Effectiveness of Direct Lagrangian Tracking Models for Simulating Nanoparticle Deposition in the Upper Airways

Longest, P. Worth; Xi, Jinxiang

doi:10.1080/02786820701203223

Cited by 208 publications

(163 citation statements)

References 62 publications

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“…To address this broad range of particle sizes, a previously developed and optimized Lagrangian particle tracking method was employed. (88,89) To model the effects of turbulent fluctuations on particle trajectories, a random walk method was implemented. (90) The primary limitation of this eddy interaction model in FIG.…”

Section: Cfd Simulationsmentioning

confidence: 99%

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

Longest

Tian

Khajeh-Hosseini-Dalasm

et al. 2016

Journal of Aerosol Medicine and Pulmonary Drug Delivery

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Background: The objective of this study was to compare aerosol deposition predictions of a new whole-airway CFD model with available in vivo data for a dry powder inhaler (DPI) considered across multiple inhalation waveforms, which affect both the particle size distribution (PSD) and particle deposition. Methods: The Novolizer DPI with a budesonide formulation was selected based on the availability of 2D gamma scintigraphy data in humans for three different well-defined inhalation waveforms. Initial in vitro cascade impaction experiments were conducted at multiple constant (square-wave) particle sizing flow rates to characterize PSDs. The whole-airway CFD modeling approach implemented the experimentally determined PSDs at the point of aerosol formation in the inhaler. Complete characteristic airway geometries for an adult were evaluated through the lobar bronchi, followed by stochastic individual pathway (SIP) approximations through the tracheobronchial region and new acinar moving wall models of the alveolar region. Results: It was determined that the PSD used for each inhalation waveform should be based on a constant particle sizing flow rate equal to the average of the inhalation waveform's peak inspiratory flow rate (PIFR) and mean flow rate [i.e., AVG(PIFR, Mean)]. Using this technique, agreement with the in vivo data was acceptable with <15% relative differences averaged across the three regions considered for all inhalation waveforms. Defining a peripheral to central deposition ratio (P/C) based on alveolar and tracheobronchial compartments, respectively, large flow-rate-dependent differences were observed, which were not evident in the original 2D in vivo data. Conclusions: The agreement between the CFD predictions and in vivo data was dependent on accurate initial estimates of the PSD, emphasizing the need for a combination in vitro-in silico approach. Furthermore, use of the AVG(PIFR, Mean) value was identified as a potentially useful method for characterizing a DPI aerosol at a constant flow rate.

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Section: Cfd Simulationsmentioning

confidence: 99%

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

Longest

Tian

Khajeh-Hosseini-Dalasm

et al. 2016

Journal of Aerosol Medicine and Pulmonary Drug Delivery

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“…Previously developed near-wall corrections for interpolating velocity and directionally dependent turbulence were included. 22,24 Due to the use of humidified air flow in the experiments, droplet evaporation was not included in the model, resulting in the simulation of particle trajectories with unchanging diameters. However, the overall MMAD of the polydisperse aerosol changes as the polydisperse particles move through the system and are selectively filtered by deposition.…”

Section: Cfd Simulationsmentioning

confidence: 99%

Improving Aerosol Drug Delivery During Invasive Mechanical Ventilation With Redesigned Components

Pw¹,

Azimi

Golshahi

et al. 2013

Respir Care

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INTRODUCTION:Patients receiving invasive mechanical ventilation with an endotracheal tube (ETT) can often benefit from pharmaceutical aerosols; however, drug delivery through the ventilator circuit is known to be very inefficient. The objective of this study was to improve the delivery of aerosol through an invasive mechanical ventilation system by redesigning circuit components using a streamlining approach. METHODS: Redesigned components were the T-connector interface between the nebulizer and ventilator line and the Y-connector leading to the ETT. The streamlining approach seeks to minimize aerosol deposition and loss by eliminating sharp changes in flow direction and tubing diameter that lead to flow disruption. Both in vitro experiments and computational fluid dynamic (CFD) simulations were applied to analyze deposition and emitted dose of drug for multiple droplet size distributions, flows, and ETT sizes used in adults. RESULTS: The experimental results demonstrated that the streamlined components improved delivery through the circuit by factors ranging from 1.3 to 1.5 compared with a commercial system for adult ETT sizes of 8 and 9 mm. The overall delivery efficiency was based on the bimodal aspect of the aerosol distributions and could not be predicted by median diameter alone. CFD results indicated a 20-fold decrease in turbulence in the junction region for the streamlined Y resulting in a maximum 9-fold decrease in droplet deposition. The relative effectiveness of the streamlined designs was found to increase with increasing particle size and increasing flow, with a maximum improvement in emitted dose of 1.9-fold. CONCLUSIONS: Streamlined components can significantly improve the delivery of pharmaceutical aerosols during mechanical ventilation based on an analysis of multiple aerosol generation devices, ETT sizes, and flows.

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“…Particle tracking was performed using a Lagrangian approach including terms for drag, gravity, and Brownian motion. (30) The turbulent dispersion of particles was included in both determining the coupled flow-field solution and aerosol deposition. Anisotropic corrections of near-wall turbulence were used to improve the accuracy of the deposition predictions.…”

mentioning

confidence: 99%

“…(24) The commercial CFD package Fluent 12 (ANSYS, Inc., Canonsburg, PA) was used to solve the governing equations in all cases considered. User-supplied Fortran and C programs were implemented for the calculation of initial flow and droplet profiles, hygroscopic droplet evaporation, nearwall anisotropic turbulence approximations, near-wall particle interpolation, (30) Brownian motion, (30) as well as heat and mass sources and sinks during two-way coupling. CFD best practices were used including the use of second or higher order discretization, hexahedral grids, (33) and doubleprecision calculations.…”

mentioning

confidence: 99%

High-Efficiency Generation and Delivery of Aerosols Through Nasal Cannula During Noninvasive Ventilation

Longest

Walenga

Son

et al. 2013

Journal of Aerosol Medicine and Pulmonary Drug Delivery

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Background: Previous studies have demonstrated the delivery of pharmaceutical aerosols through nasal cannula and the feasibility of enhanced condensational growth (ECG) with a nasal interface. The objectives of this study were to develop a device for generating submicrometer aerosols with minimal depositional loss in the formation process and to improve aerosol delivery efficiencies through nasal cannulas. Methods: A combination of in vitro experiments and computational fluid dynamics (CFD) simulations that used the strengths of each method was applied. Aerosols were formed using a conventional mesh nebulizer, mixed with ventilation gas, and heated to produce submicrometer sizes. An improved version of the mixer and heater unit was developed based on CFD simulations, and performance was verified with experiments. Aerosol delivery was considered through a commercial large-bore adult cannula, a divided (D) design for use with ECG, and a divided and streamlined (DS) design. Results: The improved mixer design reduced the total deposition fraction (DF) of drug within the mixer by a factor of 3 compared with an initial version, had a total DF of approximately 10%, and produced submicrometer aerosols at flow rates of 10 and 15 L/min. Compared with the commercial and D designs for submicrometer aerosols, the DS cannula reduced depositional losses by a factor of 2-3 and retained only approximately 5% or less of the nebulized dose at all flow rates considered. For conventional-sized aerosols (3.9 and 4.7 lm), the DS device provided delivery efficiencies of approximately 80% and above at flow rates of 2-15 L/min. Conclusions: Submicrometer aerosols can be formed using a conventional mesh nebulizer and delivered through a nasal cannula with total delivery efficiencies of 80-90%. Streamlining the nasal cannula significantly improved the delivery efficiency of both submicrometer and micrometer aerosols; however, use of submicrometer particles with ECG delivery resulted in overall lower depositional losses.

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Effectiveness of Direct Lagrangian Tracking Models for Simulating Nanoparticle Deposition in the Upper Airways

Cited by 208 publications

References 62 publications

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

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

Improving Aerosol Drug Delivery During Invasive Mechanical Ventilation With Redesigned Components

High-Efficiency Generation and Delivery of Aerosols Through Nasal Cannula During Noninvasive Ventilation

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