What Causes Pressure Ulcers? 2017-01-27T04:26:57-08:00


A pressure ulcer is an area of injury to the skin and possibly the tissues beneath the skin as a result of pressure, or pressure along with shear and/or friction. The injury is usually situated over a bony prominence. Other names for a pressure ulcer are decubitus ulcer, pressure sore or bed sore.Pressure ulcers occur far too often in health care settings. A review of the prevalence over a ten year period in the U.S. was 10 to 18% in acute care, 2.3 to 28% for long term care, and 0 to 29% for home care. Previous studies found the overall prevalence rate in Canadian health care settings to be even higher (26%). The difference may be partly due to the way in which the studies were done. About half of the pressure ulcers in the studies were stage 1 (skin was not broken).

Caring for people with pressure ulcers is expensive. The cost to heal a severe pressure ulcer may be $40,000 or more. The annual cost of pressure ulcer care in the U.S. has been estimated at between $5 and $8.5 billion. The cost in terms of human suffering cannot be measured. Pressure ulcers have a negative impact on a client’s emotional, physical and social health. Financial costs to the sufferer and their family can be high. People lose independence and control. Pressure ulcers lead to longer hospital stays and increased mortality.


A pressure ulcer stems from pressure or pressure combined with friction or shear. Clients who are immobile (unable to move) are at increased risk because immobility leads to prolonged pressure. On average, a healthy individual changes position every 11.6 minutes. People who are unable to reposition themselves must rely upon caregivers to move them. When a person sits or lies in one position for a long time, the weight of the person’s body presses on bone. The bone presses on the tissue and skin that cover it. The tissue is trapped between the bone and the bed or chair. This squeezes blood vessels in the skin and tissues, causing a reduced blood supply. A lack of nutrients and oxygen result and the tissue then starts to decay.

Friction and shear can also contribute to the creation of a pressure ulcer. Friction occurs when the skin rubs against something like a bed sheet, cast, or brace. Friction usually causes an injury, such as an abrasion, that you can see. Bony areas are more likely to be involved, such as the tailbone or ankles. This is especially true for people who have poor nutrition, for people who must be repositioned by others, and for older adults because their skin is usually thin and delicate.

Shear occurs beneath the surface of the skin as the result of a parallel force. For example, raising the head of the bed above 30 degrees will cause the resident to slide down the bed. When that happens, the skin sticks to the bed but the pelvis goes in the opposite direction. The same effect will occur when a person slides down in a chair. Tissue damage can occur.
There are two theories about how a pressure ulcer forms.

One theory says that pressure ulcers form deep inside the tissue and move outwards. The second theory is that damage occurs from a skin injury on the surface that spreads to deep tissues. The most important thing to know is that, regardless of how they develop, pressure ulcers can be prevented. It is much easier to prevent pressure ulcers than it is to cure them.

We’ve discussed three forces – pressure, friction and shear – associated with pressure ulcers. Many other factors can also contribute to the development of pressure ulcers. These factors include:

Advanced age

The aging process causes changes to the skin. These changes make the skin less able to withstand normal wear and tear. The skin of older persons is more fragile. It is easily injured and it takes longer to heal.

Decreased skin sensation

When we sit in the same spot for a long time, the blood supply to that area is decreased. The decreased blood supply caused by pressure results in pain. Pain causes us to move, thus relieving the pressure. Clients with decreased sensation may not be able to feel the pain. They may stay in the same position much too long. A pressure ulcer may result.

Physical conditions

Certain conditions such as spinal cord injury, diabetes mellitus, stroke, and hypotension can cause pressure ulcers.
Decreased nutrition or poor fluid intake.

Moisture in the skin

Moist skin due to incontinence, excessive sweating, wound drainage or increased sweating from a high temperature
Products that irritate the skin.

Decreased mental status

Clients with decreased mental status may be unable to properly care for themselves.


The use of certain drugs such as steroids


Underweight or overweight. People who are either obese or very thin are at greater risk.

Of all the factors associated with the development of pressure ulcers, “pressure” is the most important. A small amount of pressure for a long period of time can do just as much damage as a great deal of pressure over a short period of time.

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