Short-term continuous positive airway pressure therapy reverses the pathological influence of obstructive sleep apnea on blood rheology parameters.

Our aim was to analyze rheological properties of blood and plasma in patients (n=31) with obstructive sleep apnea (OSA) before and after five nights of continuous positive airway pressure (CPAP) therapy as compared with a well-matched control group (n=19). Rheology measurements included blood viscosity, plasma viscosity, erythrocyte elongation and erythrocyte deformability variables specific to the aggregation process. The mean whole blood viscosity of the OSA groups was 18.6% higher than that of the control group (P<0.001), plasma viscosity was 7.2% higher (P<0.001), and the blood count was 6% higher (P<0.001). The corrected viscosity of the OSA group was elevated 6.6% (P<0.05) and the aggregation index was 9.3% higher (P<0.05) relative to the control group. Aggregation half-time of the OSA group was 23.5% shorter than that of the control group (P<0.05). Following CPAP therapy, the rheological variables of the OSA group were significantly reduced: whole blood viscosity was 10.5% lower (P<0.001), plasma viscosity was 4.1% lower (P<0.05), corrected blood viscosity was 4.8% lower (P<0.05), and the aggregation index was 7% lower (P<0.05), while the aggregation half-time was increased 25.4% (P<0.05). There were significant correlations between rheologic and polysomnographic variables for the OSA group. Therefore, five consecutive nights of CPAP therapy improved blood rheological properties in patients with OSA. These findings may help to determine cardiovascular prognoses in these patients.