Asbestos-induced pleural fibrosis and impaired exercise physiology.
Shih-F; Wilson-JS; Broderick-A; Watt-JL; Galvin-JR; Merchant-JA; Schwartz-DA
Chest 1994 May; 105(5):1370-1376
The relationship between asbestos (1332214) induced pleural fibrosis and abnormal lung function during cardiopulmonary exercise was examined. The cohort consisted of 90 males, mean age 62.1 years, who had been occupationally exposed to high concentrations of asbestos dust for at least 1 year; 79.3% were former or current smokers. Chest X-rays were obtained and examined for abnormalities according to 1980 International Labor Office criteria. Resting pulmonary function testing was performed. The subjects instrumented with electrocardiographs exercised on a cycle ergometer at increments of 20 to 25 watts per minute. Oxygen uptake (VO2), carbon-dioxide production (VCO2), respiratory exchange rate, tidal volume, and other variables related to respiratory function were monitored. Exercise was continued until the subjects indicated they could no longer continue or electrocardiogram changes indicated that continuing would be dangerous. Among the 82 subjects who completed the study, 33 had radiographically normal pleura, 33 had circumscribed pleural plaques, and 14 had diffuse pleural thickening. Asbestosis was detected in 40% of the subjects with normal pleura, 39% of those with circumscribed pleural plaques, and 14% of those with diffuse pleural thickening. Subjects with pleural plaques and diffuse pleural thickening tended to have lower forced vital capacity and reduced air flows and lung volumes, respectively. Pulmonary function or gas exchange during exercise was not affected by the presence of circumscribed pleural plaques or diffuse pleural thickening. Impaired gas exchange, as manifested by increases in the physiological dead space volume/tidal volume (VD/VT) ratio and alveolar arterial oxygen pressure difference, was seen in subjects with asbestosis. Regression analysis showed that the presence of circumscribed pleural plaques and diffuse pleural thickening was independently associated with significant increases in the VD/VT ratio during exercise. The authors conclude that asbestos induced circumscribed pleural plaques and diffuse pleural thickening are independently associated with decrements in gas exchange during maximal exercise.
NIOSH-Grant; Pulmonary-system-disorders; Asbestos-workers; Occupational-exposure; Chest-X-rays; Pulmonary-function-tests; Lung-fibrosis; Physical-exercise
Internal Medicine University of Iowa Pulmonary Disease Division Iowa City, IA 52242
Pulmonary System Disorders
University of Iowa, Iowa City, Iowa