Spontaneous baroreflex analysis in non-apneic snoring individuals during NREM sleep.

The primary purpose of this study was to measure baroreceptor sensitivity (BS) during wakefulness and non-rapid eye movement (NREM) sleep in non-apneic snoring individuals. To achieve this purpose continuous and simultaneous measurements of snoring, oxygen saturation, sleep stages, arterial blood pressure and heart rate were obtained from seven non-apneic snoring subjects. After obtaining these measures, a computer program was employed to detect concomitant increases or decreases in systolic blood pressure and R-R interval duration during sequences of three or more consecutive beats that occurred during stage II and slow wave sleep (SWS). The values recorded from a given sequence were plotted and the slope of the regression line fit to the data was used as a measure of BS. The results showed that mean arterial pressure and heart rate during stage II and SWS of NREM sleep were not significantly different from wakefulness. In contrast, the BS measured during NREM sleep was significantly lower than values recorded during wakefulness. In addition, linear regression analysis showed that an inverse and significant correlation existed between snoring frequency and the decrease in BS during sleep. We conclude that the decrease in blood pressure and heart rate normally observed during NREM sleep in healthy non-snoring individuals is attenuated or abolished in non-apneic snoring individuals and that these cardiovascular alterations may be partially mediated by a decrease in BS.