Bedsores are caused by pressure against the skin that limits blood flow to the skin and nearby tissues. Other factors related to limited mobility can make the skin vulnerable to damage and contribute to the development of pressure sores. Three primary contributing factors are:

  • Sustained pressure. When your skin and the underlying tissues are trapped between bone and a surface such as a wheelchair or a bed, the pressure may be greater than the pressure of the blood flowing in the tiny vessels (capillaries) that deliver oxygen and other nutrients to tissues. Without these essential nutrients, skin cells and tissues are damaged and may eventually die.

    This kind of pressure tends to happen in areas that aren't well-padded with muscle or fat and that lie over a bone, such as your spine, tailbone, shoulder blades, hips, heels and elbows.

  • Friction. Friction is the resistance to motion. It may occur when the skin is dragged across a surface, such as when you change position or a care provider moves you. The friction may be even greater if the skin is moist. Friction may make fragile skin more vulnerable to injury.
  • Shear. Shear occurs when two surfaces move in the opposite direction. For example, when a hospital bed is elevated at the head, you can slide down in bed. As the tailbone moves down, the skin over the bone may stay in place — essentially pulling in the opposite direction. This motion may injure tissue and blood vessels, making the site more vulnerable to damage from sustained pressure.
Mar. 25, 2014