Improvement in pulmonary function and elastic recoil after lung-reduction surgery for diffuse emphysema

Background. Pulmonary function may improve after surgical resection of the most severely affected lung tissue (lung-reduction surgery) in patients with diffuse emphysema. The basic mechanisms responsible for the improvement, however, are not known. Methods. We studied 20 patients with diffuse emphysema before and at least three months after either a unilateral or a bilateral lung-reduction procedure. Clinical benefit was assessed by measurement of the six-minute walking distance and the transitional-dyspnea index, which is a subjective rating of the change from base line in functional impairment and the threshold for effort- and task-dependent dyspnea. Pressure-volume relations in the lungs were measured with static expiratory esophageal-balloon techniques, and right ventricular systolic function was assessed by echocardiography. Results. The patients had significant improvement in the transitional-dyspnea index after surgery (P<0.001). The mean (±SD) coefficient of retraction, an indicator of elastic recoil of the lung, improved (from 1.3±0.6 cm of water per liter before surgery to 1.8±0.8 after, P<0.001). Sixteen patients with increased elastic recoil had a greater increase in the distance walked in six minutes than the other four patients, in whom recoil did not increase (P=0.02). The improved lung recoil led to disproportionate decreases in residual volume as compared with total lung capacity (16 percent vs. 6 percent), but the decreases in both values were significant (P<0.001). Forced expiratory volume in one second increased (from 0.87±0.36 to 1.11±0.45 liters, P<0.001). End- expiratory esophageal pressure also decreased (P=0.002). These improvements in lung mechanics led to a decrease in the partial pressure of arterial carbon dioxide from 42±6 to 38±5 mm Hg (P=0.006). Furthermore, the fractional change in right ventricular area, an indicator of systolic function, increased from 0.33±0.11 to 0.38±0.10 (P=0.02). Conclusions. Lung-reduction surgery can increase the elastic recoil of the lung in patients with diffuse emphysema, leading to short-term improvement in dyspnea and exercise tolerance.