The development of periodicity of heart rate and respiration during sleep in newborn babies.

Polygraphic records of EEG, ocular movements, respiration, and heart rate were made continuously in 10 full term babies between 2 and 7 days old. Power spectral analysis was then computed for heart and respiratory rate. The period durations obtained by this method ranged from 20 to 70 minutes. Most of the power spectra showed two maxima. In many cases cycles of respiration and heart rate were not identical. The experiments show that newborns have two separate cycles with different period durations. Most probably the shorter cycle originates from the fetal life, the longer one represents the development of the periodicity of the adult.