Relative contributions of emphysema and airway remodelling to airflow limitation in COPD : Consistent results from two cohorts

Background and objective The relative contributions of emphysema and airway remodelling to airflow limitation remain unclear in chronic obstructive pulmonary disease ( COPD ). We aimed to evaluate the relative contributions of emphysema and airway wall thickness measured by quantitative computed tomography ( CT ) to the prediction of airflow limitation in two separate COPD cohorts. Methods Pulmonary function tests and whole‐lung CT were performed in 250 male smokers with COPD , including 167 from U niversity M edical C enter at H o C hi M inh C ity, V ietnam, and 83 from S higa U niversity of M edical Science H ospital, J apan. The same CT analysis software was used to measure the percentage of low attenuation volume (% LAV ) at the threshold of −950 H ounsfield units and the square root of wall area of a hypothetical airway with an internal perimeter of 10 mm ( Pi 10). The standardized coefficients in multiple linear regressions were used to evaluate the relative contributions of % LAV and Pi 10 to predictions of FEV 1 / FVC and FEV 1 % predicted. Results Both % LAV and Pi 10 independently predicted either forced expiratory volume in 1 s/forced vital capacity ( FEV 1 / FVC ) or FEV 1 % predicted ( P  ≤ 0.001 for all standardized coefficients). However, the absolute values of the standardized coefficients were 2−3 times higher for % LAV than for Pi 10 in all prediction models. The results were consistent in the two COPD cohorts.Conclusions % LAV predicts both FEV 1 / FVC and FEV 1 better than Pi 10 in patients with COPD . Thus, emphysema may make a greater contribution to airflow limitation than airway remodelling in COPD .