title: Endothelial function in obstructive sleep apnea and response to treatment.
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.
authors.affiliation: Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong SAR, China. msmip@hkucc.hku.hk
authors.forename: Mary S M
authors.initials: MS
authors.lastname: Ip
authors.forename: Hung-Fat
authors.initials: HF
authors.lastname: Tse
authors.forename: Bing
authors.initials: B
authors.lastname: Lam
authors.forename: Kenneth W T
authors.initials: KW
authors.lastname: Tsang
authors.forename: Wah-Kit
authors.initials: WK
authors.lastname: Lam
mesh_terms: D000328:Adult; D001795:Blood Pressure Determination; D015150:Echocardiography, Doppler; D004730:Endothelium, Vascular / Q000503:physiopathology*; D006801:Humans; D017214:Laryngeal Masks; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D017286:Polysomnography; D011175:Positive-Pressure Respiration; D011336:Probability; D012016:Reference Values; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000628:therapy*; D016896:Treatment Outcome; D014655:Vascular Resistance / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology; D014664:Vasodilation / Q000502:physiology