Radiological findings, pulmonary function and dyspnea in underground coal miners

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.

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).

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.

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).

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.