Analysis of cardiorespiratory signals--methodology and applications in infants.

Heart rate variability and thoracal respiratory movements were examined in two babies aged six months during eight hour polysomnographic recordings. Computer-assisted analysis in the time and frequency domain were performed to investigate the mechanisms underlying cardiorespiratory control. Coherence and phase relation between cardiac cycles and respiration were investigated in detail. Both methods demonstrated that during quiet sleep (stage 3/4), the cardiorespiratory coupling was significantly increased as compared to active sleep (REM sleep).