Pressure ulcer prevention

Learn more about the aietiology of pressure ulcers

• Intrinsic and extrinsic factors must be considered
• Structured risk assessment should be undertaken – reassessment must not be forgotten
• Accurate documentation of each assessment is critical
• Prevention plan should be implemented based on risk assessment

Intrinsic Risk Factors include an assessment of the following

Extrinsic Risk Factors

Four extrinsic factors^{1, 24} are most commonly reported to pose a risk of tissue damage:

1. Pressure^{1, 24}
2. Shear^{1, 24, 25, 26}
3. Skin microclimate^{1, 27} – heat and humidity
4. Friction¹ – this force has historically been included in this list but is now discussed separately and the wounds described as friction wounds

It is often the combination of forces that create the highest risk for a vulnerable patient. Tissue deformation happens in soft tissue, adipose tissue, connective tissue and muscle when these forces occur causing stresses and strain affecting the perfusion and cellular mechanisms essential for normal functioning. In the clinical setting non uniform forces are usually witnessed and shear forces are often present. Age, lifestyle, chronic illnesses can affect the ability to respond to these forces.

Pressure

 Definition- a load applied at right angles to the tissue interface.

Fast facts

• Affected by stiffness of surface, load, tissue composition, geometry
• Usually expressed in lb/in2 (psi) or mmHg
• Bony prominences can be exposed to higher stresses/strains and therefore may be reflected in deep tissue injury
• Combination of pressure with other forces may exacerbate issues
• Pressure wounds tend to be uniform or circular in shape and tend to present with a neat appearance
• Influence of time – high loads experienced for short periods of time can be as damaging as smaller loads experienced for long periods of time

Shear

 Definition - “an action or stress resulting from applied forces which causes or tends to cause two contiguous internal parts of the body to deform in the transverse plane”.

Fast Facts

• Increases when lateral movement occurs and also occurs when laying flat
• When pressure load is constant and the shear forces increase the amount of tissue deformation may increase
• Increased shear forces can exacerbate tissue damage
• Shear inflicted ulcers often present with a less deep area swooping down to a deeper area with bruising a typical feature- skin edges may be ragged
• Shear forces tend to cause deeper tissue damage which may not be immediately visible
• Changes in position are likely to cause shear – for example when the head of bed is raised or lowered

Microclimate

 Definition - the local tissue temperature and moisture at the body/support surface interface.

Fast Facts

• Moisture is known to impact on ability of the skin to function
• Reduce stiffness - softens skin, maceration
• Reduce strength - up 96%, lead to erosion
• Increase co-efficient of friction
• Increase adhesion to contact surface – increase risk of shear
• Promote abrasion, slough and ulceration
• Dilute skin acidity - pH shift to alkalinity
• Elevated temperature increases metabolic rate
• Elevated temperature leads to increased sweating
• At interface point with support surface, body heat becomes trapped causing the skin to rapidly warm - heat accumulates and moisture builds up
• Animal studies have demonstrated a link between heat build up and ulcer formation¹⁴

Friction

 Definition - “the contact force parallel to the skin surface in case of sliding – i.e. sliding of the surfaces along each other”.

Fast Facts

• Friction results in the disturbance of the skin – the ability of the skin to act as a barrier may be impaired posing a higher risk of infection or the underlying structures may be exposed
• Friction often presents as a shallow, denuded and painful area
• The most common areas for this type of wound are the buttocks, sacrum, back, elbows and heels
• Friction wounds may be characterized by being very untidy wounds with ragged edges
• Friction has historically been included in the list of 4 key extrinsic factors but is now discussed separately and the wounds described as friction wounds

References

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