Ventilation and sleep state in the new-born.

1. Ventilation, oesophageal pressure and sleep state were measured in fourteen babies between 25 hr and 7 days of age.2. Trunk plethysmograph records showed that respiratory rate and minute volume were significantly higher in REM sleep than non-REM sleep. Tidal volume was not significantly altered.3. Tidal volume, respiratory rate and minute volume were all more variable in each baby in REM sleep, both on breath to breath analysis and over successive 20 sec periods.4. Major oesophageal peristaltic activity was observed in REM sleep only.5. In response to a sharp rise in P(O2) the tidal volume and minute volume fell significantly by the same proportion in both sleep states. Respiratory rate did not change significantly.