Diaphragm dome height on chest radiography as a predictor of dynamic lung hyperinflation in COPD

Abstract

Background and objectiveDynamic lung hyperinflation (DLH) can play a central role in exertional dyspnoea in patients with chronic obstructive pulmonary disease (COPD). Chest X-ray is the basic tool for assessing static lung hyperinflation in COPD. However, the predictive capacity of DLH using chest X-ray remains unknown. This study was conducted to determine whether DLH can be predicted by measuring the height of the right diaphragm (dome height) on chest X-ray.MethodsThis single-centre, retrospective cohort study included patients with stable COPD with pulmonary function test, cardiopulmonary exercise test, constant load test, and pulmonary images. They were divided into two groups according to the median of changes of inspiratory capacity (ΔIC=IC lowest − IC at rest). The right diaphragm dome height and lung height were measured on plain chest X-ray.ResultsOf the 48 patients included, 24 were classified as having high DLH (ΔIC≤−0.59 L from rest; −0.59 L, median of all) and 24 as having low DLH. Dome height correlated with ΔIC (r=0.66, p<0.001). Multivariate analysis revealed that dome height was associated with high DLH independent of %low attenuation area on chest computed tomography and %FEV1. Furthermore, the area under the receiver operating characteristic curve of dome height to predict high DLH was 0.86, with sensitivity and specificity of 83% and 75%, respectively, at a cutoff of 20.5 mm. Lung height was unrelated to ΔIC.ConclusionDiaphragm dome height on chest X-ray may adequately predict high DLH in patients with COPD.