Predicted Nasal and Tracheobronchial Particle Deposition Efficiencies for the Mouse

Abstract

Few models are available for predicting the efficiency of deposition of inhaled particles in the various regions of the respiratory tract of the mouse. The purpose of this study was to improve the ability to predict upper airway (nose, pharynx and larynx) and tracheobronchial deposition efficiencies for inhaled aerosols in the laboratory mouse. Currently-used equations for predicting nasal deposition efficiencies in humans are semi-empirical and utilize airflow and/or pressure drop data. Therefore, we measured nasal pressure drop and airflow in anaesthetized mice and used this information, together with published data, to formulate aerosol deposition equations. Tracheobronchial deposition efficiency is usually predicted by considering three mechanisms (impaction, sedimentation and diffusion), along with airway anatomical and airflow information. A typical path tracheobronchial airway geometry, complete to the terminal bronchiole, was developed for the mouse from detailed measurements of three replica respiratory tract casts. Particle deposition efficiency calculations were then performed for the tracheobronchial region of the adult mouse and compared with published estimates of aerosol deposition in mice. The calculations, which covered a particle diameter range of 0.1–100 μm (aerodynamic), tended to underestimate the experimental measurements in mice. The calculations did not take into account deposition during exhalation, or the effects of several other complex factors.