Sleep and Oxygen Saturation under Flight Conditions in an Airplane Crew-Rest Compartment Mock-up

Abstract

Introduction: With increasing number and duration of long-haul flights crews’ on-board recovery is a topic of upmost importance. Preliminary evidence suggests a link between hypobaric conditions, sleep changes and oxygen desaturation. The objective of this study was to examine a potential causal relation between hypoxia and sleep disturbance under flight-level conditions. Methods: We investigated 12 healthy volunteers (6 females, mean age 26.2 years ± 5.1 SD) in 4 experimental conditions: 1) 4-h sleep opportunity in private bedrooms of the sleep laboratory, normobaric, no noise, 2) 4-h sleep opportunity in a crew-rest compartment mock-up (CRC), normobaric (ground level), inflight noise, 3) 4-h sleep opportunity in a CRC, hypobaric (8000ft flight level), inflight noise, and 4) 4-h recumbent wakefulness in a CRC, hypobaric (8000ft flight level), inflight noise. The CRC was implemented in a pressure chamber. Polysomnograms and blood oxygen saturation (SpO2) were recorded continuously and analyzed with mixed ANOVA, post-hoc t-tests. Results: In the flight simulation participants slept significantly less compared to ground level or to the sleep laboratory. Sleep onset latency (SOL) was increased (p=.0015) whereas sleep period time (SPT) (p=.0048) and total sleep time (TST) (p=.0010) were reduced. Waking after sleep onset tended to be increased (p=.0662). Sleeping at flight level reduced SpO2 in comparison to all other conditions (p<.0001). The mean SpO2 level during sleep inflight was 88% (± 0.5 SE) with a mean minimum of 80% (± 0.8 SE), whereas the mean SpO2 level during recumbent wakefulness inflight was 92% (± 0.3 SE). Participants spent 70% of SPT in a state of hypobaric hypoxia (<90% SpO2), 6% of SPT even below 85% SpO2. In contrast, during recumbent wakefulness under flight conditions participants spent only 13% of time below 90% SpO2 and 1% of time below 85% SpO2. Moreover, SpO2 during sleep was lower than during SOL (p<.001). Conclusion: Sleep under flight-level hypobaric conditions is impaired and – compared to wakefulness under the same conditions – associated with increased risk of oxygen desaturation. Sleeping on board of airplanes as a measure of recovery should therefore be regarded with caution.