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What causes a Pressure Ulcer / Bed Sore?


What Causes a Pressure Ulcer?


Pressure ulcers occur when sustained pressure is placed on a particular part of the body interrupting its blood supply.

Blood contains oxygen, and nutrients are needed to help keep tissue healthy. Without a constant blood supply,  damage to tissue occurs which results in it eventually dieing.

This lack of blood supply means that the skin no longer receives infection-fighting white blood cells and once an ulcer has developed, it can sometimes become infected by bacteria.

People with normal mobility will not develop pressure ulcers because they automatically makes hundreds of regular movements which prevent any pressure building on parts of their body:  An example is while you sleep you may think you are lying still, but in general we shift positions many times each night.

The risk factors for pressure ulcers can be divided into one of the following two categories:

  • intrinsic risk factors– you have an underlying health condition, or some other factor that will make you more vulnerable to developing ulcers
  • extrinsic risk factors– factors in your immediate environment that put you at risk of developing these pressure ulcers

In some cases, a person may have both of the above risk factors.

Intrinsic risk factors

Intrinsic risk factors include:

  • Mobility problems – anything that affects you moving some or all of your body
  • Poor nutrition – healthy skin requires nutrients that can only be supplied by eating a nutritious diet
  • An underlying health condition – which can disrupt your blood supply, or makes your skin more susceptible to injury and damage
  • Being over 70 years old
  • Urinary incontinence and/or bowel incontinence
  • Serious mental health conditions


Mobility problems

Could be due to or include:

  • Having a spinal cord injury that causes some paralysis to some or all of your limbs
  • Brain damage after a stroke, or severe head injury, which results in paralysis 
  • Having a condition like Alzheimer’s, Multiple Sclerosis and Parkinsons Disease which causes progressive damage to the nerves your body uses to move 
  • Having a fractured or broken bone
  • Severe pain causing difficulty when moving some or all of your body
  • Being in a Coma
  • Recovering from surgery
  • Condition such as Rheumatoid Arthritis, causing difficulty when moving your joints and bones


Poor nutrition

Reasons your diet may lack nutrition include:

  • Anorexia Nervosa – a mental health condition causing a person to have an unhealthy obsession with maintaining a low body weight  
  • Dysphagia – swallowing food is difficult
  • Dehydration – not enough fluids in your body


Health conditions

Conditions which make you more susceptible to pressure ulcers:

  • Type 1 & 2 Diabetes – high levels of blood sugar associated with diabites can disrupt normal blood flow
  • Peripheral arterial disease – restriction in the blood supply to the legs due to build-up of fatty substances in the arteries
  • Heart failure – previous damage to the heart making it harder for it to pump enough blood around the body
  • Kidney failure – the lose of most or all of its functions;  can lead upto to a build-up of dangerous toxins (poisons) in the blood, which can cause tissue damage
  • Chronic obstructive pulmonary disease (COPD) – a collection of lung diseases; where the low levels of oxygen in the blood associated with COPD can make the skin more vulnerable to damage


Ageing skin

There are several reasons why ageing skin is more vulnerable to pressure ulcers, including:

  • The loss of skin elasticity  which comes with age, which makes it more vulnerable to damage
  • Reduced flow of blood to the skin due to the effects of ageing
  • The lack of fat under the skin tends to decrease as people get older



Urinary incontinence (inability to control your bladder) and bowel incontinence (inability to control your bowels) can cause pressure ulcers to form due to certain areas of the skin  becoming moist and vulnerable to infection.


Mental health conditions

People with severe mental health conditions such as schizophrenia (a condition where people have problems telling the difference between reality and imagination) or severe depression have an increased risk of pressure ulcers for a number of reasons:

  • Poor diets
  • There are often other physical health conditions, such as diabetes or incontinence
  • Neglecting their personal hygiene, where their skin more vulnerable to injury and infection


Extrinsic risk factors

Extrinsic risk factors for pressure ulcers include:

  • Pressures from hard surfaces, such as wheelchais and beds
  • Pressure placed on the skin through involuntary muscle movements, like a muscle spasm
  • Moisture, this can break down the outer layer of the skin (epidermis)


The time it takes for a pressure ulcer to form will depend on:

  • The amount of pressure
  • How vulnerable a person’s skin is to damage


Grade three or four pressure ulcers can develop over short periods of time. For example, in susceptible people, a full-thickness pressure ulcer can sometimes develop in just a couple of hours. In some cases however, the damage will only become apparent a few days after the injury has occurred.