BACKGROUND: A sudden loss of external visual cues during critical phases of flight results in spatial disorientation. This is due to undetected horizontal and vertical drift when there is little tolerance for error and correction delay as the helicopter is close to the ground. Three helmet-mounted symbology system concepts were investigated in the simulator as potential solutions for the legacy Griffon helicopters.METHOD: Thirteen Royal Canadian Air Force (RCAF) Griffon pilots were exposed to the Helmet Display Tracking System for Degraded Visual Environments (HDTS), the BrownOut Symbology System (BOSS), and the current RCAF AVS7 symbology system. For each symbology system, the pilot performed a two-stage departure and a single-stage approach. The presentation order of the symbology systems was randomized. Objective performance metrics included aircraft speed, altitude, attitude, and distance from the landing point. Subjective measurements included situation awareness, mental effort, perceived performance, perceptual cue rating, and NASA Task Load Index. Repeated measures analysis of variance and subsequent planned comparison for all the objective and subjective measurements were performed between the AVS7, HDTS, and BOSS.RESULTS: Our results demonstrated that HDTS and BOSS showed general improvement over AVS7 in two-stage departure. However, only HDTS performed significantly better in heading error than AVS7. During the single-stage approach, BOSS performed worse than AVS7 in heading root mean square error, and only HDTS performed significantly better in distance to landing point and approach heading than the others.DISCUSSION: Both the HDTS and BOSS possess their own limitations; however, HDTS is the pilots’ preferred flight display.Cheung B, McKinley RA, Steels B, Sceviour R, Cosman V, Holst P. Simulator study of helmet-mounted symbology system concepts in degraded visual environments. Aerosp Med Hum Perform. 2015; 86(7):588–598.

BACKGROUND: Aerobic exercise capacity provides information regarding cardiorespiratory health and physical capacity. However, in many populations the ability to measure whole-body or leg aerobic exercise capacity is limited due to physical disability or lack of appropriate equipment. Clinically there is a need to evaluate aerobic capacity in individuals who cannot use their legs for locomotion. In astronauts the habitable space for exercise testing in the next generation of space exploration systems may be restricted and may not support the traditional lower body testing. Therefore, the purpose was to determine if upper body physical performance could estimate lower body aerobic capacity.METHODS: Maximal O₂ uptake (<inline-graphic xlink:href="amhp4181inf1.gif"/>o_2max), gas exchange threshold (GET), and the highest sustainable rate of aerobic metabolism [arm cranking critical power (_ACP) and lower body critical speed (_LCS)] were determined in 55 conditioned men and women during arm-cranking and treadmill running.RESULTS: <inline-graphic xlink:href="amhp4181inf1.gif"/>o_2max and GET (48.6 ± 7.6 and 29.0 ± 4.8 ml · kg⁻¹ · min⁻¹, respectively) were significantly lower during arm-cranking exercise compared to running (27.1 ± 7.6 and 13.5 ± 2.6 ml · kg⁻¹ · min⁻¹, respectively). The <inline-graphic xlink:href="amhp4181inf1.gif"/>o₂ at _ACP was significantly lower than the <inline-graphic xlink:href="amhp4181inf1.gif"/>o₂ at the _LCS (18.4 ± 5.01 vs. 39.5 ± 8.1 ml · kg⁻¹ · min⁻¹, respectively). There was a significant correlation between arm-cranking and lower body <inline-graphic xlink:href="amhp4181inf1.gif"/>o_2max, GET, and the <inline-graphic xlink:href="amhp4181inf1.gif"/>o₂ at _LCS and _ACP. Backward stepwise regression analyses revealed that arm-cranking physical fitness could explain 67%, 40%, and 49% of the variance in lower body <inline-graphic xlink:href="amhp4181inf1.gif"/>o_2max, GET, and _LCS, respectively.DISCUSSION: Results suggest arm-cranking exercise can be used to obtain an approximation of lower body aerobic capacity.Ade CJ, Broxterman RM, Craig JC, Schlup SJ, Wilcox SL, Barstow TJ. Upper body aerobic exercise as a possible predictor of lower body performance. Aerosp Med Hum Perform. 2015; 86(7):599–605.

INTRODUCTION: Shoulder injuries due to working inside the space suit are some of the most serious and debilitating injuries astronauts encounter. Space suit injuries occur primarily in the Neutral Buoyancy Laboratory (NBL) underwater training facility due to accumulated musculoskeletal stress. We quantitatively explored the underlying causal mechanisms of injury.METHODS: Logistic regression was used to identify relevant space suit components, training environment variables, and anthropometric dimensions related to an increased propensity for space-suited injury. Two groups of subjects were analyzed: those whose reported shoulder incident is attributable to the NBL or working in the space suit, and those whose shoulder incidence began in active duty, meaning working in the suit could be a contributing factor.RESULTS: For both groups, percent of training performed in the space suit planar hard upper torso (HUT) was the most important predictor variable for injury. Frequency of training and recovery between training were also significant metrics. The most relevant anthropometric dimensions were bideltoid breadth, expanded chest depth, and shoulder circumference. Finally, record of previous injury was found to be a relevant predictor for subsequent injury. The first statistical model correctly identifies 39% of injured subjects, while the second model correctly identifies 68% of injured subjects.DISCUSSION: A review of the literature suggests this is the first work to quantitatively evaluate the hypothesized causal mechanisms of all space-suited shoulder injuries. Although limited in predictive capability, each of the identified variables can be monitored and modified operationally to reduce future impacts on an astronaut’s health.Anderson AP, Newman DJ, Welsch RE. Statistical evaluation of causal factors associated with astronaut shoulder injury in space suits. Aerosp Med Hum Perform. 2015; 86(7):606–613.

INTRODUCTION: This study simultaneously quantified the effects of normobaric hypoxia (NH), hypobaric hypoxia (HH), exercise duration, and exposure time on acute mountain sickness severity (AMS-C).METHODS: Thirty-six subjects (27.7 ± 7.8 yr) participated in a partial repeated measures study, completing two of six conditions: normobaric normoxia (NN: 300 m/984 ft equivalent), NH or HH (Po₂ = 91 mmHg; 4400 m/14,436 ft equivalent), combined with moderate intensity cycling for 10 or 60 min. Subjects completed the Environmental Symptoms Questionnaire and oxygen saturation (S_po₂) was measured before, 1.5 h, 4 h, and 6.5 h into an 8-h exposure, and 1.5 h post-exposure. We fit multiple linear regression models with cluster adjusted standard errors on the exposure times using NH, HH, and long exercise as indicator variables, and AMS-C as the outcome variable. The S_po₂ and pre-exposure AMS-C score were used as covariates.RESULTS: NH and HH led to substantial and progressively increasing AMS-C, but NN did not. The effect of HH on AMS-C was significantly different from NH, with AMS-C in HH being 1.6 times higher than in NH. HH led to significantly increasing AMS-C, regardless of the exercise duration, while NH only did so in combination with longer exercise.DISCUSSION: Increases in AMS-C were each independently related to NH, HH, and long duration exercise, with HH affecting AMS-C more severely. This suggests that hypobaria may affect AMS development above the level induced by hypoxia alone. This further suggests that NH and HH may not be interchangeable for studying AMS and that exercise duration may impact physiological responses.DiPasquale DM, Strangman GE, Harris NS, Muza SR. Hypoxia, hypobaria, and exercise duration affect acute mountain sickness. Aerosp Med Hum Perform. 2015; 86(7):614–619.

INTRODUCTION: We describe how geographic information systems (GIS) can be used to assess and compare estimated transport time for helicopter and ground emergency medical services. Recent research shows that while the odds of a trauma patient’s survival increase with helicopter emergency medical services (HEMS), they may not increase to the extent necessary to make HEMS cost effective. This study offers an analytic tool to objectively quantify the patient travel time advantage that HEMS offers compared to ground emergency medical services (GEMS).METHODS: Using helicopter dispatch data from the Maryland State Police from 2000–2011, we computed transport time estimates for HEMS and GEMS, compare these results to a reference transport time of 60 min, and use geospatial interpolation to extrapolate the total response times for each mode across the study region.RESULTS: Mapping the region’s trauma incidents and modeling response times, our findings indicate the GIS framework for calculating transportation time tradeoffs is useful in identifying which areas can be better served by HEMS or GEMS.DISCUSSION: The use of GIS and the analytical methodology described in this study present a method to compare transportation by air and ground in the prehospital setting that accounts for how mode, distance, and road infrastructure impact total transport time. Whether used to generate regional maps in advance or applied real-time, the presented framework provides a tool to identify earlier incident locations that favor HEMS over GEMS transport modes.Widener MJ, Ginsberg Z, Schleith D, Floccare DJ, Hirshon JM, Galvagno S. Ground and helicopter emergency medical services time tradeoffs assessed with geographic information. Aerosp Med Hum Perform. 2015; 86(7):620–627.

INTRODUCTION: Bone loss due to weightlessness is a significant concern for astronauts’ mission safety and health upon return to Earth. This problem is monitored with bone densitometry (DXA), the clinical tool used to assess skeletal strength. DXA has served clinicians well in assessing fracture risk and has been particularly useful in diagnosing osteoporosis in the elderly postmenopausal population for which it was originally developed. Over the past 1–2 decades, however, paradoxical and contradictory findings have emerged when this technology was widely employed in caring for diverse populations unlike those for which it was developed. Although DXA was originally considered the surrogate marker for bone strength, it is now considered one part of a constellation of factors–described collectively as bone quality–that makes bone strong and resists fracturing, independent of bone density. These characteristics are beyond the capability of routine DXA to identify, and as a result, DXA can be a poor prognosticator of bone health in many clinical scenarios. New clinical tools are emerging to make measurement of bone strength more accurate. This article reviews the historical timeline of bone density measurement (dual X-ray absorptiometry), expands upon the clinical observations that modified the relationship of DXA and bone strength, discusses some of the new clinical tools to predict fracture risk, and highlights the challenges DXA poses in the assessment of fracture risk in astronauts.Licata AA. Challenges of estimating fracture risk with DXA: changing concepts about bone strength and bone density. Aerosp Med Hum Perform. 2015; 86(7):628–632.

Cephalad redistribution of intravascular and extravascular fluid occurs as a result of weightlessness during spaceflight. This provokes cardiovascular, cardiopulmonary, and autonomic nervous system responses. The resulting altered functional state can result in orthostatic hypotension and intolerance upon landing and return to a gravity environment. In-flight lower body negative pressure (LBNP) transiently restores normal body fluid distribution. Early in the U.S. space program, LBNP was devised as a way to test for orthostatic intolerance. With the development of the Skylab Program and longer duration spaceflight, it was realized that it could provide a method of monitoring orthostatic intolerance in flight and predicting the post-landing orthostatic response. LBNP was also investigated not only as an in-flight cardiovascular orthostatic stress test, but also as a countermeasure to cardiovascular deconditioning on Soviet space stations, Skylab, and the Shuttle. It is still being used by the Russian program on the International Space Station as an end-of-flight countermeasure.Campbell MR, Charles JB. Historical review of lower body negative pressure research in space medicine. Aerosp Med Hum Perform. 2015; 86(7):633–640.

INTRODUCTION: Helicopter flying is a complex psychomotor task requiring continuous control inputs to maintain stable flight and conduct maneuvers. Flight safety is impaired when this psychomotor performance is compromised. A comprehensive understanding of the psychomotor performance of helicopter pilots, under various operational and physiological conditions, remains to be developed. The purpose of this study was to develop a flight simulator-based technique for capturing psychomotor performance data of helicopter pilots.METHODS: Three helicopter pilots conducted six low-level flight sequences in a helicopter simulator. Accelerometers applied to each flight control recorded the frequency and magnitude of movements.RESULTS: The mean (± SEM) number of control inputs per flight was 2450 (± 136). The mean (± SEM) number of control inputs per second was 1.96 (± 0.15). The mean (± SEM) force applied was 0.44 G (± 0.05 G). No significant differences were found between pilots in terms of flight completion times or number of movements per second. The number of control inputs made by the hands was significantly greater than the number of foot movements. The left hand control input forces were significantly greater than all other input forces.DISCUSSION: This study shows that the use of accelerometers in flight simulators is an effective technique for capturing accurate, reliable data on the psychomotor performance of helicopter pilots. This technique can be applied in future studies to a wider range of operational and physiological conditions and mission types in order to develop a greater awareness and understanding of the psychomotor performance demands on helicopter pilots.McMahon TW, Newman DG. A methodology to determine the psychomotor performance of helicopter pilots during flight maneuvers. Aerosp Med Hum Perform. 2015; 86(7):641–646.

INTRODUCTION: Eye fixations can be distributed in three ways: randomly, in clusters, and regularly. However, there is always a continuum among these types, because these spatial patterns are the result of a process evolving over time. The focus of the present work was to study the changes over time observed in the Nearest Neighbor Index (NNI), an index derived from the spatial distribution of eye fixations that has been reported to be sensitive to variations in mental workload. Of particular interest are periodic changes in the ultradian timescale (an ultradian rhythm is a recurrent period or cycle repeated throughout a 24-h circadian day).METHODS: Data from a previously reported experiment were further analyzed using temporal spectral analysis, which is one of the most commonly used techniques for studying measurements collected at regularly spaced intervals of time.RESULTS: An ultradian rhythm with a periodicity between 2 and 15 min was found, which is compatible with results obtained by analyzing reaction times in prolonged vigilance tasks.DISCUSSION: The identification of a periodicity in the allocation of mental resources should be considered in the design of automation support that is dynamically matched to mental workload.Di Nocera F, Ranvaud R, Pasquali V. Spatial pattern of eye fixations and evidence of ultradian rhythms in aircraft pilots. Aerosp Med Hum Perform. 2015; 86(7):647–651.

OBJECTIVE: The aim of the POP (odontological problems among divers) study was to assess dental barotrauma among French military divers exposed to an underwater environment.METHODS: A questionnaire on dental barotrauma was completed by the divers who presented at the SMHEP (Centre for Hyperbaric Medicine and Diving Expertise) for their quadrennial medical exam from March 2011 to July 2014.RESULTS: There were 1317 questionnaires completed, representing 60.6% of all French military divers. A total of 5.3% of divers had a dental barotrauma (70/1317), mainly fracture and/or loss of dental restoration. Dental barotrauma disrupted diving in 34.3% of cases. A total of 76.4% of divers were informed by a military physician of the importance of maintaining good oral health and 88.5% of divers consult their dentist at least once a year. Of the participants, 82.5% made their dentist aware they are divers, but only 4.9% of the dental practitioners advised their patient not to dive after some types of dental treatments and 12.8% indicated that, as divers, they need adapted dental treatments.CONCLUSIONS: Dental barotrauma was experienced by 1 in 19 military divers. Nevertheless, a contradiction exists between the frequency of dental barotraumas and the rigorous medical and dental follow-up of military divers. We note that there is inadequate dental management of divers when dental issues are identified. To avoid this unsatisfactory situation, “diving dentistry” should be taught to military and civilian dentists and physicians to make them aware of the potential dental complications and preventive measures associated with operating in a subaquatic environment.Gunepin M, Derache F, Dychter L, Blatteau J-E, Nakdimon I, Zadik Y. Dental barotrauma in French military divers: results of the POP study. Aerosp Med Hum Perform. 2015; 86(7):652–655.

INTRODUCTION: Medical Guidelines for Airline Travel provide information that enables healthcare providers to properly advise patients who plan to travel by air. Not everyone is fit to travel by air and physicians should advise their patients accordingly. They should review the passenger’s medical condition, giving special consideration to the dosage and timing of any medications, contagiousness, and the need for special assistance during travel. In general, an individual with an unstable medical condition should not fly; cabin altitude, duration of exposure, and altitude of the destination airport are all considerations when recommending a passenger for flight.Thibeault C, Evans AD, Dowdall NP. AsMA medical guidelines for air travel: fitness to fly and medical clearances. Aerosp Med Hum Perform. 2015; 86(7):656.

INTRODUCTION: Medical Guidelines for Airline Travel provide information that enables healthcare providers to properly advise patients who plan to travel by air. Treating physicians should advise patients in need of special services to contact the airline well before travel to find out if the required services will be available. Ensuring the required services are available throughout a journey can be challenging, especially when different airlines and aircraft types are involved. For example, airlines carry a limited supply of oxygen for use in the event of an unexpected in-flight emergency; however, this supply is not intended for use by passengers needing supplemental oxygen. Arrangements must be made in advance with the airline. Therefore, early contact with the airline is helpful.Thibeault C, Evans AD. AsMA medical guidelines for air travel: airline special services. Aerosp Med Hum Perform. 2015; 86(7):657–658.

Pizzino DR. You’re the flight surgeon: Ménière's disease. Aerosp Med Hum Perform. 2015; 86(7):662–664.

Hettinger K. You’re the flight surgeon: priapism. Aerosp Med Hum Perform. 2015; 86(7):664–667.