Sympathetic activity in children with OSA evaluated by Poincaré plot analysis and morning urine norepinephrine levels

Heart rate variability i.e. the continuous oscillation of the R-R interval around its mean value can be evaluated using Poincare plots. Narrow Poincare scattergrams indicate enhanced sympathetic activity. The aim of this study was to confirm increased sympathetic tone in children with obstructive sleep apnea (OSA) by applying graphic analysis of the Poincare plot. Methods: Subjects with and without OSA were recruited. The width of the plot obtained during overnight polysomnography and the norepinephrine concentration in morning urine specimen were the outcome measures. Results: Fourty four children with OSA (24 with SpO2 nadir ≥90% or mild hypoxemia; 20 with SpO2 nadir