[Effect of positive pressure respiration on diurnal catecholamine excretion by patients with obstructive sleep apnea]

The aim of the study was to investigate effects of CPAP treatment on diurnal catecholamine excretion in urine in patients with obstructive sleep apnea (OSA). 12 males with severe OSA (mean AHI = 63) were measured in 3 separate 8 hour samples by fluorimetric method. NA levels were higher in OSA patients in all urine samples than in obese, mildly hypertensive males (control group = C). In C group patients NA levels were significantly lower at night than during the day contrary to OSA patients in whom NA levels dropped insignificantly during sleep. In OSA patients NA levels during sleep correlated with severity of apneas (r = 0.42) and night hypoxaemia (r = -0.46). CPAP treatment resulted in significant fall in NA levels during sleep (p < 0.01). A levels did not change after CPAP treatment. We conclude that abnormally high NA level during sleep in OSA patients may be related to sleep fragmentation and hypoxia. CPAP treatment restores normal circadian rhythm of NA excretion.