SLEEP STAGE INFLUENCES THE HEMODYNAMIC-RESPONSE TO OBSTRUCTIVE APNEAS

Blood pressure (BP) rises at the termination of obstructive episodes i n patients with sleep apnea. Although the relationship of these BP ele vations to oxygen saturation (Sa(O2)) and arousal has been explored, t he influence of sleep stage is undefined. To examine the effects of sl eep stage on the postapnea BP elevation, we enrolled 12 patients with obstructive sleep apnea (OSA), and successfully collected data from se ven of these (all male). Subjects slept overnight in the sleep laborat ory, with full sleep and respiratory monitoring. Arterial pressure was assessed continuously with a radial artery catheter (six patients) or with digital photoplethysmography (one patient). Apneas occurring in both rapid eye movement (REM) and non-rapid eye movement (NREM) sleep were matched for duration and degree of desaturation. When mean arteri al pressure (MAP) at termination of apneas during NREM sleep associate d with Sa(O2) nadirs 78 to 82% (NREM 80%) was compared with MAP follow ing apneas in REM with the same Sa(O2) nadir (REM 80%), there was a si gnificant difference (NREM 80% 122 +/- 15.3 mm Hg, REM 80% 132 +/- 11. 0; p = 0.0109). We also analyzed the effect of oxygen desaturation on MAP during REM sleep, by comparing events with Sa(O2) nadirs of 78 to 82% with events with nadirs of < 75% (REM < 75%). In REM, further desa turation was associated with significant lengthening of the obstructiv e episodes and significantly higher postapnea BP increases (REM 75% 14 3 +/- 19.9 mm Hg, p = 0.0392). We conclude that sleep stage alters the hemodynamic response to obstructive apneas during sleep.