BACKGROUND: Biomathematical modeling software like the Sleep, Activity, Fatigue, and Task Effectiveness (SAFTE) model and Fatigue Avoidance Scheduling Tool (FAST) help carriers predict fatigue risk for planned rosters. The ability of a biomathematical model to accurately estimate fatigue risk during unprecedented operations, such as COVID-19 humanitarian ultra-long-range flights, is unknown. Azul Cargo Express organized and conducted five separate humanitarian missions to China between May and July 2020. Prior to conducting the missions, a sleep-prediction algorithm (AutoSleep) within SAFTE-FAST was used to predict in-flight sleep duration and pilot effectiveness. Here we compare AutoSleep predictions against pilots’ sleep diary and a sleep-tracking actigraphy device (Zulu watch, Institutes for Behavior Resources) from Azul’s COVID-19 humanitarian missions.METHODS: Pilots wore Zulu watches throughout the mission period and reported sleep duration for their in-flight rest periods using a sleep diary. Agreement between AutoSleep, diary, and Zulu watch measures was compared using intraclass correlation coefficients (ICC). Goodness-of-fit between predicted effectiveness distribution between scenarios was evaluated using the R² statistic.RESULTS: A total of 20 (N = 20) pilots flying across 5 humanitarian missions provided sleep diary and actigraphy data. ICC and R² values were >0.90, indicating excellent agreement between sleep measures and predicted effectiveness distribution, respectively.DISCUSSION: Biomathematical predictions of in-flight sleep during unprecedented humanitarian missions were in agreement with actual sleep patterns during flights. These findings indicate that biomathematical models may retain accuracy even under extreme circumstances. Pilots may overestimate the amount of sleep that they receive during extreme flight-duty periods, which could constitute a fatigue risk.Devine JK, Garcia CR, Simoes AS, Guelere MR, de Godoy B, Silva DS, Pacheco PC, Choynowski J, Hursh SR. Predictive biomathematical modeling compared to objective sleep during COVID-19 humanitarian flights. Aerosp Med Hum Perform. 2022; 93(1):4–12.

INTRODUCTION: Repeated ischemic preconditioning (IPC) can improve muscle and pulmonary oxygen on-kinetics, blood flow, and exercise efficiency, but these effects have not been investigated in severe hypoxia. The aim of the current study was to evaluate the effects of 7 d of IPC on resting and exercising muscle and cardio-pulmonary responses to severe hypoxia.METHODS: A total of 14 subjects received either: 1) 7 d of repeated lower-limb occlusion (4 × 5 min, 217 ± 30 mmHg) at limb occlusive pressure (IPC) or SHAM (4 × 5 min, 20 mmHg). Subjects were tested for resting limb blood flow, relative microvascular deoxyhemoglobin concentration ([HHB]), and pulmonary oxygen (Vo_2p) responses to steady state and incremental exercise to exhaustion in hypoxia (fractional inspired O₂ = 0.103), which was followed by 7 d of IPC or SHAM and retesting 72 h post-intervention.RESULTS: There were no effects of IPC on maximal oxygen consumption, time to exhaustion during the incremental test, or minute ventilation and arterial oxygen saturation. However, the IPC group had higher delta efficiency based on pooled results and lower steady state Δ[HHB] (IPC ∼24% vs. SHAM ∼6% pre to post), as well as slowing the [HHB] time constant (IPC ∼26% vs. SHAM ∼3% pre to post) and reducing the overshoot in [HHB]: Vo₂ ratio during exercise onset.CONCLUSIONS: Collectively, these results demonstrate that muscle O₂ efficiency and microvascular O₂ distribution can be improved by repeated IPC, but there are no effects on maximal exercise capacity in severe hypoxia.Chopra K, Jeffries O, Tallent J, Heffernan S, Kilduff L, Gray A, Waldron M. Repeated ischemic preconditioning effects on physiological responses to hypoxic exercise. Aerosp Med Hum Perform. 2022; 93(1):13–21.

BACKGROUND: In the aviation world, hyperuricemia can endanger flight safety through the risk of incapacitation, either associated with gout disease or associated with an increased risk of cardiovascular disease. This study aims to determine the prevalence of hyperuricemia in civil pilots in Indonesia and the identification of risk factors for hyperuricemia in civil pilots in Indonesia.METHODS: The study used a cross-sectional method from the medical records of civil pilots at the Aviation Medical Center, Jakarta, who were examined on 1 November 2019 through 30 April 2020. Data collected from medical records included: laboratory data of uric acid, age, total flight hours, Body Mass Index (BMI), and alcohol consumption. Hyperuricemia is a plasma urate concentration > 420 µmol · L⁻¹(7 mg · dl⁻¹).RESULTS: The research sample amounted to 5202 pilots; 18.4% had hyperuricemia. Pilots who have total flight hours ≥5000 have a reduced risk of hyperuricemia by 24% compared to pilots with total flight hours <5000. Obese and overweight pilots had a 2.98 times and 1.36 times, respectively, greater risk of hyperuricemia than pilots who had a normal BMI. Based on BMI criteria classification of WHO Asia Pacific, obese is ≥25 and overweight is 23–24.9. Furthermore, compared to pilots who did not consume alcohol, pilots who consumed alcohol had a 14.68 times greater risk of developing hyperuricemia.CONCLUSION: The prevalence of hyperuricemia in civil pilots in Indonesia is 18.4%. Obesity, overweight, and alcohol consumption increase the risk of hyperuricemia in civil pilots in Indonesia.Tisera SC, Agustina A, Soemarko DS. Total flight hours and other factors associated with hyperuricemia in civilian pilots. Aerosp Med Hum Perform. 2022; 93(1):22–25.

BACKGROUND: Migraine is a common disorder with significant aeromedical implications. The variability and unpredictable nature of occurrences hampers accurate assessment of future risk. This uncertainty results in a necessarily conservative approach to aeromedical recommendations, which unfortunately may lead to over-restrictive dispositions. Limited long-term follow up information is available on migraine outcomes in pilots, particularly assessing for impact of potential modifiable aggravating factors.Methods: This retrospective study reviewed 159 U.S. Air Force pilots with migraine who had been granted aeromedical waivers. As a comparison group, 44 U.S. Air Force flight surgeons with migraine who had been granted aeromedical waivers were reviewed.Results: Migraine with aura and isolated migraine aura without headache accounted for the majority of migraine subtypes in both male and female subjects. Self-identified triggering factors were identified by 62% of subjects. The most commonly reported triggers were dietary factors, sleep disturbances, stress, caffeine intake, and hormonal factors. Sleep disturbances, stress, hormonal factors, and ethanol triggers were more frequently noted in female subjects. Self-reported positive response to trigger factor modification was noted in 54% of subjects. Subjects reported an average of only 3 migraine attacks in the previous year. Long-term follow up indicated continued aeromedical waiver in 91% of subjects.Discussion: The majority of subjects had migraine with aura or isolated migraine aura. Significant salutary response to modification of commonly-reported triggering factors was noted. These findings can be incorporated into individualized aeromedically-compatible management strategies to clarify symptom impact on aviation safety, improve symptom control, and increase the possibility of safe return to fly recommendations.Hesselbrock RR, Haynes JT. Migraine history and outcomes in military pilots and flight surgeons. Aerosp Med Hum Perform. 2022; 93(1):26-31.

INTRODUCTION: During spaceflight missions, astronauts work in an extreme environment with several hazards to physical health and performance. Exposure to microgravity results in remarkable deconditioning of several physiological systems, leading to impaired physical condition and human performance, posing a major risk to overall mission success and crew safety. Physical exercise is the cornerstone of strategies to mitigate physical deconditioning during spaceflight. Decades of research have enabled development of more optimal exercise strategies and equipment onboard the International Space Station. However, the effects of microgravity cannot be completely ameliorated with current exercise countermeasures. Moreover, future spaceflight missions deeper into space require a new generation of spacecraft, which will place yet more constraints on the use of exercise by limiting the amount, size, and weight of exercise equipment and the time available for exercise. Space agencies are exploring ways to optimize exercise countermeasures for spaceflight, specifically exercise strategies that are more efficient, require less equipment, and are less time-consuming. Blood flow restriction exercise is a low intensity exercise strategy that requires minimal equipment and can elicit positive training benefits across multiple physiological systems. This method of exercise training has potential as a strategy to optimize exercise countermeasures during spaceflight and reconditioning in terrestrial and partial gravity environments. The possible applications of blood flow restriction exercise during spaceflight are discussed herein.Hughes L, Hackney KJ, Patterson SD. Optimization of exercise countermeasures to spaceflight using blood flow restriction. Aerosp Med Hum Perform. 2021; 93(1):32–45.

INTRODUCTION: Hypobaric decompression sickness remains a problem during high-altitude aviation. The prevalence of venous gas emboli (VGE) serves as a marker of decompression stress and has been used as a method in evaluating the safety/risk associated with aviation profiles and/or gas mixtures. However, information is lacking concerning the variability of VGE formation when exposed to the same hypobaric profile on different occasions. In this paper, intra-individual test-retest variation regarding bubble formation during repeated hypobaric exposures is presented. The data can be used to determine the sample size needed for statistical power.METHOD: A total of 19 male, nonsmoking subjects volunteered for altitude exposures to 24,000 ft (7315 m). VGE was measured using ultrasound scanning and scored according to the Eftedal-Brubakk (EB) scale. Intraindividual test-retest variation in bubble formation (maximum VGE) was evaluated in subjects exposed more than once to hypobaric pressure. The statistical reliability was examined between paired exposures using the Intraclass Correlation test. G*Power version 3.1.9.6 was used for power calculations.RESULTS: During repeated 20–30 and 70-min exposures to 24,000 ft, 42% (N = 19, CI 23–67%) and 29% (N = 7, CI 5–70%) of the subjects varied between maximum EB scores < 3 and ≥ 3. The sample size needed to properly reject statistical significance of 1 EB step nominal difference between two paired exposures varied between 29–51 subjects.CONCLUSION: The large intraindividual test-retest variations in bubble grades during repeated hypobaric exposures highlight the need for relatively large numbers of subjects to reach statistical power when there are no or small differences in decompression stress between the exposures.Ånell R, Grönkvist M, Eiken O, Elia A, Gennser M. Intra-individual test-retest variation regarding venous gas bubble formation during high altitude exposures. Aerosp Med Hum Perform. 2022; 93(1):46–49.

OBJECTIVES: Airline cabin crew experience high levels of fatigue and sleepiness. Whether these are solely related to their work schedules/jetlag or are in part related to individual factors is unknown. The COVID-19 pandemic has significantly disrupted the aviation industry and many cabin crew have been grounded. This provides a unique opportunity to assess the causes of fatigue and sleepiness in this population.METHODS: An online anonymous survey was distributed in April–June 2020 to cabin crew who were 1) flying, 2) grounded but doing alternative work, and 3) grounded, not working, or unemployed. The survey measured fatigue, sleepiness, and mental health. It also screened their risk for insomnia, depression, and shift work disorder and assessed drug and caffeine use.RESULTS: Collected were 409 valid responses: 45 currently flying; 35 grounded but doing alternate work; and 329 not working. On average, all three groups experienced normal levels of fatigue and sleepiness. The risk for major depressive disorder was 27.4%, with 59.5% of individuals reporting abnormal levels of anxiety. Caffeine intake and the use of drugs and alcohol to facilitate sleep were common, although not different between those currently flying vs. grounded.CONCLUSIONS: With reduced workloads or not flying, cabin crew reported lowered fatigue and sleepiness compared to prepandemic findings, along with reduced risk for major depressive disorder. However, a high occurrence of negative emotional states were reported, potentially related to the uncertainty surrounding the pandemic. This study suggests fatigue and sleepiness is primarily related to airline operational rather than personal variables.Wen CC-Y, Nicholas CL, Howard ME, Trinder J, Jordan AS. Understanding sleepiness and fatigue in cabin crew using COVID-19 to dissociate causative factors. Aerosp Med Hum Perform. 2022; 93(1):50–53.

INTRODUCTION: This study aimed to evaluate whether a short familiarization session is sufficient for individuals with no prior experience of sonography to both reliably and consistently evaluate the prevalence of venous gas emboli (VGE) from precordial ultrasonic videos.METHODS: A total of 10 adults with no prior experience of sonography were introduced to the Eftedal-Brubakk 6-grade scale and were shown 6 video sequences, each of a maximum of 10 heartbeats, representing each grading level. Thereafter, they independently evaluated the prevalence of VGE in 70 ultrasonic videos before and after a 14-d interval (test-retest; intra-rater), with these being compared to an experienced sonographer’s grading (inter-rater).RESULTS: A significant inter-rater level of agreement was found between the naïve and experienced sonographers’ bubble grading both during the first (W = 0.945) and second (W = 0.952) round of bubble evaluation. The naïve observers’ evaluations were on average 79% (range: 61–95%) and 75% (range: 48–95%) in complete agreement with the experienced sonographer’s gradings, while the level of agreement was 99% and 98% within 1 grade unit. There was a significant intra-rater level of agreement (κ = 0.845) during the test-retest series, with a mean percentage level of agreement of 87% (range: 72–93%).CONCLUSION: This study demonstrates that a short familiarization session enables individuals with no prior sonography experience to consistently evaluate VGE prevalence from precordial ultrasonic videos.Elia A, Ånell R, Eiken O, Grönkvist M, Gennser M. Inter- and intra-rater level of agreement in ultrasonic video grading of venous gas emboli. Aerosp Med Hum Perform. 2022; 93(1):54–57.