INTRODUCTION: Firefighters operating in hot environments face challenges from protective garments that restrict heat dissipation, resulting in increased core temperature, thermal discomfort, and performance decline. Cooling vests represent a viable solution. The study aim was to compare effectiveness of the same amount of cooling power to the upper body (UB) or whole body (WB) in alleviating thermoregulatory and physiological stress, enhancing cognitive function, and reducing ratings of thermal discomfort and exertion, during 60 min of exercise in a hot environment (40°C, 40% relative humidity) while wearing firefighter turnout gear.

METHODS: Eight healthy individuals (27.5 ± 3 y) participated in three conditions with either no cooling (Control) or active cooling with a liquid perfused shirt (UB cooling), or with a liquid perfused shirt and pants (WB cooling). In each trial, subjects performed three sets of 15 min of stepping (20 steps ⋅ min⁻¹) and 5 min of rest.

RESULTS: Both cooling strategies were beneficial compared to having no cooling at all. Subjects could only complete two exercise bouts during Control, but they completed all three bouts with active cooling. WB cooling provided an advantage over UB cooling for core and skin temperature, and thermal comfort and sensation. The advantage in minimizing the increase in core temperature was only evident during the third exercise bout.

DISCUSSION: Active cooling is advantageous under these conditions. WB cooling provided some benefits vs UB cooling during heavy intensity exercise; however, it is uncertain whether these benefits would be observed during light-to-moderate exercise, which more likely reflects an actual firefighting scenario.

Mansouri F, Talebian Nia M, Villar R, Cornish SM, Giesbrecht GG. Upper- vs. whole-body cooling during exercise with thermal protective clothing in the heat. Aerosp Med Hum Perform. 2024; 95(9):659–666.

INTRODUCTION: Biomarker responses to intensive decompression indicate systemic proinflammatory responses and possible neurological stress. To further investigate responses, 12 additional brain and lung biomarkers were assayed.

METHODS: A total of 15 healthy men (20 to 50 yr) undertook consecutive same-day ascents to 25,000 ft (7620 m), following denitrogenation, breathing 100% oxygen. Venous blood was sampled at baseline (T0), after the second ascent (T8), and next morning (T24). Soluble protein markers of brain and lung insult were analyzed by enzyme-linked immunosorbent assay with plasma microparticles quantified using flow cytometry.

RESULTS: Levels of monocyte chemoattractant protein-1 and high mobility group box protein 1 were elevated at T8, by 36% and 16%, respectively, before returning to baseline. Levels of soluble receptor for advanced glycation end products fell by 8%, recovering by T24. Brain-derived neurotrophic factor rose by 80% over baseline at T24. Monocyte microparticle levels rose by factors of 3.7 at T8 and 2.7 at T24 due to early and late responses in different subjects. Other biomarkers were unaffected or not detected consistently.

DISCUSSION: The elevated biomarkers at T8 suggest a neuroinflammatory response, with later elevation of brain-derived neurotrophic factor at T24 indicating an ongoing neurotrophic response and incomplete recovery. A substantial increase at T8 in the ratio of high mobility group box protein 1 to soluble receptor for advanced glycation end products suggests this axis may mediate the systemic inflammatory response to decompression. The mechanism of neuroinflammation is unclear but elevation of monocyte microparticles and monocyte chemoattractant protein-1 imply a key role for activated monocytes and/or macrophages.

Connolly DM, Madden LA, Edwards VC, Lee VM. Brain and lung biomarker responses to hyperoxic hypobaric decompression. Aerosp Med Hum Perform. 2024; 95(9):667–674.

INTRODUCTION: Military aviation poses unique occupational risks, including exposures to intermittent hypoxia, high gravitational force, and toxic materials, in addition to circadian disruption, cosmic radiation, and ergonomic stressors also present in commercial flight. We sought to investigate whether a military aviation officer’s career is associated with adverse maternal or fetal health outcomes.

METHODS: We conducted a retrospective cohort study of female aviation and nonaviation officers in the Military Health System from October 2002 to December 2019. Exposure was identified as assignment of an aviation occupation code. Maternal and fetal health outcomes were identified by International Classification of Diseases codes from medical records. Regression analysis was used to estimate adjusted relative risks (aRR).

RESULTS: Included in the study were 25,929 active-duty female officers, with 46,323 recorded pregnancies and 32,853 recorded deliveries; 2131 pregnancies were diagnosed in aviation officers. Pregnant aviation officers had a decreased risk of composite adverse pregnancy outcomes [aRR 0.82 (0.73–0.92)], including gestational diabetes [aRR 0.69 (0.57–0.85)] and gestational hypertension [aRR 0.84 (0.71–0.99)]. Pregnant aviation officers had a decreased risk of depression prior to delivery [aRR 0.43 (0.35–0.53)] and hyperemesis gravidarum [aRR 0.74 (0.57–0.96)], but an increased risk of placental complications [aRR 1.15 (1.02–1.30)] and fetal growth restriction [aRR 1.36 (1.16–1.60)].

DISCUSSION: Pregnant military aviation officers have an increased risk of placental complications and fetal growth restriction in spite of a lower risk of gestational diabetes and gestational hypertension. Further research is needed to determine how flight-related occupations impact pregnancy.

Stark CM, Sorensen IS, Royall M, Dorr M, Brown J, Dobson N, Salzman S, Susi A, Hisle-Gorman E, Huggins BH, Nylund CM. Maternal and fetal health risks among female military aviation officers. Aerosp Med Hum Perform. 2024; 95(9):675–682.

INTRODUCTION: Pilots are frequently exposed to thrombotic risk as a result of immobility from air travel. As hypoxemia is associated with secondary polycythemia, and polycythemia increases the risk of thrombosis, intermittent exposure to high-altitude hypoxic environments could escalate the risk of thrombosis in pilots. Our objectives were to find the prevalence of polycythemia in airplane pilots (primary outcome) and to assess associated risk factors of polycythemia (secondary outcome).

METHODS: This study is a cross-sectional descriptive study. Data was collected from paper-based and computerized medical records of airplane pilots who applied for Class 1 Aviation Medical Certificate renewal at the Institute of Aviation Medicine, Royal Thai Air Force, Bangkok, Thailand, in 2018. The data was sampled by a simple random sampling technique.

RESULTS: A total of 386 paper-based records were sampled. Of those, 29 (7.5%) of the pilots met polycythemia criteria. Spearman’s correlation analysis showed a significant positive correlation between Body Mass Index (BMI) and hemoglobin (correlation coefficient = 0.127) and between BMI and hematocrit (correlation coefficient = 0.105). In multivariate logistic regression of each variable on polycythemia as defined by hemoglobin alone, piloting a non-pressurized aircraft was found to be an independent predictor of polycythemia (odds ratio = 4.3).

DISCUSSION: The prevalence of polycythemia in airplane pilots was 7.5%. Operating a non-pressurized aircraft was a significant risk factor of polycythemia, and pilots with higher BMI were more likely to have increased red blood cell parameters.

Thanapaisan P, Plaingam M, Manyanont S. Polycythemia prevalence and risk factors in pilots. Aerosp Med Hum Perform. 2024; 95(9):683–687.

INTRODUCTION: The benefits of using head-up displays (HUDs) include reducing head-down time during critical flight phases, enhancing awareness of the external environment, and improving in-flight crew performance. However, the monochromatic nature of HUDs, increased head rotation, and longer gaze movement paths might affect pilots’ reactions to different types of alerts.

METHODS: Pilot workload and behavior differences were examined between HUD and head-down display (HDD) configurations in three alert scenarios. The study was carried out in an A320 flight simulator and 12 pilots participated.

RESULTS: Except for one engine-on-fire scenario, pilot workload when using a HUD was significantly lower than using an HDD. In one engine-on-fire (3.98 s vs. 3.57 s) and one gear-disagree (5.42 s vs. 4.69 s) scenario, pilot response time to alerts using HUD was significantly longer than using an HDD. The angle deviations were significantly smaller when using HUDs in both go-around-under-crosswind (2.67° vs. 3.37°) and one engine-on-fire scenario (1.22° vs. 1.89°).

DISCUSSION: The HUD is suitable for a lengthy process of manual flight control inputs, which not only reduces workload but also promotes control accuracy. For tasks that rely on automation, the benefits for workload become less obvious. In addition, head rotation and reorientation of attention adversely affected the response time to non-time-critical warnings and cautions. For instantaneous control with high precision requirements, HUDs did not demonstrate a significant advantage.

Zheng Y, Lu Y, Jie Y, Fu S. Pilots’ reactions to different types of alerts when using head-up displays. Aerosp Med Hum Perform. 2024; 95(9):688–694.

INTRODUCTION: No current astronauts have surgical training, and medical capabilities for future missions do not account for it. We sought to determine the effect of communication delays and text-based communication on emergency medicine physician (EMP) performance of a simulated surgical procedure and the ideal training paradigm for remote surgery.

METHODS: In this study, 12 EMPs performed an appendectomy on a virtual reality laparoscopic simulator after tutorial. EMPs were randomized into two groups: one (bedside) group performing with bedside directing from a surgeon and the second (remote) group performing with text-based communications relayed to the surgeon after a 210-s time delay. Both groups performed a second simulated surgery 7 mo later with 240-s delay. Collected data included time to completion, number of movements, path length, economy of motion, percentage of time with appropriate camera positioning, texts sent, and major complications.

RESULTS: The remote group took significantly longer to complete the task, used more total movements, had longer path length, and had significantly worse economy of motion during the initial trial. At the 7-mo simulation, there were no significant differences between the two groups. There was a nonsignificant increase in critical errors in the remote group at follow-up (50% vs. 20% of trials).

DISCUSSION: EMPs are technically able to perform a surgical operation with delayed just-in-time telementoring guidance via text-based communication. However, the ideal paradigm for training non-surgeons to perform surgical operations is unclear but is likely real-time bedside training rather than remote training.

Kamine TH, Siu M, Stegemann S, Formanek A, Levin D. Long round-trip time delay effects on performance of a simulated appendectomy task. Aerosp Med Hum Perform. 2024; 95(9):703–708.

INTRODUCTION: The European Air Transport Command (EATC) is a seven-nation integrated command. One of its core capabilities is strategic aeromedical evacuation (AE). During the global COVID-19 pandemic and Ukrainian crisis, EATC proved that acting in concert is a valuable, effective, and reliable option.

METHODS: By pooling and sharing aircraft and personnel, EATC has privileged access to a diverse fleet and pool of experts. Cooperation is based on a common set of rules and regulations, which ensures that EATC can address any problem with expertise.

RESULTS: During the COVID-19 pandemic, 1060 COVID-19-positive patients were transported in 198 missions, with neither death nor disease transmission reported during those strategic AE flights. EATC transferred 986 military cases, mostly routine priority (91.4%); the other 74 cases were civilians, who were transported in 17 missions, with 81.1% categorized as urgent. During the Ukrainian crisis, 251 patients were transported, 112 military and 139 civilians, including 30 children. Among the recorded injuries were cerebrocranial, abdominal, and chest injuries, as well as fractures (180) and amputations (48) of the extremities.

DISCUSSION: EATC is recognized as a center of expertise within the AE community, where interoperability and harmonization of concepts are key to safety and success. Cross-national missions, where a patient is evacuated by an aircraft and medical crew provided by another nation, offer maximum flexibility. Complex situations, such as the COVID-19 pandemic and the Ukrainian crisis, have shown that multinational cooperation is not only achievable but also provides robust, effective, and reliable solutions for AE in particular.

Fiorini A, Vermeltfoort R, Dulaurent E, Hove MG, Borsch M. Cross-national strategic aeromedical evacuation at the European Air Transport Command. Aerosp Med Hum Perform. 2024; 95(9):709–715.

INTRODUCTION: Accessible spaceflight may seem a distant concept. As part of a diverse European Space Agency funded Topical Team, we are working on the physiological feasibility of space missions being undertaken by people with physical disabilities. Here, the first activity of this team is presented in the form of key lessons learned from aviation to inform new work on space missions.

DISCUSSION: The first lesson is agreeing on realistic expectations about impairments, their severity, and the possibility of flying independently. This is important in terms of astronaut recruitment and societal expectations. The second lesson relates to training and adjustments for people with disabilities. Flexibility is important while maintaining safety for everyone involved. The third lesson is about managing unconscious bias from the different stakeholders. We conclude by arguing that engagement with people from different backgrounds is essential for the success of the first space mission with people with physical disabilities.

Miller-Smith MJ, Tucker N, Anderton R, Caplin N, Harridge SDR, Hodkinson P, Narici MV, Pollock RD, Possnig C, Rittweger J, Smith TG, Di Giulio I. Lessons for flying astronauts with disabilities drawn from experience in aviation. Aerosp Med Hum Perform. 2024; 95(9):716–719.

INTRODUCTION: Human colonization of Mars has captured the imagination of many. However, the challenges posed are immense. In microgravity, changes in human physiology, immune dysregulation, alterations of our microbiome, and enhanced virulence of various microbes are some of the barriers that stand in the way of a successful endeavor. Countermeasures can be brought to bear, but it remains unclear if success of such a mission in the foreseeable future is realistic or fanciful.

Mermel L. Human evolution, microgravity, and challenges colonizing Mars. Aerosp Med Hum Perform. 2024; 95(9):720–721.

Use of onboard commercial airline defibrillators began in 1997. At first, it was met with resistance but is now present on all planes. The first in-flight resuscitation of a passenger occurred in 1998 and is described here.