Effect of nCPAP therapy on heart rate in patients with obstructive sleep apnoea-hypopnoea.

Background: Elevated heart rate (HR) is a risk factor for cardiovascular disease. The effects of obstructive sleep apnoea-hypopnoea syndrome (OSAHS) on HR are controversial.

Aim: To investigate the effect of nasal continuous positive airway pressure (nCPAP) therapy on HR in OSAHS patients.

Methods: Sixty-two OSAHS patients underwent 24-h electrocardiographic recording, both before and 3 or 4 days after instigation of nCPAP.

Results: After nCPAP was started, HR significantly decreased (mean +/- SD 71.8 +/- 10.6 vs. 67.5 +/- 9.4 bpm, p < 0.0001), both in the daytime (0600-2200 h, 76.3 +/- 12.2 vs. 72.2 +/- 10.2 bpm, p < 0.0001) and at night-time (2200-0600 h, 64.5 +/- 9.1 vs. 60.0 +/- 8.9 bpm, p < 0.0001). HR was significantly reduced in both periods in the 44 patients with hypertension and/or diabetes mellitus, but only during the night-time in the 18 with neither condition. Before nCPAP treatment, HR was positively correlated with percentage time of arterial O2 saturation <90% during sleep (p = 0.008) and with the apnoea-hypopnoea index during sleep (p = 0.003). In 15 patients undergoing HR for 2 days before starting nCPAP, the mean HRs for the two periods were similar (p = 0.95).

Discussion: nCPAP therapy appears to decrease HR in OSAHS patients, and may thereby reduce their risk of cardiovascular disease.