Minimizing Pressure Injuries Among Wheelchair Users

by Rosemarie Battiato, PT, MPT; Caitlin Corbin, PT, DPT, NCS; Jillian Kenderish, MOTR/L; and Linda Lantieri, MPT, ATP

In April 2016, the National Pressure Ulcer Advisory Panel (NPUAP) redefined pressure ulcers and injuries. The definition is migrating away from the term “ulcer” to the new term “injury.” According to the NPUAP, a pressure injury is localized damage to the skin and underlying soft tissue, usually over bony prominences or related to a medical device or other device. The actual injury can present itself as intact skin or an open ulcer. The injury is the result of a combination of pressure and shear forces. The spinal cord-injured population or those with impaired sensation are at significant risk to develop pressure injuries because of decreased perfusion, comorbidities, nutrition, and the condition of soft tissue.

The updated staging system, according to NPUAP, includes the following¹:
• Stage 1 Pressure Injury: Non-blanchable erythema of intact skin
• Stage 2 Pressure Injury: Partial-thickness skin loss with exposed dermis
• Stage 3 Pressure Injury: Full-thickness skin loss
• Stage 4 Pressure Injury: Full-thickness skin and tissue loss
• Unstageable Pressure Injury: Obscured full-thickness skin and tissue loss
• Deep Tissue Pressure Injury: Persistent non-blanchable deep red, maroon, or purple discoloration

The clinician’s understanding of the new pressure injury stages is imperative because this knowledge often drives the decision of appropriate durable medical equipment for the patient. When clinicians are evaluating a patient for a wheelchair, he or she must consider not only the pressure forces but the shear forces as well. Recommending a proper wheelchair and consideration of an appropriate seating system is paramount to a successful outcome for the patient. That successful outcome would require proper posture and positioning, and minimizing the effect of pressure and shear forces on the skin.

This article explores how therapists in Magee Rehabilitation Hospital’s Wheelchair Seating Clinic educate patients on injury prevention, and how clinical decisions are made in the selection of pressure-relieving cushions.

The Initial Evaluation

Research has shown that incorporating a specialized seating clinic in a client’s inpatient and outpatient rehab program can help to reduce the incidence of pressure injury occurrence as well as the acute care readmission rates due to pressure injuries.² At Magee, within 72 hours of admission, each client is assessed with a postural evaluation by the seating clinic to identify their specific range of motion and postural deficits to identify the optimal seating system for them before they spend any significant time sitting.

A primary goal of the initial evaluation should be to identify the best weight-shifting option for the client, which can be done in collaboration by the seating clinic and the primary treatment team. When they initially arrive to acute inpatient rehab, clients may not be able to physically perform a weight shift, so they may require a tilt-in-space wheelchair with a tilt back being their primary mode of pressure relief. Any caregivers who are present are trained on how to perform these. In addition, the client can be provided with a timer which can be attached to their chair as an auditory reminder to call for a weight shift. As their physical and medical status improves, and clients are taught how to perform multiple different types of weight shifts, their wheelchair can be changed to a manual wheelchair.

Types of acceptable weight shifts include a push-up weight shift, anterior weight shift, and lateral weight shifts. If the client requires a powered wheelchair, they will continue to perform tilt-back weight-shifts. However, they will have more independence and will not have to rely on caregivers to perform these weight shifts. At times, Magee uses a pressure mapping system as a visual assist for the clinician and patient to ensure they are achieving adequate pressure relief.

Using Pressure Mapping to Address Injury Path-Specific Factors

On the outpatient side, pressure mapping is not typically used as a predictor; it is not standard protocol to Pmap all patients. Sometimes, however, pressure mapping is used to educate and as a biofeedback tool that helps people understand the benefits of tilt and the use of tilt and recline (ie, understanding which positions provide most optimal off-loading and pressure redistribution).

Within the wheelchair clinic all seating clinicians are involved in performing pressure map evaluations, in collaboration with general staff. Use of the system is limited to ensure that those who are using the pressure mapping system are familiar with it and its interpretation.

Prior to initiating use of the pressure map, a complete postural evaluation is performed on each client to assess range of motion, asymmetries, flexibility, and functional sitting balance. That information is utilized when selecting the most appropriate seating initially for the client, and the pressure mapping is used in conjunction with our clinical judgment to confirm appropriateness of the selection. For example, if a person is flexible but has complete postural collapse due to lack of abdominal strength due to their level of injury, that person will want a cushion/backrest system that provides appropriate positional support along with skin protection. By putting someone in a system that offers no postural support, the pressure map would likely show a significant pelvic obliquity. This can help confirm a therapist is choosing the appropriate seating system for the client. An important limitation to note of the pressure mapping system is that it does not show the shearing forces that can occur and cause skin breakdown. This makes it imperative that the pressure map system is one tool utilized in the clinical decision-making process and is not the only factor in choosing the seating.

In seat cushion trials pressure mapping is used to evaluate for cushion with greatest symmetry and lowest readings across the surface, and in load redistribution pressure mapping is used as a tool for providing biofeedback and education.

Pressure mapping systems may also provide utility in helping wheelchair users visualize trouble spots through the use of color-coded maps the systems provide. Pressure mapping can educate about how readings change with positional changes, help look for lowest readings, and determine which position allows the greatest unloading.

Optimal interpretation of pressure mapping results is important in getting the best results from the equipment. For example, in using pressure mapping as part of a protocol to determine which peak pressures are acceptable—for instance, those at or below 80 mm Hg—one would look for symmetrical readings, with a goal to stay in green/80-100 range at most, but preferably 10-80 range (blue).

In assuring pressure mapping results are interpreted uniformly among clinicians, there is no formal training. However, there is education provided about symmetry, education of the patient, and how to maintain lowest possible readings and work on co-treat with other members of the team and seating specialists.

Educating the Client

Several different avenues can be used to educate clients about the ways to maintain skin integrity. For example, at Magee, clients receive one-to-one education sessions within their normal PT/OT times, as well as additional educational groups dedicated to the topics of skin integrity and pressure injury prevention. The seating clinic also attends weekly skin integrity rounds with a wound, ostomy, continence nurse (WOCN) and registered nurse (RN) to help build the bridge between nursing and their functional mobility/recovery to ensure that what is being found medically is being addressed on the therapy side. Clients are taught how to maintain their cushion, whether it is filled with air or gel, and what to do if they think the integrity of the cushion has been compromised.

With special regard to temperature and moisture, microclimate is also an important topic on which to educate clients. Many of the clients seen at Magee may experience neurogenic bowel and bladder, and at times will experience incontinence. Also, decreased ability for the body to regulate temperature, especially after spinal cord injury, contribute to tissue injury and pressure sores, if not properly managed. Educating the client to advocate for themselves, which includes directing their care for clean-up status post bowel or bladder incontinence, as well as wearing moisture wicking clothing and always utilizing their cushion covers, can prevent the development of pressure injuries from a less than ideal microclimate.³

Pressure Mitigation and Shear Force

As mentioned earlier, an important intervention in preventing pressure injury is the selection of an appropriate wheelchair cushion. This choice is especially crucial for individuals with significantly limited mobility, sensory impairment, or an inability to shift their weight or reposition effectively. There are several factors to consider when assisting a client in choosing the most appropriate seat. Key considerations include pressure management, shear force reduction, and microclimate management. Considering each of these areas and ranking the importance of each for the specific client can help narrow the options.

Sitting pressure is a vertical force that causes tissue deformation and capillary collapse, local ischemia, edema, and eventually, tissue necrosis. Cushions can mitigate pressure forces and tissue deformation in two main ways. The majority of cushions utilize the concept of immersion and envelopment. Sitting pressure equals force (the user’s weight) over area (the total amount of weight-bearing area). The greater the amount of surface contact between the user and the seat, the less the peak areas of pressure and tissue deformation. Immersion refers to how much the user sinks into the cushion, resulting in increased surface area contact. Envelopment refers to how much the cushion conforms to the user’s body shape and anatomy, also increasing surface area contact. In general, thicker cushions allow greater immersion, and softer more pliable materials allow more immersion and envelopment. Properly inflated air cushions and cushions with viscous fluids (gel) offer the greatest immersion and envelopment. These materials allow maximal sitting surface contact to spread pressure forces out and allow accommodation of asymmetries such as a pelvic obliquity that can result in unsafe peak pressure areas.

Properly fitting, contoured viscofoam cushions can also offer immersion and envelopment to a lesser degree. Gel and foam cushions lose their ability to conform over time and with sustained loading. Air cushions maintain their conforming qualities as long as they are inflated properly. This means that either the user or a reliable caregiver must be able to assess and adjust the inflation level as needed. Most of these cushions typically allow for some adjustment to accommodate changes as needed. In cases with severe postural deformity and asymmetry, custom molding may be needed to optimize sitting surface contact. These custom options allow for choice in cushion materials to optimize immersion and envelopment, such as air or viscous fluid inserts and different density foams. Custom molded options offer little ability to adjust and require a higher skill level to fit.

The other concept in pressure mitigation involves offloading of pressure from high risk areas such as the sacrum and ischium to more tolerant areas such as the upper buttocks and lateral and posterior thighs. This is a prosthetic/orthotic concept. These cushions usually have a firm, contoured base to create specific areas of pressure relief and other areas of increased contact. Most involve some degree of customization due to the need for specific fit. This means there is little room for change or ability to adjust. Fitting this type of cushion therefore requires a higher skill level.

Another contributing factor to pressure injury is shear force. Shear is an opposing parallel force created with movement between the user and the support surface. Shear can occur at the deep tissue level and result in tissue damage. Shear forces also increase the ischemic effect of pressure. Shear can occur as a result of postural instability or spasticity, during transfers, and other functional activities when the user is seated in the chair, or with the use of a recline system. In general, air cell cushions provide optimal shear reduction, followed by viscous fluids and then foams.⁴ However, cushion design can impact transfers, especially a lateral transfer, as well as postural stability. Air cell cushions are more dynamic and can result in more shear during transfers and decreased postural stability in sitting. Viscous fluids and foam offer greater postural control. Sometimes a hybrid cushion, such as a contoured foam base with an air cell insert under the sacrum and ischium, can offer a good compromise. Some cushions also offer an option of shear reducing covering material under the high risk areas.

Microclimate

During the cushion selection process, microclimate also must be considered. Increased sitting surface temperature results in increased cellular metabolism and therefore increased ischemic effect of sitting pressure.³ Increased sitting surface moisture causes decreased strength of the outer dermis layer, irritation, and increased shear.³ In other words, increased moisture and temperature significantly increase risk of pressure injury. Cushion designs that optimize air flow can reduce sitting surface temperature and moisture. Air cell cushions and composite materials like honeycomb maximize airflow. Viscous fluids and foams tend to retain heat and moisture. These materials are also affected by temperature in terms of their pressure-relieving capabilities. At high temperatures, such as in a car trunk on a hot day, they can soften and bottom out. At low temperatures, they can harden. Custom molded seats that optimize sitting surface contact also result in increased temperatures. These can be modified by adding ventilation holes to increase airflow. Some seats offer spacer fabric cover options to improve ventilation.

Managing Considerations

Prioritizing all of these factors in terms of each client’s pressure injury risk is the key to choosing the best seat cushion. An air cell cushion may offer the best pressure and shear relief but not enough postural support, or the client may not be able to maintain it properly. A gel cushion may offer the best postural control but cause too much heat and moisture buildup. It is also important to remember that the cushion cover is an important part of the sitting interface. It must contour with the cushion if immersion and envelopment is a goal for pressure relief. A thicker cover like Naugahyde or an incontinence cover will result in hammocking and prevent the user from sinking into the cushion. Placing an incontinence pad or lift sling under the client will also eliminate the protective benefits of the cushion.

The ultimate goal of Magee’s Wheelchair Seating Clinic is to prevent harm to the patient. By recognizing the risk factors and taking into consideration education, proper seating selection, and mitigation of pressure and shear forces, one can improve the quality of life and decrease the possibility of pressure injuries. RM

Rosemarie Battiato, PT, MPT, is the vice president, outpatient strategy, development & services at Magee Rehabilitation Hospital in Philadelphia. Battiato has been at Magee for 25 years and holds a Master’s in Physical Therapy from Temple University. She oversees the Outpatient Therapy Sites and the Health and Wellness Center at Magee. She has also served as instructor for physical therapy programs.

Caitlin Corbin, PT, DPT, NCS, is a senior physical therapist at Magee Rehabilitation Hospital in Philadelphia. Corbin has been at Magee for more than 6 years and has a Doctorate from Widener University in Chester, Pa. She is a Board Certified Neurological Clinical Specialist who specializes in spinal cord injury and stroke as well as in the inpatient seating clinic.

Jillian Kenderish, MOTR/L, is an advanced clinician occupational therapist in the Inpatient Seating Clinic at Magee Rehabilitation Hospital in Philadelphia. She has been working at Magee for more than 10 years. She received her Bachelor’s Degree in Health Science and Master’s Degree in Occupational Therapy from the University of the Sciences in Philadelphia in 2006. Jillian specializes in the treatment of spinal cord injury and is currently involved in research projects and the NeuroRecovery Network.

Linda Lantieri, MPT, ATP, is a physical therapist in the Inpatient Seating Clinic at Magee Rehabilitation Hospital in Philadelphia. She has been at Magee more than 20 years. She has a Master’s in Physical Therapy from Temple University and received an Assistive Technology Professional certification from RESNA in 2008. She specializes in seating and wheeled mobility. For more information, contact [email protected].

References

1. NPUAP Pressure Injury Stages. Available at: http://www.npuap.org/resources/educational-and-clinical-resources/npuap-pressure-injury-stages/. Accessed December 14, 2016.

2. Regan MA, Teasell RW, Wolfe DL, et al. A systematic review of therapeutic interventions for pressure ulcers after spinal cord injury. Arch Phys Med Rehabil. 2009;90(2):213-231.

3. International review: Pressure ulcer prevention: pressure, shear, friction and microclimate in context. A consensus document. Available at: http://www.woundsinternational.com/consensus-documents/view/international-review-pressure-ulcer-prevention-pressure-shear-friction-and-microclimate-in-context-1. Accessed December 14, 2016.

4. Akins JS, Karg PE, Brienza DM. Interface shear and pressure characteristics of wheelchair seat cushions. J Rehab Res Dev. 2011;48(3):225-234