Clinical value of quantitative ventilation-perfusion lung scans in the surgical management of bronchogenic carcinoma.

Quantitative xenon 133 ventilation and technetium 99m macroaggregated albumin (MAA) perfusion scans were performed in 85 patients with lung cancer who had resection of their tumor. The contribution of the lung to be resected to the overall pulmonary function and, therefore, the expected reduction in postoperative pulmonary function was calculated by combining the results of spirometry with the quantitative measurement of differential perfusion and/or ventilation according to several equations. This was done in an effort to determine the best method of predicting postoperative pulmonary function. The predicted postoperative forced expiratory volumes in the first second (FEV1) from each of these calculations were compared to the observed postoperative FEV1 in 37 patients, 23 of whom had a pneumonectomy and 14, a lobectomy. FEV1 after pneumonectomy was predicted as accurately from the perfusion scan (mean percent error = 11% ± 10) as from the ventilation scan (mean percent error = 14% ± 11%). FEV1 after lobectomy could be predicted with a mean percent error of less than 10%. Because of these findings, all patients requiring lung resection had their postoperative FEV1 predicted from the perfusion scan. Patients with a calculated postoperative FEV1 of less than 1.0 L were considered medically inoperable. There were three deaths, one of which was related to pulmonary insufficiency, among 45 patients who underwent pneumonectomy with a predicted postoperative FEV1 of greater than 1.0 L. Twenty-two of these patients had a preoperative FEV1 of less than 2.0 L and would have not been considered candidates for pneumonectomy if preoperative function of each lung had been assumed to be equal. There were no surgically related deaths or cases of postoperative respiratory insufficiency among these patients. Forty patients, seven of them with a preoperative FEV1 of less than 1.5 L, underwent lobectomy, with no deaths or cases of postoperative respiratory insufficiency.