Pressure ulcer prevention

Not just skin deep 

By : Mölnlycke Health Care, June 18 2013Posted in: Pressure ulcer prevention

High-risk extrinsic factors leading to pressure ulcers

Pressure ulcers can form in the deep tissue, so looking at the surface of the skin won’t necessarily tell you whether a patient is safe. And despite what the name suggests, pressure isn’t the only cause.

From our experience a number of extrinsic factors increase the risk of pressure ulcers, including pressure, shear, friction and microclimate1.

frictionFriction - A force that occurs when skin slides against another surface.  One example of friction is when gravity causes a patient to slip down the bed. The amount of friction depends on how easily the two surfaces can move across each other, and on how much pressure is applied1

Pressure - A force applied at right angles to the surface of the skin. PressurePressure compresses the tissue and can deform skin and soft tissues such as subcutaneous fat and muscle. Deformation is greater when pressure is applied over a bony prominence1


ShearShear - A result of friction, pressure and movement. Changes in position are likely to cause shear, such as when the head of the bed is raised or lowered. Shear forces tend to cause deeper tissue damage that may not be visible immediately1


MicroclimateMicro-Climate - The temperature and moisture levels where skin and support surface meet. Higher skin temperatures lead to sweating. The accumulation of heat and moisture has been shown to weaken skin and increase the amount of friction and shear between the skin and support surface1


'Superficial' versus 'deep' pressure ulcers: Possible difference in development 

Expert opinion on the causes of pressure ulcers has evolved. We now believe that different types of pressure ulcers may develop in different ways: shallower pressure ulcers are thought to start at the surface of the skin, while those that are more severe are thought to start in the deep tissue1

Outside in/top down pressure ulcers 

  • Caused by superficial damage 
  • Stage I and II pressure ulcers 

Friction and shear at the surface of the skin (or in other factors such as irritant dermatitis) may cause superficial damage. This may also lead to increased shear and pressure in deeper tissues, which results in deeper damage1

Inside out/ bottom up pressure ulcers 

  • Caused by deep-tissue damage
  • Stage III and IV pressure ulcers

Pressure and shear cause deep tissue damage near a bony prominence, which then extends outwards towards the surface of the skin1




  1. World Union of Wound Healing Societies (WUWHS) Consensus Document. Role of dressings in pressure ulcer prevention. Wounds International, 2016.


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