A semi-analytical dosimetry model for inspiratory flow of reactive gases in the lung

A semi-analytical dosimetry model for steady flow and mass transfer in cylindrical tubes is developed for reactive gas transport and uptake in proximal airways of the lung during quasi-steady inspiratory flow. The model is used to predict the longitudinal concentration distribution of inhaled ozone along selected airway pathways in the lung of a two-month-old rhesus monkey. Two ideal airway structures are considered; a symmetrically-branched model based on computer tomography (CT) scan measurements and an asymmetric one informed by airway measurements from magnetic resonance imaging (MRI) data. The model is validated by comparison with predictions of computational fluid dynamics (CFD) simulations of ozone transport and uptake in an anatomically-accurate airway structure reconstructed from MRI data. The relative error between the CFD results and model predictions for the asymmetrically-branched airway structure is less than 1.5% along all airway paths, rendering the dosimetry model a computationally efficient tool for capturing longitudinal variations of reactive species concentration within the lung airways.