Reduced cardiac sympathetic autonomic tone after long‐term nasal continuous positive airway pressure in obstructive sleep apnoea syndrome

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Abstract
The increased sympathetic activation that occurs in obstructive sleep apnoea (OSA) may play an important role in associated morbidity. We investigated the effect of long‐term (3 month) nasal continuous positive airway pressure (CPAP) on the autonomic nervous system assessed by heart rate variability (HRV). Fourteen patients (12 men), mean age 61·4 ± 8·1 years, with OSA underwent continuous synchronized electrocardiographic and polysomnographic monitoring. The apnoea/hypopnoea index (AHI) decreased from 50·6 ± 13·7 to 2·2 ± 2·5 events h−1 after CPAP. HRV analysis showed significant decreases in low frequency (LF; from 7·12 ± 1·06 to 6·22 ± 1·18 ln ms2 Hz−1; P2 Hz−1; P2 Hz−1; P2 Hz−1; P<0·001). Treatment of OSA by CPAP significantly reduced the parameters of cardiac sympathetic tone, a favourable effect.