Increased vasoconstrictor sensitivity in obstructive sleep apnea

We studied vasoconstrictor sensitivity and cholinergic responsiveness of th e forearm vasculature in 10 male patients with obstructive sleep apnea (OSA ) and 10 healthy controls. Subjects with regular medication, known arterial hypertension, diabetes mellitus, or dyslipidemia were not included in this study. Age, body mass index, blood pressure, blood glucose, serum lipids, and baseline forearm vascular conductance (derived from venous occlusion pl ethysmography and intra-arterial blood pressure measurement) did not differ significantly between these two groups. With use of three dosage steps eac h, angiotensin II and acetylcholine were successively infused into the brac hial artery. During infusion of angiotensin II, mean conductance was 39.6% lower (P = 0.002) in the OSA patients compared with that in the control sub jects. Vascular responsiveness to increasing dosages of acetylcholine was n ot significantly altered in the OSA group. These findings suggest an enhanc ed vasoconstrictor sensitivity in the forearm vasculature in OSA. The hypot hesis that endothelial function in OSA is impaired independently of other c ardiovascular risk factors is not supported by the present results.