The resurgence of interest in lung-volume reduction surgery in patients with chronic obstructive pulmonary disease has been accompanied by a recognition of the importance of preventing postoperative air leaks. Various materials have been used to buttress the staple line in lung reduction surgery, including everted walls of bullae, fibrin glue, blood patches, and strips of bovine pericardium. We conducted an experimental study to assess the effectiveness in preventing air leaks of stapling alone as compared with stapling with one of three reinforcement materials: bovine pericardium,* expanded polytetrafluoroethylene (ePTFE) cardiovascular patch,† or a prototype ePTFE staple-line reinforcement material.‡ Freshly harvested pairs of normal lungs from 24 adult mongrel dogs (48 lungs) were used. The trachea was transected approximately 3 cm above the carina. A 7 mm endotracheal tube was inserted into the lung and secured with an umbilical tape. The endotracheal tube was then connected to a ventilator with a pressure gauge (Penlown, Ltd., Abingdon, United Kingdom). A surgical stapler (Ethicon GIA 55, Ethicon, Inc., Somerville, N.J.) was used to staple across the apex of each lung. In one lung of each pair (control), only staples were inserted. For the other lung in the pair, bovine pericardium, ePTFE cardiovascular patch material, or ePTFE prototype staple-line reinforcement material (eight lungs for each material) was attached to the stapler before firing and the staples were fired through the material, thereby creating a buttressed staple line that remained in the lung tissue. The stapler was removed and the entire lung preparation, including the junction of the endotracheal tube and trachea, was immersed in normal saline solution. Positive pressure was gradually increased until one or more bubbles were visible at the staple line. The pressure (centimeters of water) at which the first bubbles appeared was recorded. The results with respect to the pressure at which air leakage occurred in the control lungs as compared with the lungs in which the staple-line reinforcement materials were placed were statistically assessed with one-way analysis of variance and t tests. The pressure at which air bubbles were observed in the staple line varied considerably within the control group and each of the test groups. There were no significant differences among the three materials in the air-leakage pressure. However, for each of the three materials, the pressure at which leakage occurred was significantly higher (p 5 0.004) than that at which air From the Division of Cardiothoracic Surgery, University of Mississippi Medical Center, Jackson, Miss.