In this four-site, randomized, parallel-group clinical trial, adult patients with significant cardiac risk factors or disease were screened for obstructive sleep apnea (OSA) using the Berlin questionnaire. Following home sleep testing, patients with significant OSA (AHI 15-50events/hour) were randomized to: healthy lifestyle and sleep education (HLSE) alone (control), CPAP with HLSE (Auto-CPAP), or supplemental oxygen with HLSE (2 L/min via nasal prongs). The primary outcome was 24-hour mean arterial pressure.
Of 318 patients who underwent randomization, 281 (88%) were evaluated for ambulatory blood pressure at both baseline and follow-up. Patients randomized to both the CPAP and supplemental oxygen groups had similar reductions in nocturnal hypoxemia. The adjusted 24-hour mean arterial pressure at 12 weeks was significantly lower in the CPAP group than in either the control group (−2.4mmHg; P=0.04) or the supplemental oxygen group (−2.8mmHg; P=0.02).
Comments. In patients with cardiovascular disease or multiple cardiovascular risk factors, the treatment of OSA with Auto-CPAP with HLSE resulted in a significant reduction in blood pressure compared to supplemental oxygen with HLSE or HLSE alone. Despite similar effects on nocturnal hypoxemia, the lack of a beneficial effect of supplemental oxygen suggests that factors such as frequent arousals, hypercapnia, and variation in intrathoracic pressure may play a role in hypertension resulting from OSA. Future pragmatic studies are indicated mechanistic influences of supplemental oxygen (such as high vs. low loop gain or dose-response relationship), and prevention of long-term cardiovascular events.