Relationships between emphysema and airways metrics at High-Resolution Computed Tomography (HRCT) and ventilatory response to exercise in mild to moderate COPD patients

Background and purpose: In Chronic Obstructive Pulmonary Disease (COPD) patients, the opportunity to carry out a thoracic high-resolution CT (HRCT) scan and to perform an incremental cardiopulmonary exercise test (CPET) increases the possibility to identify the different clinical features of disease. The aim of our study was to evaluate the relationships between HRCT metrics (on emphysema by low attenuation areas-LAA% and airways by wall area-WA%) and CPET variables related to the dynamic response to exercise in terms of elastic balance (Delta rest-to-peak IC/TLC) and ventilation capacity for carbon dioxide output (V-E/V-CO2 slope and V-E/V-CO2 intercept). Methods: We prospectively enrolled COPD outpatients from the University Hospital of Parma. Data on anthropometrics characteristics, lung function, HRCT (LAA% and WA%) and CPET (Delta rest-to-peak IC/TLC, V-E/V-CO2 slope and V-E/V-CO2 intercept) were recorded. Results: Fifty-one mild to moderate COPD patients (66% males; median age 70 y; mean FEV1 56% of pred.) were enrolled in the study. LAA% demonstrated a significant correlation with Delta rest-to-peak IC/TLC and V-E/V-CO2 slope (r = 0.405, p = 0.005 and r = 0.453, p = 0.001, respectively), while WA% with V-E/V-CO2 slope (r = -0.333, p = 0.020). In multivariate regression models, after adjustment for oxygen uptake (peak V-O2) and physical capacity (peak workload), LAA was the only independent predictor of Delta rest-to-peak IC/TLC (beta 0.774, SE 0.334, p = 0.025) and V-E/V-CO2 slope (beta 0.155, SE 0.053, p = 0.005 and beta 0.305, SE 0.123, p = 0.018, respectively). V-E/V-CO2 intercept was instead predicted from FEV1 only (beta -0.097, SE 0.042, p = 0.027). Conclusion: In mild to moderate COPD patients, emphysema (LAA) and airways metrics (WA) have close relationships with the different characteristics of ventilatory response to exercise. In particular, we were able to show that LAA is an independent predictor of exercise-induced D rest-to-peak IC/TLC and V-E/V-CO2 slope. (C) 2016 Elsevier Ltd. All rights reserved.