The right wheelchair cushion can do far more than provide a comfortable place to sit. It can increase sitting tolerance to enable a client to be mobile for longer periods. It can help to prevent pressure sores by distributing weight more evenly. Some cushions can improve a client’s stability while sitting, thereby improving, for instance, that client’s ability to safely reach out from his wheelchair. Cushions therefore are an integral part of an effective seating system.

Today’s cushions are made from a range of materials — and some are hybrids, composed of multiple media. What are the differences among the various cushion media? And how can providers use this information to choose the cushion most appropriate for each client’s needs?

Know Your Cushion Media

In a paper called Wheelchair Cushion Differences and citing Paralyzed Veterans of America and the Rehabilitation Engineering & Assistive Technology Society of North America (RESNA), Stephen Sprigle, Ph.D., PT, identified an array of media historically used to create wheelchair cushions:

• Foam — Of varying thicknesses, stiffnesses and densities.
• Viscoelastic foam — Also called memory foam; when pressed, it temporarily “remembers” or maintains an impression before gradually returning to its original shape.
• Non-deforming foam — “Does not compress, defl ect or deform under sitting forces,” which Sprigle says has made it a popular choice for cushion bases.
• Bonded foam — Different types of foams glued together.
• Viscous fluid — “A relatively incompressible substance with viscous properties… (that does not) flow as readily as water.”
  Examples: maple syrup, grease.
• Air — Used within airtight cells or pockets of the cushion.
• Water — An alternative to air, also contained within airtight cushion cells or pockets. Once common, water has since been replaced by viscous fluid as a cushion medium.
• Gel — “Solid, rubber-like, relatively incompressible material.”

In a presentation called Principles of Pressure Management, in conjunction with the Rehabilitation Engineering & Research Center on Wheeled Mobility (RERCWM), Douglas A. Hobson, Ph.D., identified several more cushion media:

• Custom-contoured foam
• Plastic honeycomb
• Combinations of the media mentioned above

Cushion Media Pros & Cons

So many cushion media are used, of course, because different media have different properties — and because complex rehab clients have highly individualized needs. Among the benefits and potential drawbacks of commonly used media:

• Foam — On the plus side, it’s lightweight, especially important for self-propelling clients. Foam (not the non-deforming type) also compresses to provide good immersion when the user sits. That envelopment enables pressure to be distributed over a larger area and can help to avoid dangerous pressure buildup at bony areas. But foam does degrade and can be damaged by light and moisture. And traditional foam cushions retain heat, though Sprigle notes that viscoelastic cushions have “good thermal characteristics.”
• Viscous fluid — Sprigle notes this medium provides “variable envelopment depending on container,” but has “good thermal properties” and low shear risk. Fluid is displaced when the user sits, meaning it may flow away from areas in critical need of protection, such as bony prominences. The fluid cannot flow back to its original position independently, so users or caregivers need to remember to manually move the fluid back into place by kneading the cushion before every use.
• Air — Both shear risk and envelopment depend on the proper infl ation and design of the cushion, Sprigle says. In a 2008 paper called “Wheelchair Cushion Selection — Making the Right Choice,” Kathy Fisher, BScOT, ATP, OT/R, wrote, “Air provides the perfect medium for immersion. The limitation is containing the air for stability.” She adds that air cushions reduce heat and moisture buildup. Air cushions need to be regularly checked to ensure infl ation levels are still appropriate and allow proper immersion when the user sits.
• Gel — Solid/polymer gels “provide shear reduction as the material moves with the skin, but due to the density does not allow for much immersion,” Fisher says. “Fluid gels promote immersion and shear reduction, as they allow bony prominences to move within the fluid. Constant movements within the fluid may cause the fluid to redistribute, allowing for ‘bottoming out’ and increased risk of pressure points.” Both polymer and fluid gels are relatively heavy compared to other cushion media.
• Honeycomb — Flexible-fusion bonded honeycomb has memory and can return to its original shape. It’s lightweight, remains flexible in high and low temperatures, and is easily cleaned. In the end, all these cushion media work well for certain clients with certain clinical, environmental and lifestyle needs, so it’s up to the complex rehab team to take those factors into consideration when making a decision.

As Fisher said in her paper, “Which cushion is best can only be determined by identifying and prioritizing clients’ postural and skin-management needs.”