Acute effects of nasal continuous positive airway pressure on 24-hour blood pressure and catecholamines in patients with obstructive sleep apnea

To assess the acute effects of nasal continuous positive airway pressure (C PAP) on the 24-hour blood pressure and the secretion of catecholamines in u rine and plasma, we investigated the changes in the 24-hour blood pressure and urinary and plasma concentrations of epinephrine (E) and norepinephrine (NE) in 26 men with obstructive sleep apnea (OSA) with and without nasal C PAP, Nasal CPAP resulted in significant decreases in the daytime diastolic pressure (from 86 +/- 16 mmHg to 83 +/- 12 mmHg), the nighttime diastolic p ressure (from 81 +/- 12 mmHg to 77 +/- 9 mmHg) and the nighttime systolic p ressures (from 125 +/- 15 mmHg to 120 +/- 10 mmHg), There was no significan t difference between patients with and without CPAP in the daytime or night time urinary E level, but patients who received CPAP showed a significant d ecrease in daytime urinary NE level (from 156 +/- 112 mu g/14h to 119 +/- 1 01 mu g/14h) and nighttime urinary NE level (from 143 +/- 91 mu g/10h to 11 2 +/- 65 mu g/10h). The morning plasma level of NE also decreased (from 371 +/- 181 pg/ml to 273 +/- 148 pg/ml) in patients who received nasal CPAP (p <0.02), but the plasma level of E remained unchanged, There were no correla tions between PSG parameters and the reductions in blood pressure and the c atecholamine levels induced by nasal CPAP, These findings suggest that OSA contributes, at least in part, to the development of systemic hypertension by increasing sympathetic nervous activity.