Background Obstructive sleep apnoea syndrome (OSAS) is associated with cardiovascular disease, especially in patients with high blood pressure. Continuous positive airway pressure (CPAP) seems to contribute to blood pressure control in patients with OSAS, mainly those with uncontrolled hypertension. However, the effect of CPAP on controlled hypertensive patients with OSAS is not known.

Objective To evaluate the effects of CPAP on blood pressure of controlled hypertensive patients with OSAS.

Design Prospective cohort study.

Patients 36 recently diagnosed patients with OSAS and hypertension controlled with oral antihypertensive medication.

Methods CPAP was performed for 5 days. Systolic and diastolic blood pressure were recorded at baseline and 5 days later using 24 h ambulatory blood pressure measurement.

Results Mean (SD) 24 h systolic blood pressure was reduced from 128.9 (3.4) to 126.5 (3.5), p<0.001 and mean (SD) 24 h diastolic blood pressure was reduced from 86.9 (3.3) to 84.8 (3.3), p<0.001. A reduction in the proportion of ‘non-dippers’ in the participants was registered (from 40.6% at baseline to 18.2%).

Conclusions A short course of CPAP may reduce systolic and diastolic blood pressure in patients with OSAS and controlled hypertension.

Trial registration number RBR – 386qsg; Brazilian Clinical Trials Registry (REBEC).