Sleep-Induced Hypoxia under Flight Conditions: Implications and Countermeasures for Long-Haul Flight Crews and Passengers

Abstract

Purpose Recuperation during sleep on board of commercial long-haul flights is a safety issue of utmost importance for flight crews working extended duty periods. We intended to explore how sleep and blood oxygenation (in wake versus sleep) are affected by the conditions in an airliner at cruising altitude. Methods Healthy participants’ sleep was compared between 4-h sleep opportunities in the sleep laboratory (n = 23; sleep lab, ie, 53 m above sea level) and in an altitude chamber (n = 20; flight level, ie, 753 hPa, corresponding to 2438 m above sea level). A subgroup of 12 participants underwent three additional conditions in the altitude chamber: 1) 4-h sleep at ground level, 2) 4-h sleep at flight level with oxygen partial pressure equivalent to ground level, 3) 4-h monitored wakefulness at flight level. Sleep structure and blood oxygenation were analysed with mixed ANOVAs. Results Total sleep time at flight level compared to in the sleep laboratory was shorter (Δ mean ± standard error −11.1 ± 4.2 min) and included less N3 sleep (Δ −17.6 ± 5.4 min), while blood oxygenation was decreased. Participants spent 69.7% (± 8.3%) of the sleep period time but only 13.2% (± 3.0%) of monitored wakefulness in a hypoxic state (<90% oxygen saturation). Oxygen enrichment of the chamber prevented oxygen desaturation. Conclusion Sleep – but not wakefulness – under flight conditions induces hypobaric hypoxia which may contribute to impaired sleep. The results caution against the assumption of equivalent crew recovery in-flight and on the ground but hold promise for oxygen enrichment as a countermeasure. The present results have implications for flight safety and possible long-term consequences for health in crews.

A genetic variation in the adenosine A2A receptor gene contributes to variability in oscillatory alpha power in wake and sleep EEG and A1adenosine receptor availability in the human brain

“…Based on the polysomnographic recordings, sleep stages were scored in 30 s epochs according to the criteria of the American Academy of Sleep Medicine (Berry et al, 2017). After manually removing epochs with movement-artifacts, power spectra were computed with an FFT routine using a 4-s Hanning window and averaging ten overlapping epochs into 30-s epochs that matched the sleep scores (Elmenhorst et al, 2022). Power values were averaged across all epochs of each sleep stage, with non-rapid eye movement (NREM) stage comprising all N2 and N3 scored epochs.…”

Recent Progress in Long-Term Sleep Monitoring Technology

“…In 2014, the patterns of brain tissue oxygen content changes in adults and adolescents during different sleep stages were revealed by NIRS [ 222 ]. In 2022, Elmenhorst et al used blood oxygen sensors to analyze the sleep quality of long-haul flight crews at high altitudes and investigated the effect of a hypoxic environment on sleep at high altitudes, which has important implications for civil aviation safety [ 223 , 224 , 225 , 226 ].…”

Association between Hypoxia, Sleep, and the Circadian System during Long-Haul Flights. A Commentary [Letter]

“…We would like to comment on the paper by Elmenhorst et al 1 regarding the quality of a short nocturnal sleep episode in double aircrews on commercial ultra-long-haul flights.…”