Disproportionate impairment in diffusing capacity predicts pulmonary hypertension with an elevated pulmonary vascular resistance in COPD.

Abstract

Current guidelines for the evaluation of chronic obstructive pulmonary disease (COPD) do not recommend screening for pulmonary hypertension (PH), despite the high prevalence and impact on outcomes. A simple screening tool to identify patients with an elevated pulmonary vascular resistance (PVR) is urgently needed, as they may benefit from PH-specific therapy and more urgent referral for lung transplantation. We sought to examine whether a ratio of forced expiratory volume in 1 s (FEV₁) to diffusing capacity (DLCO) predicts haemodynamic patterns in COPD. Individuals with COPD who underwent right heart catheterisation from two academic medical centres were included. Adjusted multinomial models tested associations between FEV₁/DLCO and haemodynamic patterns. Receiver operating curves were generated to assess the discriminative performance of the FEV₁/DLCO ratio in predicting PH with an elevated PVR. Approximately 40% of the 411 individuals included had PH with an elevated PVR. For every 0.1 increase in the FEV₁/DLCO ratio, there was a 12-14% increased rate of PH with an elevated PVR compared with No PH. FEV₁/DLCO ratio had moderate discriminative performance (C-statistic 0.68-0.72), which was strengthened when combined in a model with elevated tricuspid regurgitant jet velocity on echocardiography (C-statistic 0.78-0.82). Above a threshold of 1.4, FEV₁/DLCO demonstrated good specificity (75%) in predicting PH with an elevated PVR. These findings suggest that disproportionate reductions in DLCO predict PH with an elevated PVR in a COPD population. The FEV₁/DLCO ratio should be considered in the evaluation of PH in COPD.