Recovery in airplanes: sleep, and oxygen saturation

Abstract

Introduction: With increasing number and duration of long-haul flights the topic of crews’ on-board sleep and recovery gets progressively more important. At travelling altitude sleep takes place under hypobaric conditions corresponding to an altitude of 8000 ft. Methods: We investigated 24 healthy subjects (12 female, average age 27 years ± 4 SD) sleeping in a pressure chamber furnished as crew-rest-compartment. The flight simulation was realistic concerning the atmospheric conditions, the in-flight noise, and the 4h time in bed. Sleep-EEG, blood oxygen saturation (SpO2), and subjective sleep quality were recorded. Results were compared to a control group of 23 healthy subjects (9 female, average age 26 years ± 6 SD) that spent 4h time in bed in private rooms of the DLR-sleep laboratory under normobaric, silent conditions. Results: The recuperative value of sleep (to date subgroup of n=16) was reduced in hypobaric conditions since deep sleep (p<0.05) and REM sleep (p<0.01) were reduced whereas the light sleep phases (N1 p<0.05, N2 p<0.01) were increased. Sleep period time (SPT) and sleep efficiency did not differ between groups. The objective measures were emphasized by the subjective ratings (calmness of sleep: p<0.001; sleep depth: p<0.05). “In-flight”, subjects spent 83% (± 5%) of SPT in a state of hypobaric hypoxia (<90% SpO2), 4% of SPT even below 85% SpO2. The mean SpO2 level in-flight was 88% (± 1 SD) with a mean minimum of 81% (± 3 SD) while the control group had a mean SpO2 level of 96% (± 1 SD) (p<0.0001). Conclusion: Hypobaric hypoxia reduced the recuperative value of sleep. Young and healthy subjects were clearly affected. Older flight crews or diseased passengers might suffer from stronger effects while sleeping on board.