Effect of papain-induced emphysema on the distrubtion of pleural surface pressure.

Distribution of transpulmonary pressure (Ptp) at FRC, during spontaneous breathing, and during inflation of the relaxed respiratory system was studied in the supine, lateral and head-up postures after papain had been injected intratracheally into dogs. Functional and morphological changes of the lung resembling those of panlobular emphysema occurred in papain-treated dogs. In all postures the relationship between lung height and Ptp at FRC was steeper and shifted to the left of that obtaining for normal dogs. During artifical inflation changes of Ptp were larger in the dependent than in the upper lung and the vertical gradient of Ptp eventually disappeared, as observed in normal dogs. During spontaneous breathing changes of Ptp were uniform in the horizontal postures, but larger over the upper regions in the head-up posture; whereas they are uniform in all postures in normal dogs. From local Ptp values and lung P-V curve, distribution of specific lung volumes at FRC and ventilation during spontaneous breathing were assessed for both normal and papain-treated head-up dogs: the results agreed with those obtained using radioactive gases in normal and in elderly man or emphysematous subjects with no apparently localized lesions.