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Research Papers

Viscoelastic Properties of Human Tracheal Tissues

[+] Author and Article Information
Farzaneh Safshekan

Faculty of Biomedical Engineering,
Amirkabir University of Technology,
424 Hafez Avenue,
Tehran 15875-4413, Iran
e-mail: f.safshekan@aut.ac.ir

Mohammad Tafazzoli-Shadpour

Faculty of Biomedical Engineering,
Amirkabir University of Technology,
424 Hafez Avenue,
Tehran 15875-4413, Iran
e-mail: Tafazoli@aut.ac.ir

Majid Abdouss

Chemistry Department,
Amirkabir University of Technology,
424 Hafez Avenue,
Tehran 15875-4413, Iran
e-mail: phdabdouss44@aut.ac.ir

Mohammad B. Shadmehr

Tracheal Diseases Research Center,
National Research Institute of Tuberculosis and
Lung Diseases (NRITLD),
Shahid Beheshti University of Medical Sciences,
Darabad Avenue, Shahid Bahonar Roundabout,
Tehran 19558-41452, Iran
e-mail: mbshadmehr@sbmu.ac.ir

1Corresponding author.

Manuscript received June 10, 2016; final manuscript received August 17, 2016; published online November 4, 2016. Assoc. Editor: Guy M. Genin.

J Biomech Eng 139(1), 011007 (Nov 04, 2016) (9 pages) Paper No: BIO-16-1247; doi: 10.1115/1.4034651 History: Received June 10, 2016; Revised August 17, 2016

The physiological performance of trachea is highly dependent on its mechanical behavior, and therefore, the mechanical properties of its components. Mechanical characterization of trachea is key to succeed in new treatments such as tissue engineering, which requires the utilization of scaffolds which are mechanically compatible with the native human trachea. In this study, after isolating human trachea samples from brain-dead cases and proper storage, we assessed the viscoelastic properties of tracheal cartilage, smooth muscle, and connective tissue based on stress relaxation tests (at 5% and 10% strains for cartilage and 20%, 30%, and 40% for smooth muscle and connective tissue). After investigation of viscoelastic linearity, constitutive models including Prony series for linear viscoelasticity and quasi-linear viscoelastic, modified superposition, and Schapery models for nonlinear viscoelasticity were fitted to the experimental data to find the best model for each tissue. We also investigated the effect of age on the viscoelastic behavior of tracheal tissues. Based on the results, all three tissues exhibited a (nonsignificant) decrease in relaxation rate with increasing the strain, indicating viscoelastic nonlinearity which was most evident for cartilage and with the least effect for connective tissue. The three-term Prony model was selected for describing the linear viscoelasticity. Among different models, the modified superposition model was best able to capture the relaxation behavior of the three tracheal components. We observed a general (but not significant) stiffening of tracheal cartilage and connective tissue with aging. No change in the stress relaxation percentage with aging was observed. The results of this study may be useful in the design and fabrication of tracheal tissue engineering scaffolds.

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Figures

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Fig. 1

Schematics of (a) human trachea (composed of cartilaginous rings, which are completed by smooth muscle and connected to each other by narrow connective tissue layers) and the test samples along with the uniaxial tension direction, and (b) the strain applied on each sample, consisting of a preconditioning phase (six cycles of loading/unloading) and the stress relaxation phase (with application of a constant strain amplitude for relaxation over a period of 300 s)

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Fig. 2

Average stress relaxation curves corresponding to tracheal (a) cartilage, (b) connective tissue, and (c) smooth muscle at different strain levels

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Fig. 3

Normalized stress–time data at different strain levels for (a) tracheal cartilage, (b) connective tissue, and (c) smooth muscle

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Fig. 4

Schapery (SCH), modified superposition (MSP), quasi-linear viscoelastic (QLV), and three-term Prony series (PRO) models fitted to the experimental stress relaxation data for tracheal cartilage tissue at 5% and 10% strain levels

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Fig. 5

Schapery (SCH), modified superposition (MSP), quasi-linear viscoelastic (QLV), and three-term Prony series (PRO) models fitted to the experimental stress relaxation data for tracheal connective tissue at 20%, 30%, and 40% strain levels

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Fig. 6

Schapery (SCH), modified superposition (MSP), quasi-linear viscoelastic (QLV), and three-term Prony series (PRO) models fitted to the experimental stress relaxation data for tracheal smooth muscle at 20%, 30%, and 40% strain levels

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Fig. 7

Age-based comparison of the experimental stress relaxation data corresponding to (a) tracheal cartilage at 10% strain level, (b) connective tissue at 30% strain, and (c) smooth muscle at 30% strain

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