Endothelial Function in Normotensive Men with Obstructive Sleep Apnea Before and 6 Months After CPAP Treatment

Study Objectives: To evaluate endothelium-dependent flow-mediated dilation (FMD) and endothelium-independent nitroglycerin (NTG)-induced dilation of the brachial artery with Doppler ultrasound in patients with obstructive sleep apnea (OSA) and impact of six months of continuous positive airway pressure (CPAP) treatment. Design: A prospective, controlled, observational study. Setting: Single-site, clinic-based. Patients: Twenty-nine normotensive men with OSA (apnea-hypopnea index [AHI], mean +/- SD, 60.4 +/- 22.1-h), and 17 men without OSA (AHI 2.5 +/- 0.6-h). Interventions: Six months of CPAP therapy in OSA patients. Measurements and Results: FMD was lower in patients with OSA compared with in controls (7.19 +/- 1.78 % vs 10.93 +/- 2.59 %; P < 0.001) while NTG-induced vasodilation was similar in both groups (13.75 +/- 1.01 % vs 14.25 +/- 1.83 %; n.s.). An inverse relationship was found between FMD and AHI adjusted for age and body mass index (BMI) (beta = -0.05, P < 0.001). Following 6 months of CPAP treatment in the OSA group, FMD was increased from 7.38 +/- 2.06 % to 10.45 +/- 1.68; P = 0.001) in 20 patients compliant with the device whereas the corresponding values did not change in the non-user group (7.08 +/- 1.50% vs 7.26 +/- 1.01 %). No significant changes were observed regarding the NTG-induced vasodilation after CPAP compared with the baseline values. Conclusions: Our results confirm the previous reports suggesting impaired endothelium-dependent FMD in OSA, and additionally document the sustained improvement in endothelial function after 6 months of CPAP treatment in complaint patients.