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Home , Dysbarism, Saturation diving, Snuba, Work of breathing

UNDERSEA Session F Diving Performance and Medicine

F 1 Test of cross corrections for altitude air/ diving at 8,000, 10,000 and 12,000 feet Beck T, Weis T, Natoli M, Brown G, Gatrell A, Schinazi E, Walker A, Armstrong J, Howle L, Pieper C, Moon R Duke University Medical Center, Durham, North Carolina Submitting Author: Timothy Beck [email protected]

Introduction / Background: This study tested United States Navy procedures (Cross corrections: Bell RL, Borgwardt RE. Undersea Biomed Res 1976; 3:1-23) for adjusting procedures during air and enriched O2 diving at altitude.

Materials and Methods: After IRB approval and informed consent, three exposures were performed: (A) 60-fsw no-stop air dives for 30 minutes at 8,000 and 10,000 feet of altitude; (B) 100-fsw dives 35% O2/N2 for 25 minutes at 10,000 feet and 20 minutes at 12,000 feet. Volunteer subjects ages 18-45 years were exposed to simulated altitude in a hypobaric chamber for 24 hours (8,000 feet) or 48 hours (10,000 and 12,000 feet). They then performed a single dive fully submersed while exercising moderately on an electrically braked ergometer. Following each dive the subjects were monitored for 12 hours at altitude for DCS symptoms and VGE using 2D echocardiography. After return to sea level they underwent a complete neurological exam with telephone follow-up the next day.

Results: A total of 42 subjects have been studied (M/F=23/19, Caucasian=34, Asian=3, Hispanic=3, mixed race=2). Dives are summarized in the table.

Summary / Conclusion: Preliminary results are consistent with adequacy of Cross corrections for these no-stop dives at 8,000-12,000 feet in altitude.

Supported by NAVSEA Contract N0002418C4318

F 2 Initial evaluation of the efficacy of the O’Connor Tweezer Dexterity test as a metric of high nervous syndrome Murphy FG U.S. Navy Experimental Diving Unit, Panama City Florida; Department of Mechanical Engineering and Material Science, Duke University, Durham, NC Submitting Author: F. Gregory Murphy, PhD [email protected]

Introduction / Background: Saturation dives consist of a long, slow descent to storage depth followed by a hold during which work is performed. The slow descent was selected for its efficacy in preventing high pressure nervous syndrome (HPNS). HPNS is characterized by disorientation, nausea, dizziness, hand and arm tremors, microsleep, and convulsions. In past studies the Purdue Pegboard, Bennett Ball Bearing (BBB) Test, and electroencephalogram have all been used to detect HPNS. The U.S. Navy Experimental Diving Unit conducted an experimental saturation dive during which divers were compressed at an atypically fast rate to 450 fsw. Due to the rapid compression rate HPNS was a concern; however, the BBB test and an electroencephalogram were not readily available.

Materials and Methods: Six divers underwent compression to 40 fsw on air at 40 fsw/minute. Following a brief stop for chamber system checks they continued compression to 450 fsw on at 40 fsw/minute. These six divers breathed from a constant 0.7 atm PO2 breathing source with 82% He/12% N2/6% O2 during compression and for 40 minutes after compression until a safe breathable atmosphere had been established in the chambers. The O’Connor Tweezer Dexterity (OTD) test is a well-documented test for manual dexterity similar to the BBB test. Divers were tested for HPNS with the Purdue Pegboard and OTD test, 50 minutes, 160 minutes, and the following morning post compression.

Results: One out of six divers showed a measurable performance decrement, taking 4.28 minutes longer to complete the OTD test than their average pre-dive completion time. described tremors as starting just below the elbow and extending through the wrist. The diver also reported mild dizziness. All signs and symptoms had resolved the following morning.

Summary / Conclusion: The OTD test is a suitable replacement for the BBB test to detect intentional tremors associated with HPNS.

F 3 Characteristics of a cohort of older recreational divers with or without arrhythmias Buzzacott P1,2, Anderson G1,3, Tillmans F1, Grier J4, Denoble PJ1 1 , Durham, North Carolina 2 Prehospital, Resuscitation and Emergency Care Research Unit, School of Nursing, Midwifery and Paramedicine, Curtin University, Western Australia 3 The Warren Alpert School of Medicine at Brown University, Providence, Rhode Island 4 Biological Sciences, Dept., North Dakota State University, Fargo, North Dakpta Submitting Author: Peter Denoble, MD [email protected]

Introduction / Background: Sudden cardiac death (SCD) accounts for 20-30% of all scuba fatalities. One suspected mechanism of SCD is acute arrhythmia triggering cardiac arrest. This study describes the prevalence of factors that may predispose divers to SCD.

Materials and Methods: Sixty-eight certified scuba divers made 75 dive research trips and logged ≥920 dives. Diver characteristics, medical history and diving history were reported at enrolment. Before and after dive trips, 12-lead ECG recording and echocardiographic measurements were collected. Arrhythmias were identified and categorized by type.

Results: No diver suffered SCD during this study. Compared to divers without any arrhythmias (n=48), those with arrhythmias recorded either pre- or post- diving (n=20) were 17% older (59 vs. 50 years), had been diving longer (20 vs. 10 years), but had made fewer dives in the previous six months (15 vs. 20). Their left ventricular mass wa s greater (176 vs. 153g) and was greater when indexed to body surface area (179 vs. 161g). Their relative wall thickness was 11% greater (0.48 vs. 0.43cm), and interventricular septum thickness was 8% greater (1.05 vs. 0.97cm). There were no meaningful differences between divers with arrhythmias compared to those without in the proportion who were past smokers, who were currently taking any prescription meds, or who had left ventricular hypertrophy. The arrhythmia group had a higher proportion of alcohol drinkers (92% vs. 82%), higher frequency of cholesterol diagnosis (38% vs. 22%), and more were taking cholesterol medications (32% vs. 16%). The incidence of arrhythmias changed between pre- and post- diving in 18/20 divers.

Summary / Conclusion: Further studies of a more controlled, less exploratory, nature are warranted. We have developed and refined the protocols that could support such studies. This study, for the first time, characterizes a selected cohort of older recreational divers with cardiac arrhythmias, though this cohort may not be representative of older recreational divers generally.

F 4 signatures in closed-circuit divers Kutz C, Carlile M, Brett K, Cespedes E, Powell F, Witucki P, Sadler R, Sadler C, Popa D Department of , Division of ; University of California - San Diego Health,San Diego, California Submitting Author: Craig J. Kutz, MD [email protected]

Introduction / Background: Closed-circuit rebreather (CCR) diving has increased due to availability and advantages over scuba. Malfunctions or user error in CCR can lead to dangerous gradual hypoxia as a diver consumes available within the circuit. Hypoxia can cause underwater loss of consciousness, aspiration, , and death. Studies of hypoxia in CCR divers are limited, and the question remains as to whether hypoxia training improves the ability to self-rescue. We hypothesize that CCR divers exhibit an individualized and reproducible constellation of symptoms from a gradual onset hypoxic exposure (“hypoxic signature”). Further, we hypothesize that by learning their hypoxic signature, divers will improve hypoxia recognition and self-rescue.

Materials and Methods: We performed a single-blinded, cross-sectional study investigating 20 male and female divers certified in either CCR (n=8) or scuba (n=12). Subjects underwent a CCR oxygen malfunction with gradual onset hypoxia while simulating swimming on a cycle ergometer. Subjects played a distracting computer game while pointing to symptoms. Subjects underwent an initial known hypoxia trial, then three subsequent blinded (sham vs. hypoxia) trials. We instructed subjects to self-rescue if they perceived hypoxia. If they failed to perceive hypoxia, an alarm to self-rescue occurred at 75% oxygen saturation (hypoxia) or after six minutes (sham).

Results: With randomization, subjects correctly identified the mixture in 52/60 trials (86.6%). Of the incorrect, three subjects incorrectly identified a hypoxic trial as sham; five subjects felt a sham trial was hypoxic. Of the subset who self-aborted, 30% on subsequent hypoxia trials were able to abort without prompting. Subjects undergoing blinded hypoxia identified similar symptoms to their known hypoxia trial in 19/20 trials (95%).

Summary / Conclusion: Our preliminary evidence suggests that with known exposure to hypoxia, divers were able to recognize symptoms and self-rescue in subsequent blinded exposures. With further study, this initial work may reveal improvements in CCR safety through identification of divers’ “hypoxia signature.”

F 4 Closed circuit : FiO2, PO2, ETCO2, and ETO2 during normobaric hypoxic hypoxia exposures Carlile M, Kutz C, Brett K, Moya Cespedes E, Powell F, Witucki P, Sadler R, Sadler S, Popa D, Department of Emergency Medicine, Division of Hyperbaric Medicine; University of California - San Diego Health,San Diego, California Submitting Author: Morgan Carlile, MD [email protected]

Introduction / Background: Closed-circuit rebreather (CCR) diving is the among the most lethal activities in diving per man-hour. CCR diving has steadily increased among military, commercial and recreational applications due to significant efficiency and feasibility advantages in many dive profiles.

Due to intrinsic equipment complexity and multiple potential points of failure, CCR divers suffer 10 times the rate of deaths as compared with open-circuit recreational scuba divers. There has been new interest in using “hypoxia signatures” for potentially training CCR divers to recognize hypoxia and attempt self-rescue. As part of a larger investigation regarding hypoxia signatures among CCR divers, we hypothesize that there is a reproducible relationship seen in FiO2, PO2, ETCO2, and ETO2 observed during hypoxic training experiences.

Materials and Methods: We performed a single-blinded, cross-sectional study investigating 20 male and female divers certified in either CCR (n=8) or scuba (n=12). Subjects underwent a CCR oxygen malfunction with gradual onset hypoxia while simulating swimming on a cycle ergometer. Subjects played a distracting computer game while also pointing to hypoxia symptoms displayed on a board. Subjects underwent an initial known hypoxia trial, then three subsequent blinded (sham vs. hypoxia) trials. We instructed subjects to self-rescue if they perceived hypoxia. If they failed to perceive hypoxia, an alarm to self-rescue occurred at either 75% oxygen saturation (hypoxia) or after six minutes (sham).

Results: In hypoxic studies, the observed FiO2, ETO2, and SpO2 were highly correlated. While the FiO2, ETO2 and SPO2 were correlated linearly, SpO2 had a sigmoid relationship.

Summary / Conclusion: Protocols for hypoxia training in CCR divers can benefit from the knowledge that FiO2 measurements in CCR diving electrogalvanic sensors are directly related to PO2 and ETO2 at the mouthpiece. This study also reinforces the well-known correlation of SpO2 following the oxygen-hemoglobin dissociation curve. This benefits future research by giving insight on how FiO2, ETO2, SpO2, and pO2 are related during CCR “hypoxia signature” training protocols.

F 5 fluctuation during a static muscle contraction and its characteristics in a simulated saturation dive to 45 ATA Iwakawa T Undersea Medical Center, Maritime Self-Defense Force, Japan Ministry of Defense, Yokosuka Submitting Author: Takashi Iwakawa [email protected]

Introduction / Background: Well-trained athletes perform lower force fluctuation in muscle static contraction than non-athletes (Ushiyama 2010). Lower force fluctuation in a muscular contraction contributes to better working performances. In deep , working performances were worse in some reports. This study investigated force fluctuation and its characteristics in a simulated heliox saturation dive to 45 ATA.

Materials and Methods: Seven male professional divers participated in this study. In the pre-dive phase (1 ATA air) and compressed phase (45 ATA heliox), they performed a three-minute static handgrip; its load was 30% maximum voluntary contraction (MVC) force. The handgrip were recorded at 1 kHz and their coefficient of variances (CV) calculated. Frequency domains of the handgrip force fluctuations were analyzed by fast Fourier transform.

Results: CV of handgrip forces in 45 ATA heliox was significantly higher than in 1 ATA air (1.48 ± 0.67% vs. 1.97 ± 0.60%; p0.05). Low frequency (under 1 Hz) power density of handgrip forces in 45 ATA heliox was significantly higher than in 1 ATA air (6.40 ± 7.88 kg2/Hz vs. 10.98 ± 8.48 kg2/Hz; p0.05).

Summary / Conclusion: Higher CV of handgrip forces in 45 ATA heliox suggests lower stability in a muscular contraction in a deep heliox saturation diving. A previous study (Yoshitake 2004) showed that suppressed Ia afferent input reduced force fluctuation and the lower frequency power density of contraction forces. Increased force fluctuations and low frequency power density of of contraction forces in this study would be triggered by facilitated Ia afferent input in hyperbaric condition.

F 6 Improving the visualization of decompression bubbles: Multiplexed ultrasound imaging of different bubble sizes and their evolution over time Le DQ, McCune E, Palakurthi M, Dayton PA, Papadopoulou V Joint Department of Biomedical Engineering/University of North Carolina at Chapel Hill and North Carolina State University Submitting Author: David Q Le [email protected]

Introduction / Background: B-mode ultrasound echocardiography detection of venous gas emboli (VGE) is commonly used as a marker for decompression stress. However, we have previously shown that ultrasound techniques designed for medical microbubble imaging (contrast-enhanced ultrasound or CEUS) are more sensitive to smaller microbubbles by effectively removing both tissue and large bubble signals. In a pilot study on seven divers, cardiac CEUS detected a significant increase in image signal post-dive (before returning to pre-dive levels), both in the venous and arterial cardiac chambers, and even in the absence of detectable VGE on B-mode. Here we investigate how concurrent CEUS and B-mode imaging can be used to create a new composite image to tag decompression bubbles in different colors according to their size, and follow their evolution post-decompression.

Materials and Methods: We generated decompression bubbles of different sizes by introducing air-saturated water pressurized from 220 or 500 kPa to an water-filled column through a 600-µm nozzle. Bubbles were imaged at 42 cm from the nozzle in the column through a microscope objective inserted in the column, as well as simultaneous CEUS and B-mode imaging through an acoustically transparent window on a Siemens Sequoia C512 and 15L8 transducer (7 MHz transmit).

Results: Optically detected microbubble size distributions varied between the two , showing predominantly large bubbles at 220 kPa, and both large (>10µm) and microbubbles 1-3µm at 500 kPa. A multiplexed display scheme was developed where B-mode and CEUS imaging is used to differentiate larger bubbles (cancelled on CEUS) and microbubbles at resonance (seen on CEUS, estimated size 2 µm). These different bubbles are separately color-coded and displayed on a composite frame.

Summary / Conclusion: We believe that such a multiplexed decompression bubble display can become a powerful tool in decompression research, combining anatomical information and bubble sizing information from comparing the B-mode and CEUS concurrently acquired.

F 7 Physiologic factors associated with pulmonary B-lines in scuba divers at the NASA Neutral Lab Sanders R, Ray K, Williams S, Nowitz J NASA Laboratory, Houston, Texas Submitting Author: Robert Sanders, MD [email protected]

Introduction / Background: Immersion pulmonary edema (IPE) is a potentially life-threatening phenomenon that occurs in . Although there is much speculation on what causes IPE, the pathophysiology remains relatively unknown. A study completed at NASA’s Neutral Buoyancy Laboratory (NBL) has attempted to answer these questions.

Materials and Methods: Twenty-nine divers at NASA’s NBL were evaluated for the presence of pulmonary B-lines pre- and post-dive using chest ultrasonography at 12 intercostal points. Additional parameters including blood pressure, pulse, chest X-ray results, pulmonary functions, and smoking status were collected.

Results: There were a total of 67 dive exposures. Thirty-eight (57%) had an increase of one or more B-lines post-dive (Fisher’s exact test: OR 7.79 (2.43-29.1); p=0.001). Nine female exposures (64%) and 29 male exposures (54%) were positive for B-lines post-dive, suggesting no difference across genders (Fisher’s exact test: OR 1.48 (0.38-6.42); p=0.5613). All divers were asymptomatic, and no cases of IPE were diagnosed. With regard to the additional health parameters collected, BMI, pulse, and blood pressure were not statistically significant among B-lines versus no B- lines exposures (p=0.643, p=0.344, p=0.299). Although smoking status (current, prior, never) was not statistically significant when looking at individual exposures (p=0.998), all divers who were current smokers had one or more exposures that were positive for B-lines.

Summary / Conclusion: Although IPE is considered a rare event in scuba diving, pulmonary B-lines are a common process seen in this population. From our results, B-lines are likely a normal physiologic process occurring in those with normal vital signs. In addition, current smoking may put divers at an increased risk of acquiring pulmonary B- lines, but more data needs to be collected.

F 8 Investigating critical flicker fusion frequency for monitoring gas narcosis in divers Vrijdag XC1,2, van Waart H1, Sleigh JW1,3, Balestra C4, Mitchell SJ1,5 1 Department of Anaesthesiology, University of Auckland, Auckland, New Zealand 2 Deep Dive Dubai, Dubai, United Arab Emirates 3 Department of Anaesthesia, Waikato Hospital, Hamilton, New Zealand 4 Environmental, Occupational & Ageing (Integrative) Laboratory, Haute Ecole Bruxelles-Brabant (HE2B), Brussels, Belgium 5 Department of Anaesthesia, Auckland City Hospital, Auckland, New Zealand Submitting Author: Xavier CE Vrijdag [email protected]

Introduction / Background: Critical flicker fusion frequency (CFFF) has been used in various studies to measure the cognitive effects of gas mixtures at depth, sometimes with conflicting or apparently paradoxical results. This study aimed to evaluate a novel automatic CFFF method and investigate whether CFFF can be used to monitor gas- induced narcosis in divers.

Materials and Methods: Three hyperbaric experiments were performed: 1) automated and manual CFFF measurements during air breathing at 608 kPa; 2) manual CFFF measurements during air and heliox breathing at surface and 608kPa; 3) manual CFFF measurements during oxygen breathing at surface, 142 and 284 kPa. All results were compared to breathing air at the surface.

Results: Only breathing oxygen at the surface and 284 kPa caused a significant decrease in CFFF of respectively 2.5% and 2.6% compared to breathing air on the surface. None of the other conditions showed a difference compared to surface air breathing.

Summary / Conclusion: CFFF did not change in our experiments while breathing air at 608 kPa compared to air breathing at the surface using both devices. Based on our results CFFF does not seem to be a sensitive tool for measuring gas narcosis in divers in our laboratory setting.

F 9 Symptomatic during a recreational dive and the use of hyperbaricoxygen : A case report Price SM, Price WD, Johnston M USS Frank Cable AS-40, Unit100105, FPO AP 96657 Submitting Author: Stephanie Price, MD [email protected]

Introduction / Background: Pulmonary overinflation syndrome (POIS) refers to the spectrum of injuries that result from pulmonary . The injuries vary from benign to severe and are directly related to where in the tissue the expanding air escapes resulting in arterial gas embolism (AGE), pneumomediastinum or . Pneumomediastinum is a part of the POIS spectrum and can result in respiratory symptoms.

Methods/Materials: A 32-year-old male made a dive to 80 feet of (fsw) for 50 minutes on open-circuit air with a bottom time of 12 minutes. At the end of the dive, he began to experience chest tightness within 10 feet of reaching the surface. On the surface he had dyspnea, facial swelling, and voice changes. In the emergency room he was started on 100% ground-level oxygen (GLO). His vital signs were significant for a respiratory rate (RR) of 30. He was otherwise hemodynamically stable. After 60 minutes of treatment with GLO, his RR had not decreased, and he remained dyspneic. Chest X-rays showed pneumomediastinum and with no pneumothorax.

Results: Given the minimal alleviation of symptoms with supplemental oxygen and no contraindication to hyperbaric oxygen, the decision was made to treat him in the hyperbaric chamber located nearby. The treatment profile was 10 feet for one hour on 100% oxygen, which is in accordance with the U.S. Navy Dive Manual for severe pneumomediastinum without pneumothorax. Ten minutes into the HBO2 treatment his dyspnea resolved and respiratory rate normalized.

Summary/Conclusion: In this case HBO2 was utilized to treat a POIS injury without pneumothorax or AGE with rapid symptomatic improvement. Questions of resource cost, availability, the presence of pneumothorax and symptom severity should be considered when determining whether HBO2 is a good option for a patient with isolated symptomatic pneumo- mediastinum.

F 10 Practical and physiological considerations about the work of the breathing loop in OC regulators Angelini S SpA, Rapallo, Italy Submitting Author: Sergio Angelini, PhD [email protected]

Introduction / Background: The (WOB) loop of open-circuit scuba diving regulators is often being used by manufacturers as a marketing tool to entice customers into buying their products. This is often misleading, as a single number does not define the performance of a regulator in its entirety, just as top speed or a 0 - 60-mph acceleration does not fully define a vehicle. In this poster we describe the work of breathing loop and interpret the results from a variety of high-performance regulators.

Materials and Methods: Six high-performance regulators from three brands were tested using an ANSTI machine with a 200-meter depth rating at three different breathing rates (15, 30 and 62.5 L/minute) and depths ranging from 20 to 200 meters, using air. In addition, a 200-meter test at 62.5 L/minute using helio 3/97 was carried out. On regulator was tested in its two settings: “performance” and “comfort.“

Results: Results are shown in the tables. We place particular emphasis on the work of breathing, as is mostly passive, taking advantage of energy stored in the muscles during inhalation. When transforming the J/l data into W (power), at EN250 conditions (50 m @62.5 L/min) the values range between 0.06 and 0.65 W. At recreational conditions (30 m @15 L/min) the spread of results narrows to between 0.15 and 0.2 W.

Summary / Conclusion: Quantifying the work of breathing in absolute terms shows that even the calmest of regulators requires only about 0.5 W of power for inhalation, making it an irrelevant discussion. The flip side is that regulators providing very low WOB may have too much positive pressure during inhalation, which for some people is reflected in negative breathing comfort. Judging a regulator solely by its WOB at EN250 conditions can thus lead to an unsatisfactory diver experience.

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F 11 Dermatitis herpetiformis in a Naval diver: Dapsone as a safe treatment option? Price SM, Price WD USS Frank Cable AS-40, Unit 100105, FPO AP 96657 Submitting Author: Stephanie Price, MD [email protected]

Introduction / Background: Methemoglobinemia can cause cyanosis, respiratory distress and death. Dapsone is the primary treatment option for dermatitis herpetiformis (DH) and is one of the most common acquired causes of methemoglobinemia. We consider the case of a Navy diver who developed DH and the unique concerns posed with dapsone treatment in divers.

Methods/Materials: A 42-year-old male USN diver developed pruritic vesicles, predominately clustered on his arms and legs. Serum studies were positive for endomysial IgA and duodenal biopsies confirmed chronic duodenitis. Dapsone is the primary method for treating DH. Given the adverse drug profile in the setting of his dive status we first attempted control of symptoms with topical hydrocortisone cream. The patient is now five months post diagnosis and is entirely controlled with diet alone.

Results: Increased oxidative stress and hemolytic anemia are the two primary side effects of dapsone which can act synergistically to hasten the development of methemoglobinemia. The case literature of dapsone use and acquired methemoglobinemia is significant. The majority of the cases were not baseline healthy individuals. They had elevated levels of oxidative stress in their body due to chronic disease which increased susceptibility to the side effects of dapsone. Diving physiology is unique, and while ultimately the studies are mixed there is good evidence that the hyperbaric conditions associated with diving increase oxidative stress in the body. Given this, it could be argued there is increased risk inherent to diving for the development of methemoglobinemia in individuals taking dapsone.

Summary/Conclusion: No definitive guidelines exist for what medications are safe to take while diving. This case report combines the case literature with the known metabolic pathway of a drug and applies it to the physiological effects of diving to help assist clinical judgment when considering prescribing dapsone in divers.

F 12 Implementing the web-based crowdsourcing of venous gas emboli spatio-temporal locations in post-dive echocardiography Smolka MJ, Le DQ, Barrentine B, Edelson C, Germonpré P, Balestra C, Tillmans T, Buzzacott P, Freiberger JJ, Moon RE, Denoble PJ, Dayton PA, Papadopoulou V Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, North Carolina Submitting Author: Martin Smolka [email protected]

Introduction / Background: We have previously shown that a graphical user interface (GUI) can save time in manually counting venous gas emboli (VGE) on post-dive echocardiography, as well as provide spatiotemporally labeled data to be used for full computer automation of this task (Barrentine, et al., UHMS 2019; Le, et al., UHMS 2019). [ INCOMPLETE REFERENCES ] Our previous GUI was developed in MatLab and would require volunteers to download the program and set it up in their computer environment. Here we investigate if we can transition all of the GUI functionality, including new rater training and validation, to a fully web-based application to allow for easier and wider sharing for crowdsourcing purposes.

Materials and Methods: A website was built using the Angular 8 Javascript framework and served by the Firebase serverless backend platform. Users will be able to register using an email address, and different levels of user permissions determine what is shown to each individual. De-identified, previously acquired, post-dive echocardiography videos are played using the HTML 5 web player. Users are trained, and their ability to perform VGE counts is validated using the same methods as described in our previous work.

Results: Initial testing indicates that users are able to identify VGE in the web-based application, with an average time per video of three minutes (compared to longer than eight minutes manually without a GUI).

Summary / Conclusion: We have demonstrated that it is possible to move this application to the web, which will provide a mechanism to better share this tool with volunteers and collaborators. We are moving forward with this website to further test its crowdsourcing capability. Eventually, crowdsourced bubble locations will be used to fully automate VGE counting.

F 13 Health status of active U.S. scuba divers 2011-2017 Jooste J1, Buzzacott P2 1 Prehospital, Resuscitation and Emergency Care Research Unit, School of Nursing, Midwifery and Paramedicine, Faculty of Health Sciences, Curtin University, Perth, Western Australia 2 Department of Physics at Indiana University, Bloomington, Indiana Submitting Author: Peter Buzzacott, PhD [email protected]

Introduction / Background: The Behavioural Risk Factor Surveillance System (BRFSS) was established in 1984 and collects health and physical activity data from more than 450,000 adults annually, in all U.S. states and territories. In 2011, 2013, 2015 and 2017 participants named two activities they were most active at during the previous month. This study describes the active scuba divers.

Materials and Methods: Iterative raking on 16 variables with trimming of outliers generated person-level to reflect Nielsen Company intercensal population estimates. Proportional weighting enabled the four years of data to be combined.

Results: An estimated 11,545 person-years of data by an estimated 138,544 scuba divers (n=117,230 males, 85%, n=21,314 females, 15%), reported a median of either two dives per week or three dives total during the previous month; 47% were aged 45 years, 36% aged 45-59 and 17% were aged ≥60. Body mass index classification was overweight for 44%, and 21% were obese. 62% rated their general health excellent/very good and another 32% good. However, 28% reported a total 975 person-years of physical injury or illness within their previous 30 days. Having ever been diagnosed with high blood pressure was reported by 20%, and high cholesterol by 29%. Having smoked at least 100 cigarettes ever was reported by 52% of the divers, but 63% of those had not smoked for ≥5 years. During the previous 30 days, 22% reported drinking alcohol ≤5 days per week, 19% drank alcohol ≤10 days in total, and another 30% reported having not drunk alcohol at all.

Summary / Conclusion: The BRFSS is a rich source of data regarding the health and demography of active U.S. scuba diving adults. Identification of new health issues and advancing age are common triggers by most for regular health screening. Linking diving evaluations to those active divers already seeing their may prove beneficial in preventing dive-related morbidity/mortality.

F 14 Flu-season knows no bounds: A case study of an influenza-like outbreak during a saturation dive Muller I Navy Experimental Diving Unit, Panama City Beach, Florida Submitting Author: Imelda Muller, MD [email protected]

Introduction / Background: Influenza A and B present clinically with acute upper and/or lower respiratory tract symptoms. Systemic manifestations vary and include headache, myalgia, fever and fatigue. An outbreak of influenza or influenza-like illness during a saturation dive requires special considerations to limit transmission, ameliorate symptoms, and mitigate complications associated with acute illness and decompression.

Case Report: Eight healthy divers between the ages of 29 and 41 years-old underwent an eight-day N2O2 dry saturation dive. Twenty-four hours into the dive, one diver presented with subjective fever, chills, congestion, cough, fatigue and myalgias concerning for influenza. He was treated with oseltamivir, an antiviral medication that targets influenza A and B, and demonstrated clinical improvement over the next two days. Over the ensuing 72 hours, three other divers developed similar symptoms and were also treated with oseltamivir. Three of the four remaining divers were started on a prophylactic regimen of oseltamivir and remained asymptomatic. One diver with a recent history of a flu-like illness declined prophylactic oseltamivir and did not develop symptoms concerning for influenza. Increased hygiene precautions were enforced in an effort to limit transmission and the dive was aborted, initiating standard saturation decompression one day early. The divers did not experience significant complications during decompression or side effects from oseltamivir.

Summary / Conclusion: A saturation diving environment is an austere often isolated from surface medical support by days of decompression. Close living quarters, recycled air, and sanitation constraints pose critical challenges to preventing communicability of illnesses. When considering medication management of acute illnesses, the safety, efficacy, and pharmacologic properties of each agent must be carefully weighed against the risks associated with side effects experienced at depth and the potential for these side effects to mask or mimic diving-related injuries. This case study highlights the challenges and considerations of an influenza-like outbreak during a saturation dive.

F 15 Drowning in broken hearts: A case series of immersion pulmonary edema-induced Takotsubo’s cardiomyopathy Derksen B1,2, Tanaka L1,2, Snyder B1,2, Sadler C1,2 1 Division of Hyperbaric Medicine 2 Department of Emergency Medicine, University of California San Diego, San Diego, California Submitting Author: Brenna Derksen, MD [email protected]

Introduction / Background: Immersion pulmonary edema (IPE) and Takotsubo cardiomyopathy (TC) are two rare and reversible disorders that present with sudden onset and severe cardiopulmonary symptoms. Although IPE’s association with diving is widely accepted, it has only rarely been associated with reversible cardiomyopathies. We propose that IPE triggers a profound physiologic and emotional stress response, placing affected divers at risk for the development of stress-induced cardiomyopathy.

Materials and Methods: We present a case series of two patients who presented with IPE and TC after diving.

Results: • Case 1: 64-year-old female presented with IPE after scuba diving. She then developed chest pain with elevation in cardiac markers and echocardiogram showing apical hypokinesis and dilated left ventricle consistent with TC. Cardiac catheterization revealed no significant coronary artery disease (CAD). She later revealed multiple prior episodes of shortness of breath during cold-water dives, suggesting a history of recurrent IPE. • Case 2: 59-year-old female presented with IPE after (surface-supplied) dive. She was transferred to UCSD and was noted to also have ECG changes and elevated troponins. Echocardiogram and cardiac catheterization showed reduced ejection fraction, apical hypokinesis, and no significant CAD, consistent with TC.

Summary / Conclusion: TC closely mimics acute coronary syndrome and can present with ECG changes, elevated cardiac markers, arrhythmias, or heart failure. Findings of TC include apical ballooning of the heart on echocardiogram and the absence of CAD. Symptoms are classically triggered by emotional or physical stress. IPE impairs and leads to respiratory dysfunction and may result in profound physiologic and emotional stress. TC has been hypothesized to be the result of acute catecholamine surge, as occurs in IPE. Based on our two cases and prior publications we propose that IPE may be an under-recognized trigger for TC in divers.

F 16 An Update on pulmonary edema in special operations assessments: A look inside U.S. Air Force Special Warfare Tanaka HL1, Tilton P2, Arnold W2, Wightman JM3, Ott M4 1 Division of Hyperbaric Medicine, Dept of Emergency Medicine, University of California, San Diego 2 Special Tactics Training Squadron, Air Force Special Operations Command, USAF 3 Dept of Military and Emergency Medicine, Uniformed Services University of the Health Sciences 4 Dept of Pulmonary and Critical Care, Eglin Hospital, Eglin Air Force Base, USAF Submitting Author: Hideaki Leo Tanaka, MD [email protected]

Introduction / Background: The United States Air Force assesses hundreds of candidates annually for selection into Air Force Special Warfare assignments. Assessment processes are created to identify potential trainees, and a key portion of evaluation revolves around pool work (underwater swimming, drown-proofing, , etc.) as it exposes applicants to intrinsic stress. Swimming-induced pulmonary edema and immersion pulmonary edema are recognized risks, along with negative pressure pulmonary edema due to and breath-holding activities. What distinguishes these cases versus those in civilian activities/athletics are that all participants are rigorously medically screened; all are fit, healthy, and without major comorbidities. This population provides the greatest insight into pulmonary edema without confounders.

Methods: This case series was reported previously in abstract form after a period spanning three years; it has been extended another year and now involves 12 healthy individuals who developed pulmonary edema during the pool phase of special operations assessments, their resultant clinical evaluation, care, and follow-up.

Results: All 12 individuals were diagnosed with pulmonary edema in varying severity; most were hospitalized and all survived. None have had permanent sequelae.

Summary: In our experience, pulmonary edema in special operations assessments is a known risk associated with pool exercises. It is mitigated by having physicians, advanced practice providers, and paramedics present on deck at all pool phases, with ability to intervene when candidates display symptoms of hypoxia and/or hemoptysis. Pulmonary edema in our assessments is related to exertion, vigorous pre-event hydration, cold exposure, submersion, breath- holding, and snorkel-breathing. Most also present with concomitant rhabdomyolysis and acute kidney injury, complicating treatment options. Historically, previous cases have been misidentified as aspiration and near-drowning. Increased awareness enables medical personnel to correctly identify cases and avoid morbidity and mortality. Non- cardiogenic pulmonary edema is a physiological response to stress and does not appear to have genetic predisposition or increased risk of recurrence.

Standard Disclaimer: The opinions and assertions expressed herein are those of the authors and do not necessarily reflect the official policy or position of the Uniformed Services University, the Department of the U.S. Air Force, or the U.S. Departmen t of Defense.

F 17 Preliminary data of ultrasonic monitoring of decompression protocols in high-pressure compressed-air work in tunnels built with TBM Subbotina N1, Castro J2, De Ferraris F2, Martin M1, Frydman JD1, Correa L1, Uriona D1 1 Fisiocorp SA, Buenos Aires, Argentina 2 San Isidro Cardiovascular Institute, Buenos Aires Submitting Author: Nina Subbotina, PhD [email protected]

Introduction / Background: In countries without statutory limits on hyperbaric exposure the assessment of the decompression regimes should contain post-decompression physiological monitoring of workers. Available techniques – besides vital signs registry and medical observation – include Doppler monitoring and ultrasonic scanning.

Materials and Methods: The pressure of compressed-air exposures ranged between 3.3 and 3.9 bar gauge. Three real working shifts, each one with three participants, were monitored, obtaining nine records. In addition, Doppler data were obtained from 11 workers after remaining at rest under pressure of 3.9 bar for 45 minutes of bottom time. Ultrasonic monitoring started five minutes after the decompression and continued up to an hour. Doppler scores using the Kisman-Masurel (KM) code were recorded in the precordial and subclavian zone. Portable echograph Mindray M7 and General Electric Vivid S5 were used.

Results: Doppler maximum scores (KM III) were observed twice in the same person, after performing real work at 35 meters’ depth with no complaints and no clinical manifestations of dysbaric stress. The third case of high levels of bubble score was observed in one worker after remaining in hyperbaric chamber at rest at 39 meters. Three of the total 21 Doppler monitoring sessions (15%) demonstrated a grade III KM venous blood bubble level (see table).

Summary / Conclusion: The average values of the amount of venous blood bubbles were low and could characterize the applied decompression regimes as acceptable.

Recommendations: It is recommended to continue measurements of the amount of venous blood bubbles in compressed-air workers after the decompression process as part of physiological controls of decompression regime and for better understanding of these phenomena.

F 18 Medical monitoring of compressed-air workers in tunneling during hyperbaric interventions in the head of the tunnel boring machine Subbotina N1, Altamirano C2, Boullon F2, Uriona D1 1 Fisiocorp SA, Buenos Aires, Argentina 2 CCMI Consortium Ghella, Buenos Aires, Argentina Submitting Author: Nina Subbotina, PhD [email protected]

Introduction / Background: The medical monitoring of tunnel workers during hyperbaric interventions is adopted as a technique for health care and decompression regimes assessment in real time.

Materials and Methods: Before hyperbaric intervention, drugs and alcohol were screened in saliva and exhaled air; vital signs (BP, HR), cognitive and disposition assessment were carried out before and after work in compressed air. Working pressure ranged from 0.9 bar gauge (1.9 ATA) to 3.4 bar gauge (4.4 ATA). The 24 workers were selected and trained; three persons at a time were put under pressure. In total, 186 records from 59 interventions were collected. The bottom time varied between 0:30 and 7:45 hours. Each worker’s behavior, movements, gait and other pertinent details after returning to the surface were objects of the ’s observations to discharge or to rule out .

Results: Traces of drugs and alcohol were found in two cases, leading to the exclusion of affected personnel from work in a high-pressure environment. Three workers were considered not fit temporarily because of high BP, upper airway congestion, etc.; after treatment they joined the working team. Vital signs showed the changes enumerated in the table.

BP was slightly reduced, HR increased, keeping all parameters within normal limits; there was practically no cognitive change, disposition staying positive. One case of bends was observed and successfully treated.

Summary / Conclusion: Consequently, the selection and training of personnel for the compressed air environment and decompression protocols were appropriate for TBM cutting head maintenance.

End Session F