Different diffusing capacity of the lung for carbon monoxide as predictors of respiratory morbidity

The percent predicted diffusing capacity of the lung for carbon monoxide (Dlco%) is an important pulmonary function test (PFT) obtained before elective pulmonary resection. However, there are several Dlco values reported and it is unknown which ones are important predictors of postoperative morbidity.

This is a retrospective study of a prospective database of patients who underwent PFTs and pulmonary resection by one surgeon. The PFTs evaluated were as follows: forced expiratory volume in one second (FEV(1)%), minute ventilation volume (MVV%), and three types of diffusion capacity of the lung for carbon monoxide values: the diffusion capacity of the lung for carbon monoxide (Dlco%), the Dlco adjusted for hemoglobin (DL adjusted%), and the Dlco adjusted for alveolar volume (Dlco/VA%).

There were 906 patients between January 2005 and December 2007, and lobectomy was performed most commonly. Complications occurred in 254 patients (28%) and were respiratory in 115 (13%). On univariate analysis, age (p < 0.001), number of cigarettes smoked (p = 0.008), history of coronary artery disease (p = 0.028), FEV(1)% (p = 0.021), postoperative predicted (ppo) FEV1% (p < 0.001), Dlco% (p = 0.018), ppoDlco% (p = 0.002), and Dlco/VA% (p = 0.004) were significantly different among those who did and did not experience postoperative respiratory morbidity. Multivariate regression analysis identified ppoDlco%, ppoFEV1%, Dlco/VA%, and age as significant independent predictors of respiratory morbidity. Operative mortality was 2% (18 patients).

Although age, FEV(1)%, ppoFEV(1)%, Dlco%, and ppoDlco% are all well-known predictors of operative morbidity after elective pulmonary resection, the Dlco/VA% is another important predictor. This information should be included to help guide patient selection for pulmonary resection and to determine preoperative risk stratification.