Radiological findings, pulmonary function and dyspnea in underground coal miners.

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 (DL,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 DL,CO (rs=-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 (rs=-0.37; p<0.001). Dyspnea was best approximated by DL,CO (r=-0.312; p=0.008).

Conclusion: The clinical grade of breathlessness was best approximated by DL,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.