Mechanical behavior of the airway wall in respiratory disease

Maghsoudi-Ganjeh, Mohammad; Sattari, Samaneh; Eskandari, Mona

doi:10.1016/j.cophys.2021.05.008

Cited by 14 publications

(8 citation statements)

References 64 publications

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“…In addition to individual contribution, the cross-linking and interconnection between constituents of extracellular matrix (ECM), including collagen, elastin, and proteoglycans are responsible for the mechanical properties of the lung and undergo remodeling in pathological conditions [ 84 , 85 ]. However, their contribution in various stages of stretching is debated: traditionally, collagen and elastin fibers are thought to act independently where elastin is engaged in the low strain regime and where collagen acts as a stop-length, preventing the lung from over distending [ 86 , 87 , 88 ].…”

Section: Discussionmentioning

confidence: 99%

Effects of tissue degradation by collagenase and elastase on the biaxial mechanics of porcine airways

et al. 2023

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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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Section: Discussionmentioning

confidence: 99%

Effects of tissue degradation by collagenase and elastase on the biaxial mechanics of porcine airways

et al. 2023

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“…This does not include recent deaths associated with the global COVID-19 pandemic which, as of September 2021, surpasses 4.6 million deaths 6 . Diagnosis and treatment of these pulmonary diseases is a massive economic burden; for example, only COPD in the United States alone, is predicted to cost $800 billion in direct medical bills over the next 20 years 7 , 8 . It is known that pulmonary diseases can change the structure of the lung and in turn alter its mechanical properties 9 – 12 , 56 ; for example, obstructive diseases, such as asthma and chronic bronchitis, interrupt the airflow due to smooth muscle thickening, mucosal growth, and loss of lung elastic recoil 13 – 15 .…”

Section: Introductionmentioning

confidence: 99%

Mouse lung mechanical properties under varying inflation volumes and cycling frequencies

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Nelson

Sattari

et al. 2022

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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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“…Ventilator efficacy and pulmonary disease are also dependent on tissue compliancy [ 25 , 71 , 72 ]; high compliance is found in lungs experiencing obstructive diseases such as emphysema and reduced compliance is found in restrictive lung diseases such as fibrosis [ 73 – 75 ]. Previous studies analyzing these global organ compliances from pressure–volume loops have observed lower lung compliance as higher lung volumes were reached due to incremental lung volume gains at higher pressures [ 74 ]; however, our local compliance measures linking mean surface strains to global pressures finds that the regional tissue compliance increases at higher inflation volumes as well as at slower breathing rates.…”

Section: Discussionmentioning

confidence: 99%

Examining lung mechanical strains as influenced by breathing volumes and rates using experimental digital image correlation

et al. 2022

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Background Mechanical ventilation is often employed to facilitate breathing in patients suffering from respiratory illnesses and disabilities. Despite the benefits, there are risks associated with ventilator-induced lung injuries and death, driving investigations for alternative ventilation techniques to improve mechanical ventilation, such as multi-oscillatory and high-frequency ventilation; however, few studies have evaluated fundamental lung mechanical local deformations under variable loading. Methods Porcine whole lung samples were analyzed using a novel application of digital image correlation interfaced with an electromechanical ventilation system to associate the local behavior to the global volume and pressure loading in response to various inflation volumes and breathing rates. Strains, anisotropy, tissue compliance, and the evolutionary response of the inflating lung were analyzed. Results Experiments demonstrated a direct and near one-to-one linear relationship between applied lung volumes and resulting local mean strain, and a nonlinear relationship between lung pressures and strains. As the applied air delivery volume was doubled, the tissue surface mean strains approximately increased from 20 to 40%, and average maximum strains measured 70–110%. The tissue strain anisotropic ratio ranged from 0.81 to 0.86 and decreased with greater inflation volumes. Local tissue compliance during the inflation cycle, associating evolutionary strains in response to inflation pressures, was also quantified. Conclusion Ventilation frequencies were not found to influence the local stretch response. Strain measures significantly increased and the anisotropic ratio decreased between the smallest and greatest tidal volumes. Tissue compliance did not exhibit a unifying trend. The insights provided by the real-time continuous measures, and the kinetics to kinematics pulmonary linkage established by this study offers valuable characterizations for computational models and establishes a framework for future studies to compare healthy and diseased lung mechanics to further consider alternatives for effective ventilation strategies.

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Mechanical behavior of the airway wall in respiratory disease

Cited by 14 publications

References 64 publications

Effects of tissue degradation by collagenase and elastase on the biaxial mechanics of porcine airways

Effects of tissue degradation by collagenase and elastase on the biaxial mechanics of porcine airways

Mouse lung mechanical properties under varying inflation volumes and cycling frequencies

Examining lung mechanical strains as influenced by breathing volumes and rates using experimental digital image correlation

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