Identifying the Dangers of Shear

In the seating & positioning world, we generally understand pressure. Pressure to human soft tissue compresses the blood vessels, impeding blood supply to and from the cell. The result is cell death occurring by ischemia.

We deal with pressure by positioning end users to provide maximum pressure redistribution away from bony prominences, and teach frequent repositioning to help prevent this ischemia. But if it’s that simple, why the high incidence of pressure ulcers?

Are we addressing shear?

What if shear is contributing to this high incidence of pressure ulcers? It is often misunderstood, and at best, poorly understood. What if we’re missing the piece that could decrease the risk and promote healing of already compromised tissue?

What Is Shear?

Shear occurs with a combination of pressure (downward forces) and friction (tangential forces). Friction is the resistance of one surface moving across another. When combined with downward pressure, high friction causes distortion and deformation of the tissues -- shear strain, to be more exact. This distortion interferes with the cells’ biological functions, such as transporting nutrients from the outside in, and moving biological waste from inside of the cell to outside it. The disruption of those functions leads to cell death. And just like with pressure, cell death leads to pressure ulcers.

Who Is at Risk for Shear?

So among wheelchair users, who is at risk for shear? The simple answer is everyone.

Seating is not static. An active, independent wheelchair user is frequently weight shifting, reaching for items, transferring, and performing daily tasks involving shifting and movement. All of these activities involve downward pressure and static or dynamic friction -- and that equals shear.

Dependent users are frequently having their weight shifted and transfers performed. And as they tire, they slide into a posterior pelvic tilt in their chairs. This involves downward pressure and static or dynamic friction -- and that equals shear.

How Do We Reduce Shear?

There are several different ways that wheelchair users and their seating team can lower the risks of shear:

-- Wheelchair users should be aware of friction and try to prevent shear during transfers by fully lifting themselves over the surface or by using a low-friction interface to assist with transfers.

-- Wheelchair users can wear low-friction clothing to minimize the risk during weight shifts, reaching and transfers (e.g., jeans are high friction, while polyester is low friction).

-- Seating professionals can provide positioning equipment to minimize sliding into posterior pelvic tilt (combination of cushion, back, laterals).

-- The seating team can elect to use a low-friction interface, such as GlideWear technology, under the bony prominences.

What Is GlideWear & How Does It Work?

GlideWear is a dual-ply, “slippery,” breathable fabric. It provides a low coefficient of friction between the user and the seat, meaning it moves mostly with the user instead of against him/her, as a typical cover would. It is strategically placed under the bony prominences to decrease the risk of tissue distortion and cell death by shear.

The areas surrounding the GlideWear section are stability zones to prevent the user from sliding forward in the chair. GlideWear works during a user’s daily tasks, such as weight shifting, transfers and reaching… or just when the user tires out. You can protect the end user from the risk of shear strain simply by choosing GlideWear as a wheelchair cushion cover option on Comfort Company cushions.

For active wheelchair users and those who spend long periods of time in their wheelchairs every day, shear is a risk that is always present. The good news is that it can be combatted in a number of ways, from adopting safer transfer methods to choosing appropriate positioning components and seating options such as GlideWear.

Of course, the first step is understanding what shear is, when it’s most likely to occur, and why it threatens the mobility and independence of wheelchair users.

Then the entire seating team can brainstorm the best ways to fight back.

About the Author

Stacey Mullis, OTR/L, ATP, is director of clinical education for Comfort Company.

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