Experimental elevations of blood pressure induced as an internal stimulus during sleep in man: effects on cortical vigilance and response thresholds in different sleep stages.

The hypothesis that raising blood pressure (BP) during human sleep, by intravenous administration of angiotensin II, causes arousals was tested. BP was measured intraarterially during polygraphic sleep recordings. Twenty-seven intrasleep elevations of BP in two young adults over 2 nights were evaluated. The BP increases ranged from 16% to 74% of the preexperimental level for systolic BP and from 28% to 84% for diastolic BP. Eighty-one percent of all BP variations induced arousals, and the number of awakenings during elevated BP was 6.5 times higher than in control conditions. These results confirm the hypothesis that BP elevation is an internal stimulus inducing arousal reactions from sleep. The arousals were equally linked to the three phases of BP variation, i.e., rise, peak, and fall in BP, indicating that BP variation functions as a stimulus unit. Arousal thresholds varied with the different sleep stages. They were lowest in sleep stage 2, slightly higher in REM sleep, and highest in slow-wave sleep, in accordance with the thresholds for neutral external stimuli. The study demonstrates the relevance of BP when considering the physiological parameters of sleep-wake regulation.