Pulmonary Emphysema Regional Distribution and Extent from Chest Computed Tomography is Associated with Pulmonary Function Impairment in COPD Patients.

Abstract

Objective: To evaluate if emphysema regional distribution and extension automatically quantified from chest computed tomography (CT) is associated with lung function impairment and clinical severity in patients with cronic obstructive pulmonary disease (COPD). Methods/Design: Patients with a post-bronchodilator FEV1/FVC < 0.70, without any other obstructive airway disease, that present radiological evidence of emphysema on visual CT inspection were retrospectively enrolled. A QUAntitative Lung Imaging (QUALI) system automatically assessed the regional distribution and quantified the extent of pulmonary emphysema (paraseptal, centrilobular and panlobular), adjusting to measured or predicted lung volume, based on an artificial neural network trained for this purpose. The association between emphysema extension and regional distribution, by dividing right and left lungs in three thirds each, and pulmonary function impairment and clinical severity was then assessed. Results: 86 patients fulfilled the inclusion criteria. Their median age was 69 years, most of them were male (88.4%). An increased residual volume (RV, 179.8±59% of predicted) and a total lung capacity (TLC, 120.3±23%) suggested moderate to severe pulmonary hyperinflation. Emphysema extent adjusted to the CT measured lung volume was significantly lower than when adjusted to the predicted lung volume (PLV) (p<0.001). Emphysema extent adjusted to the PLV presented strong correlations with TLC (r = 0,60), RV (r = 0,66) and FEV1 (r = 0,60) and moderate correlation with DLCO (r = 0,58). Emphysema areas in basal and midle thirds of both lungs seem to have strong or moderate correlations with pulmonary function tests variables. Patients with at least 5% of emphysema in 5 or 6 thirds of both lungs had a significantly decline in FEV1 (p < 0.001), DLCO (p < 0.001) and a significant increase in RV (p < 0.001) and TLC (p < 0.001). Conclusions: Automatic quantification of emphysema extension and regional distribution adjusted to the PLV, but not to measured lung volume, has a strong correlation with pulmonary function tests parameters. The presence of emphysema in the middle and lower thirds of the lung seem to play a major role in lung function decline.