Based on meta-analyses, the blood pressure (BP) lowering effect of continuous positive airway pressure (CPAP) therapy in patients with obstructive sleep apnea (OSA) is reported to be approximately 2-3mmHg. This figure is derived from heterogeneous trials, often limited by poor CPAP-adherence, and thus possibly underestimating the treatment effect. We analyzed morning BP data from three randomized controlled CPAP withdrawal trials which included only patients with optimal CPAP-compliance.
Within the three trials, 149 OSA patients on CPAP were randomized to continue therapeutic CPAP (n=65) or to withdraw CPAP (n=84) for two weeks. Morning BP was measured at home before, and after sleep studies in hospital.
CPAP-withdrawal was associated with a return of OSA (apnea-hypopnea index (AHI) at baseline 2.8/h, at follow-up 33.2/h). Systolic office BP increased in the CPAP-withdrawal group, compared to CPAP-continuation, by +5.4mmHg (95%CI 1.8-8.9mmHg, p=0.003), and systolic home BP by +9.0mmHg (95%-CI 5.7-12.3mmHg, p<0.001). Diastolic office BP increased by +5.0mmHg (95%CI 2.7-7.3mmHg, p<0.001), and diastolic home BP by +7.8mmHg (95%CI 5.6-10.4mmHg, p<0.001).AHI, baseline home systolic BP, statin usage, gender, and number of antihypertensive drugs were all independently associated with systolic BP change in multivariate analysis, controlling for age, BMI, smoking, diabetes, and sleepiness.
CPAP-withdrawal results in a clinically relevant increase in BP, which is considerably higher than in conventional CPAP trials, and is also underestimated when office BP is used. Greater OSA severity is associated with a higher BP rise in response to CPAP-withdrawal.