Ventilatory functions of normal rats of different ages

1. Lung volume, respiratory mechanics and flow-volume curve were measured in 96 male Wistar rats weighing from 102 to 521 g. Their ages ranged from 31 to 137 days and therefore, most of them were in the rapidly growing phase. 2. Data except for functional residual capacity were obtained under conditions of artificial ventilation. 3. Total lung capacity and the fractions of lung volume of these animals were found to relate linearly with their body weights. 4. Most of the parameters concerning respiratory mechanics and flow-volume curve also changed generally in proportion to their body weights, but those standardized for lung volume were not constant but varied depending on the weights. 5. These results suggest that the mechanical properties of lungs of young rats are age-related and comparisons of ventilatory functions among those animals should be carefully done.