Dual-isotope measurement of lung water.

Iodine-131-labeled iodo-antipyrine and 99mTc-labeled erythrocytes were used to measure water content in lungs. These radioactive tracers were injected into 11 dogs with injured lungs. Blood samples were drawn and the animals sacrificed. The lungs were removed, weighed and homogenized. Samples of blood and lung homogenate were assayed for 131I and 99mTc. Samples were also weighed before and after drying to a constant weight at 70-76 degrees C. Extravascular lung water was determined by the dual-isotope technique and again by gravimetric analysis. The average ratio of the results from the two different methods was 1.14 +/- 0.20. The two methods were also compared by regression analysis and the correlation coefficient was 0.97 +/- 0.09.