INTRODUCTION: Flying a helicopter is a complex psychomotor skill requiring constant control inputs from pilots. A deterioration in psychomotor performance of a helicopter pilot may be detrimental to operational safety. The aim of this study was to test the hypothesis that psychomotor performance deteriorates over time during sustained operations and that the effect is more pronounced in the feet than the hands. The subjects were helicopter pilots conducting sustained multicrew offshore flight operations in a demanding environment. The remote flight operations involved constant workload in hot environmental conditions with complex operational tasking.METHODS: Over a period of 6 d 10 helicopter pilots were tested. At the completion of daily flying duties, a helicopter-specific screen-based compensatory tracking task measuring tracking accuracy (over a 5-min period) tested both hands and feet. Data were compared over time and tested for statistical significance for both deterioration and differential effect.RESULTS: A statistically significant deterioration of psychomotor performance was evident in the pilots over time for both hands and feet. There was also a statistically significant differential effect between the hands and the feet in terms of tracking accuracy. The hands recorded a 22.6% decrease in tracking accuracy, while the feet recorded a 39.9% decrease in tracking accuracy.DISCUSSION: The differential effect may be due to prioritization of limb movement by the motor cortex due to factors such as workload-induced cognitive fatigue. This may result in a greater reduction in performance in the feet than the hands, posing a significant risk to operational safety.McMahon TW, Newman DG. The differential effect of sustained operations on psychomotor skills of helicopter pilots. Aerosp Med Hum Perform. 2018; 89(6):496–502.

BACKGROUND: The cold pressor test (CPT) involves acute hand or foot exposure to cold water. CPT hyper-responders have unique traits, including risk of hypertension and a greater vasoconstrictor reserve and g force tolerance compared to hypo-responders. The purpose of this study was to uncover differences in cardiovascular and sympathetic biomarkers between responder types.METHODS: Healthy volunteers (N = 30) submerged one hand into cold water (3.3 ± 0.8°C) for 5 min. Blood pressure, heart rate, cardiac output, and cardiac parameters were recorded using an automated monitor, impedance cardiography, and a beat-to-beat monitoring system. We analyzed for salivary α-amylase (SαA), which is a convenient biomarker of the sympathetic nervous system. Subjects were stratified post hoc into hyper-responders (≥ 22 mmHg) and hypo-responders (< 22 mmHg) based on change in systolic blood pressure during CPT.RESULTS: Hyper-responders had a significantly lower baseline heart rate (64 ± 7 bpm), cardiac output (5.6 ± 0.9 L · min⁻¹), and SαA (60 ± 37 U · mL⁻¹) compared to hypo-responders (73 ± 9 bpm, 6.9 ± 1.3 L · min⁻¹, 165 ± 122 U · mL⁻¹). During the cold immersion, hyper-responders had significantly higher systolic blood pressure (150 ± 14 mmHg), diastolic blood pressure (91 ± 10 mmHg), mean arterial pressure (129 ± 17 mmHg), and systemic vascular resistance (1780 ± 640 dyn · s⁻¹ · cm⁻⁵) than hypo-responders (130 ± 14 mmHg, 81 ± 10 mmHg, 110 ± 9 mmHg, 1290 ± 220 dyn · s⁻¹ · cm⁻⁵). The change in systolic blood pressure correlated with baseline SαA (r = −0.455, P = 0.011) and baseline heart rate (r = −0.374, P = 0.042).DISCUSSION: Baseline characteristics influenced by sympathetic tone such as SαA, heart rate, and cardiac output are indicative of responses to CPT. Our data supports the use of baseline values to predict blood pressure response to acute cold exposure and indicates an intrinsic difference between CPT responder phenotypes.Youssef M, Ghassemi A, Carvajal Gonczi CM, Kugathasan TA, Kilgour RD, Darlington PJ. Low baseline sympathetic tone correlates to a greater blood pressure change in the cold pressor test. Aerosp Med Hum Perform. 2018; 89(6):503–509.

INTRODUCTION: Rotary wing pilot neck strain is increasing in prevalence due to the combined effects of head supported mass (e.g., Night Vision Goggles, head mounted displays) and whole-body vibration. This study examined the physiological responses of pilots during exposure to whole-body vibration (WBV) representative of the National Research Council’s Bell 412 helicopter in forward flight. WBV levels were measured and evaluated using the ISO-2631-1-1997 WBV standards.METHODS: Twelve pilots (aged 20–59 yr, 7 of the 12 with 20+ years flight experience) underwent six 15-min vibration trials on a human rated shaker platform. Participants were exposed to three vibration levels (-25%, normal, and +25% amplitude; Levels 1–3, respectively) while seated on an Original Equipment Manufacturer (OEM) or vibration mitigating (MIT) cushion. Upper back and neck electromyography (EMG) and acceleration were continuously recorded.RESULTS: Normalized EMG amplitude was higher using the OEM compared to the MIT during Level 2 (0.18 vs. -0.27) and Level 3 (0.24 vs. -0.14) for the anterior neck muscles. Health weighted vibration amplitude at the head (Mean of 3 levels: OEM = 1.19 and MIT = 1.11 m · s⁻²) was larger than the vibration amplitude at the seat (Mean of 3 levels: OEM = 0.77 and MIT = 0.70 m · s⁻²).DISCUSSION: The amplification of head vibration relative to the seat, and the significant effects of vibration level, as well as the vibration mitigation cushion, on neck EMG amplitude support the need for revisions to the ISO-2631-1 standard to account for the head and neck response to whole-body vibration.Wright Beatty HE, Law AJ, Thomas JR, Wickramasinghe V. Amplified pilot head vibration and the effects of vibration mitigation on neck muscle strain. Aerosp Med Hum Perform. 2018; 89(6):510–519.

BACKGROUND: Submarines routinely operate with higher levels of ambient carbon dioxide (CO₂) (i.e., 2000 – 5000 ppm) than what is typically considered normal (i.e., 400 – 600 ppm). Although significant cognitive impairments are rarely reported at these elevated CO₂ levels, recent studies using the Strategic Management Simulation (SMS) test have found impairments in decision-making performance during acute CO₂ exposure at levels as low as 1000 ppm. This is a potential concern for submarine operations, as personnel regularly make mission-critical decisions that affect the safety and efficiency of the vessel and its crew while exposed to similar levels of CO₂. The objective of this study was to determine if submariner decision-making performance is impacted by acute exposure to levels of CO₂ routinely present in the submarine atmosphere during sea patrols.METHODS: Using a subject-blinded balanced design, 36 submarine-qualified sailors were randomly assigned to receive 1 of 3 CO₂ exposure conditions (600, 2500, or 15,000 ppm). After a 45-min atmospheric acclimation period, participants completed an 80-min computer-administered SMS test as a measure of decision making.RESULTS: There were no significant differences for any of the nine SMS measures of decision making between the CO₂ exposure conditions.DISCUSSION: In contrast to recent research demonstrating cognitive deficits on the SMS test in students and professional-grade office workers, we were unable to replicate this effect in a submariner population—even with acute CO₂ exposures more than an order of magnitude greater than those used in previous studies that demonstrated such effects.Rodeheffer CD, Chabal S, Clarke JM, Fothergill DM. Acute exposure to low-to-moderate carbon dioxide levels and submariner decision making. Aerosp Med Hum Perform. 2018; 89(6):520–525.

BACKGROUND: The effects of acute mild hypoxic hypoxia (HH) and physical activity on physiological measures, signs and symptoms, mood, fatigue, cognition, and performance on a simulated flight task were investigated between 8000 (8K; 2438 m) and 14,000 ft (14K; 4267 m).METHOD: In a hypobaric chamber, 16 military helicopter pilots were randomly exposed to 4 altitudes and 3 physical exertion levels. After each exercise period, participants identified targets on a designated flight path on a desktop simulator and completed a cognitive test battery. Cerebral regional and finger pulse oxyhemoglobin saturation levels (rSO₂ and S_po₂), heart and respiration rates were continuously monitored. Participants indicated their symptoms, mood and fatigue.RESULTS: rSO₂ and S_po₂ were affected by the increase of altitude and exercise level. Target identification accuracy and latency within the simulated flight task showed decrements at 8K, 10K (3048 m), 12K (3658 m), and 14K. Cognitive performance was degraded at 14K. More than 60% of the participants at 8K and 10K and more than 80% at 12K and 14K reported symptoms. Altitude increased symptoms, negative mood, general fatigue, and physical fatigue.DISCUSSION: Our findings indicate a significant influence of mild HH on a number of outcome measures at altitudes above 10K, where operational restrictions are well established. In contrast, there was no clear influence of HH on performance at lower altitudes (i.e., 8K and 10K). The occurrence of HH symptoms and the decrements in target identification latency and accuracy at 8K and 10K may negatively impact flight performance and require further study.Bouak F, Vartanian O, Hofer K, Cheung B. Acute mild hypoxic hypoxia effects on cognitive and simulated aircraft pilot performance. Aerosp Med Hum Perform. 2018; 89(6):526–535.

INTRODUCTION: Future deep space missions will expose astronauts to more intense stressors than previously encountered. Isolation will be greater and more prolonged, living and work areas more confined, and communications and resupply channels to Earth longer and less reliable. Astronauts will need to function more autonomously, with less guidance and support from Earth. Thus, it is important to select and train astronauts who can adapt and function effectively under extreme and variable conditions. In order to identify factors linked to individual adaptability, we conducted a systematic review of the literature on cognitive and behavioral adaptation to isolated, confined, and extreme (ICE) environments.METHODS: We searched PubMed, Embase, Web of Science, and PsychINFO databases for studies addressing individual adaptability to ICE environments. Studies were rated for quality and fidelity to long-duration space missions and key results extracted.RESULTS: There were 73 studies that met all inclusion criteria. Adaptability attributes for ICE environments include intelligence, emotional stability, self-control, openness, achievement facets of conscientiousness, optimism, mastery, introversion, hardiness, task-oriented coping, past experience, low need for social support, and adequate sleep. DISCUSSION: This review identifies individual factors linked to adaptability under ICE conditions. Further studies are needed to verify causal directions and determine the relative importance of these factors.Bartone PT, Krueger GP, Bartone JV. Individual differences in adaptability to isolated, confined, and extreme environments. Aerosp Med Hum Perform. 2018; 89(6):536–546.

BACKGROUND: During ground operations, rotary-wing aircraft engines and subsystems produce noise hazards that place airfield personnel at risk for hearing damage. The noise exposure levels outside the aircraft during various operating conditions, and the distances from aircraft at which they drop to safe levels, are not readily available. The current study measured noise levels at various positions around the UH-60 Black Hawk helicopter for three operating conditions typically used when the aircraft is on the ground.METHODS: Microphones were positioned systematically around the helicopter and A-weighted sound pressure levels (SPLs) were computed from the recordings. In addition, the 85-dBA SPL contour around the aircraft was mapped. The resulting A-weighted SPLs and contour mapping were used to determine the noise hazard area around the helicopter.RESULTS: Measurements reported here show noise levels of 105 dB or greater in all operating conditions. The fueling location at the left rear of the aircraft near the auxiliary power unit (APU) is the area of greatest risk for noise-induced hearing loss (NIHL). Additionally, sound field contours indicate noise hazard areas (>85 dBA SPL) can extend beyond 100 ft from the helicopter.CONCLUSIONS: This report details the areas of greatest risk for auditory injury around the UH-60 Black Hawk helicopter. Our findings suggest the area of hazardous noise levels around the aircraft can extend to neighboring aircraft, particularly on the side of the aircraft where the APU is located. Hearing protection should be worn whenever the aircraft is operating, even if working at a distance.Jones HG, Greene NT, Chen MR, Azcona CM, Archer BJ, Reeves ER. The danger zone for noise hazards around the Black Hawk helicopter. Aerosp Med Hum Perform. 2018; 89(6):547–551.

BACKGROUND: The present study aimed to find out if possible differences in early military flight career +G_z exposure level could predict permanent flight duty limitations (FDL) due to spinal disorders during a pilot’s career.METHODS: The study population consisted of 23 pilots flying with G_z limitation (max limitation ranging from +2 G_z to +5 G_z) due to spinal disorders and 50 experienced (+1000 flight hours) symptomless controls flying actively in operative missions in the Finnish Air Force. Data obtained for all subjects included the level of cumulative G_z exposure measured sortie by sortie with fatigue index (FI) recordings and flight hours during the first 5 yr of the pilot’s career.RESULTS: The mean (± SD) accumulation of FI in the first 5 yr of flying high-performance aircraft was 8.0 ± 1.8 among the pilots in the FDL group and 7.7 ± 1.7 in the non-FDL group. There was no association between flight duty limitations and early career cumulative +G_z exposure level measured with FI or flight hours.DISCUSSION: According to the present findings, it seems that the amount of cumulative +G_z exposure during the first 5 yr of a military pilot’s career is not an individual risk factor for spinal disorders leading to flight duty limitation. Future studies conducted with FI recordings should be addressed to reveal the relationship between the actual level of +G_z exposure and spinal disorders, with a longer follow-up period and larger sample sizes.Honkanen T, Sovelius R, Mäntysaari M, Kyröläinen H, Avela J, Leino TK. +Gz exposure and spinal injury-induced flight duty limitations. Aerosp Med Hum Perform. 2018; 89(6):552–556.

BACKGROUND: This paper discusses a special kind of a sensory illusion—the Giant Hand illusion—that was experienced during an exercise on a flight simulator equipped with a VR headset. In the first part we describe spatial disorientation and the function of the vestibular apparatus during flight and its consequences. In this part, the sensory illusion simulator used for the experiment is mentioned. In the second part we describe the simulator and test flight. In the third part we discuss data retrieved during simulator flights that are important for explaining the Giant Hand illusion.CASE REPORT: A well-trained pilot experienced the Giant Hand illusion while executing instrument flight rules flight on a simulator. The Giant Hand illusion was detected from the simulation data and confirmed by the pilot afterward.DISCUSSION: The Giant Hand illusion is a rare type of sensory illusion. The pilot falsely evaluated the situation as a malfunction of the aircraft controls. If the pilot had not been informed by the operator that he might have been influenced by the illusion, he would probably have crashed the simulated aircraft. An unrecognized Giant Hand illusion during a flight can lead to fatal consequences. This case report shows the symptoms and data that can be used for early recognition of this type of illusion.Frantis P, Petru A. The Giant Hand illusion experienced on a simulator. Aerosp Med Hum Perform. 2018; 89(6):557–562.

INTRODUCTION: The purpose of this study was to analyze posterior-to-anterior spinal stiffness in Earth, hyper-, and microgravity conditions during both prone and upright postures. CASE REPORT: During parabolic flight, the spinal stiffness of the L3 vertebra of a healthy 37-yr-old man was measured in normal Earth gravity (1.0 g), hypergravity (1.8 g), and microgravity (0.0 g) conditions induced in the prone and upright positions. Differences in spinal stiffness were significant across all three gravity conditions in the prone and upright positions. Most effect sizes were large; however, in the upright posture, the effect size between Earth gravity and microgravity was medium. Significant differences in spinal stiffness between the prone and upright positions were found during Earth gravity and hypergravity conditions. No difference was found between the two postures during microgravity conditions. DISCUSSION: Based on repeated measurements of a single individual, our results showed detectable changes in posterior-to-anterior spinal stiffness. Spinal stiffness increased during microgravity and decreased during hypergravity conditions. In microgravity conditions, posture did not impact spinal stiffness. More data on spinal stiffness in variable gravitational conditions is needed to confirm these results. Swanenburg J, Meier ML, Langenfeld A, Schweinhardt P, Humphreys BK. Spinal stiffness in prone and upright postures during 0–1.8 g induced by parabolic flight. Aerosp Med Hum Perform. 2018; 89(6):563–567.

Holmes RL. You’re the flight surgeon: zika virus infection. Aerosp Med Hum Perform. 2018; 89(6):572–575.