Relation between preoperative inspiratory lung resistance and the outcome of lung-volume-reduction surgery for emphysema

Background: Surgery to reduce lung volume has recently been reintroduced to alleviate dyspnea and improve exercise tolerance in selected patients with emphysema. A reliable means of identifying patients who are likely to benefit from this surgery is needed. Methods: We measured lung resistance during inspiration, static recoil pressure at total lung capacity, static lung compliance, expiratory flow rates, and lung volumes in 29 patients with chronic obstructive lung disease before lung-volume-reduction surgery. The changes in the forced expiratory volume in one second (FEV₁) six months after surgery were related to the preoperatively determined physiologic measures. A response to surgery was defined as an increase in the FEV₁ of at least 0.2 liter and of at least 12 percent above base-line values. Results: Of the 29 patients, 23 had some improvement in FEV₁ including 15 who met the criteria for a response to surgery. Among the variables considered, only preoperative lung resistance during inspiration predicted changes in expiratory flow rates after surgery. Inspiratory lung resistance correlated significantly and inversely with improvement in FEV₁ after surgery (r = - 0.63, P<0.001). A preoperative criterion of an inspiratory resistance of 10 cm of water per liter per second had a sensitivity of 88 percent (14 of 16 patients) and a specificity of 92 percent (12 of 13 patients) in identifying patients who were likely to have a response to surgery. Conclusions: Preoperative lung resistance during inspiration appears to be a useful measure for selecting patients with emphysema for lung-volume-reduction surgery.