. Use of radioisotopes in the study of textile workers with byssinosis and chronic lung damage. A radioisotope method of measuring separately the circulation times for the pulmonary artery and pulmonary veins is described. Combined with pulmonary scintigraphy this method has been used to invesigate textile workers with lung changes.In the workers with no evidence of heart failure there was a prolongation of the pulmonary artery circulation time but no change in the pulmonary venous circulation time. In workers with signs of right heart failure there was a prolongation of right heart filling time as well as pulmonary artery circulation time but still no prolongation of the pulmonary venous circulation time. In this group the cardiac stroke volume was reduced but the output was maintained by a tachycardia. In spite of the prolonged pulmonary circulation time there was a reduction in pulmonary blood volume and poor perfusion on the scintigram.The use of radioisotopes in circulation studies can be applied to the clinical diagnosis of pulmonary disease (Johnson, Lin, Akcay, and Taplin, 1964;Oriol, Anthonisen, and McGregor, 1968;Vaskov, 1970;Mihailov et al., 1970). Vascular lung scintigrams make it possible to show diffuse or localized areas where the circulation is disturbed (Taplin, Johnson, Dore, and Kaplan, 1964). Radioisotopes can now be used also to study the central haemodynamics in occupational lung diseases (Vaskov, 1966;1970;1972).Two methods for determining the pulmonary artery circulation time separately from the pulmonary venous circulation time have been described already: (1) with a mixture of iodine-131 (1311) and iodine-125 , and (2) with 1311 only (Vaskov, 1970). In this study the last method is applied to the clinical investigation of chronic lung disease in textile workers. 37
MethodsRadiocardiography and radiocirculography The method is described diagrammatically in Figure 1. A bolus of radioactive material was injected into the right antecubital vein, and its passage first through the right heart and then through the left heart was picked up by counter I placed over the precordium. This records two peaks which represent the passage of the bolus through the right heart (R) and left heart (L) respectively. The time from injection (0) to the beginning of the ascent to R is the peripheral venous time, the ascent to R is the right heart filling time, and the distance between peaks R and L is the mean pulmonary circulation time (or central pulmonary circulation time). A pair of counters (II) were placed tangentially over the middle peripheral lung fields (left and right); these recorded the transit of radioindicator in the lung periphery or capillary bed. By arranging synchronous recording of these traces (see Fig. 2), it is possible to use the pulmonary peak (P) (Fig. 1) to divide the pulmonary circulation time into two-the arterial time (R to P) and the venous time
