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Quiros KAM, Nelson TM, Ulu A, Dominguez EC, Biddle TA, Lo DD, Nordgren TM, Eskandari M. A Comparative Study of Ex-Vivo Murine Pulmonary Mechanics Under Positive- and Negative-Pressure Ventilation. Ann Biomed Eng 2024; 52:342-354. [PMID: 37906375 PMCID: PMC10808462 DOI: 10.1007/s10439-023-03380-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 10/03/2023] [Indexed: 11/02/2023]
Abstract
Increased ventilator use during the COVID-19 pandemic resurrected persistent questions regarding mechanical ventilation including the difference between physiological and artificial breathing induced by ventilators (i.e., positive- versus negative-pressure ventilation, PPV vs NPV). To address this controversy, we compare murine specimens subjected to PPV and NPV in ex vivo quasi-static loading and quantify pulmonary mechanics via measures of quasi-static and dynamic compliances, transpulmonary pressure, and energetics when varying inflation frequency and volume. Each investigated mechanical parameter yields instance(s) of significant variability between ventilation modes. Most notably, inflation compliance, percent relaxation, and peak pressure are found to be consistently dependent on the ventilation mode. Maximum inflation volume and frequency note varied dependencies contingent on the ventilation mode. Contradictory to limited previous clinical investigations of oxygenation and end-inspiratory measures, the mechanics-focused comprehensive findings presented here indicate lung properties are dependent on loading mode, and importantly, these dependencies differ between smaller versus larger mammalian species despite identical custom-designed PPV/NPV ventilator usage. Results indicate that past contradictory findings regarding ventilation mode comparisons in the field may be linked to the chosen animal model. Understanding the differing fundamental mechanics between PPV and NPV may provide insights for improving ventilation strategies and design to prevent associated lung injuries.
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Affiliation(s)
- K A M Quiros
- Department of Mechanical Engineering, University of California Riverside, 900 University Ave., Riverside, CA, 92506, USA
| | - T M Nelson
- Department of Mechanical Engineering, University of California Riverside, 900 University Ave., Riverside, CA, 92506, USA
| | - A Ulu
- Division of Biomedical Sciences, Riverside School of Medicine, University of California, Riverside, CA, USA
| | - E C Dominguez
- Division of Biomedical Sciences, Riverside School of Medicine, University of California, Riverside, CA, USA
- Environmental Toxicology Graduate Program, University of California, Riverside, CA, USA
| | - T A Biddle
- Division of Biomedical Sciences, Riverside School of Medicine, University of California, Riverside, CA, USA
- Environmental Toxicology Graduate Program, University of California, Riverside, CA, USA
- School of Medicine, BREATHE Center, University of California, Riverside, CA, USA
| | - D D Lo
- Division of Biomedical Sciences, Riverside School of Medicine, University of California, Riverside, CA, USA
- School of Medicine, BREATHE Center, University of California, Riverside, CA, USA
- Center for Health Disparities Research, University of California, Riverside, CA, USA
| | - T M Nordgren
- Division of Biomedical Sciences, Riverside School of Medicine, University of California, Riverside, CA, USA
- Environmental Toxicology Graduate Program, University of California, Riverside, CA, USA
- School of Medicine, BREATHE Center, University of California, Riverside, CA, USA
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, USA
| | - M Eskandari
- Department of Mechanical Engineering, University of California Riverside, 900 University Ave., Riverside, CA, 92506, USA.
- School of Medicine, BREATHE Center, University of California, Riverside, CA, USA.
- Department of Bioengineering, University of California, Riverside, CA, USA.
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Pydi YS, Nath A, Chawla A, Mukherjee S, Lalwani S, Malhotra R, Datla NV. Strain-rate-dependent material properties of human lung parenchymal tissue using inverse finite element approach. Biomech Model Mechanobiol 2023; 22:2083-2096. [PMID: 37535253 DOI: 10.1007/s10237-023-01751-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 07/09/2023] [Indexed: 08/04/2023]
Abstract
Automobile crashes and blunt trauma often lead to life-threatening thoracic injuries, especially to the lung tissues. These injuries can be simulated using finite element-based human body models that need dynamic material properties of lung tissue. The strain-rate-dependent material parameters of human parenchymal tissues were determined in this study using uniaxial quasi-static (1 mm/s) and dynamic (1.6, 3, and 5 m/s) compression tests. A bilinear material model was used to capture the nonlinear behavior of the lung tissue, which was implemented using a user-defined material in LS-DYNA. Inverse mapping using genetic algorithm-based optimization of all experimental data with the corresponding FE models yielded a set of strain-rate-dependent material parameters. The bilinear material parameters are obtained for the strain rates of 0.1, 100, 300, and 500 s-1. The estimated elastic modulus increased from 43 to 153 kPa, while the toe strain reduced from 0.39 to 0.29 when the strain rate was increased from 0.1 to 500 s-1. The optimized bilinear material properties of parenchymal tissue exhibit a piecewise linear relationship with the strain rate.
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Affiliation(s)
- Yeswanth S Pydi
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, 110016, India.
| | - Atri Nath
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, 110016, India
| | - Anoop Chawla
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, 110016, India
| | - Sudipto Mukherjee
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, 110016, India
| | - Sanjeev Lalwani
- Department of Forensic Science and Toxicology, All India Institute of Medical Sciences, New Delhi, India
| | - Rajesh Malhotra
- Department of Orthopaedics, All India Institute of Medical Sciences, New Delhi, India
| | - Naresh V Datla
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, 110016, India
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3
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Laville C, Fetita C, Gille T, Brillet PY, Nunes H, Bernaudin JF, Genet M. Comparison of optimization parametrizations for regional lung compliance estimation using personalized pulmonary poromechanical modeling. Biomech Model Mechanobiol 2023; 22:1541-1554. [PMID: 36913005 PMCID: PMC10009868 DOI: 10.1007/s10237-023-01691-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 01/09/2023] [Indexed: 03/14/2023]
Abstract
Interstitial lung diseases, such as idiopathic pulmonary fibrosis (IPF) or post-COVID-19 pulmonary fibrosis, are progressive and severe diseases characterized by an irreversible scarring of interstitial tissues that affects lung function. Despite many efforts, these diseases remain poorly understood and poorly treated. In this paper, we propose an automated method for the estimation of personalized regional lung compliances based on a poromechanical model of the lung. The model is personalized by integrating routine clinical imaging data - namely computed tomography images taken at two breathing levels in order to reproduce the breathing kinematic-notably through an inverse problem with fully personalized boundary conditions that is solved to estimate patient-specific regional lung compliances. A new parametrization of the inverse problem is introduced in this paper, based on the combined estimation of a personalized breathing pressure in addition to material parameters, improving the robustness and consistency of estimation results. The method is applied to three IPF patients and one post-COVID-19 patient. This personalized model could help better understand the role of mechanics in pulmonary remodeling due to fibrosis; moreover, patient-specific regional lung compliances could be used as an objective and quantitative biomarker for improved diagnosis and treatment follow up for various interstitial lung diseases.
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Affiliation(s)
- Colin Laville
- Laboratoire de Mécanique des Solides, École Polytechnique/CNRS/IPP, Palaiseau, France
- Inria, Palaiseau, France
| | | | - Thomas Gille
- Hypoxie et Poumon, Université Sorbonne Paris Nord/INSERM, Bobigny, France
- Hôpital Avicenne, APHP, Bobigny, France
| | - Pierre-Yves Brillet
- Hypoxie et Poumon, Université Sorbonne Paris Nord/INSERM, Bobigny, France
- Hôpital Avicenne, APHP, Bobigny, France
| | - Hilario Nunes
- Hypoxie et Poumon, Université Sorbonne Paris Nord/INSERM, Bobigny, France
- Hôpital Avicenne, APHP, Bobigny, France
| | | | - Martin Genet
- Laboratoire de Mécanique des Solides, École Polytechnique/CNRS/IPP, Palaiseau, France
- Inria, Palaiseau, France
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4
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Daphalapurkar N, Riglin J, Mohan A, Harris J, Bernardin J. Quasi-dynamic breathing model of the lung incorporating viscoelasticity of the lung tissue. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2023:e3744. [PMID: 37334440 DOI: 10.1002/cnm.3744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 03/21/2023] [Accepted: 06/05/2023] [Indexed: 06/20/2023]
Abstract
We advanced a novel model to calculate viscoelastic lung compliance and airflow resistance in presence of mucus, accounting for the quasi-linear viscoelastic stress-strain response of the parenchyma (alveoli) tissue. We adapted a continuum-based numerical modeling approach for the lung, integrating the fluid mechanics of the airflow within individual generations of the bronchi and alveoli. The model accounts for elasticity of the deformable bronchioles, resistance to airflow due to the presence of mucus within the bronchioles, and subsequent mucus flow. Simulated quasi-dynamic inhalation and expiration cycles were used to characterize the net compliance and resistance of the lung, considering the rheology of the mucus and viscoelastic properties of the parenchyma tissue. The structure and material properties of the lung were identified to have an important contribution to the lung compliance and airflow resistance. The secondary objective of this work was to assess whether a higher frequency and smaller volume of harmonic air flow rate compared to a normal ventilator breathing cycle enhanced mucus outflow. Results predict, lower mucus viscosity and higher excitation frequency of breathing are favorable for the flow of mucus up the bronchi tree, towards the trachea.
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Affiliation(s)
- Nitin Daphalapurkar
- Fluid Dynamics and Solid Mechanics, T-3, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
| | - Jacob Riglin
- Mechanical and Thermal Engineering, E-1, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
| | - Arvind Mohan
- Computational Physics and Methods, CCS-2, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
| | - Jennifer Harris
- Biosecurity and Public Health, B-10, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
| | - John Bernardin
- Mechanical and Thermal Engineering, E-1, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
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Mariano CA, Sattari S, Ramirez GO, Eskandari M. Effects of tissue degradation by collagenase and elastase on the biaxial mechanics of porcine airways. Respir Res 2023; 24:105. [PMID: 37031200 PMCID: PMC10082978 DOI: 10.1186/s12931-023-02376-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Accepted: 02/22/2023] [Indexed: 04/10/2023] Open
Abstract
BACKGROUND Common respiratory illnesses, such as emphysema and chronic obstructive pulmonary disease, are characterized by connective tissue damage and remodeling. Two major fibers govern the mechanics of airway tissue: elastin enables stretch and permits airway recoil, while collagen prevents overextension with stiffer properties. Collagenase and elastase degradation treatments are common avenues for contrasting the role of collagen and elastin in healthy and diseased states; while previous lung studies of collagen and elastin have analyzed parenchymal strips in animal and human specimens, none have focused on the airways to date. METHODS Specimens were extracted from the proximal and distal airways, namely the trachea, large bronchi, and small bronchi to facilitate evaluations of material heterogeneity, and subjected to biaxial planar loading in the circumferential and axial directions to assess airway anisotropy. Next, samples were subjected to collagenase and elastase enzymatic treatment and tensile tests were repeated. Airway tissue mechanical properties pre- and post-treatment were comprehensively characterized via measures of initial and ultimate moduli, strain transitions, maximum stress, hysteresis, energy loss, and viscoelasticity to gain insights regarding the specialized role of individual connective tissue fibers and network interactions. RESULTS Enzymatic treatment demonstrated an increase in airway tissue compliance throughout loading and resulted in at least a 50% decrease in maximum stress overall. Strain transition values led to significant anisotropic manifestation post-treatment, where circumferential tissues transitioned at higher strains compared to axial counterparts. Hysteresis values and energy loss decreased after enzymatic treatment, where hysteresis reduced by almost half of the untreated value. Anisotropic ratios exhibited axially led stiffness at low strains which transitioned to circumferentially led stiffness when subjected to higher strains. Viscoelastic stress relaxation was found to be greater in the circumferential direction for bronchial airway regions compared to axial counterparts. CONCLUSION Targeted fiber treatment resulted in mechanical alterations across the loading range and interactions between elastin and collagen connective tissue networks was observed. Providing novel mechanical characterization of elastase and collagenase treated airways aids our understanding of individual and interconnected fiber roles, ultimately helping to establish a foundation for constructing constitutive models to represent various states and progressions of pulmonary disease.
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Affiliation(s)
- Crystal A Mariano
- Department of Mechanical Engineering, University of California at Riverside, Riverside, CA, USA
| | - Samaneh Sattari
- Department of Mechanical Engineering, University of California at Riverside, Riverside, CA, USA
| | - Gustavo O Ramirez
- Department of Mechanical Engineering, University of California at Riverside, Riverside, CA, USA
| | - Mona Eskandari
- Department of Mechanical Engineering, University of California at Riverside, Riverside, CA, USA.
- BREATHE Center, School of Medicine, University of California at Riverside, Riverside, CA, USA.
- Department of Bioengineering, University of California at Riverside, Riverside, CA, USA.
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6
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Nelson TM, Quiros KAM, Dominguez EC, Ulu A, Nordgren TM, Eskandari M. Diseased and healthy murine local lung strains evaluated using digital image correlation. Sci Rep 2023; 13:4564. [PMID: 36941463 PMCID: PMC10026788 DOI: 10.1038/s41598-023-31345-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 03/09/2023] [Indexed: 03/22/2023] Open
Abstract
Tissue remodeling in pulmonary disease irreversibly alters lung functionality and impacts quality of life. Mechanical ventilation is amongst the few pulmonary interventions to aid respiration, but can be harmful or fatal, inducing excessive regional (i.e., local) lung strains. Previous studies have advanced understanding of diseased global-level lung response under ventilation, but do not adequately capture the critical local-level response. Here, we pair a custom-designed pressure-volume ventilator with new applications of digital image correlation, to directly assess regional strains in the fibrosis-induced ex-vivo mouse lung, analyzed via regions of interest. We discuss differences between diseased and healthy lung mechanics, such as distensibility, heterogeneity, anisotropy, alveolar recruitment, and rate dependencies. Notably, we compare local and global compliance between diseased and healthy states by assessing the evolution of pressure-strain and pressure-volume curves resulting from various ventilation volumes and rates. We find fibrotic lungs are less-distensible, with altered recruitment behaviors and regional strains, and exhibit disparate behaviors between local and global compliance. Moreover, these diseased characteristics show volume-dependence and rate trends. Ultimately, we demonstrate how fibrotic lungs may be particularly susceptible to damage when contrasted to the strain patterns of healthy counterparts, helping to advance understanding of how ventilator induced lung injury develops.
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Affiliation(s)
- T M Nelson
- Department of Mechanical Engineering, University of California, Riverside, CA, USA
| | - K A M Quiros
- Department of Mechanical Engineering, University of California, Riverside, CA, USA
| | - E C Dominguez
- Division of Biomedical Sciences, Riverside School of Medicine, University of California, Riverside, CA, USA
- Environmental Toxicology Graduate Program, University of California Riverside, Riverside, CA, USA
| | - A Ulu
- Division of Biomedical Sciences, Riverside School of Medicine, University of California, Riverside, CA, USA
| | - T M Nordgren
- Division of Biomedical Sciences, Riverside School of Medicine, University of California, Riverside, CA, USA
- Environmental Toxicology Graduate Program, University of California Riverside, Riverside, CA, USA
- BREATHE Center, School of Medicine, University of California, Riverside, CA, USA
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, USA
| | - M Eskandari
- Department of Mechanical Engineering, University of California, Riverside, CA, USA.
- BREATHE Center, School of Medicine, University of California, Riverside, CA, USA.
- Department of Bioengineering, University of California, Riverside, CA, USA.
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7
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Bhana RH, Magan AB. Lung Mechanics: A Review of Solid Mechanical Elasticity in Lung Parenchyma. JOURNAL OF ELASTICITY 2023; 153:53-117. [PMID: 36619653 PMCID: PMC9808719 DOI: 10.1007/s10659-022-09973-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 12/13/2022] [Indexed: 06/17/2023]
Abstract
The lung is the main organ of the respiratory system. Its purpose is to facilitate gas exchange (breathing). Mechanically, breathing may be described as the cyclic application of stresses acting upon the lung surface. These forces are offset by prominent stress-bearing components of lung tissue. These components result from the mechanical elastic properties of lung parenchyma. Various studies have been dedicated to understanding the macroscopic behaviour of parenchyma. This has been achieved through pressure-volume analysis, numerical methods, the development of constitutive equations or strain-energy functions, finite element methods, image processing and elastography. Constitutive equations can describe the elastic behaviour exhibited by lung parenchyma through the relationship between the macroscopic stress and strain. The research conducted within lung mechanics around the elastic and resistive properties of the lung has allowed scientists to develop new methods and equipment for evaluating and treating pulmonary pathogens. This paper establishes a review of mathematical studies conducted within lung mechanics, centering on the development and implementation of solid mechanics to the understanding of the mechanical properties of the lung. Under the classical theory of elasticity, the lung is said to behave as an isotropic elastic continuum undergoing small deformations. However, the lung has also been known to display heterogeneous anisotropic behaviour associated with large deformations. Therefore, focus is placed on the assumptions and development of the various models, their mechanical influence on lung physiology, and the development of constitutive equations through the classical and non-classical theory of elasticity. Lastly, we also look at lung blast mechanics. No explicit emphasis is placed on lung pathology.
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Affiliation(s)
- R. H. Bhana
- School of Computer Science and Applied Mathematics, University of the Witwatersrand, Johannesburg, Wits, 2050 South Africa
| | - A. B. Magan
- School of Computer Science and Applied Mathematics, University of the Witwatersrand, Johannesburg, Wits, 2050 South Africa
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8
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Nelson TM, Quiros KAM, Mariano CA, Sattari S, Ulu A, Dominguez EC, Nordgren TM, Eskandari M. Associating local strains to global pressure-volume mouse lung mechanics using digital image correlation. Physiol Rep 2022; 10:e15466. [PMID: 36207795 PMCID: PMC9547081 DOI: 10.14814/phy2.15466] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 08/22/2022] [Accepted: 08/28/2022] [Indexed: 12/24/2022] Open
Abstract
Pulmonary diseases alter lung mechanical properties, can cause loss of function, and necessitate use of mechanical ventilation, which can be detrimental. Investigations of lung tissue (local) scale mechanical properties are sparse compared to that of the whole organ (global) level, despite connections between regional strain injury and ventilation. We examine ex vivo mouse lung mechanics by investigating strain values, local compliance, tissue surface heterogeneity, and strain evolutionary behavior for various inflation rates and volumes. A custom electromechanical, pressure-volume ventilator is coupled with digital image correlation to measure regional lung strains and associate local to global mechanics by analyzing novel pressure-strain evolutionary measures. Mean strains at 5 breaths per minute (BPM) for applied volumes of 0.3, 0.5, and 0.7 ml are 5.0, 7.8, and 11.3%, respectively, and 4.7, 8.8, and 12.2% for 20 BPM. Similarly, maximum strains among all rate and volume combinations range 10.7%-22.4%. Strain values (mean, range, mode, and maximum) at peak inflation often exhibit significant volume dependencies. Additionally, select evolutionary behavior (e.g., local lung compliance quantification) and tissue heterogeneity show significant volume dependence. Rate dependencies are generally found to be insignificant; however, strain values and surface lobe heterogeneity tend to increase with increasing rates. By quantifying strain evolutionary behavior in relation to pressure-volume measures, we associate time-continuous local to global mouse lung mechanics for the first time and further examine the role of volume and rate dependency. The interplay of multiscale deformations evaluated in this work can offer insights for clinical applications, such as ventilator-induced lung injury.
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Affiliation(s)
- Talyah M. Nelson
- Department of Mechanical EngineeringUniversity of CaliforniaRiversideCaliforniaUSA
| | | | - Crystal A. Mariano
- Department of Mechanical EngineeringUniversity of CaliforniaRiversideCaliforniaUSA
| | - Samaneh Sattari
- Department of Mechanical EngineeringUniversity of CaliforniaRiversideCaliforniaUSA
| | - Arzu Ulu
- BREATHE CenterSchool of Medicine University of CaliforniaRiversideCaliforniaUSA,Division of Biomedical SciencesSchool of Medicine, University of CaliforniaRiversideCaliforniaUSA
| | - Edward C. Dominguez
- BREATHE CenterSchool of Medicine University of CaliforniaRiversideCaliforniaUSA,Division of Biomedical SciencesSchool of Medicine, University of CaliforniaRiversideCaliforniaUSA
| | - Tara M. Nordgren
- BREATHE CenterSchool of Medicine University of CaliforniaRiversideCaliforniaUSA,Division of Biomedical SciencesSchool of Medicine, University of CaliforniaRiversideCaliforniaUSA
| | - Mona Eskandari
- Department of Mechanical EngineeringUniversity of CaliforniaRiversideCaliforniaUSA,BREATHE CenterSchool of Medicine University of CaliforniaRiversideCaliforniaUSA,Department of BioengineeringUniversity of CaliforniaRiversideCaliforniaUSA
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9
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Mariano CA, Sattari S, Quiros KAM, Nelson TM, Eskandari M. Correction to: Examining lung mechanical strains as influenced by breathing volumes and rates using experimental digital image correlation. Respir Res 2022; 23:130. [PMID: 35606760 PMCID: PMC9125815 DOI: 10.1186/s12931-022-02050-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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10
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Quiros KAM, Nelson TM, Sattari S, Mariano CA, Ulu A, Dominguez EC, Nordgren TM, Eskandari M. Mouse lung mechanical properties under varying inflation volumes and cycling frequencies. Sci Rep 2022; 12:7094. [PMID: 35501363 PMCID: PMC9059689 DOI: 10.1038/s41598-022-10417-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 03/30/2022] [Indexed: 01/23/2023] Open
Abstract
Respiratory pathologies alter the structure of the lung and impact its mechanics. Mice are widely used in the study of lung pathologies, but there is a lack of fundamental mechanical measurements assessing the interdependent effect of varying inflation volumes and cycling frequency. In this study, the mechanical properties of five male C57BL/6J mice (29–33 weeks of age) lungs were evaluated ex vivo using our custom-designed electromechanical, continuous measure ventilation apparatus. We comprehensively quantify and analyze the effect of loading volumes (0.3, 0.5, 0.7, 0.9 ml) and breathing rates (5, 10, 20 breaths per minute) on pulmonary inflation and deflation mechanical properties. We report means of static compliance between 5.4–16.1 µl/cmH2O, deflation compliance of 5.3–22.2 µl/cmH2O, percent relaxation of 21.7–39.1%, hysteresis of 1.11–7.6 ml•cmH2O, and energy loss of 39–58% for the range of four volumes and three rates tested, along with additional measures. We conclude that inflation volume was found to significantly affect hysteresis, static compliance, starting compliance, top compliance, deflation compliance, and percent relaxation, and cycling rate was found to affect only hysteresis, energy loss, percent relaxation, static compliance and deflation compliance.
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