RESUMEN
Although it is well known that autonomic dysfunction in obstructive sleep apnea syndrome (OSAS) is associated with hypertension, its relationship to hypotension and orthostatic dysregulation is still unclear. We examined the response of blood pressure (BP) and cardiovascular autonomic function to head-up tilt (HUT) test in patients with OSAS. In this study, 14 patients(mean age: 65+/-2 years old, male/female: 11/3) with diagnosed OSAS by overnight polysomnography and 84 healthy subjects(mean age: 62+/-1 years old, male/female: 46/38) underwent HUT test(from 5 to 10 min at 45 degrees). Autonomic functions were evaluated by spectrum analysis of blood pressure and heart rate variability. In healthy subjects, systolic BP was unchanged by HUT test due to the enhancement of sympathetic nerve activity and the inhibition of parasympathetic nerve activity. In contrast, autonomic responses were unchanged and systolic BP tended to be decreased by HUT test in OSAS patients. In conclusion, the results of this study suggest that baroreflex function is impaired in patients with OSAS. Furthermore, HUT test with spectrum analysis may be useful to evaluate autonomic functions in OSAS patients.
