Methodology For Delivery and Kinetics of Clearance of Insoluble Particles from Sublobar Lung Segments

Abstract

Anesthetized, mixed breed dogs were studied in a supine position, mechanically ventilated and imaged from the ventral aspect by γ-camera. Five dogs were evaluated; four of these were restudied to determine repeatability of the methods. A ventilation scan (¹³³ Xe gas) was used to characterize the homogeneity of ventilation and to outline regions of analysis. An aqueous, insoluble radiolabeled aerosol (^99m Tc-sulfur colloid) was generated by ultrasonic nebulization and delivered directly through a channel of a bronchoscope scope into sublobar bronchi. Lung retention of particles was measured continuously for ~ 1 h, followed by recovery; and dogs were reimaged at 6- and 24-h time points postdeposition. After the initial hour of clearance, mean particle retention tended to be lower in left lung segments as compared to the right lung segments, that is, 57.3% (±5.0% SE) and 75.4% (±6.7%), respectively; however, these differences were not significant. At the 6-h time postdeposition, clearance was more comparable between lung segments, that is, mean retention of 43.3% for the left versus 50.4% for the right lung segments. A small, additional amount of particle clearance occurred by the 24-h endpoint; the final mean retention levels were 34.8% and 47.1 % for respective left and right lung segments. This technique assesses mucociliary clearance of aqueous aerosols delivered directly to the epithelial surfaces of sublobar bronchi.