Background Millions of individuals with obstructive sleep apnoea (OSA) are treated by CPAP aimed at reducing blood pressure (BP) and thus cardiovascular risk. However, evidence is scarce concerning the impact of different CPAP modalities on BP evolution. Methods This double-blind, randomised clinical trial of parallel groups of patients with OSA indicated for CPAP treatment compared the efficacy of fixed-pressure CPAP (FP-CPAP) with auto-adjusting CPAP (AutoCPAP) in reducing BP. The primary endpoint was the change in office systolic BP after 4 months. Secondary endpoints included 24 h BP measurements. Results Patients (322) were randomised to FP-CPAP (n=161) or AutoCPAP (n=161). The mean apnoea+hypopnoea index (AHI) was 43/h (SD, 21); mean age was 57 (SD, 11), with 70% of males; mean body mass index was 31.3 kg/m 2 (SD, 6.6) and median device use was 5.1 h/night. In the intention-to-treat analysis, office systolic blood pressure decreased by 2.2 mm Hg (95% CI −5.8 to 1.4) and 0.4 mm Hg (−4.3 to 3.4) in the FP-CPAP and AutoCPAP group, respectively (group difference: −1.3 mm Hg (95% CI −4.1 to 1.5); p=0.37, adjusted for baseline BP values). 24 h diastolic BP (DBP) decreased by 1.7 mm Hg (95% CI −3.9 to 0.5) and 0.5 mm Hg (95% CI −2.3 to 1.3) in the FP-CPAP and AutoCPAP group, respectively (group difference: −1.4 mm Hg (95% CI −2.7 to −0.01); p=0.048, adjusted for baseline BP values). Conclusions The result was negative regarding the primary outcome of office BP, while FP-CPAP was more effective in reducing 24 h DBP (a secondary outcome). Trial registration number NCT01090297.
