INTRODUCTION: The purpose of this study was to analyze historical hearing sensitivity data to determine factors associated with an occupationally significant change in hearing sensitivity in U.S. Air Force aviation-related personnel.METHODS: This study was a longitudinal, retrospective cohort analysis of audiogram records for Air Force aviation-related personnel on active duty during calendar year 2013 without a diagnosis of non-noise-related hearing loss. The outcomes of interest were raw change in hearing sensitivity from initial baseline to 2013 audiogram and initial occurrence of a significant threshold shift (STS) and non-H1 audiogram profile. Potential predictor variables included age and elapsed time in cohort for each audiogram, gender, and Air Force Specialty Code. Random forest analyses conducted on a learning sample were used to identify relevant predictor variables. Mixed effects models were fitted to a separate validation sample to make statistical inferences.RESULTS: The final dataset included 167,253 nonbaseline audiograms on 10,567 participants. Only the interaction between time since baseline audiogram and age was significantly associated with raw change in hearing sensitivity by STS metric. None of the potential predictors were associated with the likelihood for an STS. Time since baseline audiogram, age, and their interaction were significantly associated with the likelihood for a non-HI hearing profile.DISCUSSION: In this study population, age and elapsed time since baseline audiogram were modestly associated with decreased hearing sensitivity and increased likelihood for a non-H1 hearing profile. Aircraft type, as determined from Air Force Specialty Code, was not associated with changes in hearing sensitivity by STS metric.Greenwell BM, Tvaryanas AP, Maupin GM. Risk factors for hearing decrement among U.S. Air Force aviation-related personnel. Aerosp Med Hum Perform. 2018; 89(2):80–86.

BACKGROUND: Heat stress limits endurance exercise performance. Combining precooling and warm-up prior to endurance exercise in the heat may exploit the benefits of both strategies while avoiding the potential negative consequences of each. This study tested the hypothesis that precooling combined with warm-up improves time trial cycling performance in the heat relative to either treatment alone.METHODS: Nine healthy men completed three 16.1-km time trials in 33°C after: 1) precooling (ice slurry and ice vest) alone (PREC); 2) warm-up alone (WU); or 3) PREC plus WU (COMBO).RESULTS: T_re was lower after PREC compared to WU throughout exercise and lower than COMBO for the first 12 km; COMBO was lower than WU for the first 4 km. T_sk during PREC was lower than COMBO and WU for the first 8 km, and lower in COMBO than WU for the first 4 km. PREC lowered pre-exercise heart rate relative to COMBO and WU (68 ± 10, 106 ± 12, 101 ± 13 bpm, respectively), but it increased similarly during exercise. Local sweat rate (SR) was lower in PREC (0.1 ± 0.1 mg · cm⁻² · min⁻¹) than COMBO (0.5 ± 0.2 mg · cm⁻² · min⁻¹) and WU (0.6 ± 0.2 mg · cm⁻² · min⁻¹) for the first 4 km. Treatments did not differentially affect performance (PREC = 31.9 ± 1.9 min, COMBO = 32.6 ± 2.7 min, WU = 33.1 ± 2.9 min).DISCUSSION: We conclude precooling alone or with warm-up mitigated thermal strain during exercise, but did not significantly improve 16.1-km cycling time trial performance.Al-horani RA, Wingo JE, Ng J, Bishop P, Richardson M. Precooling and warm-up effects on time trial cycling during heat stress. Aerosp Med Hum Perform. 2018; 89(2):87–93.

INTRODUCTION: A loss of 1% or more of bodyweight due to dehydration has a negative effect on cognitive performance, which could critically affect flight safety. There is no mention in the literature concerning the amounts of military pilots’ fluid loss during flight. The aim of this study was to quantify fluid loss of pilots during military flight.METHODS: There were 48 aviators (mean age 23.9) from the Israeli Air Force who participated in the study, which included 104 training flights in various flight platforms. Bodyweight, urine specific gravity, and environmental heat strain were measured before and after each flight. Fluid loss was calculated as the weight differences before and after the flight. We used a univariate and one-way ANOVA to analyze the effect of different variables on the fluid loss.RESULTS: The mean fluid loss rate was 462 ml · h⁻¹. The results varied among different aircraft platforms and depended on flight duration. Blackhawk pilots lost the highest amount of fluids per flight, albeit had longer flights (mean 108 min compared to 35.5 in fighter jets). Jet fighter pilots had the highest rate of fluid loss per hour of flight (up to 692 ml, extrapolated).CONCLUSION: Overall, at 11 flights (11%) aircrew completed their flight with a meaningful fluid loss. We conclude that military flights may be associated with significant amount of fluid loss among aircrew.Levkovsky A, Abot-Barkan S, Chapnik L, Doron O, Levy Y, Heled Y, Gordon B. Aviator’s fluid balance during military flight. Aerosp Med Hum Perform. 2018; 89(2):9498.

INTRODUCTION: The purpose of this research was to evaluate neuroendocrine and physical performance responses in sailors and Marines undergoing U.S. Navy Survival, Evasion, Resistance, and Escape (SERE) training.METHODS: Participants were 20 men (Age: 25.3 ± 3.6 yr; Height: 178.1 ± 6.1 cm; Weight: 83.7 ± 12.6 kg). Men were further split into high fit (N = 10) and low fit (N = 10) subgroups based on physical fitness test scores. Blood samples were obtained at baseline (T1), stress (T2), and recovery (T3) timepoints, and were analyzed for plasma epinephrine, plasma norepinephrine, plasma dopamine, serum cortisol, serum testosterone, and plasma neuropeptide Y. Vertical jump and handgrip tests were performed at T1 and T2.RESULTS: Stress hormone concentrations were significantly elevated at T2, with a concomitant reduction in testosterone concentrations. NPY concentrations did not increase at T2, but decreased significantly at T3. Subjects maintained performance on vertical jump and handgrip tests from T1 to T2. Significant between group differences were observed in norepinephrine (high fit: 3530.64 ± 2146.54 pmol · L⁻¹, low fit: 4907.16 ± 3020.85 pmol · L⁻¹) and NPY (high fit: 169.30 ± 85.89 pg · ml⁻¹, low fit: 123.02 ± 88.86 pg · ml⁻¹) concentrations at T3.CONCLUSION: This study revealed that despite significant increases in stress hormone concentrations in all subjects during SERE, fitter subjects exhibited differential hormonal responses during recovery, with quicker return of norepinephrine and NPY to baseline concentrations. This suggests physical fitness level may have a protective effect in recovery from periods of high stress military training.Szivak TK, Lee EC, Saenz C, Flanagan SD, Focht BC, Volek JS, Maresh CM, Kraemer WJ. Adrenal stress and physical performance during military survival training. Aerosp Med Hum Perform. 2018; 89(2):99–107.

INTRODUCTION: The provision of medical care in exploration-class spaceflight is limited by mass, volume, and power constraints, as well as limitations of available skillsets of crewmembers. A quantitative means of exploring the risks and benefits of inclusion or exclusion of onboard medical capabilities may help to inform the development of an appropriate medical system. A pilot project was designed to demonstrate the utility of an early tradespace analysis tool for identifying high-priority resources geared toward properly equipping an exploration mission medical system.METHODS: Physician subject matter experts identified resources, tools, and skillsets required, as well as associated criticality scores of the same, to meet terrestrial, U.S.-specific ideal medical solutions for conditions concerning for exploration-class spaceflight. A database of diagnostic and treatment actions and resources was created based on this input and weighed against the probabilities of mission-specific medical events to help identify common and critical elements needed in a future exploration medical capability.RESULTS: Analysis of repository data demonstrates the utility of a quantitative method of comparing various medical resources and skillsets for future missions. Directed database queries can provide detailed comparative estimates concerning likelihood of resource utilization within a given mission and the weighted utility of tangible and intangible resources.DISCUSSION: This prototype tool demonstrates one quantitative approach to the complex needs and limitations of an exploration medical system. While this early version identified areas for refinement in future version development, more robust analysis tools may help to inform the development of a comprehensive medical system for future exploration missions.Antonsen EL, Mulcahy RA, Rubin D, Blue RS, Canga MA, Shah R. Prototype development of a tradespace analysis tool for spaceflight medical resources. Aerosp Med Hum Perform. 2018; 89(2):108–114.

INTRODUCTION: An experiment in a program of research supporting the sense-assess-augment (SAA) framework is described. The objective is to use physiological measures to assess operator cognitive workload in remotely piloted aircraft (RPA) operations, and provide augmentation to assist the operator in times of high workload. In previous experiments, physiological measures were identified that demonstrate sensitivity to changes in workload. The current research solely focuses on the augmentation component of the SAA paradigm. This line of research uses a realistic RPA simulation with varying levels of workload.METHODS: Recruited from the Midwest region were 12 individuals (6 women) to participate in the experiment. The subjects were trained to perform a surveillance task and a tracking task using RPAs. There was also a secondary task in which subjects were required to answer cognitive probes. A within subjects factorial design was employed with three factors per task. Subjective workload estimates were acquired using the NASA-TLX. Performance data were calculated using a composite scoring algorithm.RESULTS: Augmentation significantly improved performance and reduced workload in both tasks. In the surveillance task, augmentation increased performance from 573.78 to 679.04. Likewise, augmentation increased performance in the tracking task from 749.39 to 791.81. Augmentation was more beneficial in high workload conditions than low workload conditions.DISCUSSION: The increase in performance and decrease in workload associated with augmentation is an important and anticipated finding. This suggests that augmentation should only be provided when it is truly needed, especially if the augmentation requires additional assets and/or resources.Gruenwald CM, Middendorf MS, Hoepf MR, Galster SM. Augmenting human performance in remotely piloted aircraft. Aerosp Med Hum Perform. 2018; 89(2):115–121.

INTRODUCTION: With the development of the commercial space industry, growing numbers of spaceflight participants will engage in activities with a risk for pulmonary injuries, including pneumothorax, ebullism, and decompression sickness, as well as other concomitant trauma. Medical triage capabilities for mishaps involving pulmonary conditions have not been systematically reviewed. Recent studies have advocated the use of point-of-care ultrasound to screen for lung injury or illness. The operational utility of portable ultrasound systems in disaster relief and other austere settings may be relevant to commercial spaceflight.METHODS: A systematic review of published literature was conducted concerning the use of point-of-care pulmonary ultrasound techniques in austere environments, including suggested examination protocols for triage and diagnosis.RESULTS: Recent studies support the utility of pulmonary ultrasound examinations when performed by skilled operators, and comparability of the results to computed tomography and chest radiography for certain conditions, with important implications for trauma management in austere environments.DISCUSSION: Pulmonary injury and illness are among the potential health risks facing spaceflight participants. Implementation of point-of-care ultrasound protocols could aid in the rapid diagnosis, triage, and treatment of such conditions. Though operator-dependent, ultrasound, with proper training, experience, and equipment, could be a valuable tool in the hands of a first responder supporting remote spaceflight operations.Johansen BD, Blue RS, Castleberry TL, Antonsen EL, Vanderploeg JM. Point-of-care ultrasound for pulmonary concerns in remote spaceflight triage environments. Aerosp Med Hum Perform. 2018; 89(2):122–129.

INTRODUCTION: A theory is presented to explain the major findings regarding motion sickness and to synthetize current theories concerning its etiology. The theory proposes that an imbalance in the output of the two major organs of the labyrinth—favoring the semicircular canals over the otolith organs—is responsible for most instances of motion sickness as experienced in terrestrial and microgravity environments.METHODS: Strengths and limitations of current theories are first outlined before the different roles of the canals and otoliths in the genesis of motion sickness symptoms are described.RESULTS: The proposed theory is shown to explain a large number of findings and integrate current theories.DISCUSSION: The role of vestibular imbalance in motion sickness may be a consequence of the more general differences between the canals and otoliths in autonomic control.Previc FH. Intravestibular balance and motion sickness. Aerosp Med Hum Perform. 2018; 89(2):130–140.

BACKGROUND: Acetabular labral tears in the hip have become an increasingly common finding in active duty members due to improved diagnostic capabilities. This has led to a dramatic increase in operative management despite a lack of evidence to support clear long-term benefits. Literature review demonstrated overwhelmingly positive short-term outcomes for labral repairs; however, scattered case reports exist demonstrating debilitating outcomes in young patients, ultimately resulting in total hip arthroplasty.CASE REPORT: A 27-yr-old pilot originally presented with groin pain. Initial X-ray demonstrated a CAM lesion of the right hip and subsequent MRA showed an acetabular labral tear. The patient underwent open arthrotomy with labral repair and femoroplasty with minimal improvement in symptoms. Repeat imaging over 2 yr showed early onset osteoarthritis with rapid progression and a recurrent labral tear. Due to the significant progression of osteoarthritis, the patient was given the choice between a repeat labral repair and total hip arthroplasty. The patient elected for hip arthrotomy with labral repair and extensive synovectomy, which yielded minimal improvement in symptoms.DISCUSSION: Acetabular labral tears have become a hot topic in the field of orthopedics as a result of a surge in diagnoses likely due to improvements in imaging, most notably MRAs. This has led to considerable debate regarding how to best manage this condition. The literature overwhelmingly shows positive short-term outcomes for surgical management; however, long-term follow-up studies are lacking. The literature has demonstrated multiple case reports resulting in significant complications as a result of these operations, including chondrolysis and eventual need for total hip arthroplasty. Therefore, patient selection is critical as the population tends to be young and active, and the potential complications can be catastrophic. In any case, it is clear that further research is required.Sardon CJ, Resnick ML. Severe arthritic changes following acetabular labral repair and femoroplasty in an air force pilot. Aerosp Med Hum Perform. 2018; 89(2):147–150.

Patterson A, Rosenthal J. You’re the flight surgeon: foot drop. Aerosp Med Hum Perform. 2018; 89(2):151–153.