Background: Lung volume reduction surgery may be a viable treatment alternative for emphysema patients suffering from severe respiratory insufficiency. Objectives: To evaluate functional and morphological aspects of emphysematous rat lungs, prior to and following lung volume reduction surgery. Method: Wistar rats were divided into two experimental groups (papain without surgery and papain with surgery) and three control groups (saline without surgery, saline with surgery and papain without mechanical ventilation). After approximately 40 days of endotracheal instillation of papain or saline solution, animals in the papain with surgery and saline with surgery groups were submitted to bilobectomy of the middle lobes by right thoracotomy along the posterior border of the superior vena cava. After 1 week, the same animals were submitted to a mechanical ventilation study, which involved measurement of lung elasticity and airway resistance. For all of the animals studied, lung tissue was analyzed in order to determine alveolar diameter and the elastic fiber quantity. Results: Morphometric analysis revealed higher mean alveolar diameter in the lungs of all animals exposed to papain as compared to those exposed to saline. Elastic fiber counts in the alveolar septa of animals treated with papain were lower than those of animals receiving saline. In the animals submitted to bilobectomy and papain, lung elasticity was greater than in those receiving papain without surgery and was statistically equal to that seen in animals receiving saline (with or without surgery). Conclusion: In the respiratory systems of animals with pulmonary emphysema submitted to lung volume reduction by bilobectomy, the capacity for elastic recoil returned to values equivalent to those of the control group animals.

Keywords: Key words: Pulmonary emphysema. Papain/drugs efects. Case-control studies. Disease models, animal. Respiratory mechanics/drugs efects. Lung/sugery. Lung/anatomy & histology.