A six-month study of the evolution of papain-induced emphysema in the dog.

The development of papain-induced emphysema and the effect of structural changes of the lung on pulmonary hemodynamics were investigated in the dog in a 6-month study. Papain was administered as an aerosol at the beginning of the study and at Day 21; control animals received saline. At 3 or at 6 months, hemodynamic investigations were carried out in the awake animal (sedated with piritramide). The dogs were then killed and the lungs processed for morphometric evaluation. Arterial blood gases were analyzed at regular intervals for the duration of the study. In the papain-treated dogs, mean linear intercept (Lm) and internal surface area of the lungs corrected to an arbitrary lung volume of 2L (ISA2) were significantly different from control dogs both at 3 and at 6 months. No progression of the structural changes of the lung occurred between these two time intervals. Arterial blood oxygenation was normal throughout the study. In the papain-treated group at 6, but not at 3, months, mean pulmonary arterial blood pressure (PAPm) and pulmonary arteriolar resistance (PAR) were significantly augmented when compared with the control group. A significant correlation was found at 6 months between the Lm and ISA2 on one side, and PAPm and PAR on the other side, suggesting that the structural changes of the lung were responsible for pulmonary hemodynamic alterations.