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.

We studied 20 patient s 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.

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).

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.