Role of catecholamine in nocturnal hypertension in obstructive sleep apnea syndrome

Since blood pressure (BP) swings occur during sleep apneas, we studied the relationship between nocturnal BP and catecholamine excretion (assessed by urinary concentration) in 10 patients with obstructive sleep apnea syndrome (OSAS). Ten subjects with a similar age were taken as controls for norepinephrine (NE) and epinephrine (E) nocturnal excretion values. BP was continuously monitored in the patients during two polysomnographic studies: the first without treatment, the second with the application of nasal continuous positive airway pressure (CPAP), to prevent apneas and the associated BP wsings. Nocturnal NE excretion was also higher in the patients, but it decreased with CPAP, although it remained significantly higher than in controls: however, the decrease was not correlated to the mean BP swings observed in the untreated patiens during apneas. These results suggest that both NE and E are higher in OSAS subjects than in normals: the decrease in E with acute CPAP may indicate that apnea recurrence could be immediately responsible for at least part of E release, whereas BP swings do not seem causally related to increased catecholamine release.