Implementation and Application of a Microstructurally Based Orthotropic Hyperelastic Model of Pulmonary Artery Mechanics under Normotensive and Hypertensive Conditions

Published

August 1, 2005

Author(s)

Yang Zhang, Martin Dunn, Elizabeth S. Drexler, Christopher N. McCowan, Andrew Slifka, Dunbar Ivy, R Shandas

Abstract

We implemented, validated, and applied a microstructurally based orthotropic hyperelastic constitutive model to simulate pulmonary artery mechanics under normotensive and hypoxic hypertensive conditions. The configuration of the model microstructure is a set of chemically cross-linked and mechanically entangled long molecular chains, similar to the structural protein framework seen in the medial layer of the arterial wall. The model micromechanics is governed by the entropic elasticity of these long chain molecules, the integration of which underlies the macro-level behavior of the whole artery. A finite element approach was adopted to implement the orthotropic hyperelastic constitutive model. Material parameters in the finite element model were determined via fitting model output to measured pressure-stretch results from normotensive and hypertensive trunks and branches obtained from a rat model of pulmonary hypertension. Results show: 1) a microstructural orthotropic hyperelastic model appears reasonable for the study of pulmonary artery mechanics; 2) typical tangent modulus values ranged from 200 ¿C 800 kPa for normotensive arteries ¿C this increased to beyond 1 MPa for hypertensive vessels; 3) the anisotropy of the arterial wall can be predicted by the preferential variation of the molecular chain dimensions in the longitudinal and circumferential directions; 4) cross-linking density of the molecular chains appears to be a key mechanism by which the pulmonary artery stiffens in hypertension. This represents the first application of a microstructural orthotropic hyperelastic model to pulmonary artery mechanics under normotensive and hypertensive conditions. Ongoing work will include a separate unit element for the adventitial layer and linking of the existing generic molecular chain properties to specific mechanical properties seen for elastin and collagen molecules.

Citation

Journal of Applied Physiology

Volume

33

Issue

8

Pub Type

Journals

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Keywords

cross-linking, orthotropic hyperelasticity, pulmonary hypertension, tangent modulus

Citation

Zhang, Y. , Dunn, M. , Drexler, E. , McCowan, C. , Slifka, A. , Ivy, D. and Shandas, R. (2005), Implementation and Application of a Microstructurally Based Orthotropic Hyperelastic Model of Pulmonary Artery Mechanics under Normotensive and Hypertensive Conditions, Journal of Applied Physiology, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=30006 (Accessed December 12, 2024)