Changes of Upper Airway According to the Sleep Stage in Normal Subjects

Objectives：Sleep has five different periods manifested by changes in the EEG activity and certain behavioral correlates. It has been proposed that the upper airway mechanics would be influenced by sleep stage. Although several methods have been used to evaluate the regions over which the upper airway collapses during sleep, there were seldom reports about the changes of upper airway according to the sleep stage. The present study was conducted to determine the effect of sleep stage on the upper airway dynamics. Materials and Method：Using electron beam, we studied ten normal subjects who did not have any sleep-disordered breathing. Each patient being monitored with EEG was scanned while sleeping naturally. The images were acquired during light sleep, deep sleep and REM sleep during at least two full respiratory cycles. Results：Upper airway collapse was increased with the progression of sleep, but the level of stenosis was relatively constant throughout the sleep. Sleep stage had differential effects on the upper airway size depending on the investigated site. Conclusion：Our data suggest that upper airway mechanics are influenced by each sleep stage. This would indicate that the study of either point of sleep or either site of airway in isolation may not allow a proper insight on the overall upper airway pathophysiology. (Korean J Otolaryngol 2003;46:491-5)