Abstract
Localized ischemia, impaired interstitial fluid flow, and sustained mechanical loading of cells have all been hypothesized as mechanisms of pressure ulcer (PrU) etiology. Time-varying loading has experimentally been shown to increase fluid flow in human skin in vivo. Towards the design of prophylactic protocols and treatment modalities for PrU management there is a need for an analytical model to investigate the local fluid flow characteristics of skin tissue under time-varying loading. In this study, a triphasic mixture theory model with constituents of extracellular matrix, interstitial fluid, and blood was calibrated and validated and used to investigate stress and fluid velocity under quasi-static and time-varying loading conditions, respectively. Four input strain profiles were considered, including uniform, geometric circular segment, Gaussian, and Hertz-type strain profiles. Calibrated bulk and shear modulus (κ;=227.7kPa, µ=1.04kPa) were on the same order of magnitude as literature. Fluid velocities were investigated for apparent strain amplitudes of 100-700μϵ and frequencies of 10-80Hz. At the lowest amplitude and frequency, interstitial fluid velocities were on the same order of magnitude as literature values, 1 micrometers/s and 1 mm/s, respectively. Interstitial fluid and blood velocity both experienced significant increases with increasing amplitude and frequency. The study demonstrated the ability to analytically predict quasi-static stress profiles as well as predict fluid velocity increases in cyclically loaded soft tissues by employing quasi-static mechanics and mixture theory models. Consequently, this study builds a strong foundation for use in the development of vibrational support surfaces for use in prophylactic protocols and adjunctive treatment modalities for PrU management
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Mechanical Engineering
Committee Chair
Eric Nauman
Date of Award
Spring 2015
Recommended Citation
Zakrajsek, Anne Dye, "A three constituent mixture theory model of cutaneous and subcutaneous tissue in the context of neonatal pressure ulcer etiology and prevention" (2015). Open Access Dissertations. 603.
https://docs.lib.purdue.edu/open_access_dissertations/603
First Advisor
Eric Nauman
Committee Member 1
Charles Krousgrill
Committee Member 2
Darryl Dickerson
Committee Member 3
Lynetta Freeman