Spirometry: predicting risk and outcome

Predicted postoperative FEV1 is certainly the most widely used parameter in preoperative risk stratification [54] and the measure recommend by BTS and ACCP functional guidelines as a first step in the screening of patients for lung resection surgery. Nevertheless, recent evidences have demonstrated that ppoFEV1 is not a reliable predictor of postoperative cardiopulmonary complications in patients with preoperative impaired pulmonary function. This may be because of the fact that the resection of a portion of lung in patients with obstructive disease determines only a minimal loss, or even an improvement, in overall respiratory function and exercise tolerance. This lung volume reduction effect takes place very early, since the first postoperative days, balancing what ever negative physiologic effects a thoracotomy and lung resection may entail. In addition to its poor predictive role in COPD patients, ppoFEV1 largely underestimate the actual loss in the very first days after operation, when most of the complications develop. The rationale to use a parameter which is poorly correlated with the pulmonary function at the moment the complications occur seems unwarranted. At the very best, ppoFEV1 appears a weak surrogate of the immediate postoperative FEV1. The FEV1 measured on the first postoperative day may be 30% less than predicted. Corrective equations have been published to correct this discrepancy with the aim to improve risk stratification.