Severity-related differences in lung attenuation in men with COPD

Abstract

Background and objectives: We compare the inspiratory and expiratory regional lung densities between different levels of COPD severity (as assessed by the GOLD scale and by the BODE index), and to assess the relationship between regional lung densities and functional lung parameters.

Patients and methods: Fifty-five stable moderate-severe COPD men were selected. Functional evaluation included dyspnoea scale, blood gases, spirometry, plethysmography, diffusing capacity and six-minute walk test. Severity was classified according the GOLD scale and the BODE index. High resolution computed tomography (HRCT) scans of the entire lung at full inspiration and two sections at full expiration were obtained. Densitometry software was used to calculate the densities of the lung areas.

Results: Inspiratory and expiratory mean lung densities (MLD) of the lower lobes were significantly lower in very severe and severe COPD patients than in moderate patients. In contrast, we only found differences between the upper lobe MLD values of moderate and severe COPD patients. Inspiratory and expiratory HRCT densities were similar among all BODE quartiles, for both the upper and lower lobes. In a multiple regression analysis, airway obstruction parameters were mainly related to the expiratory MLD of the lower lobes, whereas lung hyperinflation parameters were predicted by the inspiratory MLD of the lower lobes. Lastly, diffusion capacity was independently related to the expiratory/inspiratory MLD of the lower lobes and to the inspiratory MLD of the upper lobes.

Conclusions: There are differences in lung attenuation measurements by HRCT between the varying levels of COPD severity as assessed by the GOLD scale.