First-pass studies of acute lung injury.

Mild hydrochloric acid was introduced to a caudal lung section in each of eight dogs to induce injury. Transits of 99mTc-labeled red blood cells (RBC) and [123I]iodoantipyrine (IAP) injected intravenously were recorded by a scintillation camera. Lungs and blood samples were analyzed post-mortem. Peak-to-equilibrium ratios (P/E) of RBC time-activity curves were computed to be 3.83 +/- 0.54 for the control lung, 2.58 +/- 0.55 for the injured lung and 2.23 +/- 0.58 for the injured caudal section. For IAP, the respective results were 3.78 +/- 0.29, 2.02 +/- 0.18 and 1.77 +/- 0.17. The decrease of P/E in injured areas was attributed to reduced blood flow. Using mean transit times of the tracers, we computed extravascular lung water per unit blood volume to be 0.35 +/- 0.18 for the control lungs and an increased value of 0.68 +/- 0.24 for the injured lungs. These results displayed sensitivity to injury, but were gross underestimates relative to the corresponding values of 2.04 +/- 0.54 and 4.56 +/- 1.85 in post-mortem analyses.