Radiological Findings, Pulmonary Function and Dyspnea in Underground Coal Miners

Abstract

Background: Respiratory disability induced by dust exposure in coal workers is assessed by pulmonary function tests and radiological evidence of pneumoconiosis. High-resolution computed tomography (HR-CT) improves the visibility of tissue changes, but the value of the findings for the clinical evaluation is controversial. Objectives: It was the aim of this study to evaluate the correlation between the International Labour Office (ILO) classification and the degree of emphysema in HR-CT with self-reported dyspnea and pulmonary function tests including diffusion capacity for CO (D_L,CO). Methods: We investigated 87 coal miners (aged 67 ± 6 years), having worked underground for 26 ± 9 years, with pulmonary function tests and HR-CT. Univariate associations were tested with correlation coefficients, and multivariable analyses used a stepwise forward regression model. Results: No aspect of the ILO classification showed a univariate correlation with dyspnea or forced expiratory flow in 1 s (FEV₁). Emphysema CT score was strongly associated with D_L,CO (r_s = –0.40; p < 0.001) and FEV₁/maximal vital capacity (r = –0.38; p < 0.001) in univariate analysis, but not with the clinical grade of dyspnea (r = –0.14; p = 0.256). CT emphysema score but not ILO classification was associated with FEV₁ in multivariable analyses (r_s = –0.37; p < 0.001). Dyspnea was best approximated by D_L,CO (r = –0.312; p = 0.008). Conclusion: The clinical grade of breathlessness was best approximated by D_L,CO. HR-CT showed a good association with expiratory flow limitation. ILO classification of the chest radiograph may be a marker of exposure but conveys little information about the degree of respiratory impairment.