Deep Tissue Injury Research, Part IV

How Clients Change & What We've Learned

In 2014, Mobility Management began a series on the pressure ulcer research of Amit Gefen, Ph.D., professor in biomedical engineering at Tel Aviv University. Gefen, immediate past president of the European Pressure Ulcer Advisory Panel, brought a new perspective and new tools — including laboratory-generated cells and tissues that could be tested, and those results then modeled and extrapolated via computer programs — to the task of better understanding what pressure ulcers are, why they form, and how they challenge seating & positioning professionals trying to keep wheelchair users safe.

That series of clinical articles led into a second research series in 2015, this time concentrating on deep tissue injuries (DTI).

The traditional view of pressure ulcers focuses on ischemia. Ulcers of that type were thought to be caused by inadequate blood flow, often as being a result of prolonged pressure over a bony prominence, such as an ischial tuberosity (IT). Current clinical practices for reducing that sort of pressure ulcer risk include watching for changes in skin color and temperature. But Gefen’s research, as well as research by other notable scientists around the globe, indicated that ischemia is not the only way pressure ulcers form — and DTIs are not so easily identified by looking for changes in skin texture or color. In fact, DTIs are influenced by factors we’re only now starting to understand.

Gefen’s industry partner in this research has been Kara Kopplin, BSc, the Senior Director of Efficacy & Research for ROHO Inc.

It’s an evolving area of study, one that will impact not just today’s wheelchair users, but tomorrow’s. Here we wrap up our series by discussing how wheelchair users’ changing bodies can affect their risk.

Differences in Scar Tissues

As discussed in November, Gefen’s research covered not just how healthy tissue responds to forces and distortions, but how compromised tissue does as well. DTIs are caused by sustained tissue deformations. Gefen wanted to determine whether the immersion and envelopment strategies advanced by ROHO’s air-celled cushions would succeed in those environments, including “different types and shapes and sizes of scars that clinicians see in the real world.”

Gefen explained that ultrasound scanning work and anatomical mapping done for example in Japan could identify existing scars by looking at deeper tissues as well as what was visible on the skin. “So if you see something, that can give you a hint that this patient had a pressure ulcer already,” he noted. He used the names that Japanese researchers created to differentiate the types of scars that seating specialists often see in their clients (see diagrams).

Deep Tissue Injury Research

In the illustrations, the ischial tuberosity is white. The gluteus muscle is red and is seen directly around the IT. Surrounding fat tissue is yellow, and scar tissue is blue.

In the cross-sections, you’ll see the “Thin” example has scar tissue on the surface of the skin. “Deep” has scar tissue at the IT and gluteus muscle interface. The “Sandwich” (abbreviated “SW”) scar shows scar tissue both internally at the IT and on the surface of the skin. And the “Hourglass” scar (abbreviated “HG”) has scar tissue that traverses the distance from the IT to the surface of the skin.

Gefen pointed out that it’s important to understand how scar tissue differs from healthy tissue, and how it reacts differently to force.

In the Sandwich scar, for instance, he noted, “You can see how the scar concentrates the mechanical forces. The forces are basically going through the scar. That’s a well-known principle in mechanical engineering: Forces will always tend to go through stiffer structures. They go all the way down through the scar. But the scar cannot deform much, so at the interface, the non-scar tissues are deforming, and they’re deforming a lot. They’re deforming for themselves and compensating for the tissue that can’t deform, which means that they deform excessively.”

Gefen said he found that if scar tissue is milder, the immersion and envelopment offered by the ROHO air-cell cushions he used did greatly compensate for it.

“If the scars are more mild, you actually get load values in the tissues that are similar to what you have in tissues and skin that are normal,” Gefen said. “The immersion and envelopment effect is so strong that it can mitigate not only the presence of force between the bone and the soft tissue, but also the presence of the [mild] scar. And we quantified that. In each and every case, we divided the value of the mechanical loading in the tissues where there is a scar by the volume of the mechanical loading as if there was no scar there.

“So ideally, you would want these values to be around 1 or lower than 1. On a ROHO cushion, in some of the [more severe] scars, you do get values above 1.”

But Gefen added that for less severe scars, “most of the time, it’s controllable. [The ROHO air-celled cushion] contains them.”

In other words, those immersion and envelopment strategies can significantly compensate for and manage those scar conditions.

Managing Scars as a Chronic Condition

This research suggests that even when scar tissue is already present, it can be possible to manage pressure ulcers and deep tissue injury risk safely, as a chronic condition — depending on the severity of the scarring as well as the intervention chosen.

Gefen visited long-term care facilities and rehab centers all over the world, and noticed that the most aggressive, significant seating interventions were often reserved for “patients in the worst condition.”

That means other patients thought to be at lower risk for pressure ulcers could be denied the most effective interventions until they deteriorate. That’s far from ideal, but Gefen pointed out that the reasoning has been that clinicians in those settings haven’t understood why those immersion and envelopment strategies work — thereby making them more difficult to justify.

In pointing out the importance of these research findings, Kopplin explained, “Now that we have the evidence, we can start those conversations with them, with research data instead of anecdotal or subjective information. That’s part of the broader plan with this research. We’ve never known why some people with scars can be managed, and some with scars can’t.”

“It all points to immersion and envelopment,” Gefen said. “And as you increase immersion and envelopment, you minimize the internal tissue deformations. You buy yourself more safe sitting time.”

Clients’ Bodies Change — Quickly

Another feature of the research to emerge is how quickly a client’s body can change, for example, after a spinal cord injury (SCI). Gefen’s research discussed how rapidly fat can encroach upon muscle in newly injured SCI patients. Intramuscular fat can increase significantly, within the weeks post injury, thereby drastically changing the nature of the tissue that wheelchair seat cushions are trying to protect.

“Before the person breaks down, there are so many changes that are ongoing,” Gefen said. “That all takes place in weeks. Dramatic changes. In about 20 to 40 weeks, [newly injured SCI patients] lose 40 to 50 percent of their bone and muscle mass in the buttocks. In half a year.”

That’s a problem, Gefen pointed out, given that those clients continue to use the same seat cushions prescribed for them months before, when their bodies were much different.

“Here in the States, [funding sources and insurance companies] are pushing for a reimbursement factor of [one cushion] every fifth year. They’re thinking about the cushion. They’re thinking about the materials of the cushion — for instance, when the foam collapses. They’re not thinking about the patient. The cushion still hasn’t aged; it’s still brand new. But the person has gained a little bit of weight. If this is a non-adjustable, contoured foam cushion for example, it would not fit the shape of the buttocks after that weight gain. The buttocks are not sitting in the holes [of the cushion] any more.”

As intramuscular fat continues to develop, Gefen said, “It’s practically taking over, and if you wait long enough, there will be practically no muscle. You have stripes of fat in between muscle layers. These muscles internally slide against each other [on the cushion]. That will add even more shear internally in the tissues.”

So in addition to its ability to immerse and envelop the client’s shape when it’s prescribed, Gefen said a cushion needs to adjust to the client’s evolving body shape as long as he/she is using that cushion. This feature is called adjustability, and Gefen said it is a critical design feature of a good wheelchair cushion.

“So how well can the cushion adjust as the person changes?” Gefen asked. “What we find is that at the time of the fitting, you get shear deformation levels that are tolerable by themselves. A few weeks later, it’s tripled. The patient doesn’t even know that; it all happens internally. It’s not only the immersion and envelopment, but also the ability of the cushion to adjust to body changes.”

Kopplin said that when a person needs to function in their daily living environment, for example shifting in the chair, reaching for objects (and therefore changing sitting posture ), or even changing clothes, the cushion needs to accommodate these movements to continue to protect the client. That’s the real-world interaction between the client and the cushion. They refer to this critical cushion function as adaptability, and it’s needed not just as a client changes over weeks, but even during a typical day.

“You shouldn’t have to constantly adjust your cushion every time you’re going to lean forward to work on your computer,” she said. “It needs to respond and adapt to you.”

Gefen referred to a study that Kopplin conducted at ROHO to look at the drastic postural changes that take place simply when a client changes from flat shoes to high-heeled ones.

“I can imagine what’s happening internally at that bone and in the soft tissues surrounding it, and what a great risk that person is at, just from changing their shoes,” Kopplin said.

The current understanding of deformation and DTI, along with these research studies of the effects of scar tissues, body changes, custom contoured cushions (which may no longer “fit” over time) and even daily movements and wardrobe changes, led Gefen to a conclusion about what seating clinicians, ATPs and cushion manufacturers should strive for.

“We can actually say here,” he noted, “that Envelopment + Adjustability + Adaptability = Safety.”

Editor’s Note: Read “Computer simulations of efficacy of air-cell-based cushions in protecting against reoccurrence of pressure ulcers,” research by Gefen, Kopplin, and Ayelet Levy, in the Journal of Rehabilitation Research & Development (rehab.research.va.gov/jour/2014/518/jrrd-2014-02-0048. html) Mobility Management illustrations by Dudley Wakamatsu, based on research by Gefen, Kopplin and Levy.

This article originally appeared in the February 2016 issue of Mobility Management.

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