Different heart rate patterns in obstructive apneas during NREM sleep

Both bradycardia and a trend to tachycardia have been reported in obstructive 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) and supplemental 0, (n = 4), In air, the patients showed different HR trends
during apnea, as HR decreased (HR.!), remained constant (HR=), or increased (HRi), By multiple regression
analysis, development of HR trends correlated with the HR fall in the late interapneic period, HR at first effort, the
decrease in esophageal pressure, and the lengthening of inspiration during apnea (R' = 0,42). O2 abolished HRJ,OSA,
whereas HR= and HRt-OSA still occurred but at higher HR than in air. In both the air and O2 series, the
HR fall preceding apnea correlated significantly with the degree of hypoxia reached in the previous apneic cycle.
These data indicate a complex modulation of HR during OSA, with the HR fall in the late interapneic period
possibly reflecting the effectiveness of parasympathetic cardiac control in OSA patients during sleep.