THE EFFECT OF THE SUPPRESSION OF APNEA ON BLOOD-PRESSURE AND PLASMA-CATECHOLAMINES IN NORMOTENSIVE SUBJECTS WITH SLEEP-APNEA

BACKGROUND: The association of high blood pressure (HBP) and the sleep apnea syndrome (SPS) and the beneficial effect of SAS treatment on HB P are well known. The direct effect of the continuous nocturnal admini stration of positive air pressure (CPAP) on blood pressure is not, how ever, well known. The aim of this study was to evaluate the blood pres sure (BP), plasma cathecolamines (PC) and urinary derivatives of cathe colamines (UDC) in 17 normotensive subjects (4 females; age 49 +/- 11 years) with SAS, prior to and after correction of apnea with CPAP. MET HODS: Twenty-four hour outpatient registry of blood pressure (OPRBP) a nd after nocturnal polysomnography were performed both basal and durin g CPAP administration for two nights. Urine was collected over these 2 4 hour period for measurement of UDC. At 7 hours a blood sample was co llected for measurement of PC. RESULTS: SAS was corrected by CPAP in a ll the patients with a reduction in mean BP (24 h: 87 +/- 6 vs 84 +/- 6 mmHg, p < 0.05, diurnal, 90 +/- 6 vs 87 +/- 6 mmHg, p < 0.05, noctur nal, 84 +/- 6 vs 82 +/- 7 mmHg, NS) and the percentage of diastolic BP > 90 mmHg (24 h: 10 +/- 7 mmHg vs 6.5 +/- 6 mmHg, p < 0.01, diurnal, 15 +/- 10 vs 10 +/- 10 mmHg, p < 0.05, nocturnal 5.2 vs 5 vs 3 +/- 4 m mHg, p < 0.05). The plasma cathecolamines tended to reduce, although n ot significantly, without changes of urinary metabolites. CONCLUSIONS: There is a significant decrease in blood pressure with the administra tion of continuous positive air pressure even in normotensive patients . An early correction of sleep apnea syndrome may reduce the high prev alence of hypertension associated with this syndrome.