Obstructive sleep apnea (OSA) is common in patients with resistant hypertension, and the severity of OSA correlates with the severity of hypertension. OSA has been shown to be present in 70% to 85% of patients with resistant hypertension who are referred for a sleep study.[1-3] OSA is also more common in patients with resistant hypertension than controlled hypertension,[3] and the incidence and severity of OSA is also higher in men than women.[2-4]

The effect of treatment of OSA with continuous positive airway pressure (CPAP) usually provides a modest benefit in blood pressure (BP) reduction of about 2 mm Hg among patients with hypertension.[5] The reduction in BP from use of CPAP is less than that seen with monotherapy with an antihypertensive medication.[6] However, the positive effect of CPAP in reducing BP has not been demonstrated in all trials,[7, 8] probably as a result of methodological issues and use of different study populations and that not all studies include patients with baseline hypertension and some studies allow the use of medications while others have not.[7-9] In 2 of 3 studies that enrolled only patients with baseline hypertension, treatment with CPAP did not show a benefit on reduction in BP, suggesting that hypertensive changes may become resistant to the effects of CPAP therapy in patients with longstanding hypertension.[7-9] There also seems to be a greater reduction in BP in patients with greater excessive daytime sleepiness.[8, 10] The reduction in BP is also greater with more severe OSA or greater degree of nocturnal hypoxemia.[5, 9]

One reason that CPAP may not be successful in lowering BP may be that adherence to CPAP is often suboptimal and a recent study hypothesized that nocturnal supplemental oxygen would reduce BP in patients with OSA. In this study, patients aged 45 to 75 years had established coronary artery disease or 3 symptoms among hypertension, diabetes, obesity, and dyslipidemia.[11] Patients were randomized to control (healthy lifestyle and sleep education) vs education and CPAP treatment vs education and nocturnal supplemental oxygen. Outcomes were measured as 24-hour ambulatory BP. Results showed that adherence to CPAP was significantly worse than adherence to nocturnal supplemental oxygen but CPAP had a significantly greater effect in lowering mean arterial pressure in patients than in those randomized to nocturnal supplemental oxygen (difference, 2.8 mm Hg; 95% confidence interval, 0.5–5.1). Both supplemental oxygen and CPAP significantly improved nocturnal hypoxemia compared with the control group. Another possibility is that although daytime sleepiness does improve with CPAP, it may be that the lack of change in weight or dietary habits on CPAP are more important than improved sleep quality in lowering BP in treated hypertensive patients.

In summary, treatment of OSA with CPAP can lower BP, but reductions are often modest. However, the associations of OSA with other comorbidities (eg, coronary disease, atrial fibrillation, sleep-related accidents) remain important reasons to pursue sleep histories in hypertensive patients in whom OSA is common.


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  2. References
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    Gottlieb DJ, Bhatt DL, et al. Effect of continuous positive airway pressure and nocturnal supplemental oxygen on blood pressure in patients with obstructive sleep apnea: the HeartBEAT randomized clinical trial. Sleep. 2013; Abstract 0331.