| Objective To investigate the efficacy and possible mechanism of continuous positive airway pressure (CPAP) treatment on blood pressure in patients with obstructive sleep apnea syndrome (OSAS) and resistant hypertension (RH).Methods Thirteen OSAS patients with RH were recruited. Before and on three months' CPAP treatment, their blood pressures at 10:00 PM, 2:00 AM and 6:00 AM were measured, and their morning plasma concentrations of aldosterone (ALD) and plasma renin activity (PRA) were tested at supine position with radioimmonoassay.Results Compared with blood pressure parameters before CPAP treatment, there was a significant decrease in blood pressure on three months' CPAP treatment (all P<0.01 ), which include decrease in systolic blood pressure(SBP) at 10:00PM (152.2mmHg±19.2mmHg vs 135.5 mmHg±2.8mmHg), at 2:00AM (156.6mmHg±19.4mmHg vs 133.1mmHg±2.4mmHg) and at 6:00AM(172.1mmHg±23.7mmHg vs 151.5 mmHg±3.0mmHg );as well as decrease in diastolic blood pressure (DBP) at 10:00PM(98.9mmHg±15.6mmHg vs 84.2mmHg±4.6mmHg) , at 2:00AM(102.8mmHg±16.6mmHg vs 81.5mmHg±4.6mmHg) and at 6:00AM(50.9mmHg±16.9mmHg vs 50.7mmHg±4.3mmHg). Before CPAP treatment ,neither SBP nor DBP at 2:00AM showed significant change compaired with SBP and DBP at 10:00PM (P>0.05). However ,following three months' CPAP treatment both SBP and DBP at 2:00AM were significantly lower than those at 10:00PM (P<0.01) . Comparison of plasma concentrations of ALD and PRA before and on three months' CPAP treatment indicated that there was a significant difference in ALD (195.5ng/L±15.1ng/L vs 148.3ng/L±19.4ng/L, P<0.01 ) , but not significantly different in PRA (0.20μg·L-1·h-1±0.12μg·L-1·h-1 vs 0.27μg·L-1·h-1±0.14μg·L-1·h-1, P=0.221).Conclusions CPAP treatment could significantly improve RH,restore the physiological dipping of blood pressure at midnight, and reduce plasma ALD concentration. Elevated plasma ALD concentration is possibly involved in pathogenesis of RH in OSAS patients.
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