Computational fluid dynamics simulations of inhaled nano- and microparticle deposition in the rhesus monkey nasal passages.

Anatomically accurate computational fluid dynamics (CFD) models of the nasal passages of an infant (6 months old, 1.3 kg) and adult (7 years old, 11.9 kg) rhesus monkey were used to predict nasal deposition of inhaled nano- and microparticles. Steady-state, inspiratory airflow simulations were conducted at flow rates equal to 100, 200 and 300% of the estimated minute volume for resting breathing in each model. Particle transport and deposition simulations were conducted using the Lagrangian method to track the motion of inhaled particles. Nasal deposition fractions were higher in the infant model than the adult model at equivalent physiologic flow rates. Deposition curves collapsed when differences in nasal geometry were accounted for by plotting microparticle deposition versus the Stokes number and nanoparticle deposition as a function of the Schmidt number and diffusion parameter. Particle deposition was also quantified on major nasal epithelial types. Maximum olfactory deposition ranged from 5 to 14% for 1-2 nm particles in the adult and infant models, depending on flow rate. For these particle sizes, deposition on respiratory/transitional epithelia ranged from 40 to 50%. Increased deposition was also predicted for olfactory and respiratory/transitional epithelia for particle sizes >5 µm in the infant model and >8 µm in the adult model. Semi-empirical curves were developed based on the CFD simulation results to allow for simplified calculations of age-based deposition in the rhesus monkey nasal passages that can be implemented into lung dosimetry models.