Clearance of aerosolized Tc-99m DTPA from normal vs. acutely smoke-injured dog lungs

Acute cigarette smoke exposure is known to reversibly increase the clearance rate of aerosolized DTPA from human lungs. The authors studied DTPA clearance after acute severe plywood smoke exposure, on the order of that experienced by burn victims, since current diagnostic methods (Xe-133 and radiographs) for major inhalation injury are insensitive and/or non-specific. Smoke generated from burning plywood sawdust and kerosene was delivered via endotracheal tube at 370C. Skin burns were not inflicted (so the pulmonary consequences of thermal injury were not factors). Chest radiographs and Xe-133 studies were obtained before and after smoke injury but before DTPA aerosol delivery. Six normal and 7 smoke-exposed anesthetized mongrel dogs were studied with 3 mCi of Tc-99m DTPA delivered by aerosol for 5 minutes. Pulmonary Tc-99m DTPA activity was quantitated by computer. Data were acquired over the lungs at 1 frame per 10 secs. for 16 minutes, and the t/sub 1/2/ of DTPA washout from the lungs was calculated. The mean t/sub 1/2/ of 6 normal dogs was 36.52 min. (S.D. 17.73), while the t/sub 1/2/ of 7 smoke-injured dogs was 6.08 min. (S.D. 1.99). The longest t/sub 1/2/ of an injured lung (9.68 min.) was slightly more than half of the shortest t/sub 1/2/ of a normal lung (15.36 min). Thus, acutely smoke-injured dog lungs clear Tc-99m DTPA much faster than normal lungs, consistent with an increase in lung epithelial permeability. This technique may be promising clinically, since early diagnosis of inhalation injury is important for optimal therapy