INTRODUCTION: Aerobatic flight operations involve a higher level of risk than standard flight operations. Aerobatics imposes considerable stresses on both the aircraft and the pilot. The purpose of this study was to analyze civilian aerobatic aircraft accidents in Australia, with particular emphasis on the underlying accident causes and survival outcomes.METHODS: The accident and incident database of the Australian Transport Safety Bureau was searched for all events involving aerobatic flight for the period 19802010.RESULTS: A total of 51 accidents involving aircraft undertaking aerobatic operations were identified, with 71 aircraft occupants. Of the accidents, 27 (52.9) were fatal, resulting in a total of 36 fatalities. There were 24 nonfatal accidents. In terms of injury outcomes, there were 4 serious and 9 minor injuries, and 22 accidents in which no injuries were recorded. Fatal accidents were mainly due to loss of control by the pilot (44.4), in-flight structural failure of the airframe (25.9), and terrain impact (25.9). G-LOC was considered a possible cause in 11.1 of fatal accidents. Nonfatal accidents were mainly due to powerplant failure (41.7) and noncatastrophic airframe damage (25). Accidents involving aerobatic maneuvering have a significantly increased risk of a fatal outcome (odds ratio 26).DISCUSSION: The results of this study highlight the risks involved in aerobatic flight. Exceeding the operational limits of the maneuver and the design limits of the aircraft are major factors contributing to a fatal aerobatic aircraft accident. Improved awareness of G physiology and better operational decision-making while undertaking aerobatic flight may help prevent further accidents.Newman DG. Factors contributing to accidents during aerobatic flight operations. Aerosp Med Hum Perform. 2021; 92(8):612618.

PURPOSE: This study aimed to examine the effect of head-down tilt (HDT) on vascular autoregulation in different age groups and determine its effects on intraocular pressure (IOP) and central corneal thickness (CCT).METHODS: Included were 43 eyes of 23 men. The optic nerve head and parafoveal vascular densities were measured by optical coherence tomography angiography before and after 20 min 10 HDT. Also, the study comprised an examination of the IOP and CCT in a subset of 8 participants (14 eyes) in the sitting position and during 15 min of 10 HDT.RESULTS: Grid-based inside disc all-vessel density (GBID) was statistically significantly lower after the HDT test in subjects under 30 yr (1.26). Whole image and peripapillary capillary vessel density (WICVD, PCVD), and whole image and peripapillary all-vessel density (WIAVD, PAVD) were significantly higher after the HDT test in subjects ages 30-39 yr (1.34, 2.16, 1.05, 1.72, respectively). Inside disc capillary, all-vessel density (IDCVD, IDAVD) and GBID were significantly higher after HDT in subjects over 40 yr (2.48, 2.15, 1.52, respectively). In a subset of eight participants, IOP was significantly higher (3.7 mmHg) and CCT was unchanged after 15 min of HDT.CONCLUSION: Our study showed that simulated microgravity induced optic nerve head vessel density at the inside disc area, especially in persons over 40 years. In addition, IOP was increased by HDT, although no change in CCT was observed.Özelbaykal B, Öğretmenoğlu G, Tunçez I.H. Ocular outcomes in healthy subjects undergoing a short-term head-down tilt test. Aerosp Med Hum Perform. 2021; 92(8):619-626.

AbstractBACKGROUND: Based on posturography parameters during sleep deprivation (SD), a mental fatigue index (MFI) was constructed for healthy male cadets.METHODS: There were 37 young male subjects who volunteered for two successive days of SD. Their posturography balance, profile of mood status (POMS), and heart rate variability (HRV) were measured at four different times (10:00 and 22:00 of day 1, 10:00 and 22:00 of day 2). According to the methods used in our previous research, similar MFIs based on posturography parameters were computed. Then, correlations of MFIs with POMS scores and HRV values were evaluated by linear and nonlinear methods including quadratic, S-curve, growth, and exponential analyses.RESULTS: MFI continued to increase during SD and MFI as the independent variable had quadratic relationships with fluster (R² 0.057), depression (R² 0.067), and anger (R² 0.05) scores of POMS. A linear correlation was found between MFI and the depression score (R² 0.045) and MFI correlated linearly (R² 0.029) and nonlinearly (R² 0.03) with heart rate. Similarly, MFI reflected changes in the time and frequency domain parameters of HRV, with linear (R²range: 0.0290.082) or nonlinear (R²range: 0.0300.082) relationships.DISCUSSION: The increase of MFI was linked with amplification of personal negative moods and an imbalance of autonomic nervous system activity. The findings suggest that MFI might be a potential indicator of mental fatigue and provide a method to prevent driving fatigue and human errors.Cheng S, Yang J, Su M, Sun J, Xiong K, Ma J, Hu W. Postural stability change under sleep deprivation and mental fatigue status. Aerosp Med Hum Perform. 2021; 92(8):627632.

AbstractBACKGROUND: Members of the public will soon be taking commercial suborbital spaceflights with significant G_x (chest-to-back) acceleration potentially reaching up to 6 G_x. Pulmonary physiology is gravity-dependent and is likely to be affected, which may have clinical implications for medically susceptible individuals.METHODS: During 2-min centrifuge exposures ranging up to 6 G_x, 11 healthy subjects were studied using advanced respiratory techniques. These sustained exposures were intended to allow characterization of the underlying pulmonary response and did not replicate actual suborbital G profiles. Regional distribution of ventilation in the lungs was determined using electrical impedance tomography. Neural respiratory drive (from diaphragm electromyography) and work of breathing (from transdiaphragmatic pressures) were obtained via nasoesophageal catheters. Arterial blood gases were measured in a subset of subjects. Measurements were conducted while breathing air and breathing 15 oxygen to simulate anticipated cabin pressurization conditions.RESULTS: Acceleration caused hypoxemia that worsened with increasing magnitude and duration of G_x. Minimum arterial oxygen saturation at 6 G_x was 86 1 breathing air and 79 1 breathing 15 oxygen. With increasing G_x the alveolar-arterial (A-a) oxygen gradient widened progressively and the relative distribution of ventilation reversed from posterior to anterior lung regions with substantial gas-trapping anteriorly. Severe breathlessness accompanied large progressive increases in work of breathing and neural respiratory drive.DISCUSSION: Sustained high-G acceleration at magnitudes relevant to suborbital flight profoundly affects respiratory physiology. These effects may become clinically important in the most medically susceptible passengers, in whom the potential role of centrifuge-based preflight evaluation requires further investigation.Pollock RD, Jolley CJ, Abid N, Couper JH, Estrada-Petrocelli L, Hodkinson PD, Leonhardt S, Mago-Elliott S, Menden T, Rafferty G, Richmond G, Robbins PA, Ritchie GAD, Segal MJ, Stevenson AT, Tank HD, Smith TG. Pulmonary effects of sustained periods of high-G acceleration relevant to suborbital spaceflight. Aerosp Med Hum Perform. 2021; 92(7):633641.

INTRODUCTION: Syncope is both incapacitating and unpredictable, presenting a significant challenge in aircrew assessment. Previous UK Civil Aviation Authority (CAA) guidance lacked transparency and relied heavily on specialist in-house cardiology and neurology opinion. A new algorithm was developed which elaborated and formalized the decision-making process. An analysis of its impact on historic cases was undertaken to ensure it aligned with previous certificatory outcomes.METHODS: The medical literature on syncope and the approaches of other national aviation authorities were reviewed to help inform the development of a new algorithm. Using syncope cases in the CAA database, regulatory outcomes generated using the new algorithm were compared with previous decisions in terms of time off from flying (TOF) and Operational Multi-Crew Limitation (OML) duration.RESULTS: There were 40 historic syncope cases (25 existing certificate holders,15 initial applicants) which were reassessed using the new algorithm. The mean TOF for existing pilots using the new algorithm was 7.1 9.8 (mean SD) vs. 4.2 3.5 mo under the old guidance with an OML duration of 21.4 34.9 vs. 24.5 25.2 mo. One less initial applicant experienced a delay to certification. Four cases with underlying pathology were detected using old and new guidance.DISCUSSION: The reassessment of cases showed no statistically significant difference in TOF and OML duration; this is a positive finding from a regulatory perspective, enabling algorithm-led decision-making with less reliance on in-house expertise. A similar approach may be useful in future updates to other areas of regulatory practice.Anderton RA, Mitchell SJ, ONunain SS. Syncope in commercial pilots and new regulatory guidance. Aerosp Med Hum Perform. 2021; 92(8):642649.

AbstractINTRODUCTION: For over 50 yr, investigators have studied the physiological adaptations of the human system during short- and long-duration spaceflight exposures. Much of the knowledge gained in developing health countermeasures for astronauts onboard the International Space Station demonstrate terrestrial applications. To date, a systematic process for translating these space applications to terrestrial human health has yet to be defined.METHODS: In the summer of 2017, a team of 38 international scientists launched the Bellagio ll Summit Initiative. The goals of the Summit were: 1) To identify space medicine findings and countermeasures with highest probability for future terrestrial applications; and 2) To develop a roadmap for translation of these countermeasures to future terrestrial application. The team reviewed public domain literature, NASA databases, and evidence books within the framework of the five-stage National Institutes of Health (NIH) translation science model, and the NASA two-stage translation model. Teams then analyzed and discussed interdisciplinary findings to determine the most significant evidence-based countermeasures sufficiently developed for terrestrial application.RESULTS: Teams identified published human spaceflight research and applied translational science models to define mature products for terrestrial clinical practice.CONCLUSIONS: The Bellagio ll Summit identified a snapshot of space medicine research and mature science with the highest probability of translation and developed a Roadmap of terrestrial application from space medicine-derived countermeasures. These evidence-based findings can provide guidance regarding the terrestrial applications of best practices, countermeasures, and clinical protocols currently used in spaceflight.Sides MB, Johnston SL III, Sirek A, Lee PH, Blue RS, Antonsen EL, Basner M, Douglas GL, Epstein A, Flynn-Evans EE, Gallagher MB, Hayes J, Lee SMC, Lockley SW, Monseur B, Nelson NG, Sargsyan A, Smith SM, Stenger MB, Stepanek J, Zwart SR; Bellagio II Team. Bellagio II report: terrestrial applications of space medicine research. Aerosp Med Hum Perform. 2021; 92(8):650669.

INTRODUCTION: Ketamine is a rapidly acting general anesthetic which is globally used in surgical analgesia, as well as in the management of pain. It is also used as a recreational drug. Because of its widespread use in surgical settings, the use of this drug presents an aeromedical problemin addition, of course, to the underlying condition for which it has been used. The literature around the mechanisms and side effects of ketamine is reasonably mature, and it is possible to make fairly dependable risk management decisions about return to flying based on the information available. Accordingly, following ketamine use it is recommended that aviators be grounded for 48 h following Aviation Medical Examiner review. If review is unavailable, the aviator should be grounded for 1 wk to allow sufficient time to identify the existence of prolonged side effects, such as psychomimetic effects or cognitive changes.Boyd NL, Navathe PD. An update to aircrew grounding periods after ketamine use. Aerosp Med Hum Perform. 2021; 92(8):670-675.

INTRODUCTION: During active phases of manned spaceflight there is a possibility of a spacecraft landing at any point traversed by its orbital path on the Earth. Survival training after emergency landing is an important and vital part of pre-mission preparations. In this paper we analyze medical issues associated with winter survival training in marshy and forested terrain.METHODS: From 2011 to 2019, 50 International Space Station crews participated in winter survival training. Crewmembers included Roscosmos, NASA, CSA, ESA, and JAXA astronauts, spaceflight participants, and instructors. Medical protocols and training final reports were analyzed for conditions and medical events.RESULTS: The health status of crewmembers during training was nominal. Temperature sensation was reported as comfortable or moderately cold during daytime and moderately cold or cold during nighttime. S_pO₂ (blood oxygen saturation) and heart rate recorded during training did not exceed normal values. S_pCO (blood carbon monoxide saturation) generally was within normal limits. All participating crewmembers lost some bodyweight, from 0.15.5 kg (average 2.1 kg). Over the course of winter survival training there were 32 medical and environmental events requiring medical intervention. For two of the crewmembers requiring medical intervention, training was subsequently canceled.DISCUSSION: Winter survival training has successfully prepared spaceflight crews for the possibility of off-nominal landings in challenging terrain under adverse conditions. As this training involves high fidelity flight-like survival equipment and assigned flight crewmembers, the medical problems described here should closely reflect type and prevalence of events during an actual contingency scenario.Kireev KS, Grishin AP, Dowell GL. Medical issues associated with winter survival training. Aerosp Med Hum Perform. 2021; 92(8):676680.

BACKGROUND: The Aerospace Medicine Systematic Review Group was set up in 2016 to facilitate high quality and transparent synthesis of primary data to enable evidence-based practice. The group identified many research methods specific to space medicine that need consideration for systematic review methods. The group has developed space medicine specific methods to address this and trialed usage of these methods across seven published systematic reviews. This paper outlines evolution of space medicine synthesis methods and discussion of their initial application.METHODS: Space medicine systematic review guidance has been developed for protocol planning, quantitative and qualitative synthesis, sourcing gray data, and assessing quality and transferability of space medicine human spaceflight simulation study environments.RESULTS: Decision algorithms for guidance and tool usage were created based on usage. Six reviews used quantitative methods in which no meta-analyses were possible due to lack of controlled trials or reporting issues. All reviews scored the quality and transferability of space simulation environments. One review was qualitative. Several research gaps were identified.CONCLUSION: Successful use of the developed methods demonstrates usability and initial validity. The current space medicine evidence base resulting in no meta-analyses being possible shows the need for standardized guidance on how to synthesize data in this field. It also provides evidence to call for increasing use of controlled trials, standardizing outcome measures, and improving minimum reporting standards. Space medicine is a unique field of medical research that requires specific systematic review methods.Winnard A, Caplan N, Bruce-Martin C, Swain P, Velho R, Meroni R, Wotring V, Damann V, Weber T, Evetts S, Laws J. Developing, implementing, and applying novel techniques during systematic reviews of primary space medicine data. Aerosp Med Hum Perform. 2021; 92(8):681688.

INTRODUCTION: In 1991, Bechtel and Berning proposed that a decrement in morale and well-being affects people working in isolated and confined environments during the third quarter of their mission. Studies conducted during such conditions have suggested that whereas some people may experience such a phenomenon, it is not a typical occurrence in space or space simulation environments. Possible reasons for varying outcomes include demand characteristic bias, individual personality traits, training omissions, experimental methodological issues, and the impact of mission events on crewmember well-being. Research related to a future Mars expedition needs to investigate the impact of these factors.Kanas N, Gushin V, Yusupova A. Whither the third quarter phenomenon? Aerosp Med Hum Perform. 2021; 92(8):689691.