Endothelial Function in Obstructive Sleep Apnea and Response to Treatment

TLDR

Impaired endothelium‑dependent vascular relaxation is a prognostic marker of atherosclerosis and cardiovascular disease. The study evaluated flow‑mediated dilation and nitroglycerin‑induced dilation of the brachial artery in men with and without obstructive sleep apnea. Participants with OSA were randomized to nasal continuous positive airway pressure or observation for four weeks, and a subset using nCPAP for over three months was reassessed after one week of withdrawal. Men with moderate/severe OSA exhibited markedly reduced flow‑mediated dilation compared with controls, and nasal CPAP improved FMD, but the improvement vanished after treatment cessation, while nitroglycerin‑induced dilation remained unchanged.

Abstract

Impaired endothelium-dependent vascular relaxation is a prognostic marker of atherosclerosis and cardiovascular disease. We evaluated endothelium-dependent flow-mediated dilation (FMD) and endothelium-independent nitroglycerin (NTG)-induced dilation of the brachial artery with Doppler ultrasound in 28 men with obstructive sleep apnea (OSA) and 12 men without OSA. Subjects with OSA (apnea-hypopnea index; mean +/- SD, 46.0 +/- 14.5) had lower FMD compared with subjects without OSA (5.3 +/- 1.7% vs. 8.3 +/- 1.0%, p < 0.001), and major determinants of FMD were the apnea-hypopnea index and age. There was no significant difference in NTG-induced dilation. Subjects with OSA were randomized to nasal continuous positive airway pressure (nCPAP) or observation for 4 weeks. Subjects on nCPAP had significant increase in FMD, whereas those on observation had no change (4.4% vs. -0.8%, difference of 5.2%, p < 0.001). Neither group showed significant change in NTG-induced vasodilation. Eight subjects who used nCPAP for over 3 months were reassessed on withdrawing treatment for 1 week. On nCPAP withdrawal, FMD became lower than during treatment (p = 0.02) and were similar to baseline values. Our findings demonstrated that men with moderate/severe OSA have endothelial dysfunction and treatment with nCPAP could reverse the dysfunction; the effect, however, was dependent on ongoing use.