Spectral Analysis of Periodic and Normal Breathing in Infants

Spectral analysis techniques are used to study periodic and normal breathing in infants. Power density spectra of respiration and heart rate are obtained using the fast Fourier transform technique. For the periodic breathing case, these spectra are used to determine the coherency function. From these results, information is obtained about: 1) the modulation of heart rate by respiration, 2) the strength of the modulation as indicated by the coherency, and 3) for cases where the coherency is high, an estimate of the time delay between respiration and heart rate interaction. For the normal breathing case, the spectra revealed a low-frequency component which is approximately equal to the frequency of periodic breathing when this occurs. This low-frequency component is also present in the heart rate, suggesting a low-frequency modulation of cardiovascular control as well.