What is pressure?

05/08/2015 11:30:13

In the second of our ‘Pressure, Friction, Shear’ blog posts, we look this week at pressure.

What is pressure?
Pressure can be defined as; ‘Continuous physical force exerted on or against an object by something in contact with it’(1)  and as you would guess, it is a key force in the development of pressure ulcers.
It can also be defined mathematically as ‘force ÷ area’
Pressure is a force acting at a right angle to the surface, i.e. the ‘normal’ force that acts on people and objects every day(2).
We are able to tolerate high pressure on the skin. 
Divers for example experience very high hydrostatic pressures and don’t get pressure ulcers, because the pressure is even therefore there is no shear(3).
Where pressure ulcers occur, the forces (pressure) acting on the skin deforms the cells. The deformation can restrict blood supply and deform or damage the cell membranes, both of which can cause cell death.
As pressure from a patient’s body is applied to the support surface, pressure acts down, and shear stress is a component of the reacting force of compression, resulting in tissue deformation. 
How can pressure be prevented?
Pressure can’t be prevented – a patient on a medical support surface, like a mattress cover, will always have a weight that pushes down on that surface, and will therefore exert pressure on the skin. 
BUT - pressure can be redistributed to lower the amount of pressure building up on one particular area.
For example, on a reactive foam support surface, pressure redistribution is achieved through the use of a stretch mattress cover. 
This helps because:
  • There is no ‘hammocking’ of the fabric due to the stretch properties of the material 
  • By fully immersing and enveloping the patient, the load is fully spread over a greater contact area – because pressure = force ÷ area, by increasing the area you decrease the pressure
Want to know more? 
Speak with one of our technical experts for more information on the impacts of pressure, shear and friction enquiries@dartexcoatings.com 
(1) http://www.oxforddictionaries.com/definition/english/pressure 
(2) http://medical-dictionary.thefreedictionary.com/normal+force 
(3) The role of shear forces and shear strains in the development of pressure ulcers – BHTA presentation. Oomens, C. and Bader, D. (2014) http://www.bhta.net/sites/default/files/Dr.%20Cees%20Oomens%20presentation.pdf


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