INTRODUCTION: With the increasing use of aeromedical transport for critically ill patients, it is essential to understand the impact of pressure changes on drug infusion delivery systems. As airplanes ascend and descend, gases/bubbles are released from solutions when ambient pressure decreases and dissolves when pressure increases. This may affect mechanical fluid delivery systems and cause clinically significant changes, especially within a critical care setting. We aimed to evaluate the impact of pressure changes on volumetric pumps and syringe drivers.

METHODS: An in vitro study of six volumetric pumps and eight syringe drivers was conducted in a hypobaric chamber to mimic pressure changes during flights. Infusion devices were set to deliver water at 0.2 ml ⋅ h⁻¹ and infused volumes were measured. There were 15 open-ended syringes also studied.

RESULTS: During ascent, syringe drivers and volumetric pumps over-delivered 173 µL and 38 µL of fluid. During descent, syringe drivers under-delivered by 166 µL, whereas volumetric pumps under-delivered by 9 µL. Syringe drivers experienced statistically significant changes in fluid delivery during both ascent and descent. In volumetric pumps, only the descent phase infusion differed significantly from other phases. The volume of fluid expansion is dependent on volume and the mechanical properties of the fluid.

DISCUSSION: Decreasing ambient pressure causes bubble formation, which displaces fluid, and increasing ambient pressure causes bubble reabsorption in mechanical infusion devices. Hence, atmospheric pressure changes during air travel may alter fluid delivery from medical fluid delivery systems and affect critically ill patients who require both aeromedical evacuation and accurate infusion of drugs.

Fan KS, Paterson M, Shojaee-Moradie F, Manoli A, Edwards V, Lee V, Hutchison E, Gifford RM, Parsons IT, Koehler G, Mathieu C, Mader JK, King BR, Russell-Jones D; EASA Consortium. Performance of fluid infusion systems in the changing atmospheric pressures encountered in aviation. Aerosp Med Hum Perform. 2025; 96(1):4–11.

INTRODUCTION: Many questions are still being asked about the actual health effects of exposure to a fume event for airline crewmembers. To shed new light on this controversy about so-called aerotoxic syndrome, we undertook a large-scale epidemiological study.

METHODS: We present a retrospective cohort study involving 14,953 crewmembers, including 2577 exposed to a fume event and 12,376 matched controls to estimate the hazard ratio of a subsequent sickness.

RESULTS: Prevalence of diseases that could be related to the fume event based on “possible” or “probable” level and date of occurrence after the fume event was for exposed (controls): neurological 2.9% (2.9%), psychiatric 2.5% (2.4%), vegetative 1.8% (1.5%), irritative 5.1% (4.5%), and functional 2.8% (3.2%). Differences were not significant. Incidences of having any related disease are estimated at 1552 per 100,000 person-years for exposed and 1497 per 100,000 person-years for controls, with a nonsignificant hazard ratio of 1.04 (0.86–1.25) in the Cox model. A subset of 2577 matched pairs exposed/control allowing specific statistical tests for paired data confirmed the lack of difference between exposed and controls: matched-pair risk ratio for any fume event related disease was 1.07 (0.85–1.34).

DISCUSSION: Our results clearly show that fume events are not associated with significant clinical consequences for cabin and cockpit crew. This work does not support the proposal of an “aerotoxic syndrome” in association with exposure to fume events.

Klerlein M, Dubiez L. Medical consequences after a fume event in commercial airline crews. Aerosp Med Hum Perform. 2025; 96(1):12–17.

INTRODUCTION: Metaphoric signs, which refer to a resemblance to something absent, are, like pareidolia, strong cognitive tools that help us understand abstract concepts by relating them to concrete, sensory experiences, and these have not been studied in student pilots. Evaluating the characteristics of students in aviation, including sensory experiences such as stress, decision-making, and pattern recognition, is important for safe flight. This study aims to investigate the cognitive and emotional impacts of face pareidolia among pilot students by using the digital Pareidolia Test (PT).

METHODS: Subjects were 86 students from the Professional Pilot B.Sc. Program. PT includes 10 face and 10 pareidolia images. The number of European Aviation Safety Agency flight and simulator training hours, stress levels, and perceiving emotion in the pareidolia and face images were assessed using a self-report questionnaire. Descriptive statistics were used to test normality, and the Chi-squared test was used to analyze differences.

RESULTS: Results indicated significant differences in perceiving emotion in facial images based on stress levels from flight training from faculty courses (N = 42/86, 49.9%), and perceiving faces in pareidolia images related to flight simulator training hours. Perceiving emotions in pareidolia images varied significantly based on the number of European Aviation Safety Agency tests, but perceiving faces on pareidolia images did not show significant differences.

DISCUSSION: We claim that incorporating pareidolia in aviation training enhances pilots’ pattern recognition abilities, facilitating more accurate decision-making. The research recommends using the new digital PT in professions that require attention, such as pilots, to evaluate these parameters.

Akdeniz G, Yilmaz HE, Geza H. Cognitive and emotional impacts of face pareidolia application among pilot students. Aerosp Med Hum Perform. 2025; 96(1):18–22.

INTRODUCTION: Insomnia and sleep apnea (SA) can have adverse effects on operating aircraft. This study examined trends in insomnia and SA incidence rates in U.S. military aviators from 2006–2022 and examined associated demographic and operational factors.

METHODS: Data on incidence cases of outpatient insomnia and SA, aviator demographics, and operational factors were obtained from the Defense Medical Epidemiological Database, a comprehensive online archive of military medical data. Insomnia and SA cases were identified using specific International Classification of Diseases codes.

RESULTS: For the entire military aviator population (N = 331,992 ± 1649, mean ± SD) overall rates of insomnia and SA were 10.2 and 24.9 cases/1000 person-years, respectively. Compared to the entire U.S. military nonaviator population, aviators had lower incidence of insomnia, but higher incidence of SA. Insomnia rates among aviators increased up to 2015 and declined afterwards, while SA rate generally rose over the period. Insomnia and SA rates among aviators increased with age, were higher among those of black and other nonwhite races, were highest among Army personnel (compared to other services) and were highest among helicopter pilots (compared to fixed-wing aircraft pilots). Insomnia rates were similar among male and female aviators, but SA rates were higher among men.

DISCUSSION: These data indicate that insomnia and SA are prevalent within the military aviation population; however, the incidence of insomnia appears to have fallen as the tempo of military operations has decreased while the incidence of SA continues on an upward trajectory, possibly associated with the growing problem of obesity.

Caldwell JA, Knapik JJ. Trends and factors associated with insomnia and sleep apnea in U.S. military aviators, 2006–2022. Aerosp Med Hum Perform. 2025; 96(1):23–30.

INTRODUCTION: In-flight medical incapacitation jeopardizes flight safety. To reduce such breakdown episodes, airlines have implemented a sick leave system. This study aimed to examine the association of total flight hours and health status with sick leave use among civilian pilots in South Korea and to identify the demand for a health promotion program.

METHODS: For data collection, an online survey was conducted between August–November 2018, involving pilots of nine civil airlines in South Korea. A total of 456 pilots responded, of which data from 6 were excluded due to missing items; 450 pilots were included in the final analysis. The SPSS WIN 26.0 software was used for analysis, and a logistic regression analysis was performed.

RESULTS: The factors influencing sick leave were 7.39 times higher in the case of 1000–4999 h of total flight time than in the case of less than 1000 h, and 2.19 times higher for those with pre-existing conditions than for those without.

DISCUSSION: Future research is needed to focus on the relationship between sick leave use and chronic diseases and between sick leave use and health-promoting behaviors among pilots. In addition, health promotion programs may be more effective if they are tailored to the job characteristics of pilots. Furthermore, counseling and education programs regarding the numerous harms of high-risk drinking must be strengthened. This may include emphasizing the negative effects of drinking on flight safety and personal health.

Han B-S, Choi E-H, Kim M-S. Association of total flight hours and health conditions with sick leave use among civilian pilots. Aerosp Med Hum Perform. 2025; 96(1):31–38.

INTRODUCTION: Fighter pilots are a population particularly vulnerable to developing mental fatigue, which puts the safety of military operations at risk. Although there is no gold standard tool for its assessment, Yoshitake’s Feeling of Fatigue Scale (FFS) appears promising for application to fighter pilots as it has already been validated for Brazilian commercial airline pilots. The objective of this study was to evaluate the psychometric properties of the FFS in Brazilian fighter pilots.

METHODS: This was a cross-sectional study, carried out between March–August 2023, with 58 fighter pilots operating F-5M and JAS 39E aircraft. A sociodemographic questionnaire, the FFS, and the Samn-Perelli Scale were applied in two moments with a maximum interval of 7 d between them. The reliability/reproducibility and agreement of the instrument were evaluated using Cronbach’s α, Cohen’s κ test (for categorical variables), and the intraclass correlation coefficient for numerical variables in the test-retest. Criterion validation was carried out using the Samn-Perelli Scale. Data were also analyzed using Statistical Package for Social Sciences statistical software, version 25.0.

RESULTS: The instrument presents good reliability, being suitable for evaluating the domains of drowsiness [a = 0.840, F = 6.241, confidence interval (CI): 0.576–0.827], concentration (a = 0.907, F = 10.739, CI: 0.726–0.894) and physical discomfort (a = 0.747, F = 3.948, CI: 0.385–0.730). The criterion validity analysis showed that the FFS is valid and accurate for assessing mental fatigue in Brazilian fighter pilots.

DISCUSSION: The psychometric properties of the FFS are suitable for assessing mental fatigue in this population.

Milioli Ferreira D, Morisco de Sá P, Bittencourt Ferreira D. The Feeling of Fatigue Scale for Brazilian fighter pilots. Aerosp Med Hum Perform. 2025; 96(1):39–44.

INTRODUCTION: In space, under weightlessness conditions, human brain activity is changed due to the shifting of body fluid and blood toward the cephalic region. This shifting leads to changes in cerebral hemodynamics and, consequently, neurophysiological function, which impacts mental functions like cognition and decision-making capabilities of space travelers. The present study reports the effect of acute exposure to simulated microgravity on cognitive functions and event-related potentials.

METHODS: There were 18 healthy human subjects who participated in a 1-h 6° head-down tilt (HDT) bed rest to simulate physiological conditions during microgravity. Subjects were instructed to perform event-related potential tasks and cognitive tasks with a simulator sickness questionnaire to evaluate their performance, attention, and alertness during weightlessness, at baseline, after microgravity exposure, and after a recovery of 30 min.

RESULTS: A significant change was found in the latency of P300 as compared to the baseline. The amplitude of the P300 wave was changed during HDT. The mean reaction time of contingent negative variation increased significantly as compared to the baseline. A significant increase in choice reaction time was observed during HDT vs. baseline. The values recovered partially after 30 min of exposure.

DISCUSSION: It was concluded that simulated microgravity impacts mental functions as evidenced by alterations in choice reaction time and event-related potential latencies and reaction time. The study has applied value for understanding neurophysiological responses and optimization of cognitive performance in space conditions.

Sharma M, Gaur S, Pawar H, Yadav N, Thondala B, Kumar S, Kishore K, Ray K, Panjwani U. Neurophysiological and cognitive changes induced by the acute head-down tilt. Aerosp Med Hum Perform. 2025; 96(1):45–52.

INTRODUCTION: Space agencies will embark on manned journeys to Mars on smaller vehicles than those used previously. In-flight exercise on those flights must abate the adverse effects microgravity (μG) has on humans. Due to space constraints on these vehicles, a single exercise device must address multiple fitness needs. Exercise and μG individually cause body heat accrual. During in-flight exercise they conspire to exacerbate heat gain. Given the duration of Mars missions and volume of exercise they entail, excess heat accrual must be addressed.

METHODS: This review presents data on μG, thermoregulation, and exercise. Since their relationships are impacted by other variables, energy balance, body water, and cerebral and vascular physiology are discussed. Data are integrated to acknowledge the challenges long-term missions, and the in-flight exercise that accompanies them, impose on thermoregulation. Strategies to limit heat accrual are discussed.

RESULTS: Current in-flight exercise and hardware will not address heat accrual mitigation or operational performance needs for Mars missions.

DISCUSSION: This review suggests for future missions, crewmembers: 1) consume beverages with high sodium contents; 2) employ palm cooling for conductive heat transfer; and 3) perform plyometric exercise on gravity-independent hardware. Research should continue to evaluate these treatments to abate heat gain in μG.

Maguire K, Wydotis M, Bollinger L, Caruso J. Abating heat accrual during exercise in microgravity and implications for future long-term missions. Aerosp Med Hum Perform. 2025; 96(1):53–61.

INTRODUCTION: The introduction of fifth-generation fighter aircraft has raised concerns regarding the impact of high gravitational forces on lung function. This study aimed to investigate the acute effects of controlled +G_z exposure, up to +9 G_z, on lung function in military pilots using impulse oscillometry (IOS).

METHODS: These studies, conducted in Canada and the Netherlands, involved military pilots undergoing high G centrifuge training. IOS measurements were obtained using the Tremoflo^TM IOS device, which assesses lung function during normal tidal breathing without forced maneuvers. Included in the study were 30 military pilots of the Royal Canadian Air Force (RCAF) and 28 military pilots trained by the Royal Netherlands Air Force (RNLAF). Both performed baseline IOS measurements, with postexposure measurements obtained within 10 min in RCAF pilots and within 2 min by the RNLAF.

RESULTS: Both the RCAF and RNLAF studies showed significant increases in compliance (median = −1.605 and −2.085) and decreases in resistance (median = −0.611 and −0.230). Small airway resistance reduction was significant only in the RNLAF study (median = 0.176), indicating a greater effect at higher G_z levels.

DISCUSSION: The combined data showed no evidence that repeated exposure to high +G_z in combination with an anti-G suit and performance of the anti-G straining maneuver has acute negative effects on lung function. In fact, there was evidence of improvement in small airway function, perhaps as a result of the respiratory strain component of the anti-G straining maneuver, which increases intrathoracic pressure, possibly stretching the small airways, decreasing resistance, and increasing reactance.

Cornelissen SJWM, Frijters E, Gray G. Lung function changes with acute +G_z exposure as assessed by impulse oscillometry. Aerosp Med Hum Perform. 2025; 96(1):62–66.

BACKGROUND: Mission Controllers (MCs) are the main point of contact for space crews and are vital for successful human spaceflight. On a mission to Mars, there will be as long as 22-min one-way communication delays between the ground and the crew, causing major changes to current communication infrastructures.

METHODS: This exploratory study assessed the impact of a 20-min one-way communication delay on MCs’ task performance, workload, and stress levels under nominal and off-nominal conditions, conducted during a 21-d analog mission.

RESULTS: Decrements in performance were noted on both nominal and off-nominal task completion in time-delay conditions [100% of real-time (rt) tasks complete, 16.7% of time-delay (td) tasks incomplete; 12.50% of nominal tasks and 33.33% of off-nominal tasks were incomplete]; more errors on task record forms (td = 6 forms, rt = 1 form); higher ratings of workload burden (nominal, td workload = 38.64; off-nominal, td workload = 58.72; nominal, rt workload = 34.00, off-nominal, rt workload = 52.78). No significant changes in MC stress levels were detected in rt compared to td, but MCs did report greater stress during off-nominal tasks compared to nominal tasks. The crew, however, were unable to detect these changes in MC stress levels.

DISCUSSION: Overall, these findings point to the importance of future research focused on MC training and adapting MC’s operations for time-delayed missions. Further studies of time-delayed analog missions could help determine additional solutions focused on technology advances.

Diamond M, Leon GR, de León P. Mars mission communication delays and impact on mission controller performance, workload, and stress. Aerosp Med Hum Perform. 2025; 96(1):67–70.

INTRODUCTION: Assessment of fitness for flight constitutes one of the core tasks of aeromedical professionals. The value of such evaluations depends on the decision to be based on complete medical information, valid risk methodology, and genuine flight safety indicators. To achieve these goals, the aeromedical practitioner should ensure an evidence-based approach.

METHODS: This article describes a pragmatic and evidence-based methodology for aeromedical fitness assessments, grounded on already validated principles within scientific epistemology and evidence-based clinical medicine.

RESULTS: The aeromedical assessment should integrate both individual variables of the particular applicant, deductive reasoning by relevant experts, and the best available scientific evidence. Each of these three pillars includes a set of specific aspects based on knowledge of precision medicine, flight environment, risk methodology, statistics, metacognition, and scientific method.

DISCUSSION: Despite evidence-based approach being the benchmark, the aeromedical practitioner should be aware of limitations and potential pitfalls. The conclusion should be based on both functional performance and future risk of medical incapacitation using a transparent and objective risk matrix.

Saehle T. Evidence-based aeromedical assessments. Aerosp Med Hum Perform. 2025; 96(1):71–77.