Fine particle deposition within human nasal airways.

An original mathematical model describing particle diffusion in human nasal passages is presented. A unique feature of the model is that it combines effects of both turbulent and laminar flows. To account for turbulence, concentration equations written in cylindrical coordinates are first simplified by a scaling technique and then solved analytically based on momentum/mass transfer analogy. To describe laminar motion, the work of Martonen et al. (1995a) is modified for application to nasal passages. The predictions of the new model agree well with particle deposition data from experiments using human replica nasal casts over a wide range of flow rates (4-30 L/min) and particle sizes (0.001-0.1 micro m). The results of our study suggest that a complex fluid dynamics situation involving a natural transition from laminar to turbulent motion may exist within human nasal passages during inspiration. The model may be used to predict deposition efficiencies of inhaled particles for inhalation toxicology (e.g., the risk assessment of air pollutants) and aerosol therapy (e.g., the treatment of lung diseases) applications.