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Imagine a seating evaluation for a client who needs complex rehab technology (CRT) interventions.
As part of the evaluation and fitting process, the client sits on a cushion and comments on how he feels as the seating team notes his posture and how well the cushion fits him as he’s sitting still. The group tries several cushions before settling on the one that seems to be the best fit. Maybe there’s a pressure mapping session, as well, to look for pressure points.
Everything looks good and feels good.
Then the client’s phone, which was sitting on the table next to him, rings. Automatically, he leans to his left and reaches toward the phone, shifting his weight to the side to do so.
What’s just happened to the cushion he’s sitting on?
Cushions & the Active Client
A wheelchair cushion that does its job well is also likely to be a cushion that’s used a lot. Cushions with higher HCPCS codes — the ones for skin protection and positioning and/or adjustability — are designed with the expectation their users will spend a lot of time in their wheelchairs.
Those cushions are therefore likely to be exposed to a number of different activities and environments during their lifetimes. The more active the client, the tougher he or she is likely to be on the cushion.
“More active clients usually spend more hours in their chair per day, may have more frequent transfers and other movements, exposure to sunlight and more temperature variations,” said Susan Cwiertnia, Susan Cwiertnia, PT, MS, Director of Medical, VARILITE. “All of these place more demands on a cushion in regards to wear and tear. Certain materials or material combinations are more durable, while others like foam would wear faster. Types of activities and transfer also make a difference — for example, using a slide board will typically cause a cushion to wear more.”
Jean Sayre, MSOT, COTA/L, ATP, CEAC, VP of Quantum R&D Clinical Development for Quantum Rehab and Pride Mobility Products, said understanding how the client will use the cushion is critical to selecting the optimal product.
“I always ask for ‘a day in your life, from the time you get up to the time you go to bed,’” Sayre said in describing the questions she has asked clients during evaluations. “That also accounts for transfers they’re doing.”
The glimpse that clinicians and ATPs get during a pressure mapping, for instance — when the consumer is sitting still and in a centered position — isn’t necessarily an accurate picture of how the cushion will be used in the real world. During daily activities, consumers lean from side to side while reaching or doing weight shifts. Their bodies move as consumers self propel, as they tilt and recline, as they transfer from their chairs into bed. All of this movement impacts the shape the cushion assumes, how weight is distributed in and across it, and even how the cushion’s cover interacts with the client.
So how do manufacturers design cushions that do their jobs when clients are sitting still and while they’re moving?
Anthropometrics & Design
There is a range of seating possibilities for these clients, Cwiertnia said.
“[One] extreme would be a custom-contoured cushion that is uniquely designed for an individual and often functions to prevent progressive deformity or abnormal tone,” she explained. “These cushions can limit activities if the client engages in activities that the cushion was not designed for.”
Most CRT clients use less-customized products — cushions that have skin protection and/or positioning features, but are still designed to fit a range of consumers rather than a particular individual.
“When designing ‘off-the-shelf’ cushions that have contours or features that are dependent on anatomy, the engineers try to incorporate anthropometrics, which is scientific information about humans’ sizes and shapes,” Cwiertnia said. “Since the ‘average’ human doesn’t exist, the engineers have to determine a range above and below the average that they want to accommodate. The goal is to develop a shape that will work for a majority of clients, but may not work for everyone.”
“Unfortunately, we don’t have the tools to see how a person is sitting all day long,” Sayre said. “But what we’ve done is work with anthropometric measurements. We know that, for instance, in an adult pelvis, the ITs [ischial tuberosities] are normally spaced anywhere from 4.5″ to 5″ wide. You go with that as your foundation.”
Of course, for every client who fits within that “average” range, ATPs and clinicians can point out a client who doesn’t.
“I’ve measured some ITs that are 7″ across,” Sayre recalled. “So you have to make accommodations for that. Normally, you make the [cushion] well oversized, because for instance, if the person goes into tilt, we have no problem. But if the person goes into recline, and then they tilt and you open up that hip angle, you are going to have some shearing and movement. So you make that well a little bit bigger to accommodate [their position]. You figure out how much you want that person to move.”
There are also anthropometric differences between male and female users. “When you look at the adult pelvis, there are gender differences,” Sayre said. “With the male pelvis, the ITs are a little bit closer than a female’s, because a female’s was designed to have children. So female pelvic girdles are a little bit wider, and those ITs are a little bit wider versus a male’s.”
Sayre said that during evaluations, she has observed how movement can change the client’s position on the cushion.
“I would have them lean forward and have them go into recline or tilt, because if the well is too small, their ITs might shear and hit the edge. Sometimes I would chamfer the edge off [the cushion] if I could get to it. Sometimes the top layer of the visco [foam] is glued and you can’t get to it. Then you have to choose a different cushion.”
Cushion covers are affected when clients move — but covers can also impact movement in return.
“Cushion covers are often an integral part of the cushion design and function specifically to that cushion,” Cwiertnia pointed out. “Covers can provide protection to the cushion from daily exposure to dirt, moisture, UV exposure, and physical wear. Some covers are designed to assist with the breathability of the cushion, pressure management, moisture management, friction and even for flammability and anti-microbial protection.”
Cover properties can vary according to their construction, Sayre noted.
“For instance, mesh is not only used for air flow, but some people like it because it’s a little more abrasive than Lycra or nylon,” she said. “Some people use it to keep themselves in place, because otherwise, they could slide all over the cushion.
“[Mesh] acts as a stabilizer. For some people, if they’re active and able to get in and out [of the chair], mesh keeps them from fatiguing as much. It keeps them upright. For instance, I know a gentleman with a C5-C6 [spinal cord injury], and he will not use anything but mesh because it keeps him stable. It keeps him in place. Some people put mesh on the backrest.”
Just as some consumers prefer the more tacky texture of mesh to help them stay in place, others prefer a smoother surface with less resistance because such a cover can facilitate transfers.
“For CoolCore,” Sayre said, referring to Stealth’s cushion cover technology, “when I was looking at how the fibers are woven, we wanted to use a matte finish. There are two sides of the material, so we used the matte finish side that’s not as slippery.”
But Sayre said the Stealth team also used the fabric’s weave to facilitate side transfers without affecting forward movement in the chair.
“The way the fibers are woven,” Sayre explained, “you slide a little bit easier side to side, but not forward. So when you’re doing a side transfer, you don’t slide forward out of the chair. [The fabric] helps to keep you where you need to be, in that sacral well. This makes it a little bit easier to do side-to-side transfers.”
Since the fibers don’t encourage forward movement, the fabric’s weave doesn’t contribute to sacral sitting. But if a client lacks lateral stability, and therefore wants to avoid facilitating side-to-side movement, a different fabric weave might be a better choice. As Sayre pointed out, in seating there are pros and cons that constantly need to be balanced.
“It’s about prioritizing how you use the chair, and then also prioritizing how you use the cushion and the cover,” she said.
There’s a wry observation in CRT that when something goes wrong with a seating and wheeled mobility system, the wheelchair seat cushion is often the very first component to get the blame.
Yet, in this day of hurried evaluations, how much time is spent on cushion fitting and trials?
“I think cushions are an afterthought,” Sayre said. “The cushions and the backs are one of the most important systems. That’s what clients sit on. You have people sitting there for 15 or 16 hours a day.”
She would like cushions to get the same critical and individual consideration that a CRT wheelchair does. “The cushions are also complex accessories, complex devices,” she said. “You should be able to build the cushion to the person to match their needs.”
And when a consumer qualifies for a CRT wheelchair, Sayre would like seating teams to think along those same lines — that a similarly complex cushion, carefully chosen and fitted per the client’s specific needs and functional goals, would be the optimal choice.
“For complex rehab,” she said, “we should start at the skin protection and positioning level [of cushion]. It should be helping you with your skin protection, and it should be helping you with your positioning. And the cover makes a big difference, too.”