Lung mechanics in relation to radiographic category of coalworkers' simple pneumoconiosis

Abstract

ABSTRACT The maximal expiratory flow/static transpulmonary pressure relationship and the maximal expiratory flow response to breathing oxyhelium were used to distinguish between loss of elastic recoil and narrowing of small airways in 36 lifelong non-smoking non-bronchitic South Wales coalminers. On average the miners showed significantly (p < 0·05) reduced lung elastic recoil when compared with 10 healthy similarly aged non-miners. The mean forced expiratory volume in one second and the forced expiratory flow response to oxyhelium at 50% of the vital capacity were significantly (p < 0·05) lower in 12 miners with radiographic categories 2 or 3 when compared with 24 similarly aged miners with radiographic categories 0 or 1. The miners with categories 2 or 3 coalworkers' simple pneumoconiosis (CWP) had worked underground for 10 years longer, and their mean residual volume, residual volume/total lung capacity ratio, volume of isoflow and critical transmural pressure were significantly higher (p < 0·05). The results indicate that in the prodromal and early stages of simple CWP (categories 0 and 1), the dominant pathophysiological abnormality is loss of elastic recoil suggesting the presence of “focal emphysema.” As simple CWP progresses to categories 2 and 3, the loss of recoil is maintained, and the small airways become narrower. These findings are consistent with the hypothesis that progression of simple CWP is associated with the development of both centrilobular emphysema and intrinsic narrowing of small airways.