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How Pressure Ulcers and Injuries Form

Even a healthy person can begin to develop pressure ulcers in less than a day if left in one position. It helps to know where how pressure ulcers develop and what you can do to prevent them.

Cross section of skin showing layers of healthy skin and bone. Arrows show surface pressure and body-weight pressure on skin. Subcutaneous layer contains blood vessels and cushioning fat. Dermis is where new cells are made. Epidermis is outer protective covering. Sweat glands lubricate skin. Bones support body. Cross section of fragile skin showing layers of skin and bone. Arrows show surface pressure and body-weight pressure on skin. Subcutaneous layer has fewer and flatter fat cells. Dermis produces cells more slowly. Epidermis is dry and loses cell layers. Fewer sweat glands make less lubrication. Bones protrude.

Unrelieved pressure

People who can’t move for long periods of time are at risk for pressure ulcers/injuries. This is because oxygen and other nutrients can’t easily reach the skin, tissue, muscle, and bone cells in the area being compressed between the bone and the chair or bed. An immobile person who is fragile from age or disease is at greater risk of developing wounds. This pressure can come from prolonged pressure (while in bed, sitting down, or from a medical device) and/or in combination with shearing.


There is a force that can contribute to pressure ulcers/injuries. This force is called shearing and can occur from the force of the skin sliding against a surface. This sliding motion (shearing) compresses blood vessels and in combination with pressure can lead to the development of pressure ulcer/injuries.


Friction is a surface rubbing against the skin that can cause skin breakdown. Friction alone does not cause pressure ulcers/injuries.

Moisture buildup

Skin exposed to large amounts of fluid is fragile. Too much moisture (in some instances in combination with pressure and shear) can weaken or make skin brittle, change skin temperature, humidity, and airflow between the skin and support surface level (for example, a bed or chair).

Poor nutrition

Cells reproduce slowly if they are poorly nourished. They reproduce even more slowly in a person with an illness or tissue injury. Loss of body weight from poor nutrition makes tissue thin and fragile.

To learn more

For more information, go to the Pressure Ulcer/Injury Resource mobile app.

Author: StayWell Custom Communications
Last Annual Review Date: 8/1/2018
Copyright © The StayWell Company, LLC. except where otherwise noted.
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