DIFFERENT HEART-RATE PATTERNS IN OBSTRUCTIVE APNEAS DURING NREM SLEEP

Both bradycardia and a trend to tachycardia have been reported in obst ructive sleep apneas (OSA). Because heart rate (HR) behavior may yield information on parasympathetic activity during OSA, we analyzed HR in samples of consecutive apneic cycles in non-rapid eye movement (NREM) sleep, recorded in normotensive patients breathing room air (n = 7) a nd supplemental O-2 (n = 4). In air, the patients showed different HR trends during apnea, as HR decreased (HR down arrow), remained constan t (HR=), or increased (HR up arrow). By multiple regression analysis, development of HR trends correlated with the HR fall in the late inter apneic period, HR at first effort, the decrease in esophageal pressure , and the lengthening of inspiration during apnea (R-2 = 0.42). O-2 ab olished HR down arrow-OSA, whereas HR= and HR up arrow-OSA still occur red but at higher HR than in air. In both the air and O-2 series, the HR fall preceding apnea correlated significantly with the degree of hy poxia reached in the previous apneic cycle. These data indicate a comp lex modulation of HR during OSA, with the HR fall in the late interapn eic period possibly reflecting the effectiveness of parasympathetic ca rdiac control in OSA patients during sleep.