Dynamics of Oropharyngeal Aerosol Transport and Deposition With the Realistic Flow Pattern

Abstract

Aerosol flow and deposition in the model of human oropharynx was studied theoretically and experimentally for two realistic inspiratory patterns. The three-dimensional (3D) airflow structure in the sample geometry was solved with the computational fluid dynamics (CFD) code (Fluent), used to calculate dynamic distribution of particle deposition (0.3-10 mum). Experiments were done for the same flow conditions using the silicone-rubber cast with the matching geometry. Nonsteady breathing flows were reproduced with the computer-controlled artificial lung apparatus. Results of computations show that particles smaller than 3 mum easily pass the oropharynx during inspiration, while particles with a size close to 10 mum are substantially deposited, preferentially in the region of the naso-pharyngeal bend. For particles in the submicrometer size range, the spatial and temporal deposition pattern is more complicated, and strongly depends on breathing dynamics. The experiments confirmed that the mass median diameter (MMD) of the aerosol that penetrates the oropharynx and flows to the tracheobronchial tree is reduced. Measured total mass efficiency of deposition of the tested aerosol was in the range of 35-60%, depending on the breathing pattern. These findings are consistent with the CFD results. The methods and the preliminary results enable a more realistic analysis of dynamic effects during the flow of inhaled particles through the complex geometry of the oropharynx. Such analysis is needed for estimation of toxic potential of aerosols, related to their local deposition in different parts of the respiratory tract.

Multicomponent aerosol particle deposition in a realistic cast of the human upper respiratory tract

“…It is therefore important to fully understand the aerosol dynamics in both in vitro exposure systems and the human respiratory tract. To determine the exposure and local deposition in the complex human airways at realistic flow conditions, aerosol particle deposition has been studied experimentally using physical in vitro replicas of the human respiratory tract (Chan & Lippmann, 1980;Cheng et al, 1999;Sosnowski et al, 2006), which are often generated from computed tomography or magnetic resonance imaging images. Many studies have been performed on extrathoracic deposition in mouth and throat replica (Cheng, 2012;Golshahi et al, 2013;Grgic et al, 2004a,b;Zhang et al, 2004).…”

Evaluation of a Drift Flux Model for Simulating Submicrometer Aerosol Dynamics in Human Upper Tracheobronchial Airways

“…Furthermore, previous studies have highlighted the physical significance of inhalation and exhalation waveforms. 78 Each of these factors affects the physical realism of the model predictions in relation to actual particle deposition in the lung. These limitations should be addressed in future studies in order to develop more physically realistic models of particle deposition for fine aerosols.…”

Aerosol Dosimetry Modeling Using Computational Fluid Dynamics

“…Geometries of the respiratory system of animals, such as the replica of an average rat respiratory tract [100], have also been generated using CT images. Combinations of CT and MRI images have also been used to generate an average geometrical model of the mouth and throat [75], a realistic head airway geometry [16,17], models of the human upper respiratory tract [101], and detailed geometrical models of rat, monkey and human respiratory tracts [102], including 17 7 ± , 19 9 ± and 9 2 ± airway generations, respectively.…”

“…In these experiments, the deposition of fluorescent particles was studied for generations 9-11 of the lung where the airway diameter is about 1 mm. A realistic head airway geometry was generated by Sosnowski et al [16,17] from computed tomography (CT) and magnetic resonance imaging (MRI) images, in which the influence of realistic breathing patterns on the deposition was measured for various particle sizes. Experiments on cigarette smoke deposition have also been performed on a human replica of the tracheobronchial airways generated from CT scans [18].…”