Cardiopulmonary adaptation to exercise in coal miners

Twenty-six coal miners, without associated functional chronic obstructive lung disease (COLD), assessed by normal airway resistance, were divided into three groups: (1) Group C, normal X-ray; (2) Group S1, micronodular silicosis; and (3) Group S2, complicated silicosis. All subjects were evaluated while at rest and during exercise. Significant lung volume reduction was observed in the S2 Group only. Blood gases, pulmonary pressure, and cardiac output were found to be within the normal range for all three groups when at rest. The pulmonary pressure and pulmonary vascular resistance were higher, however, for the S1 and S2 Groups when compared to the C Group. During exercise, pulmonary hypertension was observed in 50% of teh patients with complicated silicosis. When all data (N = 26) were included, the high values for pulmonary pressure and pulmonary vascular resistance correlated well with the loss in vital capacity (VC) and the decrease in forced expiratory volume in 1 sec (FEV 1.0). From the initial 26 patients, 19 were selected on the basis of their normal airway resistance and FEV 1.0/VC ratio. This selection did not alter the differences noted for the pulmonary pressure and total pulmonary vascular resistance, which previously existed between the groups, even though the correlations were not statistically significant. We conclude that silicosis without associated COLD leads to mineral hemodynamic impairment at rest and during exercise, and that airway resistance does not detect impairment of flow as effectively as FEV 1.0 reduction. The increased pulmonary vascular resistance observed, especially in complicated silicosis, may be best explained by the loss of lung parenchyma and possible impairment of small airways.