Astronaut Health Human travel to Mars and beyond is no longer science fiction. Through shuttle research we know how the body changes, what we and Performance need to do to fix some of the problems or—better yet—prevent them, the importance of monitoring health, and how to determine the Introduction human body’s performance through the various sequences of launch, Helen Lane spaceflight, and landing. Basically, we understand how astronauts Laurence Young keep their performance high so they can be explorers, scientists, How Humans Adapt to Spaceflight: and operators. Physiological Changes Vision, Orientation, and Balance William Paloski Astronauts change physically during spaceflight, from their brain, Sleep heart, blood vessels, eyes, and ears and on down to their cells. Laura Barger Many types of research studies validated these changes and Charles Czeisler demonstrated how best to prevent health problems and care for the Muscle and Exercise John Charles astronauts before, during, and after spaceflight. Steven Platts Daniel Feeback During a shuttle flight, astronauts experienced a multitude of Kenneth Baldwin gravitational forces. Earth is 1 gravitational force (1 g); however, Judith Hayes during launch, the forces varied from 1 to 3 g. During a shuttl e’s Cardiovascular John Charles return to Earth, the forces varied from nearly zero to 1. 6g, over Steven Platts approximately 33 minutes, during the maneuvers to return. In all, Nutritional Needs in Space the shuttle provided rather low gravitational forces compared with Helen Lane other rocket-type launches and landings. Clarence Alfrey Scott Smith The most pervasive physiological human factor in all spaceflight, Immunology and Infectious Diseases Brian Crucian however, is microgravity. An astronaut perceives weightlessness and Satish Mehta floats along with any object, large or small. The microgravity Mark Ott physiological changes affect the human body, the functions within the Duane Pierson Clarence Sams space vehicle, and all the fluids, foods, water, and contaminants. Habitability and Environmental Health We learned how to perform well in this environment through the Habitability Janis Connolly Space Shuttle Program. This information led to improvements in David Fitts astronaut s’ health care not only during shuttle flights but also for the Dane Russo International Space Station (ISS) and future missions beyond Vickie Kloeris Environmental Health low-Earth orbit. Shuttle research and medical care led directly to John James improved countermeasures used by ISS crew members. No shuttle Thomas Limero mission was terminated due to health concerns. Mark Ott Chau Pham Duane Pierson Astronaut Health Care Philip Stepaniak

370 Major Scientific Discoveries How Humans Adapt Laurence Young, ScD to Spaceflight: Principal investigator or coinvestigator on seven space Physiological Changes missions, starting with STS-9 (1983). Alternate payload specialist on Vision, Orientation, and Balance STS-58 (1993). Change in Microgravity Founding director of the National Space Biomedical Research Institute. Gravity is critical to our existence. Apollo Program professor of As Earthlings, we have come to rely on astronautics and professor of health sciences and technology at Earth’s gravity as a fundamental Massachusetts Institute of Technology. reference that tells us which way is down. Our very survival depends on “The Space Shuttle Program provided a golden era for life sciences research. our ability to discern down so that we The difference between science capabilities on spacecraft before and after the can walk, run, jump, and otherwise Space Shuttle is enormous: it was like doing science in a telephone booth in the move about without falling. To accomplish this, we evolved specialized Gemini-Apollo era while shuttle could accommodate a school-bus-size laboratory. motion-sensing receptors in our inner This significantly added to the kind of research that could be done in space. ears—receptors that act like biological We had enormous success in life sciences, especially with the Spacelabs, for guidance systems. Among other things, quality of instrumentation, their size, and opportunity for repeated measurements these receptors sense how well our on the astronauts on different days of flight and over many different flights heads are aligned with gravity. Our including Space Life Sciences flights 1 and 2 and ending with Neurolab. brains combine these data with visual information from our eyes, pressure “Our research led to a much more complete understanding of the neurovestibular information from the soles of our feet changes in spaceflight and allowed us to know what issues require (and the seats of our pants), and countermeasures or treatment, such as space motion sickness, as well as what position and loading information from research needed to continue in Earth laboratories, such as the role of short radius our joints and muscles to continuously centrifuges for intermittent artificial gravity to support a Mars exploration mission.” track the orientation of our bodies relative to gravity. Knowing this, our brains can work out the best strategies for adjusting our muscles to move our One thing we learned during the shuttle physical activities, such as running, limbs and bodies about without losing era, though, is that astronauts’ nervous jumping, climbing ladders, driving our balance. And, we don’t even have systems adapt very quickly. By the automobiles, and flying planes. to think about it. third day of flight, most crew members The Space Shuttle––particularly At the end of launch phase, astronauts overcame the loss of gravitational when carrying one of its Spacelab find themselves suddenly thrust into stimulation. Beyond that, most or Spacehab modules and during the microgravity environment. Gravity, exhibited few functionally significant the human-health-focused, the fundamental up/down reference side effects. The downside to this rapid extended-duration Orbiter medical these astronauts relied on throughout adaptation was that, by the time a missions (1 989 through 1995)–– their lives for orientation and shuttle mission ended and the provided unique capabilities to study movement, suddenly disappears. astronauts returned to Earth, they had neurological adaptation to space. As you might expect, there are a forgotten how to use gravity for By taking advantage of the shuttle’s number of immediate consequences. orientation and movement. So, for the ability to remove and then reintroduce Disorientation, perceptual illusions, first few days after return, they suffered the fundamental spatial orientation motion sickness, poor eye-head/eye- again from a multitude of side effects reference provided by gravity, many hand coordination, and whole-body similar to those experienced at the researchers sought to understand movements are issues each astronaut beginning of spaceflight. During the the brain mechanisms responsible for has to deal with to some degree. Earth-readaptation period, these tracking and responding to this postflight affects limited some types of

Major Scientific Discoveries 371 stimulus. Other researchers used these disorientation, and motion sickness such as car sickness, sea sickness, air stimuli to investigate fundamental and symptoms. Over time, however, the sickness, or sickness caused by carnival functional aspects of neural adaptation, brain would learn not to anticipate this rides. To complicate our understanding while others focused on the operational inner-ear information during head tilts of the mechanisms of space motion impacts of these adaptive responses and the symptoms would abate. sickness further, landing-day motion with an eye toward reducing risks to sickness was not even predicted by the space travelers and enabling future How Often Do Astronauts Have incidence or severity of early in-flight missions of longer duration. Space Motion Sickness? motion sickness. The only predictable aspect was that repeat flyers usually had Many astronauts report motion sickness Space Motion Sickness fewer and less severe symptoms with symptoms just after arrival in space and each subsequent flight. What Is Space Motion Sickness? again just after return to Earth. For example, of the 400 crew members who Many people experience motion How Do Astronauts Deal With flew on the shuttle between 1981 and sickness while riding in vehicles ranging Space Motion Sickness? 1998, 309 reported at least some motion from automobiles to airplanes to boats sickness symptoms, such as stomach Crew members can limit head to carnival rides. Its symptoms include awareness, headache, drowsiness, movements during the first few days of headache, pallor, fatigue, nausea, and pallor, sweating, dizziness, and, of microgravity and during return to Earth vomiting. What causes motion sickness course, nausea and vomiting. For most to minimize the symptoms of space is unknown, but it is clearly related to astronauts, this was a short-term motion sickness. For some astronauts, the nervous system and almost always problem triggered by the loss of gravity drugs are used to reduce the symptoms. involves the specialized motion-sensing stimuli during ascent to orbit and, again, Promethazine-containing drugs receptors of the inner ear, known as the by the return of gravity stimuli during emerged as the best choice during the vestibular system. descent back to Earth. It usually lasted early 1990s, and were frequently used The most popular explanation for only through the few days coinciding throughout the remaining shuttle motion sickness is the sensory-conflict with neural adaptations to these gravity flights. Scientists also investigated theory. This theory follows from transitions. While the symptoms of preflight adaptation training in devices observations that in addition to planning space motion sickness were quite that simulate some aspects of the the best strategies for movement control, similar to other types of motion sensory conflicts during spaceflight, but the brain also anticipates and tracks the sickness, its incidence was not predicted more work is necessary before outcome of the movement commands by susceptibility to terrestrial forms, astronauts can use this approach. it issues to the muscles. When the tracked outcome is consistent with the anticipated outcome, everything proceeds normally; however, when the tracked outcome is inconsistent, the brain must take action to investigate what has gone wrong. Sensory conflict occurs when some of the sensory information is consistent with the brain’s anticipated outcome and some information is inconsistent. This might occur in space, for example, when the brain commands the neck muscles to tilt the head. The visual and neck joint receptors would provide immediate feedback indicating that the head has tilted, but because gravity has been reduced, some of the anticipated signals from the inner ear would not arrive. Some crew members experience height vertigo or acrophobia during extravehicular activities. Initially, this would cause confusion, Astronaut Stephen Robinson is anchored by a foot restraint on the International Space Station Robotic Arm during STS-114 (2005).

372 Major Scientific Discoveries After flight, crew members also experience unusual sensations. For Dafydd (Dave) Williams, MD example, to many crew members Canadian astronaut on STS-90 (1998) everyday objects (e.g., apples, and STS-118 (2007). cameras) feel surprisingly heavy. Also, when walking up stairs, many “Humans adapt remarkably well to experience the sensation that they are the physiologic challenges associated pushing the stairs down rather than with leaving the Earth’s gravitational pushing their bodies up. Some feel environment. For me, these started at an overwhelming sense of translation (sliding to the side) when rounding main engine cutoff. After 7 minutes of the 8½-minute ride, G forces pushed corners in a vehicle. Many also me like an elephant sitting on my chest. The crushing pressure resolved as have difficulty turning corners while I was thrown forward against my harness when the main engines shut down. walking, and some experience This created a sense of tumbling, head over heels, identical to performing difficulty while bending over to somersaults as a child. I pulled myself down in the shuttle seat to re-create the pick up objects. Early after return to gravitational sense of sitting in a chair and the tumbling stopped. I had Earth, most are unable to land from a jump; many report a sensation experienced my first illusion of spaceflight! that the ground is coming up rapidly “On the first day, many changes took place. My face felt puffy. I had a mild to meet them. For the most part, headache. Over the first few days, I experienced mild low back pain. Floating all of these sensations abate within freely inside the shuttle with fingertip forces gently propelling us on a a few days; however, there have been some reports of “flashbacks” somewhat graceful path reminded me of swimming underwater—with the occurring, sometimes even weeks notable absence of any resistance. after a shuttle mission. “During re-entry into the Earth’s atmosphere, I felt the forces of gravity gradually Eye-Hand Coordination: building. Standing on the middeck after landing, I felt gravitationally challenged. Changes in Visual Acuity and As I walked onto the crew transfer vehicle I felt as though my arms weighed Manual Control twice what they normally do. Moving my head created an instant sense of vertigo. Manual control of vehicles and other “On my second spaceflight, when I arrived in space it seemed like I had never left complex systems depends on accurate and as I floated gracefully, looking back at Earth, it reminded me that I will always eye-hand coordination, accurate remain a spacefarer at heart.” perception of spatial orientation, and the ability to anticipate the dynamic response of the vehicle or system to manual inputs. This function was Spatial Disorientation: Almost all have difficulty figuring out extremely important during shuttle Which Way Is Down? how much push-off force is necessary flights for operating the Shuttle Robotic to move about in the vehicle. While Astronauts entering the microgravity Arm, which required high-level spacewalking (i.e., performing environment of orbital spaceflight for coordination through direct visual, extravehicular activities [EVAs]), many the first time report many unusual camera views, and control feedback. astronauts report height vertigo—a sensations. Some experience a sense of It was also of critical importance to sense of dizziness or spinning—that sustained tumbling or inversion (that is, piloting the vehicle during rendezvous, is often experienced by individuals on a feeling of being upside down). Others docking, re-entry, and landing. Earth when looking down from great have difficulty accepting down as being heights. Some astronauts also Clear vision begins with static visual the direction one’s feet are pointing, experienced transient acrophobia—an acuity (that is, how well one can see preferring instead to consider down in overwhelming fear of falling toward an image when both the person and the terms of the module’s orientation Earth—which can be terrifying. image are stationary). In most of our during preflight training on the ground. daily activities, however, either we are

Major Scientific Discoveries 373 Since part of this function depends on how the inner ear senses gravity, Eye-Hand Coordination scientists were interested in how it changes in space. Many experiments Catching a ball is easy for most performed during and just after shuttle people on Earth. Yet, we don’t missions examined the effects of usually realize how much work spaceflight on visual acuity. Static visual acuity changed mildly, mainly our brains do to predict when because the headward fluid shifts and where the ball will come during flight cause the shape of the down, get our hand to that eyes to change. Dynamic visual acuity, exact place at the right time, on the other hand, was substantially and be sure our fingers grab disrupted early in flight and just after the ball when it arrives. return to Earth. Even for simple dynamic vision tasks, such as pursuing Because of the downward a moving target without moving the acceleration caused by gravity, head, eye movements were degraded. the speed of a falling object But the disruption was found to be increases on Earth. Scientists greatest when the head was moving, think that the brain must especially in the pitch plane (the plane anticipate this to be able to your head moves in when you nod it to indicate “yes”). Scientists found that catch a ball. Objects don’t fall in whether pursuing a target, switching space, however. So, scientists vision to a new target of interest (the wondered how well people source of a sudden noise, for instance), could catch objects without or tracking a stationary target while Payload specialist James Pawelczyk, STS-90 (1998). gravity. To find out, astronauts moving (either voluntarily or as a result were asked to catch balls launched from a spring-loaded canon that “dropped” them of vehicle motion), eye movement control was inaccurate whenever the at a constant speed rather than a constant acceleration as on Earth. In flight, the head was moving. astronauts always caught the balls, but their timing was a little bit off. They reacted as if they expected the balls to move faster than they did, suggesting that their brains Vision (eye movements) and orientation perceptions are disrupted were still anticipating the effects of gravity. The astronauts eventually adapted, but during spaceflight. Scientists found some of the effects were still evident after 15 days in space. After flight, the that some kinds of anticipatory actions astronauts were initially surprised by how fast the balls fell, but they readapted very are inaccurate during flight. The quickly. This work showed that, over time in microgravity, astronauts could make impact of these changes on shuttle changes in their eye-hand coordination, but that it took time after a gravity transition operations was difficult to assess. For for the brain to accurately anticipate mechanical actions in the new environment. example, while it appears that some shuttle landings were not as accurate as preflight landings in the Shuttle Training Aircraft, many confounding moving or the object we wish to see systems that use information from the factors (such as crosswinds and is moving. Under these dynamic visual vestibular sensors of the inner ear to engineering anomalies) precluded conditions, even people with 20/20 automatically generate eye movements rigorous scientific evaluation. It vision will see poorly if they can’t keep that are equal and opposite to any appears that the highly repetitive the image of interest stabilized on head movements. On Earth, this training crew members received just their retinas. To do this while walking, maintains a stable image on the retina before a shuttle mission might have running, turning, or bending over, we whenever the head is moving. helped offset some of the physiological have evolved complex neural control changes during the flight. Whether the

374 Major Scientific Discoveries positive effects of this training will landing day, most crew members had Scientists performed many experiments persist through longer-duration flights a wide-based gait, had trouble turning before and after shuttle missions to is unknown. At this point, training is corners, and could not land from a understand the characteristics of these the only physiological countermeasure jump. They didn’t like bending over transient postflight balance and gait to offset these potential problems. or turning their heads independent disorders. By using creative of their torsos. Recovery usually took experimental approaches, they showed Postflight Balance and Walking about 3 days; but the more time the that the changes in balance control crew member spent in microgravity, were due to changes in the way the When sailors return to port following a the longer it took for his or her balance brain uses inner-ear information long sea voyage, it takes them some and coordination to return to normal. during spaceflight. As a result, the time to get back their “land legs.” When Previous experience helped, though; crew members relied more on visual astronauts returned to Earth following a for most astronauts, each subsequent information and body sense information shuttle mission, it took them some time shuttle flight resulted in fewer postflight from their ankle joints and the bottoms to get back their “ground legs.” On effects and a quicker recovery. of their feet just after flight. Indeed, when faced with a dark environment (simulated by closing their eyes), the Balance: Eye, Ear, and Brain Working in Concert crew members easily lost their balance on an unstable surface (like beach sand, deep grass, or a slippery shower Trochlear Oculomotor (Cranial Nerve IV) floor), particularly if they made any (Cranial Nerve III) Nucleus Nucleus head movements. As a result, crew Extrinsic eye muscles receive Locus Coeruleus members were restricted from certain signals from the brain stem. Abducens (Cranial activities for a few days after shuttle Nerve VI) flights to help them avoid injuring Nucleus Vestibular themselves. These activities included (Cranial the return to flying aircraft. Nerve VIII) Nuclei In summary, experiments aboard the Space Shuttle taught us many Cerebellar Pons things about how the nervous system Cortex Medulla Nucleus of the uses gravity, how quickly the nervous Inferior Olive Solitary Tract system can respond to changes in

Somatic Motor Re exes gravity levels, and what consequences flight-related gravity changes might Vestibule of the inner ear have on the abilities of crew members sends signals to the brain stem. to perform operational activities. We know much more now than we did when the Space Shuttle Program Adapted from an illustration by William Scavone, Kestrel Illustration. started. But, we still have a lot to learn For us to see clearly, the image of interest must be focused precisely on a small region of the about the impacts of long-duration retina called the fovea. This is particularly challenging when our heads are moving (think about microgravity exposures, the effects how hard it is to make a clear photograph if your camera is in motion). Fortunately, our nervous of partial gravity environments, such systems have evolved very effective control loops to stabilize the visual scene in these as the moon and Mars, and how to instances. Using information sensed by the vestibular systems located in our inner ears, our develop effective physiological brains quickly detect head motion and send signals to the eye muscles that cause compensatory eye movements. Since the vestibular system senses gravity as well as head motion, countermeasures to help offset some investigators performed many experiments aboard the shuttle to determine the role of gravity in of the undesirable consequences the control of eye movements essential for balance. They learned that the eye movements used of spaceflight on the nervous system. to compensate for certain head motions were improperly calibrated early in flight, but they These will need to be tackled for eventually adapted to the new environment. Of course, after return to Earth, this process had to space exploration. be reversed through a readaptation process.

Major Scientific Discoveries 375 Sleep Quality and Quantity on Environmental Factors important for mental restoration), diminishing subsequent alertness, Space Shuttle Missions Several factors negatively affect cognition, and performance. A sleep: unusual light-dark cycles, noise, Many people have trouble sleeping comfortable ambient temperature and unfavorable temperatures. All of when they are away from home or in is also important for promoting these factors were present during unusual environments. This is also true sleep. On the daily questionnaire, shuttle flights and made sleep difficult of astronauts. When on a shuttle approximately 15% of the disturbances for crew members. Additionally, some mission, however, astronauts had to were attributed to the environment crew members reported that work stress perform complicated tasks requiring being too hot and approximately 15% further diminished sleep. optimal physical and cognitive abilities of the disturbances were attributed under sometimes stressful conditions. When astronauts completed a daily to it being too cold. Thus, the shuttle Astronauts have had difficulty questionnaire about their sleep, almost environment was not optimal for sleep. sleeping from the beginning of human 60% of the questionnaires indicated spaceflight. Nearly all Apollo crews that sleep was disturbed during the Circadian Rhythms previous night. Noise was listed as reported being tired on launch day and Appropriately timed circadian rhythms the reason for the sleep disturbance many gave accounts of sleep disruption are important for sleep, alertness, approximately 20% of the time. High throughout the missions, including performance, and general good health. levels of noise negatively affect both some reporting continuous sleep Light is the most important time cue to slow-wave (i.e., deep sleep important periods lasting no more than 3 hours. the body’s circadian clock, which has a for physical restoration) and REM Obtaining adequate sleep was also a natural period of about 24.2 hours. (Rapid Eye Movement) sleep (i.e., serious challenge for many crew Normally, individuals sleep when it is stage at which most dreams occur and members aboard shuttle missions. dark and are awake when it is light.

Comp arison of Earth and Space Sleep Cycles Sleep W

( Wake (8Sleep hours) (16 Wake hours) Eart h Condit i ons (16 hours) (8 hours) (16 hours) On a 24-hou r ex ternal li ght- dark cycl e , the body’s circa d ian clock r re mai ns prop e rly synchro n ize d r (e.g., hor mon es like melatonin are 4 released at the Melatonin

appropriate time). 40 hours 24 hours Space Conditions On the Orbiter’s 90-minu te light-dark

cycle, weak interior Wake Sleep Wake

ambient light may not

sufficiently cue the Wake Sleep Wake

body’s circadian clock,

wh ich may then b ecom e de synch roniz e d (e.g ., inapprop r iately ti m ed ho rmone relea se). Melatonin Melatonin

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376 Major Scientific Discoveries This 24-hour pattern resets the body’s crew members had to shift their study on STS-90 and STS-95 clock each day and keeps all of the sleep-wake schedule, sometimes up missions using full polysomnography, body’s functions synchronized, to 12 hours. This physiological which monitors brain waves, tension maximizing alertness during the day challenge, associated with sleep in face muscles, and eye movements, and consolidating sleep at night. Unlike disruption, created “fatigue pre-load” and is the “gold standard” for the 24-hour light-dark cycle that we before the mission even began. evaluating sleep. Scientists also experience on Earth, shuttle crew made simultaneous recordings of All US crew members participated in members experience 90-minute light- multiple circadian variables such as the Crew Health Stabilization Program dark cycles as they orbited the Earth. body temperature and cortisol, a where they were housed together for salivary marker of circadian rhythms. Not only is the timing of light 7 days prior to launch to separate This extensive study included unsuitable, but the low intensity of the them from potential infectious disease performance assessments and the light aboard the shuttle may have from people and food. During this first placebo-controlled, double-blind contributed to circadian misalignment. quarantine period, scientists at clinical trial of a pharmaceutical Light levels were measured in the Harvard Medical School, in association (melatonin) during spaceflight. Crew various compartments of the shuttle with NASA, implemented a members on these flights experienced during Space Transportation System bright-light treatment program for crew circadian rhythm disturbances, (STS)-90 Neurolab (1 998) and STS-95 members of STS-35 (1 990), the first sleep loss, and decrements in (1 998) missions. In the Spacelab, light Space Shuttle mission requiring both neurobehavioral performance. levels were constant and low dual shifts and a night launch. (approximately 10 to 100 lux) during the Scheduled exposure to bright light For another experiment, crew members working day. In the middeck, where the (about 10,000 lux—approximately the wore a watch-like device, called an crew worked, ate, and slept, the light brightness at sunrise), at appropriate actigraph, on their wrists to monitor levels recorded were relatively constant times throughout the prelaunch sleep. The actigraph contained an and very dim (1 to 10 lux). Laboratory period at Johnson Space Center and accelerometer that measured wrist data showed that these light levels are Kennedy Space Center, was used motion. From that recorded motion insufficient to entrain the human to prepare shuttle crew members of scientists were able to use software circadian pacemaker to non-24-hour the Red Team of STS-35 for both their algorithms to estimate sleep duration. sleep-wake schedules. Normal room night launch and their subsequent Fifty-six astronauts (approximately lighting (200 to 300 lux) would be night-duty shift schedule in space. 60% of the Astronaut Corps between required to keep the circadian system A study confirmed that the prescribed 20 01 and 2 01 0) participated in this aligned under 24-hour light-dark cycles. light exposure during the prelaunch study. Average nightly sleep duration quarantine period successfully induced across multiple shuttle missions was Crew members also were often circadian realignment in this crew. approximately 6 hours. This level scheduled to work on 23.5-hour days or Bright lights were installed at both of sleep disruption has been associated had to shift their sleep-wake schedule centers’ crew quarters in 1991 for use with cognitive performance deficits several hours during flight. Moreover, when shuttle flights required greater in numerous ground-based laboratory deviations from the official schedule than a 3-hour shift in the prelaunch and field studies. were frequently required by operational sleep-wake cycle. demands typical of space exploration. Pharmaceuticals were the most Therefore, the crew members’ circadian Studies of Sleep in Space widespread countermeasure for sleep rhythms often became misaligned, disruption during shuttle flights. Indeed, resulting in them having to sleep during NASA studied sleep quality and more than three-quarters of astronauts a time when their circadian clock was quantity and investigated the reported taking sleep medications promoting alertness, much as a shift underlying physiological mechanisms during missions. Astronauts took sleep worker on Earth. associated with sleep loss as well as medications during flight half the time . countermeasures to improve sleep Wake-promoting therapeutics gained in Actually, difficulties with sleep began and ultimately enhance alertness and popularity as well, improving alertness even before the shuttle launched. performance in space. Scientists after sleep-disrupted nights. Often in the week prior to launch conducted a comprehensive sleep

Major Scientific Discoveries 377 Space Station (ISS) where frequent shifts in the scheduled sleep-wake Richard Searfoss times disrupt sleep and circadian Colonel, US Air Force (retired). alignment. Sleep most certainly will Pilot for STS-58 (1993) and also be an issue when space travel STS-76 (1996). continues beyond low-Earth orbit. Commander for STS-90 (1998). Private sleep quarters will probably not be available due to space and mass Perspectives on issues. Consequently, ground-based Neurolab studies continue to search for the most effective, least invasive, and least “I was privileged to time-consuming countermeasures to command STS-90 improve sleep and enhance alertness Neurolab, focusing on the effects of weightlessness on the brain and nervous during spaceflight. Currently, scientists system. Although my technical background is in engineering and flight test, it was are trying to pinpoint the most effective still incredibly rewarding to join a dedicated team that included not just NASA but wavelength of light to use to ensure the National Institutes of Health and top researchers in the world to strive with alignment of the circadian system and improve alertness during critical tasks. disciplined scientific rigor to really understand some of the profound changes to living organisms that take place in the unique microgravity environment. I viewed my primary role as science enabler, calling on my operational experience to build Spaceflight Changes Muscle the team, lead the crew, and partner with the science community to accomplish the Within the microgravity environment real ‘mission that mattered.’ of space, astronauts’ muscles are said to be “unweighted” or “unloaded” “Even though at the time STS-90 flew on Columbia humans had been flying to because their muscles are not required space nearly 40 years, much of our understanding of the physiological effects was to support their body weight. The still a mystery. Neurolab was extremely productive in unveiling many of those unloading of skeletal muscle during mysteries. The compilation of peer-reviewed scientific papers from this mission spaceflight, in what is known as “muscle atrophy,” results in remodeling produced a 300-page book, the only such product from any Space Shuttle mission. of muscle (atrophic response) as an I’ll leave it to the scientists to testify to the import, fundamental scientific value, and adaptation to the spaceflight. These potential for Earth-based applications from Neurolab. It’s enough for me to realize decrements, however, increase the that my crew played an important role in advancing science in a unique way. risk of astronauts being unable to adequately perform physically “With STS-90 as the last of 25 Spacelab missions, NASA reached a pinnacle of demanding tasks during EVAs or after overall capability to meld complex, leading-edge science investigations with abrupt transitions to environments the inherent challenges of operating in space. Building on previous Spacelab of increased gravity (such as return to flights, Neurolab finished up the Spacelab program spectacularly, with scientific Earth at the end of a mission). results second to none. What a joy to be part of that effort! It was unquestionably A similar condition, termed “disuse the honor of my professional life to be a member of the Neurolab team in my muscle atrophy,” occurs any time role as commander.” muscles are immobilized or not used as the result of a variety of medical conditions, such as wearing a cast or being on bed rest for a long time. Space Although sleep-promoting medication acceptable, feasible, and effective muscle research may provide a better use was widespread in shuttle methods to promote sleep in future understanding of the mechanisms crew members, investigations need missions. Sleep monitoring is ongoing underlying disuse muscle atrophy, to continue to determine the most in crew members on the International which may enable better management

378 Major Scientific Discoveries of these patients. In the US human flight. The volumes of various leg exercises may prevent loss of muscle space program, the only tested in-flight muscles were reduced by about 4% function leading to implementation of preventive treatment for muscle atrophy to 6% after spaceflight. In another routine combined aerobic and resistive has been physical exercise. In-flight study of longer missions (9 to 16 days’ exercise for ISS astronauts. exercise hardware and protocols varied duration—two males and one female, from mission to mission, somewhat mean age 41 years), the losses were Muscle Fiber Changes in Size and Shape dependent on mission duration as well reported to be greater, ranging from An “average” healthy person has as on the internal volume of the 5.5% to 15.9% for specific leg roughly equal numbers of the two spacecraft. Collective knowledge gained muscles. This study found that daily major muscle fiber types (“slow” and from these shuttle missions aided in the volume losses of leg muscles “fast” fibers). Slow fibers contract evolution of exercise hardware and normalized for duration of flight were (shorten) slowly and have high protocols to prevent spaceflight-induced from 0.6% to 1.04% per mission day. endurance (resistance to fatigue) levels. muscle atrophy and the concomitant Fast fibers contract quickly and fatigue deficits in skeletal muscle function. Muscle Strength Decreases readily. Individual variation in muscle How Was Muscle Atrophy Measured, Decreases in muscle strength persisted fiber type composition is genetically and What Were the Results? throughout the shuttle period in spite (inherited) determined. The of various exercise prescriptions. compositional range of slow fibers in Leg and Back Muscle Size Decreases Measurements of muscle strength, the muscles on the front of the thigh mass, and performance helped (quadriceps muscles) in humans can Loss of muscle and strength in the lower NASA determine the degree of vary between 20% and 95%, a extremities of astronauts was initially muscle function loss and assess the percentage found in many marathon found in the Gemini (1 962 -1 966) and efficacy of exercise equipment and runners. On the other hand, a Apollo missions (1 967 -1 972) and was determine whether exercise protocols world-class sprinter or weight lifter further documented in the first US space were working as predicted. would have higher proportions of fast station missions (Skylab, 1973 -1 974) fibers and, through his or her training, Muscle strength, measured with a of 28, 59, and 84 days’ duration. these fibers would be quite large dynamometry (an instrument that NASA calculated crude muscle volumes (higher cross-sectional diameter or measures muscle-generated forces, by measuring the circumference of the area). Changing the relative proportions movement velocity, and work) before lower and upper legs and arms at of the fiber types in muscles is possible, launch and after landing consistently multiple sites. but it requires powerful stimulus showed loss of strength in muscles that such as a stringent exercise program For shuttle astronauts, more extend the knee (quadriceps muscles) or the chronic unloading profile that sophisticated, accurate, and precise by up to 12% and losses in trunk occurs in microgravity. NASA was measures of muscle volume were made flexor strength of as much as 23%. interested in determining whether there by magnetic resonance imaging (MRI). The majority of strength and endurance were any changes in the sizes or MRI is a common diagnostic medical losses occurred in the trunk and leg proportions of fiber types in astronauts procedure used to image patient’s muscles (the muscle groups that are during spaceflight. internal organs that was adapted to active in normal maintenance of posture provide volume measurements of a and for walking and running) with In the only biopsy study of US crew member’s lower leg, thigh, and little loss noted in upper body and arm astronauts to date, needle muscle back muscles before and after flight. muscle strength measurements. In biopsies from the middle of the vastus The leg muscle volume was evaluated contrast, four STS-78 (1 996) astronauts lateralis muscle (a muscle on the side in eight astronauts (seven males and had almost no decrease in calf muscle of the thigh) of eight shuttle crew one female, age range 31 to 39 years) strength when they participated members were obtained before launch who flew on either one of two 9-day voluntarily in high-volume exercise (3 to 16 weeks) and after landing missions. Scientists obtained MRI in combination with the in-flight, (within 3 hours) for missions ranging scans of multiple leg cross sections experiment-specific muscle strength in duration from 5 to 11 days. Three of prior to flight and compared them performance measurements. This the eight crew members (five males and to scans obtained at 2 to 7 days after preliminary research suggested that such three females, age range 33 to 4 7 years)

Major Scientific Discoveries 379 flew 5-day missions while the other maneuver around, the lack of gravity astronauts, even as missions grew in five crew members completed 11 -day can decondition the human body. length. Armed with information from flights. Five of the eight crew members Skylab, NASA decided to provide Knowledge gained during the early did not participate in other medical exercise on future shuttle missions to years of human spaceflight indicated an studies that might affect muscle fiber minimize consequences that might adaptation to the new environment. size and type. NASA made a variety of be associated with spaceflight While the empirical evidence was measurements in the biopsy samples, deconditioning to guarantee in-flight limited, the biomedical data indicated including relative proportions of the astronaut performance and optimize that microgravity alters the two major muscle fiber types, muscle postflight recovery. musculoskeletal, cardiovascular, and fiber cross-sectional area by muscle neurosensory systems. In addition, the fiber type, and muscle capillary (small Benefits of Exercise responses to spaceflight varied from blood vessel) density. Slow fiber-type person to person. Space adaptation was Space Shuttle experience demonstrated cross-sectional area decreased by highly individualized, and some human that for the short-duration shuttle 15% as compared to a 22% decrease systems adjusted at different rates. flights, the cardiovascular adaptations for fast fiber muscle fibers. Biopsy Overall, these changes were considered did not cause widespread significant samples from astronauts who flew on to have potential implications on problems except for the feelings of the 11 -day mission showed there were astronaut occupational performance as light-headedness—and possibly relatively more fast fiber types and well as possible impacts to crew health fainting—in about one-fifth of the fewer slow fiber types, and the density and safety. There was concern that astronauts and a heightened concern of muscle capillaries was reduced space-related deconditioning could over irregular heartbeats during when the samples taken after landing negatively influence critical space spacewalks. During the Space Shuttle were compared to those taken before mission tasks, such as construction of Program, however, it became clear launch. NASA research suggests that the space station, repair of the orbiting from these short-duration missions that fiber types can change in microgravity Hubble Space Telescope, piloting and exercise countermeasures would be due to the reduced loads. This has landing operations, and the ability to required to keep astronauts fit during implications for the type and volume egress in an emergency. long-duration spaceflights. Although of prescriptive on-orbit exercise. exercise was difficult in the shuttle, Historically, NASA worked on Research conducted during the shuttle simple exercise devices were the programs to develop a variety of flights provided valuable insight into stationary bike, a rowing machine, and strategies to prevent space how astronauts’ muscles responded a treadmill. Astronauts, like those from deconditioning, thus migrating toward to the unloading experienced while Skylab, found it difficult to raise their the use of exercise during spaceflight living and working in space. Exercise heart rate high enough for adequate to assure crew member health and equipment and specific exercise exercise. NASA demonstrated that fitness. In general, exercise offered therapies developed and improved on in-flight exercise could be performed a well-understood approach to fitness during the program are currently in and helped maintain some aerobic on Earth, had few side effects, and use on the ISS to promote the safety fitness, but much research remained to provided a holistic approach for and health of NASA crew members. be done. This finding led to providing addressing health and well-being, both the ISS with a bicycle ergometer, a physically and psychologically. treadmill, and a resistive exercise The “Why” and “How” of NASA scientists conducted experiments device to ensure astronaut fitness. Exercise on the Space Shuttle in the 1970s to characterize the effects Deconditioning due to a lack of of exercise during missions lasting 28, Why Exercise in Space? aerobic exercise is a concern in the 56, and 84 days on America’s first area of EVAs, as it could keep the Just as exercise is an important orbiting space station—Skylab. This astronaut from performing spacewalks component to maintain health here on was the first opportunity for NASA to and other strenuous activities. Without Earth, exercise plays an important role study the use of exercise in space. These enough in-flight aerobic exercise, in maintaining astronaut health and early observations demonstrated that astronauts experienced elevated heart fitness while in space. While living in exercise modalities and intensity could rates and systolic blood pressures. space requires very little effort to improve the fitness outcomes of

380 Major Scientific Discoveries How Astronauts Exercised on the Space Shuttle Ken Baldwin, PhD Because of the myriad restrictions Principal investigator on three Spacelab missions—STS-40 about what can be launched within a (1991), STS-58 (1993), and STS-90 space vehicle, tremendous challenges (1998)—and a Physiological exist related to space exercise Anatomical Rodent Experiment. equipment. Systems need to be portable Muscle Team leader, 2001-2009, and lightweight, use minimal electrical for the National Space Biomedical Research Institute. power, and take up limited space during use and stowage. In addition, “The space life sciences missions (STS-40, STS-58, and STS-90) provided a operation of exercise equipment in state-of-the-art laboratory away from home that enabled scientists to customize microgravity is inherently different than it is on Earth. Refining the their research studies in ways that were unheard of prior to the Space Shuttle human-to-machine interfaces for Program. In using such a laboratory, my research generated unique insights exercise in space was a challenging task concerning the remodeling of muscle structure and function to smaller, weaker, tested throughout the shuttle missions. fatigue-prone muscles with a contractile phenotype that was poorly suitable to Providing exercise concepts with the apposing gravity. These unique findings became the cornerstone of appropriate physical training stimulus recommendations that I spearheaded to redesign the priority of exercise during to maintain astronaut performance that operates effectively in microgravity spaceflight from one of an aerobic exercise focus (treadmill and cycling exercise) to proved to be a complex issue. a greater priority of exercise paradigms favoring heavy-resistance exercise in order to prevent muscle atrophy in microgravity. Additionally, our group also made an Exercise systems developed for shuttle included: treadmill, cycle ergometer, important discovery in ground-based research supported by NASA’s National Space and rower. The devices offered exercise Biomedical Research Institute showing that it is not necessarily the contraction conditioning that simulated ambulation, mode that the muscles must be subjected to, but rather it is the amount and volume cycling, and rowing activities. All of mechanical force that the muscle must generate within a given contraction exercise systems were designed for mode in order to maintain normal muscle mass. Thus, the early findings aboard the operations on the shuttle middeck; Space Shuttle have served as a monument for guiding future research to expand however, the cycle could also be used on the flight deck so that astronauts humankind’s success in living productively on other planets under harsh conditions.” could gaze out the overhead windows during their exercise sessions. Each of the three systems had its own challenges for making Earth-like The deconditioned cardiovascular or she is walking slowly. The heart exercise feasible while in space within system must work harder to do the rate and systolic blood pressure (the the limits of the shuttle vehicle. Most same or even less work (exercise) than highest blood pressure in the arteries, traditional exercise equipment has the the well-conditioned system. just after the heartbeats during each benefit of gravity during use, while cardiac cycle) increase as the astronaut Exercise capacity was measured spaceflight systems require unique walks fast or runs until the heart rate preflight on a standard upright bike. approaches to exercise for the astronaut cannot increase any more. Exercise was stepped up every users. While each system had its unique 3 minutes with an increase in In-flight exercise testing showed that issues for effective space operations, workload. Maximal exercise was crew members could perform at 70% of the exercise restraints were some of the determined preflight by each the preflight maximum exercise level biggest challenges during the program. astronaut’s maximum volume of with no significant issues. This allowed These restraints included techniques oxygen uptake. A conditioned mission planners to schedule EVAs for securing an astronaut to the exercise astronaut may have little increase and other strenuous activities that did device itself to allow for effective in heart rate above sitting when he not overtax the astronauts’ capabilities. exercise stimuli.

Major Scientific Discoveries 381 with exercise profiles that alter speed “Shuttle left a legacy, albeit incomplete, of the theory and and grade. The shuttle treadmill had practice for exercise countermeasures in space.” limits to its tread length and speed and had no means for altering grade. William Thornton, MD, astronaut, principal investigator and original inventor of the shuttle treadmill. Treadmill ambulation required the astronaut to wear a complex over-the- shoulder bungee harness system that connected to the treadmill and held the runner in place during use. Otherwise, the runner would propel off the tread with the first step. While exercise target heart rates were achieved, the treadmill length restricted gait length and the harness system proved quite uncomfortable. This information was captured as a major lesson learned for the development of future treadmill systems for use in space.

Cycle Ergometer The shuttle cycle ergometer (similar to bicycling) operated much like the equipment in a gym. It used a conventional flywheel with a braking band to control resistance via a small motor with a panel that displayed the user’s speed (up to 120 rpm) and workload (up to 350 watts). The restraint system used commercial pedal-to-shoe bindings, or toe clips, that held the user to the cycle while leaning on a back pad in a recumbent position. The cycle had no seat, however, and used a simple lap belt to stabilize the astronaut during aerobic The evolution of types of exercise: running, rowing, and cycling from Earth to space exercise. While the cycle offered great configurations. Astronaut Jerry Linenger running during STS-64 (1994), Astronaut Robert aerobic exercise, it was also used for Cabana rowing on STS-53 (1992), and Astronaut Catherine Coleman cycling on STS-73 (1995). prebreathe operations in preparation for EVAs. The prebreathe exercise protocol allowed for improved nitrogen In-flight exercise quality and quantity considerations used for generating release from the body tissues to were measured on all modalities exercise prescriptions. Research minimize the risk of tissue bubbling using a commercial heart rate monitor showed that target heart rates could be during the EVA that could result in for tracking work intensity and achieved using each of the three types decompression sickness or “the bends.” exercise duration. This allowed for a of exercise during spaceflight. Exercise accelerated, “washout” common measure across devices. Heart nitrogen that may bubble in the tissues rate is a quality indicator of exercise Treadmill during EVA, causing decompression intensity and duration (time) is a gauge Running and walking on a treadmill in sickness and, thereby, terminating the of exercise quantity––common the gym can be computer controlled EVA and risking crew health.

382 Major Scientific Discoveries Rower to generate blood pressure and a well-being of crew members while also healthy vascular system to regulate revealing the mechanisms underlying The rower offered total body aerobic the pressure and distribute the blood, the systemic adjustments to spaceflight. exercise, similar to gym rowers. It also as needed, throughout the body via NASA researchers studied the had limited capability for resistance the blood vessels. immediate responses to the effects of exercise. Similar to the cycle, it was weightlessness during Space Shuttle seatless since the body floats. The For our purposes, the human body flights and the well-developed systemic astronaut’s feet were secured with a is essentially a column of fluid; the adjustments that followed days and Velcro ® strap onto a footplate that hydrostatic forces that act on this weeks of exposure. Most allowed for positioning. The rower used column, due to our upright posture such research related to the loss of a magnetic brake to generate resistance. and bipedal locomotion, led to a orthostatic tolerance after even brief complex system of controls to flights and to the development of Summary maintain—at a minimum—adequate potentially detrimental disturbances in blood flow to the brain. In summary, exercise during Space cardiac rhythm during longer flights. Shuttle flights had physical and On Earth, with its normal gravity, Scientists also evaluated the usefulness psychological benefits for astronauts. all changes in posture—such as when of several interventions such as exercise, In general, it showed that astronauts lying down, sitting, or standing as fluid ingestion, and landing-day gravity could reduce the deconditioning effects well as changes in activity levels such suits (g-suits) in protecting the that may alter performance of critical as through exercising—require the astronauts’ capacities for piloting the mission tasks using exercise in space, heart and vascular system to regulate Orbiter—an unpowered, 100-ton even on the relatively short shuttle blood pressure and distribution by glider—safely to a pinpoint landing, missions. As a result, a “Flight Rule” adjusting the heart rate (beats per and especially for making an unaided was developed that mandated minute), amount of blood ejected by evacuation from the Orbiter if it landed astronauts exercise on missions longer the heart (or stroke volume), and at an alternate site in an emergency. than 11 days to maintain crew health, constriction or dilation of the safety, and performance. distributing arteries. These adjustments Orthostatic Intolerance: assure continued consciousness by Each device had the challenge of Feeling Light-headed and Fainting providing oxygen to the brain or providing an appropriate exercise on Standing Upright continued ability to work, with oxygen stimulus without the benefit of gravity going to the working muscles. One of the most important changes and had a unique approach for on-orbit negatively impacting flight operations operations. Engineers and exercise Removing the effects of gravity during and crew safety is landing day physiologists worked closely together to spaceflight and restoring gravity after a orthostatic intolerance. Astronauts who develop Earth-like equipment for the period of adjustment to weightlessness have orthostatic intolerance (literally, shuttle environment that kept astronauts present significant challenges to the inability to remain standing upright) healthy and strong. the cardiovascular control system. cannot maintain adequate arterial blood The cardiovascular system is stressed pressure and have decreased brain blood very differently in spaceflight, where levels when upright, and they experience Cardiovascular: Changes body fluids are shifted into the head light-headedness and perhaps even in the Heart and Blood Vessels and upper body and changes in fainting. This may impair their ability That Affect Astronaut Health posture do not require significant to stand up and egress the vehicle after and Performance responses because blood does not landing, and even to pilot the vehicle drain and pool in the lower body. The cardiovascular system, including while seated upright as apparent gravity Although the cardiovascular system the heart, lungs, veins, arteries, and increases from weightlessness to 1.6 g is profoundly affected by spaceflight, capillaries, provides the cells of the during atmospheric re-entry. the basic mechanisms involved are still body with oxygen and nutrients and not well understood. The orthostatic intolerance condition allows metabolic waste products is complicated and multifactorial. to be eliminated through the kidneys During the shuttle era, flight-related Its hallmarks are increased heart rate, (as urine) and the gastrointestinal tract. cardiovascular research focused on decreased systolic blood pressure, All of this depends on a strong heart topics that could benefit the safety and

Major Scientific Discoveries 383 after returning to Earth. Thus, it is not the plasma volume loss alone that Blood Volume Changes During Spaceflight causes light-headedness but the lack of compensatory activation of the sympathetic system. Another possible mechanism for Immediately While in post-spaceflight orthostatic hypotension After Entering Prolonged Microgravity Microgravity (low blood pressure that causes Environment fainting) is cardiac atrophy and the resulting decrease in stroke volume (the amount of blood pushed out of the heart at each contraction). Orthostatic hypotension occurs if the fall in stroke volume overwhelms normal compensatory mechanisms such as an increase in heart rate or constriction in the peripheral blood vessels in the arms, legs, and abdomen. The vast majority of astronauts have been male. Consequently, any conclusions drawn regarding the physiological responses to spaceflight are male biased. NASA recognized significant differences in how men and women respond to spaceflight, including the effects of spaceflight on cardiovascular responses to orthostatic stress. More than 80% of female crew Launch Landing Day Day members tested became light-headed during postflight standing as compared to about 20% of men tested, confirming a well-established difference in the The distribution of blood changes in microgravity more in the upper torso and less in the legs. At landing, the astronaut is light-headed because of less blood and the pooling of non-astronaut population. This is an the blood in the feet. important consideration for prevention, as treatment methods may not be equally effective for both genders. and decreased stroke volume during them developed orthostatic intolerance 5 minutes of standing shortly after during standing or head-up tilting. How Can This Risk be Changed? landing. The decrease in blood volume The group of astronauts that developed frequently observed is an important While orthostatic intolerance is orthostatic intolerance lost comparable initiating event in the etiology of perhaps the most comprehensively amounts of plasma (the watery orthostatic intolerance, but it is the studied cardiovascular effect of portion of the blood, which the body subsequent effects and the spaceflight, the mechanisms are not can adjust quickly) to the group that physiological responses (or lack well understood. Enough is known did not develop orthostatic intolerance. thereof) to those effects that may result to allow for the implementation of But, the group that was not susceptible in orthostatic intolerance after shuttle some countermeasures, yet none of had a more pronounced increase in flights. This is highlighted by the fact these countermeasures have been the functioning of the sympathetic that while all shuttle crew members completely successful at eliminating nervous system, which is important who were tested had low blood volume spaceflight-induced orthostatic in responding to orthostatic stress on landing day, only one-quarter of intolerance following spaceflight.

384 Major Scientific Discoveries In 1985, ingestion of fluid and salt (or “fluid loading”) prior to landing became a medical requirement through How Red Blood Cells Are Lost a Flight Rule given the demonstrated benefits and logic that any problem in Spaceflight caused—at least in part—by a loss in plasma volume should be resolved— What do astronauts, people at least in part—by fluid restoration. traveling from high altitudes to Starting about 2 hours before landing, sea level, and renal (kidney) astronauts ingest about 1 liter (0.58 oz) failure patients have in common? of water along with salt tablets. All experience changes in red Subsequent refinements to enhance palatability and tolerance include the blood cell numbers due to changes addition of sweeteners and substitution in the hormone erythropoietin, of bouillon solutions. Of course, any synthesized in the kidneys. data on plasma volume acquired after 1985 do not reflect the unaltered landing Red blood cells bring oxygen to tissues. When astronauts enter microgravity day deficit. But, in spite of the fluid or high-altitude residents travel to sea level, the body senses excess red blood cells. loading, astronauts still returned from High-attitude residents produce an increased number because of decreased ambient shuttle missions with plasma volume oxygen levels but, at sea level, excess cells are not needed. Astronauts experience deficits ranging from 5% to 19% as well a 15% decrease in plasma volume as the body senses an increase in red blood cells as with orthostatic intolerance. per volume of blood. In these situations, erythropoietin secretion from the kidneys Shuttle astronauts returned home ceases. Prior to our research, we knew that when erythropoietin secretion stops, the wearing a lower-body counterpressure bone marrow stops production of pre red blood cells and an increase in programmed garment called the anti-g suit. These suits have inflatable bladders at the destruction of these cells occurs. calves, thighs, and lower abdomen Another function was found in the absence of erythropoietin, the loss of the newly that resist blood pooling in those areas and force the blood toward the head. secreted blood cells from the bone marrow—a process called neocytolysis. Since The bladders can be pressurized from patients with renal failure are unable to synthesize erythropoietin, it is administered at 25 mmHg (0.5 psi) to 130 mmHg the time of renal dialysis (a process that replaces the lost kidney functions); however, (2.5 psi). In addition, ISS crew blood levels of erythropoietin fell rapidly between dialysis sessions, and neocytolysis members landing on the shuttle used occurs. Thus, the development of long-lasting erythropoietin now prevents recumbent seats (as opposed to the neocytolysis in these patients. Erythropoietin is, therefore, important for human upright seats of the shorter-duration shuttle crews) and only inflated their health—in space and on Earth—and artificial erythropoietin is essential for renal suit minimally to 25 mmHg (0.5 psi). failure patients. All astronauts deflated their anti-g suit slowly after the shuttle wheeled to a stop to allow their own cardiovascular systems time to readjust to the pooling and thus recondition the cardiovascular well-tolerated by crew members and effects of Earth’s gravity. system, showed promise in ground did not produce any differences in studies but was judged too plasma volume or orthostatic tolerance. Other treatments for orthostatic cumbersome and time consuming for Thus, the countermeasures tested were intolerance were also evaluated during routine shuttle use. A much simpler not successful in preventing postflight the program. A technique called approach used a medication known as orthostatic intolerance, at least not “lower body negative pressure,” fludrocortisone, a synthetic in an operationally compatible manner. which used slight decompression of corticosteroid known to increase fluid The knowledge gained about an airtight chamber around the retention in patients on Earth. It proved spaceflight-induced cardiovascular abdomen and legs to pool blood there unsuccessful, however, when it was not

Major Scientific Discoveries 385 changes and differences between orthostatic tolerance groups, however, provided a base for development of future pharmacological and mechanical countermeasures, which will be especially beneficial for astronauts on long-duration missions on space stations and to other planets.

Cardiovascular Changes During Spaceflight Headward fluid shift was inferred from reports containing astronaut observations of puffy faces and skinny legs, and was long believed to be the initiating event for subsequent In the Spacelab (laboratory in Orbiter payload bay) Astronaut Rhea Seddon, MD, measures cardiac cardiovascular responses to spaceflight. function on Martin Fettman during Columbia life sciences mission STS-58 (1993) . The documentation of this shift was an early goal of Space Shuttle-era demonstrated the variety of changes in the resting astronaut than before investigators, who used several in the cardiovascular system in flight. flight. The volume of blood ejected from techniques to do so. Direct measurement In-flight heart rate and systolic and the heart with each beat initially of peripheral venous blood pressure in diastolic blood pressure decreased when increases because of the headward fluid an arm vein (assumed to reflect central compared to the preflight values. During shift, but it becomes lower than preflight venous pressure in the heart, an re-entry into Earth’s atmosphere, these levels after that due to the decreased indication of headward fluid shift) was values increased past their preflight blood volume. done in 1983 during in-flight blood baseline, reaching maximal values at collections. Actual measurement of peak deceleration loading. When crew Cardiac Rhythm Disturbances central venous pressure was done on a members stood upright for the first time Contrary to popular opinion, shuttle small number of astronauts on dedicated after landing, both systolic and diastolic astronauts were not monitored space life sciences Spacelab missions pressures significantly decreased from extensively throughout their flights. starting in 1991 . These studies, and their seated values and the decrease in Electrocardiograms were recorded and particularly the direct central venous diastolic pressure was greater in crew transmitted for crew health assurance pressure measurements, demonstrated members who did not fully inflate their only on up to two crew members that central venous pressure was g-suits. Systolic pressure and heart rate (out of crews numbering up to seven) elevated in recumbent crew members returned to preflight values within an and only during launch and landing even before launch, and that it increased hour of landing, whereas all other through the 14th shuttle mission, acutely during launch with acceleration spaceflight-induced cardiovascular STS-41G (1 984). Subsequently, given loads of up to three times Earth’s changes were reversed within a week the established confidence that healthy surface gravity. This increased the after landing. Furthermore, stress astronauts could tolerate spaceflight weight of the column of blood in the hormones such as adrenaline without difficulty, the requirement for legs “above” the heart and the central (involved in the primal “fight or flight even such minimal medical monitoring venous pressure decreased to below response”) were increased postflight, was eliminated. Later, a purpose-built baseline values immediately on whether the astronauts were resting system for on-board recording of reaching orbit. Investigators realized supine or standing. that the dynamics of central blood electrocardiograms and blood pressure was used on select volunteer astronauts volume changes were more complex So, What Does This Mean? than originally hypothesized. between 1989 and 1994. During weightlessness, there is reduced At present, there is little evidence to By measuring and recording arterial postural stress on the heart. As expected, indicate that cardiovascular changes blood pressures, heart rate, and rhythm, the cardiovascular response is muted: observed in spaceflight increase two-dimensional echocardiography blood pressure and heart rate are lower

386 Major Scientific Discoveries susceptibility to life-threatening ISS and beyond. Additionally, as the of strong gravitational force, a shift of disturbances in cardiac rhythms. expression goes, while good nutrition fluid from the lower body to the upper Certain findings, however, suggest that will not make you an Olympic-quality body occurs. This begins on the launch significant cardiac electrical changes athlete, inadequate nutrition can ruin an pad, when crew members may lie on occurred during short and long flights. Olympic-quality athlete. their backs for 2 to 3 hours for many flights. Scientists hypothesize that the NASA systematically studied cardiac Nutritional needs drive the types and brain senses this extra upper-level body rhythm disturbances during some amounts of food available on orbit. water and adapts through reduced thirst shuttle missions in response to medical Since shuttle flights were short (1 to and, sometimes, increased losses through reports of abnormal rhythms in nine of 2 weeks), nutritional needs were more the kidney—urine. An initial reduction 14 spacewalking astronauts between like those required for a long camping of about 15% water (0 .5 kg [1. 15 pounds]) 1983 and 1985. In subsequent studies on trip. Accordingly, NASA’s research occurred in the plasma in flight, thus 12 astronauts on six shuttle flights, focused on the most important nutrients producing a concentrated blood that is investigators acquired 24-hour that related to the physiological corrected by reducing the levels of red continuous Holter recordings of the changes that microgravity induced for blood cells through a mechanism that electrocardiograms during and after such short missions. The nutrients reduces new blood cells. Soon after altitude chamber training, then again studied were water, energy (calories), entering space, these two compartments 30 days before launch, during and after sodium, potassium, protein, calcium, (plasma and red blood cells) return to each EVA, and after return to Earth. vitamin D, and iron. the same balance as before flight but These investigators observed no change Many astronauts eat and drink less in with about 10% to 15% less total in the number of premature contractions flight, probably due to a combination of volume in the circulation than before per hour during flight compared to reduced appetite and thirst, high stress, flight. Through unknown mechanisms, preflight or postflight. Given the fact altered food taste, and busy schedules. extracellular fluid is less and total body that these data disagreed with other Because the success of a flight is based water does not change or may decrease previous reports on astronauts, the on the primary mission, taking time for slightly, 2% to 3% (maximum loss of investigators recommended that further eating may be a low priority. Astronauts 1.8 kg [4 pounds]). From this NASA study was required. are healthy adults, so NASA generally scientists inferred that the amount of intracellular fluid is increased, Summary uses Earth-based dietary nutrient recommendations; however, researchers although this has not been measured. The Space Shuttle provided many commonly found inadequate food These major fluid shifts affect thirst opportunities to study the intake and corresponding loss of and, potentially, water requirements cardiovascular system due to the high body weight in astronauts. This as well as other physiological functions. number of flights and crew members, observation led to research designed Water turnover decreases due to a along with an emphasis on life sciences to estimate body water and energy lower amount of water consumed research. This research provided a needed during spaceflight. and decreased urine volume—both better understanding of the changes occur in many astronauts during in spaceflight and provided focus for How Much Water Should an spaceflight. Since total body water the ISS research program. Astronaut Consume? does not change much, recommended water intakes are around 2,000 ml/d Water intake is important to prevent (68 oz, or 8.5 cups). Astronauts may Nutritional Needs in Space dehydration. About 75% of our bodies consume this as a combination of is water, located mostly in muscles. beverages, food, and water. Do Astronauts Have Special The fluid in the blood is composed of Nutritional Needs? a noncellular component (plasma) and a Because of potentially reduced thirst If elite athletes like Olympians have cellular component (red blood cells). and appetite, astronauts must make an effort to consume adequate food and special nutritional needs, do astronauts NASA measured the various body water water. Water availability on the shuttle too? During the shuttle flights, compartments using dilution techniques: was never an issue, as the potable nutrition research indicated that, in total body water; extracellular volume water was a by-product of the fuel general, the answer is no. Research, (all water not in cells), plasma volume, cells. With flights to the Russian space however, provided the groundwork for and blood volume. Because of the lack long-duration missions, such as for the station Mir and the ISS, the ability to

Major Scientific Discoveries 387 transfer water to these vehicles Renal Stones body and drives blood pressure up, provided a tremendous help as the while atrial natriuretic peptide controls As stated, the kidney controls excess space agencies no longer needed to body water, Na, K, and fat (adiposity), water. But, what happens if a crew launch water, which is very heavy. thereby reducing blood pressure. member is dehydrated due to sweating In the first few days of spaceflight, A much-improved understanding of or not consuming enough water? During antidiuretic hormone is high but it then water loss during EVAs occurred spaceflight, urine becomes very readjusts to controlling body water. during the shuttle period. This concentrated with low levels of body Aldosterone and atrial natriuretic information led to the ISS EVA water. This concentrated urine is doubly peptide reflect Na and water intakes to standards. Dehydration may increase changed by immediately entering prevent high blood pressure. body heat, causing dangerously high microgravity, and the bone starts losing temperatures. Therefore, adequate calcium salts. Although these losses Research from several Spacelab water intake is essential during EVAs. were not significant during the short missions demonstrated that in NASA determined how much water shuttle flights, this urinary increase had microgravity, astronauts’ bodies are was needed for long EVAs (6 hours the potential to form calcium oxalate able to adjust to the changes induced outside the vehicle, with up to 12 hours renal stones. Furthermore, during by microgravity, high Na intakes, in the EVA suit). Due to the concern spaceflight, protein breakdown increases and the stress of spaceflight. During for dehydration, water supplies due to muscle atrophy and some of the spaceflight, Na intakes are generally were 71 0 to 946 ml (24 to 32 oz, or end products could also promote renal high while K intakes are low as 3 to 4 cups) in the in-suit drink bag stones. Due to the potential problem of compared to needs. The astronauts (the only nutrition support available renal stones, crew members were adjust to microgravity within a few during EVA). strongly encouraged to consume more days. Although astronauts have less water than their thirst dictated. This body water and a headward shift of How Spaceflight Affects work led to the development of water, these regulatory hormones Kidney Function countermeasures for ISS crew members. primarily reflect dietary intakes.

Does the headward fluid shift decrease Sodium and Potassium: Electrolytes The implications of these data for kidney function? The kidneys depend Important for Health long-duration flights, such as the ISS, on blood flow, as it is through plasma remain unknown. While on Earth, high that the renal system removes just the The electrolytes sodium (Na) and Na intakes are most often associated right amount of excess water, sodium, potassium (K) are essential components with increasing blood pressure. Such metabolic end products like urea and of healthy fluid balance; Na is a intakes also may exacerbate bone loss, creatinine, as well as other metabolic primarily extracellular ion while K is which is a problem for astronauts on products from foods and contaminates. a primarily intracellular ion. They long-duration spaceflights. So, what is the affect of reduced heart are essential for osmotic balance, cell rates and lower blood volumes? function, and many body chemical How Many Calories Do Astronauts Astronauts on several Spacelab flights reactions. K is required for normal Need in Spaceflight? participated in research to determine muscle function, including the heart. Because astronauts eat less, research any changes in renal function and the With changes in fluid balance, what determined the energy level (calories) hormones that regulate this function. happens to these electrotypes, needed during spaceflight. For selected When the body needs to conserve especially in their relationship to missions, astronauts completed food water, such as when sweating or not kidney and cardiovascular function? records with a bar code reader to obtain hydrating enough, a hormone called Total body water levels change with good information about dietary intake antidiuretic hormone prevents water changes in body weight. With weight during spaceflights. These studies loss. Similarly, when the body has too loss, liver glycogen (polymers of showed that most astronauts ate less little sodium, primarily due to diet and glucose) stores that contain significant than their calculated energy needs—on sweating, aldosterone keeps sodium associate water are lost, followed by average, about 25% less. loss down. All the experiments showed tissue water—fat 14% and lean body that these mechanisms worked fine in Scientists completed two types of mass 75% water. Antidiuretic hormone spaceflight. We learned not to worry research for measuring astronauts’ conserves body water. Aldosterone about the basic functions of the kidney. body energy use. Energy can be increases the volume of fluid in the

388 Major Scientific Discoveries determined from the products of energy thus energy expenditure added up to bone. NASA confirmed this initial metabolism: carbon energy sources like a fairly high level. The lower energy observation of bone loss in the 1990s by carbohydrates, protein, or fat + oxygen levels occurred when crew members using the latest biological markers (O 2) = heat + carbon dioxide (CO 2). were within the payload bay, primarily technology. In fact, research showed We used two methods for shuttle doing less-demanding work for short that as soon as the astronauts arrived in flights. For most flights, all the expired periods. With the construction of the space, they started losing bone. CO 2 was removed by chemical reaction ISS, EVA activity increased along Vitamin D is essential for the body with lithium hydroxide (LiOH) so the with duration to about 4 to 8 kJ/hr (250 to absorb the dietary Ca that is used for amount of CO 2 produced during a flight to 500 kcal/hr). For an 8-hour EVA, bone and other tissue functions. could be determined. CO 2 that was this was significant. Of course, as Vitamin D syntheses occur in the skin absorbed into the LiOH could be previously described, increased energy during exposure to sunlight. In measured at the end of the flight to expenditure increased water needs. spacecraft, however, sunlight is not determine the energy use by the crew tolerated: the rays are too strong over the entire mission. The second Protein and Amino Acids: Essential because flights take place above the method was to determine the amount for Maintenance of Muscle Function protective atmosphere. Studies of CO 2 and water loss over 3 to 5 days Protein and its components (amino completed during the Shuttle-Mir and of time per astronaut. Astronauts acids) are essential for all body European Space Agency research consumed two stable isotopes (not chemical reactions, structure, and programs showed low vitamin D levels radioactive), deuterium and 18 O, and muscles. In spaceflight, total body could be a problem for Ca absorption the levels of these isotopes in urine protein turnover increases as measured and good bone health. A vitamin D were measured over a period of several by the loss of the orally ingested stable supplement is provided for ISS days. The O 2 occurs in the CO 2 and isotope 15 N-glycine, which was long-duration spaceflights. water, but deuterium is only in the measured in body tissues such as saliva water; thus the method allowed for the and blood. Glycine is an amino acid Too Much Iron May Be Toxic determination of the CO 2 produced by that occurs abundantly in proteins, so an astronaut. Surprisingly for both Changes in astronaut’s red blood cells changes in blood levels indicate the methods, the levels of energy used were and iron (Fe) levels are similar to those amount of glycine moved to the tissues the same in flight as on Earth. As a of a person who lives at a high altitude for protein syntheses. Some of the result of this research, NASA dietitians (e.g., 3,658 m [1 2,000 ft]) coming to increased turnover may be due to the use gender and weight, along with sea level. Both have too much available catabolic state of weight loss found allowing for moderate activity values, Fe (i.e., not bound up in red blood cells). with many astronauts due to to calculate astronauts’ energy needs for lower-than-needed energy intakes. Fe is an important part of red blood spaceflight. This method has worked There is evidence, even with short-term cells that brings oxygen from the for many years to ensure adequate shuttle flights, that skeletal muscle lungs to the tissues. Low levels of red provision of space foods. function decreases. The mild stress of blood cells cause fatigue. The initial One of the major contributions of EVA spaceflight found with hard-working decrease in plasma volume produces research is the increased ability to astronauts may increase protein an increased concentration of red predict energy expenditure during breakdown. Increased stress was blood cells. The body may then spacewalks. EVAs were routinely determined by increased levels of blood perceive too many red blood cells conducted from the shuttle. Energy and urinary cortisol. Dietary protein and make adjustments accordingly. expenditure was important for both suit levels are already high in spaceflight. A12% to 14% decrease in the design and dietary intakes before and Protein recommendations are the same number of red blood cells occurs after a spacewalk. After conducting as ground-based dietary guidelines. within a couple of weeks of spaceflight. thousands of EVA hours, NASA To maintain the correct percent of knows that the energy expenditure Bones Need Calcium and Vitamin D red blood cells (about 37% to 51% of was not high for a short period of time, the blood), newly formed red blood Studies with Skylab astronauts in the similar to walking 4 to 6.4 kph cells are destroyed until a new 1970s and shuttle crew members found (2.5 to 4.0 mph). Nearly all EVAs equilibrium is achieved. The red calcium (Ca) losses increased during lasted around 6 hours, however, and blood cell Fe is released back into the flight, probably through removal from

Major Scientific Discoveries 389 blood and tissues, and no mechanism pathogens are limited by a series of how vaccines work. T cells are part of except bleeding can reduce the level of controls. All shuttle consumables cell-mediated immunity, while B cells body Fe. Excess Fe could potentially (e.g., drinking water and food) and provide the humoral immune response. have toxic effects, including tissue environment (breathing air and Humoral immunity is mediated by oxidation and cardiovascular diseases. surfaces) are carefully examined to soluble antibodies—highly specific Shuttle research showed that the dietary ensure the health and safety of the antimicrobial proteins that help Fe need is below that needed on Earth astronauts. Preflight restrictions are in eliminate certain types of pathogens and because of the reduced need for red place to limit exposure of astronauts to persist in the blood to guard against blood cell production. ill individuals. This system works very future infections. Upon initial exposure well to keep astronauts healthy before, to a unique pathogen such as a herpes Summary of Nutritional Needs Found during, and after spaceflight. Since virus, the number of specific types of for Space Shuttle Astronauts spaceflight is thought to adversely affect T and B cells expands in an attempt to the immune system and increase disease eliminate the infection. Afterward, Nutrient Level potential of microorganisms, the shuttle smaller numbers of memory cells Energy men 12.147 MJ/d (2,874 kcal/d) served as a platform to study immunity continue to patrol the body, ever vigilant 70 kg (~154 pounds) and microbes’ ability to cause disease. for another challenge by that particular Energy women 9.120 MJ/d (2,160 kcal/d) pathogen. An immune response can 60 kg (~132 pounds) The Immune System be too strong at times, leading to 12% to 15% of energy intake self-caused illness without a pathogen. Protein Your immune system quietly works < 85 g/d Examples of this are allergies and for you, a silent army within your body autoimmune diseases. At other times Water 2,000 ml/d protecting you from microorganisms an immune response is not strong Na 1,500 to 3,500 mg/d that can make you sick. If it is enough to fight an infection working well, you never know it. K 3,500 mg/d (immunodeficiency). Acquired But, when it’s not working well, you Immunodeficiency Syndrome (AIDS) Fe 10 mg/d will probably feel it. and cancer chemotherapy are both Vitamin D 10 ug/d The human immune system consists of examples of immunodeficiency Calcium 800 to 1,200 mg many distinct types of white blood cells conditions caused by the loss of one or residing in the blood, lymph nodes, and more types of immune cells. various body tissues. The white blood Changes in Immunity cells of the immune system function in Spaceflight-associated Changes and Risk of Infectious Disease a coordinated fashion to protect the host in Immune Regulation from invading pathogens (bacteria, During Spaceflight Changes in regulation of the immune fungi, viruses, and parasites). Humans are healthy most of the time, system are found with both short- and despite being surrounded by potentially There are various elements of immunity. long-duration spaceflight. Studies infectious bacteria, fungi, viruses, and Innate immunity is the first line of demonstrated that reduced cell mediated parasites. How can that be? The answer defense, providing nonspecific killing of immunity and increased reactivation of is the immune system. This highly microbes. The initial inflammation latent herpes viruses occur during flight. complex and evolved system is our associated with a skin infection at a In contrast, humoral (antibody) guardian against infectious diseases wound site is an example of innate immunity was found to be normal when and many cancers. It is essential that immunity, which is primarily mediated astronauts were immunized during astronauts have a robust, fully by neutrophils, monocytes, and spaceflight. Other shuttle studies functional immune system just as it macrophages. Cell-mediated immunity showed reduced numbers of T cells and is for us on Earth. Astronauts are very provides a specific response to a natural killer cells (a type of white healthy, exquisitely conditioned, and particular pathogen, resulting in blood cell important for fighting cancer well nourished—all factors promoting immunologic “memory” after which and virally infected cells), altered healthy immunity. In addition, immunity to that unique pathogen is distribution of the circulating leukocyte exposures to potential microbial conferred. This is the part of the (white blood cell) subsets, altered stress immune system that forms the basis of hormone levels, and altered cytokine

390 Major Scientific Discoveries levels. Reduced antimicrobial functions humoral immunity. One hypothesis to commonly measured via skin testing. of monocytes, neutrophils, and natural explain immune dysregulation during Briefly, seven common antigens, killer cells also occur when measured spaceflight is a shift in the release of bacteria, Proteus (common in urinary soon after spaceflight. Cytokines are cytokines from Th1 toward Th2 track infections), Streptococcus, small proteins produced by immune cytokines. Data gained from the shuttle tuberculin and Trichophyton (skin cells; they serve as molecular research support this theory. diseases), and yeast, Candida (known to messengers that control the functions increase in the immune compromised), of specialized immune cells. Cytokines Selected Space Shuttle are injected into the forearm skin. are released during infection and serve Immune Studies For most normal individuals, the to shape the immune response. There cell-mediated arm of the immune Hypersensitivity are many cytokines, and they can be system reacts to these antigens within grouped in several ways. Th 1 cytokines Hypersensitivity occurs when the 2 days, resulting in a visible red, are produced by specialized T cells immune response to a common antigen raised area at the site of the injections. to promote cell-mediated immunity, is much stronger than normal. Usually, These reactions are expected and whereas Th2 cytokines promote this manifests itself as a rash and is represent a healthy immune response. The red, raised circular area for each antigen can be quantified. To test astronauts, antigens were injected Immunity Components of Blood 46 hours before landing, and the evaluation of the reaction took place 2 hours after landing. Data showed that, as compared to preflight baseline testing, the cell-mediated immunity was significantly reduced during flight. Both the number of reactions and the

Antibodies individual reaction size were reduced Plasma Humoral immunity during flight. These data indicated for Cytokines the first time that immunity was reduced during short-duration spaceflight. Any associated clinical risks were unknown at the time. The possibility that this Granulocytes Innate immunity phenomenon would persist for White Blood Cells Monocytes long-duration flight was also unknown. Similar reductions in cell-mediated LymphocytesLymymphocytes B lymphocytes - Humoral immunity immunity were reported in Russian T lymphocytes - Cell-mediated immunity cosmonauts during longer missions. Red Blood Cells Natural killer cells - Innate immunity Studies of the Peripheral Mononuclear Cells Peripheral mononuclear cells are Innate immunity comprises the cells and mechanisms that defend the host from blood immune cells. Their numbers infection by other organisms, in a nonspecific manner, and are found in all classes of plant are a measure of the current immune and animal life. status of a subject. During the latter Humoral immunity (involving substances found in the humours, or body fluids) is stages of the 11 -day STS- 71 (1 995) mediated by secreted antibodies that are produced by B lymphocytes and bind to antigens shuttle mission, the shuttle astronauts on the surfaces of invading microbes, which marks the microbes for destruction. and the returning long-duration Cell-mediated immunity is an immune response that involves the activation of astronauts (from Mir space station) macrophages, natural killer cells, antigen-specific cytotoxic T lymphocytes, and the release of various cytokines in response to an antigen. stained samples of their peripheral

Major Scientific Discoveries 391 Herpes Viruses Become Active During Spaceflight

Herpes viruses, the most commonly immunity in astronauts during flight. The urine in response to spaceflight. Healthy recognized latent viruses in humans, causes of reduced immunity are unknown, individuals rarely shed cytomegalovirus cause specific primary diseases but stress associated with spaceflight in urine, but the virus is commonly found in (e.g., chicken pox), but may remain inactive appears to play a prominent role, as the those with compromised immunity. in nervous tissue for decades. When levels of stress hormones increase during Scientists also studied Varicella-Zoster immune response is diminished by stress spaceflight. The resulting decreased virus, the causative agent of chicken pox or aging, latent viruses reactivate and immunity allows the viruses to multiply and shingles. These astronaut studies were cause disease (e.g., shingles). and appear in saliva. The mechanism for the first reports of the presence of this Epstein-Barr virus reactivation seems to be Epstein-Barr virus reactivated and appeared infectious virus in saliva of asymptomatic a reduction in the number of virus-specific in astronauts’ saliva in large numbers individuals. A rapid, sensitive test for T cells leading to decreased ability to keep during spaceflight. Saliva collected during use in doctors’ offices to diagnose shingles Epstein-Barr virus inactive. the flight phase contained tenfold more virus and facilitate early antiviral therapy than saliva collected before or after flight. Cytomegalovirus, another latent virus, resulting in reductions in nerve damage This finding correlated with decreased also reactivated and appeared in astronaut was a product of this study.

Role of Varicella-Zoster Virus in Chicken Pox and Shingles

Childhood chicken pox becomes dormant in the nervous system.

Shingles Outbreak

Hair Shaft Skin Surface

Initial stage consists Blisters resembling of burning pain and chicken pox sensitive skin. develop and ll with pus. Weakened Blisters eventually immune system burst, crust over, reawakens and heal. virus.

Nerve damage can cause Dormant postherpetic Varicella neuralgia. Primary Disease Virus Stress on the (Chicken Pox) immune system allows the latent virus to reactivate Nerve Fiber as shingles.

Reactivation (Shingles)

392 Major Scientific Discoveries blood immune cells with various Habitability and and equipped to facilitate the work that dyes using unique and patented is to be done. equipment developed at Johnson Environmental Health Resource limitations conspire to Space Center. These data showed that severely limit the habitability of space the major “bulk” levels of peripheral Habitability vehicles. Spacecraft usually provide blood immune cells did not appear to The shuttle contributed significantly minimal volume in which crew be altered during flight. to advances in technologies and members can live and work due to processes to improve the habitability the high cost of launching mass into Summary of space vehicles and enable humans space. The spacecraft’s environmental The laboratory capabilities of the to live and work productively in space. control system is usually closed to Space Shuttle allowed our first These shuttle-sponsored advances some degree, meaning that spacecraft systematic assessment of the effects played a key role in our coming to air and water are recycled and their of space travel on the human immune view living and working in space as quality must be carefully maintained system. Most indicators of immunity not only possible but also achievable and monitored. It may be several were altered during short-duration on a long-term basis. months between when food is prepared spaceflight, which is a uniquely and when it is consumed by a space Habitability can be defined as the stressful environment. These stressors crew. There is normally a limited fresh degree to which an environment meets were likely major contributors to the resupply of foods. Care must be taken an individual’s basic physiological and observed changes in immunity and the to assure the quality of the food before psychological needs. It is affected by increased viral reactivation. Latent it is consumed. multiple factors, including the size of viruses were shown to be sensitive the environment relative to the number The following sections illustrate some indicators of immune status. Bacterial of people living and working there of the technologies and processes that pathogens were also shown to be more and the activities to be undertaken. contributed to the habitability of the virulent during spaceflight. It is Other habitability factors include air, shuttle and provided a legacy that will unknown whether these are transient water, and food quality as well as help make it possible for humans to live effects or whether they will persist for how well the environment is designed safely and work productively in space. long-duration missions. These important data will allow flight surgeons to determine the clinical risk for exploration-class space missions (moon, Mars) related to immunology, and to further the development of countermeasures for those risks. These studies and the hardware developed to support them serve as the platform from which new studies on board the ISS were initiated. It is expected that the ISS studies will allow a comprehensive assessment of immunity, stress, latent viral reactivation, and bacterial virulence during long-duration spaceflight.

On STS-90 (1998), three Space Shuttle Columbia crew members—Astronauts James Pawelczyk, Richard Searfoss, and Richard Linnehan—meet on the middeck, where the crew ate, slept, performed science, prepared for extravehicular activities (spacewalks), exercised, took care of personal hygiene needs, and relaxed.

Major Scientific Discoveries 393 Innovations Improve Habilitability visibility and access to the activity area. . d e v r

The latter difficulties can lead to e s e r

Restraints and Mobility Aids s prolonged periods of unnatural postures t h g i r

l l

that may potentially harm muscles or A

One of the most successful aids . e s u developed through the program, and one exacerbate neurological difficulties. o M

e l b r

that will be used on future spacecraft, to a M

Cursor Control Devices n support crew member physical stability a m k c a

in microgravity is foot restraints. r T

The shuttle spacecraft environment h c e

It is nearly impossible to accomplish t i

included factors such as complex g o L tasks in microgravity without stabilizing lighting scenarios, limited habitable © one’s feet. NASA scientists developed volume, and microgravity that could Example of a cursor control device with a trackball several designs to make use of the render Earth-based interface designs as used with ungloved and gloved hands. body’s natural position while in space. less than optimal for space applications. One design has foot loops and Research in space human factors and undesirable characteristics of cursor two-point leg/foot restraints used while included investigating ways to optimize control devices using high-fidelity a crew member works at a glove box. interfaces between crew members and environments. Experiments began in These restraints stabilize a crew spacecraft hardware, and the shuttle ground laboratories and then moved to member. The effectiveness of a restraint proved to be an excellent test bed for the KC -1 35 aircraft for evaluation in a system relates to the simplicity of evaluating those interfaces. short-duration microgravity environment design, comfort, ease of use, during parabolic flight. The experiments For example, while computer use is adjustability, stability, durability, and culminated with flight experiments on quite commonplace today, little was flexibility for the range of the task. board Space Transportation System known about how, or if, typical cursor Other restraint systems developed (STS)-29 (1 989), STS- 41 (1 990), and control devices used on Earth would include handrails, bungee cords, STS-43 (1 991 ). These evaluations and ® work in space. NASA researchers Velcro , and flexible brackets. experiments used on-board crew conducted a series of experiments to Furthermore, foot restraints aid in members to take the devices through gather information about the desirable meeting other challenges such as limited the prescribed series of tasks.

Anchoring Improves Performance

Without Constraints On STS-73 (1995) Astronaut Kathryn Thornton works at the Drop Physics Module on board the Spacelab science module located in the cargo bay of the Earth-orbiting shuttle. Notice that Dr. Thornton is anchoring her body by using a handrail for her feet and right hand. This leaves only one free hand to accomplish her tasks at that workstation and would be an uncomfortable position to hold for a long period of time.

With Constraints Also on STS-73, Astronaut Catherine Coleman uses the advanced lower body extremities restraint at the Spacelab glove box. With Dr. Coleman’s feet and knees anchored for body stability, she has both hands free to work for longer periods, providing her stability and comfort.

394 Major Scientific Discoveries It cannot be assumed that computer equipment, like cursor control devices (e.g., a trackball, an optical mouse), White Light-emitting Diode Illuminators used on Earth will behave the same way in space. Not only does microgravity As the shuttle orbited Earth, the crew experienced a sunrise and sunset every 45 make items “float,” in general the minutes on average. This produced dramatic changes in lighting conditions, making equipment might be used while a crew artificial light sources very important for working in space. member is wearing gloves—and the gloves could be pressurized at the time. Because of power and packaging constraints during the Space Shuttle Program, most For example, a trackball has a certain artificial lights were restricted to fixed locations. With the assembly of the International amount of movement allowed within its Space Station and the maintenance of the Hubble Space Telescope, NASA felt it casing. In space, the ball will float, making it much more difficult to use the would be a great improvement to have lights mounted on all of the shuttle cameras. trackball and be accurate. During These light sources had to be durable, lightweight, and low in power requirements— STS-43, the shuttle crew worked with the characteristics of light-emitting diodes (LEDs). a trackball that was modified to reduce the “play,” and they reported that the In 1995, NASA began using white LED lights for general illumination in camera mechanism worked well. This systems several years in advance of industry. These early lights were designed as modification resulted in the fastest and rings mounted around the lens of each camera. The four payload bay cameras were most accurate responses. equipped with four LED light systems capable of being pointed with the pan-and-tilt Those tests in the flight environment unit of each camera. NASA also outfitted the two robotic arm cameras with LED rings. paved the way for the types of In June 1998, the first white 40 LED illumination system was flown. In May 1999, equipment chosen for the International white 180 LED illuminators were flown. These lighting systems remained in use on Space Station (ISS). The goal was to provide the best equipment to ensure all shuttle flights. quick and precise execution of tasks by crew members. As computer technology advances, NASA will continue investigations involving computer hardware as spacecraft and habitats are developed.

Shuttle Food System Legacy Does NASA have a grocery store in space? The answer is no. One significant change NASA made to the space food system during the Space Shuttle Program, however, was the addition of a unique bar code on each food package to facilitate on-orbit science. When crew members began participating in experiments on orbit that required them to track their food LED rings consumption, a method was needed that would promote accurate data collection Light-emitting diode (LED) rings mounted on the two shuttle cameras in the aft payload while minimizing crew time; thus, the bay of shuttle.

Major Scientific Discoveries 395 bar code. Crew members simply used a handheld scanning device to scan empty food packages after meals. The device automatically recorded meal composition and time of consumption. Not only did bar codes facilitate science, they also had the additional benefit of supporting the Hazard Analysis and Critical Control Point program for space food. Hazard Analysis and Critical Control Point is a food safety program developed for NASA’s early space food system. Having a unique bar code on each food package made it easy to scan the food packages as they were stowed into the food containers prior to launch. The unique bar code could be traced to a specific lot of food. On STS-122 (2007), Astronaut Leland Melvin enjoys his dessert of rehydrated peach ambrosia. This served as a critical control point Also shown is the pair of scissors that is needed to open the pouch. On the pouch is a bar code in the event of a problem with a food that is used to track the food. The blue Velcro ® allows the food to be attached to the walls. product. If a problem had arisen, use of the suitcase-sized food warmer environment. In fact, this system the bar code data collected during the for heating US food products. consisted of a network of systems that scanning could have been used to interacted to create such an environment, locate every package of food from that Food packaging for shuttle foods also in addition to cooling or heating same lot, making traceability much changed during the course of the various Orbiter systems or components. easier and more reliable. This system program. The original rigid, rectangular The network included air revitalization, of bar coding food items carried over plastic containers for rehydratable water coolant loop, active thermal into the ISS food system. foods and beverages were replaced control, atmosphere revitalization by flexible packages that took up less Food preparation equipment also pressure control, management of supply room in storage and in the trash. evolved during the shuttle era. The and wastewater, and waste collection. The increase in crew size and mission earliest shuttles flew with a portable duration that occurred during the The Air Revitalization System assured water dispenser and a suitcase-sized program necessitated this change. the safety of the air supply by using food warmer. The first version of the These improvements continue to lithium hydroxide to maintain carbon portable water dispenser did not benefit the ISS food system. dioxide (CO 2) and carbon monoxide at measure, heat, or chill water, but it did nontoxic levels. It also removed odors allow the crew to inject water into foods and trace contaminants through active and beverages that required it. This Environmental charcoal, provided ventilation in the dispenser was eventually replaced by Environmental Conditions crew compartment via a network of a galley that, in addition to measuring fans and ducting, controlled the cabin’s and injecting water, chilled and heated Maintaining a Healthy Environment During relative humidity (30% to 75%) and it as well. The shuttle galley also Spaceflight temperature (1 8°C [65°F] to 27°C included an oven for warming foods The shuttle crew compartment felt like [80°F]) through cabin heat exchangers to serving temperature. Ironically, an air-conditioned room to astronauts for additional comfort, and supplied air the food preparation system in use living and working in space, and the cooling to various flight deck and on the ISS does not include chilled Environmental Control and Life middeck electronic avionics as well as water and, once again, involves the Support System created that habitable the crew compartment.

396 Major Scientific Discoveries The water coolant loop system sea-level pressure, with an average on the shuttle, overheated electronics, collected heat from the crew mixture of 80% nitrogen and 20% systems leaks, propellants, payload compartment cabin heat exchanger oxygen. Oxygen partial pressure was chemicals, and chemical leaching and from some electronic units within maintained between 20.3 kPa (2.95 posed a risk to air and water quality. the crew compartment. The system pounds per square inch, absolute [psia]) Standards were necessary to define transferred the excess heat to the and 23.8 kPa (3.45 psia), with sufficient safe air and water, along with water coolant/Freon ®-2 1 coolant loop nitrogen pressure of 79.3 kPa (11 .5 monitoring systems to demonstrate a heat exchanger of the Active Thermal psia) added to achieve the cabin total safe environment. Control System, which then moved pressure of 101 .3 kPa (1 4.7 psia) excess heat from the various Orbiter +/- 1.38 kPa (0.2 psia). The Pressure Air systems to the system heat sinks using Control System received oxygen from Both standards and methods as well Freon ®-2 1 as a coolant. two power reactant storage and as instruments to measure air quality distribution cryogenic oxygen systems were needed to ensure air quality. For During ground operations, the ground in the mid-fuselage of the Orbiter. the shuttle, NASA had a formalized support equipment heat exchanger in the Nitrogen tanks, located in the process for setting spacecraft Orbiter’s Freon ®-2 1 coolant loops mid-fuselage of the Orbiter, supplied maximum allowable concentrations. rejected excess heat from the Orbiter gaseous nitrogen—a system that was Environmental standards for astronauts through ground systems cooling. Shortly also used to pressurize the potable and must consider the physiological effects after liftoff, the flash evaporator wastewater tanks located below the of spaceflight, the continuous nature of (vaporization under reduced pressure) crew compartment middeck floor. airborne exposures, the aversion to was activated and provided Orbiter heat drinking water with poor aesthetic rejection of the Freon ®-2 1 coolant loops Three fuel-cell power plants produced properties, and the reality that astronauts through water boiling. When the Orbiter the astronauts’ potable water, to which could not easily leave a vehicle if it was on orbit and the payload bay doors iodine was added to prevent bacterial were to become dangerously polluted. were opened, radiator panels on the growth, that was stored in water tanks. underside of the doors were exposed to Iodine functions like the chlorine that On Earth, plants remove CO 2—a gas space and provided heat rejection. is added to municipal water supplies, exhaled in large quantities as a result If combinations of heat loads and the but it is less volatile and more stable of human metabolism—from the Orbiter attitude exceeded the capacity of than chlorine. Condensate water and atmosphere. By contrast, CO 2 is one the radiator panels during on-orbit human wastewater were collected of the most difficult compounds to operations, the flash evaporator was into a wastewater tank, while solid deal with in spaceflight. For example, activated to meet the heat rejection waste remained in the Waste Collection accumulation of CO 2 was a critical requirements. At the end of orbital System until the Orbiter was serviced problem during the ill-fated Apollo 13 operations, through deorbit and re-entry, during ground turnaround operations. return flight. As the disabled spacecraft the flash evaporator was again brought returned to Earth, the crew had to into operation until atmospheric Space Shuttle Environmental Standards implement unanticipated procedures to pressure, about 30,480 m (1 00,000 ft) manage CO 2. This involved duct-taping We live on a planet plagued with air and below, no longer permitted the flash filters and tubing together to maintain and water pollution problems because evaporation process to provide adequate CO 2 at tolerable levels. Such extreme of the widespread use of chemicals for cooling. At that point, the ammonia measures were not necessary aboard energy production, manufacturing, boilers rejected heat from the Freon ®-2 1 shuttle; however, if the crew forgot to agriculture, and transportation. To coolant loops by evaporating ammonia change out filters, the CO 2 levels could protect human health and perhaps the through the remainder of re-entry, have exceeded exposure standards entire planet, governmental agencies landing, and postlanding until ground within a few hours. set standards to control the amount cooling was connected to the ground of potentially harmful chemicals that Although older limits for CO 2 were support equipment heat exchanger. can be released into air and water set at 1%, during NASA’s new Atmosphere revitalization pressure and then monitor the results to show standard-setting process with the control kept cabin pressure around compliance with standards. Likewise, National Research Council it became

Major Scientific Discoveries 397 clear that 1% was too high and, therefore, the spacecraft maximum Combustion Product Analyzer Ensured allowable concentration was reduced to 0.7 %. Even this lower value proved Crew Breathed Clean Air After Small to be marginal under some conditions. For example, the shuttle vehicle did Fire in Russian Space Station not have the capability to measure local pockets of CO 2, and those pockets The combustion product analyzer flew on every Space Shuttle flight from 1990 could contain somewhat higher levels through 1999 and proved its value during the Shuttle-Mir Program (1995-1998). than were found in the general air. On the seventh joint mission in 1998, no harm seemed to have occurred during an That was especially true in the absence inadvertent valve switch on an air-purifying scrubber. In fact, during this time, the of gravity where convection was not crew—including American Andrew Thomas—participated in a video presentation available to carry warm, exhaled air transmitted back to Earth; however, shortly after the valve switch, the crew upward from the astronaut’s breathing zone. Use of a light-blocking curtain experienced headaches. As on Earth, when occupants of a house or building during a flight caused the crew to experience headaches simultaneously, it can indicate that the air has been severely experience headaches on awakening, degraded. The crew followed procedures and activated the combustion product and this was attributed to accumulation analyzer, designed to detect carbon monoxide (CO), hydrogen cyanide, hydrogen of CO 2 because the crew slept in a chloride, and hydrogen fluoride. The air contained over 500 parts per million of CO, confined space and the curtain significantly above acceptable concentrations. This high concentration was produced obstructed normal airflow. by hot air flowing through a paper filter and charcoal bed and then into the cabin Setting air quality standards for when the valve was mistakenly switched on. The combustion product analyzer was astronaut exposures to toxic used to follow the cleanup of the CO. Archival samples confirmed the accuracy of the compounds is not a precise science analyzer’s results. The success of this analyzer and its successor—the compound and is complicated. NASA partnered with the National Research Council specific analyzer-combustion products—led to the inclusion of four units (compound Committee on Toxicology in 1989 specific analyzer-combustion products) on the International Space Station and a to set and rigorously document air combustion products analyzer on future crew exploration vehicles. quality standards for astronauts during shuttle spaceflight. The spaceflight environment is like Earth in that exposure standards can control activities when environmental monitors suggest the need for control. For example, youth outdoor sports activities are curtailed when ozone levels exceed certain standards on Earth. Likewise, spacecraft maximum allowable concentrations for carbon monoxide, a toxic product of combustion, were used to determine criteria for the use of protective masks in the event of an electrical burn. The shuttle Flight Rules provided the criteria. Ranges for environmental Commander Robert Gibson and Astronaut Jan Davis check the monitoring instruments were also based combustion product analyzer during STS-47 (1992). on spacecraft maximum allowable

398 Major Scientific Discoveries Measuring Airborne Volatile Organic Compounds

Volatile organic compounds are airborne contaminants that pose Contaminants: Elektron Incident on a problem in semi-closed systems such as office buildings with the Russian Space Station Mir contributions from carpets, furniture, and paper products as well 0.25 as in closed systems such as airplanes and spacecraft. These Compounds: Toluene 0.2 contaminates cause headaches, eye and skin irritation, dizziness, ) 3 Benzene m / and even cancer. g Ethylbenzene m (

0.15

n Xylenes o i t

NASA needed to be able to measure such compounds for the a r t n

e 0.1

International Space Station (ISS), a long-term closed living situation. c n o Therefore, in the latter 1990s, the shuttle was used as a test bed C 0.05 for instruments considered for use on the ISS.

0 Shuttle flights provided the opportunity to assess the performance Pre-incident Post release Post release Normalized 62 minutes 296 minutes of a volatile organic analyzer-risk mitigation experiment in 9/04/06 9/18/06 9/18/06 9/25/06 microgravity on STS-81 (1997) and STS-89 (1998). Results This chart plots the course of the confirmed component function and improved the instrument built Elektron incident showing the concentrations of toluene, benzene, for ISS air monitoring. ethylbenzene, and xylenes—all serious toxins—released into the The volatile organic analyzer air. In 2004, the levels of the four operated episodically on ISS contaminates were very low, as measured by the volatile organic since 2001 and provided analyzer and grab samples returned timely and valuable to Earth for analysis. During the information during the incident, the analyzer measured increases in the four compounds. Elektron (Russian oxygen Grab samples confirmed the higher generation system) incident in levels for these compounds and verified that the analyzer had September 2006 when the worked. The next available data crew tried to restart the showed the contaminants had Elektron and saw what returned to very low levels. appeared to be smoke emanating from the device. The volatile organic analyzer collected and analyzed samples prior to the event and During the STS-89 shuttle dock during cleanup. Data showed with Russian space station Mir, Astronaut Bonnie Dunbar goes that the event had started through her checklist to start before the crew noticed the the volatile organic analyzer sample acquisition sequence. smoke, but the concentrations of the contaminants released were not a health hazard.

Major Scientific Discoveries 399 concentrations. For example, the arriving at the scene of a chemical Toxic containments may be released monitoring requirements for hydrogen spill, fire, or building where occupants from burning materials depending cyanide, another toxic combustion have been overcome by noxious on the type of materials and level of product, were based on spacecraft fumes. Additionally, these instruments oxygen. For spaceflight, NASA maximum allowable concentrations to must be capable of determining when identified five marker compounds: determine how sensitive the monitor the cleanup efforts have made it safe carbon monoxide (odorless and must be. By analogy with Earth-based for unprotected people to return. When colorless gas) released from most environmental monitoring, spaceflight a spill, thermodegradation, or unusual thermodegradation events; hydrogen monitors needed the ability to indicate odor occurs on a spacecraft, crew chloride released from polyvinyl when safe conditions had returned so members are the first responders. chloride; hydrogen fluoride and that normal operations could resume. They need the tools to assess the carbonyl fluoride associated with situation and track the progress of the Teflon ®; and hydrogen cyanide released Water cleanup. As a result of shuttle from Kapton ®-coated wire and NASA recognized the need for unique experiments, NASA was able to polyurethane foam. The concentration water-quality standards. Although the provide crews with novel instruments range monitored for each marker effort to set specific water-quality to manage degradations in air quality compound was based on the established standards, called spacecraft water caused by unexpected events. spacecraft maximum allowable exposure guidelines, did not begin until concentrations at the low end and, at The combustion products 2000, NASA quickly realized the value the other end of the range, an estimated analyzer addressed spacecraft of these new limits. One of the first highest concentration that might be thermodegradations events, which spacecraft water-exposure guidelines released in a fire. can range from overheated wiring to set was for nickel, a slightly toxic metal a full-fledged fire. Fire in a sealed, An upgraded combustion product often found in water that has been held remote capsule is a frightening event. analyzer is now used on the ISS, in metal containers for some time. A small event—overheated wire demonstrating that the technology and The primary toxic effect of concern was (odor produced)—occurred on research on fire produced methods that nickel’s adverse effect on the immune STS-6 (1 983), but it wasn’t until 1988, detect toxic materials. The results system. High nickel levels had been when technology advances improved indicate when it is safe for the astronauts observed from time to time in the shuttle the reliability and shrank the size of to remove their protective gear. water system based on the existing monitors, that a search for a requirements in NASA documents. combustion products analyzer was This sometimes caused expensive and initiated. Before the final development Safeguarding the Astronauts schedule-breaking activity at Kennedy of the analyzer, however, a more From Microorganisms— Space Center to deal with these events. significant event occurred on STS-28 Prevention of Viral, Bacterial, When National Research Council (1 989) that hastened the completion of and Fungal Diseases experts accepted a new, higher the instrument. On STS-28, a small standard, the old standard was no Certain bacteria, fungi, and viruses portion of teleprinter cable pyrolyzed longer applied to shuttle water and the cause acute diseases such as upper and the released contaminants could nickel “problem” became history. respiratory problems, lung diseases, have imperiled the crew if more of the and gastrointestinal disease as well as cable had burned. The combustion Toxicants From Combustion chronic problems such as some products analyzer requirements were to cancers and serious liver problems. Fire is always a concern in any measure key contaminants in the air In space, astronauts are exposed to environment, and a flame is sometimes following thermodegradation incidents, microorganisms and their by-products difficult to detect. First responders track the effectiveness of cleanup from the food, water (both used must have instruments to quickly efforts, and determine when it was safe for food and beverage rehydration, assess the contaminants in the air on to remove protective gear.

400 Major Scientific Discoveries and for personal hygiene), air, microorganisms produced changes that time and were later used to develop interior surfaces, and scientific would prevent problems for the ISS contamination limits for the ISS and investigations that include animals and the next generation of crewed the next generation of crewed vehicles. and microorganisms. The largest vehicles. With assistance from industry Microbial growth in the closed threat to the crew members, however, and government standards (e.g., environment of spacecraft can lead to is contact with their crewmates. Environmental Protection Agency) a wide variety of adverse effects and expert panels, NASA established The shuttle provided an opportunity including infections as well as the acceptability limits for bacteria and to better understand the changes in release of volatile organics, allergens, fungi in the environment (air and microbiological contamination and toxins. Biodegradation of critical surfaces) and consumables (food because, unlike previous US spacecraft materials, life support system fouling, and water). Preflight monitoring for for human exploration, the shuttle and bio-corrosion represent other spaceflight was thorough and included was designed to be used over many potential microbial-induced problems. the crew, spaceflight food, potable years with limited refurbishment Shuttle crew members sometimes water, and vehicle air and surfaces between missions. Risks associated reported dust in the air and occasional to ensure compliance with these with the long-term accumulation eye irritation. In-flight monitoring acceptability standards. NASA of microorganisms in a crewed showed increased bacterial levels in the reviewed all flight payloads for compartment were unknown at the shuttle air as the number of days in biohazardous materials. Space Shuttle start of the shuttle flights; however, space increased. Dust, microbes, and acceptability limits evolved with many years of studying these even water droplets from a simple

Adverse Effects of Microorganisms

n Infectious diseases n Toxin production n Plant diseases n Allergies n Food spoilage n Volatile release n Material degradation n Immune alteration n Environmental contamination

Astronauts Megan McArthur, Michael Massimino (center), and Andrew Feustel prepare to eat a meal on the middeck of Atlantis (STS-125 [2009]).

Major Scientific Discoveries 401 sneeze settle out on Earth. The human body alone sheds about 1 billion skin As illustrated, a high-efficiency particulate cells every week. Particles remain air (HEPA) filter removes suspended in space and carry particles from recirculated microorganisms and allergens that pose air, resulting in improved a health risk to the crew. air quality. The HEPA filter in the air-purification The shuttle’s air filters were system on the International designed to remove particles greater Space Station (ISS), as than 70 micrometers. The filters pictured below, is of a higher quality than removed most skin cells (approximately purification systems used 100 micrometers) and larger airborne in offices and homes. contaminants (e.g., lint); however, they did not quickly remove smaller contaminants such as bacteria, viruses, and particulates. When the shuttle was modified for longer flights of up to 2 weeks, an auxiliary cabin air cleaner provided filtration that removed particles over 1 micrometer. As the air recirculated through the vehicle, the filter captured skin cells, lint, microorganisms, and other debris. This resulted in much-improved air quality. These high-efficiency particulate air (HEPA) filters (99.97% efficient at removing particles >0.3 micrometers) provide dust- and microbe-free air. This led HEPA Filter on the ISS to the inclusion of HEPA filters in the Air Revitalization System on the ISS where monitoring has shown that air quality has been maintained below These challenges provided maintaining relative humidity below stringent microbial requirements. opportunities for improvements that 70%, avoiding condensation buildup, HEPA filters are also planned for served as “lessons learned,” which were implementing rigorous housekeeping, other crewed vehicles. applied to all future missions. Lessons maintaining air and water filtration, learned from the shuttle experiences and judicially using disinfectants Microbial growth can result in led to NASA’s current approach of are effective steps limiting the volatile chemicals that can produce prevention first and mitigation second. adverse effects of microorganisms. objectionable odors or irritants. For Many microbiological risks associated In all, the microbiological lessons example, during the STS-55 (1 993) with living in space can be pre vented learned from the Space Shuttle era mission, the crew reported a noxious or mitigated to acceptable levels resulted in improved safety for all odor that was later found by extensive through engineering approaches. future spacecraft. ground studies to be a mixture of Prevention strategy begins with the three dimethyl sulfides resulting from design phase and includes steps that the bacterial metabolism of urine in discourage excessive microbial a waste storage container. growth. Use of antimicrobial materials,

402 Major Scientific Discoveries Astronaut Health Care Shuttle–Mir, Shuttle-International Space mission planners to ensure that all Station (ISS), post-Columbia (2003) facets of coordinating the basic tenets accident and, finally, the ISS assembly of personnel, equipment, procedures, Astronaut health care includes all issues completion. All of these evolutionary and communications were included that involve flight safety, physiological phases required changes in the selection in mission support. During the shuttle health, and psychological health. of crews for spaceflight, preparation era, the Mission Control Center was During the Space Shuttle Program, for spaceflight, on-orbit health care, and upgraded, significantly improving space medicine was at the “heart” of postflight care of the astronauts. communications among the shuttle each issue. flight crew, medical team, and other Astronauts maintained their flight Space medicine evolved during the flight controllers with the flight director status, requiring both ambulatory shuttle’s many transitional phases, from for the mission. Additionally, the and preventive medical care of their the experimental operational test vehicle longitudinal study of astronaut health active and inactive medical conditions. to pre-Challenger (1 986) accident, began with all medical data collected Preflight, on-orbit, and postflight post-Challenger accident, unique during active astronaut careers. NASA medical care and operational space missions such as Department of Defense used post-retirement exams, conducted medicine training occurred for all and Hubble, Spacelab/Spacehab, annually, to study the long-term effect flights. The medical team worked with Extended Duration Orbiter Project, of short-duration spaceflight on crews.

Astronaut Selection and Space Adaptation Syndrome Medical Standards Due to increasing levels of flight The first thing an astronaut noticed was a fluid shift from his or her lower extremities experience and changes in medical to his or her torso and upper bodies, resulting in a facial fullness. Ultimately, this fluid delivery, medical standards for shift caused a stretch on the baroreceptors in the arch of the aorta and carotid arteries astronaut selection evolved over the and the astronaut would lose up to 1.5 to 2 L (1.6 to 2.1 qt) of fluid. shuttle’s 30 years, as it was important that the selected individuals met certain Secondly, over 80% of crew members experienced motion sickness, from loss of medical criterion to be considered as appetite to nausea and vomiting. Basic prevention included attempting to maintain an having the “right stuff.” The space Earth-like orientation to the vehicle. Also, refraining from exaggerated movements agency initially adopted these standards from a combination of US Air Force, helped. If symptoms persisted despite preventive measures, medications in an oral, US Navy, and Federal Aviation suppository, or injectable form were flown to treat the condition. Administration as well as previous The next thing crew members noticed was a change in their musculoskeletal system. standards from the other US space programs. The shuttle medical In space, the human body experiences a lengthening and stretching of tendons and standards were designed to support ligaments that hold bones, joints, and muscles together. Also, there was an unloading short-duration spaceflights of as many of the extensor muscles that included the back of the neck and torso, buttocks, and as 30 days. NASA medical teams, along back of the thighs and calves. Preventive measures and treatment included on-orbit with experts in aerospace medicine exercise, together with pain medications. and systems specialties, met at least every 2 years to review and update Additional changes were a mild decrease in immune function, smaller blood cell standards according to a combination volume, and calcium loss. Other problems included headache, changes in visual acuity, of medical issues related to flights and sinus congestion, ear blocks, nose bleeds, sore throats, changes in taste and smell, the best evidence-based medicine at that time. These standards were very constipation, urinary infections and difficulty in urination, fatigue, changes in sleep strict for selection, requiring optimum patterns with retinal flashes during sleep, minor behavioral health adjustment reactions, health, and they eventually led to adverse reactions to medications, and minor injuries.

Major Scientific Discoveries 403 the ISS medical requirements for procedures and processes such as a was lost on orbit during physiological long-duration spaceflight. family/astronaut private communication changes to the cardiovascular system. that allowed the astronaut another It was also important to maximize the Preventive medicine was the key to avenue to express concerns. health and readaptation of the crew on success. Astronauts had an annual return to Earth in case emergency spaceflight certification physical Over the course of the Space Shuttle bailout, egress, and escape procedures exam to ensure they remained healthy Program, NASA provided improved needed to be performed. for spaceflight, if assigned. Also, if a physical conditioning and rehabilitation potential medical condition or problem medicine throughout the year to keep The addition of two NASA-trained crew was diagnosed, it was treated crews in top physical shape. Before and medical officers further improved appropriately and the astronaut was during all shuttle flights, the agency on-orbit medical care. Training included retained for spaceflight. M edical exams provided predictions on solar activity contents of the medical kits with an were completed 10 days prior to launch and accumulation of the radiation understanding of the diagnostic and and again at 2 days prior to launch to astronauts received during their careers therapeutic procedures contained within ensure that the astronaut was healthy to help them limit their exposure. the medical checklist. These classes and met the Flight Readiness Review were commonly referred to as “4 years Prior to a shuttle mission, NASA requirements for launch. Preventive of medical school in three 2-hour trained all astronauts on the effects of health successfully kept almost 99% of sessions.” Crew medical officers learned microgravity and spaceflight on their the astronauts retained for spaceflight basic emergency and nonemergency bodies to prepare them for what to duties during their careers with NASA. procedures common to spaceflight. expect in the environment and during This training included how to remove the physiological responses to foreign bodies from the eye; treat ear microgravity. The most common Crew Preparation for Flight blocks and nose bleeds; and start IVs medical concerns were the space and give medications that included IV, Approximately 9 months prior to each adaptation syndrome that included intramuscular, and subcutaneous shuttle flight, the medical team and space motion sickness and the injections and taught the use of oral flight crew worked together to resolve cardiovascular, musculoskeletal, and and suppository intake. Emergency any medical issues. The flight medical neurovestibular changes on orbit. Other procedures included training in team provided additional medical effects such as head congestion, cardiopulmonary resuscitation, airway supplies and equipment for the crew’s headaches, backaches, gastrointestinal, management and protection, wound active and inactive medical problems. genitourinary, crew sleep, rest, fatigue, care with Steri-Strip ™ and suture repair, and handling of injuries were also Spaceflight inspired some exceptional bladder catheterization, and needle discussed. The most common types of medical care. Noise was a thoracentesis. NASA taught special environmental issues were radiation, hazard and, therefore, hearing needed classes on how to mitigate the possibility the biothermal considerations of heat to be monitored and better hearing of decompression sickness from an and cold stress, decompression sickness protection was included. Due to the EVA. This incorporated the use of from an extravehicular activity (EVA), presence of radiation, optometry was various EVA prebreathe protocols potable water contamination, carbon important for eye health and for developed for shuttle only or shuttle-ISS dioxide (CO 2), and other toxic understanding the impact of radiation docking missions. Crews were taught to exposures. Re-entry-day (return to exposure on cataract development. recognize decompression sickness and Earth) issues were important because Also, in space visual changes occurred how to medically manage this event by the crew transitioned quickly from with elongation of the eye, thus treating and making a disposition of the microgravity into a hypergravity, requiring special glasses prescribed crew member if decompression sickness then into a normal Earth environment. for flight. All dental problems needed occurred during an EVA. to be rectified prior to flight as well. Countermeasures needed to be Behavioral health counseling was developed to overcome this rapid Environmental exposure specialty also available for the crews and their response by the human body. These classes included the recognition and families, if required. This program, countermeasures included the control management of increased CO 2 along with on-orbit support, of cabin temperature, use of the g-suit, exposure, protection and monitoring in provided the advantage of improved and entry fluid loading, which helped case of radiation exposure from either restore fluid in the plasma volume that artificial or solar particle events, and the

404 Major Scientific Discoveries exposure to those compounds. NASA trained crew members on how to use the Shuttle Medical Kit toxicology database that enabled them to readily identify the exposed material The Shuttle Orbiter Medical System had generic and accessory items and provided and then provide protection to basic emergency and nonemergency medical care common to spaceflight. The themselves during cleanup of toxic contents focused on preventing illnesses and infection as well as providing pain compounds using a specialty contamination cleanup kit. Astronauts control. It also provided basic life support to handle certain life-threatening were also trained on fire and smoke emergencies, but it did not have advanced cardiac life support capabilities. Initially, it procedures such as the rapid quick-don included two small kits of emergency equipment, medications, and bandages; however, mask for protection while putting out this evolved into a larger array of sub packs as operational demands required during the fire and scrubbing the cabin the various phases of the program. The generic equipment remained the same for atmosphere. In such an incident, the every flight, but accessory kits included those mission-specific items tailored for the atmosphere was monitored for carbon monoxide, hydrogen cyanide, and crew’s needs. Overall, the Shuttle Orbiter Medical System included: a medical checklist hydrogen chloride. When those levels that helped the on-board crew medical officers diagnose and treat on-orbit medical were reduced to nontoxic levels, the problems; an airway sub pack; a drug sub pack; an eye, ear, nose, throat, and dental masks were removed. sub pack; an intravenous sub pack; saline supply bags; a trauma sub pack; a sharps The potable water on the shuttle was container; a contamination cleanup kit; patient and rescue restraints; and an monitored 15 and 2 days preflight to electrocardiogram kit. ensure quality checks for iodine levels, microbes, and pH. Crews were instructed in limiting their iodine (bacteriostatic agent added to stored shuttle water tank) intake by installing/reinstalling a galley iodine- reduction assembly device each day that limited their intake of iodine from the cold water. The crews also learned how to manage the potable water tank in case it became contaminated on orbit. Over the course of the program, NASA developed Flight Rules that covered launch through recovery after landing and included risky procedures such as EVAs. These rules helped prevent medical conditions and were approved through a series of review boards that included NASA missions managers, flight directors, medical personnel, and outside safety experts. The Flight Rules determined the preplanned decision on how to prevent or what to do in case biothermal consideration of heat stress hydrazines and nitrogen tetroxide, something went wrong with the shuttle in case the Orbiter lost its ability to ammonia, and halogenated systems. Other controlled activities maintain cooling. Toxicology exposure hydrocarbons such as halon and were rules and constraints that protected specialty classes focused on generic Freon ®. Certain mission-specific toxic and maintained the proper workload, toxic compounds unique to the Orbiter compounds were identified and rest, and sleep prior to flight and for and included hypergolic exposure to antidotes were flown in case of crew on-orbit operations during the presleep,

Major Scientific Discoveries 405 work, and post-sleep periods. The flight-specific sleep and work schedule was dependent on the launch time and Crew Transport Vehicle included the use of bright and dim lights, naps, medications, and shifts in sleep and work patterns. NASA developed crew schedules to prevent crew fatigue—an important constraint for safety and piloted return. Although implemented in the Apollo Program, preflight crew quarantine proved to be essential during the Space Shuttle Program to prevent infectious disease exposure prior to launch. The quarantine started 7 days prior to launch. At that point, all crew contacts were monitored and all contact personnel received special training in the importance of recognizing the signs and symptoms of infectious disease, thus limiting their contact with the Prior to the 1990s’ flight crew if they became sick. This Extended Duration program helped eliminate the exposure Operations Program, of an infectious disease that would immediate postflight delay launch and was successful in that care was conducted only one flight had to be delayed in the “white room” or on a small stairwell platform that mated with the port-side because of a respiratory illness. hatch of the shuttle. Typically, astronaut support personnel, a “suit” technician, and the crew medical team entered the shuttle, postlanding. If a medical condition occurred Readiness for Launch and and a crew member had problems readapting to the Earth environment, this care was On-orbit Health Care conducted in the shuttle interior or on the platform of the “white room” stairwell. One Launch day is considered the most major improvement to landing-day medical care was the change to a mobile postflight risky aspect of spaceflight. As such, crew transport vehicle. This vehicle was redesigned to mate with the Orbiter and medical teams were positioned to work provided private transport of the crew to a location where they could receive better directly with mission managers as well care, if required. The vehicle was outfitted with lounge chairs, a rest room, gurneys, as the shuttle crew during this critical and medical supplies. The crew could first be stabilized. Then, those who didn’t need to stage. On launch day, one crew medical remain on board for research testing could perform a crew walk around the Orbiter. doctor was stationed in the Launch Control Center at Kennedy Space The crew transport vehicle was first used with STS-40 at Dryden Flight Research Center (KSC) with KSC medical Center (DFRC), California, in 1991 and supported all subsequent shuttle flights at both emergency care providers. They had DFRC and Kennedy Space Center, Florida. direct communication with Johnson Space Center Mission Control, Patrick Air Force Base located close to KSC, alternate landing sites at Dryden Flight the KSC rescue forces and trauma teams Once launch occurred and the crew Research Center/Edwards Air Force at a site determined by wind direction. reached orbit in just over 8 minutes, Base, White Sands Space Harbor, and Other forces, including military physiologic changes began. Every transoceanic abort landing medical doctors and US Air Force pararescuers crew member was unique and teams. Another crew medical doctor in helicopters, stood on “ready alert” for responded to these changes differently was pre-staged near a triage site with any type of launch contingency. on a various scale.

406 Major Scientific Discoveries All medical conditions were discussed suit, then on to a full pressure suit lessons learned over time, especially during a private medical communication called the advanced crew escape suit. during the transitional phases of the with the crew every flight day. The An incorporated g-suit could be used to program, continued to refine astronaut results at the end of a discussion were compress lower extremities and the health and medical care. one of the following: no mission impact abdomen, which prevented fluid from (the majority); possible mission impact; accumulating in those areas. Another or mission impact. With possible post-Challenger accident lesson learned Accidents and Emergency mission impacts, further private was to cool the cabin and incorporate Return to Earth discussion with the crew and flight the liquid cooling within the launch and Main engine or booster failures could director, other crew members, and other re-entry suit to prevent heat loads that have caused emergency returns to KSC medical care specialists occurred. could possibly compromise the landing or transoceanic abort landing sites. Fortunately for the program, all possible performance of the vehicle by the NASA changed its handling of mission impacts were resolved with commander and pilot (second in post-accident care after the two shuttle adjustments to the timeline and duties command). Finally, each crew member accidents. Procedures specific for the performed by the crew so the mission used slow, steady motions of his or her medical team were sessions on could continue to meet its objectives. head and body to overcome the emergency medical services with the If a mission impact were to occur, neurovestibular changes that occurred US Department of Defense Manned changes would be made public but not while transitioning from a microgravity Spaceflight Support Office and the specifics of those changes. Due to to an Earth environment. All items included search and rescue and medical the Medical Privacy Act of 1974, details were important that assisted the crew evacuation. This support and training of these private medical conferences in landing the vehicle on its single evolved tremendously after the could not be discussed publicly. opportunity in a safe manner. Challenger and Columbia accidents, Private family communication was incorporating lessons learned. It mainly another important aspect, Postflight Care included upgrades in training on crew psychologically, of on-orbit health equipment that supported the scenarios care. Early in the program, this was Once the landed shuttle was secured of bailout, egress, and escape. not performed but, rather, was from any potential hazards, the medical team worked directly with returning implemented at the start of the The Future of Space Medicine Extended Duration Orbiter Medical crew members. Therefore, medical Project (1 989 -1 996) and involved teams were stationed at all potential NASA’s medical mission continues to flights of 11 days or longer. landing sites—KSC in Florida, Dryden require providing for astronaut health Flight Research Center in California, and medical care. Whatever the future The second riskiest time of spaceflight and White Sands in New Mexico. milestones are for the US space was returning to Earth. To overcome When the crew returned to crew program, the basic tenets of selecting hypotension or low blood pressure healthy astronaut candidates by having during re-entry, the crew employed quarters, they reunited with their families and then completed a postflight strict medical selection standards and certain countermeasures. The crew then retaining them through excellent would fluid load to restore the lost exam and mini debrief. Crew members were advised not to drive a vehicle preventive medical care are of utmost plasma volume by ingesting 237 ml importance. Combining these with (8 oz) of water with two salt tablets for at least 1 day and were restricted from aircraft flying duties due to the operational aspects of coordinating every 15 minutes, starting 1 hour prior all tenets of understanding the to the time of deorbit ignition and to disequilibrium—problems with spatial and visual orientation. NASA personnel, equipment, procedures, finish this protocol by entry interface and communications within the (i.e., the period right before the final performed another postflight exam and a more extensive debrief at return plus training to prepare crews for flight will return stage) for a total fluid loading enhance the success of any mission. time of 90 minutes. Body weight 3 days and, if passed, the crew member determined the total amount ingested. was returned to aircraft flight duties. At the closing stages of the Space After the Challenger accident, NASA Mission lessons learned from debriefs Shuttle Program, no shuttle mission developed a launch and re-entry suit were shared with the other crew was terminated or aborted because of that transitioned from the standard medical teams, space medicine a medical condition, and this was a Nomex ® flight suit, to a partial pressure researchers, special project engineers, major accomplishment. and the flight directors. All of these

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