Modeling the interaction between micro-climate factors and moisture-related skin-support friction during patient repositioning in bed
Thyrza Jagt

Supervisor: Fred Vermolen

Site of the project: TU Delft

start of the project: January 2014

In June 2014 the Interim Thesis has appeared and a presentation has been given.

The Master project has been finished in April 2015 by the completion of the Masters Thesis and a final presentation has been given. For working address etc. we refer to our alumnipage.

Summary of the master project:
Immobile patients that are limited to spending their time in bed predominantly are prone to skin breakdown as a consequence of moisture development between the skin and mattress. This wetness results from transpiration or urine. Due to wetting of the skin, the mechanical properties of the skin change and the friction between the skin and the mattress increases. This increase implies that the shear forces at the interface between the skin and mattress increase when a patient is moved or relocated on bed for daily care. This mechanism increases the likelihood of the development of a superficial pressure ulcer.

In this research, we will analyze, use and improve the phenomenological model developed by Gefen for the simulation of micro-climate factors. This model contains an interaction between the amount of transpiration and ambient temperature, increase of humidity, increase in the skin-support contact pressure. Furthermore, we will analyze and use a finite-element model for the mechanical support and equilibrium of tissue interacting with the mattress where the skin and subcutaneous tissue are incorporated. This interaction poses a contact problem where the surface of contact between the skin and mattress has to be determined. In this work, we will focus on the combination of the two models, where we aim at predicting the likelihood of the development of a superficial pressure ulcer in the course of time upon moving the patient over the surface of the mattress. This is done by using the finite-element method over the domain containing the tissue as well as the mattress. As an output parameter the shear strain will be important to estimate the probability that skin break-down (failure) occurs. Since the mechanical properties of skin change with local humidity, the skin will deteriorate in the course of time due to the build-up of moisture levels. In this MSc-thesis, we aim at a coupling of the micro-climate factors to the mechanical equilibrium which consists of a contact problem. Furthermore, skin behaves differently from rigid materials, hence most likely Hooke's Law will not be appropriate for the modeling.

Figuur 1: Hospital bed

Figuur 2: superficial pressure ulcer

Contact information: Kees Vuik

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