Nasal Dosimetry Modeling for Humans

Abstract

An anatomically accurate, finite element mesh of the right human nasal cavity was constructed from computerized axial tomography (CAT) scans of a healthy adult nose. The equations of motion were solved numerically to determine the steady laminar inspiratory airflow patterns at quiet breathing flow rates. The numerically computed velocity field was compared with the experimentally measured velocity field in a large-scale (20x) model, which was built by scaling up from the same CAT scans. Numerical results showed good agreement with the experimental results throughout the nasal cavity. The numerical velocity field was then used in the solution of the steady convective diffusion equation using the finite element mesh to determine the uptake pattern of inhaled pollutants. The mass transfer boundary condition used at the nasal cavity wall included the effects of solubility, diffusivity, and removal of pollutants by first-order chemical reaction in the mucosal lining. The results showed that about 80% of highly soluble or highly reactive pollutants are absorbed up to the posterior end of the nasal turbinates. For these pollutants, most uptake occured in the anterior and lower half of the nasal cavity. For more insoluble pollutants, uptake was more uniform along the nasal cavity. Finite element and physical models are powerful new tools that, when combined with information on human nasal mucosal histology, blood flow, and biochemistry of the pollutant reactions in the mucosa and throughout the body, can provide valuable information on nasal dosimetry of inhaled pollutants.