Intrapleural injection of elastase: a model for inducing subpleural emphysema?

Subpleural emphysema induction was attempted by injecting elastase intrapleurally into rats and cats. Microscopic evaluation of emphysema (alveolar dilation and septal rupture) was compared with a quantification of alveolar dilation (Fawell-Newman method). The emphysema found in animals treated with an intrapleural injection of porcine pancreatic elastase did not appear to be specifically located in a subpleural zone, and was identical to the focal emphysema induced by an enzyme instillation into the airways. It should be noted that a placebo instillation into the feline airways sometimes induced alveolar dilation without septal disruption presumably by causing bacterial contamination. Cats were seen to be very sensitive to pleural stress since this enzyme injection produced an alveolar dilation (increased mean intercept) as significant as that in cats treated by an intrabronchial instillation of elastase (P less than 0.001).