[Correlation between respiration and heart rate in 12- to 14-year-old children during sleep and wakefulness].

The coupling of respiratory and cardiac rhythm is determined by interactions of oscillating brain stem centers and external physical and psychical influences. Not well known are effects of sleep and wakefulness which will be investigated over the day. From the ECG and respirogram of 42 healthy children (11 female, 31 male, 12 to 14 years) during 24 h the time series of instantaneous heart rate (HR) and respiratory rhythm and from this by FFT the density spectra of power, the maximal power and related frequency in the respiratory range were ascertained. Differences between nonREM sleep and wakefulness and the strength of coupling were determined by coherence analysis. In all probands the maximal power of HR and of the coherence were higher during nonREM sleep than in wakefulness. Both values were stable during each state. The maximum related frequencies of HR and respiration shifted parallel between sleep and wakefulness. The results mean augmentation in nonREM sleep following to improved transfer of respiratory activity to the control of HR. The increased coherence hints at a stronger linear coupling which is stable during each state. The changes of cardiorespiratory coupling may be effected by stronger non-linear parts in the interactions during wakefulness.