Biomedical Engineering Reference
In-Depth Information
Fig. 7.18 a Path 3 and
b path 4 indicated by yellow
markers
7.1.5.2 Stress Analysis
Tissue stress analysis in lateral body posture is based on two additional node paths,
path 3 and path 4. Both paths originate at the bone surface of the trochanter major
at the point of maximum normal stress (path 3) and maximum shear stress (path 4)
and proceed towards the muscle tissue to skin level, Fig.
7.18
.
Figure
7.19
a depicts normal stress S
33
along node path 3 of all the inves-
tigated bedding systems (LS2 with varying membrane pressure and foam
mattress material). Figure
7.19
b depicts the bedding systems which caused
lowest tissue stress. In the same manner, Fig.
7.20
show shear stress along node
path 4.
From Figs.
7.19
and
7.29
it can be concluded that the system variations LS2/
F0.5 and LS2/F0.75 at a membrane pressure of 3 mbar minimize tissue normal
and shear stress. The system combination LS2/F0.5 at 3 mbar membrane
pressure thus represents the ideal system in the recumbent as well as in the
lateral body posture.
