Mechanical properties of the lungs in the rat.

Abstract

A study of the mechanical properties of the lungs in specific-pathogen-free (SPF) rats and ordinary (non-SPF) rats has been carried out using anesthetized animals. Pulmonary compliance was measured under static conditions; the measured pulmonary resistance was that offered by the airway and tissues during flow. In the SPF rats, the mean pulmonary compliance was 0.25 ml/cm H2O (SD = 0.04) and the mean pulmonary resistance in tracheostomized animals was 0.14 cm H2O/ml/sec (SD = 0.04). Upper airway resistance was estimated to be 53% of the total pulmonary flow resistance. For the purposes of comparison between the SPF and non-SPF groups, the animals were arbitrarily divided into two subgroups (young and old) using 12 months as the dividing line. Pulmonary resistance was compared in tracheostomized animals because upper airway resistance accounts for a large part of the total resistance and changes in resistance in the lower airways would not be easily detected if total resistances were compared. It was found that old non-SPF animals had significantly higher pulmonary resistances than the SPF as well as the young non-SPF rats.