Desaturation during Six-Minute Walk Testing Predicts Major Morbidity Following Anatomic Lung Resection among Patients with COPD

Background: Pulmonary function testing (PFT) is commonly used to risk-stratify patients prior to lung resection. Guidelines recommend that patients with reduced lung function, due to chronic lung conditions such as Chronic Obstructive Pulmonary Disease (COPD), should receive additional physiologic testing to determine fitness for resection. We reviewed our experience with six-minute walk testing (SMWT) to determine the association of test results and post-operative complications. Methods: Consecutive adult patients undergoing segmentectomy, lobectomy, bilobectomy or pneumonectomy between 1 January, 2007 and 1 January, 2017 were identified in a prospectively maintained database. Patients with poor lung function, as defined by percent predicted forced expiratory volume in 1 s (FEV1) or diffusion capacity of carbon monoxide (DLCO) ≤60%, had results of SMWT extracted from their chart. Association of test result to post-operative events was performed. Results: 581 patients had anatomic lung resections with predicted post-operative FEV1 or DLCO values ≤60%, consistent with a diagnosis of COPD. Among them, 50 (8.6%) had preoperative SMWT performed. Patients who received SMWT were more likely to have a FEV1 or DLCO less than 40 percent predicted (24/50 (48.0%) vs 166/531 (31.3%), p = 0.016). Post-operatively, patients who had SMWT performed had higher rates of pneumonia, but similar rates of major morbidity. The post-exercise oxygen saturation and the amount of desaturation correlated with the occurrence of major morbidity. In multivariable regression, oxygen desaturation was an independent risk factor for the occurrence of major morbidity, and desaturation was an excellent predictor of major morbidity by receiver operating characteristic curves analsysis. Conclusions: Among patients with elevated risk, oxygen desaturation during SMWT was independently associated with the occurence of major morbidity in multivariable analysis, while pulmonary function testing was not. SMWT is an important tool for risk-stratification, and may be underutilized.