Low-frequency respiratory rhythms in infants during the first six months of life

The aim of the study was to investigate characteristics of low-frequency co mponents in respiration. Sixteen healthy term infants were examined from th e first day up to the 6th month of life. The respirogram, instantaneous res piratory frequency and respiratory amplitude of undisturbed segments of qui et sleep phases and periodic breathing (PB) were analysed via fast Fourier transformation. The peak frequency (PF) in the low-frequency range (0.04-0. 2 Hz) was determined. PF for PB ranged from 0.056 to 0.1 Hz. Further, low-f requency rhythms (LFR) of the respirogram, which were stable during the rec ordings as well as during development, were found ranging from 0.045 to 0.0 67 Hz. The LFR of the respirogram is correlated with rhythmic changes in th e relationship between inspiratory and expiratory amplitudes. The frequency of the LFR was significantly lower than that of the PB. The data indicate that LFR and PB are low-frequency respiratory rhythms which are separately controlled and perform independently.