Sleep stage influences the hemodynamic response to obstructive apneas.

Blood pressure (BP) rises at the termination of obstructive episodes in patients with sleep apnea. Although the relationship of these BP elevations to oxygen saturation (SaO2) and arousal has been explored, the influence of sleep stage is undefined. To examine the effects of sleep stage on the postapnea BP elevation, we enrolled 12 patients with obstructive sleep apnea (OSA), and successfully collected data from seven of these (all male). Subjects slept overnight in the sleep laboratory, 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 arterial pressure (MAP) at termination of apneas during NREM sleep associated with SaO2 nadirs 78 to 82% (NREM 80%) was compared with MAP following apneas in REM with the same SaO2 nadir (REM 80%), there was a significant 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 SaO2 nadirs of 78 to 82% with events with nadirs of < 75% (REM < 75%). In REM, further desaturation was associated with significant lengthening of the obstructive episodes and significantly higher postapnea BP increases (REM 75% 143 +/- 19.9 mm Hg, p = 0.0392). We conclude that sleep stage alters the hemodynamic response to obstructive apneas during sleep.