INTRODUCTION: Nonhypoxic hypobaric (low atmospheric pressure) occupational exposure, such as experienced by U.S. Air Force U-2 pilots and safety personnel operating inside altitude chambers, is associated with increased subcortical white matter hyperintensity (WMH) burden. The pathophysiological mechanisms underlying this discrete WMH change remain unknown. The objectives of this study were to demonstrate that occupational exposure to nonhypoxic hypobaria is associated with altered white matter integrity as quantified by fractional anisotropy (FA) measured using diffusion tensor imaging and relate these findings to WMH burden and neurocognitive ability.METHODS: There were 102 U-2 pilots and 114 age- and gender-controlled, health-matched controls who underwent magnetic resonance imaging. All pilots performed neurocognitive assessment. Whole-brain and tract-wise average FA values were compared between pilots and controls, followed by comparison within pilots separated into high and low WMH burden groups. Neurocognitive measurements were used to help interpret group difference in FA values.RESULTS: Pilots had significantly lower average FA values than controls (0.489/0.500, respectively). Regionally, pilots had higher FA values in the fronto-occipital tract where FA values positively correlated with visual-spatial performance scores (0.603/0.586, respectively). There was a trend for high burden pilots to have lower FA values than low burden pilots.DISCUSSION: Nonhypoxic hypobaric exposure is associated with significantly lower average FA in young, healthy U-2 pilots. This suggests that recurrent hypobaric exposure causes diffuse axonal injury in addition to focal white matter changes.McGuire SA, Boone GRE, Sherman PM, Tate DF, Wood JD, Patel B, Eskandar G, Wijtenburg SA, Rowland LM, Clarke GD, Grogan PM, Sladky JH, Kochunov PV. White matter integrity in high-altitude pilots exposed to hypobaria. Aerosp Med Hum Perform. 2016; 87(12):983–988.

INTRODUCTION: Attention plays a central role in cognitive processing; ineffective attention may induce accidents in flight operations. The objective of the current research was to examine military pilots’ attention distributions between chasing a moving target and a stationary target.METHOD: In the current research, 37 mission-ready F-16 pilots participated. Subjects’ eye movements were collected by a portable head-mounted eye-tracker during tactical training in a flight simulator. The scenarios of chasing a moving target (air-to-air) and a stationary target (air-to-surface) consist of three operational phases: searching, aiming, and lock-on to the targets.RESULTS: The findings demonstrated significant differences in pilots’ percentage of fixation during the searching phase between air-to-air (M = 37.57, SD = 5.72) and air-to-surface (M = 33.54, SD = 4.68). Fixation duration can indicate pilots’ sustained attention to the trajectory of a dynamic target during air combat maneuvers. Aiming at the stationary target resulted in larger pupil size (M = 27,105, SD = 6565), reflecting higher cognitive loading than aiming at the dynamic target (M = 23,864, SD = 8762).DISCUSSION: Pilots’ visual behavior is not only closely related to attention distribution, but also significantly associated with task characteristics. Military pilots demonstrated various visual scan patterns for searching and aiming at different types of targets based on the research settings of a flight simulator. The findings will facilitate system designers’ understanding of military pilots’ cognitive processes during tactical operations. They will assist human-centered interface design to improve pilots’ situational awareness. The application of an eye-tracking device integrated with a flight simulator is a feasible and cost-effective intervention to improve the efficiency and safety of tactical training.Li W-C, Yu C-S, Braithwaite G, Greaves M. Pilots’ attention distributions between chasing a moving target and a stationary target. Aerosp Med Hum Perform. 2016; 87(12):989–995.

INTRODUCTION: Few studies have evaluated physiological responses to high acceleration forces during actual flight and to our knowledge no normative data has been acquired by technologies such as wearable biosensors during high performance jet aircraft operations.METHODS: In-flight physiological data from an FDA cleared portable triaxial accelerometer and bio-sensor were observed from five active duty F-18 pilots of the Naval Flight Demonstration Squadron (Blue Angels). Of the five pilots, three were formation pilots who flew lower G profiles and two were solo pilots who flew higher G profiles. Physiological parameters monitored were heart rate, respiratory rate, temperature, caloric expenditure, and duration of exposure to levels of acceleration.RESULTS: Evaluated were 25 practice demonstration flights; 9 flights were excluded secondary to incomplete or inaccurate physiological data. We observed no significant bradycardia during a total of 189 maneuvers which met inclusion criteria for push-pull events (PPE) or isolated −G_z exposures. Further analysis of 73 PPE revealed an overall significant rise in HR following the PPE, where mean heart rate was 106 (95% CI, 100:112) at the beginning of the push and 129 (95% CI, 123:135) following the pull.DISCUSSION: A majority of the flights monitored provided reliable physiological data. Initial data suggests, contrary to currently held aeromedical doctrine, maneuvers such as the “push-pull” do not evoke vasovagal based bradycardic responses in aerobatic pilots. Possible explanations for these findings are sympathetic nervous system activation through adaptation and/or sustained isometric resistance from control inputs, both of which are areas of future research for our team.Rice GM, Snider D, Moore JL, Lavan JT, Folga R, VanBrunt TB. Evidence for –G_z adaptation observed with wearable biosensors during high performance jet flight. Aerosp Med Hum Perform. 2016; 87(12):996–1003.

BACKGROUND: This is a cross-sectional observational study to investigate the safety and feasibility of integrating changing body positions and physical activity in a hypoxic challenge test (HCT). The secondary objective was to compare oxygen saturation (S_po₂) in two different locations (forehead and finger).METHODS: Included were 12 pediatric to young adult patients with congenital heart (N = 7) or lung disease (N = 5). An HCT was performed using breathing room air (21% oxygen) while sitting and breathing a normobaric hypoxic gas mixture (15% oxygen) through a facemask while seated, lying supine, standing, walking 3 km/h, and walking 5 km/h in a nonrandomized order.RESULTS: All patients, except one, successfully passed the HCT. Three patients reported symptoms, possibly related to hypoxia. Median S_po₂ during the HCT decreased in all body positions compared with room air. In 9/12 (finger oximeter) vs. 6/12 (forehead oximeter) patients S_po₂ decreased below 90% in one or more body positions at rest. In 11/12 (finger oximeter) vs. 3/12 (forehead oximeter) patients S_po₂ decreased below 90% during mild exercise. There was no significant difference in S_po₂ between the different body positions. However, patients desaturated significantly more during mild exercise (walking 3km/h and 5 km/h). S_po₂% measured at the forehead gave significantly higher values compared to the index finger.DISCUSSION: HCT is safe and feasible in children and adolescents with congenital heart or lung disease, and gives additional information about oxygenation during physical activity in addition to resting conditions. Simulated hypoxia of 8202 ft (2500 m) induced a small but significant decrease in S_po₂%.Spoorenberg ME, Hulzebos EHJ, Takken T. Feasibility of hypoxic challenge testing in children and adolescents with congenital heart and lung disease. Aerosp Med Hum Perform. 2016; 87(12):1004–1009.

INTRODUCTION: Most fighter pilots report cervical pain during their careers. Recommendations for remediation lack evidence. We sought to determine whether regular use of a home cervical traction device could decrease reported cervical pain in F-15C pilots.METHODS: An institutional review board-approved, Health Insurance Portability and Accountability Act-compliant, controlled crossover study was undertaken with 21 male F-15C fighter pilots between February and June 2015. Of the 21 subjects, 12 completed 6 wk each of traction and control, while logging morning, postflying, and post-traction pain. Pain was compared with paired t-tests between the periods, from initial pain scores to postflying, and postflying to post-traction.RESULTS: In the traction phase, initial pain levels increased postflight, from 1.2 (0.7) to 1.6 (1.0) Subsequent post-traction pain levels decreased to 1.3 (0.9), with a corresponding linear decrease in pain relative to pain reported postflight. The difference in pain levels after traction compared to initial levels was not significant, indicating that cervical traction was effective in alleviating flying-related pain. Control pain increased postflight from 1.4 (0.9) to 1.9 (1.3). Daily traction phase pain was lower than the control, but insignificant.DISCUSSION: To our knowledge, this is the first study of home cervical traction to address fighter pilots’ cervical pain. We found a small but meaningful improvement in daily pain rating when using cervical traction after flying. These results help inform countermeasure development for pilots flying high-performance aircraft. Further study should clarify the optimal traction dose and timing in relation to flying.Chumbley EM, O’Hair N, Stolfi A, Lienesch C, McEachen JC, Wright BA. Home cervical traction to reduce neck pain in fighter pilots. Aerosp Med Hum Perform. 2016; 87(12):1010–1015.

BACKGROUND: Metabolic syndrome (MetS) is a cluster of metabolic abnormalities that can affect civilian pilots’ health. Its prevalence and the correlation with periodontal disease (PD) among pilots had not been previously reported. The aim of the study was to determine MetS and PD status, and to reveal their relationship in a representative sample of Chinese civilian pilots.METHODS: We investigated 303 civilian pilots (mean age 34.92 ± 7.66 yr). General information as well as blood and saliva samples were collected. Diagnostic criteria for MetS were based on the joint interim statements of several medical organizations. Periodontal status was evaluated by Community Periodontal Index (CPI). Measurements included body mass index (BMI), waist circumference (WC), blood pressure (BP), concentration of serum high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), fasting plasma glucose (FPG), saliva matrix metalloproteinase-8, and tissue inhibitors of matrix metalloproteinase-1 (TIMP-1).RESULTS: Of the subjects, 38.28% showed MetS and 23.10% showed periodontitis. Significant differences were found between the MetS and non-MetS pilots in total flying hours, CPI, WC, BP, TG, HDL-C, FPG, BMI, and TIMP-1. Significant relationships were found between MetS and CPI, BMI, and TIMP-1. The odds ratios were 3.378 (95%CI: 1.889–5924) for CPI, 1.269 (95%CI: 1.101–1.463) for BMI, and 0.600 (95%CI: 0.399–0.904) for TIMP-1.CONCLUSION: The prevalence of MetS was sufficiently high to be a matter of medical concern, and was associated with PD among civilian pilots.Chen X, Xie L, Liu Y, Chen D, Yu Q, Gan X, Yu H. Metabolic syndrome and periodontal disease among civilian pilots. Aerosp Med Hum Perform. 2016; 87(12):1016–1020.

INTRODUCTION: Stress Management Training programs are increasingly being adopted in the military field for resilience empowerment and primary stress prevention. In the last several years, advanced technologies (virtual reality in particular) have been integrated in order to develop more innovative and effective stress training programs for military personnel, including soldiers, pilots, and other aircrew professionals. This systematic review describes experimental studies that have been conducted in recent years to test the effectiveness of virtual reality-based Stress Management Training programs developed for military personnel. This promising state-of-the-art technology has the potential to be a successful new approach in empowering soldiers and increasing their resilience to stress.METHODS: To provide an overview from 2001 to 2016 of the application of virtual reality for Stress Management Training programs developed for the military, a computer-based search for relevant publications was performed in several databases. Databases used in the search were PsycINFO, Web of Science (Web of Knowledge), PubMed, and Medline. The search string was: (“Virtual Reality”) AND (“Military”) AND [“Stress Training” OR (“Stress Management”)].RESULTS: There were 14 studies that met the inclusion criteria and were included in the review.DISCUSSION: The main observation to be drawn from this review is that virtual reality can provide interactive Stress Management Training to decrease levels of perceived stress and negative affect in military personnel. This technology appears to be a promising tool for assessing individuals’ resilience to stress and for identifying the impact that stress can have on physiological reactivity and performance.Pallavicini F, Argenton L, Toniazzi N, Aceti L, Mantovani F. Virtual realtiy applications for stress management training in the military. Aerosp Med Hum Perform. 2016; 87(12):1021–1030.

BACKGROUND: High altitude cerebral edema (HACE) is a fulminant, deadly, and yet still unpredictable brain disease. A new prophylactic treatment for HACE and its predecessor, acute mountain sickness (AMS), needs to be developed without the contraindications or adverse effect profiles of acetazolamide and dexamethasone. Since neovascularization signals are likely key contributors to HACE/AMS, our approach was to examine already existing anti-angiogenic drugs to inhibit potential initiating HACE pathway(s). This approach can also reveal crucial early steps in the frequently debated mechanism of HACE/AMS pathogenesis.METHODS: We exposed four rat cohorts to hypobaric hypoxia and one to sea level (hyperbaric) conditions. The cohorts were treated with saline controls, an anti-angiogenesis drug (motesanib), a pro-angiogenesis drug (deferoxamine), or an intraperitoneal version of the established AMS prophylaxis drug, acetazolamide (benzolamide). Brain tissue was analyzed for cerebrovascular leak using the Evans Blue Dye (EVBD) protocol.RESULTS: We observed significantly increased EVBD in the altitude control and pro-angiogenesis (deferoxamine) cohorts, and significantly decreased EVBD in the anti-angiogenesis (motesanib), established treatment (benzolamide), and sea-level cohorts.DISCUSSION: Anti-angiogenesis-treated cohorts demonstrated less cerebrovascular extravasation than the altitude control and pro-angiogenesis treated rats, suggesting promise as an alternative prophylactic HACE/AMS treatment. The leak exacerbation with pro-angiogenesis treatment and improvement with anti-angiogenesis treatment support the hypothesis of early neovascularization signals provoking HACE. We demonstrate statistically significant evidence to guide further investigation for VEGF- and HIF-inhibitors as HACE/AMS prophylaxis, and as elucidators of still unknown HACE pathogenesis.Tarshis S, Maltzahn J, Loomis Z, Irwin DC. Preventing high altitude cerebral edema in rats with repurposed anti-angiogenesis pharmacotherapy. Aerosp Med Hum Perform. 2016; 87(12):1031–1035.

BACKGROUND: The ecology of medical care model has been used in various populations with varying results. We aimed to apply this model in the population of Israeli Air Force (IAF) aviators.METHODS: An anonymous questionnaire was presented to all Israeli Air Force aviators during their mandatory yearly check-up over 1 yr starting on November 26^th, 2012. The questionnaire contained items on demographic, personal, and military details, as well as items on the presence of clinical symptoms, and various health care contacts in the previous month. We assessed the differences between career and reserve personnel using a X² test.RESULTS: There were 325 aviators who completed the questionnaire (2 women, 132 reserves). Clinical symptoms were reported by 62.5% of the responders. Over half (52.6%) had any health care encounter: 23.7% with a dentist, 17.9% with non-MD therapists, 12.6% with a specialist, and 11.7% with a primary physician. A significant difference between reserve and career personnel was found only in primary care visits. Out of the aviators who reported having clinical symptoms, 70.9% did not visit a physician. Of those who did not seek medical care, 42.4% reported that the symptoms were viewed as unimportant, 41% thought they would disappear by themselves, 40.3% could not find time for treatment.CONCLUSIONS: Aviators in the IAF have similar rate of clinical symptoms as in other unselected populations. Those who report symptoms usually do not visit a physician for treatment. When they do seek advice it is mostly from non-MD practitioners.Gordon B, Levy Y, Yemini T, Carmon E, Erlich Y, Hermoni D. The ecology of medical care among Israeli military aviators. Aerosp Med Hum Perform. 2016; 87(12):1036–1040.

BACKGROUND: To measure nitrogen (N₂) wash-out and uptake requires elaborate set-ups, especially when doing the measurements at increased or decreased ambient pressure. Here we present a transportable device for quantifying N₂ turnover in humans which can be used at different ambient pressures.METHODS: A modified close-circuit electronic rebreather was used to assess N₂ turnover. Changes in N₂ volume within the rebreathing circuit, reflecting N₂ uptake or washout, were derived from the continuously monitored total system volume and the calculated volumes of oxygen and water vapor. The calculation of continuous N₂ volume curves was performed off-line using dedicated computer software.RESULTS: Four subjects participated in the proof-of-concept tests. At steady state, the drift in calculated N₂ volume in the rebreathing circuit over a 1-h duration was minimal. Three of the subjects participated in additional N₂ steady-state measurements where 1019 mL (BTPD) of N₂ was injected into the rebreathing circuit over 20 min and the measured volume increase was 1006 ± 32 mL. Lastly, N₂ elimination was assessed during decompression to 0.5 atm and while breathing hyperoxic gas. N₂ uptake was measured during compression to 1.8 atm. The elimination and uptake curves were deemed to be realistic.DISCUSSION: A method for assessing N₂ turnover in humans has been developed and a first evaluation has been performed. It is easy to work with operationally and can be used at different ambient pressures. More research is needed in order to further validate it as a method for assessing N₂ turnover in humans.Sundblad P, Frånberg O, Siebenmann C, Gennser M. Measuring uptake and elimination of nitrogen in humans at different ambient pressures. Aerosp Med Hum Perform. 2016; 87(12):1045–1050.

DeFlorio PT. You’re the flight surgeon: supraventricular tachycardia. Aerosp Med Hum Perfom. 2016; 87(12):1051–1053.