Correlation of Physiological and Radiological Characteristics in Chronic Obstructive Pulmonary Disease

Background. Diagnosis of chronic obstructive pulmonary disease (COPD) is confirmed on spirometry but the diagnosis of emphysema remains problematic. The objective of this study was to evaluate the utility of chest radiograph (CXR) and computed tomography (CT) for the diagnosis of emphysema and to correlate these findings with pulmonary function tests (PFTs). Methods. Thirty-five patients with COPD were studied. In all of them, CXR, CT and PFTs were done; three patients had bronchiectasis on CT and were excluded from the study. Chest radiographs (CXRs) were scored for signs of hyperinflation. Lung densities were measured on CT. Results. Functional indices of hyperinflation, i.e. functional residual capacity (FRC), residual volume (RV) and RV/total lung capacity (TLC) had significant correlation with CXR scores. The mean retrosternal space (RSP) measurement was 2.63±0.6 cm (range 1.2 to 3.6cm). Mean lung density (MLD) was -867.91 Hounsfield units (HU) which significantly correlated with functional indices of hyperinflation (FRC, RV, TLC, RV/TLC). Conclusions. In Indian population hyperinflation was found to occur even with lesser values of RSP than the western criteria. CT lung density gives good radiological evidence of emphysema and correlates with lung function abnormalities. [Indian J Chest Dis Allied Sci 2012;54:235-242]