Developmental changes in ventilation and breathing pattern in unanesthetized kittens

Ventilation and the breathing pattern of 12 intact, unanesthetized, unrestrained kittens, were recorded at intervals from the second postnatal day to the end of the eighth month. Five of the animals were also studied at 12 months of age. Ventilation (VE) became stable by the 5th month, whereas body weight was still increasing. The relationship between tidal volume (VT) and breathing rate (BR) changed with age. During the 1st month, BR fell and VT increased, VE increasing slowly. From 1 to 5 months, BR remained nearly constant while VT increased. Finally, from 5 to 12 months, BR decreased slightly, VT increased slightly, and VE did not change. The results are compared with relevant data from the literature, especially those derived from interspecific analyses.