INTRODUCTION: A flight trial was conducted to determine whether breathing 60% oxygen during high performance flight maneuvers using contemporary pilot flight equipment induces atelectasis and to explore whether cabin altitude had any influence on the extent of atelectasis identified.METHODS: On 2 separate days, 14 male aircrew flew as passengers at High [14,500–18,000 ft (4420–5486 m)] and Low [4000–6000 ft (1219–1829 m)] cabin pressure altitude in a Hawk T Mk1 aircraft breathing 60% oxygen. Sorties comprised 16 maneuvers at +5 G_z, each sustained for 30 s. Lung volumes (spirometry), basal lung volume (electrical impedance tomography, EIT), and peripheral oxygen saturation during transition from hyperoxia to hypoxia (pulmonary shunt fraction) were measured in the cockpit immediately before (Pre) and after (Post) flight.RESULTS: Forced inspiratory vital capacity (FIVC) was significantly lower Postflight after High (−0.24 L) and Low (−0.38 L) sorties, but recovered to Preflight values by the fourth repeat (FIVC4). EIT-derived measures of FIVC decreased after High (−3.3%) and Low (−4.4%) sorties but did not recover to baseline by FIVC4. FIVC reductions were attributable to decreased inspiratory capacity. S_po₂ was lower Postflight than Preflight in High and Low sorties.DISCUSSION: Breathing 60% oxygen during flight results in a 3.8–4.9% reduction in lung volume associated with a small decrease in blood oxygenation and an estimated pulmonary shunt of up to 5.7%. EIT measures suggest persisting airway closure despite repeated FIVC maneuvers. There was no meaningful influence of cabin pressure altitude. The operational consequence of the observed changes is likely to be small.Tank H, Kennedy G, Pollock R, Hodkinson P, Sheppard-Hickey R-A, Woolford J, Green NDC, Stevenson A. Cabin pressure altitude effect on acceleration atelectasis after agile flight breathing 60% oxygen. Aerosp Med Hum Perform. 2023; 94(1):3–10.

INTRODUCTION: The U.S. Navy experienced a series of physiological events in aircrew involving primarily the F/A-18 airframe related to rapid decompression of cabin pressures, of which aviation decompression sickness (DCS) was felt to contribute. The underlying pathophysiology of aviation DCS is the same as that of diving-related. However, based on the innate multifactorial circumstances surrounding hypobaric DCS, in clinical practice it continues to be unpredictable and less familiar as it falls at the intersect of aerospace and hyperbaric medicine. This retrospective study aimed to review the case series diagnosed as aviation DCS in a collaborative effort between aerospace specialists and hyperbaricists to increase appropriate identification and treatment of hypobaric DCS.METHODS: We identified 18 cases involving high-performance aircraft emergently treated as aviation DCS at a civilian hyperbaric chamber. Four reviewers with dual training in aviation and hyperbaric medicine retrospectively reviewed cases and categorized presentations as “DCS” or “Alternative Diagnosis”.RESULTS: Reviewers identified over half of presenting cases could be attributed to an alternative diagnosis. In events that occurred at flight altitudes below 17,000 ft (5182 m) or with rapid decompression pressure changes under 0.3 atm, DCS was less likely to be the etiology of the presenting symptoms.CONCLUSIONS: Aviation physiological events continue to be difficult to diagnose. This study aimed to better understand this phenomenon and provide additional insight and key characteristics for both flight physicians and hyperbaric physicians. As human exploration continues to challenge the limits of sustainable physiology, the incidence of aerospace DCS may increase and underscores our need to recognize and appropriately treat it.Kutz CJ, Kirby IJ, Grover IR, Tanaka HL. Aviation decompression sickness in aerospace and hyperbaric medicine. Aerosp Med Hum Perform. 2023; 94(1):11–17.

BACKGROUND: Unexpected events in flight might decrease the transparency of the flying process and weaken the pilot’s perception of the current state, or even erode manipulating skills. However, during the flight test of a new or modified aircraft, to verify the boundaries of aircraft aerodynamic performance and handling stability, unexpected events may be encountered that need to be handled by the test pilot. Therefore, studying the differences between test pilots and airline pilots could help improve flight safety.METHODS: Two kinds of physiological parameters, eye blink rate and average fixation duration and task-related performance of test pilots and airline pilots, were analyzed in three abnormal scenarios. A total of 16 pilots participated. The study was carried out in an A320 flight simulator.RESULTS: The differences were significant for both test pilots and airline pilots in eye blink rate and average fixation duration. Furthermore, the reaction time of test pilots (Mean = 23.38 s) was significantly shorter than airline pilots (Mean = 42.63 s) in Unreliable Airspeed condition, and the pitch angle deviations between them were significant in both Wind Shear and Unreliable Airspeed condition.DISCUSSION: The uncertainty of environmental change could create more severe pressure and mental workload influence than actual system failure. For airline pilots, compared with test pilots, the importance of practicing manual flight should still be emphasized. Improving reactions to unexpected ambient conditions and unannounced fault status could also contribute to flight safety.Zheng Y, Lu Y, Jie Y, Zhao Z, Fu S. Test pilot and airline pilot differences in facing unexpected events. Aerosp Med Hum Perform. 2023; 94(1):18–24.

INTRODUCTION: Ethyl acetate is a simple organic compound that occurs naturally and is used industrially as a solvent. It has been detected in the ISS atmosphere and is known to off-gas from building materials. As NASA astronauts have been and will be exposed to ethyl acetate during space missions, Spaceflight Maximum Allowable Concentrations (SMACs) were developed following an extensive review of the available literature.METHODS: Toxicological data relevant to SMAC development was collected from electronic databases using principles of systematic review, and from previous assessments and reviews of ethyl acetate.RESULTS: From an initial pool of over 35,000 studies, 10 were identified as studies appropriate to support SMAC development. The toxicological properties of ethyl acetate are relatively straightforward. Ethyl acetate is rapidly absorbed and converted by carboxyesterases to ethanol. At concentrations on the order of 400 ppm for 4–8 h, most volunteers experienced mild irritation but no lasting effects. In subchronic animal studies, mild sedative effects and changes in body weight and weight gain were observed at 750 ppm and above.DISCUSSION: Numerous studies were identified to support the development of both short- and long-duration SMACs. No chronic studies were available, but the high quality of the subchronic studies and the short half-life of ethyl acetate support extrapolation to longer durations.Williams ES, Ryder VE. Spaceflight maximum allowable concentrations for ethyl acetate. Aerosp Med Hum Perform. 2023; 94(1):25–33.

BACKGROUND: Surface extravehicular activity (sEVA) will be a critical component of future human missions to the Moon. sEVA presents novel risks to astronaut crews not associated with microgravity operations due to fundamental differences in task demands, physiology, environment, and operations of working on the lunar surface. Multimodal spacesuit informatics displays have been proposed as a method of mitigating sEVA risk by increasing operator autonomy.METHODS: A formalized literature review was conducted. In total, 95 journal articles, conference papers, and technical reports were included. Characteristics of U.S. spacesuits were reviewed, ranging from the Apollo A7L to the xEMU Z-2.5. Multimodal display applications were then reviewed and assessed for their potential in aiding sEVA operations.RESULTS: Through literature review 25 performance impairments were identified. Performance impairments caused by the spacesuit represented the greatest number of sEVA challenges. Multimodal displays were mapped to impairments and approximately 36% of performance impairments could be aided by using display interfaces.DISCUSSION: Multimodal displays may provide additional benefits for alleviating performance impairments during sEVA. Utility of multimodal displays may be greater in certain performance impairment domains, such as spacesuit-related impairments.Zhang JY, Anderson AP. Performance risks during surface extravehicular activity and potential mitigation using multimodal displays. Aerosp Med Hum Perform. 2023; 94(1):34–41.

INTRODUCTION: Recently developed wearable monitoring devices can provide arterial oxygen saturation (S_po₂) measurements, offering potential for use in aerospace operations. Pilots and passengers are already using these technologies, but their performance has not yet been established under conditions experienced in the flight environment such as environmental hypoxia and concurrent body motion.METHODS: An initial evaluation was conducted in 10 healthy subjects who were studied in a normobaric chamber during normoxia and at a simulated altitude of 15,000 ft (4572 m; 11.8% oxygen). S_po₂ was measured simultaneously using a standard pulse oximeter and four wearable devices: Apple Watch Series 6; Garmin Fēnix 6 watch; Cosinuss^o Two in-ear sensor; and Oxitone 1000M wrist-worn pulse oximeter. Measurements were made while stationary at rest, during very slight body motion (induced by very low intensity cycling at 30 W on an ergometer), and during moderate body motion (induced by moderate intensity cycling at 150 W).RESULTS: Missed readings, defined as failure to record an S_po₂ value within 1 min, occurred commonly with all wearables. Even with only very slight body motion, most devices missed most readings (range of 12–82% missed readings) and the rate was higher with greater body motion (range 18–92%). One device tended to under-report S_po₂, while the other devices tended to over-report S_po₂. Performance decreased across the devices when oxygenation was reduced.DISCUSSION: In this preliminary evaluation, the wearable devices studied did not perform to the same standard as a traditional pulse oximeter. These limitations may restrict their utility in flight and require further investigation.Hearn EL, Byford J, Wolfe C, Agyei C, Hodkinson PD, Pollock RD, Smith TG. Measuring arterial oxygen saturation using wearable devices under varying conditions. Aerosp Med Hum Perform. 2023; 94(1):42–47.

BACKGROUND: The purpose of this report is to document the first use of a single piece, posterior chamber phakic implantable collamer lens (ICL) with a central port in the right eye (OD) of a spaceflight participant (SFP) during a 12-d Soyuz mission to the International Space Station (ISS). We also briefly document the stability of a pre-existing pachychoroid pigment epitheliopathy (PPE) in the macula of his left eye (OS) during this mission.CASE REPORT: Ocular examination, including refraction, slit lamp examination, macular examination by optical coherence tomography (OCT), and tonometry were performed before and after his mission and he was questioned regarding visual changes during each portion of his flight.DISCUSSION: We documented no change in ICL position during his spaceflight. He reported stable vision during liftoff, entry into microgravity, 12 d on the ISS, descent, and landing. Our results suggest that the modern ICL with a central port is stable, effective, and well tolerated during short duration spaceflight. His PPE also remained stable during this mission as documented by OCT.Gibson CR, Mader TH, Lipsky W, Brown DM, Jennings R, Law J, Sargsyan A, Brunstetter T, Danilichev SN, Maezawa Y. Implantable collamer lens use in a spaceflight participant during short duration spaceflight. Aerosp Med Hum Perform. 2023; 94(1):48–50.