INTRODUCTION: Astronauts undergo CO₂ exposure training to recognize their symptoms that can arise acutely both on the ground and in spaceflight. This article describes acute CO₂ exposure training at NASA and examines the symptoms reported by astronauts during training.METHODS: In a controlled training environment, astronauts are exposed to up to 8% CO₂ (60 mmHg) by a rebreathing apparatus. Symptoms are reported using a standard form.RESULTS: Symptom documentation forms between April 1994 and February 2012 were obtained for 130 astronauts. The number of symptoms reported per session out of the possible 24 was related to age and sex, with those older slightly more likely to report symptoms. Women reported more symptoms on average than men (men: 3.7, women: 4.7). Respiratory symptoms (90%), flushing sensation/sweating (56%), and dizziness/feeling faint/lightheadedness (43%) were the top symptoms. Only headache reached statistical significance in differences between men (13%) and women (37%) after adjustment for multiple testing. Among those with multiple training sessions, respiratory symptoms were the most consistently reported.DISCUSSION: CO₂ exposure training is an important tool to educate astronauts about their potential acute CO₂ symptoms. Wide interindividual and temporal variations were observed in symptoms reported during astronaut CO₂ exposure training. Headache could not be relied on as a marker of acute exposure during testing since fewer than half the subjects reported it. Our results support periodic refresher training since symptoms may change over time. Further study is needed to determine the optimal interval of training to maximize symptom recognition and inform operational decisions.Law J, Young M, Alexander D, Mason SS, Wear ML, Méndez CM, Stanley D, Meyers Ryder V, Van Baalen M. Carbon dioxide physiological training at NASA. Aerosp Med Hum Perform. 2017; 88(10):897–902.

BACKGROUND: Astronauts’ orientation preferences tend to correlate with their susceptibility to space motion sickness (SMS). Orientation preferences appear universally, since variable sensory cue priorities are used between individuals. However, SMS susceptibility changes after proper training, while orientation preferences seem to be intrinsic proclivities. The present study was conducted to investigate whether orientation preferences change if susceptibility is reduced after repeated exposure to a virtual reality (VR) stimulus environment that induces SMS.METHODS: A horizontal supine posture was chosen to create a sensory context similar to weightlessness, and two VR devices were used to produce a highly immersive virtual scene. Subjects were randomly allocated to an experimental group (trained through exposure to a provocative rotating virtual scene) and a control group (untrained). All subjects’ orientation preferences were measured twice with the same interval, but the experimental group was trained three times during the interval, while the control group was not.RESULTS: Trained subjects were less susceptible to SMS, with symptom scores reduced by 40%. Compared with untrained subjects, trained subjects’ orientation preferences were significantly different between pre- and posttraining assessments. Trained subjects depended less on visual cues, whereas few subjects demonstrated the opposite tendency.CONCLUSION: Results suggest that visual information may be inefficient and unreliable for body orientation and stabilization in a rotating visual scene, while reprioritizing preferences for different sensory cues was dynamic and asymmetric between individuals. The present findings should facilitate customization of efficient and proper training for astronauts with different sensory prioritization preferences and dynamic characteristics.Chen W, Chao J-G, Zhang Y, Wang J-K, Chen X-W, Tan C. Orientation preferences and motion sickness induced in a virtual reality environment. Aerosp Med Hum Perform. 2017; 88(10):903–910.

BACKGROUND: Hypoxia and exercise each exhibit opposing effects on executive function, and the mechanisms for this are not entirely clear. This study examined the influence of cerebral oxygenation and perfusion on executive function during exercise and recovery in normobaric hypoxia (NH) and normoxia (N).METHODS: There were 18 subjects who completed cycling trials in NH (12.5% F_Io₂) and N (20.93% F_Io₂). Right prefrontal cortex (PFC) oxyhemoglobin (O₂Hb) and middle cerebral artery blood velocity (MCAbv) were collected during executive function challenges [mathematical processing and running memory continuous performance task (RMCPT)] at baseline, following 30 min of acclimation, during 20 min of cycling (60% Vo_2max), and at 1, 15, 30, and 45 min following exercise.RESULTS: Results indicated effects of time for Math, RMCPT, and O₂Hb; but not for MCAbv. Results also indicated effects of condition for O₂Hb. Math scores were improved by 8.0% during exercise and remained elevated at 30 min of recovery (12.5%), RMCPT scores significantly improved at all time points (7.5–11.9%), and O₂Hb increased by 662.2% and 440.9% during exercise in N and NH, respectively, and remained elevated through 15 min of recovery in both conditions.DISCUSSION: These results support the influence of PFC oxygenation and perfusion on executive function during exercise and recovery in N and NH.Stavres J, Gerhart HD, Kim J-H, Glickman EL, Seo Y. Cerebral hemodynamics and executive function during exercise and recovery in normobaric hypoxia. Aerosp Med Hum Perform 2017; 88(10):911–917.

INTRODUCTION: Medical Emergency Response Team (MERT) helicopters fly at altitudes of 3000 m in Afghanistan (9843 ft). Civilian hospitals and disaster-relief surgical teams may have to operate at such altitudes or even higher. Mild hypoxia has been seen to affect the performance of novel tasks at flight levels as low as 5000 ft. Aeromedical teams frequently work in unpressurized environments; it is important to understand the implications of this mild hypoxia and investigate whether supplementary oxygen systems are required for some or all of the team members.METHODS: Ten UK orthopedic surgeons were recruited and in a double blind randomized experimental protocol, were acutely exposed for 45 min to normobaric hypoxia [fraction of inspired oxygen (F_Io₂) ∼14.1%, equivalent to 3000 m (10,000 ft)] or normobaric normoxia (sea-level). Basic physiological parameters were recorded. Subjects completed validated tests of verbal working memory capacity (VWMC) and also applied an orthopedic external fixator (Hoffmann^® 3, Stryker, UK) to a plastic tibia under test conditions.RESULTS: Significant hypoxia was induced with the reduction of F_Io₂ to ∼14.1% (S_po₂ 87% vs. 98%). No effect of hypoxia on VWMC was observed. The pin-divergence score (a measure of frame asymmetry) was significantly greater in hypoxic conditions (4.6 mm) compared to sea level (3.0 mm); there was no significant difference in the penetrance depth (16.9 vs. 17.2 mm). One hypoxic frame would have failed early.DISCUSSION: We believe that surgery at an altitude of 3000 m, when unacclimated individuals are acutely exposed to atmospheric hypoxia for 45 min, can likely take place without supplemental oxygen use but further work is required.Parker PJ, Manley AJ, Shand R, O’Hara JP, Mellor A. Working memory capacity and surgical performance while exposed to mild hypoxic hypoxemia. Aerosp Med Hum Perform. 2017; 88(10):918–923.

INTRODUCTION: This study aimed to assess changes in common carotid (CA) and superficial femoral (FA) arterial stiffness during long-duration spaceflight.METHODS: Ultrasound imaging was used to investigate the CA and FA of 10 astronauts preflight (PRE), on flight day 15 (FD15), after 4–5 mo (FD4–5m), and 4 d after return to Earth (R+4). Arterial wall properties were assessed through the calculation of strain, stiffness (β), pressure-strain elastic modulus (Ep), and distensibility (DI). Stiffness indices were assessed for potential correlations to measurements of intima-media thickness (IMT).RESULTS: Significant effects of spaceflight were found for all CA stiffness indices, indicating an increase in arterial stiffness. CA strain was reduced by 34 ± 31% on FD15 and 50 ± 16% on FD4–5m and remained reduced by 42 ± 14% on R+4 with respect to PRE values. On FD4–5m, with respect to PRE values, DI was reduced by 46 ± 25% and β and Ep were increased by 124 ± 95% and 118 ± 92%, respectively. FA arterial stiffness indices appeared to show similar changes; however, a main effect of spaceflight was only found for strain. Correlation analysis showed weak but significant relationships between measurements of CA IMT and arterial stiffness indices, but no relationships were found for FA measurements.DISCUSSION: The observed change in CA and FA stiffness indices suggest that spaceflight results in an increase in arterial stiffness. That these changes were not strongly related to measurements of IMT suggests the possibility of different mechanisms contributing to the observed results.Arbeille P, Provost R, Zuj K. Carotid and femoral arterial wall distensibility during long-duration spaceflight. Aerosp Med Hum Perform. 2017; 88(10):924–930.

INTRODUCTION: This study examined the association between mean age of pilot, pilot license, pilot medical certificate and drug use trends in pilots fatally injured in aircraft accidents. The prevalence of prescription drugs, OTC drugs, controlled drugs and drugs that may be potentially impairing was also examined.METHODS: This study was a descriptive observational study in which the NTSB Aviation Accident Database was searched from the period beginning January 1, 2012 to December 31, 2014.RESULTS: During the study period a total of 706 accidents involving 711 fatalities were investigated by the NTSB. This study included 633 of these accidents, involving 646 fatalities. Of these pilots, 42.1% had drugs in their biological samples. The prevalence of prescription drugs, controlled drugs, OTC drugs, opioids, and potentially impairing drugs in the fatally injured pilot population over the study period was 28.9%, 15.0%, 20.1%, 5.1%, and 25.5%, respectively. Pilots with any drugs in their samples were significantly older than those without drugs. Medical certificate held was associated with drug use; pilots who held third class certificates had the highest prevalence at 54.1%. Pilot license was not associated with drug use. In 3.8% of the accidents, drugs were a contributing factor in the cause.DISCUSSION: Despite current FAA medical regulations, potentially impairing drugs are frequently found in biological samples of fatally injured pilots in the U.S. More education of airmen by aviation medical examiners is needed on the safety of drug use.Akparibo IY, Stolfi A. Pilot certification, age of pilot, and drug use in fatal civil aviation accidents. Aerosp Med Hum Perform. 2017; 88(10):931–936.

BACKGROUND: Neuropsychological changes that may occur due to the environmental and psychological stressors of prolonged spaceflight motivated the development of the Cognition Test Battery. The battery was designed to assess multiple domains of neurocognitive functions linked to specific brain systems. Tests included in Cognition have been validated, but not in high-performing samples comparable to astronauts, which is an essential step toward ensuring their usefulness in long-duration space missions.METHODS: We administered Cognition (on laptop and iPad) and the WinSCAT, counterbalanced for order and version, in a sample of 96 subjects (50% women; ages 25–56 yr) with at least a Master’s degree in science, technology, engineering, or mathematics (STEM). We assessed the associations of age, sex, and administration device with neurocognitive performance, and compared the scores on the Cognition battery with those of WinSCAT. Confirmatory factor analysis compared the structure of the iPad and laptop administration methods using Wald tests.RESULTS: Age was associated with longer response times (mean β = 0.12) and less accurate (mean β = −0.12) performance, women had longer response times on psychomotor (β = 0.62), emotion recognition (β = 0.30), and visuo-spatial (β = 0.48) tasks, men outperformed women on matrix reasoning (β = −0.34), and performance on an iPad was generally faster (mean β = −0.55). The WinSCAT appeared heavily loaded with tasks requiring executive control, whereas Cognition assessed a larger variety of neurocognitive domains.DISCUSSION: Overall results supported the interpretation of Cognition scores as measuring their intended constructs in high performing astronaut analog samples.Moore TM, Basner M, Nasrini J, Hermosillo E, Kabadi S, Roalf DR, McGuire S, Ecker AJ, Ruparel K, Port AM, Jackson CT, Dinges DF, Gur RC. Validation of the Cognition Test Battery for spaceflight in a sample of highly educated adults. Aerosp Med Hum Perform. 2017; 88(10):937–946.

INTRODUCTION: Epidemiological studies suggest that pilots and cabin crew have higher incidences and mortality rates of cutaneous malignant melanoma than those of the general population. Exposure to UV radiation is one of the main risk factors for this type of cancer. The aim of this study was to evaluate the level of UV radiation in an airliner in flight.METHODS: Measurements were taken with a three sensor-integrated electronics UV radiometer (A, B, and C) during 14 flights from July to October 2016. They were performed during daylight hours once the airliner had reached cruising altitude.RESULTS: We failed to find UVC radiation. The measurements detected neither UV A nor B in any parts of the cabins of the planes tested, nor in the Airbus cockpits. UVA radiation was however found in the cockpit of Boeing 777s. But UVA levels remained well below the values found at ground level and they were also strongly reduced (more than 10 times) by cockpit sun visors.DISCUSSION: Few studies have assessed the level of UV radiation in an airplane. They suggested that the cockpit windshields reduced this type of radiation to some degree (according mainly to the wavelength of the radiation and the nature of the windshield). Our study strongly confirms these results and suggests that increased incidence of melanoma and mortality by this type of illness found among pilots and airline cabin crews may not be related to in-flight UV radiation exposure.Cadilhac P, Bouton M-C, Cantegril M, Cardines C, Gisquet A, Kaufman N, Klerlein M. In-flight ultraviolet radiation on commercial airplanes. Aerosp Med Hum Perform 2017; 88(10):947–951.

INTRODUCTION: A recent U-2 fatigue study, in which 10 subjects completed 2 simulated long-duration missions breathing either 100% oxygen or air in a hypobaric chamber, offered an opportunity to compare subjects’ pulmonary function before and after remaining seated in a confined cockpit for 12 h.METHODS: In one U-2 mission configuration, the subject wore a full pressure suit and breathed aviator’s breathing oxygen while chamber pressure was maintained at 4572 m (15,000 ft) above mean sea level. In the second mission configuration, subjects wore standard aircrew flight equipment and breathed air while chamber pressure was maintained at 2438 m (8000 ft) above mean sea level. Subjects’ pulmonary function was assessed before and after the mission using four metrics: forced vital capacity, forced expiratory volume in 1 s, peak expiratory flow, and forced expiratory volume in 1 s/forced vital capacity ratio.RESULTS: Subjects showed significant declines for all four pulmonary metrics (2.7%, 6.4%, 13.9%, and 3.5%, respectively) after 12 h seated in the cockpit in both full pressure suit and aircrew flight equipment conditions.DISCUSSION: While the declines at both altitudes amounted to modest percentages of subjects’ total pulmonary capacities, they emerged after a single, acute sedentary exposure and appear to be unrelated to the percentage of oxygen in the breathing gas. This might have operational implications in confined mission environments where physiological demands are interspersed with long periods of inactivity.Beer J, Dart TS, Fischer J, Kisner J. Pulmonary effects from a simulated long-duration mission in a confined cockpit. Aerosp Med Hum Perform. 2017; 88(10):952–957.

BACKGROUND: ''Cannon ball'' opacities on chest X-rays are a common manifestation of hematogenous dissemination of a malignant tumor in the lungs. They indicate an advanced stage of disease with a very grim prognosis in terms of cure and survival. In aerospace medicine, this aspect means the patient is unfit for flight duties. Nonmetastatic etiologies of pulmonary nodules are rare. We report a case of cannon ball opacities discovered fortuitously during an admission visit.CASE REPORT: A 23-yr-old flight attendant candidate came to the Aeromedical Expertise Center of the Military Hospital in Rabat for medical evaluation. He had no previous medical comorbidities and was asymptomatic. The physical examination was unremarkable. Chest X-ray revealed multiple poorly defined pulmonary nodular opacities, without mediastinal widening. After excluding other possibilities, such as infection or malignancy, the diagnosis of a pseudotumoral form of thoracic sarcoidosis was established by clinical and radiological findings, supported by histopathologic analysis.DISCUSSION: The pseudotumoral form of sarcoidosis is rare. It is usually seen in young people who are asymptomatic. Chest X-ray shows bilateral nodular opacities of different sizes. CT scan shows snowballs, which may or may not manifest with air bronchogram or mediastinal lymph nodes. Laboratory investigations are nonspecific. Pulmonary functions are normal or may show a restrictive pattern. Evolution is spontaneously favorable and does not require any treatment in asymptomatic patients. Aeromedical fitness in sarcoidosis disease depends on several conditions. This observation affirms the benefit of routine chest X-ray during medical evaulations to detect possible entities that may endanger flight safety.Zerrik M, Echchachoui H, Iloughmane Z, El’mhadi C, Elkhader S, Benaissa L, Chemsi M. Cannon ball diagnosis and management in a flight attendant candidate. Aerosp Med Hum Perform. 2017; 88(10):958–961.

BACKGROUND: A syrinx is a fluid-filled cavity within the spinal cord. They can lead to a variety of symptoms, including limb weakness and back pain. Incidental finding of syringomyelia provides a challenge for clinicians due to the wide variety of possible symptoms. In military aviation, neurological findings in pilots can result in extensive investigation that can lead to potentially invasive management. Conversely, the potential for chronic progression of a spinal syrinx and subsequent neurological deterioration makes early identification critical. Ultimately, the discovery of a lesion may have implications for flying status and operational capability.CASE REPORT: A 25-yr-old man working as a navy Seahawk helicopter pilot presented with episodes of right arm paraesthesia and pain between the scapulae. On at least one occasion, these symptoms woke him at night. Upon magnetic resonance imaging, dilatation of the central canal in a syrinx-like pattern in the lower cervical region was noted. Neurology review suggested the finding was persistent and unlikely to be responsible for his symptoms. No surgical input was recommended. His symptoms were attributed to mild cervical spondylosis, which resolved with ongoing physiotherapy, and he was returned to flying status.DISCUSSION: This case highlights several issues involved with the incidental finding of a syringomyelia. Surgical intervention has been known to worsen symptoms. Conversely, studies have identified minimal radiological progression in cases of idiopathic syringomyelia, with fewer individuals displaying neurological deterioration. For aircrew, potentially unnecessary neurosurgical intervention poses risks to a flying career and overall operational capability.Schiemer A. Idiopathic syringomyelia in a military helicopter pilot. Aerosp Med Hum Perform. 2017; 88(10):962–965.

Woolley RB. You’re the flight surgeon: hypertension. Aerosp Med Hum Perform. 2017; 88(10):967–970.

McCoy RP. You’re the flight surgeon: myxopapillary ependymoma. Aersop Med Hum Perform. 2017; 88(10):970–973.