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Pressure Injuries: Do We Know What We Know?

How Current Research Is Shaping Future Risk Assessment

Pressure Injuries


Not too long ago, pressure injuries were pressure ulcers or pressure sores, and clinicians were only taught to watch for changes in the color, texture and temperature of patients’ skin. Then came research into and understanding of deep tissue injuries, which occur internally and can’t be observed at surface-of-the-skin levels. Now in answer to that, new studies have examined how ultrasound technology can play a role in risk assessment — and could shape wheelchair seating development going forward.

Interviewees for this story were Jonathan S. Akins, Ph.D., assistant professor, Widener University, Chester, Pa.; David M. Brienza, Ph.D., professor and associate dean for research, School of Health & Rehabilitation Sciences, University of Pittsburgh; Professor Amit Gefen, Ph.D., professor, department of biomedical engineering, Tel Aviv University; and Kara Kopplin, senior research manager, Research and Innovation, Permobil.

While their main focal point was the study of ultrasound use in pressure injury risk assessment, their discussion also referenced aspects of pressure injuries that we’ve known about for some time, as well as what risk assessment could look like in the future.

The Background

Kara Kopplin: We were very interested in being a part of research studies around the risks of pressure injuries, with a goal toward prevention. We’ve done quite a bit of partnership work with Dr. Gefen, with Tel Aviv University, with MRI [Magnetic Resonance Imaging] and the finite element models, then in the last couple of years, with Dr. Brienza and his group as well, analyzing direct MRI imaging with people sitting on different cushions. We know the seated MRI can’t be used in a clinical setting, and our hope was that something would evolve that would someday be able to provide a patient-specific tool to assess risk of pressure injury.

So that’s where we pursued the use of ultrasound. We wanted to see if that could be a valuable method that could be more cost effective and more accessible to people in the future, to provide a better assessment of risk than what is available today, and hopefully lead to the prescription of seating systems and protocols that will be personalized for the best individual outcomes.

Q: What Can Ultrasound Accomplish?

Mobility Management: Did the research show that ultrasound technology was a comparable substitute for MRI?

David Brienza: Dr. Gefen has done this body of work over the last 10 years in which he’s been able to generate an understanding of what’s happening in the deeper tissues. What’s allowed him to do that was being able to fine-image the geometry of the tissue and then use the finite element modeling tool to simulate different conditions. His work has generated the knowledge of what parameters are important to this problem.

The important research question here really isn’t Does ultrasound substitute for MRI? I think the better and related question is Does ultrasound give you the critical information you need to predict the effects that are important for determining risk, and determining what intervention is appropriate for a particular person in a seated situation?

We weren’t looking to see whether ultrasound did the same thing as MRI, because it doesn’t. MRI gives you a much more complete picture of the anatomy. But what we were interested in is Can ultrasound measure those critical tissue thicknesses and the critical characteristics of the bone structure, the ischial tuberosity (IT) bone structure? Can we measure that distance, and is that measurement equivalent to the measurement we get using the MRI methodology? Finally, can we assess, in this case, the curvature of the bone? If successful, we would have taken the first step toward developing a clinically feasible method for assessing the important parameters related to deep tissue injury risk.

Amit Gefen: Dave very accurately described the background and the motivation. The work that we have been doing has consistently showed that it is the anatomy and the individual anatomical differences which are very different across individuals. It is the anatomy that has the strongest influence on the state of mechanical loads in tissues, particularly the peak loads in tissues.

For example, the sharpness of the bony prominences: It’s unbelievable how distinguished these differences are across individuals. One [person] could have a very sharp bone, and the other could have a more blunt bone surface. Even when you look at the same individual and you look at an MRI scan: You look at the left bone and the right bone, and you see a difference in the curvature of the bone, just from the left to the right side of the body. Much like your right arm is not identical to your left arm.

So the thickness of the different tissue layers, the overall thickness of the soft tissues, that’s important. But actually, these anatomical features are much more important than the stiffness properties that these tissues have, which also vary across individuals.

What we discovered is it’s a challenge to measure mechanical properties of tissues in living human beings. There are now emerging methods that are specific for that. It’s still quite expensive and not that accessible. What we discovered is if you know something about internal anatomy, then the mechanical properties are less important because the differences across individuals in tissue mechanical properties are not as dramatic as the differences in anatomies, that is, in internal anatomical features. And that basically leads to what Dave said about the need to then cost effectively capture these anatomical features of the individual without sending people for MRI scans, which is obviously not something that you would do outside the research lab.

Q: Why Is the Idea of Asymmetry Important?

Mobility Management: So a critical finding of your research was that not only do the structures of the ischial tuberosities vary from person to person, but our ITs also vary in shape within our own bodies, meaning that our left IT could be differently shaped than our right IT?

Jonathan Akins: I think what the study has done is confirmed that there is this difference from side to side and this asymmetry in this data that we collected — this particular study was on six people, and four of them had spinal cord injuries. One of the parameters that we published is we found there were pretty dramatic differences in the way the tissue deformed from side to side in a particular person. So I think the assumption that there’s [symmetry] is not correct, especially in people with spinal cord injuries.

Gefen: Human beings are not symmetrical to start with. But sometimes, a condition or a comorbidity may worsen that or make differences larger.

People have used pressure mapping a lot in the past to capture asymmetries in posture and in the structure of the buttocks. Some of the information you wouldn’t be able to capture with a pressure map because the pressure map only shows you asymmetries that present themselves on the surface of the skin, because that’s where the measurement is taking place. Asymmetries deep within the body — for example, an asymmetry in the left to right ischial tuberosities, say in the sharpness or the shape of the bones — wouldn’t necessarily manifest in a pressure mapping measurement. Because you have all these soft tissue thicknesses that kind of mask the information in the deep tissues. So you may have serious differences and exposure to mechanical loads around these bony prominences because they’re not identical (because they’re asymmetric), but you can’t really detect that information when you’re far away from that site, that is, when you’re measuring quantities on the surface of the skin.

Akins: As an example of that, there are cases in this study where we found that some people sat on muscle on one side of their buttocks and did not sit on muscle on the other side. They sat on adipose tissue, on fat tissue.

Gefen: Pressure mapping wouldn’t necessarily show you that. Because the pressure mapping doesn’t know that on one side there is muscle tissue, and on the other side, the bone is actually covered by fat.

Q: How Do MRI & Ultrasound Differ in the Information They Provide?

Akins: I think one thing to pull back into consideration is the sharpness of the ischial tuberosity, and that can play into that asymmetry. One of the interesting findings is how we were able to use ultrasound more reliably to obtain the radius curvature compared to our T1-weighted MRI images. We found actually poor reliability between raters of obtaining a “good” radius curvature. And that was due to the inability to differentiate between cortical bone and the musculotendinous junction. We could have used a different type of MRI image, T2 weighted, to potentially solve that issue, but we can easily see that and measure that structure with the ultrasound.

So from a clinical perspective, that could be something very useful: to not only see that asymmetry of how they sit, but what is that sharpness, that radius curvature between the two sides?

Brienza: How the tissue compresses and how the loads are distributed varies based on posture and how the pelvis is tilted at any particular point in time. But those anatomical features of the bone itself are going to be constant. So if you find a person with a very high radius of curvature, indicating a high-risk situation, then you know to take some special precautions for that case. Pressure mapping might not detect this risk factor.

Maybe they were leaning to their good side when you took that pressure map. So you didn’t see that stress concentration, that pressure concentration because the weight was distributed away from it.

Consider the bone shape as a fundamental piece of information that’s going to help determine how the load is going to be distributed in the tissue beneath that bone. And the other thing that Jon said that is really important: The ultrasound is perhaps a better methodology for measuring bone curvature because you can’t distinguish between the muscle junction with the bone and the bone itself in the type of MRI imaging we performed.

Q: Does Ultrasound Technology Offer Practical, Operational Advantages?

Gefen: What we should also take into account with regards to imaging technology: MRIs are probably not going to be much smaller than they are today. There are some miniature MRIs, but I don’t see an MRI system going into someone’s pocket.

With ultrasound systems, there is huge potential — you can see the technology going there, where we end up with devices that look like pens that we can stick in our pocket. We can talk to our cell phone using a Bluetooth connection, and we will put that pen-like device on the [patient’s] skin, and you’ll see what’s going on internally on the screen of your cell phone.

So looking at where technology is going and trying to extrapolate for the future, we should consider that risk assessment tools as we know them today are going to be totally different 10 years from now, maybe five years from now. As technologies are able to look at deep tissues, I’m sure that ultrasound will play an important role. And essentially, we’ll end up with risk-assessment tools that are able to take into account anatomical features that we’re not taking into account using existing tools.

For example, in many of the existing risk-assessment tools, you take the nutritional status of the patient into account by measuring the BMI [body mass index]. BMI is essentially an anatomical feature which is rather easy to assess: You just need to measure the [patient’s] weight and height. If you could assess, for instance, the sharpness of the ischial tuberosities as easily as you would measure someone’s weight or height, you could have a critical piece of information for the risk assessment because you know the ischial tuberosities can be as sharp as a nail or as blunt as the bottom of a cup. If you can measure that, then you know this individual is at higher risk for developing a deep tissue injury because [the IT] looks like a sharp nail. That would immediately shape your overall risk assessment, and you’re currently not doing that because you don’t have the technology for that insight into the deep tissues.

I see a potential for nurses, for anyone who’s doing risk assessment, to have these tools in their pockets in the next couple of years, which will then change the risk assessment procedures that we know and will eventually save lives.

Brienza: Include time [savings] as well, because each of these MRI scans took about 15 to 30 minutes, and with the ultrasound probe, we’re able to obtain that measurement in a matter of minutes. But it’s also done at the bedside, so that’s hitting other points: We have the patient lie down in a seated posture on a plinth [for an ultrasound], versus having to transfer into a seated MRI, which is challenging for people that have a spinal cord injury. And the transportation [for an MRI] just adds hours of time compared to minutes [to conduct an ultrasound assessment].

Gefen: It’s important to not only describe things as they are today, but also to look into what could happen in the very near future as we see miniaturization of these ultrasound devices. So they will be very cheap to the point that every nurse could have one in his or her pocket and they will do that regularly, five or 10 times a day, whenever they see a patient, whenever they suspect that there is something going wrong. Much like in Star Trek, they could put this device on the skin, and it will give them complete diagnostics, or if not complete diagnostics, at least the internal anatomy. Actually, the technology does exist today, and it’s just a question of time until we see it commercially.

Q: How Could This New Technology Improve the Continuum of Client Care?

Mobility Management: It sounds as if ultrasound, because the technology is more efficient to use and particularly if miniaturization literally places an ultrasound device into the pocket of every acute or long-term care nurse, has the potential to greatly expand and improve risk assessment.

Gefen: The other thing to think about is the development of a field in engineering or computer science or in both that we call big data. Being able to monitor, at will, anatomical or any other type of features in the body and then comparing them to a huge database of measurements being taken at the same time in the same facility, or in other facilities and being stored in the cloud. And then being able to analyze [observations of a patient] in real time because we’ve seen that patient’s normative data — [are current readings] deviating from normal values?

Again, that data being transmitted to the cell phone of the nurse or to her tablet, seconds or fractions of seconds after she takes the measurements — that’s huge. It’s not only the ability to visualize and provide the image of what’s happening in the body, but it’s also the computer being able to tell you: That’s normal.

Brienza: The other piece to this is once you understand the characteristics of the person and you can model it, then you can simulate interactions with external devices, like cushions, and start to predict how someone is going to perform when they sit on a cushion and how the characteristics of that cushion may change how the person is being affected and how their tissues are being affected. We do know that tissues deform differently when people sit on cushions with different characteristics, so we can use that information to choose, if you will, the best cushion based on the personal characteristics and the characteristics of the cushion.

These measurements that we’re talking about get even more difficult when you’re talking about a loaded situation. The ultrasound measurement we’re making now is of someone lying on their side [with] their buttocks exposed. It gets much more difficult when you try to take measurements while forces are being applied.

If we can parameterize the model of the person and then apply that to a cushion, we can predict how well that cushion is going to protect that person and their tissues from harmful deformation.

It’s a combination of general knowledge and population information with specific risk information to arrive at the best solutions.

Q: How Does the Research Move Forward from Here?

Mobility Management: Given what you’ve learned, will you continue to study these technologies and to advance what you’ve discovered?

Kopplin: We are doing MRI assessments with Dr. Brienza’s team to further understand the differences in anatomy, how different people’s structures are and how that translates into that internal tissue stress and risk that Amit and his team will be analyzing. We are advancing the research to better understand the role that cushions, wheelchairs, positioning, and protocols can play in ensuring the best outcomes for wheelchair users, which is exciting.

Gefen: We are basically laying the foundations for technologies, either building upon existing or new technologies that will aid clinicians in doing their daily risk assessments with patients in a world that has currently seen no technology at all in those aspects. It’s now only based on nurses’ skills, experience, sometimes subjective impressions that she may have when a patient is admitted to the facility. We’re offering a thoroughly different, revolutionary, bioengineering approach based on technology and solid evidence that will change the world as we know it today and as related to risk assessment. That’s a fundamental point to emphasize. It’s not just the fact that we took ultrasound and compared it to an MRI. That’s the technical aspect of it. The important aspect of it is that introduced technology to a field which is virgin in that aspect.

Brienza: We were trying to take down that barrier that was between utilizing that knowledge that’s been generated over 10 or 15 years and applying that in the clinic. There was this barrier that we couldn’t make the measurements. So by assessing whether ultrasound can make those measurements, it takes that barrier down.

Gefen: We translate the basic science that we have done and the findings that were supported by sophisticated, expensive imaging like MRI, and with ultrasound, we are translating that into the clinic and to the bedside.

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

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