ATTENUATED ENDOTHELIUM-DEPENDENT VASCULAR RELAXATION IN PATIENTS WITHSLEEP-APNEA

Objective To evaluate endothelium-dependent vascular function in obstr uctive sleep apnoea patients. Design and methods Forearm blood flow an d vascular resistance were studied in eight normotensives and eight ob structive sleep apnoea patients and also in eight normotensive and eig ht hypertensive controls after graded brachial artery infusion of acet ylcholine (10-60 mu g/min) and sodium nitroprusside (1-6 mu g/min), re spectively. Patients and controls were matched for age, sex and body w eight Results Forearm blood flow after acetylcholine infusion was redu ced in patients compared with that in controls (peak flows were 6.0 +/ - 0.7 and 9.8 +/- 1.5 ml/min for 100 g, respectively), but there was n o difference between hypertensive and normotensive subjects. However, the hypertensive obstructive sleep apnoea group exhibited a reduced fl ow response to sodium nitroprusside compared with that of their corres ponding hypertensive controls. Minimal forearm vascular resistance aft er acetylcholine infusion and after sodium nitroprusside infusion was higher in obstructive sleep apnoea patients than it was in controls. C onclusions Endothelium-dependent vascular relaxation in patients with obstructive sleep apnoea was reduced independently of hypertension. An additional defect in endothelium-independent vascular relaxation was found in obstructive sleep apnoea patients with hypertension. These fi ndings suggest a vascular pathogenetic link between obstructive sleep apnoea and systemic hypertension.