Predominant endothelial vasomotor activity during human sleep: a near-infrared spectroscopy study.

Vasomotion is important in the study of vascular disorders, including stroke. Spontaneous low and very low hemodynamic oscillations (3-150 mHz) measured with near-infrared spectroscopy (NIRS) reflect the endothelial (3-20 mHz), neurogenic (20-40 mHz) and myogenic (40-150 mHz) components of vasomotion. We investigated sleep-specific patterns of vasomotion by characterizing hemodynamic oscillations with NIRS in healthy subjects, and tested the feasibility of NIRS as a bedside tool for monitoring vasomotion during whole-night sleep. To characterize local cerebral vasomotion, we compared cerebral NIRS measurements with muscular NIRS measurements and peripheral arterial oxygen saturation (SpO2 ) during different sleep stages in 14 healthy volunteers. Spectral powers of hemodynamic oscillations in the frequency range of endothelial vasomotion were systemically predominant in every sleep stage, and the powers of endothelial and neurogenic vasomotion decreased in deep sleep as compared with light sleep and rapid eye movement (REM) sleep in brain, muscle, and SpO2 . The decrease in the powers of myogenic vasomotion in deep sleep only occurred in brain, and not in muscle. These results point to a predominant role of endothelial function in regulating vasomotion during sleep. The decline in cerebral endothelial and neurogenic vasomotion during progression to deeper non-REM sleep suggests that deep sleep may play a protective role for vascular function. NIRS can be used to monitor endothelial control of vasomotion during nocturnal sleep, thus providing a promising non-invasive bedside tool with which to study the sleep-relevant pathological mechanisms in vascular diseases and stroke.