ATP Series

Showing Their Age

Why Wheelchair Seat Cushions Wear Out — And a Standards Update

• By Laurie Watanabe
• May 01, 2017

As a critical interface between wheelchair and user, complex rehab seat cushions have a huge impact on positioning and overall mobility efficiency.

They’re expected to be breathable. Many provide positioning via contouring. They might use multiple types of media — for example, gel bladders in addition to layers of foam — to be mindful of weight distribution in critical areas. For ultralightweight wheelchair users, cushions need to be lightweight so they don’t make self propelling more difficult.

And naturally, cushions are expected to be “comfortable” and “durable,” definitions that vary from user to user.

WHEN LIFE HAPPENS

Like any often-used equipment, seat cushions do wear down — and ironically, when ATPs and clinicians do a great job of building a seating and wheeled mobility system, its cushion may age more quickly because it’s being used extensively. The goal the seating team aims for — a fully functional consumer — can be the exact thing that wears down a cushion.

Jeff Rogers, senior product manager of pediatrics and seating for Sunrise Medical, confirmed that much of what causes cushions to age can be linked to everyday wheelchair use.

“There are multiple factors that can help accelerate cushion aging,” he said. “Dirt, food, liquids and a multitude of other things come in contact with the cushion on a daily basis.”

Kara Kopplin, senior research manager/research and innovation for Permobil, said, “Wheelchair cushions play such an important role in protecting the health, function and well-being of the user, and they have to survive environments and use that can be very damaging over time. Just daily sitting and transferring provides a mechanical stress to the cushion, and adding in moisture from sweat and incontinence, as well as exposure to body temperatures or higher (especially if left in a car!) can all potentially shorten the useful life of the cushion.”

Susan Cwiertnia, PT, MS, director of medical for VARILITE, noted, “There are many everyday factors that impact how a wheelchair cushion ages. A major factor is how much time the user spends in their wheelchair during the day and their activity level. Some users can spend as much as 16 hours a day in the wheelchair!

“The activity levels vary from sitting in an office most of the day to higher activity levels with frequent transfers throughout the day and transporting in a vehicle. Whether the cushion is used primarily in an indoor or outdoor environment impacts aging: When outdoors, the cushion is exposed to more extremes of temperature, sunlight and humidity. Bowel and bladder incontinence can accelerate aging by causing exposure to moisture and soiling, requiring more frequent laundering of the cover.”

That brings up another irony: Cleaning and not cleaning a cushion can cause it to age.

“Add in laundering, and even disinfecting [the cushion] if the person is living in a facility, and you’ll find the cushion can really be exposed to a wide variety of potentially abusive conditions,” Kopplin said. “When a cushion is not washed, or cannot be washed, biological agents accumulate that can attack the cushion materials. So this can lead to accelerated degradation…not to mention an unsanitary condition for the user. There can even be the problem of wear and tear from foreign objects that aren’t washed away, like sand from a visit to the beach, which can grind and scrape against the cushion or cover.”

WHEN WEAR HAPPENS

As the cushion’s initial line of protection from such menaces as spilled food and drink, as well as incontinence, cushion covers also age.

“The cover can show wear and tear from these exposures as well,” Kopplin said. “Depending on the design and construction of the cushion, though, these failures may be more cosmetic in nature, with potentially less or no impact on the overall benefits of the cushion. However, in other cases one of the important functions of the cover is to protect a cushion that cannot be washed or disinfected, so the degree of effect of a cover failure can vary.”

“Cushion covers are designed not only to work with the functional design of the cushion, but to protect the cushion inside,” Cwiertnia said. “The covers will wear faster than the cushion and should be replaced to extend the lifetime of the cushion. Some users will have a second cover and alternate them during wash cycles. If the cushion is in use in a facility instead of a home, it may also have accelerated aging due to disinfection techniques used on equipment in facilities.”

What wear looks like depends on the media that make up the cushion: “Symptoms of aging can vary depending on the cushion materials,” Cwiertnia said.

As an example, Rogers said, “As foams and other materials are exposed to the elements, they can accelerate the wear. Foam that is starting to deteriorate or break down is one common side of excessive wear. Fabrics that are starting to become thin and see through is another.”

“Open-cell foam cushions can develop a compression set, where the spring-like nature of the cells don’t spring back to full height,” Cwiertnia said. “Open-cell foam can be moldy due to moisture and can have stains. Both open- and closed-cell foam cushions can crumble with aging and exposure to ultraviolet light. Neoprene cushion materials can also show signs of cracking, or the cells might stick together, indicating reduction in neoprene integrity.

“Most cushions use a passive system for microclimate control that includes spacer knit material or reticulated foam as part of the cover materials for air to circulate, so inspecting the cover is important. Viscous gel cushions might show signs of fluid leakage or fluid hardening over time. Also check for the number and location of puncture patches on cushions, because too many patches on the surface will decrease how the cushion functions.”

TESTING & STANDARDS FOR CUSHION WEAR

Theoretically, subjecting seat cushions to standards regarding wear could help clinicians to better understand the anticipated performance of the cushions they choose.

But developing cushion wear tests and agreeing on how durable a cushion has to be — as well as how test results will be interpreted and used — are not easy tasks.

Cwiertnia pointed out “the big discrepancy between how often CMS [Centers for Medicare & Medicaid Services] will pay to replace worn-out equipment. On the PDAC [Pricing, Data Analysis & Coding contractor] application to get a cushion HCPCS code for CMS, the requirement is that the cushion pass 18 months of life-cycle testing. Yet in the wheelchair seating LCD [Local Coverage Determination], they will only replace DME/cushions once every five years.”

So would it make sense for manufacturers to create more durable cushions that could last five years?

“The tricky part,” Cwiertnia said, “is CMS mandates to make the cushions have to pass longer life-cycle testing [would require] materials to be much more durable — think thicker, stiffer, stronger — which might take away from the function of a skin protection cushion. At the same time it could interfere with innovation and design to make products that perform at high levels.”

Kopplin agreed that developing standards for aging is complex. “The development of a standard to simulate cushion use is a very challenging process. The overarching goal is to design lab tests that can adequately predict whether the brand-new cushion the user receives ‘out of the box’ will still behave and perform the same way in the future over months and years. This is especially critical now, as cushions are typically only replaced every five years under the Medicare reimbursement system.”

Of current work being done on this front, Kopplin said, “With this standard, we intend to measure a number of characteristics of a new cushion; then expose the cushion to appropriate challenges that simulate aging; then re-measure those initial characteristics to see if anything changed. This was the approach taken with the development of the international standard in 2015: ‘ISO 16840-6 Simulated use and determination of the changes of physical properties of seat cushions.’ The RESNA committee is working toward a U.S.-specific standard that is similar in nature. However, some of the thoughts and discussions we struggle with are about how rigorous the test needs to be.

“The challenges we apply in the lab might at first seem overly aggressive, but they are meant to ‘accelerate’ the aging process, so there’s a balance to find. Accelerating aging with a temperature exposure that’s too high, for example, could degrade some cushion materials in ways that they wouldn’t naturally degrade in real time/real use. From an engineering/testing standpoint, you typically like to test a product to failure to fully understand how a product could fail. But that again may be overly extreme. If the test is too ‘easy,’ it may not adequately predict failure that could occur in three, four or five years of use, so such a test wouldn’t be beneficial, either. As a result, our committee — which consists of dedicated contributors from universities, clinics and industry — attempt to find the ‘sweet spot’ of testing that will give a reasonable prediction of durability, without being unduly aggressive, to better inform the user, prescriber and payor of how cushions can continue to benefit the user in the long haul.”

There’s also the challenge of ensuring that test results are accurately understood and applied by all stakeholders.

Said Cwiertnia: “The U.S. standards group working on this has been in a long debate regarding minimum testing protocols for cushion aging because we are concerned that the testing or information could be misconstrued by funding sources.”

EXTENDING CUSHION LIFE

As discussion continues regarding how tomorrow’s cushions might be defined and tested, there are practical ways to extend the life of cushions today.

“Keeping them clean and keeping dirt and debris out of the material will prolong the life and not accelerate the breakdown over time,” Rogers said.

“The best methods to prevent accelerated aging start with following the manufacturer’s recommendations for laundering, disinfection, storage and maintenance,” Cwiertnia added. “Sometimes putting the cushion cover in the dryer on too high heat will ruin it. I have also seen cushions ruined because they were left in direct sunlight inside a hot vehicle during the summer. Often, bleach isn’t recommended for disinfection because it can ruin cushion materials, so check to see which disinfectants are approved. Choosing the proper style of cushion to match the user’s needs and lifestyle is very important too.”

This article originally appeared in the May 2017 issue of Mobility Management.