Total lung capacity in asbestosis: a comparison of radiographic and body plethysmographic methods

The effect of asbestosis on lung volumes was studied in 46 workers by measuring total lung capacity (TLC), forced vital capacity, vital capacity, and residual volume using two standard methods: body plethysmography and radiographic lung area. Nine men had neither irregular opacities of any International Labour Office profusion category nor pleural abnormalities; 9 had pleural abnormalities only, 19 had irregular opacities only; and 9 had pulmonary asbestosis with pleural plagues. Of the 28 with irregular opacities, 18 had moderate or advanced asbestosis (category 2/1 or greater). The radiographic method gave a mean TLC of 8.11 L and the body plethysmographic mean was 8.09 L. Thus, the radiographic and plethysmographic methods produced virtually identical mean values for TLC and for residual volume 3.84 L and 3.8 L and residual volume/TLC, 47.3 and 47.3, respectively. Lung volumes measured by body plethysmography and by x-ray area were the same in each of the four radiographic categories of asbestosis. The air trapping and normal or slightly elevated TLC, which characterize asbestosis in men who have smoked cigarettes, are revealed by both methods. The radiographic method, when adequate measures are taken to obtain full inspirations, effectively duplicates the body plethysmographic method but is quicker and simpler, particularly for field studies.