A Method to Determine Capabilities and Resources for Spacecraft Medical Systems.

INTRODUCTION: This paper describes the method for assigning medical diagnostic and treatment capabilities and resources to the database which assists with an updated probabilistic risk analysis (PRA) tool for exploration class medical system planning. The National Aeronautics and Space Administration has used PRA since 2011 to inform mission medical system design, but existing tools are designed only for low Earth orbit. An updated PRA tool was needed to assist with exploration class missions.METHODS: A team of medical experts with a wide range of expertise and experience, including Space Medicine, was assembled to build capability and resource tables for the new PRA tool. This team met over 8 mo and used practice guidelines, literature, and experience to build capability and resource tables (CRTs) for each condition in the new PRA tool database.RESULTS: This process led to CRTs for each condition and a total of 617 distinct capabilities and 839 discrete resources.CONCLUSION: The CRT method is an effective way to translate medical practice guidelines into capabilities and resources usable by PRA tools for exploration class medical system planning. This same method may be used in commercial space ventures and in other applications in which medical predictive analytics are informative.Levin DR, Nelson AM, Zahner C, Stratton ER, Anderson A, Steller J. A method to determine capabilities and resources for spacecraft medical systems. Aerosp Med Hum Perform. 2024; 95(7):403-408.

Revisions to Limits for Toluene in Spacecraft Air.

INTRODUCTION: The original Spacecraft Maximal Allowable Concentrations (SMACs) for toluene (set for 1 h, 24 h, 7 d, 30 d, and 180 d) were first established by NASA in 1996 based on a human study in which no irritation or neurotoxicity was reported following 6-h exposure to 40 ppm toluene vapors. While the toluene SMACs were updated in 2008 to account for auditory, visual, and hormonal effects (for 7 d, 30 d, and 180 d) and to include a long-term SMAC (1000 d) in anticipation of longer spaceflight exploration missions, the short-term SMAC limits (1 h and 24 h) remained unchanged. Acute toluene exposure is reported to result in ocular and nasal irritation, although it is not a primary irritant, as well as central nervous system effects including headaches and dizziness. Long-term exposure to toluene can elicit hepatotoxicity, nephrotoxicity, neurotoxicity, and endocrine toxicity.RESULTS AND DISCUSSION: Since publication of the original and revised toluene SMACs, the National Academy of Sciences developed interim Acute Exposure Guideline Limits reviewed by the National Research Council Committee. Based on these data, we have increased the limits for toluene in crewed spacecraft to 40 ppm for 1 h, 24 h, 7 d, and 30 d. SMACs for durations of 180 and 1000 d will remain unchanged.changed.Tapia CM, Langford SD, Ryder VE. Revisions to limits for toluene in spacecraft air. Aerosp Med Hum Perform. 2024; 95(7):399-402.

Circadian Disruption in Civilian Airline Pilots.

INTRODUCTION: Most airline pilots reported having suffered from sleep disorders and fatigue due to circadian disruption, a potential risk to flight safety. This study attempted to uncover the actual scenario of circadian disruption and working load status among airline pilots.METHODS: In study 1, 21 pilots were invited to participate in a 14-d sleep monitoring and a dual 2-back test to monitor their sleep patterns and cognitive function level. To provide an in-depth view, data from scheduled flights, including 567 airline pilots, was analyzed in Study 2. The present study used cluster analysis to reflect the distribution of the flight scheduling characteristics, including working time and actual working hours. A simulation model was then developed to predict the pilots' 1-mo sleep-wake pattern.RESULTS: The results indicated that sleep problems were prevalent in this population, especially the night before an earlier morning shift. Regarding the cognitive test, they scored the lowest on earlier morning shifts compared with daytime and evening shifts. It was found that over 70% of the flight schedules can lead to circadian disruption, and 47.44% of the pilots worked under high-load status.DISCUSSION: Airline pilots inevitably work irregular hours and the current policies for coping with circadian disruption seem inefficient. This study thus calls for urgency in improving scheduling and fatigue management systems from the circadian rhythm perspective.Yang SX, Cheng S, Sun Y, Tang X, Huang Z. Circadian disruption in civilian airline pilots. Aerosp Med Hum Perform. 2024; 95(7):381-389.

Relative Severity of Human Performance Decrements Recorded in Rapid vs. Gradual Decompression.

INTRODUCTION: Cabin decompression presents a threat in high-altitude-capable aircraft. A chamber study was performed to compare effects of rapid (RD) vs. gradual decompression and gauge impairment at altitude with and without hypoxia, as well as to assess recovery.METHODS: There were 12 participants who completed RD (1 s) and Gradual (3 min 12 s) ascents from 2743-7620 m (9000-25000 ft) altitude pressures while breathing air or 100% O2. Physiological indices included oxygen saturation (SPo2), heart rate (HR), respiration, end tidal O2 and CO2 partial pressures, and electroencephalography (EEG). Cognition was evaluated using SYNWIN, which combines memory, arithmetic, visual, and auditory tasks. The study incorporated ascent rate (RD, gradual), breathing gas (air, 100% O2) and epoch (ground-level, pre-breathe, ascent-altitude, recovery) as factors.RESULTS: Physiological effects in hypoxic "air" ascents included decreased SPo2 and end tidal O2 and CO2 partial pressures (hypocapnia), with elevated HR and minute ventilation (V˙E); SPo2 and HR effects were greater after RD (-7.3% lower and +10.0 bpm higher, respectively). HR and V˙E decreased during recovery. SYNWIN performance declined during ascent in air, with key metrics, including composite score, falling further (-75% vs. -50%) after RD. Broad cognitive impairment was not recorded on 100% O2, nor in recovery. EEG signals showed increased slow-wave activity during hypoxia.DISCUSSION: In hypoxic exposures, RD impaired performance more than gradual ascent. Hypobaria did not comprehensively impair performance without hypoxia. Lingering impairment was not observed during recovery, but HR and V˙E metrics suggested compensatory slowing following altitude stress. Participants' cognitive strategy shifted as hypoxia progressed, with efficiency giving way to "satisficing," redistributing effort to easier tasks.Beer J, Mojica AJ, Blacker KJ, Dart TS, Morse BG, Sherman PM. Relative severity of human performance decrements recorded in rapid vs. gradual decompression. Aerosp Med Hum Perform. 2024; 95(7):353-366.

Increased Functional Connectivity Between the Parietal and Occipital Modules Among Flight Cadets.

INTRODUCTION: Modular organization in brain regions often performs specific biological functions and is largely based on anatomically and/or functionally related brain areas. The current study aimed to explore changes in whole-brain modular organization affected by flight training.METHODS: The study included 25 male flight cadets and 24 male controls. The first assessment was performed in 2019, when the subjects were university freshmen. The second assessment was completed in 2022. High spatial resolution structural imaging (T1) and resting-state functional MRI data were collected. Then, 90 cerebral regions were organized into 6 brain modules. The intensity of intra- and intermodular communication was calculated.RESULTS: Mixed-effect regression model analysis identified significantly increased interconnections between the parietal and occipital modules in the cadet group, but significantly decreased interconnections in the control group. This change was largely attributed to flight training.DISCUSSION: Pilots need to control the aircraft (e.g., attitude, heading, etc.) using the stick and pedal in response to the current state of the aircraft displayed by the instrument panel; as such, flying requires a large amount of hand-eye coordination. Day-to-day flight training appeared to intensify the connection between the parietal and occipital modules among cadets.Chen X, Jiang H, Meng Y, Xu Z, Luo C. Increased functional connectivity between the parietal and occipital modules among flight cadets. Aerosp Med Hum Perform. 2024; 95(7):375-380.

Galvanic Vestibular Stimulation Advancements for Spatial Disorientation Training.

INTRODUCTION: Spatial disorientation (SD) remains the leading contributor to Class A mishaps in the U.S. Navy, consistent with historical trends. Despite this, SD training for military aircrew is largely confined to the classroom and experiential training replicating SD illusions is limited and infrequent. Static flight simulators are most commonly used for training but offer no vestibular stimulation to the flight crew, omitting the source of vestibular-mediated SD.BACKGROUND: We first cover vestibular-mediated SD illusions which may be replicated through galvanic vestibular stimulation (GVS) in a static environment. GVS is a safe, reliable, low-cost avenue for providing vestibular sensory stimulation. We review the underlying mechanisms of GVS such as the excitement and inhibition of the afferent neurons innervating the vestibular system, particularly in the binaural bipolar electrode montage.APPLICATIONS: Two approaches for how GVS may be used to enhance SD training are examined. The first is a means for providing unreliable vestibular sensory perceptions to pilots, and the second details how GVS can be leveraged for replicating vestibular-mediated SD illusions.DISCUSSION: We recommend GVS be pursued as an enhancement to existing SD training. The ability to disorient aircrew in the safe training environment of a static flight simulator would allow for aircrew familiarization to SD, serving as an opportunity to practice life-saving checklist items to recover from SD. A repeatable training profile that could be worn by military aircrew in a static flight simulator may afford a low-cost training solution to the number one cause of fatalities in military aviation.Allred AR, Lippert AF, Wood SJ. Galvanic vestibular stimulation advancements for spatial disorientation training. Aerosp Med Hum Perform. 2024; 95(7):390-398.

Photorefractive Keratectomy in Experienced U.S. Naval Aviators: A Prospective Evaluation.

PURPOSE: To report on the prospective evaluation of photorefractive keratectomy (PRK) in experienced ametropic naval aviators that led to the approval of refractive surgery for military pilots. METHODS: This was the first study evaluating refractive surgery in naval aviators. Return to flight status after PRK and clinical outcomes and subjective and objective flight performance were evaluated. RESULTS: A total of 785 U.S. naval aviators were enrolled in the study. Average preoperative refraction was -2.92 ± 1.73 diopters (D) (range: +5.25 to -9.13 D). By 6 months, 85.9% of eyes were within ±0.50 D and 96.4% were within ±1.00 D of emmetropia. 94.4% of eyes achieved 20/20 or better, 74.3% had 20/16 or better, and 45.2% had 20/12.5 or better uncorrected distance visual acuity (UDVA) at 6 months. A total of 78.5% of aviators met return-to-flight criteria by 4 weeks, 83.3% by 8 weeks, and 90.8% by 12 weeks following PRK. All aviators eventually returned to full flight status. Cumulative flight experience included logging more than 48,000 flight hours and 19,500 landings in the 6 months following PRK. Psychometric questionnaire results showed that 78% reported improved ability to detect other aircraft and 92% reported improved ability to land on an aircraft carrier (82% significantly improved) compared to wearing corrective lenses. No one felt their vision was worse in these dynamic environments. All aviators indicated they would undergo the procedure again and would recommend it to a fellow aviator. CONCLUSIONS: This prospective study in U.S. naval aviators determined PRK to be safe and effective in a unique patient population operating in a visually demanding and hazardous environment. The program continues to be enthusiastically supported by aviators and PRK is now allowed in all branches of the military and for National Aeronautics and Space Administration astronauts. [J Refract Surg. 2024;40(6):e371-e380.].

Practice effects of a breathing technique on pilots' cognitive and stress associated heart rate variability during flight operations.

Commercial pilots endure multiple stressors in their daily and occupational lives which are detrimental to psychological well-being and cognitive functioning. The Quick coherence technique (QCT) is an effective intervention tool to improve stress resilience and psychophysiological balance based on a five-minute paced breathing exercise with heart rate variability (HRV) biofeedback. The current research reports on the application of QCT training within an international airline to improve commercial pilots' psychological health and support cognitive functions. Forty-four commercial pilots volunteered in a one-month training programme to practise self-regulated QCT in day-to-day life and flight operations. Pilots' stress index, HRV time-domain and frequency-domain parameters were collected to examine the influence of QCT practice on the stress resilience process. The results demonstrated that the QCT improved psychophysiological indicators associated with stress resilience and cognitive functions, in both day-to-day life and flight operation settings. HRV fluctuations, as measured through changes in RMSSD and LF/HF, revealed that the resilience processes were primarily controlled by the sympathetic nervous system activities that are important in promoting pilots' energy mobilization and cognitive functions, thus QCT has huge potential in facilitating flight performance and aviation safety. These findings provide scientific evidence for implementing QCT as an effective mental support programme and controlled rest strategy to improve pilots' psychological health, stress management, and operational performance.

Safety and Risk in Airway Management During Bariatric Air Medical Retrieval.

OBJECTIVE: Bariatric anatomy and physiology present added clinical challenges to the provision of safe critical care and patient transport. LifeFlight Retrieval Medicine provides air medical retrieval services in Queensland, Australia, and performs over 6,000 retrieval missions annually using rotary wing, fixed wing, and ground ambulance platforms. METHODS: Bariatric patient retrievals were identified from the LifeFlight Retrieval Medicine electronic patient database. These cases were interrogated to quantify and describe adverse events during patient transport. RESULTS: Over the study period from July 2019 to December 2021 11,096 patient retrievals were completed. Of these patients, 816 (7.3%) had a body weight ≥ 120 kg (range, 120-246 kg; median = 146 kg). Bariatric patients were more likely to be male (70%) and to require critical care interventions than nonbariatric patients (25.9% vs. 19.9%). There was an absolute 1.5% increase of high-interest events during patient retrieval, corresponding to a 1.9-fold increased relative risk. Five hundred eleven of 11,096 patients were intubated by the retrieval team, and 61 of these weighed ≥ 120 kg. Bariatric patients undergoing intubation were of similar age and sex, weighed significantly more, had nonsignificant trends toward poorer airway visualization by Cormack-Lehane laryngoscopic grade, and tended toward reduced first-attempt success compared with nonbariatric patients. Rates of airway adverse events (AAEs) were significantly increased for the bariatric group (30/61, 49.2%) compared with the nonbariatric group (135/450, 30.0%) (χ2 likelihood ratio, P = .004). Postintubation desaturation was the most common AAE and was the only criterion significantly increased when comparing bariatric (26%) versus nonbariatric (12%) patients (χ2 likelihood ratio, P = .005). Using patient weight as a continuous variable, nominal logistic regression revealed a significant effect of increasing weight on AAEs (χ2 = 12.9, P = .0003) with a threshold of 105 kg providing an optimal 88% sensitivity for predicting AAEs. The odds of AAEs were increased significantly for those weighing 105 to 119 kg versus those weighing < 105 kg (odds ratio [OR] = 3.4; 95% confidence interval [CI], 1.6-7.5) and for those weighing ≥ 120 kg versus those weighing < 105 kg (OR = 2.5; 95% CI, 1.4-4.3). There was no difference between those weighing ≥ 120 kg versus those weighing 105 to 119 kg (OR = 0.73; 95% CI, 0.3-1.8). CONCLUSION: Air medical retrieval of bariatric patients is safe despite an increased risk of adverse events. Strategies to optimize emergency anesthesia should be used to maximize safe intubation in bariatric patients.

Spaceflight Environment.

The safety and health of individuals who may be exposed to the spaceflight environment are first and foremost cared for through prevention. This environment, which encompasses microgravity, radiation, and alternobaric factors, can have physiologic impacts on every human system. Available medical care and resources in the spaceflight environment are currently limited by mass and volume constraints, with available medical resources thereby focusing on a patient's stabilization and evacuation. An understanding of the spaceflight environment and its possible effects is crucial for the treatment of individuals prior to, during, and after spaceflight.

Re-evaluating the Need for Routine Maximal Aerobic Capacity Testing within Fighter Pilots.

INTRODUCTION: There is a current belief in aviation suggesting that aerobic training may reduce G-tolerance due to potential negative impacts on arterial pressure response. Studies indicate that increasing maximal aerobic capacity (V˙o2 max) through aerobic training does not hinder G-tolerance. Moreover, sustained centrifuge training programs revealed no instances where excessive aerobic exercise compromised a trainee's ability to complete target profiles. The purpose of this review article is to examine the current research in the hope of establishing the need for routine V˙o2-max testing in air force pilot protocols.METHODS: A systematic search of electronic databases including Google Scholar, PubMed, the Aerospace Medical Association, and Military Medicine was conducted. Keywords related to "human performance," "Air Force fighter pilots," "aerobic function," and "maximal aerobic capacity" were used in various combinations. Articles addressing exercise physiology, G-tolerance, physical training, and fighter pilot maneuvers related to human performance were considered. No primary data collection involving human subjects was conducted; therefore, ethical approval was not required.RESULTS: The V˙o2-max test provides essential information regarding a pilot's ability to handle increased Gz-load. It assists in predicting G-induced loss of consciousness by assessing anti-G straining maneuver performance and heart rate variables during increased G-load.DISCUSSION: V˙o2-max testing guides tailored exercise plans, optimizes cardiovascular health, and disproves the notion that aerobic training hampers G-tolerance. Its inclusion in air force protocols could boost readiness, reduce health risks, and refine training for fighter pilots' safety and performance. This evidence-backed approach supports integrating V˙o2-max testing for insights into fitness, risks, and tailored exercise.Zeigler Z, Acevedo AM. Re-evaluating the need for routine maximal aerobic capacity testing within fighter pilots. Aerosp Med Hum Perform. 2024; 95(5):273-277.

Worldwide Regulation of the Medical Emergency Kit and First Aid Kit.

INTRODUCTION: On-board medical emergencies are increasing. Different geographies have different legislation and requirements for medical emergency kits and first aid kits. A comprehensive review to compare the contents of both kits was conducted, including the International Air Transport Association, European Union Aviation Safety Agency, and Federal Aviation Administration, as well as some from other geographical areas of the globe to cover continents and regions with the highest air traffic, such as Brazil, Kenya, Australia, and Taiwan.METHODS: On June 10, 2023, a search was conducted using standardized medical terms (medical subject headings) within the PubMed® database. The relevant terms identified were "Aircraft" and "Medical Emergencies"; articles published within the last 10 yr were filtered. Subsequently, even articles published before 2013 were consulted if cited by the initial ones. The main regulatory entities' documentation was found using the Google search engine and consulted.CONCLUSIONS: It is impossible to be prepared for every emergency on board. Still, as doctors, we have a moral and ethical obligation to try to improve the outcomes of those emergencies. Getting a standardized report of every on-board emergency is crucial. That would make optimizing the items to include in the emergency and first aid kits easier. There are many similarities among the compared entities, but essential differences have been found. There is room for improvement, especially for pediatric travelers.Oliveira ATB. Worldwide regulation of the medical emergency kit and first aid kit. Aerosp Med Hum Perform. 2024; 95(6):321-326.

Photorefractive Keratectomy and Laser-Assisted In Situ Keratomileusis on 6-Month Space Missions.

BACKGROUND: This article documents the stability of photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK) in two astronauts during 6-mo missions to the International Space Station.CASE REPORTS: Ocular examinations including visual acuity, cycloplegic refraction, slit lamp examination, corneal topography, central corneal thickness, optical biometry (axial length/keratometry), applanation tonometry, and dilated fundus examination were performed on each astronaut before and after their missions, and in-flight visual acuity testing was done on flight day 30, 90, and R-30 (30 d before return). They were also questioned regarding visual changes during flight.DISCUSSION: We documented stable vision in both PRK and LASIK astronauts during liftoff, entry into microgravity, 6 mo on the International Space Station, descent, and landing. Our results suggest that both PRK and LASIK are stable and well tolerated during long-duration spaceflight.Gibson CR, Mader TH, Lipsky W, Schallhorn SC, Tarver WJ, Suresh R, Hauge TN, Brunstetter TJ. Photorefractive keratectomy and laser-assisted in situ keratomileusis on 6-month space missions. Aerosp Med Hum Perform. 2024; 95(5):278-281.

Global Cardiovascular Risk and Associated Factors in 2792 French Military and Civilian Aircrew.

INTRODUCTION: Cardiovascular (CV) diseases are a major public health issue, the prevention of which plays a key role in promoting flight safety. However, few studies have looked at the determinants of the overall risk of CV morbidity-mortality within the various aeronautical occupations.METHODS: A monocentric, observational, cross-sectional study was based on the retrospective data collected during 6 mo at the Toulon Aeromedical Center. From October 2017 to April 2018, 2792 professional aircrew ages 18-74 were included. The overall CV risk was estimated using the European Society of Cardiology SCORE and the Framingham model, as well as a summation model.RESULTS: More than two-thirds of this mainly male population (86.2%) had no more than one CV risk factor [69.9% (68.2-71.6)]. In 82.5% of cases, this was dyslipidemia according to current European criteria [55.8% (52.4-59.1)] or smoking [26.7% (23.8-29.8)]. An overall risk level of "moderate" to "very high" concerned only one subject in five according to the SCORE model [20.1% (18.6-21.6)], one in six according to Framingham [16.3% (14.9-17.7)] and almost one in three according to the summation model [30.1% (28.4-31.9)].DISCUSSION: Multivariate analyses found no significant associations between socio-professional criteria and overall risk levels. The results have underlined the effect of dyslipidemia and smoking on early risk among applicants. Beyond the illustration of favorable cardiovascular status among aircrews related to the standards of selection and close monitoring process, areas for improvement were identified, inviting the development of prevention strategies around the "moderate" overall CV risk.Huiban N, Gehant M, Brocq F-X, Collange F, Mayet A, Monteil M. Global cardiovascular risk and associated factors in 2792 French military and civilian aircrew. Aerosp Med Hum Perform. 2024; 95(5):233-244.

Fatigue Risk Management Preferences for Consumer Sleep Technologies and Data Sharing in Aviation.

INTRODUCTION: Employees from any type of aviation services industry were asked to give their opinions about the usefulness of consumer sleep technologies (CSTs) during operations and their willingness to share data from CSTs with their organizations for fatigue risk management purposes under a variety of circumstances.METHODS: Respondents provided information about position in aviation and use of CST devices. Respondents ranked sleep issues and feedback metrics by perceived level of importance to operational performance. Respondents rated their likelihood to share data with their organization under a series of hypothetical situations.RESULTS: Between January-July 2023, 149 (N = 149) aviation professionals responded. Pilots comprised 72% (N = 108) of respondents; 84% (N = 125) of all respondents worked short- or medium-haul operations. "Nighttime operations" and "inconsistent sleep routines" ranked as the most important issues affecting sleep. "Sleep quality history" and "projected alertness levels" ranked as most important feedback metrics for personal management of fatigue. Respondents were split between CST users (N = 64) and nonusers (N = 68). CST users did not indicate a strong preference for a specific device brand. The most-reported reason for not using a CST was due to not owning one or no perceived need. Respondents indicated greater likelihood of data sharing under conditions where the device was provided to them by their organization.DISCUSSION: These results suggest that aviation professionals are more concerned about schedule-related disturbances to sleep than they are about endogenous sleep problems. Organizations may be able to increase compliance to data collection for fatigue risk management by providing employees with company-owned CSTs of any brand.Devine JK, Choynowski J, Hursh SR. Fatigue risk management preferences for consumer sleep technologies and data sharing in aviation. Aerosp Med Hum Perform. 2024; 95(5):265-272.