Erythrocyte deformability, plasma viscosity and oxidative status in patients with severe obstructive sleep apnea syndrome

Background and purposeIn patients with severe obstructive sleep apnea syndrome (OSAS), diurnal changes of plasma viscosity and erythrocyte deformability were measured to elucidate the possible mechanism of cardiovascular diseases in OSAS patients.Patients and methodsPlasma viscosity and erythrocyte deformability was determined in 11 OSAS patients and 11 healthy subjects matched by sex and age. Plasma viscosity was measured by a cone-plate viscometer, and erythrocyte deformability was determined by filtration technique. Whole blood counts were performed and oxidative status of the patients' plasma and erythrocytes were evaluated.ResultsOSAS patients had higher plasma viscosity than controls, both in the morning (1.74±0.3 vs. 1.36±0.2 mPa s, P<0.002) and evening (1.55±0.2 vs. 1.27±0.1 mPa s, P<0.002), and morning plasma viscosity was significantly higher than the evening level (P<0.05). Morning plasma viscosity of patients was inversely correlated with their mean nocturnal SaO2. Morning plasma malonyldialdehyde level was significantly higher in the patients than in the controls (69.7±30.5 vs. 45.5±11.0 nmol/l, P<0.005). Erythrocyte deformability of the patients was slightly lower.ConclusionsWe have observed that plasma viscosity is high both in the morning and in the evening in severe OSAS patients. This elevation may predispose OSAS patients to myocardial infarction and stroke by increasing blood viscosity. Low nocturnal mean SaO2 may be responsible for the high plasma viscosity in these patients.