Cardioventilatory coupling and inter-breath variability in children referred for polysomnography

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 (SHα) was measured to quantitate CVC. SHα 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.

► Cardioventilatory coupling (CVC) occurs in children in REM and NREM sleep. ► CVC is more commonly seen with increasing age in Stage 4 sleep. ► Prader Willi syndrome subjects exhibit more CVC in Stage 4 sleep than other children. ► CVC is associated with higher oxygen saturation in Stage 4 sleep.