1
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Geitner CM, Köglmeier LJ, Frerichs I, Langguth P, Lindner M, Schädler D, Weiler N, Becher T, Wall WA. Pressure- and time-dependent alveolar recruitment/derecruitment in a spatially resolved patient-specific computational model for injured human lungs. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2024; 40:e3787. [PMID: 38037251 DOI: 10.1002/cnm.3787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 08/28/2023] [Accepted: 10/16/2023] [Indexed: 12/02/2023]
Abstract
We present a novel computational model for the dynamics of alveolar recruitment/derecruitment (RD), which reproduces the underlying characteristics typically observed in injured lungs. The basic idea is a pressure- and time-dependent variation of the stress-free reference volume in reduced dimensional viscoelastic elements representing the acinar tissue. We choose a variable reference volume triggered by critical opening and closing pressures in a time-dependent manner from a straightforward mechanical point of view. In the case of (partially and progressively) collapsing alveolar structures, the volume available for expansion during breathing reduces and vice versa, eventually enabling consideration of alveolar collapse and reopening in our model. We further introduce a method for patient-specific determination of the underlying critical parameters of the new alveolar RD dynamics when integrated into the tissue elements, referred to as terminal units, of a spatially resolved physics-based lung model that simulates the human respiratory system in an anatomically correct manner. Relevant patient-specific parameters of the terminal units are herein determined based on medical image data and the macromechanical behavior of the lung during artificial ventilation. We test the whole modeling approach for a real-life scenario by applying it to the clinical data of a mechanically ventilated patient. The generated lung model is capable of reproducing clinical measurements such as tidal volume and pleural pressure during various ventilation maneuvers. We conclude that this new model is an important step toward personalized treatment of ARDS patients by considering potentially harmful mechanisms-such as cyclic RD and overdistension-and might help in the development of relevant protective ventilation strategies to reduce ventilator-induced lung injury (VILI).
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Affiliation(s)
- Carolin M Geitner
- Institute for Computational Mechanics, Department of Engineering Physics & Computation, TUM School of Engineering and Design, Technical University of Munich, Garching b. Muenchen, Germany
| | - Lea J Köglmeier
- Institute for Computational Mechanics, Department of Engineering Physics & Computation, TUM School of Engineering and Design, Technical University of Munich, Garching b. Muenchen, Germany
| | - Inéz Frerichs
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Patrick Langguth
- Department of Radiology and Neuroradiology, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Matthias Lindner
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Dirk Schädler
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Norbert Weiler
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Tobias Becher
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Wolfgang A Wall
- Institute for Computational Mechanics, Department of Engineering Physics & Computation, TUM School of Engineering and Design, Technical University of Munich, Garching b. Muenchen, Germany
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2
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Cruz AF, Herrmann J, Ramcharran H, Kollisch-Singule M, Tawhai MH, Bates JHT, Nieman GF, Kaczka DW. Sustained vs. Intratidal Recruitment in the Injured Lung During Airway Pressure Release Ventilation: A Computational Modeling Perspective. Mil Med 2023; 188:141-148. [PMID: 37948236 DOI: 10.1093/milmed/usad059] [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: 12/01/2022] [Revised: 02/03/2023] [Accepted: 02/14/2023] [Indexed: 11/12/2023] Open
Abstract
INTRODUCTION During mechanical ventilation, cyclic recruitment and derecruitment (R/D) of alveoli result in focal points of heterogeneous stress throughout the lung. In the acutely injured lung, the rates at which alveoli can be recruited or derecruited may also be altered, requiring longer times at higher pressure levels to be recruited during inspiration, but shorter times at lower pressure levels to minimize collapse during exhalation. In this study, we used a computational model to simulate the effects of airway pressure release ventilation (APRV) on acinar recruitment, with varying inspiratory pressure levels and durations of exhalation. MATERIALS AND METHODS The computational model consisted of a ventilator pressure source, a distensible breathing circuit, an endotracheal tube, and a porcine lung consisting of recruited and derecruited zones, as well as a transitional zone capable of intratidal R/D. Lung injury was simulated by modifying each acinus with an inflation-dependent surface tension. APRV was simulated for an inhalation duration (Thigh) of 4.0 seconds, inspiratory pressures (Phigh) of 28 and 40 cmH2O, and exhalation durations (Tlow) ranging from 0.2 to 1.5 seconds. RESULTS Both sustained acinar recruitment and intratidal R/D within the subtree were consistently higher for Phigh of 40 cmH2O vs. 28 cmH2O, regardless of Tlow. Increasing Tlow was associated with decreasing sustained acinar recruitment, but increasing intratidal R/D, within the subtree. Increasing Tlow was associated with decreasing elastance of both the total respiratory system and transitional subtree of the model. CONCLUSIONS Our computational model demonstrates the confounding effects of cyclic R/D, sustained recruitment, and parenchymal strain stiffening on estimates of total lung elastance during APRV. Increasing inspiratory pressures leads to not only more sustained recruitment of unstable acini but also more intratidal R/D. Our model indicates that higher inspiratory pressures should be used in conjunction with shorter exhalation times, to avoid increasing intratidal R/D.
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Affiliation(s)
- Andrea F Cruz
- Department of Anesthesia, University of Iowa, Iowa City, IA 52242, USA
| | - Jacob Herrmann
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA 52242, USA
| | - Harry Ramcharran
- Department of Surgery, SUNY Upstate Medical Center, Syracuse, NY 13210, USA
| | | | - Merryn H Tawhai
- Department of Bioengineering, University of Auckland, Auckland 1124, New Zealand
| | - Jason H T Bates
- Department of Medicine, University of Vermont, Burlington, VT 05405, USA
| | - Gary F Nieman
- Department of Surgery, SUNY Upstate Medical Center, Syracuse, NY 13210, USA
| | - David W Kaczka
- Department of Anesthesia, University of Iowa, Iowa City, IA 52242, USA
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA 52242, USA
- Department of Radiology, University of Iowa, Iowa City, IA 52242, USA
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3
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Hannon DM, Mistry S, Das A, Saffaran S, Laffey JG, Brook BS, Hardman JG, Bates DG. Modeling Mechanical Ventilation In Silico-Potential and Pitfalls. Semin Respir Crit Care Med 2022; 43:335-345. [PMID: 35451046 DOI: 10.1055/s-0042-1744446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Computer simulation offers a fresh approach to traditional medical research that is particularly well suited to investigating issues related to mechanical ventilation. Patients receiving mechanical ventilation are routinely monitored in great detail, providing extensive high-quality data-streams for model design and configuration. Models based on such data can incorporate very complex system dynamics that can be validated against patient responses for use as investigational surrogates. Crucially, simulation offers the potential to "look inside" the patient, allowing unimpeded access to all variables of interest. In contrast to trials on both animal models and human patients, in silico models are completely configurable and reproducible; for example, different ventilator settings can be applied to an identical virtual patient, or the same settings applied to different patients, to understand their mode of action and quantitatively compare their effectiveness. Here, we review progress on the mathematical modeling and computer simulation of human anatomy, physiology, and pathophysiology in the context of mechanical ventilation, with an emphasis on the clinical applications of this approach in various disease states. We present new results highlighting the link between model complexity and predictive capability, using data on the responses of individual patients with acute respiratory distress syndrome to changes in multiple ventilator settings. The current limitations and potential of in silico modeling are discussed from a clinical perspective, and future challenges and research directions highlighted.
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Affiliation(s)
- David M Hannon
- Anesthesia and Intensive Care Medicine, School of Medicine, NUI Galway, Ireland
| | - Sonal Mistry
- School of Engineering, University of Warwick, Coventry, United Kingdom
| | - Anup Das
- School of Engineering, University of Warwick, Coventry, United Kingdom
| | - Sina Saffaran
- Faculty of Engineering Science, University College London, London, United Kingdom
| | - John G Laffey
- Anesthesia and Intensive Care Medicine, School of Medicine, NUI Galway, Ireland
| | - Bindi S Brook
- School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Jonathan G Hardman
- Anesthesia and Critical Care, Injury Inflammation and Recovery Sciences, School of Medicine, University of Nottingham, Nottingham, United Kingdom.,Nottingham University Hospitals NHS Trust, Nottingham, United Kingdom
| | - Declan G Bates
- School of Engineering, University of Warwick, Coventry, United Kingdom
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4
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Prediction and estimation of pulmonary response and elastance evolution for volume-controlled and pressure-controlled ventilation. Biomed Signal Process Control 2022. [DOI: 10.1016/j.bspc.2021.103367] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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5
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Kaczka DW. Oscillatory ventilation redux: alternative perspectives on ventilator-induced lung injury in the acute respiratory distress syndrome. CURRENT OPINION IN PHYSIOLOGY 2021; 21:36-43. [PMID: 33898903 PMCID: PMC8056876 DOI: 10.1016/j.cophys.2021.03.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
For patients with the acute respiratory distress syndrome (ARDS), ventilation strategies that limit end-expiratory derecruitment and end-inspiratory overdistension are the only interventions to have significantly reduced the morbidity and mortality. For this reason, the use of high-frequency oscillatory ventilation (HFOV) was considered to be an ideal protective strategy, given its reliance on very low tidal volumes cycled at very high rates. However, results from clinical trials in adults with ARDS have demonstrated that HFOV does not improve clinical outcomes. Recent experimental and computational studies have shown that oscillation of a mechanically heterogeneous lung with multiple simultaneous frequencies can reduce parenchymal strain, improve gas exchange, and maintain lung recruitment at lower distending pressures compared to traditional ‘single-frequency’ HFOV. This review will discuss the theoretical rationale for the use of multiple oscillatory frequencies in ARDS, as well as the mechanisms by which it may reduce the risk for ventilator-induced lung injury.
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Affiliation(s)
- David W Kaczka
- Department of Anesthesia, University of Iowa, Iowa City, IA, USA.,Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, USA.,Department of Radiology, University of Iowa, Iowa City, IA, USA
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6
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Polak AG, Obojski A, Mroczka J. Quantitative Assessment of the Airway Response to Bronchial Tests Based on a Spirometric Curve Shift. IEEE Trans Biomed Eng 2021; 68:739-746. [PMID: 32746039 DOI: 10.1109/tbme.2020.3004907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
OBJECTIVE Although spirometry is the most common pulmonary function test, there is no method to quantitatively infer about airway resistance or other properties from the flow-volume curves. Recently, an identifiable inverse model for forced expiration was proposed, as well as the idea to deduce changes in airway resistances and compliances from spirometric curve evolution. The aim of this work was to combine the above advances in a method for assessing the airway response to bronchial tests from a spirometric curve shift. METHODS The approach is based on the differential measurement of the degree, site of maximal effect and width of changes, further recalculated into relative changes in the distribution of airway resistances (δRg) and compliances (δCg) along the bronchial tree. To this end, appropriate models were identified using the pre- and post-test spirometry data. The accuracy was validated using sets of data simulated by the anatomy and physiology based models. Finally, the method was used to analyze the bronchodilation tests of three asthmatic subjects. RESULTS The expected errors in assessing the degree, site and width of changes in the zone of conducting airways were 6.3%, 2.4 generations and 22%, respectively, and for δRg and δCg were 5-10% and 13-16%, respectively. The analyses of clinical data indicated a significant reduction in resistances and an increase in compliances of airway generations 8-12, consistent with clinical knowledge. CONCLUSION An unprecedented method to plausibly transforming the spirometry data into the site and degree of changes in airway properties has been proposed. SIGNIFICANCE The method can be used to deduce about the effects of bronchial tests, as well as to monitor changes in the airways between visits or to investigate how inhaled pharmaceuticals affect the bronchi.
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7
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Herrmann J, Gerard SE, Shao W, Hawley ML, Reinhardt JM, Christensen GE, Hoffman EA, Kaczka DW. Quantifying Regional Lung Deformation Using Four-Dimensional Computed Tomography: A Comparison of Conventional and Oscillatory Ventilation. Front Physiol 2020; 11:14. [PMID: 32153417 PMCID: PMC7044245 DOI: 10.3389/fphys.2020.00014] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 01/13/2020] [Indexed: 01/14/2023] Open
Abstract
Mechanical ventilation strategies that reduce the heterogeneity of regional lung stress and strain may reduce the risk of ventilator-induced lung injury (VILI). In this study, we used registration of four-dimensional computed tomographic (4DCT) images to assess regional lung aeration and deformation in 10 pigs under baseline conditions and following acute lung injury induced with oleic acid. CT images were obtained via dynamic axial imaging (Siemens SOMATOM Force) during conventional pressure-controlled mechanical ventilation (CMV), as well as high-frequency and multi-frequency oscillatory ventilation modalities (HFOV and MFOV, respectively). Our results demonstrate that oscillatory modalities reduce intratidal strain throughout the lung in comparison to conventional ventilation, as well as the spatial gradients of dynamic strain along the dorsal-ventral axis. Harmonic distortion of parenchymal deformation was observed during HFOV with a single discrete sinusoid delivered at the airway opening, suggesting inherent mechanical nonlinearity of the lung tissues. MFOV may therefore provide improved lung-protective ventilation by reducing strain magnitudes and spatial gradients of strain compared to either CMV or HFOV.
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Affiliation(s)
- Jacob Herrmann
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States.,Department of Anesthesia, University of Iowa, Iowa City, IA, United States.,OscillaVent, Inc., Iowa City, IA, United States
| | - Sarah E Gerard
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States
| | - Wei Shao
- Department of Electrical and Computer Engineering, University of Iowa, Iowa City, IA, United States
| | | | - Joseph M Reinhardt
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States.,Department of Radiology, University of Iowa, Iowa City, IA, United States
| | - Gary E Christensen
- Department of Electrical and Computer Engineering, University of Iowa, Iowa City, IA, United States.,Department of Radiation Oncology, University of Iowa, Iowa City, IA, United States
| | - Eric A Hoffman
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States.,Department of Radiology, University of Iowa, Iowa City, IA, United States.,Department of Internal Medicine, University of Iowa, Iowa City, IA, United States
| | - David W Kaczka
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States.,Department of Anesthesia, University of Iowa, Iowa City, IA, United States.,OscillaVent, Inc., Iowa City, IA, United States.,Department of Radiology, University of Iowa, Iowa City, IA, United States
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8
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Bhatawadekar SA, Leary D, de Lange V, Peters U, Fulton S, Hernandez P, McParland C, Maksym GN. Reactance and elastance as measures of small airways response to bronchodilator in asthma. J Appl Physiol (1985) 2019; 127:1772-1781. [PMID: 31647721 DOI: 10.1152/japplphysiol.01131.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Bronchodilation alters both respiratory system resistance (Rrs) and reactance (Xrs) in asthma, but how changes in Rrs and Xrs compare, and respond differently in health and asthma, in reflecting the contributions from the large and small airways has not been assessed. We assessed reversibility using spirometry and oscillometry in healthy and asthma subjects. Using a multibranch airway-tree model with the mechanics of upper airway shunt, we compared the effects of airway dilation and small airways recruitment to explain the changes in Rrs and Xrs. Bronchodilator decreased Rrs by 23.0 (19.0)% in 18 asthma subjects and by 13.5 (19.5)% in 18 healthy subjects. Estimated respiratory system elastance (Ers) decreased by 23.2 (21.4)% in asthma, with no significant decrease in healthy subjects. With the use of the model, airway recruitment of 15% across a generation of the small airways could explain the changes in Ers in asthma with no recruitment in healthy subjects. In asthma, recruitment accounted for 40% of the changes in Rrs, with the remaining explained by airway dilation of 6.8% attributable largely to the central airways. Interestingly, the same dilation magnitude explained the changes in Rrs in healthy subjects. Shunt only affected Rrs of the model. Ers was unaltered in health and unaffected by shunt in both groups. In asthma, Ers changed comparably to Rrs and could be attributed to small airways, while the change in Rrs was split between large and small airways. This implies that in asthma Ers sensed through Xrs may be a more effective measure of small airways obstruction and recruitment than Rrs.NEW & NOTEWORTHY This is the first study to quantify to relative contributions of small and large airways to bronchodilator response in healthy subjects and patients with asthma. The response of the central airways to bronchodilator was similar in magnitude in both study groups, whereas the response of the small airways was significant among patients with asthma. These results suggest that low-frequency reactance and derived elastance are both sensitive measures of small airway function in asthma.
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Affiliation(s)
- S A Bhatawadekar
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Medicine, University of Vermont College of Medicine, Burlington, Vermont
| | - D Leary
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, Colorado
| | - V de Lange
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
| | - U Peters
- Department of Medicine, University of Vermont College of Medicine, Burlington, Vermont
| | - S Fulton
- Division of Respirology, QE-II Health Sciences Centre, Halifax, Nova Scotia, Canada
| | - P Hernandez
- Division of Respirology, QE-II Health Sciences Centre, Halifax, Nova Scotia, Canada.,Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - C McParland
- Division of Respirology, QE-II Health Sciences Centre, Halifax, Nova Scotia, Canada.,Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - G N Maksym
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
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9
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Herrmann J, Tawhai MH, Kaczka DW. Strain, strain rate, and mechanical power: An optimization comparison for oscillatory ventilation. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2019; 35:e3238. [PMID: 31318162 PMCID: PMC6785367 DOI: 10.1002/cnm.3238] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 06/07/2019] [Accepted: 07/14/2019] [Indexed: 06/10/2023]
Abstract
The purpose of this study was to assess the potential for optimization of mechanical ventilator waveforms using multiple frequencies of oscillatory flow delivered simultaneously to minimize the risk of ventilator-induced lung injury (VILI) associated with regional strain, strain rate, and mechanical power. Optimization was performed using simulations of distributed oscillatory flow and gas transport in a computational model of anatomically derived branching airway segments and viscoelastic terminal acini under healthy and injured conditions. Objective functions defined by regional strain or strain rate were minimized by single-frequency ventilation waveforms using the highest or lowest frequencies available, respectively. However, a mechanical power objective function was minimized by a combination of multiple frequencies delivered simultaneously. This simulation study thus demonstrates the potential for multifrequency oscillatory ventilation to reduce regional mechanical power in comparison to single-frequency ventilation, and thereby reduce the risk of VILI.
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Affiliation(s)
- Jacob Herrmann
- Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa, USA
- Department of Anesthesia, University of Iowa, Iowa City, Iowa, USA
| | - Merryn H. Tawhai
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - David W. Kaczka
- Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa, USA
- Department of Anesthesia, University of Iowa, Iowa City, Iowa, USA
- Department of Radiology, University of Iowa, Iowa City, Iowa, USA
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10
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Herrmann J, Tawhai MH, Kaczka DW. Computational Modeling of Primary Blast Lung Injury: Implications for Ventilator Management. Mil Med 2019; 184:273-281. [PMID: 30901433 DOI: 10.1093/milmed/usy305] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 09/27/2018] [Accepted: 10/18/2018] [Indexed: 01/02/2023] Open
Abstract
Primary blast lung injury (PBLI) caused by exposure to high-intensity pressure waves is associated with parenchymal tissue injury and severe ventilation-perfusion mismatch. Although supportive ventilation is often required in patients with PBLI, maldistribution of gas flow in mechanically heterogeneous lungs may lead to further injury due to increased parenchymal strain and strain rate, which are difficult to predict in vivo. In this study, we developed a computational lung model with mechanical properties consistent with healthy and PBLI conditions. PBLI conditions were simulated with bilateral derecruitment and increased perihilar tissue stiffness. As a result of these tissue abnormalities, airway flow was heterogeneously distributed in the model under PBLI conditions, during both conventional mechanical ventilation (CMV) and high-frequency oscillatory ventilation. PBLI conditions resulted in over three-fold higher parenchymal strains compared to the healthy condition during CMV, with flow distributed according to regional tissue stiffness. During high-frequency oscillatory ventilation, flow distribution became increasingly heterogeneous and frequency-dependent. We conclude that the distribution and rate of parenchymal distension during mechanical ventilation depend on PBLI severity as well as ventilatory modality. These simulations may allow realistic assessment of the risks associated with ventilator-induced lung injury following PBLI, and facilitate the development of alternative lung-protective ventilation modalities.
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Affiliation(s)
- Jacob Herrmann
- Department of Anesthesia, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA.,Department of Biomedical Engineering, University of Iowa, 5601 Seamans Center for the Engineering Arts and Sciences, Iowa City, IA
| | - Merryn H Tawhai
- Auckland Bioengineering Institute, University of Auckland, 6/70 Symonds St, Grafton, Auckland 1010, New Zealand
| | - David W Kaczka
- Department of Anesthesia, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA.,Department of Biomedical Engineering, University of Iowa, 5601 Seamans Center for the Engineering Arts and Sciences, Iowa City, IA.,Department of Radiology, University of Iowa Hospitals and Clinics, 3970 John Pappajohn Pavilion, 200 Hawkins Dr, Iowa City, IA
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11
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Soares JHN, Carvalho AR, Bergamini BC, Gress MAK, Jandre FC, Zin WA, Giannella-Neto A. Alveolar Tidal recruitment/derecruitment and Overdistension During Four Levels of End-Expiratory Pressure with Protective Tidal Volume During Anesthesia in a Murine Lung-Healthy Model. Lung 2018; 196:335-342. [DOI: 10.1007/s00408-018-0096-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 02/05/2018] [Indexed: 12/16/2022]
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12
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Herrmann J, Tawhai MH, Kaczka DW. Parenchymal strain heterogeneity during oscillatory ventilation: why two frequencies are better than one. J Appl Physiol (1985) 2017; 124:653-663. [PMID: 29051332 DOI: 10.1152/japplphysiol.00615.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
High-frequency oscillatory ventilation (HFOV) relies on low tidal volumes cycled at supraphysiological rates, producing fundamentally different mechanisms for gas transport and exchange compared with conventional mechanical ventilation. Despite the appeal of using low tidal volumes to mitigate the risks of ventilator-induced lung injury, HFOV has not improved mortality for most clinical indications. This may be due to nonuniform and frequency-dependent distribution of flow throughout the lung. The goal of this study was to compare parenchymal strain heterogeneity during eucapnic HFOV when using oscillatory waveforms that consisted of either a single discrete frequency or two simultaneous frequencies. We utilized a three-dimensional, anatomically structured canine lung model for simulating frequency-dependent ventilation distribution. Gas transport was simulated via direct alveolar ventilation, advective mixing at bifurcations, turbulent and oscillatory dispersion, and molecular diffusion. Volume amplitudes at each oscillatory frequency were iteratively optimized to attain eucapnia. Ventilation using single-frequency HFOV demonstrated increasing heterogeneity of acinar flow and CO2 elimination with frequency for frequencies greater than the resonant frequency. For certain pairs of frequencies, a linear combination of the two corresponding ventilation distributions yielded reduced acinar strain heterogeneity compared with either frequency alone. Our model demonstrates that superposition of two simultaneous oscillatory frequencies can achieve more uniform ventilation distribution, and therefore lessen the potential for ventilator-induced lung injury, compared with traditional single-frequency HFOV. NEW & NOTEWORTHY In this study, we simulated oscillatory ventilation with multiple simultaneous frequencies using a computational lung model that includes distributed flow and gas transport. A mechanism of benefit was identified by which ventilation with two simultaneous frequencies results in reduced acinar strain heterogeneity compared with either frequency alone. This finding suggests the possibility of tuning the spectral content of ventilator waveforms according to patient-specific mechanical heterogeneity.
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Affiliation(s)
- Jacob Herrmann
- Department of Anesthesia, University of Iowa , Iowa City, Iowa.,Department of Biomedical Engineering, University of Iowa , Iowa City, Iowa
| | - Merryn H Tawhai
- Auckland Bioengineering Institute, University of Auckland , Auckland , New Zealand
| | - David W Kaczka
- Department of Anesthesia, University of Iowa , Iowa City, Iowa.,Department of Biomedical Engineering, University of Iowa , Iowa City, Iowa.,Department of Radiology, University of Iowa , Iowa City, Iowa
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13
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Nieman GF, Satalin J, Kollisch-Singule M, Andrews P, Aiash H, Habashi NM, Gatto LA. Physiology in Medicine: Understanding dynamic alveolar physiology to minimize ventilator-induced lung injury. J Appl Physiol (1985) 2017; 122:1516-1522. [PMID: 28385915 PMCID: PMC7203565 DOI: 10.1152/japplphysiol.00123.2017] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 03/16/2017] [Accepted: 04/03/2017] [Indexed: 02/01/2023] Open
Abstract
Acute respiratory distress syndrome (ARDS) remains a serious clinical problem with the main treatment being supportive in the form of mechanical ventilation. However, mechanical ventilation can be a double-edged sword: if set improperly, it can exacerbate the tissue damage caused by ARDS; this is known as ventilator-induced lung injury (VILI). To minimize VILI, we must understand the pathophysiologic mechanisms of tissue damage at the alveolar level. In this Physiology in Medicine paper, the dynamic physiology of alveolar inflation and deflation during mechanical ventilation will be reviewed. In addition, the pathophysiologic mechanisms of VILI will be reviewed, and this knowledge will be used to suggest an optimal mechanical breath profile (MBP: all airway pressures, volumes, flows, rates, and the duration that they are applied at both inspiration and expiration) necessary to minimize VILI. Our review suggests that the current protective ventilation strategy, known as the “open lung strategy,” would be the optimal lung-protective approach. However, the viscoelastic behavior of dynamic alveolar inflation and deflation has not yet been incorporated into protective mechanical ventilation strategies. Using our knowledge of dynamic alveolar mechanics (i.e., the dynamic change in alveolar and alveolar duct size and shape during tidal ventilation) to modify the MBP so as to minimize VILI will reduce the morbidity and mortality associated with ARDS.
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Affiliation(s)
- Gary F Nieman
- State University of New York Upstate Medical University, Syracuse, New York
| | - Josh Satalin
- State University of New York Upstate Medical University, Syracuse, New York;
| | | | - Penny Andrews
- R Adams Cowley Shock Trauma Center, Baltimore, Maryland
| | - Hani Aiash
- State University of New York Upstate Medical University, Syracuse, New York.,Suez Canal University, Ismailia, Egypt; and
| | | | - Louis A Gatto
- State University of New York Upstate Medical University, Syracuse, New York.,State University of New York Cortland, Cortland, New York
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Herrmann J, Tawhai MH, Kaczka DW. Regional gas transport in the heterogeneous lung during oscillatory ventilation. J Appl Physiol (1985) 2016; 121:1306-1318. [PMID: 27763872 PMCID: PMC5206385 DOI: 10.1152/japplphysiol.00097.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 09/29/2016] [Accepted: 09/29/2016] [Indexed: 11/22/2022] Open
Abstract
Regional ventilation in the injured lung is heterogeneous and frequency dependent, making it difficult to predict how an oscillatory flow waveform at a specified frequency will be distributed throughout the periphery. To predict the impact of mechanical heterogeneity on regional ventilation distribution and gas transport, we developed a computational model of distributed gas flow and CO2 elimination during oscillatory ventilation from 0.1 to 30 Hz. The model consists of a three-dimensional airway network of a canine lung, with heterogeneous parenchymal tissues to mimic effects of gravity and injury. Model CO2 elimination during single frequency oscillation was validated against previously published experimental data (Venegas JG, Hales CA, Strieder DJ, J Appl Physiol 60: 1025-1030, 1986). Simulations of gas transport demonstrated a critical transition in flow distribution at the resonant frequency, where the reactive components of mechanical impedance due to airway inertia and parenchymal elastance were equal. For frequencies above resonance, the distribution of ventilation became spatially clustered and frequency dependent. These results highlight the importance of oscillatory frequency in managing the regional distribution of ventilation and gas exchange in the heterogeneous lung.
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Affiliation(s)
- Jacob Herrmann
- Department of Anesthesia, University of Iowa, Iowa City, Iowa.,Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa
| | - Merryn H Tawhai
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand; and
| | - David W Kaczka
- Department of Anesthesia, University of Iowa, Iowa City, Iowa; .,Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa.,Department of Radiology, University of Iowa, Iowa City, Iowa
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