Analysis of periodic changes in ventilation in new-born infants.

1. Ventilation was recorded in thirty term infants during the first week after delivery using the trunk plethysmograph, during periods of rapid eye movement sleep (r.e.m.) and quiet sleep (n.r.e.m.). 2. Continuous histograms of tidal volume (VT) and instantaneous respiration rate (f) were samples at 0.5 sec intervals, passed through a digital filter to remove long-term trends in the data, and then subjected to frequency analysis. 3. In all the infants oscillations in VT and f were detected, with mean periods varying from 6.7 to 12.5 sec. The amplitude of these oscillations was higher during r.e.m. than n.r.e.m. sleep in all the infants. 4. The oscillations in VT tended to be out of phase with those for f, particularly during n.r.e.m. sleep; this contrasted with in-phase oscillations in VT and f found during periodic breathing in an additional six premature infants studied.