Pulmonary lymphatic clearance of 99mTc-DTPA from air spaces during lung inflation and lung injury.

ABSTRACT

A total of 22 sheep with lymphatic cannulas were used to determine if 99mTc-labeled diethylenetriaminepentaacetic acid (DTPA) clears directly from the air spaces of the lungs into the lymph vessels. Each sheep was anesthetized and ventilated with an aerosol of the DTPA for 2-5 min, and the DTPA activities in the lymph and plasma were measured every 15 min for 2 h. After the first 45 min, the average ratio of the DTPA in the lymph to that in the plasma (L/P) was 1.03 +/- 0.06 (SD) in the six control experiments and 1.11 +/- 0.05 in the six experiments in which the lungs were inflated with a positive end-expired pressure of 10 cmH2O throughout the study. Direct movement of the DTPA from the air spaces into the lymph was not necessary to account for the DTPA clearance in these experiments because the L/P ratio was not significantly different from 1.0. Eight additional sheep received intravenous infusions of air at 0.2 ml.kg-1.min-1 for 2 h to induce lung injury before depositing the DTPA. In these sheep L/P was 1.53 +/- 0.28, which was significantly higher than the value measured in the control group (P less than 0.01). We considered the possibility that the increased L/P ratio in these sheep could be due to alterations in the distribution of the blood flow to the tissue, but the L/P ratio in four sheep whose distribution of blood flow was altered by inflation of a balloon in the right pulmonary artery was 1.05 +/- 0.10, the same as the control value.(ABSTRACT TRUNCATED AT 250 WORDS)