FOURTEENTH ANNUAL EUROPEAN PRESSURE ULCER ...
FOURTEENTH ANNUAL EUROPEAN PRESSURE ULCER ...
FOURTEENTH ANNUAL EUROPEAN PRESSURE ULCER ...
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Thursday September 1st<br />
Proceedings of the 14th Annual European Pressure Ulcer Meeting<br />
Oporto, Portugal<br />
Relationship Between “Tilt in Space” Wheelchair Function and Risk of Pressure Ulcer<br />
Development<br />
Introduction<br />
Olesen, C.G. 1* , Siefert, A. 2 , de Zee, M 3 , Pankoke, S. 2 , Rasmussen, J. 1<br />
1* M-Tech, Aalborg University, Denmark, (cgo@m-tech.aau.dk)<br />
2 Wölfel Beratende Ingenieure GmbH + Co.KG, Würzburg, Germany<br />
3 Department of Health Science and Technology, Aalborg University, Denmark,<br />
It is well acknowledged that sustained mechanical<br />
loading of soft tissues causes pressure ulcers [1].<br />
The wheelchair adjustments affect the tissue loading in<br />
the sense that the tissue stresses, and thereby the risk<br />
of ulceration, change when the seated posture is<br />
adapted [2]. This study focuses on a basic wheelchair<br />
adjustment called the “Tilt-in-Space” function, with<br />
which many wheelchairs are equipped. The tilt-inspace<br />
function enables the cushion and backrest to<br />
incline while the angle between the cushion and<br />
backrest is kept constant [3]. When the tilt-in-space<br />
function is used, the cushion and the backrest reaction<br />
forces change, which causes a change in tissue<br />
deformation under the buttocks. This study focuses on<br />
investigating how much the reaction forces between<br />
the body and the chair change when tilted in space;<br />
this information will then be used to estimate how the<br />
buttock tissue is deformed.<br />
Methods<br />
The Seated Human computational model from the<br />
AnyBody Modeling System was used to calculate<br />
reaction forces acting between the seat and the<br />
human for different postures. The model has been<br />
validated with respect to the calculated forces by<br />
experimental data.<br />
Figure 1 show the seated AnyBody model not tilted, and<br />
tilted<br />
The “Tilt-in-Space” function was modeled by fixing the<br />
cushion and backrest at a 90° angle relative to each<br />
other. The chair was then rotated backwards with 5°<br />
increments to a maximal inclination of 45° and the<br />
reaction forces for each increment were computed.<br />
The calculated reaction forces were then applied as<br />
boundary conditions to the human body model<br />
CASIMIR. In the interest of limiting computational time,<br />
the finite element model only comprises the buttocks.<br />
Finally the tissue deformation changes caused by the<br />
“Tilt-in-Space” function were evaluated. The FE-model<br />
83<br />
used was a commercially available model developed<br />
by Wölfel, Würzburg, Germany [4].<br />
Figure 2 Human body model CASIMIR used for<br />
calculating tissue deformation<br />
Results<br />
Preliminary results show that the reaction forces<br />
between the seat and the buttocks change, and this<br />
leads to a change in buttocks tissue deformation.<br />
Discussion<br />
The preliminary results found in this study indicate that<br />
the “Tilt-in-Space” function found on many wheelchairs<br />
is not optimal, with respect to risk of developing<br />
pressure ulcers.<br />
Clinical relevance<br />
This work is clinical relevant for wheelchair designers<br />
who aim to enhance wheelchair design with respect to<br />
prevention of pressure ulcers.<br />
Acknowledgements<br />
This work was supported by the project Minimizing the<br />
risk of developing a pressure ulcer (ERDFN-09-0070),<br />
supported by Growth Fund North Denmark and<br />
European Regional Development Fund.<br />
Conflict of Interest<br />
There were no conflict of interests<br />
References<br />
[1] Romanelli M. et.al. Science and Practice of<br />
Pressure Ulcer Management, Springer, 2005<br />
[2] Bush TR. et.al. J.Biomech.Eng. 129: 1: 58-65,<br />
2007.<br />
[3] Michael SM et.al. Clin.Rehabil. 21: 12: 1063-1074,<br />
2007<br />
[4] Siefert A. et.al. Int.J.Ind.Ergonomics 38: 5-6: 410,<br />
2008.<br />
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