The FEV1/DLCO Ratio as an Effective Predictor of Severity and Survival in COPD-Associated Pulmonary Hypertension: A Retrospective Analysis

Abstract

Background/Objectives: Pulmonary hypertension (PH) is associated with increased morbidity and mortality in chronic obstructive pulmonary disease (COPD). The ratio of the functional vital capacity (FVC) to diffusing capacity of the lung for carbon monoxide (DLCO) has demonstrated predictive and prognostic efficacy in PH due to lung disease, including COPD. However, forced expiratory volume in 1 s (FEV1) is used to grade COPD severity. We aimed to determine whether FEV1/DLCO predicts PH severity in COPD-PH. Methods: This is a retrospective analysis of patients with COPD-PH diagnosed via right heart catheterization and pulmonary function testing. Linear regression assessed the correlation of FEV1/DLCO with RHC parameters. Receiver operating characteristic (ROC) analysis was performed to assess the predictive effectiveness of FEV1/DLCO for severe PH. Results: Among 212 patients with COPD-PH, the FEV1/DLCO ratio positively correlated with mean pulmonary artery pressure (mPAP; r = 0.6, p < 0.001) and pulmonary vascular resistance (PVR; r = 0.56, p < 0.001). In ROC analysis, FEV1/DLCO was effective at predicting severe PH (AUC 0.60, p = 0.02). Those with a FEV1/DLCO ratio > 1.66 had a decreased rate of transplant-free survival as compared to those with a lower ratio (40.8% vs. 59.2%, p = 0.01). Conclusions: Among patients with COPD-PH, FEV1/DLCO correlates well with mPAP and PVR. The FEV1/DLCO ratio may effectively predict severe PH and may predict transplant-free survival in COPD-PH.