Rp. Subramaniam et al., COMPUTATIONAL FLUID-DYNAMICS SIMULATIONS OF INSPIRATORY AIR-FLOW IN THE HUMAN NOSE AND NASOPHARYNX, Inhalation toxicology, 10(2), 1998, pp. 91-120
Extrapolation of the regional dose of an inhaled xenobiotic from labor
atory animals to humans for purposes of assessing human health risk is
problematic because of large interspecies differences in nasal respir
atory physiology and airway anatomy. There is a need for dosimetry mod
els that can adjust for these differences in the upper respiratory tra
ct. The present work extends previous efforts in this laboratory and e
lsewhere to simulate nasal airflow profiles numerically in laboratory
animals and humans. A three-dimensional, anatomically accurate represe
ntation of an adult human nasal cavity and nasopharynx was constructed
. The Navier-Stokes and continuity equations for airflow were solved u
sing the finite-element method under steady-stale, inspiratory conditi
ons simulating rest and light exercise (steady-state inspiratory flow
rates: 15 L/min and 26 L/min, respectively) with the fluid dynamics so
ftware package FIDAP. Simulated airflow was streamlined in the main na
sal passages and complex in the vestibule and nasopharynx. Swirling ai
r currents and recirculating flow were predicted in the nasal vestibul
e, and the expansion at the nasopharynx gave rise to two downward, cou
ntercurrent, spiraling vortices. Significant lateral flow was observed
mainly in the middle lateral meatus. Flow apportionment among differe
nt regions of the nose remained almost unchanged between the two inspi
ratory rates simulated. Fastest flow occurred in the posterior nasal v
alve region. In the main nasal airway, the highest airspeeds occurred
through the ventral and middle medial regions. Simulated velocity fiel
ds and pressure drops across the nasal cavity generally agreed with ex
perimental results from the literature. It is proposed that this model
can be used to reduce uncertainty in human health risk assessment for
inhaled materials and to assess changes in airflow and nasal resistan
ce due to common surgical procedures and medical conditions.