Harvest Healthcare

Equipped to care

Harvest Healthcare

Clinical Information

Shear and Friction in Pressure Ulcer Development

While the major factor in the development of pressure injury is pressure itself, shear forces also play a part.

What causes shear and friction?

When you move over a surface and the body remains in contact with it, the skin can be pulled along that surface. You can feel this ‘drag’ effect if you run your hand over something.

This ‘drag’ is caused by friction and leads to a difference in the direction of movement of the skin and the deeper tissues. This difference is called “shear” and is an important factor in pressure ulcer development.

How can shear forces lead to the development of a pressure ulcer?

Shear causes stretching and tearing of blood vessels which reduce blood flow increase blood pooling and can lead to cell damage.

Shearing stops or reduces blood flow more easily than pressure alone (for example, it is easier to cut off flow in a water hose by bending than by pinching it).

Although shear causes tissue damage slightly differently to pressure, the damage produced is the same as with pressure.

Importantly, it is difficult to create pressure without shear, and shear without pressure, so the two usually go hand-in-hand.

For information on how pressure leads to pressure injury, see our article How Pressure Ulcers Develop?

How can repeated friction cause a pressure ulcer?

As well as being a key element of making shear force, friction between the skin and the stationary surfaces such as bedclothes can result in the loss of the top layer of the skin (the stratum corneum).

Think about repeatedly rubbing your skin against a surface – after a time, the skin would start to become red and sore. This is due to friction.

This inflammation can lead to deeper injury or could be the initial damage needed to start pressure ulcer formation.

When there is a loss of the top skin layer, there is also a breach in the barrier against infection.

How can friction and shear be reduced?

There are several strategies to reduce shear and friction forces:

  • Use low-friction clothing such as Parafricta undergarments and socks to reduce friction on the vulnerable heel and pelvic areas. These can be especially useful for people who push themselves back up the bed using their heels, or who have involuntary leg movement, for example, those with Parkinson’s.
  • Use positioning aids such as slides sheets under the person’s body and feet and heels when repositioning to reduce the risk of friction and shear.
  • Use a profiling bed with an in-built knee break. When the person has been repositioned in bed, elevate the knee break first to prevent the person from sliding down the bed.

 

For more information about Harvest Healthcare please click here

For more news please visit our Twitter

Or follow us on LinkedIn

 

Risk Factors for Pressure Ulcer Development

Who is at Risk of Developing Pressure Ulcers?

The risk of developing a pressure ulcer is affected by many health and environment-associated factors.

In fact, more than 100 risk factors for pressure ulcers have been identified.

This means that anyone can get a pressure ulcer, although the following factors can make them more likely to develop:

  • Being elderly – older people are more likely to have mobility problems and may also have thin skin that is more easily damaged.
  • Being confined to bed or a chair with an acute illness, for example a urine infection, diarrhoea and vomiting, or after recent surgery.
  • Full or partial paralysis, reducing the ability to move independently.
  • Incontinence leading to wet and irritated skin.
  • Poor nutrition, which may be due to a lack of adequate nutrients or insufficient calories.
  • Medical conditions such as kidney disease or heart failure, or those that affect the blood supply, such as diabetes or peripheral arterial disease, or conditions that affect the ability to move independently, such as a stroke (CVA), multiple sclerosis (MS) or Parkinson’s disease.
  • History of previous pressure damage, where scar tissue may be present, as this will be less resilient than normal skin.

 

For more information about Harvest Healthcare please click here

For more news please visit our Twitter

Or follow us on LinkedIn

Preventing Pressure Ulcer Development

Pressure ulcers can develop rapidly given the right conditions.

Not all risk factors can be controlled. However, the key risk factors affecting the individual should be taken into account as part of a pressure ulcer prevention strategy.
Preventive measures should include:

  • Risk assessment to identify key risk factors that put the individual at higher risk of pressure ulcer development

Risk assessment may involve the use of a scoring system eg. Waterlow, Braden, or Glamorgan scales or a system for colour (RAG) rating risk eg. Purpose T.

Whichever system is in use, it is important to ensure that it is not used in isolation but supports clinical & holistic assessment of the person and their needs and preferences.

  • Frequently assessing skin for early signs of damage

People who are able to do so should be shown how to check their skin for any signs of damage

Carers can also be shown how to inspect the skin and what to look for

Early signs of skin damage may include discomfort, redness, or a change in colour to the skin. This may be more difficult to assess in dark skin tones

  • Use of equipment that reduces pressure

Inflate and deflate to redistribute pressure
Static Viscoelastic (memory-foam) mattresses/cushions which conform to the shape of the body to distribute pressure evenly.
Positioning devices – these may include slide sheets for repositioning, and devices suitable for heels, etc. to remove all pressure from the heel and facilitate healing

  • Keep the person moving as much as possible. Regular movement helps redistribute pressure

For those at risk of pressure damage, changes in position should be made at least every 4 hours

For those at high risk of pressure damage changes in position should be made at least every 6 hours

Even small changes in position are really important to reduce the risk of damage

This should be discussed with each person on an individual basis, and agreement on the frequency of repositioning should be recorded

Repositioning frequency may need to be increased if skin assessment shows any increased vulnerability

People who cannot reposition themselves need assistance to do so.

This repositioning should be done throughout the day and night.

  • Use barrier creams and appropriate containment products (eg. Continence pads) for those with bladder or bowel issues that lead to frequent episodes of wet or soiled skin

Barrier creams should be dimethicone based products rather than oil-based products

A thorough continence assessment should be undertaken to establish the most appropriate containment products for the person.

  • Ensure access to a healthy diet and adequate fluid intake to keep the skin nourished and hydrated

 

For more information about Harvest Healthcare please click here

For more news please visit our Twitter

Or follow us on LinkedIn

 

Common Sites for Pressure Ulcer Development

Pressure ulcers are damage caused by pressure and / or shear.

What are the common sites for pressure ulceration?

The areas that are particularly prone to pressure sores are those that cover the bony areas such as:

 

  • Heels
  • Ankles
  • Buttocks
  • Shoulders
  • Spine
  • Backs or sides of the knees
  • Toes and feet
  • Back of the head (occiput)

 

 

 

 

 

When describing where the tissue damage has occurred on the buttocks, clinical staff should ensure that the correct terminology is used to accurately describe the location – the following diagram may help.

  • Sacrum (see below)
  • Coccyx (Tailbone)
  • Trochanter (Hipbones)
  • Gluteal (buttock)
  • Ischial (often incorrectly described as lower buttock or upper thigh, but usually caused by unrelieved pressure from sitting)
  • Gluteal cleft (often see moisture damage rather than pressure damage in this area)
  • Perianal / perineal area (often due to moisture eg. From urine or faeces – rather than pressure)

                       

Effective preventive measures reduce the risk of pressure ulcers developing.

Preventive measures should include:

  • Frequently assessing skin for early signs of damage
  • Use a high-quality static pressure-reducing mattress and cushion. Or, for those who require a higher level of protection use an alternating pressure air mattress and cushion
  • Keep the person moving as much as possible. Even small changes in position are really important to reduce risk of damage
  • Use barrier creams and appropriate containment products (eg. Continence pads) for those with bladder or bowel issues that lead to frequent episodes of wet or soiled skin
  • Ensure access to a healthy diet and adequate fluid intake to keep the skin nourished and hydrated

 

*’Surface Anatomy of Buttocks’ image is taken from the ‘Visual Guide for Accurately Designating the Anatomic Location of Buttocks Lesions’ article.
J Wound Ostomy Continence Nurs. 2016;43(2):148-149. Published by Lippincott Williams & Wilkins

For more information about Harvest Healthcare please click here

For more news please visit our Twitter

Or follow us on LinkedIn

How Pressure Ulcers Develop

What are pressure ulcers?

Pressure ulcers – also referred to as pressure damage, pressure injuries, bedsores or decubitus ulcers – are usually seen on the skin as red, purple or discoloured areas, which may progress into blistering or open wounds. These can develop on bony areas of the body such as the back, bottom or heels or in areas where the blood supply to the tissues has been reduced due to prolonged pressure.

They can happen to anyone, but usually affect people who spend more time in bed or those who sit in a chair or wheelchair for long periods of time. If you are at risk of pressure damage you should be offered advice on how to reduce your risk and this will usually include information on:

  • How to assess your skin for early signs of damage
  • What type of mattresses, cushions or special devices may help to relieve pressure from vulnerable areas
  • How to keep moving. Even small changes in position are really important to reduce the risk of damage
  • If you have problems with your bladder or bowels that mean that your skin is wet or soiled, there may be creams and products that will help to prevent skin damage
  • How to make sure that you eat a healthy diet and take sufficient fluid to keep the skin nourished and hydrated.

While pressure ulcers can appear anywhere on the body, they are most commonly seen over bony areas such as the heels, ankles, hips, spine and buttocks.

Why do pressure ulcers develop?

Pressure ulcers form when blood flow to the tissues of the skin and surrounding area is reduced.

Capillaries are the smallest blood vessels. They bring oxygenated blood from the arteries into the organs, skin and underlying tissue, as well as taking deoxygenated blood away from the skin and tissues back into the veins.

When a person is sitting or lying on a surface the pressure between the seat/mattress and the body compresses the capillaries in this area. This is especially noticeable over bony areas, like your heels, buttocks and tailbone (coccyx). Just like squeezing a hosepipe if this pressure is high enough it can reduce blood flow through these capillaries or even stop it altogether.

Pressure is not the only issue. Shear forces (such as sliding down the bed or slouching in a chair) also play a part in the development of pressure.

For more information on these forces, see our article Shear and Friction in Pressure Ulcer Development.

How do we naturally prevent pressure ulcers?

If someone’s blood vessels are closed or compressed due to pressure, then the oxygen supply to the surrounding tissues falls.
Interestingly, in healthy people, this fall in oxygen prompts a reflex to move; this is the reason you cross and uncross your legs or roll over in bed at night without really thinking about it! Ignore this reflex and you will start to feel pain and discomfort, a sign from your body that it’s time to get moving again.

If the pressure is relieved, and the circulation is restored, the capillaries open up again and blood flow increases to the area again. For those with pale skin, this may be observed as the pink patch that is visible if you have had your legs crossed for a sustained period. This pink patch is called ‘blanching erythema’. Blanching erythema is identifiable by the pale spot you can see when you press on it with a finger on Caucasian skin. In dark skin tones, this may not be visible, therefore when checking the skin, any change in skin colour or appearance should be checked carefully in case it is a sign of increased vulnerability.

To see strategies to support pressure ulcer prevention click here.

What happens if the skin remains under pressure?

If pressure continues, then reduced oxygen levels starts to cause damage to the capillaries and surrounding cells.
The first sign in the skin is often a change in colour. For those with light skin tones, non-blanching erythema may be visible, where the skin colour is a persistent red and the skin colour does not change when lightly pressed with a finger.

For those with dark skin tones, a change in skin colour may be observed, but is unlikely to present as redness. It is therefore important to compare any changes in colour observed with areas of unaffected skin to determine if early signs of pressure damage are developing.

It is also important to understand that damage may occur deep within the tissues, presenting as a Deep Tissue Injury. This may present as a purple or dark discoloured area, a thin blistered area over an area of dark discolouration or an area of thin dark eschar. The affected area may be painful and may be harder or softer, or warmer or sometimes cooler than the surrounding areas.

 

For more information about Harvest Healthcare please click here

For more news please visit our Twitter

Or follow us on LinkedIn