Showing Their Age

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.”