INTRODUCTION: Recent physiological incidents involving pilots of high performance fighter aircraft have raised the question of whether inadvertent, short bursts of significantly reduced oxygen could negatively impact real-time performance. This study evaluated normobaric, real-time performance in the setting of transient near-anoxia to inform future countermeasure development.METHODS: The study was performed on 12 healthy subjects without significant medical history. Following collection of baseline data, real-time performance changes were evaluated during sequentially increasing periods of near-anoxic gas exposure (F_Io₂ = 1%) using a computer-based performance assessment tool. Both room air and 100% oxygen were used as the prebreathe/recovery gases. Statistical analysis was performed on the results.RESULTS: Under normobaric conditions, subjects inspiring up to five near-anoxic breaths showed no significant performance decrement in either accuracy or effective actions per minute. Mean accuracy up to five near-anoxic breaths was 0.67 (SD = 0.01) as compared to a baseline mean of 0.68 (SD = 0.02). Hyperoxia had a protective effect on subject physiological response to near anoxia.DISCUSSION: These normobaric findings offer an assessment of real-time performance changes in the setting of transient, near-anoxic gas exposure. Overall, the results help inform the design of increasingly complex aircraft oxygen delivery systems in terms of how tightly such systems must match the sea-level gas equivalent with increasing altitude. This is particularly relevant as such systems are being called upon to ensure safe aircrew operations across an expanding operational flight envelope.McEachen JC, Issa AN, Marck JW, Steinkraus LW, Johnson BD. Real-time effects of normobaric, transient near-anoxia on performance. Aerosp Med Hum Perform. 2015; 86(2):76–81.

INTRODUCTION: Given the effects of cold water immersion on breath-hold (BH) capabilities, a practical training exercise was developed for military/paramilitary personnel completing a helicopter underwater egress training (HUET) program. The exercise was designed to provide firsthand experience of the effects of cold water exposure on BH time.METHODS: After completing the required HUET, 47 subjects completed two BH testing sessions as well as a short questionnaire. The first BH was completed while standing on the pool deck. The second BH was completed while fully immersed (face down) in 2-3°C water. There were 40 of the volunteers who also breathed from an emergency breathing system (EBS) while in the cold water.RESULTS: Results demonstrated that BH capabilities in cold water were significantly lower than those in ambient air. A significant correlation was also found between BH in air and the difference in cold water vs. air BH capabilities, which suggests that subjects who can hold their breath the longest in air experienced the greatest decrease in BH when immersed. Results indicate that 92% of the subjects reported that the practical cold water immersion exercise had a high value. Finally, 58% of those who used the EBS reported that it was harder to breathe in cold water than while in the training pool (approximately 22°C).DISCUSSION: The BH times for this group were similar to those reported in previous cold water immersion studies. Based on the questionnaire results, it is possible, when carefully applied, to include a practical cold water immersion exercise into existing HUET programs.Taber MJ, MacKinnon SN, Power J, Walker R. Breath-hold times in air compared to breath-hold times during cold water immersions. Aerosp Med Hum Perform. 2015; 86(2):82–87.

BACKGROUND: Susceptibility of healthy astronauts to orthostatic hypotension and presyncope is exacerbated upon return from spaceflight. Up to 64% of astronauts experience postflight orthostatic intolerance. A promising countermeasure for postflight orthostatic intolerance is fluid loading by giving crew salt tablets and water prior to re-entry. The primary goal of the current study was to determine the optimal time window prior to re-entry when individual crewpersons would initiate fluid loading.METHODS: There were 16 subjects who were given two 6-h exposures, with and without fluid loading (conditions), to head-down tilt (HDT) to simulate the effects of microgravity. Pre- and post-HDT stand tests of orthostatic tolerance were given. Physiological measurements recorded included heart rate, blood pressure, peripheral blood volume, total peripheral resistance, and impedance cardiography. Echocardiography measures of stroke volume and cardiac output were also recorded.RESULTS: Data were analyzed with three-way repeated measures ANOVA (gender × condition × time). Only the condition × time interaction was significant for mean arterial pressure. Post hoc multiple comparison tests revealed significant increases in mean arterial pressure occurred between hours 1 and 3 of HDT after fluid loading (10 mmHg higher than no fluid).DISCUSSION: These findings indicate that the optimal time for crew to begin fluid loading is within 1 to 3 h prior to re-entry. Nonsignificant trends of multiple cardiovascular responses showed similar time profiles. The large amount of individual variability suggests that fluid loading alone may be an inadequate countermeasure for all crewmembers. Further research is needed on possible adjunct methods of tailoring countermeasures for individuals.Cowings P, Toscano W, Kanis D, Saicheur T, Ravikumar A, Gebreyesus F. Fluid loading effects on temporal profiles of cardiovascular responses to head-down tilt. Aerosp Med Hum Perform. 2015; 86(2):88–96.

INTRODUCTION: Our prior publication suggested that elevated serum concentrations of low-density lipoprotein (LDL) was protective against the development of acute mountain sickness (AMS) while an inflammatory response was contributory to its development. The use of 3-hydroxy-3-methylglutaryl-coenzyme-A-reductase inhibitors (“statins”) may be of interest to those traveling to altitude—these medications will lower serum LDL concentrations, but are also reported to have anti-inflammatory properties.METHODS: Prior to flying from sea level to the South Pole (∼10,498.7 ft or 3200 m) during the austral summer months of 2005-2006 and 2006-2007, the 248 subjects provided informed consent. Questionnaires related to AMS symptoms, acetazolamide use, personal history, and anthropometrics were paired with results from blood samples. Statin use was reported by six subjects who were matched for age, sex, altitude of residence, and acetazolamide use with seven subjects not using a statin.RESULTS: No significant differences were identified in any of the matched variables between the groups. No statin users reported symptoms of AMS while 57% of participants not using a statin did report AMS symptoms (P = 0.03). No significant difference was noted between LDL levels in the statin group (108.3 ± 61.0) as compared to the group not taking statins (104.6 ± 22.1) (P = 0.88).DISCUSSION: Our previous results suggested that elevated LDL was protective while an inflammatory response was contributory with respect to AMS development. The present results suggest that statin use may provide protection against AMS symptoms, possibly through an anti-inflammatory property, despite its lipid-lowering capacity.Harrison MF, Johnson BD. Statin use and the development of acute mountain sickness. Aerosp Med Hum Perform. 2015; 86(2):97–102.

INTRODUCTION: The coding of space as near and far is not only determined by arm-reaching distance, but is also dependent on how the brain represents the extension of the body space. Recent reports suggest that the dissociation between reaching and navigational space is not limited to perception and action but also involves memory systems. It has been reported that gender differences emerged only in adverse learning conditions that required strong spatial ability.METHODS: In this study we investigated navigational versus reaching memory in air force pilots and a control group without flight experience. We took into account temporal duration (working memory and long-term memory) and focused on working memory, which is considered critical in the gender differences literature.RESULTS: We found no gender effects or flight hour effects in pilots but observed gender effects in working memory (but not in learning and delayed recall) in the nonpilot population (Women’s mean = 5.33; SD= 0.90; Men’s mean = 5.54; SD= 0.90). We also observed a difference between pilots and nonpilots in the maintenance of on-line reaching information: pilots (mean = 5.85; SD=0.76) were more efficient than nonpilots (mean = 5.21; SD=0.83) and managed this type of information similarly to that concerning navigational space. In the navigational learning phase they also showed better navigational memory (mean = 137.83; SD=5.81) than nonpilots (mean = 126.96; SD=15.81) and were significantly more proficient than the latter group.DISCUSSION: There is no gender difference in a population of pilots in terms of navigational abilities, while it emerges in a control group without flight experience. We found also that pilots performed better than nonpilots. This study suggests that once selected, male and female pilots do not differ from each other in visuo-spatial abilities and spatial navigation.Verde P, Piccardi L, Bianchini F, Guariglia C, Carrozzo P, Morgagni F, Boccia M, Di Fiore G, Tomao E. Gender differences in navigational memory: pilots vs. nonpilots. Aerosp Med Hum Perform. 2015; 86(2):103–111.

BACKGROUND: Aviation exposes pilots to various occupationally related hazards, including ionizing radiation and chemical combustion. The possible increased risk of prostate cancer among pilots in comparison to the general population is a subject of debate. This systematic review and meta-analysis aimed to determine the quality of supporting evidence and magnitude of this association.METHODS: All studies pertaining to prostate cancer in pilots were retrieved from multiple databases and from a manual search. Any study that assessed the incidence of prostate cancer relative to the incidence in the general population was included regardless of language or size. A random effect model was used to pool relative risks (RR) across studies. Heterogeneity was assessed using the Q statistic and I².RESULTS: Eight studies with a low risk of bias were included in the meta-analysis. Pilots had an increased risk of developing prostate cancer compared to the general population [RR 2.0; 95% confidence interval (CI), 1.5–2.7]. The analysis was associated with substantial heterogeneity (I² = 79%). Several subgroups had significantly increased risk, such as African American pilots (RR 10.00; 95% CI, 5.04–19.86) and military pilots (RR 3.30; 95% CI, 2.03–5.39).CONCLUSION: Pilots are at least twice as likely to develop prostate cancer compared to the general population. The implications of these findings are important considering the high prevalence of prostate cancer and the large number of pilots in the workforce.Raslau D, Summerfield DT, Abu Dabrh AM, Steinkraus LW, Murad MH. The risk of prostate cancer in pilots: a meta-analysis. Aerosp Med Hum Perform. 2015; 86(2):112–117. <related-article related-article-type="other"/>

BACKGROUND: Effects of hypobarism and hypoxia on visual performance and mainly on contrast sensitivity (CS) are well known. The purpose of this study was to compare the adjustments of corneal thickness in hypobaric hypoxia conditions with changes in contrast sensitivity.METHODS: There were 12 healthy, emmetropic subjects assigned to the 14^th Wing Aircrew based in Pratica di Mare AFB (Rome, Italy) who were evaluated for changes occurring in central corneal thickness (CCT), measured by portable ultrasonic pachymeter, and CS, assessed after reading the standard Pelli-Robson charts, during modification of atmospheric pressure and, therefore, of oxygen partial pressure.RESULTS: Hypobaric hypoxia conditions in pilots raised CCT (550 μm to 600 μm) and reduced CS (1.95 log to 1.05 log) in a statistically significant result.DISCUSSION: The study demonstrated that hypoxia and variations of atmospheric pressure may produce corneal edema, including changes of CCT and, correlatively, CS reduction.Pescosolido N, Barbato A, Di Blasio D. Hypobaric hypoxia: effects on contrast sensitivity in high altitude environments. Aerosp Med Hum Perform. 2015; 86(2):118–124.

PURPOSE: U.S. combat activities in Iraq and Afghanistan saw the implementation of multiple ad hoc systems incorporated onto commercial aerial platforms for supporting operations. The use of manned platforms, many of which were never intended for the long-duration missions to which they have been applied, has had human factor and aviation life support equipment (ALSE) implications. The physiological stress-inducing nature of high temperatures (> 40 C) is one such concern. This study assessed cockpit temperatures in one such platform during actual combat missions over Iraq.METHODS: Three missions were flown in Iraq during 2011 on an ad hoc aerial platform and dry bulb temperature readings were recorded periodically at head height at different crew stations. Relative humidity was also recorded.RESULTS: Temperatures demonstrated wide variability during mission profiles, ranging from > 40°C to 15°C. Ground heat-soaked cabin temperatures were measured as high as 48°C. High temperatures could be experienced for up to an hour prior to departure.DISCUSSION: While ad hoc aerial platform use has operational merits, the lack of adequate crew life support systems on such platforms can pose thermal risks to the aircrews. More detailed investigation is needed to determine core temperature response of aircrews during such operations and platform specific ALSE requirements to better support aircrew mission effectiveness.Fredricks TR, Nakazawa M. Dry bulb temperature effects on crew well-being in long-duration ad hoc platform flights. Aerosp Med Hum Perform. 2015; 86(2):125–130.

INTRODUCTION: This study compares observational data from two situations designed as planetary exploration missions: the Tara expedition and the Mars-500 experiment. We examined the issue of distinct environmental factors, isolation vs. confinement, which may have different or similar impacts on crews’ behavioral manifestations for long-term adaptation, such as on a Mars mission. The Tara expedition was a 507-d polar drift of the Tara schooner embedded in the Arctic ice with two successive periods of summer and winter-over in an isolated environment. The Mars-500 experiment took place in Moscow and was a 520-d simulation of a trip to Mars, the Mars landing, and the return trip to Earth in a confined environment.METHODS: We used the ethological method based on observation, description, and quantification of individual and interindividual behaviors. These events were scored from video recordings made during daily life activities and aggregated according to the summer period and to the outgoing trip for the whole crew (N = 6) for each situation, respectively.RESULTS: We did not observe differences in the frequency of facial expressions and in the duration of body interactions. Conversely, there were differences in the frequency of collateral acts and in the duration of personal actions with the highest levels during the Mars-500 experiment (0.52 /min and 41,799 s); the highest level of visual interactions was observed during the Tara expedition (33,167 s).DISCUSSION: We found that confinement generates stress manifestations vs. isolation, that isolation enhances social relashionships vs. confinement, and that the crew adapted positively to both environments.Tafforin C. Confinement vs. isolation as analogue environments for Mars missions from a human ethology viewpoint. Aerosp Med Hum Perform. 2015; 86(2):131–135.

BACKGROUND: Isolated perivesicular hematomas are uncommonly described and not an injury typically reported in the literature after parachuting or skydiving.CASE REPORT: Herein, we described a series of three patients with isolated perivesicular hematomas sustained after military parachuting. All three patients were managed nonoperatively after a somewhat prolonged hospital course. Despite the lack of orthopedic injuries, all required physical therapy consultation and required an assisting device to aide with ambulation at the time of discharge. For all three individuals, follow-up imaging months after the injury demonstrated a continued presence of the hematoma. Clinically, the patients continued to have ambulatory and urological difficulties for several months after their injury.DISCUSSION: This injury pattern is uncommonly reported in the literature. An appropriate index of suspicion must be maintained or there may be a delay in diagnosis. Management of these injuries requires coordinated care between the trauma service, urology, and physical therapy.Plackett TP, Lynn DC, Zagol BR, Malone BA, Detro JF, Seery JM, Deveaux PG, Sawyer EM, Ellison RW. Isolated perivesicular hematoma after military parachuting. Aerosp Med Hum Perform. 2015; 86(2):136–139.

ABSTRACT: On ISS missions and explorer class missions, unexpected medical and surgical emergencies could be disastrous. Lack of ability to rapidly assess and make critical decisions affects mission capability. Current imaging modalities on ISS consist only of ultrasound. There are many acute diagnoses which ultrasound alone cannot diagnose. Portable X-Ray imaging (radiography) technology has advanced far enough to where it is now small enough, cheap enough, and accurate enough to give diagnostic quality images sent wirelessly to the onboard computer and on Earth for interpretation while fitting in something the size of a briefcase. Although further research is warranted, Portable Radiography is an important addition to have on ISS and future Explorer Class Missions while maintaining a very small footprint.Lerner DJ, Parmet AJ. Portable radiography: a reality and necessity for ISS and explorer-class missions. Aerosp Med Hum Perform. 2015; 86(2):140–142.

Park BY. You’re the flight surgeon: bronchogenic cyst. Aerosp Med Hum Perform. 2015; 86(2):144–146.

Tay E, Gan WH. You’re the flight surgeon: sudden foot drop in an aviator after centrifuge training. Aerosp Med Hum Perform. 2015; 86(2):146–148.