Sleep at Simulated Aircraft Cabin Pressure and Its Effects on Performance
This study was funded by the Boeing Company and conducted with the University of Oklahoma, Tulsa in their hypobaric chamber, in collaboration with Washington State University Spokane. Polysomnography (EEG, EOG, EMG) was used to monitor the sleep of 20 men (30-56 y) at ground level and the equivalent of 8000 ft, in a blinded crossover study design. The surprising finding was that, although average oxygen saturation was much lower at 8000 ft than at ground level, there were no significant differences between the conditions in sleep quantity or quality, or in in post-sleep performance on a range of tests.
Physiologic Mechanisms and Significance of Mild Hypobaric Hypoxia on Oxygen Saturation During Sleep
This second hypobaric chamber study was also funded by the Boeing Company and was conducted to confirm and expand on the findings of the above study. It was conducted with the Aerospace Physiology Laboratory of Simon Fraser University in Vancouver. As well as monitoring sleep using polysomnography, overnight oximetry and respiratory monitoring were undertaken in 3 different conditions: at ground level, 6000 feet, and 8000 feet. Fourteen male participants aged 30-49 y completed the study.
In agreement with the previous study, there were marked changes to oxygenation during sleep but no discernable changes to total sleep time, sleep architecture or perception of sleep. However, there was greater sleep disruption at increasing altitude, as shown by an increase in both arousal and sleep stage transition indices. Increasing altitude was also associated with an increase in respiratory disturbances during sleep (increase in the Apnoea/Hypopnea Index) and initiated the onset of periodic breathing in most participants. There was considerable variability among participants in the periodic breathing response which deserves further investigation with a larger group of participants and more intensive respiratory monitoring.
