BIEXPONENTIAL PULMONARY CLEARANCE OF TC-99M-DTPA INDUCED BY DETERGENTAEROSOL

We measured the pulmonary clearance of technetium-99m-labeled diethyle netriamine pentaacetatic acid (Tc-99m-DTPA) for 3 h after perturbation of the surfactant system by administration of the detergent dioctyl s odium sulfosuccinate in aerosol. Forty-two rabbits were anesthetized w ith pentobarbital sodium. Tracheostomies were performed, and the rabbi ts were mechanically ventilated. Increasing concentrations of detergen t (0.125-2%) or vehicle were given for 5 min, and clearance measuremen ts were performed immediately or 60 min after detergent administration . No animals developed respiratory distress. After vehicle, the cleara nce was monoexponential with a half-life of 158 min. Detergent induced a biexponential clearance with a rapidly clearing additional pool of radioactivity with a half-life of 5-15 min. The relative amount of rad ioactivity clearing rapidly increased with detergent concentration. Th e detergent effect was partly reversible. We conclude that detergent i nduces a biexponential clearance of Tc-99m-DTPA by accelerating the tr ansfer of tracer across the alveolocapillary barrier in a proportion o f lung units in a dose-related manner.