Objective: To determine the difference of plasma VIP, NO and ET concentrations in awake and in different sleep periods and the relationship between VIP, NO and ET values and the changes in nocturnal blood pressure in patients with obstructive sleep apnea syndrome(OSAS).
Methods: Retaining manometric tube in radial artery and polysomnography(PSG) were done synchronously in 12 patients with OSAS whom was diagnosed by whole-night PSG. Blood specimens were collected before sleep, during NREM sleep and REM sleep and the next morning to detect the concentrations of VIP and ET by radioimmunoassay(RIA) and NO by nitrate reductase method.
Results: (1) Plasma NO values were significantly decreased in the morning than those before sleep (P = 0.014). There was no remarkable changes of VIP and ET values in different testing periods. (2) Plasma NO and ET values in the morning were correlated with hypoxia at night, but not with AHI (P > 0.05). (3) Plasma VIP values were significantly correlated with the baseline of SBP (r = 0.654, P < 0.05) and DBP (r = 0.706, P < 0.01) in NREM sleep and that of DBP (r = 0.613, P < 0.05) in REM sleep. There was no significant correlation between BP and plasma NO and ET values in different times.
Conclusions: Endothelial dysfunction associated with NO reduction might be present and VIP might be involved in regulating BP changes in patients with OSAS.