What is a Pressure Ulcer?

A pressure ulcer is an area of damage to the skin and the underlying tissue, usually over a bony area of the body. Pressure ulcers range in severity from skin discolouration to severe open wounds where the muscle and bone are visible.


What causes Pressure Ulcers?

Pressure ulcers develop as a response to external forces causing localised ischemia (a restriction in blood supply). It is generally believed that external forces from pressure, or pressure with a combination of shear cause stresses and strains on the tissue. These stresses and strains occlude circulation, reducing oxygen and other vital nutrients reaching the tissue. Lymphatic drainage is also thought to be impaired, causing a build of metabolic waste. Lets take a closer look four main factors that cause skin damage:


Pressure can be calculated by dividing weight by support surface area, hence the greater the support area, the lower the pressure. The pressure from a mattress when lying or sitting compresses skin and tissue between the surface of the mattress and the bony parts of the body. When skin and tissue is compacted between these two surfaces, capilliaries get compressed preventing them from carrying oxygen and other vital nutrients to the tissue.



Shear forces are parallel forces, sometimes described as stretching forces, caused by the effects of gravity. When an individual slides down or is dragged up a bed or chair, shear forces pull on the skin. When this occurs, the upper layers of skin can be pulled away from deeper layers of skin and tissue causing damage. This stretching force can rupture capilliaries, thus causing localised tissue damage.



Friction is a type of shear force that is limited to the skin but can damage the epidermis and result in a superficial ulcer. Friction is commonly defined as the resistance present when one material rubs against another e.g. the rubbing of a bed sheet against the skin. This commonly occurs when individuals slide down the bed or chair causing abrasions or blisters.



Increased body temperature is also thought to increase the risk of pressure ulcer development.


Who is at risk of developing pressure ulcers?

People may be at risk of developing pressure ulcers, often referred to as Bed Sores, for a number of reasons such as:

- Immobility - Obesity
- Malnourishment - Continence issues
- Poor circulation - Previous tissue damage

People with certain skin types and those with particular underlying medical conditions are also vulnerable. The presence of pressure ulcers has been associated with an increased risk of secondary infection and a two to four-fold increase in the risk of death in older people in intensive care units.4

Understanding the environment and your patient

Many clinicians now use a SKIN or CARE Bundle which is a useful tool in preventing pressure ulcers. This typically includes observation and action elements that are designed to monitor and prevent pressure ulcer formation


The SKIN Bundle

S - Support Surface

A high quality and properly maintained pressure reducing foam mattress is clinically proven to positively contribute to pressure ulcer prevention. If a patient sits out of bed, a pressure reducing cushion should also be used to assist in the prevention of damage to the buttocks.

K - Keep moving

Lying or sitting in one position for long periods of time can cause the skin to become damaged and eventually die due to lack of blood flow. Patients should be repositioned regularly and/or encouraged to re-position themselves.

I - Incontinence

Management of continence and keeping patients clean and dry is essential in preventing skin damage. Prolonged wetness to the skin (maceration) increases the risk of damage that can be caused by shearing. A skin inspection should include assessment of continence.

N - Nutrition and Hydration

The skin, as the largest organ in the body, must be kept will hydrated. Patients should be encouraged or assisted to drink two litres of fluid per day. Good nutrition provides essential nutrients which in turn keeps the skin healthy. An underweight bony patient will be at greater risk of developing pressure ulcers. Similarly an obese patient will be at greater risk, due to immobility, and increased pressure caused by body weight.

Pressure Ulcer Classification

There are a number of methods for classifying the severity of a pressure ulcer.

Invacare has developed a Pressure Ulcer Classification poster based on the EPUAP research, which is available for you to download. If you require hard copies, please complete the Contact form.

There are a selection of free educational resources available for you to download, just click here.

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