A randomized controlled trial on ambulatory blood pressure lowering effect of CPAP in patients with obstructive sleep apnea and nocturnal hypertension

Objective: In a randomised controlled trial, we investigated the blood pressure (BP) lowering effect of continuous positive airway pressure (CPAP) in patients with moderate-severe obstructive sleep apnoea syndrome (OSAS, an apnoea-hypopnoea index, AHI of 15 or higher) and nocturnal hypertension (night-time systolic/diastolic BP >= 120/70mmHg).Methods: Sixty patients were randomly assigned to CPAP or sham CPAP, while maintaining their antihypertensive treatment. Ambulatory BP monitoring was performed at baseline (first run-in visit) and the end of follow-up. Clinic and home BP were measured at baseline and each of the monthly follow-up visits.Results: Of the 60 patients, 47 completed the 3-month study. CPAP (n=26), compared with sham CPAP (n=21), slightly and non-significantly reduced 24-h systolic/diastolic BP by -2.8/-2.5mmHg (p >= 0.27), with a slightly greater between-group difference in the daytime (-4.0/-2.8mmHg, p >= 0.29) than night-time (-0.2/-1.5mmHg, p >= 0.50). The CPAP treatment did not significantly influence clinic or home BP during follow-up (p >= 0.27). Nonetheless, simple and partial correlation analyses showed that the ambulatory BP lowering effect was dependent on the daytime pulse rate at baseline (r >= 0.47, p <= 0.01). In patients with a daytime pulse rate greater than 85 beats/min, the mean changes in daytime systolic BP were significantly greater in the CPAP (n=10) than sham CPAP group (n=11), with a between-group mean difference of -10.1mmHg (p=0.048).Conclusions: The CPAP treatment did not show significant ambulatory BP lowering effect in patients with moderate-severe OSAS and nocturnal hypertension. However, it may be effective in lowering daytime BP in patients with a faster pulse rate.