A simple mechanistic model of deposition of water-soluble aerosol particles in the mouth and throat.

Aerosol drugs are usually delivered to the lung by inhalation via the oral route, since aerosol deposition is much lower in the oral than in nasal airways. In the present study a practical, non-CFD-based, mechanistic model is developed, which permits an efficient calculation of deposition along the oral route with simple computational means. A simplified geometrical description of the mouth and throat region is used, based on a sequence of conducting ducts. The numerical model takes into account aerosol dynamics, which enables to express the impact on aerosol transport and deposition of the hygroscopic growth of water-soluble particles. Simulations are made for coarse particles in the range 1-17 microm, and the model predictions are found in good agreement with the available experimental data. The model predicts inertial impaction to be the dominant mechanism, and correctly reproduces the increase in the deposition with an increasing flow rate and particle diameter. Higher deposition is calculated in the oropharyngeal region than the laryngeal region, due to the significant flow direction change and constriction at the end of the oral cavity. According to the model, highly soluble particles may deposit up to 50% more than inert aerosols in the mouth-throat region. The proposed model will be useful for quick, practical calculations of deposition with a full account of aerosol dynamical processes.