Extrinsic risk factors

Four extrinsic factors1, 3 are most commonly reported to pose a risk of tissue damage:

  1. Pressure1, 3
  2. Shear1, 3, 4, 5
  3. Skin microclimate1, 6 – Heat and humidity
  4. Friction1 – This force has historically been included in this list but is now discussed separately and the wounds described as friction wounds.

It is often the combination of forces that create the highest risk for a vulnerable patient. Tissue deformation happens in soft tissue, adipose tissue, connective tissue and muscle when these forces occur causing stresses and strain affecting the perfusion and cellular mechanisms essential for normal functioning. In the clinical setting non uniform forces are usually witnessed and shear forces are often present. Age, lifestyle, chronic illnesses can affect the ability to respond to these forces.