Breathing support reduces blood pressure for people with sleep apnoea

A reduction in blood pressure--and in the probable risk of stroke and other cardiovascular disease--could be possible for patients treated with nocturnal breathing support for sleep apnoea, conclude authors of a study in this week's issue of THE LANCET.

Obstructive sleep apnoea is a serious condition in which airflow from the nose and mouth to the lungs is restricted during sleep; it is second only to asthma as a cause of chronic respiratory disease. It is characterised by loud snoring, daytime sleepiness (due to poor-quality sleep), and a fall in the oxygen concentration in blood, and is associated with increased blood pressure and a raised cardiovascular risk profile. Untreated sleep apnoea patients have about a 3% risk of a stroke or other cardiovascular event each year. An effective treatment for sleep apnoea with a breathing support device called nasal continuous positive airway pressure (nCPAP) is known to improve sleep quality, but the effects of this treatment on blood pressure are unclear.

Robert Davies and colleagues from Oxford Radcliffe Hospital, UK, did a randomised trial of nCPAP, to compare the change in blood pressure in 118 men with severe obstructive sleep apnoea. Patients were assigned to either therapeutic or subtherapeutic nCPAP for one month. Subtherapeutic nCPAP involved the same breathing equipment delivering a reduced air pressure that did not affect the severity of sleep apnoea. The primary outcome was the change in 24-hour average blood pressure. Other outcomes were changes in systolic and diastolic blood pressure and pressures while the patient was asleep and awake, and relations between blood pressure changes, baseline blood pressure, and severity of sleep apnoea.

Therapeutic nCPAP reduced mean arterial blood pressure by 3.3 mm Hg compared with the subtherapeutic control. This benefit was seen in both systolic and diastolic blood pressure, and during both sleep and while awake. The benefit was largest in patients with more severe sleep apnoea, and was especially substantial in patients also taking drug treatment for high blood pressure.

Robert Davies comments: "We have shown a clinically important lowering of blood pressure when patients with moderate or severe obstructive sleep apnoea are given therapeutic nCPAP. This result is confirmed by comparison with a robust control and is seen in both systolic and diastolic pressure, and during both wake and sleep. As a result of this reduction we conclude that nCPAP treatment for obstructive sleep apnoea probably produces a significant reduction in the risk of stroke and other cardiovascular diseases as well as substantially improving these patients' excessive daytime sleepiness and quality of life."

Contact: Dr Robert Davies, Oxford Sleep Unit, The Oxford Centre for Respiratory Medicine, Churchill Hospital Site, Oxford Radcliffe Hospital, Headington, Oxford OX3 7LJ, UK; T) +44 (0)1865 225230; M) +44 (0)7767 440702; F) +44 (0)1865 225205; E) [email protected]