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Blood Pressure Reduced In Severe Apnoea By Breathing Support

Nasal continuous positive airway pressure among patients with most severe sleep apnoea reduces blood pressure, providing significant vascular risk benefits, and substantially improving excessive daytime sleepiness and quality of life.

"We have shown a clinically important lowering of blood pressure when patients with moderate or severe obstructive sleep apnoea are given therapeutic nasal continuous positive airway pressure (nCPAP), declares Dr Robert Davies and colleagues at the Oxford Centre for Respiratory Medicine, Radcliffe Hospital, Oxford, England.

Investigators note that in more-developed countries, 2 to 4 percent of adult men, and about 1 percent of adult women, have detectable obstructive sleep apnoea, Sleep apnoea is caused by the collapse of the pharynx during sleep, which leads to airway occlusion and transient asphyxia. These events are repetitive, with severely affected patients having hundreds of obstructive episodes and arousal's every night.

Both nocturnal and daytime blood pressure are raised in patients with obstructive sleep apnoea.

An effective treatment with breathing support nCPAP is known to improve sleep quality, but the effects of this treatment on blood pressure are unclear.

Dr Davies and colleagues 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 involves the same breathing equipment delivering a reduced air pressure that does not affect the severity of sleep apnoea.

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.

The researchers found that therapeutic nCPAP reduced mean arterial ambulatory blood pressure by 2.5 mmHg, while subtherapeutic nCPAP increased blood pressure by 0.8 mmHg . This benefit was seen in both systolic and diastolic blood pressure, and during both sleep and wake.

Benefit was largest in patients with more severe sleep apnoea, and was especially substantial in patients who were being treated with drugs for hypertension.

Dr Davies said that they 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 also seen in systolic and diastolic pressure, and during both wake and sleep. The reduction in blood pressure was independent of baseline pressure, but was mostly restricted to patients with more than 30 episodes of respiratory obstruction every hour, and was greater in patients with good nCPAP compliance."

The clinicians conclude that nCPAP treatment for obstructive sleep apnoea "probably produces significant vascular risk benefits through reduced blood pressure, and substantially improves these patients' excessive daytime sleepiness and quality of life.
Lancet 2002; 359: 204-10.

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