Characteristics of COPD phenotypes classified according to the findings of HRCT and spirometric indices and its correlation to clinical characteristics

Introduction: In recent years, there has been increasing interest in diagnosing various components of chronic obstructive pulmonary disease (COPD) using high-resolution computed tomography (HRCT). The present study was undertaken to evaluate HRCT features in patients with COPD.
Materials and methods: Fifty patients of COPD (confirmed on Spirometry as per the GOLD guidelines 2014 guidelines) were enrolled, out of which 35 patients got a HRCT done. The Philips computer program for lung densitometry was used with these limits (-800/-1, 024 Hounsfield unit [HU]) to calculate densities, after validating densitometry values with phantoms. We established the area with a free hand drawing of the region of interest, then we established limits (in HUs) and the computer program calculated the attenuation as mean lung density (MLD) of the lower and upper lobes.
Results: There was a significant correlation between smoking index and anteroposterior tracheal diameter (P = 0.036). Tracheal index was found to be decreasing with increasing disease severity which was statistically significant (P = 0.037). A mild linear correlation of pre-forced expiratory volume in the first second (FEV1) was observed with lower lobe and total average MLD while a mild linear correlation of post-FEV1 was observed with both coronal (P = 0.042) and sagittal (P = 0.001) lower lobes MLD. In addition, there was a linear correlation between both pre (P = 0.050) and post (P = 0.024) FEV1/forced vital capacity with sagittal lower lobe MLD.
Conclusion: HRCT may be an important additional tool in the holistic evaluation of COPD.

Keywords
Chronic obstructive pulmonary disease; high resolution computed tomography; spirometry.