THE EFFECT OF RAPID EYE-MOVEMENT (REM) SLEEP ON UPPER AIRWAY MECHANICS IN NORMAL HUMAN-SUBJECTS

1. It has been proposed that the upper airway is more compliant during rapid eye movement (REM) sleep than during non-rapid eye movement (NR EM) sleep. The purpose of this study was to test this hypothesis in a group of subjects without sleep-disordered breathing. 2. On the first night, the effect of sleep stage on the relationship of retropalatal c ross-sectional area (CSA; visualized with a fibre-optic scope) to phar yngeal pressure (P-PH) measured at the soft palate during eupnoeic bre athing was studied. Breaths during REM sleep were divided into phasic (associated with eye movements) and tonic (not associated with eye mov ements). There was a significant decrease in pharyngeal CSA during NRE M sleep compared with wakefulness. There was no further decrease obser ved during either tonic or phasic REM sleep. Pharyngeal compliance, de fined as the slope of the regression CSA versus P-PH, was significantl y increased during NREM sleep compared with wakefulness and REM sleep, with the compliance during both tonic and phasic REM sleep being simi lar to that observed in wakefulness. 3. On the second night, the effec t of sleep stage on pressure-flow relationships of the upper air-way w as investigated. There was a trend towards the upper air-way resistanc e being highest in NREM sleep compared with wakefulness and REM sleep. 4. We conclude that the upper airway is stiffer and less compliant du ring REM sleep than during NREM sleep. We postulate that this differen ce is secondary to differences in upper airway vascular perfusion betw een REM and NREM sleep.