Deposition of medical aerosols in the human respiratory tract: Predicting dosages from nebulizers, and deposition in the mouth-throat using computational fluid dynamics

A Lagrangian dynamical model for calculating the regional deposition of hygroscopic aerosols in the respiratory tract is presented. The model tracks a bolus of aerosol as it travels through the respiratory tract and calculates the growth of the particles using a full two-way coupled hygroscopic growth model in which the change in aerosol droplet size affects the humidity and temperature of the air in the respiratory tract. The deposition probabilities for a particle in a specific generation are calculated from theoretical and empirical expressions. A method to estimate the intersubject variability is also presented. The deposition probabilities calculated by the model agree well with available experimental data.;A methodology is presented in which experimental methods that characterize the aerosol emitted by jet nebulizers are combined with the deposition model to predict the dosage of medication delivered to the different regions of the respiratory tract. The methodology is applied to the Hudson T-Updraft II nebulizer, and the Pari LC+ nebulizer. The dosage delivered to the lungs by the Hudson is estimated as 16.1 ;Computational fluid dynamics (CFD) is investigated as a tool to predict the deposition of aerosol particles in the mouth and throat by testing a commercially available CFD package (TASCflow3D, ASC, Waterloo, ON) on a number of geometries. For laminar flow in tubes with simple 90-degree bends, CFD provided accurate predictions of the particle deposition. In the USP model throat, the overall filtering efficiency of the model and the deposition pattern predicted by the CFD agreed poorly with the filtering efficiency and deposition patterns determined experimentally. Finally, the code was tested in a novel geometry that approximates the extrathoracic region of the respiratory tract. Here, the deposition patterns agreed reasonably well with experimentally determined patterns, but the CFD greatly overestimated the deposition compared with experimentally determined values and the values from an empirical equation for the deposition of droplets in the extrathoracic region of the respiratory tract. The poor performance of CFD in the USP model throat and the physiologically realistic throat geometry may be due to the inadequacy of current models of turbulence and turbulent dispersion.