Autonomic cardiovascular tests in children with obstructive sleep apnea syndrome

Study Objectives: The aim of our study was to investigate cardiovascular autonomic activity during wakefulness, using cardiovascular tests, in a population of children with OSAS. Design: Prospective study. Setting: Sleep unit of an academic center. Participants: We included 25 children (mean age 10.2 +/- 2.3 years) undergoing a diagnostic assessment for OSAS, and 25 age-matched healthy control subjects. All subjects underwent an overnight polysomnography and autonomic cardiovascular tests using parts of the Ewing test battery, which is a physiological test used for the assessment of autonomic function (head-up tilt test, Valsalva maneuver, deep breathing test). Measurements and Results: Eighteen of 25 children with OSAS (11 males, mean age 9.4 +/- 1.7 years) concluded the study. OSAS patients had higher systolic blood pressure, diastolic blood pressure, baseline heart rate, the 30:15 index (which represents the RR interval at the 15th and 30th beats during the head up tilt test), and delta diastolic and systolic blood pressure during the head-up tilt test, while the heart rate variability during the deep breathing test was lower, compared with controls. A positive correlation between systolic and diastolic blood pressure and the apnea-hypopnea index (AHI), and negative between AHI and both the 30:15 index and Valsalva ratio, were found. Stepwise linear regression analysis detected a negative correlation between AHI and the 30:15 index and Valsalva ratio, a positive correlation between overnight mean oxygen saturation and delta heart rate, and between AHI and delta systolic blood pressure. Conclusions: Our data point to an increase in basal sympathetic activity during wakefulness and to an impaired reaction to several physiological stimuli, which is dependent on the severity of OSAS.