Friction vs. Shearing in Wound Care: What’s the Difference?

Friction vs. Shearing: What's the Difference?

 

It’s a common question among wound care providers: what exactly is the difference between friction and shearing? These two conditions are common with limited mobility patients, and often contribute to the development of pressure ulcers. Knowing the answer to this question will help you provide better treatment for your patients. Plus, you’ll be able to amaze your friends at dinner parties! So in the interest of your patients and social life, we’ve got some answers.

What is friction?

Friction is when two forces rub together.  The result will be a superficial, partial thickness skin injury that will look like an abrasion.  For instance, a patient in bed might be agitated or restless, and as a result, continuously rub his feet across the sheets. No pressure is involved, his feet are simply sliding against the surface. This constant friction can cause the damage to the epidermis (and upper dermal skin layers) known as “sheet burn.”  The damage will be superficial in depth and irregular in shape. But this type of damage is not caused from pressure and therefore won’t be staged.

Friction can be avoided in this example by having the patient assist as much as possible when moving in bed, or using two caregivers and a lift sheet to avoid dragging across the bed.

What is shearing?

Shearing, on the other hand, is friction plus the force of gravity.  Let’s think of that same patient in bed, with his head in a raised position.

Example of a Stage 3 pressure injury, which can result from friction and shearing.

Example of a Stage 3 pressure injury, which can result from friction and shearing.

As the weight of gravity pulls down on the skeleton towards the foot of the bed, his skin might be stuck against the mattress due to friction. As his bones slide down, vessels in between the skin and the bone can become compressed, stretched and/or torn.  This causes a lack of blood flow to the tissue leading to ischemia. This is how we end up with a full thickness wound.

If pressure is present (and it almost always is with shearing), then it’s staged as a full thickness pressure injury. This is either a Stage 3 or 4, depending on the depth of tissue destruction, based on NPUAP definitions.  Have you seen a Stage 3 or Stage 4 pressure injury with an oblong or teardrop in shape,  irregular or jagged edges, and undermining or tunneling? This is a significant clue that shearing forces were present.

The Bottom Line

Remember this: it is not possible to have shear without friction, but it is possible to have friction without shear. Because shear is a result of a combination of friction and gravity, it can be avoided by keeping the head of the patient bed at a lower angle.

Wound Care Education Institute® provides online and onsite courses in the fields of Skin, Wound, Diabetic and Ostomy Management. Health care professionals who meet the eligibility requirements may sit for the prestigious WCC®, DWC® and OMS national board certification examinations through the National Alliance of Wound Care and Ostomy® (NAWCO®). For more information see wcei.net.

 

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