Investigation into the effect of pressure and shear on tissue viability of human skin.

Pressure ulcers are a significant problem in healthcare, not only affecting the
quality of life, morbidity and mortality of patients but also in terms of
healthcare costs. The prevalence of pressure ulcers in healthcare institutions
in the Netherlands was on average 8.3% (range 0% - 24%) in 2012. These figures
are comparable with other Western countries such as UK, Canada and the USA .
Most pressure ulcers in healthcare institutions in the Netherlands heal within
three months, but in the home care situation almost 50% of the pressure ulcers
do not heal within six months. The costs associated with pressure ulcers in the
Netherlands alone is over 200 million Euros annually.
Although the exact aetiology of pressure ulcers is still under debate, there is
consensus that pressure ulcers develop when tissue is devitalized. Tissue
viability depends on the microcirculation for the exchange of oxygen, carbon
dioxide, nutrients, water and waste products. If the microcirculation is
blocked, waste products accumulate and an oxygen deficiency arises, leading to
deterioration of the cells and the tissues. A few factors are directly linked
to the development of pressure ulcers: immobility, mechanical loading (pressure
and/or shear), moisture and ischemia. Immobility is seen as a prerequisite for
the development of a pressure ulcer, and also has an effect on the mechanical
load exerted on the tissue.
If loading is persistent for a longer period of time, tissue damage can occur
as a direct result of internal stresses or as an indirect results of changed
blood circulation.
To improve prevention of pressures ulcers, more knowledge is needed on the
relation between loading on the skin and the change in blood circulation. In
particular, the effect of shear on the skin microcirculation is unknown. Within
this research we want to investigate the relation between pressure and/or shear
and the change in circulation and whether this response changed with age of
patient groups.

This study will investigate the effect of shear and pressure on tissue
viability of human skin. Skin vitality is determined by tissue oxygenation and
blood flow, measured with the 'Oxygen to See'. The focus will be on individual
response patterns and possibly identification of groups of response patterns.
The aim of this study is to gather new knowledge on the effect of shear and
thereby help in quantifying the risk for development of pressure ulcers.

Experimental, non-randomised intervention study. The intervention is systematic
application of pressure and shear forces on the skin.

Application of eight different randomised (block randomisation) pressure and
shear combinations on the sacrum. Each condition start with a one minute
baseline (no load), followed by application of the load during 5 minutes and
after load removal the reaction will be measured for 7.5 minutes.

Participants will be asked to come to the laboratory and lie still for 1 or 2
hours consecutive (in total 2 hours). The application of pressure and shear
forces could potentially lead to skin damage. The range of forces stays well
within the range of normal sitting and lying and is well within range of
comparable studies. Also the loading time of 5 minutes is within range of
normal sitting duration. Therefore we expect the risk for skin damage to be
low. There are no direct benefits for subjects participating in this study.