Transport and deposition of respiratory aerosols in models of childhood asthma

Longest, P. Worth; Vinchurkar, Samir; Martonen, T. B.

doi:10.1016/j.jaerosci.2006.01.011

Cited by 106 publications

(73 citation statements)

References 77 publications

(107 reference statements)

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“…70 Longest and Oldham 28 showed that it was necessary to accurately model upstream flow and particle conditions in order to match the experimentally reported deposition data of 1 lm aerosols in a double bifurcations model. 45 Longest et al 31 reported good agreement between numerical simulations and the empirical data of Kim and Fisher 23 for Stokes numbers ranging from 0.02 to 0.2. For 10 lm particles, Longest and Vinchurkar 30 reported good agreement with the localized cumulative deposition data of Oldham et al 45 for a physiologically realistic bifurcation model of respiratory generations G3-G5.…”

Section: Model Testingmentioning

confidence: 85%

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Transport and Deposition of Micro-Aerosols in Realistic and Simplified Models of the Oral Airway

2007

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A number of in vivo, in vitro and numerical studies have considered flow field characteristics and micro-particle deposition in the oral airway extending from the mouth through the larynx. These studies have highlighted the effects of flow rates, turbulence and particle characteristics on deposition values in realistic and simplified geometries. However, the effect of geometry simplifications on regional and local deposition patterns remains largely un-quantified for the oral airway and throughout the respiratory tract. The objective of this study is to assess the effects of geometry simplifications on regionally averaged and local micro-aerosol deposition characteristics in models of the extrathoracic oral airway. To achieve this objective, a realistic model of the oral airway has been constructed based on CT scans of a healthy adult in conjunction with measurements reported in the literature. Three other geometries with descending degrees of physical realism were constructed based on successive geometric simplifications of the realistic model. A validated low Reynolds number (LRN) k-omega turbulence model was employed to simulate laminar, transitional and fully turbulent flow regimes for 1-31 microm particles. Geometric simplifications were found to have a significant effect on aerosol dynamics, hot spot formations and cellular-level deposition values in the extrathoracic airway models considered. For all models, regional deposition efficiency results were found to be approximately within one standard deviation of available experimental data when plotted as a function of Stokes number. The realistic geometry provided the best predictions of regional deposition in comparison to experimental data as a function of particle diameter. Considering localized deposition, maximum deposition enhancement factors, which represent the ratio of local to total deposition, were one to two orders of magnitude higher for the realistic model. Geometric factors that significantly contributed to enhanced particle localization in the realistic model include a triangular-shaped glottis and a dorsal-sloped trachea. Therefore, highly realistic models of the oral airway geometry may be necessary to evaluate localized deposition patterns and hot spot formations, which are critical for accurately predicting cellular-level dose.

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Section: Model Testingmentioning

confidence: 85%

“…33 This prescribed area is consistent with the localized areas considered by other researchers. 3,4,31,64 However, the definition of the DEF in this study is for a pre-specified constant area at each sampling location. Sampling locations are taken to be nodal points.…”

Section: Deposition Factorsmentioning

confidence: 99%

Transport and Deposition of Micro-Aerosols in Realistic and Simplified Models of the Oral Airway

2007

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“…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. (41)(42)(43)(44) CFD predictions of pharmaceutical aerosol deposition in the upper airways have successfully resulted in correlations of deposition that are integrated into semi-empirical and 1D whole lung models.…”

Section: Introductionmentioning

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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“…Nowadays, it is generally accepted that full 3D computational modeling using CFD codes is suitable and very useful when seeking information about local deposition (Longest et al 2006). The flow in the airways of the respiratory tract is typically turbulent, transitional laminar/turbulent and laminar, depending on the inlet flow rate and on the branching generation.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of inspiratory airflow in a realistic model of the human tracheobronchial airways and a comparison with experimental results

Elcner

Lízal

Jedelský

et al. 2015

Biomech Model Mechanobiol

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In this article, the results of numerical simulations using computational fluid dynamics (CFD) and a comparison with experiments performed with phase Doppler anemometry are presented. The simulations and experiments were conducted in a realistic model of the human airways, which comprised the throat, trachea and tracheobronchial tree up to the fourth generation. A full inspiration/expiration breathing cycle was used with tidal volumes 0.5 and 1 L, which correspond to a sedentary regime and deep breath, respectively. The length of the entire breathing cycle was 4 s, with inspiration and expiration each lasting 2 s. As a boundary condition for the CFD simulations, experimentally obtained flow rate distribution in 10 terminal airways was used with zero pressure resistance at the throat inlet. CCM+ CFD code (Adapco) was used with an SST k-ω low-Reynolds Number RANS model. The total number of polyhedral control volumes was 2.6 million with a time step of 0.001 s. Comparisons were made at several points in eight cross sections selected according to experiments in the trachea and the left and right bronchi. The results agree well with experiments involving the oscillation (temporal relocation) of flow structures in the majority of the cross sections and individual local positions. Velocity field simulation in several cross sections shows a very unstable flow field, which originates in the tracheal laryngeal jet and propagates far downstream with the formation of separation zones in both left and right airways. The RANS simulation agrees with the experiments in almost all the cross sections and shows unstable local flow structures and a quantitatively acceptable solution for the time-averaged flow field.

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Transport and deposition of respiratory aerosols in models of childhood asthma

Cited by 106 publications

References 77 publications

Transport and Deposition of Micro-Aerosols in Realistic and Simplified Models of the Oral Airway

Transport and Deposition of Micro-Aerosols in Realistic and Simplified Models of the Oral Airway

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

Numerical investigation of inspiratory airflow in a realistic model of the human tracheobronchial airways and a comparison with experimental results

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