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What causes pressure injuries?

A pressure injury is caused by a lack of blood flow due to mechanical stress and the skin and tissues over a bony area.  Please read that again: it is caused by a loss of blood flow.  The pressure on the skin and subcutaneous tissues presses on the small blood vessels such that blood flow stops up - the tissues get oxygen-deprived, and cells die by the millions. 


Most areas of skin manage with little oxygen for about 2-3 hours; after that, the cells start to die.  So if the pressure lasts for longer than two hours, we can see pressure injuries developing.  That is why we should turn an immobile patient every two hours! 

In addition, when slowly sliding down a bed or chair, friction to the outer skin layer - such as from wrinkled bedding or clothing - contributes to skin injury and ulceration. Excessive exposure to moisture, such as sweat, blood, urine or faeces, also increases the likelihood of developing a pressure ulcer. 


Immobile patients are obviously at most risk of developing a pressure injury. If the patient is wheelchair-bound or bedridden and cannot change position without assistance, they are at high risk of developing a pressure ulcer. Incontinence and poor nutritional status are other risk factors. Peripheral neuropathy ( for example, from diabetes) is a high risk for developing pressure ulcers on the heel and the rest of the foot.  Alcoholism and drug abuse can lead an otherwise healthy patient to develop serious pressure ulcers because they have been lying immobilised for many hours in an intoxicated condition. Surgical procedures that take many hours can cause serious pressure injuries, and surgical staff must be trained to prevent this.  Anything hard that we place on the patient, like a plaster of paris, other casts or orthotics, can cause pressure injuries. Medical, technical devices like nose catheters, oxygen tubes, oxygen masks and equipment used for monitoring the patient can all cause localised pressure injuries, especially in sedated patients or on assisted ventilation in ICUs. 

Incontinence associated dermatitis (IAD) is confused by many caregivers with a pressure injury.  Whilst they may appear similar in appearance, the crucial difference is that the one is caused by pressure- the other by excessive moisture/ irritating substances in urine/faeces.   Pressure ulcers need offloading, and IAD needs skin protection from urine/faeces.  However, IAD poses a significant danger to developing a pressure ulcer also. The damaged skin in IAD is not as tolerant to pressure as healthy skin, and these patients need offloading as well.  So in many ways, these two conditions are treated very similarly - but in IAD, we also have a particular focus on keeping urine/faeces away from the skin.  We have written a separate chapter on IAD - please refer to that for more details. 

Figure 1 Irritated skin caused by incontinence (IAD).  This form of moisture-associated skin damage increases the danger of pressure injury, and off-loading is therefore essential in addition to keeping urine/feces away from the skin. What are signs that the above skin changes are not  (just a pressure injury"? If you look closely, you will see the redness going well into the gluteal cleft - this is not usually an area most prone to pressure injury.  Also, the appearance of the reddish areas reminds more of a diaper rash than a pressure injury. In addition, we know that the above patient is incontinent for both urine and feces, which furthermore supports our theory that this is IAD.

Sadly many times, pressure injuries arise due to a lack of knowledge on the side of the caregivers:

  • Lack of vigilance

  • Lack of training/knowledge

  • Not identifying who is at high risk to develop a pressure injury

  • Failure to communicate with colleagues (i.e., nurses not communicating between shifts)

  • Lack of equipment (i.e., not having pressure reducing mattresses available)

  • Improper use of equipment (i.e., thinking that a pressure-reducing mattress is enough and that the patient doesn`t need turning anymore.

  • Delays in starting with off-loading measures

  • Lack of engagement from leaders, other medical professions, health authorities, and politicians

As mentioned above, patients who are immobilized during surgery ( general anesthesia, spinal anesthesia, or peripheral blocks) or sedated on a respirator are at high risk of developing pressure injuries. Staff working in these environments need special training for pressure injury prevention.  If the surgery lasts for more than 3 hours ( healthy individuals) and 2 hours (high-risk patients), you will have to make some changes to the positioning of the patient. Remember to cushion the heels and elbows well in these patients.  Also, some patients decide to cross their legs just before receiving narcosis.  This may not always be observed by staff and cause a severe pressure injury to the back of the leg, which is lying on top of the other.

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