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Oakes JM. The utility of hybrid in silico models of airflow and aerosol dosimetry in the lung. J Biomech 2024; 168:112126. [PMID: 38718595 DOI: 10.1016/j.jbiomech.2024.112126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 04/19/2024] [Accepted: 04/25/2024] [Indexed: 06/05/2024]
Abstract
The development and application of multi-scale models of the lung has significantly increased in recent years. These hybrid models merge realistic representations of the larger airways with lower-dimensional descriptions of the bronchioles and respiratory airways. Due to recent advancements, it is possible to calculate airflow and dosimetry throughout the entire lung, enabling model validation with human or animal data. Here, we present a hybrid modeling pipeline and corresponding characteristic airflow and particle deposition hotspots. Next, we discuss the limitations of current hybrid models, including the need to update lower-dimensional deposition function descriptions to better represent realistic airway geometries. Future directions should include modeling diseased lungs and use of machine learning to predict whole lung dosimetry maps for a wider population.
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Affiliation(s)
- Jessica M Oakes
- Department of Bioengineering, Northeastern University, Boston, MA 02115.
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2
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Schwarz EL, Pegolotti L, Pfaller MR, Marsden AL. Beyond CFD: Emerging methodologies for predictive simulation in cardiovascular health and disease. BIOPHYSICS REVIEWS 2023; 4:011301. [PMID: 36686891 PMCID: PMC9846834 DOI: 10.1063/5.0109400] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 12/12/2022] [Indexed: 01/15/2023]
Abstract
Physics-based computational models of the cardiovascular system are increasingly used to simulate hemodynamics, tissue mechanics, and physiology in evolving healthy and diseased states. While predictive models using computational fluid dynamics (CFD) originated primarily for use in surgical planning, their application now extends well beyond this purpose. In this review, we describe an increasingly wide range of modeling applications aimed at uncovering fundamental mechanisms of disease progression and development, performing model-guided design, and generating testable hypotheses to drive targeted experiments. Increasingly, models are incorporating multiple physical processes spanning a wide range of time and length scales in the heart and vasculature. With these expanded capabilities, clinical adoption of patient-specific modeling in congenital and acquired cardiovascular disease is also increasing, impacting clinical care and treatment decisions in complex congenital heart disease, coronary artery disease, vascular surgery, pulmonary artery disease, and medical device design. In support of these efforts, we discuss recent advances in modeling methodology, which are most impactful when driven by clinical needs. We describe pivotal recent developments in image processing, fluid-structure interaction, modeling under uncertainty, and reduced order modeling to enable simulations in clinically relevant timeframes. In all these areas, we argue that traditional CFD alone is insufficient to tackle increasingly complex clinical and biological problems across scales and systems. Rather, CFD should be coupled with appropriate multiscale biological, physical, and physiological models needed to produce comprehensive, impactful models of mechanobiological systems and complex clinical scenarios. With this perspective, we finally outline open problems and future challenges in the field.
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Affiliation(s)
- Erica L. Schwarz
- Departments of Pediatrics and Bioengineering, Stanford University, Stanford, California 94305, USA
| | - Luca Pegolotti
- Departments of Pediatrics and Bioengineering, Stanford University, Stanford, California 94305, USA
| | - Martin R. Pfaller
- Departments of Pediatrics and Bioengineering, Stanford University, Stanford, California 94305, USA
| | - Alison L. Marsden
- Departments of Pediatrics and Bioengineering, Stanford University, Stanford, California 94305, USA
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Ciloglu D, Karaman A. A Numerical Simulation of the Airflow and Aerosol Particle Deposition in a Realistic Airway Model of a Healthy Adult. J Pharm Sci 2022; 111:3130-3140. [PMID: 35948158 DOI: 10.1016/j.xphs.2022.08.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 08/04/2022] [Accepted: 08/04/2022] [Indexed: 12/14/2022]
Abstract
Determining the behavior of aerosol drug particles is of vital importance in the treatment of respiratory tract diseases. Despite the development of imaging techniques in the pulmonary region in recent years, current imaging techniques are insufficient to detect particle deposition. Computational fluid dynamics (CFD) methods can fill the gap in this field as they take into account the very different physical processes that occur during aerosol transport. This study aims to numerically investigate the airflow and the aerosol particle dynamics on a realistic human respiratory tract model during multiple breathing cycles. The simulations were conducted on the different breathing conditions for people under light, normal, and heavy physical activities, and the aerosol particles with different aerodynamic diameters (i.e., dp=2, 5, and 7 µm). The numerical results were validated by comparing extensively with experimental and numerical results. The results indicated that the airflow during inspiration and expiration was characteristically different from each other and changed with the inspiration flow rate. It was determined that small-sized particles followed the streamlines and moved towards the distal of the lung under low respiratory conditions. On the other hand, larger particles tended to deposit in higher generations due to the higher inertia. It was found that with the increase of inspiration flow rate the deposition of particles increased for all particles during multiple breaths. For light breathing conditions, low deposition efficiencies were obtained because the particles followed the streamlines and moved towards the distal part of the lung. The particle deposition efficiency under heavy breathing conditions was 28.2% for 2 µm, 33.05% for 5 µm, and 38.4% for 7 µm particles. The results showed that inertial impaction plays an active role in particle deposition.
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Affiliation(s)
- Dogan Ciloglu
- Vocational College of Technical Sciences, Ataturk University, Erzurum, Turkey.
| | - Adem Karaman
- Department of Radiology, Faculty of Medicine, Ataturk University, 25240 Erzurum, Turkey
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Darquenne C, Borojeni AA, Colebank MJ, Forest MG, Madas BG, Tawhai M, Jiang Y. Aerosol Transport Modeling: The Key Link Between Lung Infections of Individuals and Populations. Front Physiol 2022; 13:923945. [PMID: 35795643 PMCID: PMC9251577 DOI: 10.3389/fphys.2022.923945] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 05/24/2022] [Indexed: 12/18/2022] Open
Abstract
The recent COVID-19 pandemic has propelled the field of aerosol science to the forefront, particularly the central role of virus-laden respiratory droplets and aerosols. The pandemic has also highlighted the critical need, and value for, an information bridge between epidemiological models (that inform policymakers to develop public health responses) and within-host models (that inform the public and health care providers how individuals develop respiratory infections). Here, we review existing data and models of generation of respiratory droplets and aerosols, their exhalation and inhalation, and the fate of infectious droplet transport and deposition throughout the respiratory tract. We then articulate how aerosol transport modeling can serve as a bridge between and guide calibration of within-host and epidemiological models, forming a comprehensive tool to formulate and test hypotheses about respiratory tract exposure and infection within and between individuals.
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Affiliation(s)
- Chantal Darquenne
- Department of Medicine, University of California, San Diego, San Diego, CA, United States
- *Correspondence: Chantal Darquenne,
| | - Azadeh A.T. Borojeni
- Department of Medicine, University of California, San Diego, San Diego, CA, United States
| | - Mitchel J. Colebank
- Edwards Lifesciences Foundation Cardiovascular Innovation and Research Center and Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, United States
| | - M. Gregory Forest
- Departments of Mathematics, Applied Physical Sciences, and Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Balázs G. Madas
- Environmental Physics Department, Centre for Energy Research, Budapest, Hungary
| | - Merryn Tawhai
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Yi Jiang
- Department of Mathematics and Statistics, Georgia State University, Atlanta, GA, United States
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Ehrmann S, Schmid O, Darquenne C, Rothen-Rutishauser B, Sznitman J, Yang L, Barosova H, Vecellio L, Mitchell J, Heuze-Vourc’h N. Innovative preclinical models for pulmonary drug delivery research. Expert Opin Drug Deliv 2020; 17:463-478. [PMID: 32057260 PMCID: PMC8083945 DOI: 10.1080/17425247.2020.1730807] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 02/11/2020] [Indexed: 02/08/2023]
Abstract
Introduction: Pulmonary drug delivery is a complex field of research combining physics which drive aerosol transport and deposition and biology which underpins efficacy and toxicity of inhaled drugs. A myriad of preclinical methods, ranging from in-silico to in-vitro, ex-vivo and in-vivo, can be implemented.Areas covered: The present review covers in-silico mathematical and computational fluid dynamics modelization of aerosol deposition, cascade impactor technology to estimated drug delivery and deposition, advanced in-vitro cell culture methods and associated aerosol exposure, lung-on-chip technology, ex-vivo modeling, in-vivo inhaled drug delivery, lung imaging, and longitudinal pharmacokinetic analysis.Expert opinion: No single preclinical model can be advocated; all methods are fundamentally complementary and should be implemented based on benefits and drawbacks to answer specific scientific questions. The overall best scientific strategy depends, among others, on the product under investigations, inhalation device design, disease of interest, clinical patient population, previous knowledge. Preclinical testing is not to be separated from clinical evaluation, as small proof-of-concept clinical studies or conversely large-scale clinical big data may inform preclinical testing. The extend of expertise required for such translational research is unlikely to be found in one single laboratory calling for the setup of multinational large-scale research consortiums.
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Affiliation(s)
- Stephan Ehrmann
- CHRU Tours, Médecine Intensive Réanimation, CIC INSERM 1415, CRICS-TriggerSep network, Tours France
- INSERM, Centre d’étude des pathologies respiratoires, U1100, Tours, France
- Université de Tours, Tours, France
| | - Otmar Schmid
- Comprehensive Pneumology Center (CPC-M), German Center for Lung Research (DZL), Max-Lebsche-Platz 31, 81377 Munich, Germany
- Institute of Lung Biology and Disease, Helmholtz Zentrum München – German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany
| | - Chantal Darquenne
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, MC0623A, La Jolla, CA 92093-0623, United States
| | | | - Josue Sznitman
- Department of Biomedical Engineering, Technion - Israel Institute of Technology, Julius Silver building, Office 246, Haifa 32000, Israel
| | - Lin Yang
- Comprehensive Pneumology Center (CPC-M), German Center for Lung Research (DZL), Max-Lebsche-Platz 31, 81377 Munich, Germany
- Institute of Lung Biology and Disease, Helmholtz Zentrum München – German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany
| | - Hana Barosova
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, Fribourg, Switzerland
| | - Laurent Vecellio
- INSERM, Centre d’étude des pathologies respiratoires, U1100, Tours, France
- Université de Tours, Tours, France
| | - Jolyon Mitchell
- Jolyon Mitchell Inhaler Consulting Services Inc., 1154 St. Anthony Road, London, Ontario, Canada, N6H 2R1
| | - Nathalie Heuze-Vourc’h
- INSERM, Centre d’étude des pathologies respiratoires, U1100, Tours, France
- Université de Tours, Tours, France
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Sul B, Oppito Z, Jayasekera S, Vanger B, Zeller A, Morris M, Ruppert K, Altes T, Rakesh V, Day S, Robinson R, Reifman J, Wallqvist A. Assessing Airflow Sensitivity to Healthy and Diseased Lung Conditions in a Computational Fluid Dynamics Model Validated In Vitro. J Biomech Eng 2019; 140:2668581. [PMID: 29305603 DOI: 10.1115/1.4038896] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Indexed: 12/16/2022]
Abstract
Computational models are useful for understanding respiratory physiology. Crucial to such models are the boundary conditions specifying the flow conditions at truncated airway branches (terminal flow rates). However, most studies make assumptions about these values, which are difficult to obtain in vivo. We developed a computational fluid dynamics (CFD) model of airflows for steady expiration to investigate how terminal flows affect airflow patterns in respiratory airways. First, we measured in vitro airflow patterns in a physical airway model, using particle image velocimetry (PIV). The measured and computed airflow patterns agreed well, validating our CFD model. Next, we used the lobar flow fractions from a healthy or chronic obstructive pulmonary disease (COPD) subject as constraints to derive different terminal flow rates (i.e., three healthy and one COPD) and computed the corresponding airflow patterns in the same geometry. To assess airflow sensitivity to the boundary conditions, we used the correlation coefficient of the shape similarity (R) and the root-mean-square of the velocity magnitude difference (Drms) between two velocity contours. Airflow patterns in the central airways were similar across healthy conditions (minimum R, 0.80) despite variations in terminal flow rates but markedly different for COPD (minimum R, 0.26; maximum Drms, ten times that of healthy cases). In contrast, those in the upper airway were similar for all cases. Our findings quantify how variability in terminal and lobar flows contributes to airflow patterns in respiratory airways. They highlight the importance of using lobar flow fractions to examine physiologically relevant airflow characteristics.
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Affiliation(s)
- Bora Sul
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, MD 21702
| | - Zachary Oppito
- Mechanical Engineering Department, Rochester Institute of Technology, Rochester, NY 14623
| | - Shehan Jayasekera
- Mechanical Engineering Department, Rochester Institute of Technology, Rochester, NY 14623
| | - Brian Vanger
- Mechanical Engineering Department, Rochester Institute of Technology, Rochester, NY 14623
| | - Amy Zeller
- Mechanical Engineering Department, Rochester Institute of Technology, Rochester, NY 14623
| | - Michael Morris
- Department of Medicine, San Antonio Military Medical Center, JBSA Fort Sam Houston, San Antonio, TX 78234
| | - Kai Ruppert
- Radiology Department, University of Pennsylvania, Philadelphia, PA 19104
| | - Talissa Altes
- Department of Radiology, University of Missouri, Columbia, MO 65211
| | - Vineet Rakesh
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, MD 21702
| | - Steven Day
- Mechanical Engineering Department, Rochester Institute of Technology, Rochester, NY 14623
| | - Risa Robinson
- Mechanical Engineering Department, Rochester Institute of Technology, Rochester, NY 14623
| | - Jaques Reifman
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, MD 21702 e-mail:
| | - Anders Wallqvist
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, MD 21702
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Poorbahrami K, Oakes JM. Regional flow and deposition variability in adult female lungs: A numerical simulation pilot study. Clin Biomech (Bristol, Avon) 2019; 66:40-49. [PMID: 29395490 DOI: 10.1016/j.clinbiomech.2017.12.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 12/18/2017] [Accepted: 12/30/2017] [Indexed: 02/07/2023]
Abstract
BACKGROUND Despite the promise of respiratory simulations improving diagnosis and treatment of pulmonary diseases, model predictions have yet to be translated into the clinical setting. Current state-of-the-art in silico models have not yet incorporated subject variability in their predictions of airflow distributions and extent of deposited particles. Until inter-subject variability is accounted for in lung modeling, it will remain impossible to translate model predictions into clinical practice. METHODS Airflow and particle trajectories (dp=1,3,5μm) are calculated in three subject-specific female adults by performing physiologically-based simulations. The computation framework features the ability to track air and particles throughout the respiration cycle and in the entire lung. Airway resistances, air velocities, and local deposition sites are correlated to airway anatomical features. FINDINGS Smaller airway diameters are correlated to larger airway resistances and pressure gradients in one subject compared to the other two. Irregular shape of the airway and flow direction (e.g. inspiration or expiration) correspond with peak velocities and secondary flow motions. Largest subject variability in deposition between conducting and respiratory zones is seen for 1 μm diameter particles. Little difference in total deposition is found among subjects. Localized deposited particle concentration hotspots are linked to airway anatomy and flow motion. INTERPRETATION Simulation predictions provide a first look into the correlation of anatomical features with airflow characteristics and deposited particle concentrations. Global deposition percentages ranged (at most, by 20%) between subjects and variances in localized deposition hotspots are correlated to variances in flow characteristics.
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Affiliation(s)
- Kamran Poorbahrami
- Department of Mechanical and Industrial Engineering, Northeastern University, USA.
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8
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Sul B, Altes T, Ruppert K, Qing K, Hariprasad DS, Morris M, Reifman J, Wallqvist A. In vivo dynamics of the tracheal airway and its influences on respiratory airflows. J Biomech Eng 2019; 141:2733770. [PMID: 31074759 DOI: 10.1115/1.4043723] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Indexed: 11/08/2022]
Abstract
Respiration is a dynamic process accompanied by morphological changes in the airways. Although deformation of large airways is expected to exacerbate pulmonary disease symptoms by obstructing airflow during increased minute ventilation, its quantitative effects on airflow characteristics remain unclear. Here, we used an exemplar case derived from in vivo dynamic imaging and examined the effects of tracheal deformation on airflow characteristics under different conditions. First, we measured tracheal deformation profiles of a healthy lung using magnetic resonance imaging during forced exhalation, which we simulated to characterize subject-specific airflow patterns. Subsequently, for both inhalation and exhalation, we compared the airflows when the maximal deformation in tracheal cross-sectional area was 0% (rigid), 33% (mild), 50% (moderate), or 75% (severe). We quantified differences in airflow patterns between deformable and rigid airways by computing the correlation coefficients (R) and the root-mean-square of differences (Drms) between their velocity contours. For both inhalation and exhalation, airflow patterns were similar in all branches between the rigid and mild conditions (R > 0.9; Drms < 32%). However, airflow characteristics in the moderate and severe conditions differed markedly from those in the rigid and mild conditions in all lung branches, particularly for inhalation (moderate: R > 0.1, Drms < 76%; severe: R > 0.2, Drms < 96%). Our exemplar case supports the use of a rigid airway assumption to compute flows for mild deformation. For moderate or severe deformation, however, dynamic contraction should be considered, especially during inhalation, to accurately predict airflow and elucidate the underlying pulmonary pathology.
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Affiliation(s)
- Bora Sul
- The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland; Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, Maryland
| | - Talissa Altes
- Department of Radiology, University of Missouri, Columbia, Missouri
| | - Kai Ruppert
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Kun Qing
- Department of Radiology, University of Virginia, Charlottesville, Virginia
| | - Daniel S Hariprasad
- The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland; Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, Maryland
| | - Michael Morris
- Graduate Medical Education, Brooke Army Medical Center, Joint Base San Antonio Fort Sam Houston, Texas
| | - Jaques Reifman
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, Maryland
| | - Anders Wallqvist
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, Maryland
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Asgharian B, Owen TP, Kuempel ED, Jarabek AM. Dosimetry of inhaled elongate mineral particles in the respiratory tract: The impact of shape factor. Toxicol Appl Pharmacol 2018; 361:27-35. [PMID: 29738812 PMCID: PMC6329593 DOI: 10.1016/j.taap.2018.05.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 04/24/2018] [Accepted: 05/01/2018] [Indexed: 10/17/2022]
Abstract
Inhalation exposure to some types of fibers (e.g., asbestos) is well known to be associated with respiratory diseases and conditions such as pleural plaques, fibrosis, asbestosis, lung cancer, and mesothelioma. In recent years, attention has expanded to other types of elongate mineral particles (EMPs) that may share similar geometry with asbestos fibers but which may differ in mineralogy. Inhalability, dimensions and orientation, and density are major determinants of the aerodynamic behavior for fibers and other EMPs; and the resultant internal dose is recognized as being the critical link between exposure and pathogenesis. Insufficient data are available to fully understand the role of specific physicochemical properties on the potential toxicity across various types of fiber materials. While additional information is required to assess the potential health hazards of EMPs, dosimetry models are currently available to estimate the initially deposited internal dose, which is an essential step in linking airborne exposures to potential health risks. Based on dosimetry model simulations, the inhalability and internal dose of EMPs were found to be greater than that of spherical particles having the same mass or volume. However, the complexity of the dependence of internal dose on EMPs dimensions prevented a straightforward formulation of the deposition-dimension (length or diameter) relationship. Because health outcome is generally related to internal dose, consideration of the factors that influence internal dose is important in assessing the potential health hazards of airborne EMPs.
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Affiliation(s)
| | - T Price Owen
- Applied Research Associates, Arlington, VA, United States
| | - Eileen D Kuempel
- National Institute for Occupational Safety and Health, Cincinnati, OH, United States
| | - Annie M Jarabek
- U.S. Environmental Protection Agency, Research Triangle Park, NC, United States
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Oakes JM, Mummy D, Poorbahrami K, Zha W, Fain SB. Patient-Specific Computational Simulations of Hyperpolarized 3He MRI Ventilation Defects in Healthy and Asthmatic Subjects. IEEE Trans Biomed Eng 2018; 66:1318-1327. [PMID: 30281426 DOI: 10.1109/tbme.2018.2872845] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Combined, medical imaging data and respiratory computer simulations may facilitate novel insight into pulmonary disease phenotypes, including the structure/function relationships within the airways. This integration may ultimately enable improved classification and treatment of asthma. Severe asthma (15% of asthmatics) is particularly challenging to treat, as these patients do not respond well to inhaled therapeutics. METHODS This study combines medical image data with patient-specific computational models to predict gas distributions and airway mechanics in healthy and asthmatic subjects. We achieve this by integrating segmental volume defect percent (SVDP), measured from hyperpolarized 3He MRI and CT images, to create models of patient-specific gas flow within the conducting airways. Predicted and measured SVDP distributions are achieved when the prescribed resistances are increased systematically. RESULTS Because of differences in airway morphology and regional function, airway resistances and flow structures varied between the asthmatic subjects. Specifically, while mean SVDP was similar between the severe asthmatics (4.30±5.22 versus 3.54±5.98%), one subject exhibited abnormal flow structures, high near wall flow gradients, and enhanced conducting airway resistances (17.3E-3versus 1.1E-3 cmH2O-s/mL) in comparison to the other severe asthmatic subject. CONCLUSION By coupling medical imaging data with computer simulations, we provide detailed insight into pathological flow characteristics and airway mechanics in asthmatics, beyond what could be inferred independently.
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Oakes JM, Roth SC, Shadden SC. Airflow Simulations in Infant, Child, and Adult Pulmonary Conducting Airways. Ann Biomed Eng 2017; 46:498-512. [PMID: 29264667 DOI: 10.1007/s10439-017-1971-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 12/13/2017] [Indexed: 10/18/2022]
Abstract
The airway structure continuously evolves from birth to adulthood, influencing airflow dynamics and respiratory mechanics. We currently know very little about how airflow patterns change throughout early life and its impact on airway resistance, namely because of experimental limitations. To uncover differences in respiratory dynamics between age groups, we performed subject-specific airflow simulations in an infant, child, and adult conducting airways. Airflow throughout the respiration cycle was calculated by coupling image-based models of the conducting airways to the global respiratory mechanics, where flow was driven by a pressure differential. Trachea diameter was 19, 9, and 4.5 mm for the adult (36 years, female), child (6 years, male), and infant (0.25 years, female), respectively. Mean Reynolds number within the trachea was nearly the same for each subject (1100) and Womersley number was above unity for all three subjects and largest for the adult, highlighting the significance of transient effects. In general, air speeds and airway resistances within the conducting airways were inversely correlated with age; the 3D pressure drop was highest in the infant model. These simulations provide new insight into age-dependent flow dynamics throughout the respiration cycle within subject-specific airways.
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Affiliation(s)
- Jessica M Oakes
- Department of Bioengineering, Northeastern University, Boston, MA, USA.
| | - Steven C Roth
- Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Shawn C Shadden
- Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA
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Oakes JM, Shadden SC, Grandmont C, Vignon-Clementel IE. Aerosol transport throughout inspiration and expiration in the pulmonary airways. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33. [PMID: 27860424 DOI: 10.1002/cnm.2847] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/22/2016] [Indexed: 06/06/2023]
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.
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Affiliation(s)
- Jessica M Oakes
- Department of Mechanical Engineering, University of California Berkeley, Berkeley, 94709, CA, USA
- Inria Paris, 2 Rue Simone Iff, 75012, Paris, France
- Sorbonne Universités, UPMC Univ. Paris 6, Laboratoire Jacques-Louis Lions, 75252, Paris, France
| | - Shawn C Shadden
- Department of Mechanical Engineering, University of California Berkeley, Berkeley, 94709, CA, USA
| | - Céline Grandmont
- Inria Paris, 2 Rue Simone Iff, 75012, Paris, France
- Sorbonne Universités, UPMC Univ. Paris 6, Laboratoire Jacques-Louis Lions, 75252, Paris, France
| | - Irene E Vignon-Clementel
- Inria Paris, 2 Rue Simone Iff, 75012, Paris, France
- Sorbonne Universités, UPMC Univ. Paris 6, Laboratoire Jacques-Louis Lions, 75252, Paris, France
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Kabilan S, Suffield S, Recknagle K, Jacob R, Einstein D, Kuprat A, Carson J, Colby S, Saunders J, Hines S, Teeguarden J, Straub T, Moe M, Taft S, Corley R. Computational fluid dynamics modeling of Bacillus anthracis spore deposition in rabbit and human respiratory airways. JOURNAL OF AEROSOL SCIENCE 2016; 99:64-77. [PMID: 33311732 PMCID: PMC7731948 DOI: 10.1016/j.jaerosci.2016.01.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Three-dimensional computational fluid dynamics and Lagrangian particle deposition models were developed to compare the deposition of aerosolized Bacillus anthracis spores in the respiratory airways of a human with that of the rabbit, a species commonly used in the study of anthrax disease. The respiratory airway geometries for each species were derived respectively from computed tomography (CT) and μCT images. Both models encompassed airways that extended from the external nose to the lung with a total of 272 outlets in the human model and 2878 outlets in the rabbit model. All simulations of spore deposition were conducted under transient, inhalation-exhalation breathing conditions using average species-specific minute volumes. Two different exposure scenarios were modeled in the rabbit based upon experimental inhalation studies. For comparison, human simulations were conducted at the highest exposure concentration used during the rabbit experimental exposures. Results demonstrated that regional spore deposition patterns were sensitive to airway geometry and ventilation profiles. Due to the complex airway geometries in the rabbit nose, higher spore deposition efficiency was predicted in the nasal sinus compared to the human at the same air concentration of anthrax spores. In contrast, higher spore deposition was predicted in the lower conducting airways of the human compared to the rabbit lung due to differences in airway branching pattern. This information can be used to refine published and ongoing biokinetic models of inhalation anthrax spore exposures, which currently estimate deposited spore concentrations based solely upon exposure concentrations and inhaled doses that do not factor in species-specific anatomy and physiology for deposition.
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Affiliation(s)
- S. Kabilan
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN J4-16, Richland, WA 99352, United States
| | - S.R. Suffield
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN J4-16, Richland, WA 99352, United States
| | - K.P. Recknagle
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN J4-16, Richland, WA 99352, United States
| | - R.E. Jacob
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN J4-16, Richland, WA 99352, United States
| | - D.R. Einstein
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN J4-16, Richland, WA 99352, United States
| | - A.P. Kuprat
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN J4-16, Richland, WA 99352, United States
| | - J.P. Carson
- Texas Advanced Computing Center, Austin, TX 78758, United States
| | - S.M Colby
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN J4-16, Richland, WA 99352, United States
| | - J.H. Saunders
- Battelle, 505 King Avenue, Columbus, OH 43201, United States
| | - S.A. Hines
- Battelle, 505 King Avenue, Columbus, OH 43201, United States
| | - J.G. Teeguarden
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN J4-16, Richland, WA 99352, United States
| | - T.M. Straub
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN J4-16, Richland, WA 99352, United States
| | - M. Moe
- Department of Homeland Security, Science and Technology Directorate, Washington, DC 20528, United States
| | - S.C. Taft
- U.S. Environmental Protection Agency, National Homeland Security Research Center, Threat and Consequence Assessment Division, Cincinnati, OH 45268, United States
| | - R.A. Corley
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN J4-16, Richland, WA 99352, United States
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14
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Darquenne C, Fleming JS, Katz I, Martin AR, Schroeter J, Usmani OS, Venegas J, Schmid O. Bridging the Gap Between Science and Clinical Efficacy: Physiology, Imaging, and Modeling of Aerosols in the Lung. J Aerosol Med Pulm Drug Deliv 2016; 29:107-26. [PMID: 26829187 DOI: 10.1089/jamp.2015.1270] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Development of a new drug for the treatment of lung disease is a complex and time consuming process involving numerous disciplines of basic and applied sciences. During the 2015 Congress of the International Society for Aerosols in Medicine, a group of experts including aerosol scientists, physiologists, modelers, imagers, and clinicians participated in a workshop aiming at bridging the gap between basic research and clinical efficacy of inhaled drugs. This publication summarizes the current consensus on the topic. It begins with a short description of basic concepts of aerosol transport and a discussion on targeting strategies of inhaled aerosols to the lungs. It is followed by a description of both computational and biological lung models, and the use of imaging techniques to determine aerosol deposition distribution (ADD) in the lung. Finally, the importance of ADD to clinical efficacy is discussed. Several gaps were identified between basic science and clinical efficacy. One gap between scientific research aimed at predicting, controlling, and measuring ADD and the clinical use of inhaled aerosols is the considerable challenge of obtaining, in a single study, accurate information describing the optimal lung regions to be targeted, the effectiveness of targeting determined from ADD, and some measure of the drug's effectiveness. Other identified gaps were the language and methodology barriers that exist among disciplines, along with the significant regulatory hurdles that need to be overcome for novel drugs and/or therapies to reach the marketplace and benefit the patient. Despite these gaps, much progress has been made in recent years to improve clinical efficacy of inhaled drugs. Also, the recent efforts by many funding agencies and industry to support multidisciplinary networks including basic science researchers, R&D scientists, and clinicians will go a long way to further reduce the gap between science and clinical efficacy.
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Affiliation(s)
- Chantal Darquenne
- 1 Department of Medicine, University of California , San Diego, La Jolla, California
| | - John S Fleming
- 2 National Institute of Health Research Biomedical Research Unit in Respiratory Disease , Southampton, United Kingdom .,3 Department of Medical Physics and Bioengineering, University Hospital Southampton NHS Foundation Trust , Southampton, United Kingdom
| | - Ira Katz
- 4 Medical R&D, Air Liquide Santé International, Centre de Recherche Paris-Saclay , Jouy-en-Josas, France .,5 Department of Mechanical Engineering, Lafayette College , Easton, Pennsylvania
| | - Andrew R Martin
- 6 Department of Mechanical Engineering, University of Alberta , Edmonton, Alberta, Canada
| | | | - Omar S Usmani
- 8 Airway Disease Section, National Heart and Lung Institute , Imperial College London and Royal Brompton Hospital, London, United Kingdom
| | - Jose Venegas
- 9 Department of Anesthesia (Bioengineering), MGH/Harvard, Boston, Massachusetts
| | - Otmar Schmid
- 10 Comprehensive Pneumology Center (CPC), Member of the German Center for Lung Research , Munich, Germany .,11 Institute of Lung Biology and Disease, Helmholtz Zentrum München-German Research Center for Environmental Health , Neuherberg, Germany
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15
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Corley RA, Kabilan S, Kuprat AP, Carson JP, Jacob RE, Minard KR, Teeguarden JG, Timchalk C, Pipavath S, Glenny R, Einstein DR. Comparative Risks of Aldehyde Constituents in Cigarette Smoke Using Transient Computational Fluid Dynamics/Physiologically Based Pharmacokinetic Models of the Rat and Human Respiratory Tracts. Toxicol Sci 2015; 146:65-88. [PMID: 25858911 PMCID: PMC4476461 DOI: 10.1093/toxsci/kfv071] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Computational fluid dynamics (CFD) modeling is well suited for addressing species-specific anatomy and physiology in calculating respiratory tissue exposures to inhaled materials. In this study, we overcame prior CFD model limitations to demonstrate the importance of realistic, transient breathing patterns for predicting site-specific tissue dose. Specifically, extended airway CFD models of the rat and human were coupled with airway region-specific physiologically based pharmacokinetic (PBPK) tissue models to describe the kinetics of 3 reactive constituents of cigarette smoke: acrolein, acetaldehyde and formaldehyde. Simulations of aldehyde no-observed-adverse-effect levels for nasal toxicity in the rat were conducted until breath-by-breath tissue concentration profiles reached steady state. Human oral breathing simulations were conducted using representative aldehyde yields from cigarette smoke, measured puff ventilation profiles and numbers of cigarettes smoked per day. As with prior steady-state CFD/PBPK simulations, the anterior respiratory nasal epithelial tissues received the greatest initial uptake rates for each aldehyde in the rat. However, integrated time- and tissue depth-dependent area under the curve (AUC) concentrations were typically greater in the anterior dorsal olfactory epithelium using the more realistic transient breathing profiles. For human simulations, oral and laryngeal tissues received the highest local tissue dose with greater penetration to pulmonary tissues than predicted in the rat. Based upon lifetime average daily dose comparisons of tissue hot-spot AUCs (top 2.5% of surface area-normalized AUCs in each region) and numbers of cigarettes smoked/day, the order of concern for human exposures was acrolein > formaldehyde > acetaldehyde even though acetaldehyde yields were 10-fold greater than formaldehyde and acrolein.
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Affiliation(s)
- Richard A Corley
- *Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352; Texas Advanced Computing Center, University of Texas, Austin, Texas 78758; Radiology, University of Washington, Seattle, Washington 98195; and Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98195
| | - Senthil Kabilan
- *Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352; Texas Advanced Computing Center, University of Texas, Austin, Texas 78758; Radiology, University of Washington, Seattle, Washington 98195; and Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98195
| | - Andrew P Kuprat
- *Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352; Texas Advanced Computing Center, University of Texas, Austin, Texas 78758; Radiology, University of Washington, Seattle, Washington 98195; and Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98195
| | - James P Carson
- *Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352; Texas Advanced Computing Center, University of Texas, Austin, Texas 78758; Radiology, University of Washington, Seattle, Washington 98195; and Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98195
| | - Richard E Jacob
- *Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352; Texas Advanced Computing Center, University of Texas, Austin, Texas 78758; Radiology, University of Washington, Seattle, Washington 98195; and Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98195
| | - Kevin R Minard
- *Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352; Texas Advanced Computing Center, University of Texas, Austin, Texas 78758; Radiology, University of Washington, Seattle, Washington 98195; and Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98195
| | - Justin G Teeguarden
- *Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352; Texas Advanced Computing Center, University of Texas, Austin, Texas 78758; Radiology, University of Washington, Seattle, Washington 98195; and Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98195
| | - Charles Timchalk
- *Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352; Texas Advanced Computing Center, University of Texas, Austin, Texas 78758; Radiology, University of Washington, Seattle, Washington 98195; and Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98195
| | - Sudhakar Pipavath
- *Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352; Texas Advanced Computing Center, University of Texas, Austin, Texas 78758; Radiology, University of Washington, Seattle, Washington 98195; and Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98195
| | - Robb Glenny
- *Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352; Texas Advanced Computing Center, University of Texas, Austin, Texas 78758; Radiology, University of Washington, Seattle, Washington 98195; and Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98195
| | - Daniel R Einstein
- *Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352; Texas Advanced Computing Center, University of Texas, Austin, Texas 78758; Radiology, University of Washington, Seattle, Washington 98195; and Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98195
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16
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Ismail M, Gravemeier V, Comerford A, Wall WA. A stable approach for coupling multidimensional cardiovascular and pulmonary networks based on a novel pressure-flow rate or pressure-only Neumann boundary condition formulation. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2014; 30:447-469. [PMID: 24243701 DOI: 10.1002/cnm.2611] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2013] [Revised: 09/23/2013] [Accepted: 10/12/2013] [Indexed: 06/02/2023]
Abstract
In many biomedical flow problems, reversed flows along with standard treatment of Neumann boundary conditions can cause instabilities. We have developed a method that resolves these instabilities in a consistent way while maintaining correct pressure and flow rate values. We also are able to remove the necessary prescription of both pressure and velocities/flow rates to problems where only pressure is known. In addition, the method is extended to coupled 3D/reduced-D fluid and fluid-structure interaction models. Numerical examples mainly focus on using Neumann boundary condition in cardiovascular and pulmonary systems, particularly, coupled with 3D-1D and 3D-0D models. Inflow pressure, traction, and impedance boundary conditions are first tested on idealized tubes for various Womersley numbers. Both pressure and flow rate are shown to match the analytical solutions for these examples. Our method is then tested on a coupled 1D-3D-1D artery example, demonstrating the power and simplicity of extending this method toward fluid-structure interaction. Finally, the proposed method is investigated for a coupled 3D-0D patient-specific full lung model during spontaneous breathing. All coupled 3D/reduced-D results show a perfect matching of pressure and flow rate between 3D and corresponding reduced-D boundaries. The methods are straight-forward to implement in contrast to using Lagrange multipliers as previously proposed in other studies.
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Affiliation(s)
- M Ismail
- Institute for Computational Mechanics, Technische Universität München, D-85747 Garching, Germany
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17
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Oakes JM, Marsden AL, Grandmont C, Shadden SC, Darquenne C, Vignon-Clementel IE. Airflow and particle deposition simulations in health and emphysema: from in vivo to in silico animal experiments. Ann Biomed Eng 2014; 42:899-914. [PMID: 24318192 PMCID: PMC4092242 DOI: 10.1007/s10439-013-0954-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 11/23/2013] [Indexed: 10/25/2022]
Abstract
Image-based in silico modeling tools provide detailed velocity and particle deposition data. However, care must be taken when prescribing boundary conditions to model lung physiology in health or disease, such as in emphysema. In this study, the respiratory resistance and compliance were obtained by solving an inverse problem; a 0D global model based on healthy and emphysematous rat experimental data. Multi-scale CFD simulations were performed by solving the 3D Navier-Stokes equations in an MRI-derived rat geometry coupled to a 0D model. Particles with 0.95 μm diameter were tracked and their distribution in the lung was assessed. Seven 3D-0D simulations were performed: healthy, homogeneous, and five heterogeneous emphysema cases. Compliance (C) was significantly higher (p = 0.04) in the emphysematous rats (C = 0.37 ± 0.14 cm(3)/cmH2O) compared to the healthy rats (C = 0.25 ± 0.04 cm(3)/cmH2O), while the resistance remained unchanged (p = 0.83). There were increases in airflow, particle deposition in the 3D model, and particle delivery to the diseased regions for the heterogeneous cases compared to the homogeneous cases. The results highlight the importance of multi-scale numerical simulations to study airflow and particle distribution in healthy and diseased lungs. The effect of particle size and gravity were studied. Once available, these in silico predictions may be compared to experimental deposition data.
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Affiliation(s)
- Jessica M Oakes
- Mechanical and Aerospace Engineering Department, University of California, San Diego, La Jolla, CA, 92093, USA
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18
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Fouchet-Incaux J. Artificial boundaries and formulations for the incompressible Navier–Stokes equations: applications to air and blood flows. ACTA ACUST UNITED AC 2014. [DOI: 10.1007/s40324-014-0012-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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19
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Jacob RE, Carson JP, Thomas M, Einstein DR. Dynamic multiscale boundary conditions for 4D CT of healthy and emphysematous rats. PLoS One 2013; 8:e65874. [PMID: 23799057 PMCID: PMC3683027 DOI: 10.1371/journal.pone.0065874] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 04/29/2013] [Indexed: 11/30/2022] Open
Abstract
Changes in the shape of the lung during breathing determine the movement of airways and alveoli, and thus impact airflow dynamics. Modeling airflow dynamics in health and disease is a key goal for predictive multiscale models of respiration. Past efforts to model changes in lung shape during breathing have measured shape at multiple breath-holds. However, breath-holds do not capture hysteretic differences between inspiration and expiration resulting from the additional energy required for inspiration. Alternatively, imaging dynamically--without breath-holds--allows measurement of hysteretic differences. In this study, we acquire multiple micro-CT images per breath (4DCT) in live rats, and from these images we develop, for the first time, dynamic volume maps. These maps show changes in local volume across the entire lung throughout the breathing cycle and accurately predict the global pressure-volume (PV) hysteresis. Male Sprague-Dawley rats were given either a full- or partial-lung dose of elastase or saline as a control. After three weeks, 4DCT images of the mechanically ventilated rats under anesthesia were acquired dynamically over the breathing cycle (11 time points, ≤100 ms temporal resolution, 8 cmH2O peak pressure). Non-rigid image registration was applied to determine the deformation gradient--a numerical description of changes to lung shape--at each time point. The registration accuracy was evaluated by landmark identification. Of 67 landmarks, one was determined misregistered by all three observers, and 11 were determined misregistered by two observers. Volume change maps were calculated on a voxel-by-voxel basis at all time points using both the Jacobian of the deformation gradient and the inhaled air fraction. The calculated lung PV hysteresis agrees with pressure-volume curves measured by the ventilator. Volume maps in diseased rats show increased compliance and ventilation heterogeneity. Future predictive multiscale models of rodent respiration may leverage such volume maps as boundary conditions.
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Affiliation(s)
- Richard E Jacob
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America.
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20
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Corley RA, Kabilan S, Kuprat AP, Carson JP, Minard KR, Jacob RE, Timchalk C, Glenny R, Pipavath S, Cox T, Wallis CD, Larson RF, Fanucchi MV, Postlethwait EM, Einstein DR. Comparative computational modeling of airflows and vapor dosimetry in the respiratory tracts of rat, monkey, and human. Toxicol Sci 2012; 128:500-16. [PMID: 22584687 DOI: 10.1093/toxsci/kfs168] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Computational fluid dynamics (CFD) models are useful for predicting site-specific dosimetry of airborne materials in the respiratory tract and elucidating the importance of species differences in anatomy, physiology, and breathing patterns. We improved the imaging and model development methods to the point where CFD models for the rat, monkey, and human now encompass airways from the nose or mouth to the lung. A total of 1272, 2172, and 135 pulmonary airways representing 17±7, 19±9, or 9±2 airway generations were included in the rat, monkey and human models, respectively. A CFD/physiologically based pharmacokinetic model previously developed for acrolein was adapted for these anatomically correct extended airway models. Model parameters were obtained from the literature or measured directly. Airflow and acrolein uptake patterns were determined under steady-state inhalation conditions to provide direct comparisons with prior data and nasal-only simulations. Results confirmed that regional uptake was sensitive to airway geometry, airflow rates, acrolein concentrations, air:tissue partition coefficients, tissue thickness, and the maximum rate of metabolism. Nasal extraction efficiencies were predicted to be greatest in the rat, followed by the monkey, and then the human. For both nasal and oral breathing modes in humans, higher uptake rates were predicted for lower tracheobronchial tissues than either the rat or monkey. These extended airway models provide a unique foundation for comparing material transport and site-specific tissue uptake across a significantly greater range of conducting airways in the rat, monkey, and human than prior CFD models.
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Affiliation(s)
- Richard A Corley
- Systems Toxicology, Pacific Northwest National Laboratory Richland, Washington 99352, USA.
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