Airsickness - VSA 2009

October 2009 Airsickness

VSA Lecture Series 2009

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Airsickness Notes prepared on airsickness – causes, symptoms, prevention and treatment. Prepared by Jeff Farrow, GGC for the VSA Winter Lecture Series, 2009

Problem for newcomers to the sport, early cross country pilots been taken cross country and for TIF’s/F&F’s Airsickness 2009 Airsickness - VSA 2009 Definition October 2009 ■ Simplistically one of a number of motion induced sicknesses ■ Misnomer – Doesn’t need motion to induce – Not an illness, is physiological ■ Motion Mal-adaptation Syndrome ■ Caused by conflicting stimuli from the various balance organs 2

Definition Types Simply though of as one of a number of forms of motion induced sickness including Vestibular Visual imbalance seasickness airsickness carsickness swing-sickness (carnival rides) camel-sickness (Laurence of Arabia) Canal-Otolith space-sickness

Misnamed It can be the absence of motion as well as presence of motion that can be the issue Cinerama sickness (IMAX etc) It is not an illness or sickness, but a normal physiological response experienced by all if provocation is severe enough More accurately defined as a motion mal-adaptation syndrome Caused by mismatched/absent signals from the various balance organs particularly the eyes, the labyrinth, and the proprioceptor system (muscles and joint position senses)

The only individuals who are immune to are those who have had their vestibular systems destroyed Airsickness 2009 Airsickness - VSA 2009 Incidence October 2009 ■ Initial individual susceptibility varies ■ Individuals develop tolerance with time and experience ■ Incidence – 99% life-raft in heavy seas – 20% USN ab initio trainees *(non-pilot aircrew) – 12% USN advanced trainees* – 8% RPT in severe turbulence – 7% USN in Flight readiness Sorties * – <1% civil RPT operations 3

Incidence Individual susceptibility varies widely, and depends predominately on the type of the motions, as well as a on a number of factors which will be discussed shortly. Individuals usually develop tolerance with continued exposure given time enough to adapt and as long as they don’t develop excessive anxiety over the condition. This is a process called adaptation. This acquired tolerance gradually fades with time, so repeated exposure is needed. This retention also varies with individuals Been a number of studies usually on service recruits. Pre-recruitment questionnaires for RAF had the incidence at 3.6%, increased to 59% on post-acceptance confidential questionnaires Airsickness 2009 Airsickness - VSA 2009 Signs & Symptoms October 2009 ■ Prodrome – Stomach awareness ■ Incipient signs – – Circumoral or facial – Sweating – Apathy, introspection and poor concentration ■ Avalanche Phenomena – Salivation, flushing, light headedness – Vomiting 4

Symptoms and Signs The cardinal symptoms is nausea

The sequence: Stomach awareness - epigastric discomfort and unfamiliar sensation of awareness Prodrome - Nausea of increasing severity Circumoral or facial pallor Sweating (thermal not emotive)

Avalanche phenomena - Salivation, flushing, light headedness, apathy and lack of concentration (instructor may interpret as lack of aptitude/skill) VOMITING Airsickness 2009 Airsickness - VSA 2009 Sequelae October 2009 ■ Often initial transient relief of symptoms, but the cycles repeats with waxing and waning of symptoms

■ Results – Short term - Increasing prostration and inability to function – Medium - Electrolyte and hydration issues – Long term - Apathy, depression, suicide

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Sequelae Vomiting may be followed by temporary relief of symptoms, but if the provocation continues the symptoms recur, with Short term - increasing prostration, and inability to function. Medium term - dehydration and electrolyte disturbance (hypokalemia, ketosis), can result in cardiac arrhythmias or mental changes Long term - apathy, depression and suicide (in the setting of life boats) Airsickness 2009 Airsickness - VSA 2009 Associated Symptoms October 2009 ■ Associated symptoms more variable – Belching and flatulence early – Hyperventilation – Sighing and yawning – Headache or buzzing sensation ■ Post vomiting somnolence ■ Somnolence can be the main symptom instead of nausea in those partially adapted 6

Associated Symptoms Early stages increased salivation, belching and flatulence precede the development of nausea Hyperventilation is occasionally seen, more often sighing and yawning

Somnolence Typically following withdrawal of the provocation feelings of lethargy and somnolence persist for hours. Some individuals the only symptoms evoked by motion is an inordinate desire to sleep. This is typically seen in conditions where the stimulus is low enough that there has been adaptation without malaise. Seems reminiscent of the infantile response of sleep to repetitive motion Airsickness 2009 Airsickness - VSA 2009 Physiology October 2009 ■ Equilibrium is maintained by – Visual system – Vestibular system – Proprioceptive system ■ Integrated in the CNS – Brain stem and cerebellum – unconscious regulation of balance – Cerebral cortex – conscious appreciation of balance

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Physiology The bodies equilibrium is maintained by a number of senses. Visual – Image projected on the retina. Orientate static equilibrium and slow angular and linear velocities. Not effective with faster movement, or if eyes closed. Vestibular – measures static (gravitational) orientation, angular movement, linear and angular acceleration. Less effective with constant linear movement. Effective in darkness and higher speed Proprioceptive . Stress detectors in the muscle and joint ligaments, and pressure detectors in the skin and subcutaneous tissues. Useful for determining gravitational equilibrium, acceleration and linear motion (eg air on body running). Limited sensitivity, affected by change in G-load. High input from the neck area to compensate for the specialist senses being in the head

Input from these receptors is to the CNS, initially to the brain stem and cerebellum but ultimate appreciation of balance is in the temporal lobe of the cortex. Airsickness 2009 Airsickness - VSA 2009 Vestibular Apparatus October 2009

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Vestibular Apparatus Cochlea – hearing Saccule – hearing and vibration sense in lower species, non-functional in humans

Utricle contains the macula or otolith. Consists of hairs topped with denser (x3) rocks. The hairs are connected to nerve fibres. Accelerational forces, including centrifugal and gravitational forces, act on these rocks and bend the hairs. Asymmetry in the length of the hairs gives directional information (the kinocilium is always located to one side of the group of hairs). Different groups of hair cells are orientated in different directions so different groups are stimulated by different positions in space.

Detect – static equilibrium, gravity pulls down on the rocks bending the hair. - linear acceleration, inertia displaces the rocks bending the hairs - constant angular velocity, changing orientation leads to changing groups of hairs being stimulated

Semicircular canals in three different axes (with head bent forward 30° external horizontal, superior forwards and 45° outwards, posterior backwards and 45° outwards). The ampullae contain a gelatinous vane of similar density to the fluid in which hairs are embedded, with nerve fibres connected to them (the cupule). Movement of the vane in one direction stimulates the nerve, in the other direction inhibits it.

Detect – angular acceleration causes the canals to turn and the fluid to remain still due to inertia, this causes a flow of fluid which bends the cupule generating a signal (say an increase). With constant rotation the fluid catches up due to friction and the signal settles back to a resting tone. With deceleration the reverse occurs, the fluid keeps moving for a while, the vane bends the other way, and the hair cells generate the opposite signal (a decrease). Sensitivity 1°/sec 2.

By detecting changes in acceleration these organs will predict a change in position before it occurs (the otolith only after it occurs) enabling one to maintain balance.

Also maintain visual fixation during fast rotation through nystagmus Airsickness 2009 Airsickness - VSA 2009 CNS Mechanisms October 2009

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CNS Mechanisms - The various equilibratory inputs converge at the level of the brain stem. (level of these depend on receptivity). - They are transmitted to the cerebellum where they are compared with a stored copy of expected motion cues accumulated from previous experience. (retention) (mal de debarquement) - The output of this centre is a mismatch signal, transmitted through to the motor control system as well as updating the internal model (adaptation) - A sustained mismatch signal gradually accumulates (slow onset of symptoms) and may reach a threshold to stimulate the motion sickness response. This mechanism must also include some degree of leak as adaptation can occur without motion sickness. These features are suggestive of a neurohumoral mechanism though the factors involved have not been identified. - These factors act in turn on the vomiting centre of the medulla oblongata (brainstem)

Why Vomiting? Motion sickness is not a sensation that would be expected in unaided man. Without technology or domestication of animals there are no likely situations where unaided man would develop motion sickness. The vestibular mechanism are complex neural mechanisms relatively exposed to the blood stream compared to the CNS behind the blood brain barrier. They serve a further function in being the receptors for neurotoxins present in the blood stream. Neurotoxins will affect the vestibular mechanism causing a “motion mismatch” signal, and thus induce a protective emetic reflex. The threshold mechanism protects against transient signals involved in normal motion. Neurotoxins found in nature in various bacterial (clostridium botulism), plant (horse chestnut) and small animal (dart frog) sources likely to be potential human food sources. Airsickness 2009 Airsickness - VSA 2009 Predisposing Factors October 2009 ■ Other forms of motion sickness ■ Other tasks ■ Stress ■ Age ■ ■ Sex ■ Odours ■ Lifestyle – Smoking – Fitness – Diet – 10

Predisposing Factors Previous susceptibility - Other forms of motion sickness increase the risk, lack decreases the risk (with the exception of space sickness) Other Tasks - Individuals involved concentrating in mental tasks are less likely to develop symptoms (though not if fixated inside the cabin) Personality - Anxiety is a potent potentiator of airsickness. Of course anxiety can cause vomiting in its own right, and the two can be hard to differentiate, fear of flight, or fear of vomiting can be a precipitant. The aggravation by presence of motion being the main differentiating factor. Other personality factors such as emotional lability, introversion increase risk. Age – rare before age two years of age, peaks in childhood (3-12), and tolerance slowly improves subsequently (OFITTH) Sex – females 1.7:1 over males, particularly more so around period time, or while on the pill Fatigue increases susceptibility Odours can be a trigger, usually seen in the situation of another passenger vomiting, but also other environmental odours eg smoke stacks (eg Yallorn Valley) Smoking increases susceptibility Fitness both low and high (increased vagal tone) increase risk Diet - heavy/protein rich/fatty foods , carbohydrates better - alcohol and other stomach irritants - carbonated beverages Airsickness 2009 Airsickness - VSA 2009 Prevention October 2009 ■ Minimise motion mismatch – Avoid rough conditions – Avoid aerobatics – Seating position ■ Minimise anxiety – Instructing style – Take over at high work load ■ Adaptation 11

Prevention Minimise motion, both total and mismatch - choose calm flying conditions - avoid aerobatics and other - keep horizon in sight, encourage focus outside the fixed visual environment of the cabin, , don’t fix your gaze on individually moving objects, such as nearby cloud, just scan generally. Some find closing eyes can help, others this exacerbates the condition. - position in the aircraft with least movement (often closest to the centre of lift, but may conflict with maintaining external view) - let the sufferer fly as much as possible, so A/C movements are more predictable to the sufferer - minimise head movement, particularly sudden movements Minimise anxiety - Instructor create relaxed environment, avoid shouting - take over at high work load stages - Generally flying as smoothly as possible Adaptation - the process of gradual introduction to the provocative stimulus, and once adaptation obtained - regular and repeated exposure to maintain tolerance (retention) Gradual introduction of increasing stimulus through the flying syllabus while maintaining regular flying time. Airsickness 2009 Airsickness - VSA 2009 Treatment October 2009 ■ Environment – Fresh air vents, oxygen ■ Desensitisation – specialist course ■ involving the regular exposure to provocative stimuli on a regular and increasing basis over a set period ■ psycho-education ■ Pharmacological 12

Treatment Environment – Fresh air vents, oxygen - neither has demonstrated efficacy but anecdotally worth trying (there are reflex effects from cooling the skin of the face that may having an effect), as well as decrease any odours etc.

Desensitisation - specialist course involving the regular exposure to provocative stimuli either low frequency or cross coupled rotational stimulus (Corialis) on a regular and increasing basis over a set period (eg twice daily for three weeks). Associated psycho-educational aspects such as reassurance of normality, feedback on increasing tolerance, biofeedback and other relaxation techniques. Currently run by the RAAF Edinburgh for service personnel "A motion sickness desensitisation program has been very successful, allowing students to adapt to the motion environment before being returned to flying to continue their training. About six students a year take part in this program that begins with controlled exposure to rotation, acceleration and deceleration and culminates in six sorties in a PC-9.”

Pharmacological - The most widely used method, but limited by side effects, with no ideal answer. They are used b the RAAF for early training to allow students to gain adaptation (up to eight flights, not for solo use), but if not effective referred for desensitisation.

Others Studies in adults using acupuncture wristbands, which activate the P6 Neiguan acupuncture point (5 cm above the wrist), show relief of nausea in and after chemotherapy, but evidence for efficacy in motion sickness is contradictory. There are no studies in children, although wristbands are marketed for this age group Airsickness 2009 Airsickness - VSA 2009 Pharmacological Treatments October 2009 ■ – effective – dry mouth, blurring, interferes with performance ■ Antihistamines – less effective, less blurring and dry mouth – sedative ■ Ginger – safe – no proven efficacy ■ Scopolamine/Dexamphetamine – mitigates sides effects – not readily available, psychomotor impairment ■ Others

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Pharmacological Treatments Medication – Anticholinergics - Scop (Scopolamine or hyoscine) most effective, decrease 10% incidence to 2%, (50% to 8%) but there is an associated decrease in performance for tasks involving continuous concentration and memory storage.. Can cause interference to accommodation (blurring) and dry mouth. Interfere with adaptation. Can be used topically (patch). Not currently available in Australia, is advertised on the web at $US80 for four patches, including consultation and prescription! Main problem is unreliable adsorption, and takes 12 hours to reach stable blood levels. Lasts three days. Orally hyoscine available in Australia (Kwells) OTC, dose 0.3-0.6mg. Antihistamines - Promethzine is used (Phenergan of Avomine), less effective, more sedative, less problems with dry mouth or accommodation. Ginger - probably fairly benign, but of unproven efficacy (chew on a piece of raw ginger, or ginger tea) Scopolamine-Dexamphetamine - Dexamphetamine has been shown to both increase the efficacy of oral scopolamine as well as mitigate it sedative side effects (but not anticholinergic effects). Has been trialed with aircrew and no decrease in psychomotor S/E. Unfortunately S8 and only approved for treatment in ADD or narcolepsy. Pseudoephedrine has similar though less effect but is approved for use by aircrew in Australia. (Cochrane) Similar studies on service helicopter passengers (Black Hawk) have shown efficacy of caffeine 200mg/ 25mg. The former available OTC as NoDoz. The latter is not permitted for aircrew due sedation. (Cochrane) Phenytoin - a commonly used anticonvulsant has been demonstrated to be effective, but this hasn't been extensively explored.

Cinnarizine (Stugeron) and its derivative flunarizine are piperazine antihistamines with vasodilating actions of calcium channel blockers. The only study of anti-motion sickness drugs specifically in children was in an open study with . It was rated by participants (n=79, mean age 8.4 years) to be effective in preventing car sickness, with a low level of adverse effects Airsickness 2009 Airsickness - VSA 2009 References October 2009 ■ Ernsting’s Aviation Medicine ■ Aviation Medicine and other Human Factors for Pilots ■ Aviation Medicine - John Mills ■ AvMedia Vol 22 November 1998 Motion Sickness - David G. Newman ■ http://en.wikipedia.org/wiki/ ■ www.defence.gov.au/news/raafnews ■ http://www.britannica.com/ ■ Medical Physiology - Guytons

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References Ernsting’s Aviation Medicine Aviation Medicine and other Human Factors for Pilots Aviation Medicine - John Mills AvMedia Vol 22 November 1998 Motion Sickness - David G. Newman http://en.wikipedia.org/wiki/ www.defence.gov.au/news/raafnews http://www.britannica.com/ Medical Physiology - Guytons