MAXIMAL EXPIRATORY FLOWS IN COAL-MINERS

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Abstract
From a group of approximately 9000 working coal miners studied by the U. S. Public Health Service in 1973 and 1974, 4 groups of 428 age- and height-matched subjects were selected according to their smoking habits and whether or not they had bronchitis. Flow-volume curves, lung volumes and the more commonly used indices of ventilatory capacity, the forced vital capacity and the forced expiratory volume in 1 s, had been measured previously in each subject. A larger total lung capacity was observed in smoking than in nonsmoking miners, whether bronchitic or not. This phenomenon is believed to indicate a loss of retractive forces due to destruction of the lung parenchyma associated with cigarette smoking. No comparable change in total lung capacity was observed in the nonsmoking miners with bronchitis. Because dust-induced bronchitis in nonsmoking miners is associated with a decrease in flows at high lung volumes in the absence of an increase in total lung capacity, it is inferred that industrial bronchitis leads to large airway obstruction but not emphysema. It was also apparent that flows, when expressed as percentages of forced vital capacity exhaled, offered little or no advantage over the 1 s forced expiratory volume or the ratio of the 1 s forced expiratory volume to vital capacity as an index of ventilatory capacity, except that peak flow and the flows at higher lung volumes were sometimes helpful in differentiating bronchitic from nonbronchitic subjects. In longitudinal studies, however, the flow-volume curve when related to absolute lung volumes may have advantages over the conventional time vs. volume tracing.

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