Effects of CPAP on Blood Pressure and Sympathetic Activity in Patients With Diabetes Mellitus, Chronic Kidney Disease, and Resistant Hypertension

BACKGROUND: Patients with obstructive sleep apnea (OSA) have increased sympathetic activity and frequently also have resistant hypertension (HTN). Treatment of OSA with continuous positive airway pressure (CPAP) decreases awake and sleep blood pressure (BP) and sympathetic activity. This study was designed to assess the effect of treatment of OSA with CPAP on sympathetic activity and BP in patients with diabetes mellitus (DM), chronic kidney disease (CKD), and resistant HTN. METHODS: This was a randomized, double-blind, sham-controlled trial. Patients with DM, CKD, and resistant HTN were randomized to treatment with a therapeutic or subtherapeutic CPAP for 6 weeks. They underwent 24-hour ambulatory BP monitoring and assessment of muscle sympathetic nerve activity before and after 6 weeks on treatment. RESULTS: Treatment with therapeutic CPAP caused significant decreases in awake systolic and diastolic BP from 144 to 136 mm Hg (P = 0.004) and from 79 to 74 mm Hg (P = 0.004) and in sleep BP from 135 to 119 mm Hg (P = 0.045) and from 75 to 65 mm Hg (P = 0.015) compared with treatment with subtherapeutic CPAP. In contrast, treatment with therapeutic CPAP did not decrease sympathetic activity as assessed from muscle sympathetic nerve activity. CONCLUSIONS: Decrease in BP by treatment with CPAP in patients with DM, CKD, and OSA indicates the contribution of OSA to severity of HTN in this clinical scenario. Decrease in BP in the absence of changes in sympathetic activity is suggestive that other mechanisms induced by OSA play a larger role in the maintenance of HTN in these patients.