INTRODUCTION: The Psychomotor Vigilance Test (PVT) measures effects of fatigue from sleep loss and circadian misalignment on sustained vigilance performance. To promote PVT use in field environments, a 5-min PVT version has been implemented on a personal digital assistant (PDA) with a touch screen. The present laboratory study was conducted to validate this PVT against a standard 10-min laptop PVT across 38 h of total sleep deprivation (TSD).METHODS: Following a baseline sleep night, subjects underwent 38 h of TSD, during which they performed the PVT every hour, alternating between the two test platforms. The study concluded with a night of recovery sleep.RESULTS: The primary outcome was the number of PVT lapses (reaction times > 500 ms). Both PVT platforms showed significant effects for the number of lapses across TSD test times involving an increase with time awake modulated by circadian rhythm. Laptop PVT lapses across test times exhibited a large effect size (f₂ = 0.36), whereas PDA PVT lapses exhibited a medium effect size (f₂ = 0.17). The laptop PVT showed a significant effect for the number of false starts during TSD similar to the temporal profile of lapses, while the PDA PVT had false starts throughout the TSD period.DISCUSSION: The 5-min PDA PVT provided performance testing functionality and results comparable to the 10-min laptop PVT. The number of PDA PVT lapses tracked fatigue similarly to the laptop PVT lapses, albeit with smaller average ranges and effect sizes.Honn KA, Riedy SM, Grant DA. Validation of a portable, touch-screen psychomotor vigilance test. Aerosp Med Hum Perform. 2015; 86(5):428–434.

BACKGROUND: Sea travel leads to well-known changes in gait, but these effects have not been evaluated using quantitative data obtained through controlled experiments. We obtained quantitative data on step-timing patterns as experienced maritime crewmembers walked on a ship at sea.METHODS: Using a within-subjects design, crewmembers walked back and forth along straight line paths (11 m long) that were parallel with the ship’s long (i.e., fore-aft) and short (i.e., athwart) axes. Using contact switches attached to the feet, we measured temporal parameters of gait, including stride time, the variability of stride time, and the coefficient of variation. We also evaluated the temporal dynamics of stride times using detrended fluctuation analysis.RESULTS: The variability of stride time differed between walking fore-aft (mean = 0.10 s) and walking athwart (mean = 0.28 s). The coefficient of variation also differed between walking fore-aft (mean = 11%) and walking athwart (mean = 43%).CONCLUSIONS: We obtained direct evidence that ship motions in roll and pitch differentially affect the timing of stepping patterns in human gait. This novel finding motivates new research on quantitative parameters of gait at sea.Haaland E, Kaipust J, Wang Y, Stergiou N, Stoffregen TA. Human gait at sea while walking fore-aft vs. athwart. Aerosp Med Hum Perform. 2015; 86(5):435–439.

BACKGROUND: The most commonly cited hypotheses for motion sickness (MS) focus on inconsistent sensory inputs. Visual/vestibular conflicts may lead to MS, but visual input from retinal regions/neural pathways that are sensitive to motion might bear more weight in MS etiology. We hypothesized that inducing blurred vision in an optokinetic drum would attenuate the influence of foveal (parvocellular) input, but not peripheral (magnocellular) input that is sensitive to motion. Increased relative influence of peripheral visual input was predicted to subsequently lead to more visual/vestibular conflict and subsequently more severe MS symptoms.METHODS: Through goggles that were either clear or frosted, 15 subjects (5 men, 10 women, mean age = 24.9 yr, range = 18-49) viewed the interior of a rotating (60° · s⁻¹) optokinetic drum for 10 min. Subjects completed the Simulator Sickness Questionnaire (SSQ) before and after viewing. Overall subjective sickness ratings (0-10) and visually induced self-motion perception (vection) ratings (0-10) were also recorded.RESULTS: Postexposure SSQ scores obtained in the blur condition (total - 52.9, oculomotor - 38.9, disorientation - 69.6) were significantly higher than those obtained in the control condition (total - 30.4, oculomotor - 21.7, disorientation - 37.8). Overall sickness ratings and vection ratings were also significantly higher in the blur condition.CONCLUSIONS: These results suggest that visual blur can exacerbate MS, perhaps because of differential influences of visual pathways. Although these results were obtained with an optokinetic drum, possible effects of visual blurring in motion provocative environments such aircraft, watercraft, spacecraft, and land vehicles should be considered.Bonato F, Bubka A, Thornton W. Visual blur and motion sickness in an optokinetic drum. Aerosp Med Hum Perform. 2015; 86(5):440–444.

BACKGROUND: There is a high prevalence of neck pain in air force pilots; however, the causes are not clear and are considered work-related. Kyphotic changes in the cervical spine have been known to cause neck pain. In this study, we investigated the association between neck pain and cervical kyphosis in air force pilots.METHODS: This is a cross-sectional study of 63 Republic of South Korea Air Force pilots. We examined the C2-7 absolute rotation angle (ARA) using the posterior tangent method and other radiologic parameters on whole spine lateral radiographs. We divided the participants into a neck pain group (N = 32) and no neck pain group (N = 31), and subsequently analyzed the difference in radiographic parameters and clinical data between the two groups.RESULTS: There were no significant differences found in age, body mass index, total flight time, or aerobic or anaerobic exercise between the neck pain and control groups. The fighter pilots had higher 1-yr prevalence of neck pain than nonfighter pilots (84.4% vs. 15.6%). The lower C2-7 ARA (OR = 0.91, 95% CI 0.846, 0.979) and fighter type aircrafts (OR = 3.93, 95% CI 1.104, 13.989) were associated with neck pain.CONCLUSIONS: Fighter pilots experienced neck pain more frequently than the nonfighter pilots. Those fighter pilots suffering from neck pain were shown to have more kyphotic changes in the cervical spine than control pilots through evaluation of whole spine lateral radiographs using the posterior tangent method. These key findings suggest that the forces involved in flying a fighter type aircraft may affect cervical alignment and neck pain.Moon BJ, Choi KH, Yun C, Ha Y. Cross-sectional study of neck pain and cervical sagittal alignment in air force pilots. Aerosp Med Hum Perform. 2015; 86(5):445–451.

BACKGROUND: Motion sickness is an unpleasant physiological state that may be controlled via nonpharmacological methods. Controlled breathing has been shown to maximize parasympathetic nervous system (PNS) tone and may have the ability to decrease motion sickness symptoms.METHODS: The effects of slow diaphragmatic breathing (DB) in a motion sickness-inducing environment were examined within motion sickness susceptible individuals. Subjects (N = 43) were assigned randomly to either an experimental group trained in slow DB or a control group breathing naturally at a normal pace. The experimental group was trained using a digital video that helped them pace their diaphragmatic breathing at six breaths/min. During the study, subjects viewed a virtual reality (VR) experience of a boat in rough seas for 10 min. Motion sickness ratings along with heart rate and respiration rate were collected before, during, and after the VR experience.RESULTS: Results indicated that the experimental group was able to decrease their breathing to eight breaths/min during the VR experience. This breathing rate was significantly slower than those in the control group. We found that DB subjects, compared to those in the control group, displayed significantly greater heart rate variability and reported feeling less motion sickness during exposure to the VR experience than those in the control group.DISCUSSION: Results indicate possible benefits of using slow DB techniques in a motion sickness inducing environment.Stromberg SE, Russell ME, Carlson CR. Diaphragmatic breathing and its effectiveness for the management of motion sickness. Aerosp Med Hum Perform. 2015; 86(5):452–457.

OBJECTIVE: To study associations between the cockpit environment, psychosocial work environment, home environment, and medical symptoms in a cohort of commercial pilots followed over 3 yr.METHODS: A standardized questionnaire was mailed in February-March 1997 to all Stockholm-based pilots on duty in a Scandinavian flight company (N = 622); 577 (93%) participated. During this time smoking was allowed on long haul flights, but not on shorter flights. Smoking was prohibited on all flights after September 1997. The same questionnaire was sent to the cohort of 577 pilots in February-March 2000; 436 participated (76%). The questionnaire contained questions on symptoms, the psychosocial work environment, and the home environment. Associations were investigated using multiple logistic and ordinal regression.RESULTS: Symptoms were common, especially eye symptoms (38.5%), nose symptoms (39.9%), and tiredness (29.9%). Pilots exposed to environmental tobacco smoke (ETS) on long haul flights had more eye symptoms (odds ratio = 1.91) and tiredness (odds ratio = 2.73). These symptoms were reduced when no longer exposed to ETS. Those who started working on long haul flights developed more nose symptoms. Pilots reporting increased work demands developed more nose and dermal symptoms and tiredness and those with decreased work control developed more eye symptoms. Pilots living in new houses, multifamily houses, and in recently painted homes reported more symptoms.CONCLUSION: Eliminating ETS exposure on board reduced medical symptoms. Further work to reduce ETS exposure globally is needed. Psychosocial aspects of the work environment for commercial pilots should be considered, as well as the home environment.Fu X, Lindgren T, Norbäck D. Medical symptoms among pilots associated with work and home environments: a 3-year cohort study. Aerosp Med Hum Perform. 2015; 86(5):458–465.

INTRODUCTION: Modern super agile fighter aircraft are capable of producing an increasing multiaxial acceleration environment which can adversely affect the pilot. An evaluation of the performance of the restraint system during flight maneuvers will benefit restraint designs and, thus, the safety of pilots.METHODS: A finite element model of a mannequin with PCU-15/P harness restraint was used in this study to investigate how the factors, such as strap material stiffness, friction, and belt tension, affect the performance of restraint systems during impact along the −G_x, −G_y, and −G_z directions. The corresponding maximum displacement of the mannequin's torso was computed.RESULTS: The mannequin moved beyond 74 mm sideways. The change in friction coefficient (FC) from 0.1 to 0.4 decreased the displacement of the lower torso by less than 6.7%. The displacement of the torso decreased as the stiffness of the strap or tension increased. Displacement decreased by 9.3%, 6.0%, and 2.7% for the lower torso under the G_x impact, as the tightening force increased from 20 N to 80 N gradually. However, this changed slightly when the stiffness arrived at 1 E or the tension increased to 60 N.DISCUSSION: PCU-15/P harness has the poorest performance during side impact and friction plays an unimportant role in affecting its performance. The stiffness of the webbing used in the PCU-15/P harness is sufficiently high. The lap belt has more effect on limiting the movement of the pilot than the shoulder straps, and a tension of 60 N during the adjustment may be enough for conventional flight maneuvers.Du C-F, Liu X-Y, Wang L-Z, Liu S-Y, Fan Y-B. Restraint harness performance during flight maneuvers: a parametric study. Aerosp Med Hum Perform. 2015; 86(5):466–471.

BACKGROUND: There is a close physiological connection between muscular activity and kidney function. During physical exercise (PE) the qualitative and quantitative composition of urine changes. This paper explores the influence of moderate PE on urine protein composition. The study of urine protein composition will help to make corrections to the existing methods of countermeasures.METHODS: There were 10 healthy men who exercised on a treadmill similar to the one onboard the International Space Station. We analyzed their urinary proteome composition, potassium level, sodium level, and their level of osmotically active substances before and after PE.RESULTS: After moderate PE, a small increase in urine flow speed and a constant glomerular filtration rate were noted. The average-group index of total protein excretion within the urine was reliably increased. From the 148 proteins identified in the urine, 64 were associated with known tissue origin. We found that protein penetration into the urine had a positive correlation with their tissue expression. Selectivity of the glomerular barrier during PE decreased and high-molecular weight proteins penetrated through the glomerular barrier more easily after PE.DISCUSSION: Performance of moderate intensity physical exercise of short duration did not lead to an increase in the glomerular filtration rate nor did diuresis increase above the limits of baseline variability. However, the protein excretion rate increased after PE. We also observed that protein composition drift indicated a change in the set of biological processes in which a given protein participated, in some cases activating, in some cases inactivating them.Fomina EV, Lisova NIu, Kireev KS, Tiys ES, Kononikhin AS, Larina IM. Kidney function and urine protein composition in healthy volunteers during space station fitness tests. Aerosp Med Hum Perform. 2015; 86(5):472–476.

BACKGROUND: Incidental findings pose a dilemma in aviation medicine, where every finding must be carefully considered in order to ensure the well-being of the aircrew for flight and mission safety. Since suprasellar masses are not uncommon, their possible effects should be addressed.CASE REPORT: We present an incidental finding of 11.5 mm × 14.4 mm, hyper-intense on T2 and iso-intense on T1-weighted images, of a suprasellar mass in a 19-yr-old man. This finding led to the re-evaluation of his position as a military flight cadet, followed by his later disqualification.DISCUSSION: No medical waiver regarding asymptomatic suprasellar mass exists. We have carefully examined the differential diagnosis and generated a profile for each possible diagnosis consisting of risks for sudden incapacitation, progression likelihood, and the effect of an aerial environment on a brain lesion. We were able to draw up a medical waiver for some of the possible diagnoses (namely, Rathke’s cyst or craniopharyngioma) for nonhigh performance aircraft.Doron O, Carmon E. An incidental suprasellar mass in a military flying cadet: implications for aircrew. Aerosp Med Hum Perform. 2015; 86(5):477–480.

BACKGROUND: Sleep deprivation is known to be a common problem in the U.S. Navy and has been documented using wrist-worn actigraphy in various operational studies that typically span 2 to 4 wk in duration. However, sleep patterns over an extended period of time have not been objectively measured.CASE REPORT: This 6-mo study used actigraphy and the Fatigue Avoidance Scheduling Tool (FAST) to quantify the sleep patterns of a 39-yr-old Commanding Officer (CO) of an Arleigh Burke class destroyer while the ship was forward-deployed. On average, the CO received 5.2 h of sleep daily and averaged 6 h time in bed each day. The participant received more than 8 h of sleep for only 2% (N = 3) of the study days; for 17% (N = 27) of the days, he received less than 4 h of daily sleep. For 15% of waking time, the CO had a predicted effectiveness of less than 70% on the FAST scale, equating to a blood alcohol equivalent of 0.08%—or legally drunk. The CO’s predicted effectiveness was below 65% approximately 10% of waking time.DISCUSSION: Results from this study are aligned with earlier research showing that crewmembers on U.S. Navy ships suffer from chronic sleep restriction. During a typical deployment, personnel accrue a considerable sleep debt even during normal operations. Should critical events with additional sleep restriction occur, the ship has limited reserve capacity, potentially placing her crew and their mission in grave jeopardy.Shattuck NL, Matsangas P. A 6-month assessment of sleep during naval deployment: a case study of a commanding officer. Aerosp Med Hum Perform. 2015; 86(5):481–485.

INTRODUCTION: Medical Guidelines for Airline Travel provide information that enables healthcare providers to properly advise patients who plan to travel by air. Modern commercial aircraft are very safe and, in most cases, reasonably comfortable. However, all flights, short or long haul, impose stresses on passengers. Preflight stresses include airport commotion on the ground such as carrying baggage, walking long distances, getting to the gate on time, and being delayed. In-flight stresses include acceleration, vibration (including turbulence), noise, lowered barometric pressure, variations of temperature and humidity, and fatigue among others. Healthy passengers normally tolerate these stresses quite well; however, there is the potential for passengers to become ill during or after the flight due to these stresses, especially for those with pre-existing medical conditions and reduced physiological reserves.Thibeault C, Evans AD. AsMA medical guidelines for air travel: stresses of flight. Aerosp Med Hum Perform. 2015; 86(5):486–487.

Howard CT, Vu P. You're the flight surgeon: hand, foot, and mouth disease. Aerosp Med Hum Perform. 2015; 86(5):497–500.

Woolford JS. You're the flight surgeon: epilepsy. Aerosp Med Hum Perform. 2015; 86(4):500–503.