Deposition and Clearance Following Inhalation and Intratracheal Injection of Particles

Abstract

The pulmonary deposition patterns and the clearance rates of insoluble particles from the lungs of rats were measured during the early post-exposure period following inhalation and intratracheal injection. The data were analyzed by assuming that the pulmonary system consists of a series of compartments and that these compartments are cleared sequentially in time via the trachea. Based on these assumptions, the intratracheal injection technique produced a relatively greater deposition of particles in the lower respiratory tract as compared with inhalation. The clearance kinetics of particles from the lungs were similar for particles deposited in equivalent compartments of the pulmonary system by the two methods of exposure, suggesting that clearance from a given lung compartment is independent of the distribution of particles within that compartment. If this inference is valid, the clearance kinetics obtained following intratracheal injection of particles should not differ from those obtained following inhalation, even though the fractional deposition of particles in lung compartments may differ following the two methods of exposure.