Prediction of airway deformation effect on pulmonary air-particle dynamics: A numerical study (original) (raw)
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Applied Sciences, 2017
The trajectory and deposition efficiency of micron-sized (1-5 µm) particles, inhaled into the pulmonary system, are accurately determined with the aid of a newly developed model and modified simulation techniques. This alveolar model, which has a simple but physiologically appropriate geometry, and the utilized fluid structure interaction (FSI) methods permit the precise simulation of tissue wall deformation and particle fluid interactions. The relation between tissue movement and airflow in the alveolated duct is solved by a two-way fluid structure interaction simulation technique, using ANSYS Workbench (Release 16.0, ANSYS INC., Pittsburgh, PA, USA, 2015). The dynamic transport of particles and their deposition are investigated as a function of aerodynamic particle size, tissue visco-elasticity, tidal breathing period, gravity orientation and particle-fluid interactions. It is found that the fluid flows and streamlines differ between the present flexible model and rigid models, and the two-way coupling particle trajectories vary relative to one-way particle coupling. In addition, the results indicate that modelling the two-way coupling particle system is important because the two-way discrete phase method (DPM) approach despite its complexity provides more extensive particle interactions and is more reliable than transport results from the one-way DPM approach. The substantial difference between the results of the two approaches is likely due to particle-fluid interactions, which re-suspend the sediment particles in the airway stream and hence pass from the current generation.
Computational and Mathematical Methods in Medicine
This study aims to investigate the effect of altered structures and functions in severe asthma on particle deposition by using computational fluid dynamics (CFD) models. Airway geometrical models of two healthy subjects and two severe asthmatics were reconstructed from computed tomography (CT) images. Subject-specific flow boundary conditions were obtained by image registration to account for regional functional alterations of severe asthmatics. A large eddy simulation (LES) model for transitional and turbulent flows was applied to simulate airflows, and particle transport simulations were then performed for 2.5, 5, and 10 μm particles using CFD-predicted flow fields. Compared to the healthy subjects, the severe asthmatics had a smaller air-volume change in the lower lobes and a larger air-volume change in the upper lobes. Both severe asthmatics had smaller airway circularity (Cr), but one of them had a significant reduction of hydraulic diameter (Dh). In severe asthmatics, the larg...
Drug Development and Industrial Pharmacy, 2019
Dry powder inhalers (DPIs) are considered a main drug delivery system through pulmonary route. The main objective of this work is to study the flow of differently shaped microparticles in order to find the optimum shape of drug particles that will demonstrate the best flow to the deep lung. The flowability of particles in air or any fluid depends particularly on the drag force which is defined as the resistance of the fluid molecules to the particle flow. One of the most important parameters that affect the drag force is the particles' shape. Computational simulations using COMSOL Multi Physics 5.2 software were performed for investigating the particles flow in the air pathways of lung, and the drag force was calculated for different particles shapes. This was accomplished by screening a set of 17 possible shapes that are expected to be synthesized easily in the micro-scale. In addition, the macro-scale behavior of the investigated shapes was also simulated so as to compare the behavior of the flowing particles in both cases. A very big difference was found between the behavior of particles' flow in the micro and macro scales, but a similar behavior can be obtained if the flow velocity of the microparticles is very high. It was also found that the micro-triangle with aspect ratio 2:1 has the least drag force in both deep and upper lung; so, it should be the shape of choice during the process of particle synthesis for pulmonary drug delivery.
Journal of Aerosol Science, 2021
Dynamic modeling of how particulate matter (PM) transport, deposit, and translocate from human respiratory systems to systemic regions subject to indoor and outdoor exposures are essential for case-specific lung dosimetry predictions and occupational health risk assessments. Because of the invasive nature and imaging resolution limitations of existing in vitro and in vivo methods, Computational Fluid-Particle Dynamics plus Physiologically Based Pharmacokinetic/ Toxicokinetic (CFPD-PBPK/TK) models have been employed to predict the fate of the respirable aerosols for decades. This paper presents a guide on how to use the multiscale CFPD-PBPK/TK models to predict lung dosimetry and systemic translocations quantitatively with 3D subjectspecific human respiratory systems. The tutorial aims to clarify possibly ambiguous concepts. The step-by-step modeling procedure should help researchers set up the CFPD-PBPK/TK model accurately, following the standard model validation and verification (V&V) processes, and to bring the lung dosimetry predictions to health endpoints. Starting from the fundamentals of CFPD and PBPK/TK governing equations, the tutorial covers the problem identification, pre-processing, solving, and post-processing steps to perform a computational lung aerosol dynamics simulations, emphasizing on (a) the importance of correct reconstruction and mesh generation of the pulmonary airways; (b) the significance of choosing the appropriate turbulence model to predict the laminar-to-turbulence pulmonary airflow regimes; and (c) the standard (V&V) procedures of submodels in the CFPD-PBPK/TK modeling framework. The tutorial also highlights the deficiencies of current CFPD-PBPK/TK models, clarifies the missing biomechanisms and aerosol dynamics in the respiratory systems that need to be considered to build the next-generation virtual human whole-lung models.
Numerical Simulation of Particle Transport and Deposition in the Pulmonary Vasculature
Journal of Biomechanical Engineering, 2014
To quantify the transport and adhesion of drug particles in a complex vascular environment, computational fluid particle dynamics (CFPD) simulations of blood flow and drug particulate were conducted in three different geometries representing the human lung vasculature for steady and pulsatile flow conditions. A fully developed flow profile was assumed as the inlet velocity, and a lumped mathematical model was used for the calculation of the outlet pressure boundary condition. A receptor-ligand model was used to simulate the particle binding probability. The results indicate that bigger particles have lower deposition fraction due to less chance of successful binding. Realistic unsteady flow significantly accelerates the binding activity over a wide range of particle sizes and also improves the particle deposition fraction in bifurcation regions when comparing with steady flow condition. Furthermore, surface imperfections and geometrical complexity coupled with the pulsatility effect can enhance fluid mixing and accordingly particle binding efficiency. The particle binding density at bifurcation regions increases with generation order and drug carriers are washed away faster in steady flow. Thus, when studying drug delivery mechanism in vitro and in vivo, it is important to take into account blood flow pulsatility in realistic geometry. Moreover, tissues close to bifurcations are more susceptible to deterioration due to higher uptake.
Numerical Modeling of Deposition of Inhaled Particles in Central Human Airways
Annals of Occupational Hygiene, 2002
The objective of our research is to model physical and biological processes related to the development of adverse health effects, especially initiation of lung cancer in the central human airways following inhalation of aerosol particles. There is experimental evidence that bronchogenic carcinomas originate mainly at the dividing zone of large central airway bifurcations where primary hotspots of deposition have been found. However, current lung deposition models do not take into consideration the inhomogeneity of deposition within bronchial airways. The flow field within three-dimensional morphologically realistic geometries of airway generations 3-6 of the human tracheobronchial tree is computed by the FLUENT CFD (computational fluid dynamics) code for a wide range of flow rates during both inhalation and exhalation. A large number of particle trajectories has been simulated to determine the resulting deposition patterns, which were finally quantified by local deposition enhancement factors. Both the local airflow fields and deposition patterns strongly depend on the shape of the geometry, especially on the form of the carinal ridge. The computed enhancement factors indicate that local deposition densities may be two orders of magnitude higher than the average values for scanning on the surface by a 100 × 100 µm surface element, i.e. at approximately cellular dimensions.
BMC medical informatics and decision making, 2017
Chronic obstructive pulmonary disease (COPD) and asthma are considered as the two most widespread obstructive lung diseases, whereas they affect more than 500 million people worldwide. Unfortunately, the requirement for detailed geometric models of the lungs in combination with the increased computational resources needed for the simulation of the breathing did not allow great progress to be made in the past for the better understanding of inflammatory diseases of the airways through detailed modelling approaches. In this context, computational fluid dynamics (CFD) simulations accompanied by fluid particle tracing (FPT) analysis of the inhaled ambient particles are deemed critical for lung function assessment. Also they enable the understanding of particle depositions on the airways of patients, since these accumulations may affect or lead to inflammations. In this direction, the current study conducts an initial investigation for the better comprehension of particle deposition with...
2019
In the present study, the realistic model of the human trachea with five generations that are obtained from computerized tomography scan images is considered. Due to the complexity of lung geometry, many researchers have used simple models. Therefore in the present study realistic model with all geometrical details are considered. The airflow behavior, particle transport and deposition in various conditions such as steady flow, transient flow, light breathing and heavy breathing condition for various micro-particles diameters are investigated. Governing equations are solved and obtained results show that the flow patterns in the realistic model are much more complicated than those of symmetrical models. Also, the particle deposition pattern in the realistic condition is very different from that of the symmetrical model and the details of the trachea are very important and affect the deposition fractions in the small airways. Also, results show that the turbulent effect should be cou...
It is recognised that knowledge of air flow characteristics in the tracheo-bronchial tree was essential to the understanding of airway resistance, intrapulmonary gas mixing, and deposition of airborne particles. Numerical and mathematical methods had previously been used extensively to obtain particle deposition patterns inside a single airway and various regions of the human lung for a range of physiological conditions. However, detailed analysis of particle deposition, in asymmetrical human upper airways, under transient conditions, had not been uncovered in published literature at the time this research commenced. In this research study, a commercial CFD package, called "CFX Workbench 11" was deployed to analyze flow fields, transient flow and particle deposition. This research work was an extension to earlier research published in 2008 by the authors here. The airway geometry applied in this current research was created by closely following the values published by another researcher (Horsfield), where the transient flows for three different breathing cycles were used as the input boundary conditions. The findings of the modelling presented herein indicated that the release position did not vary significantly at different time steps or with changes in particle size, but it did vary significantly with breathing patterns. Moreover, the rate of particle deposition at the wall was found to increase with the rising of the branching angles.