The effect of CPAP withdrawal on blood pressure in OSA: Data from three randomised-controlled trials

Background Based on meta-analyses, the blood pressure (BP) lowering effect of continuous positive airway pressure (CPAP) in obstructive sleep apnoea (OSA) is reported to be 2mmHg. This figure is derived from trials often limited by poor CPAP compliance, thus, underestimating the effect of CPAP treatment. We analysed BP data from randomised-controlled CPAP withdrawal trials which included only optimally CPAP compliant patients. Methods 145 OSA patients on CPAP were randomised to continue therapeutic (n=62) or to withdraw CPAP (n=83) for two weeks. Morning BP was measured at home before and in hospital after sleep studies. Results CPAP withdrawal was associated with a return of OSA (apnoea-hypopnoea 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 +6.5mmHg (95%CI 2.6-10.4mmHg, p=0.001) and systolic home BP by +9.7mmHg (95%-CI 6.3-13.0mmHg, p<0.001); diastolic office BP increased by +5.0mmHg (95%CI 2.4-7.6mmHg, p<0.001) and diastolic home BP by +7.9mmHg (95%CI 5.6-10.3mmHg, p<0.001). AHI, baseline systolic BP, statins, gender and number of antihypertensive drugs were independently associated with systolic BP change in multivariate analysis controlled for age, BMI, smoking, diabetes, and sleepiness. Change in diastolic BP was independently predicted by AHI, baseline diastolic BP, and statins. Conclusions Short-term CPAP withdrawal results in a clinically relevant increase in BP, which is considerably higher than in conventional CPAP trials and may be underestimated if only office BP values are used. OSA severity and baseline BP seem to be predictors of BP response to CPAP.