title: Changes in diaphragmatic EMG activity during sleep in space.
abstract: It remains unknown how increased upper airway resistance (UAR) during sleep could be a function of gravity. We therefore conducted quantitative evaluation of the gravitational influence on diaphragmatic EMG activity (EMGdi) in an astronaut to estimate the effect of UAR in space. EMGdi was recorded by paired surface electrodes on the ground (control, C) and abroad a short-term space mission (space, S) for 30 consecutive h. Mean EMGdi recorded during quiet breathing in wakefulness was assigned the value of 100. EMGdi in C was significantly enhanced in all sleep stages compared with that while awake in the supine position (mean +/- SD, 230 +/- 23.2% in non-rapid eye movement (non-REM) Stage II, 233 +/- 13.8 in slow-wave sleep, and 233 +/- 40.0 in REM sleep versus 100 +/- 17.3 in wakefulness, p < 0.001). In contrast, there was no statistical difference in EMGdi in S between awake and any non-REM sleep stage (mean +/- SD, 100 +/- 20.5% in wakefulness versus 103 +/- 16.9 in non-REM Stage II and 100 +/- 14.8 in slow-wave sleep; NS). However, EMGdi in REM sleep in S was statistically greater (132 +/- 28.3%) than that during wakefulness or any other sleep stage in space (p < 0.001). Therefore, gravity may play a much more significant role in the normal healthy human in the increased upper airway resistance during sleep than the relative atonia of the upper airway muscles.
authors.affiliation: Second Department of Internal Medicine, School of Medicine, Tokai University, Kanagawa, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Takasaki
authors.forename: K
authors.initials: K
authors.lastname: Kamio
authors.forename: M
authors.initials: M
authors.lastname: Okamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Ohta
authors.forename: H
authors.initials: H
authors.lastname: Yamabayashi
mesh_terms: D000704:Analysis of Variance; D003964:Diaphragm / Q000502:physiology*; D004576:Electromyography / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D017286:Polysomnography / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D012016:Reference Values; D012890:Sleep / Q000502:physiology*; D013026:Space Flight; D014586:USSR