1
|
Gupta S, Singh G, Chanda A. Prediction of diabetic foot ulcer progression: a computational study. Biomed Phys Eng Express 2021; 7. [PMID: 34560679 DOI: 10.1088/2057-1976/ac29f3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 09/24/2021] [Indexed: 01/13/2023]
Abstract
The development of foot ulcers is a common consequence of severe diabetes. Due to vascular disorders and impeded healing caused by the disease, most foot ulcers have been reported to be affected by body weight and progress with time. Also, abnormal distribution of plantar pressures has been observed to cause the formation of additional ulcers, which may collectively lead to traumatic amputations. While a study of such pathophysiology is not possible through experiments, a few computational modelling works have investigated diabetic foot ulcers. To date, ulcers with a few sizes and locations have been studied, and their effect on the plantar stresses has been quantified. In this work, we have attempted to study the effect of all possible ulcer locations on the generated plantar peak stresses and peak stress locations where additional ulcers may form. Also, the effect of ulcer location on the possible ulcer growth was investigated. A full-scale foot model was developed and a total of 52 ulcer locations were simulated separately, with standing and walking loads. The generated stresses were normalised with the foot size and statistically analysed to develop novel formulations for predicting peak plantar stresses and their locations for any known ulcer location. The results from this study are anticipated to provide important guidelines to doctors and medical practitioners for predicting foot ulcer progression in diabetic patients with existing ulcers and allow the administration of timely preventive interventions.
Collapse
Affiliation(s)
- Shubham Gupta
- Centre for Biomedical Engineering, Indian Institute of Technology (IIT), Delhi, India
| | - Gurpreet Singh
- Centre for Biomedical Engineering, Indian Institute of Technology (IIT), Delhi, India
| | - Arnab Chanda
- Centre for Biomedical Engineering, Indian Institute of Technology (IIT), Delhi, India.,Department of Biomedical Engineering, All India Institute of Medical Sciences (AIIMS), Delhi, India
| |
Collapse
|
2
|
Casey DT, Bou Jawde S, Herrmann J, Mori V, Mahoney JM, Suki B, Bates JHT. Percolation of collagen stress in a random network model of the alveolar wall. Sci Rep 2021; 11:16654. [PMID: 34404841 PMCID: PMC8371101 DOI: 10.1038/s41598-021-95911-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 07/28/2021] [Indexed: 11/21/2022] Open
Abstract
Fibrotic diseases are characterized by progressive and often irreversible scarring of connective tissue in various organs, leading to substantial changes in tissue mechanics largely as a result of alterations in collagen structure. This is particularly important in the lung because its bulk modulus is so critical to the volume changes that take place during breathing. Nevertheless, it remains unclear how fibrotic abnormalities in the mechanical properties of pulmonary connective tissue can be linked to the stiffening of its individual collagen fibers. To address this question, we developed a network model of randomly oriented collagen and elastin fibers to represent pulmonary alveolar wall tissue. We show that the stress-strain behavior of this model arises via the interactions of collagen and elastin fiber networks and is critically dependent on the relative fiber stiffnesses of the individual collagen and elastin fibers themselves. We also show that the progression from linear to nonlinear stress-strain behavior of the model is associated with the percolation of stress across the collagen fiber network, but that the location of the percolation threshold is influenced by the waviness of collagen fibers.
Collapse
Affiliation(s)
- Dylan T Casey
- Depatment of Medicine, University of Vermont Larner College of Medicine, 149 Beaumont Ave, Burlington, VT, 05405, USA
- Complex Systems Center, University of Vermont, Burlington, VT, USA
| | - Samer Bou Jawde
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Jacob Herrmann
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Vitor Mori
- Depatment of Medicine, University of Vermont Larner College of Medicine, 149 Beaumont Ave, Burlington, VT, 05405, USA
| | - J Matthew Mahoney
- Department of Neurological Science, University of Vermont Larner College of Medicine, Burlington, VT, USA
- The Jackson Laboratory, Bar Harbor, ME, USA
| | - Béla Suki
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Jason H T Bates
- Depatment of Medicine, University of Vermont Larner College of Medicine, 149 Beaumont Ave, Burlington, VT, 05405, USA.
| |
Collapse
|
3
|
Guérin C, Bayat S, Noury N, Cour M, Argaud L, Louis B, Terzi N. Regional lung viscoelastic properties in supine and prone position in a porcine model of acute respiratory distress syndrome. J Appl Physiol (1985) 2021; 131:15-25. [PMID: 33982595 DOI: 10.1152/japplphysiol.00104.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Regional viscoelastic properties of thoracic tissues in acute respiratory distress syndrome (ARDS) and their change with position and positive end-expiratory pressure (PEEP) are unknown. In an experimental porcine ARDS, dorsal and ventral lung (R2,L and E2,L) and chest wall (R2,cw and E2,cw) viscoelastic resistive (R) and elastic (E) parameters were measured at 20, 15, 10, and 5 cmH2O PEEP in supine and prone position. E2 and R2 were obtained by fitting the decay of pressure after end-inspiratory occlusion to the equation: Pviscmax (t) =R2 e-t/τ2, where t is the length of occlusion and τ2 time constant. E2 was equal to R2/τ2. R2,cw and E2,cw were measured from esophageal, dorsal, and ventral pleural pressures. Global R2,L and E2,L were obtained from the global transpulmonary pressure (airway pressure-esophageal pressure), and regional R2,L and E2,L from the dorsal and ventral airway pressure-pleural pressure difference. Lung ventilation was measured by electrical impedance tomography (EIT). Global R2,cw and E2,cw did not change with PEEP or position. Global R2,L [median(Q1-Q3)] was 37.1 (11.0-65.1), 5.1 (4.3-5.5), 12.1 (8.4-19.5), and 41.0 (26.6-53.5) cmH2O/L/s in supine, and 15.3 (9.1-41.9), 7.9 (5.7-11.0), 8.0 (5.1-12.1), and 12.9 (6.4-19.4) cmH2O/L in prone from 20 to 5 cmH2O PEEP (P = 0.06 for PEEP and P = 0.06 for position). Dorsal R2,L significantly and positively correlated with the amount of collapse measured with EIT. Global and regional lung and chest wall viscoelastic parameters can be described by a simple rheological model. Regional E2 and R2 were uninfluenced by PEEP and position except for PEEP on dorsal E2,L and position on dorsal E2,cw.NEW & NOTEWORTHY In a porcine model of acute respiratory distress syndrome, data were successfully fitted to a rheological model of the nonlinear behavior of viscoelastic properties of lung and chest wall at different positive end-expiratory pressure (PEEP) in the supine and prone position. Prone position tended to decrease lung viscoelastic resistive component. PEEP had a significant effect on dorsal lung viscoelastic elastance. Finally, lung viscoelastic resistance correlated with the amount of lung collapse assessed by electrical impedance tomography.
Collapse
Affiliation(s)
- Claude Guérin
- Médecine Intensive-Réanimation, Groupement Hospitalier Centre, Hôpital Edouard Herriot, Lyon, France.,Université de Lyon, Lyon, France.,Laboratoire d'explorations fonctionnelles respiratoires, CHU Grenoble-Alpes, Grenoble, France
| | - Sam Bayat
- Laboratoire d'explorations fonctionnelles respiratoires, CHU Grenoble-Alpes, Grenoble, France.,INSERM UA7 STROBE, Grenoble, France.,Université de Grenoble, Grenoble, France
| | | | - Martin Cour
- Médecine Intensive-Réanimation, Groupement Hospitalier Centre, Hôpital Edouard Herriot, Lyon, France.,Université de Lyon, Lyon, France
| | - Laurent Argaud
- Médecine Intensive-Réanimation, Groupement Hospitalier Centre, Hôpital Edouard Herriot, Lyon, France.,Université de Lyon, Lyon, France
| | - Bruno Louis
- Laboratoire d'explorations fonctionnelles respiratoires, CHU Grenoble-Alpes, Grenoble, France
| | - Nicolas Terzi
- Université de Grenoble, Grenoble, France.,Médecine intensive-Réanimation, CHU Grenoble-Alpes, Grenoble, France.,INSERM U1042, Grenoble, France
| |
Collapse
|
4
|
Maritz J, Agustoni G, Dragnevski K, Bordas SPA, Barrera O. The Functionally Grading Elastic and Viscoelastic Properties of the Body Region of the Knee Meniscus. Ann Biomed Eng 2021; 49:2421-2429. [PMID: 34075449 PMCID: PMC8455388 DOI: 10.1007/s10439-021-02792-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 05/05/2021] [Indexed: 12/29/2022]
Abstract
The knee meniscus is a highly porous structure which exhibits a grading architecture through the depth of the tissue. The superficial layers on both femoral and tibial sides are constituted by a fine mesh of randomly distributed collagen fibers while the internal layer is constituted by a network of collagen channels of a mean size of 22.14 \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\mu $$\end{document}μm aligned at a \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$30^{\circ }$$\end{document}30∘ inclination with respect to the vertical. Horizontal dog-bone samples extracted from different depths of the tissue were mechanically tested in uniaxial tension to examine the variation of elastic and viscoelastic properties across the meniscus. The tests show that a random alignment of the collagen fibers in the superficial layers leads to stiffer mechanical responses (E = 105 and 189 MPa) in comparison to the internal regions (E = 34 MPa). All regions exhibit two modes of relaxation at a constant strain (\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\tau _1 = 6.4$$\end{document}τ1=6.4 to 7.7 s, \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\tau _2$$\end{document}τ2 = 49.9 to 59.7 s).
Collapse
Affiliation(s)
| | - Greta Agustoni
- University of Oxford, Oxford, UK.,Department of Health Science and Technologies, ETH, Zurich, Switzerland
| | | | - Stéphane P A Bordas
- Institute of Computational Engineering Sciences, University of Luxembourg, Luxembourg, Luxembourg.,Institute of Research and Development, Duy Tan University, K7/25 Quang Trung, Danang, Vietnam.,Cardiff University, School of Engineering, Cardiff, UK
| | - Olga Barrera
- University of Oxford, Oxford, UK. .,School of Engineering, Computing and Mathematics, Oxford Brookes University, Wheatley Campus, Oxford, OX33 1HX, UK. .,Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan.
| |
Collapse
|
5
|
Walker M, Godin M, Harden JL, Pelling AE. Time dependent stress relaxation and recovery in mechanically strained 3D microtissues. APL Bioeng 2020; 4:036107. [PMID: 32984751 PMCID: PMC7500532 DOI: 10.1063/5.0002898] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Accepted: 08/02/2020] [Indexed: 02/06/2023] Open
Abstract
Characterizing the time-dependent mechanical properties of cells is not only necessary to determine how they deform but also to understand how external forces trigger biochemical-signaling cascades to govern their behavior. At present, mechanical properties are largely assessed by applying local shear or compressive forces on single cells grown in isolation on non-physiological 2D surfaces. In comparison, we developed the microfabricated vacuum actuated stretcher to measure tensile loading of 3D multicellular "microtissue" cultures. Using this approach, we here assessed the time-dependent stress relaxation and recovery responses of microtissues and quantified the spatial viscoelastic deformation following step length changes. Unlike previous results, stress relaxation and recovery in microtissues measured over a range of step amplitudes and pharmacological treatments followed an augmented stretched exponential behavior describing a broad distribution of inter-related timescales. Furthermore, despite the variety of experimental conditions, all responses led to a single linear relationship between the residual elastic stress and the degree of stress relaxation, suggesting that these mechanical properties are coupled through interactions between structural elements and the association of cells with their matrix. Finally, although stress relaxation could be quantitatively and spatially linked to recovery, they differed greatly in their dynamics; while stress recovery acted as a linear process, relaxation time constants changed with an inverse power law with the step size. This assessment of microtissues offers insights into how the collective behavior of cells in a 3D collagen matrix generates the dynamic mechanical properties of tissues, which is necessary to understand how cells deform and sense mechanical forces in vivo.
Collapse
Affiliation(s)
- Matthew Walker
- Department of Biology, University of Ottawa, Gendron Hall, 30 Marie Curie, Ottawa, Ontario K1N5N5, Canada
| | | | | | - Andrew E. Pelling
- Author to whom correspondence should be addressed:. Tel.: +1 613 562 5800 ext. 6965. Fax: +1 613 562 5190. URL:http://www.pellinglab.net
| |
Collapse
|
6
|
Quantification of Age-Related Lung Tissue Mechanics under Mechanical Ventilation. Med Sci (Basel) 2017; 5:medsci5040021. [PMID: 29099037 PMCID: PMC5753650 DOI: 10.3390/medsci5040021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 09/25/2017] [Accepted: 09/28/2017] [Indexed: 01/30/2023] Open
Abstract
Elderly patients with obstructive lung diseases often receive mechanical ventilation to support their breathing and restore respiratory function. However, mechanical ventilation is known to increase the severity of ventilator-induced lung injury (VILI) in the elderly. Therefore, it is important to investigate the effects of aging to better understand the lung tissue mechanics to estimate the severity of ventilator-induced lung injuries. Two age-related geometric models involving human bronchioles from generation G10 to G23 and alveolar sacs were developed. The first is for a 50-year-old (normal) and second is for an 80-year old (aged) model. Lung tissue mechanics of normal and aged models were investigated under mechanical ventilation through computational simulations. Results obtained indicated that lung tissue strains during inhalation (t = 0.2 s) decreased by about 40% in the alveolar sac (G23) and 27% in the bronchiole (G20), respectively, for the 80-year-old as compared to the 50-year-old. The respiratory mechanics parameters (work of breathing per unit volume and maximum tissue strain) over G20 and G23 for the 80-year-old decreased by about 64% (three-fold) and 80% (four-fold), respectively, during the mechanical ventilation breathing cycle. However, there was a significant increase (by about threefold) in lung compliance for the 80-year-old in comparison to the 50-year-old. These findings from the computational simulations demonstrated that lung mechanical characteristics are significantly compromised in aging tissues, and these effects were quantified in this study.
Collapse
|
7
|
Donovan GM. Systems-level airway models of bronchoconstriction. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2016; 8:459-67. [PMID: 27348217 DOI: 10.1002/wsbm.1349] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Revised: 03/23/2016] [Accepted: 05/18/2016] [Indexed: 01/26/2023]
Abstract
Understanding lung and airway behavior presents a number of challenges, both experimental and theoretical, but the potential rewards are great in terms of both potential treatments for disease and interesting biophysical phenomena. This presents an opportunity for modeling to contribute to greater understanding, and here, we focus on modeling efforts that work toward understanding the behavior of airways in vivo, with an emphasis on asthma. We look particularly at those models that address not just isolated airways but many of the important ways in which airways are coupled both with each other and with other structures. This includes both interesting phenomena involving the airways and the layer of airway smooth muscle that surrounds them, and also the emergence of spatial ventilation patterns via dynamic airway interaction. WIREs Syst Biol Med 2016, 8:459-467. doi: 10.1002/wsbm.1349 For further resources related to this article, please visit the WIREs website.
Collapse
Affiliation(s)
- Graham M Donovan
- Department of Mathematics, University of Auckland, Auckland, New Zealand
| |
Collapse
|