Pressure Injuries and Staging

What is a Pressure Injury?

A pressure injury is localized damage to the skin and underlying soft tissue usually over a bony prominence or related to a medical or other device. The injury can present as intact skin or an open ulcer and may be painful. The injury occurs as a result of intense and/or prolonged pressure or pressure in combination with shear. The tolerance of soft tissue for pressure and shear may also be affected by microclimate, nutrition, perfusion, co-morbidities and condition of the soft tissue.1


Pressure and Shear

  • Used with permission L. Edsberg. Designed by Knightime Designs


    Pressure - Pressure is the force (per unit area) exerted perpendicular to the skin surface.2 Pressure damages the skin and underlying tissues by (1) directly deforming and damaging tissue; (2) compressing small blood vessels hindering blood flow and nutrient supply and (3) through ischemia-reperfusion injury. When pressure is redistributed over a greater surface area, the pressure is less intense in any one area.3

  • Used with permission L. Edsberg. Designed by Knightime Designs


    Shear - Shear stress is the force (per unit area) exerted parallel to the tissue.2 Shear strain is the actual distortion or deformation of tissue as a result of shear stress. Some shear strain occurs at rest. Shear strain is intensified in certain clinical situations (e.g., raising the head of the bed > 30 degrees; dragging rather than lifting while repositioning). One layer of tissue slides over another deforming adipose and muscle tissue and disrupting blood flow.

  1. Edsberg, L. E., Black, J. M., Goldberg, M., McNichol, L., Moore, L. , & Sieggreen, M. (2016). Revised National Pressure Ulcer Advisory Panel Pressure Injury Staging System. J Wound Ostomy Continence Nurs, 43(6), 1-13. doi: 10.1097/WON.0000000000000281 Fletcher, J. (2012). Device related pressure ulcers made easy. . Wounds UK, 8(2).
  2. National Pressure Ulcer Advisory Panel. (2007). Terms and Definitions to Support Surfaces. Retrieved July 30,2016, from
  3. National Pressure Ulcer Advisory Panel, European Pressure Ulcer Advisory Panel, & Pan Pacific Pressure Injury Alliance. (2014). Prevention and Treatment of Pressure Ulcers: Clinical Practice Guideline (Emily Haesler Ed.). Osborne Park, Western Australia: Cambridge Media.