by Patricia E. Tully, OTR, ATP Pressure ulcers are a global healthcare problem, costing the United States healthcare system more than $11 billion each year.1 Pressure ulcers affect almost 3 million adults annually and, more than twice as many individuals died from pressure ulcers1 than from motor vehicle accidents.2 Adults 65 years of age and older account for more than 70% of acute hospitalizations involving pressure ulcers, and in nursing homes, more than one in 10 residents has a pressure ulcer.3 In high-risk populations, such as those with spinal cord injures, 60% are likely to develop a pressure ulcer during their lifetime.4 These statistics demonstrate the serious and threatening nature of pressure ulcers, and pose the question to the healthcare industry about how it can proactively reduce the number of annual cases. Pressure ulcers affect a vast number of individuals of varying conditions and diagnoses. Treatment responsibilities extend to the entire healthcare team for them to review the pathological mechanisms causing pressure ulcers and to pay careful attention to early symptoms. Likewise, it falls to the members of this team to pay attention to intrinsic and extrinsic risk factors that contribute to pressure ulcers, and to understand the differences in the pathology related to deformation. One area that deserves special attention in pressure ulcer cases is cushioning, and specifically how cushioning choices affect individuals who use wheelchairs. When it comes to choosing cushions for wheelchair seating, current standards are inadequate to ensure appropriate protection from pressure ulcers. There seems to be an overwhelming set of variables that occupational and physical therapists must consider when selecting a wheelchair or mobility seating products. Between each client’s physical needs and lifestyle, staying current on available products and technology, funding requirements and paperwork, it’s understandable that consideration of one aspect—like pressure ulcer prevention—can occasionally become lost or minimized among all of the variables. However, increasing numbers of therapists and health experts who have seen the effects of equipment that does not “fit” are asking how to minimize the risks of extended seating times—specifically, the risks associated with pressure ulcers and soft-tissue deformation.
Know the Variables, Solve the Problem
Consider the physics of the seated body and the force applied to the buttocks, not just at the ischial tuberosities (ITs), but also the force on the surrounding soft tissue. By increasing the surface area of the body in contact with the cushion, force is spread across a larger area — resulting in reduction of external pressure—which we can clearly see through mapping changes. This reduction in surface pressure is just a hint of the impact seating surface has on the internal risk for tissue damage and deformation. Even cushions categorized as “adjustable skin protection cushions” can deliver a wide range of either risk or protection, since, unfortunately, such cushions are not categorized by how well they minimize internal tissue deformations. Given this country’s significant population of people who use wheelchairs for mobility (about 3.6 million Americans over the age of 15 years5) and the high healthcare system cost of treating pressure ulcers, a change in direction toward prescribing better and safer seating solutions is increasingly essential, as is reliable evidence that can be applied accurately and has clinical significance. New research from the laboratory of Amit Gefen, PhD, at Tel Aviv University in Israel, as well as other leading international labs, is providing a much better understanding of a particularly dangerous and difficult-to-detect kind of pressure ulcer—the sort caused by deep-tissue injury (DTI). Gefen is a professor in the department of biomedical engineering and the president of the European Pressure Ulcer Advisory Panel (EPUAP). As one of several researchers studying the pathway of pressure ulcers—the deep mechanism of injury and cellular deformation, Gefen’s lab recently performed a study that revealed important insights about the best ways to minimize such deformations and, consequently, the DTIs they produce. Part of Gefen’s work involves using finite element modeling (FEM), a sophisticated predictive technology that is new with regard to studying pressure ulcers.
New Model for Predicting Pressure Ulcers
Finite element modeling uses computer software to analyze and predict how tissues within the body will behave. As used in Gefen’s study in conjunction with seated MRIs, researchers were able to look at the soft tissues, the effects and the behaviors of tissues and bones, and the shapes of the patients’ anatomy. All of this visual information enabled researchers to review properties of varying tissues down to the cellular level and import the behavior of the cells and tissues into a computer simulation that can be used for predicting behaviors. This work laid the foundation for their study published in the Journal of Tissue Viability in 2014. This study offered the first tissue deformation comparison between two commonly used cushion technologies—foam-based (representing the largest number of cushions in use) and air-cell-based (ACB) technologies—to help guide clinicians in recommending the best cushion to protect their clients. Researchers analyzed data far beyond mere contact pressure measurements to develop a better understanding of what really happens deep within the body in the muscle and fat tissue, where DTIs occur. All of this research is crucial in pinpointing the extent that a cushion can play in preventing deformation and cell death that leads to DTIs. Through managing extrinsic risk factors, clinicians can become aware of internal deformations sooner, which is vital in reducing the number of pressure ulcer cases. Considering once a deep tissue injury stage is suspected, it’s often too late and the damage is already done. Research shows the primary cause of DTI-based ulcers is tissue and cell deformation rather than ischemia, or lack of blood flow, which acts as a secondary factor. Through evaluation of internal soft-tissue loads in the buttocks and detailed performance comparisons of an ACB cushion and two flat, foam-based cushions with varying stiffness properties (7 kPa and 10 kPa) as used by individuals with spinal cord injuries (SCIs), the results were powerful. For the ACB cushion, immersion was consistently in the 91% to 93% range; for the foam cushions, the range was typically 58% to 65%.6 Consequently, all of the peak stress components were four orders of magnitude (ie, 10,000 times) lower for all three kinds of tissues in the ACB cushion than for the foam models.6 Additionally, the ACB cushion demonstrated lower peak stresses on muscle tissue from bone flattening, and substantially decreased muscle atrophy than was present with the foam cushions. This study also helped researchers conclude just how limited pressure map views are and deduce that even just a slight change in the way a patient is immersed (how deep into the cushion a patient sinks) and enveloped (how intimately it matches the patient’s shape) in a cushion can result in a huge change in what’s happening inside of the body where the ulcers begin. It’s the mechanism of injury and the pathway for the pressure ulcer that healthcare professionals need to be extremely conscious of and concerned with since friction, temperature, moisture, and microclimate significantly affect the skin—the most superficial layer of tissue—of where the person is sitting on the cushion.
Tissue Loading: Small Changes Have Big Consequences
The small changes on the surface area and the ability of the cushion to immerse and envelope a patient result in incredibly vast changes internally. Tissue deformation damage can occur quickly, and ischemia is only part of the story. Healthcare professionals need to be aware of both types of injuries. Damage from deformation can occur in a few hours, whereas ischemic cell deaths take a little longer, leading to pressure ulcers in 6 to 8 hours. This has an impact on how the tissues are loaded, the type of support surface they’re sitting on, and, of course, time. Posture, time, and support surfaces are not typically risk factors associated with pressure ulcer development, but evidence shows they’re having a direct impact and correlation to the safe sitting time and therefore need to be considered as additional risk factors. The variety of commercially available cushions is striking, and some clinicians view cushions simply as commodities. Cushioning solutions range from flat foams, segmented foams, contoured foams, water/gel-filled cushions, honeycomb-like cushions, and air-cell-based cushions, among many others. However, viewing cushions as anything other than serious medical necessities can lead clinicians to make recommendations solely on the basis of price—a well-intentioned but false belief that all cushions are essentially equal. Clinicians under this assumption do not realize the magnitude of the hazard they could potentially be prescribing to their clients. For example, SCI patients represent a key segment of the wheelchair-user population, since many have been victims of severe accidents and will spend the rest of their lives in wheelchairs. Yet many of these patients will die from a pressure ulcer and many more will be affected by one, consequently leading to a significantly reduced quality of life. To further complicate the choice, decisions typically must fall within a matrix of choices related to funding sources and present medical documentation.
Considerations Are More Than Just Cost
The new research from Gefen’s lab and the understanding of the role of tissue deformations in the formation of DTIs provide evidence for a change in direction toward prescribing better and safer sitting solutions through the use of ACB cushions. Unfortunately, solid evidence for which cushion is superior is primarily lacking, partly because of the difficulties and costs associated with randomized clinical trials for isolating cushion efficacies. While Gefen’s findings clearly suggest that the ACB cushions provide much longer safe-sitting times than foams for wheelchair cushion users, further research is needed to understand how body movements, positions, and other common risk factors affect internal tissue deformations and stresses. A policy of simply steering patients toward the cheapest solution without evaluating the ulcer risk to the patient is not only shortsighted but dangerously irresponsible. This incorrect approach can lead to needless maladies, complications, suffering, and even life-threatening conditions. In addition to the physical strain on the patient, there are significant financial impacts to consider; after all, the total cost of managing a single, full-thickness pressure ulcer can be as high as $70,000.1 Thankfully, most clinicians routinely evaluate wheelchair users with respect to pressure ulcer risk; however, objective risk measurements that inform prescription are not readily available. A need exists to provide clinicians with objective measurements of pressure ulcer risk that can be applied on a patient-to-patient basis. Another essential consideration in preventing pressure ulcers is whether the chosen cushion has the adjustability to change with the person through the years, as well as the adaptability to allow tiny movements that occur throughout each day, without increasing the person’s risk. These small, daily micro-movements are actually changing the shape of a patient’s body and impacting the interaction with the cushion. Therefore, it’s not only important that therapists think about what’s happening as the body changes over time with atrophy, bony adaptation, and soft-tissue changes, but also how those changes are affecting the person throughout the day in terms of pressure relief while going up a ramp, down a ramp, and picking up something from the floor. It’s important that the cushion can accommodate these small changes so that it is not increasing force or stresses on the internal tissues along with the external skin. Additionally, a cushion should provide both pelvis and trunk support and sufficient trunk mobility.7 Attention to a cushion’s abilities has important consequences for patient quality of life. Also, because patients adopt different postures when using different cushions (and backrests), posture needs to be assessed along with the functional reach capacities on the selected cushion.
Ethos of Prevention
Any prescribed cushion should be durable enough to last its expected lifetime. The latest Medicare rule is that cushions will be replaced no less than every 5 years, and research shows external and internal anatomy and tissue structures and functions change considerably in the months and years following the loss of sensation and mobility. Therefore, any cushion chosen needs to be adjustable, adaptable to the daily movements of the end user, and accommodating enough to respond to any change in anatomy, tissue composition, and long-term tissue (patho)physiological changes such as weight and fat mass gain, skeletal muscle atrophy, fat infiltration into muscles, bone loss, bone shape adaptation, and more. In conclusion, the more immersion and envelopment a product delivers, the more it’s going to increase the end user’s surface areas, resulting in decreased force on the skin and minimizing internal risks simultaneously. Along with higher-quality and better-performing cushions, clinicians’ attention to internal deformations and extrinsic risk factors also play a part in pressure ulcer prevention. Attention to these preventative measures should ultimately result in fewer pressure ulcers occurring each year, less funds spent on treating them, and happier and healthier patients overall. RM Patricia E. Tully, OTR, ATP, has been a registered occupational therapist since 2000 and an assistive technology practitioner since 2009 through Rehab Engineering Society of North America (RESNA). She is currently employed as a resource specialist in the Education Department for Therapy Services at TIRR Memorial Hermann in Houston. Tully has been at TIRR Memorial Hermann since 2000, where she has worked as a treating clinician with the Brain Injury and Stroke Program, Pediatric Program, Adolescent Team, and the Out-Patient Wheelchair Clinic. Tully earned a bachelor of science in community education from Texas A&M University and a bachelor of science in occupational therapy from Texas Tech University. She volunteers as a Board Member for Rehabilitation Services Volunteer Project (RSVP) in Houston, a group that provides physical medicine and rehabilitation (PM&R) services and equipment to those who otherwise cannot access these services. For more information, contact [email protected].
- Duncan KD. Preventing pressure ulcers: The goal is zero. Jt Comm J Qual Patient Saf. 2007;33(10):605e10.
- National Highway Traffic Safety Administration (2012, January 1). Retrieved September 11, 2014, from http://www-fars.nhtsa.dot.gov/Main/index.aspx. Accessed August 5, 2015.
- Park-Lee E, Caffrey,C. Pressure Ulcers in Nursing Homes in the United States: 2004. NCHS Data Brief. Feb 14, 2009.
- System N. SCI Forum Report: Picture this… Pressure Mapping Assessment for Wheelchair Users. SCI Forum Report. 2004.
- US Census Bureau, Americans with Disabilities 2010.
- Levy A, Kopplin K, Gefen A. An air-cell-based cushion for pressure ulcer protection remarkably reduces tissue stresses in the seated buttocks with respect to foams: Finite element studies. J Tissue Viability. 2014;23:13-23.
- Sprigle S, Wootten M, Sawacha Z, Thielman G. Relationships among cushion type, backrest height, seated posture, and reach of wheelchair users with spinal cord injury. J Spinal Cord Med. 2003;26(3):236-243.
Thank for the very interesting article with so thoroughly researched information! “…review properties of varying tissues down to the cellular level and import the behavior of the cells and tissues into a computer simulation that can be used for predicting behaviors” – that sounds like a very sophisticated predictive technology indeed. I wonder what exactly they actually read at the cellular level to make these predictions. Fascinating and most importantly – how promising for increasing life quality!
Thank you for the very important and interesting article. Could you please list the references cited in the report?
The references the author cites throughout the article appear at the bottom, below her bio.
Thank you for your feedback!