Predicted tracheobronchial and pulmonary deposition in a murine asthma model

Particulate matter dosimetry provides the critical link between exposures and initial doses reaching various sites in the respiratory tract. To extrapolate findings from animal models to humans, quantitative respiratory-tract anatomical data dosimetry in these animal models is required. The goal of this study was to provide anatomical information for the tracheobronchial and pulmonary region so predictions of particle deposition could be performed for a widely used model of asthma; the sensitized Balb/c mouse. Tracheobronchial airway morphometry of sensitized male Balb/c mice was generated from three in situ prepared lung casts. Distribution of the number of generations to terminal bronchiole for each lung lobe was determined by assigning a unique binary number to each airway. This strategy enabled the median path length to terminal bronchiole to be determined. A total of 25 median length paths to terminal bronchiole were measured (airway length, diameter, and branch angle) in each lung cast. These 25 paths were proportionately distributed among the six lobes based upon the number of median length pathways in each cast. Airway length, diameter, and branch angle were measured for each airway in the 25 median length pathways. Measurements of airway length, diameter, and branch angle for each generation were averaged to create a typical path tracheobronchial anatomy model. A pulmonary airway model was also developed so that particle deposition predictions could be performed for particle diameters of 0.2-10 micrometers. Particle deposition efficiency predictions were consistent with in vivo measured deposition.