Nature and Science of Sleep (Feb 2022)
Sleep-Induced Hypoxia under Flight Conditions: Implications and Countermeasures for Long-Haul Flight Crews and Passengers
Abstract
Eva-Maria Elmenhorst,1,2 Daniel Rooney,1 Sibylle Benderoth,1 Martin Wittkowski,1 Juergen Wenzel,1 Daniel Aeschbach1,3,4 1Department of Sleep and Human Factors Research, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, 51170, Germany; 2Institute for Occupational and Social Medicine, Medical Faculty, RWTH Aachen University, Aachen, 52074, Germany; 3Institute of Experimental Epileptology and Cognition Research, University of Bonn Medical Center, Bonn, 53127, Germany; 4Division of Sleep Medicine, Harvard Medical School, Boston, MA, 02115, USACorrespondence: Eva-Maria Elmenhorst, Department of Sleep and Human Factors Research, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, 51170, Germany, Tel +49 2213 601 4735, Fax +49 2213 68323, Email [email protected]: 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.Keywords: polysomnography, oxygen saturation, EEG sleep power spectra, altitude, air travel, oxygen enrichment
