Regional Deposition of Particles in an Image-Based Airway Model: Large-Eddy Simulation and Left-Right Lung Ventilation Asymmetry

Abstract

Regional deposition and ventilation of particles by generation, lobe and lung during steady inhalation in a computed tomography (CT) based human airway model are investigated numerically. The airway model consists of a seven-generation human airway tree, with oral cavity, pharynx and larynx. The turbulent flow in the upper respiratory tract is simulated by large-eddy simulation. The flow boundary conditions at the peripheral airways are derived from CT images at two lung volumes to produce physiologically-realistic regional ventilation. Particles with diameter equal to or greater than 2.5 microns are selected for study because smaller particles tend to penetrate to the more distal parts of the lung. The current generational particle deposition efficiencies agree well with existing measurement data. Generational deposition efficiencies exhibit similar dependence on particle Stokes number regardless of generation, whereas deposition and ventilation efficiencies vary by lobe and lung, depending on airway morphology and airflow ventilation. In particular, regardless of particle size, the left lung receives a greater proportion of the particle bolus as compared to the right lung in spite of greater flow ventilation to the right lung. This observation is supported by the left-right lung asymmetry of particle ventilation observed in medical imaging. It is found that the particle-laden turbulent laryngeal jet flow, coupled with the unique geometrical features of the airway, causes a disproportionate amount of particles to enter the left lung.

Validating Whole-Airway CFD Predictions of DPI Aerosol Deposition at Multiple Flow Rates

“…These additional geometric details were found to modify the overall predicted deposition of pharmaceutical aerosols in the region of B1-B3. Curvature of the trachea was also shown to alter the aerosol distribution pattern among the lung lobes, as previously reported by Lambert et al (37) In both Models C and D, significant time was dedicated to constructing high quality hexahedral meshes, which were previously shown to be more efficient and more accurate compared with the tetrahedral or hybrid cell approach that is frequently employed. (81,82) Beyond the third bifurcation, stochastic individual path (SIP) models were considered extending into the lung lobes (Fig.…”

“…The relevant governing transport equations are solved in 3D models of the airways, which are discretized into interconnected small spatial elements (or control volumes) such as hexahedral, tetrahedral, or prism cells. Recent CFD studies of inhaled pharmaceutical aerosols have captured the effects of inhalers on transport and deposition in the mouth-throat region (34)(35)(36) and have predicted aerosol deposition through numerous generations of the upper (37)(38)(39) and lower TB airways. (40) However, prediction of aerosol transport and deposition throughout the lungs with CFD simulations (i.e., a CFD whole-lung model) remains challenging and requires simplifying techniques, which are actively being developed.…”

Effect of Lung Inflation Level on Hyperpolarized3He Apparent Diffusion Coefficient Measurements in Never-Smokers

“…Similarly, computational fluid dynamics simulations have suggested increased flow patterns in the right lung airway geometries with respect to the left equivalents, possibly owing to differences in airway geometries between the two main branches (30).…”

Large Eddy Simulation of Titanium Dioxide Nanoparticle Formation and Growth in Turbulent Jets

“…However, since only the effects of the small scales are modeled in LES the closure uncertainties at such scales are less damaging than those in RANS in which modeling is applied at all scales. While there has been significant progress in development and implementation of LES in turbulent, single-phase flows, comparatively little has been done in its utilization in turbulent aerosols (Lumley 1990;Moin 1991;Jaberi et al 1999;Gicquel et al 2002;Givi 2006;Lambert et al 2011). There have been recent efforts towards the simulation of nanoparticle dynamics in turbulent flows.…”