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

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Roche CHU Nord – Niveau 6, F-42055 Saint-Etienne Cedex 2, France

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; P<0·001), high frequency (HF; from 5·91 ± 0·87 to 5·62 ± 0·92 ln ms2 Hz−1; P<0·05) and LF/HF (from 1·21 ± 0·12 to 1·11 ± 0·15 ln ms2 Hz−1; P<0·001) when the patients were asleep. The decrease in LF/HF was prolonged into the daytime (from 1·33 ± 0·22 to 1·24 ± 0·21 ln ms2 Hz−1; P<0·001). Treatment of OSA by CPAP significantly reduced the parameters of cardiac sympathetic tone, a favourable effect.

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