Effect of Continuous Positive Airway Pressure (CPAP) on Systemic Blood Pressure, Coagulability and Carotid Intima-media Thickness in Patients With Sleep Apnea

Sleep-disordered breathing (SDB) briefly means cessation of breathing during sleep at least 5 times per hour. Sleep-disordered breathing affects 9 to 24% of the middle-aged and overall 4% of the middle-aged males suffers from Obstructive sleep apnea syndrome (OSAS) i.e. SDB with associated daytime sleepiness. Several major epidemiological studies have shown that SDB is not only an independent risk factor for systemic hypertension but it is also associated with cardiovascular complications such as heart failure, stroke, and sudden death.

The mechanisms for the linkage between Sleep-disordered breathing and cardiovascular diseases are not fully determined but surges in sympathetic nerve activity are seen at the end of each apneic episode accompanied by large rises in systemic arterial blood pressure (BP). The increased levels of muscle sympathetic nerve activity are diminished by nasal continuous positive airway pressure (CPAP) therapy. Numerous studies have found a hypercoagulable state in terms of increased clotting factor and platelet activities, and impaired fibrinolysis in coronary artery disease, ischaemic stroke, and sleep-disordered breathing. Common carotid artery intima-media thickness (IMT) has been shown to correlate with traditional vascular risk factors and may predict the likelihood of acute coronary events and stroke. Recently, carotid artery intima-media thickness has been shown to have positive correlations with the severity of sleep disordered breathing.

Despite robust evidence showing improvement of symptoms, cognitive function and quality of life in patients with obstructive sleep apnea treated with nasal continuous positive airway pressure, there are conflicting short-term data whether continuous positive airway pressure can reduce blood pressure in patients with obstructive sleep apnea. This randomized controlled study aims to assess the long-term effects of nasal continuous positive airway pressure on 1) 24 hr systemic blood pressure; 2) Coagulation state; and 3) Carotid artery intimal media thickness.