Aerospace medicine and human performance最新文献

Introduction: Recent studies of quick-don aviator masks have challenged the traditional view that beards promote unacceptable leaks in close-fitting masks, suggesting instead that adequate respiratory protection remains. This new review aims to establish an updated position based on all available studies of close-fitting masks in bearded users.

Methods: Systematic searches identified eligible studies that evaluated the seal of close-fitting masks, intended to achieve optimal respiratory protection, in the presence of facial hair. Study quality was graded against five criteria: 1) study design (controls); 2) mask testing schedule; 3) bearded cohort size; 4) leak measurement method; and 5) representative testing (increased ventilatory demand, movements, and speech). Consideration was given to data meta-analysis.

Results: Of 21 discrete studies, 5 are rated high quality, 8 medium, and 8 low quality. Overwhelmingly, they indicate that facial hair can seriously degrade the performance of close-fitting masks, with relevant factors including beard age, hair length, and density. Early hair growth (days, possibly hours) can compromise seals at ambient gas supply pressure, with positive (safety) pressure supplies vulnerable to established beards, particularly at lower flow rates and increased ventilatory demands. Mask protection factors may degrade with facial hair by two or more orders of magnitude.

Discussion: Safety-critical close-fitting masks require a skin-tight seal. Mask seal integrity with facial hair is highly variable between individuals, between masks, and from one wear to the next. Quick-don close-fitting oxygen masks, required in aviation emergencies, will not function reliably unless the user is clean-shaven where the mask seal contacts the skin. Connolly D, Sheppard-Hickey R, Powell D, Lupa H. Sealing properties of close-fitting masks worn over facial hair. Aerosp Med Hum Perform. 2025; 96(12):1069-1078.

Introduction: Exposure to microgravity has physiological consequences that can impair astronaut safety and performance. Many can be directly linked to fluctuations in plasma serotonin levels on Earth, like bone loss, nausea, and fatigue. Yet the metabolic activity of serotonin in space is not well known. This study measured plasma serotonin levels and bone density in the mouse hindlimb unloading (HU) model, an established Earth analog of microgravity-induced bone loss.

Methods: The HU model has been used for decades to simulate axial unloading and fluidic shifts experienced in microgravity. Over a 30-d period, mice were suspended by their tails, with blood plasma collected at days 1, 15, and 30. Plasma was assessed for the presence of serotonin protein using an enzyme-linked immunosorbent assay and quantified. At day 30, microcomputed tomography of femur structural changes in HU mice was correlated with plasma serotonin increases.

Results: Serotonin in plasma from HU mice showed increases in plasma serotonin at every timepoint compared to normally loaded mice. Between days 15-30, there was a 1.87-fold increase in serotonin levels found for normal mice while a significantly larger increase of 2.5-fold was found in the HU mice.

Discussion: The HU mouse model showed plasma serotonin is elevated in HU mice, which corresponds to cortical and trabecular bone loss. These data suggest that elevated plasma serotonin may have a role in microgravity-induced bone loss. Specific serotonin receptor antagonists may be a safer countermeasure than currently used bisphosphonates to protect against astronaut bone loss. Casey TJ, Kubik AJ, Allen NG, Zilberman AH, Whitman BM, Hunt JC, Juran CM, French J, Blaber EA. Targeting serotonin pathways for astronaut safety and performance. Aerosp Med Hum Perform. 2025; 96(11):969-975.

Introduction: Acute mountain sickness (AMS) is a common condition in individuals ascending rapidly to high altitudes and often presents with headaches, fatigue, and gastrointestinal symptoms. AMS is prevalent above 13,000 ft (4000 m), but some individuals experience it at lower elevations. This pilot study assessed the prevalence and timing of AMS symptoms in unacclimatized individuals exposed to 16,000 ft (4900 m) in a controlled hypobaric environment.

Methods: A total of 10 healthy, unacclimatized men and women were exposed to an altitude of 16,000 ft (4900 m) for 5 h. Physiological parameters, including heart rate (HR), oxygen saturation (Spo2), and respiratory rate (RR), were recorded alongside AMS symptom severity using the 2018 Lake Louise Questionnaire (LLQ) and divided into low, moderate, and high responders based on severity.

Results: All subjects experienced some degree of AMS symptoms, with LLQ scores increasing over time. Two subjects could not complete the full exposure due to moderate and severe symptoms. HR increased (Δ = 7.0 ± 0.6), while Spo2 remained stable but lower than baseline (Δ = 9 ± 4.2). LLQ score increases were strongly correlated with HR, Spo2, and RR. RR remained stable across subjects but varied between AMS severity groups.

Discussion: This pilot study demonstrated that unacclimatized individuals rapidly exposed to 13,000 ft (4900 m) develop AMS symptoms in a controlled environment. The correlation between LLQ scores and physiological changes offers insight into AMS pathophysiology, supporting the need for further research into AMS susceptibility and genetic factors. Murphey JT, Hess HW, Schwob J, Monaco BA, Clemency BM, Hostler D. Acute mountain sickness symptoms after rapid ascent to 4900 m. Aerosp Med Hum Perform. 2025; 96(11):958-963.

Background: Elevated partial pressure of carbon dioxide (Pco2) poses a persistent health challenge during spaceflight. Unlike Earth's environment, the International Space Station experiences Pco2 levels that often exceed terrestrial safety thresholds, creating unique physiological risks for astronauts. In microgravity, localized Pco2 "pockets" can form due to lack of convection, exacerbating hypercapnic symptoms such as headaches, visual disturbances, and cognitive impairments. Moreover, microgravity-induced cephalad fluid shifts amplify the impact of CO2-mediated cerebral vasodilation, contributing to elevated intracranial pressure and potentially exacerbating spaceflight-associated neuro-ocular syndrome. Chronic hypercapnia also raises concerns about bone demineralization and renal stone formation, compounding mission risks. As we move toward longer missions to the Moon and Mars, mitigating CO2-related health effects through engineering controls, physiological countermeasures, and enhanced monitoring is essential. This article discusses current evidence and calls for integrated strategies to safeguard astronaut health and mission success under the compounded stressors of CO2 exposure and microgravity. Evans LA. Carbon dioxide as a multisystem threat in long duration spaceflight. Aerosp Med Hum Perform. 2025; 96(11):1024-1026.

Background: Spatial disorientation is a leading nontechnical cause of fatal military aviation accidents, triggered by insufficient or misleading cues mainly from the visual and vestibular systems. Spatial disorientation accounts for 20-38% of fatal military aviation accidents, but case reports describing specific illusions during actual flight are rare.

Case report: On a clear night, an aerial refueling tanker was cruising at 16,000 ft (4877 m), while an F-15I fighter aircraft was 3 mi behind and 971 ft (296 m) below. About 100 s before a near collision, the fighter pilot switched to Air-to-Air mode, displaying the distance and speed difference to the tanker via a Target Designator box on the Head-Up Display. However, the crew did not realize they were accelerating toward the tanker [from 597-663 ft · s-1 (182-202 m · s-1)] or climbing by 738 ft (225 m). The two aircraft came within 49 ft (15 m) of each other before the navigator noticed the tanker and initiated a roll to the left.

Discussion: The dip illusion occurs when a pilot flying in trail attempts to maintain the image of the lead aircraft in a fixed position on the windscreen as separation increases, which can lead to unintentional descent. In this case, we propose a "reverse-dip" illusion. The fighter crew was unaware they were closing in on the tanker, causing the Target Designator box to rise in the Head-Up Display. The pilot instinctively pulled back on the stick to maintain the box's position, resulting in an unintentional climb. Recognizing how such illusions develop in flight is essential to reducing future risks. Nakdimon I, Gordon B. Spatial disorientation event during flight due to proposed reverse-dip visual illusion. Aerosp Med Hum Perform. 2025; 96(11):1015-1018.

Introduction: Historical and modern science has produced many remedies for motion sickness; however, few if any of these remedies have demonstrated successful mitigation without producing negative side effects. The purpose of this study was to determine if a newly created commercial bone conducted vibration (BCV) device could reduce motion sickness symptoms in a simulated visual and provocative motion flight environment.

Methods: Subjects (N = 12) passively experienced two 30-min, auto-pilot simulated flights in a motion-based simulator while wearing a BCV device during experimental or placebo conditions. Trial condition presentations were counterbalanced to control potential order effects with a minimum of 1 d between trials. During each trial, subjects completed a tracking task and verbally reported subjective motion sickness ratings every 2 min. After completion of each trial, a Motion Sickness Assessment Questionnaire (MSAQ) was administered.

Results: No significant differences in overall MSAQ scores were observed between experimental (29.3 ± 19.4) and placebo (31.1 ± 17.4) BCV conditions. Significant differences in motion sickness scores were observed between the first (34.0 ± 17.6) and second (26.3 ± 18.4) trial sessions.

Discussion: The commercial BCV device did not affect the presence or absence of motion sickness during placebo or experimental conditions and had no effect on tracking task performance. During the second trial session, MSAQ scores were lower and time to nausea and failure were longer; however, observed increases in motion tolerance during the second trial sessions likely resulted from sensory adaptation and appeared to be unrelated to the BCV device. Patterson FR, Kaplan A, Gallimore D, Sherwood S, Horning D, Folga RV. Evaluation of a bone conducted vibration device designed for motion sickness mitigation. Aerosp Med Hum Perform. 2025; 96(11):993-999.

Introduction: Prolonged exposure to microgravity alters spinal biomechanics, increases disc herniation risk, and complicates perioperative care. With commercial and deep-space missions on the horizon, the need for in-orbit surgical capability has gained prominence as a safeguard for astronaut health.

Methods: A narrative review of PubMed, EMBASE, and Google Scholar through November 2024 identified human, animal, and in vitro studies addressing spinal physiology, pathology, or surgical feasibility in actual or simulated microgravity. Studies unrelated to the spine or lacking English full text were excluded.

Results: Of 988 records, there were 85 that met inclusion criteria. Across study types, microgravity consistently produced spinal elongation, disc swelling, vertebral bone loss, and muscle atrophy, leading to elevated postflight spinal morbidity. Although no spine operations have been reported in orbit, analog studies describe key intraoperative challenges, including fluid containment, sterility, imaging, anesthesia, and hemodynamic control. Promising countermeasures encompass bisphosphonates, resistive exercise, robot-assisted instrumentation, and teleoperation. These data offer a generalizable framework for perioperative planning during long-duration missions.

Discussion: Existing evidence clarifies physiological and logistic barriers to operative care. Targeted musculoskeletal countermeasures, coupled with tele-robotic and augmented-reality platforms, provide a realistic pathway to safe spine surgery during future long-duration missions. Further translational research and on-orbit validation are essential before clinical deployment. Birhiray D, Ghali A, Philipp T, Chilukuri S, Fiedler B, Lawand J, Deveza L. Spine surgery in space. Aerosp Med Hum Perform. 2025; 96(11):1000-1007.