ABSTRACT
OBJECTIVE: To assess the added value of pulmonary function tests (PFTs) and different classifications of chronic obstructive pulmonary disease (COPD) to the Society of Thoracic Surgeons (STS) risk model using a clinical definition of lung disease for predicting outcomes after cardiothoracic (CT) surgery. METHODS: We evaluated consecutive patients who underwent nonemergency cardiac surgery and underwent PFTs before CT surgery. We used the STS risk model 2.73 to estimate the postoperative risk for respiratory failure (RF; defined as the need for mechanical ventilation for ≥72 hours, or reintubation), prolonged postoperative stay (PPLS; defined as >14 days), and 30-day all-cause mortality. We plotted the receiver operating characteristics curve for STS score for each adverse event, and compared the resulting area under the curve (AUC) with the AUC after adding PFT parameters and COPD classifications. RESULTS: Of the 1412 patients with a calculated STS score, 751 underwent PFTs. The AUC of the STS score was 0.65 (95% confidence interval [CI], 0.55-0.74) for RF, 0.67 (95% CI, 0.6-0.74) for prolonged postoperative length of stay (PPLS), and 0.74 (95% CI, 0.6-0.87) for death. None of the PFT parameters or COPD classifications added to the predictive ability of STS for RF, PPLS, or 30-day mortality. CONCLUSIONS: Adding individual PFT parameters or different COPD classifications to STS score calculated using clinically based classification of lung disease did not improve model discrimination. Thus, routine preoperative PFTS may have limited clinical utility in patients undergoing CT surgery when the STS score is readily available.
