AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Quantifying Inter-individual Variability in Nasal Filtration of Nebulized Micron-sized Particles as a Function of Nasal Anatomy using Computational Fluid Dynamics
Azadeh Borojeni, John Rhee, GUILHERME GARCIA, Medical College of Wisconsin
Abstract Number: 76 Working Group: Health Related Aerosols
Abstract Background: Pharmaceutical aerosols are often used to treat nasal diseases, such as nasal airway obstruction (NAO) and chronic rhinosinusitis (CRS). Inter-individual differences in nasal anatomy are expected to have a significant impact on the dose of nebulized medication that reaches each region of the nasal cavity. However, the relationship between inter-subject variability in nasal anatomy and intranasal doses of inhaled medications remains poorly understood.
Objectives: The goal of this study is to develop a quantitative understanding of how inter-individual variations in nasal anatomy lead to inter-individual differences in nasal deposition of nebulized micron-sized particles.
Materials and Methods: Three-dimensional models of the human nasal cavity were created from cone beam computed tomography (CBCT) and medical CT scans representing 27 healthy subjects and 15 patients with NAO. The paranasal sinuses were excluded under the assumption that they have a minimal impact on airflow in the main nasal cavity. Tetrahedral meshes with 4 prism layers were created with ~4 million cells. Nasal airflow was modeled as laminar. The deposition of spherical particles with aerodynamic diameters da = 1-30 µm was studied for a steady-state inhalation rate of Q = 15 L/min.
Results: Our numerical results confirmed that particle deposition in the human nasal cavity is dominated by inertia with 1µm particles having <10% deposition, while 30µm particles have nearly 100% deposition in all individuals. Substantial inter-individual variability was observed for particle sizes 5µm to 20µm. For example, the deposition efficiency of 10µm particles varied from 10% to 100% among individuals. NAO patients had higher intranasal doses than healthy subjects. Unilateral nasal deposition efficiency (DF) nearly collapsed onto a single curve when the data for all subjects was plotted as function of the modified impaction parameter IP = da2Δp, where Δp is the transnasal pressure drop.
Conclusions: Inter-individual variations in nasal filtration of micron-sized particles can be mostly attributed to inter-individual variations in transnasal pressure drop (i.e., nasal resistance to airflow).