Respiratory function in southern Appalachian coal miners

Shape of small opacities and lung function in coalworkers

Lung function and chest radiographs were reviewed in 357 coalworkers who had been referred from the Cardiff Pneumoconiosis Medical Panel. The chest films were read according to the 1980 ILO classification of radiographs by three experienced readers. An irregularity score, reflecting the shape of the small opacities, was derived from the readings and compared with the lung function variables. Men with higher irregularity scores had significant reductions in ventilatory capacity and gas transfer factor, with no change in total lung capacity, after age, height, profusion of small opacities, and smoking habit had been taken into account. The effects were present both in those with and in those without large opacities. The agreement between readers over the shape of opacities was almost as good as for their profusion. Men with rounded opacities had a lower gas transfer factor if they were predominantly of the "p" type. The results are consistent with those for a combination of emphysema and interstitial fibrosis, which has been found in coalworkers with irregular opacities.

Fractional carbon monoxide uptake in an employed population

Stebbings, J. H. (1974).Thorax, 29, 505-510. Fractional carbon monoxide uptake in an employed population. The fractional carbon monoxide uptake in 913 New York City transit workers was studied. A prediction equation for white males, based on nonsmokers, was obtained: fractional CO uptake = 0·58032 − 0·00204 × age + 0·0004 × weight (kilograms). Weight was the index of body size most strongly correlated with the fractional CO uptake. Decline in function with age by amount of tobacco smoked is described. A correction factor for respiration, based on results from 581 workers with two or more tests, was calculated: − 0·123654 × (standard tidal volume − observed tidal volume). Tidal volume was the most important contributor to individual variability of the fractional CO uptake, and minute volume or respiration rate do not add significantly to it. For epidemiological or screening uses, prediction equations are given for the fractional CO uptake corrected to 0·5 1. tidal volume. Respiration variables explain only 1·5% of individual variability, and individual variability over a mean period of 16·6 months was much larger (an individual standard error of 0·07) than the unexplained population variability (a population standard error of 0·01−0·02); thus the usefulness of the fractional CO uptake as a test of respiratory function is in doubt.

Lung mechanics and frequency dependence of compliance in coal miners

The mechanical properties of the lungs were studied in two groups of coal miners. The first group consisted of miners with either simple or no pneumoconiosis and was divided into two subgroups (1A and 1B). The former (1A) consisted of 62 miners most of whom had simple pneumoconiosis but a few of whom had clear films. Although their spirometry was normal, all claimed to have respiratory symptoms. The other subgroup (1B) consisted of 25 working miners with definite radiographic evidence of simple pneumoconiosis but normal spirometric findings. The second major group consisted of 25 men with complicated pneumoconiosis. In subjects with simple pneumoconiosis, static compliance was mostly in the normal range, whereas it was often reduced in subjects with the complicated disease. The coefficient of retraction was normal or reduced in most subjects except those with advanced complicated disease, in several of whom it was elevated. So far as simple pneumoconiosis was concerned, abnormalities, when present, reflected "emphysema" rather than fibrosis. In severe complicated pneumoconiosis, changes suggesting fibrosis tended to predominate. In the 25 working miners (subgroup 1B) dynamic compliance was measured at different respiratory rates. 17 of the subjects in this subgroup demonstrated frequency dependence of their compliance, a finding unrelated to bronchitis and suggestive of increased resistance to flow in the smallest airways.

Pulmonary disability in coal workers' pneumoconiosis

Results from a correlation survey which compared radiological and physiological findings during life with detailed morbid anatomical findings in the lungs of 247 deceased miners and ex-miners with pneumoconiosis were used to assess the extent and significance of their pulmonary disability.Coal workers' pneumoconiosis usually caused progressive impairment of ventilation, which in the simple type of disease was not related to radiological category. In such cases the presence of emphysema was found to be a more important factor in determining the impairment of ventilation than the radiological category of simple pneumoconiosis.