Objective: To evaluate endothelium-dependent vascular function in obstructive sleep apnoea patients.
Design and methods: Forearm blood flow and vascular resistance were studied in eight normotensives and eight obstructive sleep apnoea patients and also in eight normotensive and eight hypertensive controls after graded brachial artery infusion of acetylcholine (10-60 micrograms/min) and sodium nitroprusside (1-6 micrograms/min), respectively. Patients and controls were matched for age, sex and body weight.
Results: Forearm blood flow after acetylcholine infusion was reduced 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 no difference between hypertensive and normotensive subjects. However, the hypertensive obstructive sleep apnoea group exhibited a reduced flow response to sodium nitroprusside compared with that of their corresponding hypertensive controls. Minimal forearm vascular resistance after acetylcholine infusion and after sodium nitroprusside infusion was higher in obstructive sleep apnoea patients than it was in controls.
Conclusions: 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 findings suggest a vascular pathogenetic link between obstructive sleep apnoea and systemic hypertension.