BIEXPONENTIAL PULMONARY CLEARANCE OF TC-99M-DTPA INDUCED BY DETERGENT AEROSOL

We measured the pulmonary clearance of technetium-99m-labeled diethylenetriamine pentaacetatic acid (Tc-99m-DTPA) for 3 h after perturbation of the surfactant system by administration of the detergent dioctyl sodium sulfosuccinate in aerosol. Forty-two rabbits were anesthetized with pentobarbital sodium. Tracheostomies were performed, and the rabbits were mechanically ventilated. Increasing concentrations of detergent (0.125-2%) or vehicle were given for 5 min, and clearance measurements were performed immediately or 60 min after detergent administration. No animals developed respiratory distress. After vehicle, the clearance 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 radioactivity clearing rapidly increased with detergent concentration. The detergent effect was partly reversible. We conclude that detergent induces a biexponential clearance of Tc-99m-DTPA by accelerating the transfer of tracer across the alveolocapillary barrier in a proportion of lung units in a dose-related manner.