Experimental papain-induced emphysema in dogs.

Papain was injected intratracheally into 8 dogs after measurements had been made of oxygen tension, carbon dioxide tension and pH of arterial blood, subdivisions of lung volume, steady state diffusing capacity for carbon monoxide, fractional uptake of carbon monoxide, static pressurevolume curves, and pulmonary resistance at different lung volumes, and measurements were repeated one to four weeks later. There were no significant changes in arterial blood gas tensions, acid-base balance, or pulmonary resistance, but the diffusing capacity decreased. Total lung capacity, functional residual capacity, and residual volume increased; elastic recoil decreased. Pulmonary resistance was partitioned when the dog was sacrificed; the resistance of airways smaller than 2 mm in diameter was increased whereas that of larger airways was decreased. Trivial to moderate panlobular emphysema was found in all animals on pathologic examination. Internal surface area was reduced, particularly when it was assessed at a standard...