A method for predicting postoperative lung function and its relation to postoperative complications in patients with lung cancer.

We predicted the postoperative forced expiratory volume in 1 second (FEV1) with a formula based on the premise that the total number of subsegments was 42: postop FEV1 = [1 - (b - n)/(42 - n)] (preop FEV1), where n and b are the number of obstructed subsegments and total subsegments, respectively, in the resected lobe. It was assumed that b was 6, 4, and 12 in the right upper, middle, and lower lobes, respectively, and 10 each in the left upper and the left lower lobes. The obstructed subsegments, n, were obtained from the findings on bronchography or bronchofiberscopy or both before operation. The linear regression line derived from the correlation between predicted (x) and measured (y) FEV1 was y = 0.850x + 0.286 +/- 0.296 (standard error) (N = 52; r = 0.821; p less than 0.001). We calculated the predicted postoperative FEV1 in 188 patients with primary lung cancer. The predicted values were corrected with the regression equation just mentioned and then normalized by the patient's height and sex (%FEV1(p,c). The correlation between %FEV1(p,c) and the surgical risk was studied. Postoperative respiratory complications were inversely related to %FEV1(p,c), and a significantly high incidence of complications (p less than 0.05) was observed in those whose %FEV1(p,c) was less than 60% of predicted normal. In aged patients (65 years old or more) without complications, %FEV1(p,c) was 67.3 +/- 18.0%; it was 52.2 +/- 12.8% in those with respiratory trouble and 53.3% +/- 9.6% in those with circulatory complications. The difference between groups with and without complications was significant (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)