Influence of sleep respiratory disturbance on nocturnal blood pressure

We subjected 65 patients to overnight monitoring and continuous nocturnal blood pressure measurement in order to assess the influence of sleep apnea on the circulatory system. Thirty-one patients were compared before and after surgery. The severity of sleep apnea was classified by means of the apnea-hypopnea index (AHI), the duration of exposure to low-level oxygen [calculated as the desaturation time (DT)] and changes in blood pressure (BP). Before surgery, a significant correlation was noted between DT and changes in BP. Therefore, DT was considered useful for assessing the influence of sleep apnea on nocturnal BP. After surgery, an improvement in AHI of > 50% was noted in 19/31 patients (61.3%), a result comparable to that described in the literature. Improvements in DT and change in BP were > 50% in 21/31 (67.7%) and 14/ 31 (45.2%) patients, respectively. With regard to the severity of sleep apnea before surgery, AHI was > or = 50 and DT > or = 40% in 10 and 18 patients, respectively and 19 patients showed changes in BP of > or = 40 mmHg. After surgery, one, five and two patients, respectively, still showed these values. Thus, a beneficial effect of surgery was demonstrated.