Dynamics of Heart Rate Control in Obstructive Sleep Apnea

Abstract

Recent studies indicate that cardiovascular regulation is impaired and sympathetic activity is abnormally elevated in patients with obstructive sleep apnea (OSA) during both wakefulness and sleep^1,2. Heart rate variability (HRV) has been found to be substantially reduced in OSA³. Spectral analysis shows an increase in the proportion of low-frequency (0.04 to 0.15 Hz) content relative to high-frequency (0.15 to 0.4 Hz) content of heart rate oscillations in awake OSA subjects, suggesting increased sympathetic modulation along with decreased vagal cardiac activity. Although statistical and spectral analyses of HRV offer a simple and non-intrusive means of assessing cardiovascular autonomic function in these subjects, the measures derived can be confounded significantly by intra-and inter-subject differences in ventilation level and breathing pattern^4,5. To circumvent this limitation, we have introduced a minimal modeling approach that allows a clear delineation of the respiratory-related influences on HRV from the effects that are intrinsically circulatory in nature.