Abstract
Measures of respiratory variability including cardioventilatory coupling (CVC), were examined in 8 Down syndrome (DS), 4 Prader Willi syndrome (PWS) and 42 non-syndromic children (median age 7 years) referred for diagnostic polysomnography. Inspiratory onsets (I) and corresponding ECG R waves were determined, I-I, R-R and R-I intervals derived, and ventilatory frequency (f), standard deviation of f (SDf), coefficient of variation of f (CVf), median I-I and kurtosis and skewness I-I calculated. Proportional Shannon Entropy of the RI-1 interval (SH alpha) was measured to quantitate CVC. SH alpha varied with age (p = 0.02), oxygen saturation (p < 0.05) and PWS diagnosis (p = 0.001) in Stage 4 but not REM sleep. SDf and CVf varied with sleep state (p < 0.00001) as did kurtosis I-I (p < 0.0001) and skewness I-I (p = 0.004). Ventilatory frequency decreased with age in REM sleep (p = 0.03) and increased in obese children in REM (p = 0.02) and Stage 4 sleep (p = 0.004). Sleep state influences respiratory variability in children and CVC may confer a physiological advantage in children with PWS. (C) 2012 Elsevier B.V. All rights reserved.