INTRODUCTION: Urinary calcium (Uca) levels in space reflect bone loss and kidney stone risk and could be measured using portable devices. This project evaluated the repeatability of Uca measurements to assess how many repeated measurements would be needed to detect significant urinary calcium elevations in space.METHODS: A total of six subjects collected 24-h urine samples weekly for 8 wk and took 500 mg of oral calcium carbonate and 400 IU of vitamin D daily in week 7 and 8. Uca concentration was analyzed using a calcein-based system. The effect of the intake of calcium and vitamin D on Uca levels and the correlation between first void concentration and 24-h mass were assessed with linear mixed effect models. The reproducibility coefficient (RPC) for Uca was determined using Bland-Altman analysis on pairs of measurements at different time points.RESULTS: Oral supplementation did not significantly affect 24-h mass. First void concentration correlated with 24-h mass. The 24-h mass RPCs were 167.0, 116.8, and 108.1 mg for 1-, 2-, and 3-wk average measurements. First void concentration RPCs were 90.6, 76.6, and 72.8 mg L¹. Skylab astronauts 24-h mass increased by 88.9 76.0, 123.5 58.3, 142.2 56.5, and 159.9 83.4 mg after 1, 2, 3, and 4 wk in flight.DISCUSSION: Averaging multiple Uca measurements reduced variability effectively and allowed increases likely to be seen in space to be detected. Consecutive Uca measurements could be tracked over time in space to assess the effectiveness of the countermeasure program. First void concentration could potentially be used rather than 24-h collections.Ren J, Stankovic AS, Knaus DA, Phillips SD, Kynor DB, Buckey JC. Urinary calcium for tracking bone loss and kidney stone risk in space. Aerosp Med Hum Perform. 2020; 91(9):689696.

PURPOSE: The objective was to quantify the venous redistribution during a 4-d dry immersion (DI) and evaluate the effect of thigh cuffs.METHODS: The study included nine control (Co) and nine subjects wearing thigh cuffs during the daytime (CU). Ultrasound measures were performed Pre-DI, on day 4 AM (D4 AM) and D4 PM: left ventricle stroke volume and ejection fraction (SV, EF), jugular vein volume (JVvol), portal vein diameter (PV), and middle cerebral vein velocity (MCVv). An additional measure of JVvol was performed on Day 1 after 2 h in DI.RESULTS: After 2 h in DI, JVvol increased significantly from Pre in both groups, but increased more in the Co compared to the CU subjects (Co: 0.27 0.15 cm³ to 0.94 0.22 cm³; CU: 0.32 0.13 cm³ to 0.64 0.32 cm³). At D4 AM, SV and EF decreased from Pre (SV: 111 23 cm³ to 93 24 cm³; EF: 0.66 0.07 to 0.62 0.07). JVvol was slightly increased (Co: 0.47 0.22 cm³ CU: 0.35 014 cm³). MCVv and PV remained unchanged from Pre-DI. No difference was found between the two groups for any of the parameters measured. From D4 AM to PM, no significant change was observed for any parameter.CONCLUSION: The results confirm that DI induces, during the first 2-3 h, a significant cephalic fluid shift as observed in spaceflight. During this early phase, the thigh cuffs reduced the amplitude of the fluid shift toward the head, but after 4 d in DI there was only a slight memory (residual) effect of DI on the jugular volume and no residual effect of the thigh cuffs.Arbeille P, Greaves D, Guillon L, Besnard S. Thigh cuff effects on venous flow redistribution during 4 days in dry immersion. Aerosp Med Hum Perform. 2020; 91(9):697702.

BACKGROUND: Motion sickness is a problem for many; however, it is especially pressing for military personnel who need to operate in life and death environments. The current study investigated the underlying cause of motion sickness by testing postural instability theory.METHODS: Subjects experienced realistic motion profiles while performing a virtual reality shooting task and reporting any motion sickness symptoms. Postural instability was manipulated within 20 subjects across 2 conditions. In one condition, subjects could readily adapt their posture to the motion profile by adjusting their feet on the platform (Free), and in the other condition, their feet were fixed in place on the moving platform (Fixed). This Free condition decreased postural instability by allowing adjustment, while the Fixed condition increased postural instability by restricting adjustment. The same subjects completed both conditions to control for individual differences in motion sickness susceptibility.RESULTS: Overall, motion sickness was mild as measured by SSQ (M 14.41, Free; M 18.89, Fixed), and no statistically significant differences were observed between the conditions. Performance on the shooting task was reduced in accuracy by approximately 40%, although this result did not differ between conditions.DISCUSSION: The results do not support postural instability as a contributing factor in motion sickness symptomology. They also demonstrate the importance of accounting for motion when conducting training.Pettijohn KA, Pistone DV, Warner AL, Roush GJ, Biggs AT. Postural instability and seasickness in a motion-based shooting simulation. Aerosp Med Hum Perform. 2020; 91(9):703709.

INTRODUCTION: Aircraft maintenance workers may be exposed to organophosphates in hydraulic fluid and engine oil. Previous research has indicated that inhalation may not be the primary exposure route. This study sought to measure dermal contact and inhalation in conjunction with cholinesterase inhibition and determine if Air Force Specialty Code serves as an exposure predictor.METHODS: Aircraft maintenance workers were sampled for changes in acetylcholinesterase and butyrylcholinesterase. Dermal contact was measured using wrist-worn silicone passive dosimeters and inhalation exposure was measured using thermal desorption tube air sampling.RESULTS: Overall prevalence of any cholinesterase inhibition in the study population was 25.33%. Prevalence of inhibition of acetylcholinesterase and butyrylcholinesterase was 18.67% and 6.67%, respectively. The mean tributyl phosphate result was 1.71 ng of tributyl phosphate per gram of wristband (ng g¹) [95% confidence interval (CI): 5.63, 9.05]. Triphenyl phosphate was more prevalent, with only one sample below the limit of detection (mean 1386.26 ng g¹; 95% CI: 7297.78, 10,070.31), and tricresyl phosphate was found in every sample (mean 4311.65 ng g¹; 95% CI: 8890.24, 17,512.31). No organophosphates were detected via air sampling.DISCUSSION: Workers experienced organophosphate exposure and cholinesterase inhibition, but the study was not large enough to establish a statistically significant association between exposure and disease. Exposure to organophosphate esters is more likely to occur through contact and absorption of chemicals through the skin than through inhalation of oil mists. Air Force Specialty Code does not appear to be a good predictor of exposure to organophosphates. Future studies should consider using a larger sample size.Hardos JE, Rubenstein M, Pfahler S, Sleight T. Cholinesterase inhibition and exposure to organophosphate esters in aircraft maintenance workers. Aerosp Med Hum Perform. 2020; 91(9):710714.

BACKGROUND: Cabin pressurization is the process by which aircraft maintain a comfortable and safe environment for passengers flying at high altitudes. At high altitudes, most patients can tolerate changes in pressurization; however, passengers at high risk of hypoxia may experience ischemic events. The purpose of this study was to evaluate variations in pressurization of commercial aircraft at cruising altitude and describe its relevance in relation to patients with non-arteritic anterior ischemic optic neuropathy (NAION).METHODS: Altimeters were used to measure altitude and cabin altitude at cruising altitude aboard 113 commercial flights, including 53 narrow-body and 60 wide-body aircraft.RESULTS: Cabin altitude ranged from 4232 ft to 7956 ft at cruising altitudes ranging from 30,000 ft to 41,000 ft. The mean cabin altitude for all flights was 6309 876 ft. Narrow-body aircraft had a significantly higher mean cabin altitude (6739 829 ft) compared to wide-body aircraft (5929 733 ft). For all flights, the mean cruising altitude was 35,369 2881 ft with narrow-body aircraft cruising at a lower altitude of 34,238 2389 ft compared to wide-body aircraft at 36,369 2925 ft. Newer generation aircraft had a mean cabin altitude of 6066 837 ft, which was lower than the mean cabin altitude of older aircraft (6616 835 ft).DISCUSSION: Innovation in flight design has offered the ability for aircraft to fly at greater altitudes while maintaining lower cabin altitude. Those at high risk of hypoxia-induced complications may consider aircraft type when air travel is required.Nazarali S, Liu H, Syed M, Wood T, Asanad S, Sadun AA, Karanjia R. Aircraft cabin pressurization and concern for non-arteritic anterior ischemic optic neuropathy. Aerosp Med Hum Perform. 2020; 91(9):715719.

INTRODUCTION: It is important for military commanders to know the extent of fatigue experienced by soldiers undergoing a long-term military training. This knowledge can enable them to determine the level of physical capabilities of soldiers. The present study aimed to evaluate changes in the level of chosen biochemical parameters in blood during the survival training of Polish Naval Academy cadets. METHODS: Participating voluntarily in the research study were 14 cadets. All subjects were men, ages 23.1 2.0 yr. During the 36-h survival training, the subjects were deprived of sleep. The following biochemical parameters were assessed in venous blood collected from the cadets: creatine kinase (CK) activity, concentration of lipid hydroperoxides (LOOHs), superoxide dismutase activity (SOD), and glutathione peroxidase activity (GPx). RESULTS: After 36 h of training a significant increase was observed in CK (from 183.1 up to 530.2 U L¹), LOOHs (from 1.72 up to 3.74 mol L¹), and GPx (from 27.4 up to 36.4 U gHb¹). After 12 h of rest, the level of LOOHs returned to the initial level, GPx activity did not change significantly, and CK activity was significantly higher than those at baseline (422.3 U L¹). DISCUSSION: The 36-h survival training increased oxidative stress, which contributed to the damage to muscle cells in the group of cadets of the Polish Naval Academy. The intensity of postexercise changes in the level of oxidative damage indicators is dependent on the initial level of enzymatic antioxidant defense. The 12-h recovery proved to be too short to regenerate the damaged muscle tissue. Tomczak A, Jówko E, Różański P. Survival training effects on oxidative stress and muscle damage biomarkers of naval cadets. Aerosp Med Hum Perform. 2020; 91(9):720724.

INTRODUCTION: The current U.S. Army aviator anthropometric screening process for rotary-wing cockpit compatibility was codified over 30 yr ago. Critical to the process are the anthropometric standards that define what is acceptable for U.S. Army flight school applicants. The purpose of this study was to assess and optimize the efficiency of the standards in screening for anthropometric cockpit compatibility while maintaining safety.METHODS: A retrospective analysis was performed. Anthropometry and disposition data of flight school applicants from 2005 to 2014 were taken from the Aeromedical Electronic Resource Office database to determine efficiency of the process. Data on mishaps from 1972 to 2017 were retrieved from the Risk Management Information System database to determine the safety benchmark of the existing process, to which adjusted standards would be held. Adjustments to standards were modeled that would more efficiently pass applicants over the period studied without exceeding the established acceptable safety level.RESULTS: There were 40,136 (98.28%) applicants who passed the standards, while 702 (1.72%) failed. Most (98.52%) applicants who failed the standards and applied for an anthropometry exception to policy (ETP) received one. The models would pass up to 396 (99.25%) applicants who received ETPs without exceeding the established number of mishaps attributable to the anthropometry standards, which was found to be zero.DISCUSSION: The screening process is efficient and effective, but could be improved. Adjusting the standards could increase process efficiency by passing more applicants during their flight physical and widening the applicant pool, while maintaining the current level of safety.Moczynski AN, Weisenbach CA, McGhee JS. Retrospective assessment of U.S. Army aviator anthropometric screening process. Aerosp Med Hum Perform. 2020; 91(9):725731.

BACKGROUND: From 2007, the Federal Aviation Administration (FAA) permitted pilots who have had a heart transplant to be considered for recertification under special issuance at the third-class level. The objective of this study was to evaluate certification safety and determine if any adverse outcome occurred in this airman group as a consequence of this policy.METHODS: Methods involved collecting data from the FAA Document Imaging Workflow System to identify airmen undergoing cardiac transplantation since 2007, and examining medical and safety-related outcomes through the National Transportation Safety Board-related accident database and the Centers for Disease Control and Prevention National Death Index.RESULTS: Included in the study were 36 airmen, with 16 recertified at the class 3 level and 20 denied certification. No aviation accidents or recorded deaths occurred in the group of 16 airmen undergoing recertification. Of these airmen, 13 underwent a second successful recertification and 6 underwent a third attempt, with 5 being successful. Two airmen have declared their intention to fly under BasicMed. Of the 20 airmen denied recertification, 16 were denied for failure to provide information. There were three deaths in this denied group.DISCUSSION: The policy allowing third-class heart transplant recipient recertification appears to be safe. Aviation safety is not being compromised by allowing these airmen to resume flying, with the exception that recertification should continue under the special issuance system and not through BasicMed.Norris A, Skaggs V, Kaye D, De Voll J, McGiffin D. Selective recertification of pilots who have undergone a cardiac transplant. Aerosp Med Hum Perform. 2020; 91(9):732736.

INTRODUCTION: Numerous issues in mental health benefit from technological innovation. An example involves the mental health challenges of long-duration spaceflight (such as a Mars mission), including prolonged confinement, microgravity, and different sunlight exposure lengths. Persisting on Earth are global mental health challenges stemming from disease burdens, limited interview-based diagnostic systems, trial-and-error treatment approaches, and suboptimal access. There is potential for cross-pollinating solutions between these seemingly disparate challenges using a range of emerging technologies such as sensors, omics, and big data. In this review, we highlight the bidirectional value of mental health technology transfer aimed to address issues both on Earth and in space.METHODS: We prepared a systematic review of studies pertaining to mental health technological innovation and space medicine.RESULTS: For Earth mental health technologies translatable to long-duration space missions, we cite several example technologies, including device-based psychotherapy and social support, conversational agents aka chatbots, and nutritional and physical activity focused mental health. Space technologies translatable to Earth mental health include remote sensing devices, global navigation satellite systems, satellite communications, chronotherapies, and nutritional advances.DISCUSSION: There is a rich history of space technologies informing Earth technological trends, including general health care on Earth, and vice versa. To avoid the traditional happenstance approach that results in delays, missed opportunities, and increased cost, and to improve outcomes for both Earth and space utilization of these technologies, we propose increased dialogue and training opportunities to enhance innovation and outcomes.Chang DD, Storch EA, Black L, Berk M, Pellis N, Lavretsky H, Sutton J, Ternes K, Shepanek M, Smith E, Abbott R, Eyre HA. Promoting tech transfer between space and global mental health. Aerosp Med Hum Perform. 2020; 91(9):737745.

BACKGROUND: Syncope and near-syncope are commonly encountered symptoms. Many cases are situationally specific or otherwise benign, with no adverse aeromedical implications. Autonomic dysfunction can produce orthostatic intolerance with resultant symptoms and is aeromedically concerning for potential occurrence in flight. Vitamin B12 deficiency is an insidious condition with protean manifestations, which can present with autonomic dysfunction. Neurological abnormalities are often reversible following adequate replacement.CASE REPORT: We describe a case of vitamin B12 deficiency in a pilot with atypical syncope and abnormal tilt-table testing who had progressively abnormal hematologic findings on review. He was also discovered to have intrinsic factor antibodies. After B12 replacement, he had normal cardiovascular response to exercise stress testing and an unremarkable centrifuge assessment.DISCUSSION: This case highlights the importance of recognizing subtle laboratory findings and serial laboratory data review in cases of atypical syncope to identify potential reversible etiologies.Hesselbrock RR, Palileo EV, Davenport ED. Vitamin B12 deficiency related syncope in a young military pilot. Aerosp Med Hum Perform. 2020; 91(9):746748.