Correlation between lung structure and function in a canine model of emphysema

To correlate lung structure and function in an animal model of emphysema, 17 dog lungs were treated with intrabronchial instillation of papain (range of concentration 0.5-5%); the contralateral lungs served as controls. The lungs were inflated to the volume at a transpulmonary pressure (PL) of 25 cmH2O (V25), and static pressure-volume and maximal expiratory flow-volume curves were obtained. Eight pairs of lungs were processed for histology at a PL of 5 cmH2O, and eight pairs of lungs were processed at a PL of 25 cmH2O. Significant loss of elastic recoil was found in the papain-treated lungs, between 30 and 90% predicted V25 (P less than 0.02). However, there was no correlation between the mean linear intercept corrected to predicted lung volume (indicative of alveolar destruction) and loss of elastic recoil. There was a significant reduction of maximal flow (Vmax) between 20 and 90% predicted V25. However, the reduction in Vmax was commensurate with the reduction of elastic recoil, since there was no significant change in resistance of the upstream segment between 30 and 70% predicted V25. Airway morphometry demonstrated no significant differences in small airway dimensions between control and emphysema-treated lungs. In both control and papain-treated lungs, small airway dimensions changed relatively more than lung volume a PL of 25 and 5 cmH2O.