AN ANIMAL-MODEL FOR LUNG-VOLUME REDUCTION THERAPY OF PULMONARY-EMPHYSEMA

Stapled lung volume reduction surgery (LVRS) has recently been describ ed for treatment of emphysema. Many questions arise regarding physiolo gic mechanisms of response from surgical treatment of emphysema. The o bjective of this study was to develop an animal model for the study of lung volume reduction surgery in diffuse heterogeneous emphysema. We hypothesized that elastic recoil would increase, static respiratory sy stem compliance would decrease, and expiratory flows would increase af ter lung volume reduction surgery in animals with emphysema. In the st udy, emphysema was induced in 31 New Zealand White rabbits (3-5 kg) wi th endotracheally aerosalized porcine elastase (10,000-12,000 U). Late ral thoracotomies were performed 4-6 weeks postinduction under general anesthesia and mechanical ventilatory support. Stapled volume reducti on was performed on the right lower lobe using a standard multirow ped iatric stapler (U.S. Surgical). Pulmonary function tests were performe d at baseline (preinduction), before stapling LVRS (postemphysema indu ction), immediately post stapling LVRS, and 1 week poststapling. Stati c respiratory system compliance, flow, conductance and forced expirato ry flows, and peak flows at 20 and 40 cm(3) of exhaled volume were ana lyzed. Animals were sacrificed 1 week poststapling, and bilateral lung s were harvested for histopathology. Diffuse but heterogeneous pulmona ry emphysema was seen in these animals treated with high-dose aerosoli zed elastase. Static compliance increased, while expiratory flows and conductance decreased after induction of emphysema. Immediately post s tapled volume reduction therapy, animals had decreased static complian ce. By 1 week following surgery, animals showed increased forced expir atory flows and decreased expiratory resistance, although compliance w as similar to preoperative levels. In conclusion, we describe initial results in an animal model of obstructive emphysema suitable for the s tudy of lung volume reduction surgery. Changes in pulmonary function i ndicate that unilateral lower lobe LVRS increases airway conductance i n the rabbits. Findings from LVRS studies in animal models such as thi s may help explain clinical improvement following LVRS in humans.