Aerosol transport throughout inspiration and expiration in the pulmonary airways

Abstract

Little is known about transport throughout the respiration cycle in the conducting airways. It is challenging to appropriately describe the time-dependent number of particles entering back into the model during exhalation. Modeling the entire lung is not feasible; therefore, multidomain methods must be used. Here, we present a new framework that is designed to simulate particles throughout the respiration cycle, incorporating realistic airway geometry and respiration. This framework is applied for a healthy rat lung exposed to ∼ 1μm diameter particles, chosen to facilitate parameterization and validation. The flow field is calculated in the conducting airways (3D domain) by solving the incompressible Navier-Stokes equations with experimentally derived boundary conditions. Particles are tracked throughout inspiration by solving a modified Maxey-Riley equation. Next, we pass the time-dependent particle concentrations exiting the 3D model to the 1D volume conservation and advection-diffusion models (1D domain). Once the 1D models are solved, we prescribe the time-dependent number of particles entering back into the 3D airways to again solve for 3D transport. The coupled simulations highlight that about twice as many particles deposit during inhalation compared to exhalation for the entire lung. In contrast to inhalation, where most particles deposit at the bifurcation zones, particles deposit relatively uniformly on the gravitationally dependent side of the 3D airways during exhalation. Strong agreement to previously collected regional experimental data is shown, as the 1D models account for lobe-dependent morphology. This framework may be applied to investigate dosimetry in other species and pathological lungs.

Mechanical properties of the airway tree: heterogeneous and anisotropic pseudoelastic and viscoelastic tissue responses

“…The predictive capabilities of pulmonary mechanics computational models are limited by the unavailability of airwayspecific constitutive relations. Previous studies highlighted the need for relevant experimental data to inform physiological models, especially for the bronchial tree (17,45,48,57). Past studies extensively investigated the buckling and folding behavior of the airways due to inflammation and bronchoconstriction in diseases such as asthma and bronchitis, since the effect is directly tied to airway resistance (4,16,53).…”

Impact of Wildfires on Cardiovascular Health

“…14 Although direct measurement of particle deposition and clearance remain challenging to date, dosimetry models that couple airflow simulations with particle transport facilitate prediction of regional deposition fractions. 122,[124][125][126] As an additional benefit, these computational tools enable incorporation of processes for particle transport, deposition, and clearance that are tailored to each species and, therefore, remain instrumental in establishing equivalent exposure conditions between animals and humans.…”

A revision of the multiple‐path particle dosimetry model focusing on tobacco product aerosol dynamics

“…These methods can be used for broad measures of the amount of aerosol deposition and uptake, such as total, organ‐specific, or lung lobe‐specific dosimetry; however, other approaches are necessary for analyzing local concentrations of aerosols. Computational modeling is a common approach for simulating the deposition and uptake amount in animal and human airways 6–9 . These days, simulated dosimetry is practically employed for toxicological assessment.…”

“…Computational modeling is a common approach for simulating the deposition and uptake amount in animal and human airways. [6][7][8][9] These days, simulated dosimetry is practically employed for toxicological assessment. For example, the Organization for Economic Co-operation and Development (OECD) showed a case study in which human equivalent concentration was estimated by calculation based on computational fluid dynamics (CFD) modeling.…”