INTRODUCTION: Ambulation during extravehicular activity on Mars may increase the risk of decompression sickness through enhanced bubble formation in the lower body. Hypotheses: walking effort (ambulation) before an exercise-enhanced denitrogenation (prebreathe) protocol at 14.7 psia does not increase the incidence of venous gas emboli (VGE) at 4.3 psia, but does increase incidence if performed after tissues become supersaturated with nitrogen at 4.3 psia.METHODS: VGE results from 45 control subjects who performed exercise prebreathe without ambulation before or during a 4-h exposure to 4.3 psia were compared to 21 subjects who performed the same prebreathe but ambulated before and during the hypobaric exposure (Group I) and to 41 subjects who only ambulated before the hypobaric exposure (Group II). Monitoring for VGE in the pulmonary artery was for 4 min at about 12-min intervals using precordial Doppler ultrasound (2.5 mHz). Detected VGE were assigned a categorical grade from I to IV. The detection of Grade III or IV was classified as “high VGE grade.”RESULTS: The incidence of high VGE grade for Group I (57%) was greater than the control (17%) and Group II (15%). The incidence of pain-only decompression sickness was greater for Group I (20%) than the control (0%) and Group II (5%).CONCLUSIONS: High-grade VGE are increased by mild ambulation conducted under a supersaturated state (Group I vs. II); however, no increase was observed with mild ambulation during the saturated state alone (control vs. Group II).Conkin J, Pollock NW, Natoli MJ, Martina SD, Wessell JH III, Gernhardt ML. Venous gas emboli and ambulation at 4.3 psia. Aerosp Med Hum Perform. 2017; 88(4):370–376.

BACKGROUND: Cartilage tissue engineering is a growing field due to the lack of regenerative capacity of native tissue. The use of bioreactors for cartilage tissue engineering is common, but the results are controversial. Some studies suggest that microgravity bioreactors are ideal for chondrogenesis, while others show that mimicking hydrostatic pressure is crucial for cartilage formation. A parallel study comparing the effects of loading and unloading on chondrogenesis has not been performed.METHODS: The goal of this study was to evaluate chondrogenesis of human adipose-derived stem cells (hASC) under two different mechanical stimuli relative to static culture: microgravity and cyclic hydrostatic pressure (CHP). Pellets of hASC were cultured for 14 d under simulated microgravity using a rotating wall vessel bioreactor or under CHP (7.5 MPa, 1 Hz, 4 h · d⁻¹) using a hydrostatic pressure vessel.RESULTS: We found that CHP increased mRNA expression of Aggrecan, Sox9, and Collagen II, caused a threefold increase in sulfated glycosaminoglycan production, and resulted in stronger vimentin staining intensity and organization relative to microgravity. In addition, Wnt-signaling patterns were altered in a manner that suggests that simulated microgravity decreases chondrogenic differentiation when compared to CHP.DISCUSSION: Our goal was to compare chondrogenic differentiation of hASC using a microgravity bioreactor and a hydrostatic pressure vessel, two commonly used bioreactors in cartilage tissue engineering. Our results indicate that CHP promotes hASC chondrogenesis and that microgravity may inhibit hASC chondrogenesis. Our findings further suggest that cartilage formation and regeneration might be compromised in space due to the lack of mechanical loading.Mellor LF, Steward AJ, Nordberg RC, Taylor MA, Loboa EG. Comparison of simulated microgravity and hydrostatic pressure for chondrogenesis of hASC. Aerosp Med Hum Perform. 2017; 88(4):377–384.

INTRODUCTION: Disabled submarine (DISSUB) survivors may face elevated CO₂ levels and inert gas saturation, putting them at risk for CO₂ toxicity and decompression sickness (DCS). Propranolol was shown to reduce CO₂ production in an experimental DISSUB model in humans but its effects on DCS in a DISSUB rescue scenario are unknown. A 100% oxygen prebreathe (OPB) reduces DCS incidence and severity and is incorporated into some DISSUB rescue protocols. We used a swine model of DISSUB rescue to study the effect of propranolol on DCS incidence and mortality with and without an OPB.METHODS: In Experiment 1, male Yorkshire Swine (70 kg) were pressurized to 2.8 ATA for 22 h. Propranolol 1.0 mg · kg⁻¹ (IV) was administered at 21.25 h. At 22 h, the animal was rapidly decompressed and observed for DCS type, onset time, and mortality. Experimental animals (N = 21; 69 ± 4.1 kg), PROP_1.0, were compared to PROP_1.0-OPB₄₅ (N = 8; 69 ± 2.8 kg) with the same dive profile, except for a 45 min OPB prior to decompression. In Experiment 2, the same methodology was used with the following changes: swine pressurized to 2.8 ATA for 28 h; experimental group (N = 25; 67 ± 3.3 kg), PROP_{0.5 bis}, propranolol 0.5 mg · kg⁻¹ bis (twice) (IV) was administered at 22 h and 26 h. Control animals (N = 25; 67 ± 3.9 kg) received normal saline.RESULTS: OPB reduced mortality in PROP_1.0-OBP₄₅ compared to PROP_1.0 (0% vs. 71%). PROP_0.5 bis had increased mortality compared to CONTROL (60-% vs. 4%).DISCUSSION: Administration of beta blockers prior to saturation decompression appears to increase DCS and worsen mortality in a swine model; however, their effects in bounce diving remain unknown.Forbes AS, Regis DP, HallAA, Mahon RT, Cronin WA. Propranolol effects on decompression sickness in a simulated DISSUB rescue in swine. Aerosp Med Hum Perform. 2017; 88(4):385–391.

OBJECTIVE: In aviation psychology, there is a constant need for the cognitive evaluation of pilots as part of operational fitness and safety criteria.METHODS: A cross-sectional study with comparison between the performance of Israeli Air Force pilot cadets (N = 318) and U.S. Air Force pilot training candidates (N = 512) as assessed by a cognitive battery was undertaken. The data of the comparison group was collected from Callister, King, and Retzlaff, as published in 1996.RESULTS: In general, the means in the three components composing the battery—speed, accuracy, and throughput variables—indicated that the Israeli Air Force pilot cadets' scores were higher than those of the U.S. Air Force pilot candidates' scores in 50 of 53 variables. Nonsignificant differences were found in Accuracy of shifting attention-arrow color (SATAC), pathfinder-combined (PFC), and pathfinder-letter (PFL).CONCLUSIONS: The difference in performance between the two groups may be due to differences in population characteristics. However, these results need to be considered cautiously, as the groups were sampled at a sizeable time gap (1996 for the U.S. Air Force vs. 2013 for the Israeli Air Force), with each time period characterized by different cultural and technological influences.Gordon S, Goren C, Carmon E, Shelef L. Cognitive evaluation of Israeli Air Force pilot cadets. Aerosp Med Hum Perform. 2017; 88(4):392–398.

INTRODUCTION: Education frequently dictates students need to study for prolonged periods of time to adequately prepare for examinations. This is especially true with aviation preflight indoctrination (API) candidates who have to assimilate large volumes of information in a limited amount of time during API training. The purpose of this study was to assess caffeine consumption patterns (frequency, type, and volume) among naval aviation candidates attending API to determine the most frequently consumed caffeinated beverage and to examine if the consumption of a nonenergy drink caffeinated beverage was related to energy drink consumption.METHODS: Data were collected by means of an anonymous 44-item survey administered and completed by 302 students enrolled in API at Naval Air Station Pensacola, FL.RESULTS: Results indicated the most frequently consumed caffeinated beverage consumed by API students was coffee (86.4%), with daily coffee consumption being approximately 28% and the most frequent pattern of consumption being 2 cups per day (85%). The least frequently consumed caffeinated beverages reported were energy drinks (52%) and energy shots (29.1%). The present study also found that the consumption patterns (weekly and daily) of caffeinated beverages (coffee and cola) were positively correlated to energy drink consumption patterns.DISCUSSION: Naval aviation candidates’ consumption of caffeinated beverages is comparable to other college and high school cohorts. This study found that coffee and colas were the beverages of choice, with energy drinks and energy shots being the least frequently reported caffeinated beverages used. Additionally, a relationship between the consumption of caffeinated beverages and energy drinks was identified.Sather TE, Williams RD, Delorey DR, Woolsey CL. Caffeine consumption among naval aviation candidates. Aerosp Med Hum Perform. 2017; 88(4):399–405.

INTRODUCTION: The present study reports the clinical features of middle ear barotrauma in student pilots in the Republic of Korea Air Force.METHODS: The authors reviewed medical records of student pilots with barotrauma. The grade of barotrauma was assigned using Teed’s classification. This study included nasal symptoms, endoscopic findings of the nasal cavity, and clinical course (duration, recurrence). The relationship between middle ear barotrauma and the nasal airway was also evaluated.RESULTS: There were 57 cases in 51 pilots included. There were 49 cases (86.0%) that showed unilateral disease and 4 subjects experienced relapse. Two subjects (3.9%) had chronic rhinosinusitis and four subjects (7.8%) had allergic rhinitis. Ear fullness was reported in all cases, while hearing loss and persistent ear pain were reported in 3 cases (5.3%) and 19 cases (33.3%), respectively. Stuffy nose (26 cases, 45.6%) and rhinorrhea (24 cases, 42.1%) were relatively common. Most cases were Grade 0 (23 cases, 40.3%) or Grade III (27 cases, 47.4%) according to Teed’s classification. Septal deviation was observed in 12 cases (21.0%), while turbinate hypertrophy was seen in 53 cases (93.0%) and increased nasal discharge in 33 cases (57.9%). The grade of barotrauma varied significantly according to the severity of turbinate hypertrophy and nasal discharge. The mean duration of disease was 6.8 d.DISCUSSION: Nasal symptoms and endoscopic findings showed some association with the grade and duration of barotrauma. Most cases resolved within a week; however, barotrauma showed persistence or relapse in some cases.Sohn JH, Cho KR. Middle ear barotrauma in student pilots. Aerosp Med Hum Perform. 2017; 88(4):406–412.

BACKGROUND: Around 25% of people involved in a helicopter accident in water do not survive. From time to time, physicians and their medical staff are required to fly over water in a helicopter to attend one or more seriously ill patients. Many will have had little or no experience of the issues involved if the helicopter has an accident in the water. Also as Family Practitioners, Aeromedical Examiners, and Flight Surgeons, they are asked to provide advice to patients, travel agents, and airline booking agents about whether an overwater helicopter flight is advisable or not.METHOD: From 50 yr of helicopter accident evidence in the scientific literature, government agency reports, and statistics from the military safety centers and the offshore oil industry, the critical hazards involved and risks to medical staff and their patients have been identified.RESULTS: Patients most at risk are those who suffer from cardiovascular or respiratory disease, have physical disabilities, have a very large body size, and anyone who is a non-swimmer. Medical staff are at risk if they are not familiar with the procedure for escape from a flooded inverted cabin and difficulties after escape from the fuselage with life jackets, life rafts, and sometimes the necessity to swim ashore.CONCLUSIONS: With 50 yr of hindsight, many of the deaths were preventable, and many lives can be saved if a series of very simple mental and physical preventive actions are taken by anyone stepping on to a helicopter that flies over water.Brooks CJ, MacDonald CV. Safety considerations for medical staff and patients who fly over water in a helicopter for work or recreation. Aerosp Med Hum Perform. 2017; 88(4):413–417.

INTRODUCTION: The extravehicular activity suit currently used by the United States in space includes a liquid cooling and ventilation garment (LCVG) that controls thermal conditions. Previously, we demonstrated that self-perspiration for evaporative cooling (SPEC) garment effectively lowers skin temperature without raising humidity in the garment. However, the cooling effect is delayed until a sufficient dose of water permeates and evaporates. In the present study, we hypothesized that wearer-controlled vaporization improves the cooling effect.METHODS: Six healthy subjects rode a cycle ergometer under loads of 30, 60, 90, and 120 W for durations of 3 min each. Skin temperature and humidity on the back were measured continuously. Subjects wore and tested three garments: 1) a spandex garment without any cooling device (Normal); 2) a simulated LCVG (s-LCVG) or spandex garment knitted with a vinyl tube for flowing and permeating water; and 3) a garment that allowed wearer-controlled vaporization (SPEC-W).RESULTS: The use of s-LCVG reduced skin temperature by 1.57 ± 0.14°C during 12 min of cooling. Wearer-controlled vaporization of the SPEC-W effectively and significantly lowered skin temperature from the start to the end of cycle exercise. This decrease was significantly larger than that achieved using s-LCVG. Humidity in the SPEC-W was significantly lower than that in s-LCVG.DISCUSSION: This preliminary study suggests that SPEC-W is effective in lowering skin temperature without raising humidity in the garment. The authors think it would be useful in improving the design of a cooling system for extravehicular activity.Tanaka K, Nagao D, Okada K, Nakamura K. Cooling effects of wearer-controlled vaporization for extravehicular activity. Aerosp Med Hum Perform. 2017; 88(4):418–422.

BACKGROUND: The U.S. Air Force performs more than 6000 aeromedical transport flights annually, both internationally and domestically. Many of these flights include patients requiring pain relief medications. The risk of side effects from such medications administered at altitude is unknown, but understanding these risks is vital when selecting the safest pain management strategies to achieve optimal postflight outcomes.METHODS: Using an evidence-based medication side effect risk assessment model, we compared our patient-centric approach to an aircrew-centric approach using medications approved for use in U.S. Navy aircrew. We then determined the patient-centric side effect risk of medications commonly used during Air Force aeromedical evacuation (AE).RESULTS: The patient-centric approach to medication side effect risk assessment demonstrates that the majority of medications currently approved for use during AE have an acceptable side effect risk for the patient (18/22, 82%). Four approved drugs displayed significantly elevated patient risk, with risk scores between 2.0- and 3.2-fold greater than the statistically determined upper allowable (“acceptable”) limit and between 1.2- and 2.0-fold above the upper control (“tolerable”) limit.DISCUSSION: Our results suggest that pain management strategies during AE should be tailored individually to minimize the risk associated with pain medications administered en route.Huntsberger SA, Butler WP, Chapleau RR. Patient-centric side effect risk assessment for medications used during aeromedical evacuations. Aerosp Med Hum Perform. 2017; 88(4):423–426.

BACKGROUND: Decompression sickness (DCS) is a potential danger and risk for both divers and aircrew alike. DCS is also a potential side effect of altitude (hypobaric) chamber training as well and can present long after training occurs. Literature review shows that altitude chamber induced DCS has approximately a 0.25% incidence.CASE REPORT: A 32-yr-old, active duty military member developed symptoms of DCS 3 h after his hypobaric chamber training. Unfortunately, he did not seek treatment for DCS until 48 h after the exposure. His initial treatment included ground level oxygen therapy for 30 min at 12 L of oxygen per minute using a nonrebreathing mask. He achieved complete symptom resolution and was returned to duty. However, 12 d after his initial Flight Medicine evaluation, the patient returned complaining of a right temporal headache, multijoint pains, and fatigue. He was treated in the hyperbaric chamber and had complete resolution of symptoms. He was returned to flying status and 5 mo later denied any return of symptoms.DISCUSSION: Hypobaric chamber familiarity training is a requirement for all military aircrew personnel to allow them assess their ability to identify symptoms of hypoxia. This training method is not only costly to maintain, but it also places aircrew and chamber technicians at risk for potential long-term side effects from failed recompression treatment of DCS. We are presenting a case of recurrent DCS symptoms 12 d after initial ground level oxygen therapy.Gentry J, Rango J, Zhang J, Biedermann S. Latent presentation of decompression sickness after altitude chamber training in an active duty flier. Aerosp Med Hum Perform. 2017; 88(4):427–430.

BACKGROUND: Extra corporeal life support (ECLS) is presently first line therapy for refractory cardiogenic shock. Mobile circulatory support teams implant ECLS or extra corporeal membrane oxygenation (ECMO) in patients in the hospital without circulatory support. These patients are then transported to specialized centers. Here we report a case of sending a mobile circulatory support team abroad, followed by air ambulance evacuation, which, to our knowledge, has never been used as part of medical assistance abroad.CASE REPORT: In June, during a holiday in Turkey, a 56-yr-old woman complained about chest pain. She had a cardiac arrest and was resuscitated with no no-flow time in the local hospital. ECG showed ST segment elevation. Medic'Air International medical assistance (Paris, France) contacted the hospital, which was not equipped with coronarography or cardiac ultrasound and the local treating doctor refused transfer of the patient to another facility. A medical team completed by a cardiothoracic surgeon and a perfusionist went from Paris to the patient’s bedside by air ambulance. They implemented the ECLS and successfully repatriated the patient to her home country (Belgium). The patient’s condition improved, she neurologically improved, and returned home on the 14^th day.DISCUSSION: Possible indications for ECLS repatriations firstly take into account recognized ECLS indications and case-by-case discussions on the evaluation of inadequacy of the health facilities and risk-benefit balance. In international medical assistance, this case’s description is an example of repatriation for patients who previously could not be transferred due to high risk of such intervention.Gerard D, Raffin H, Lebreton G. Aeromedical evacuation using extra corporeal life support after resuscitated cardiac arrest. Aerosp Med Hum Perform. 2017; 88(4):431–433.

Ensley D. You’re the flight surgeon: green laser event. Aerosp Med Hum Perform. 2017; 88(4):437–439.

Milner MR. You’re the flight surgeon: an unusual case of pharyngitis. Aerosp Med Hum Perform. 2017; 88(4):439–442.