Mobility & Seating


Pressure Mapping Reveals the Complete Picture for Seating and Positioning Solutions

Understanding pressure mapping system components and the hidden insights they provide helps clinicians form a more comprehensive response to seating and mobility needs.

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During an evaluation, the author demonstrates a pressure map image for a patient.

by Kirsten N. Davin, OTD, OTR/L, ATP, SMS

As America ages and the survival rates related to trauma and degenerative diagnoses increase, we, as a country, are seeing more wheelchair users than ever. Recent estimates suggest at least 1 in 250 people currently requires use of a wheelchair on at least a part-time basis.1 The wheelchair industry has experienced unprecedented growth in the last decade, including the development of state of the art equipment and accessories to provide the user with comfort and function never before seen.

Unfortunately, using a wheelchair comes with inherent risks, chief among which is skin breakdown. Populations most at risk are the elderly and, more specifically, nursing home residents and individuals who have experienced spinal cord injury. These populations present with a pressure wound incidence rate of 23% and 60%, respectively.2

Therapists, equipment providers, and end users alike have long known about the benefits of incorporating a pressure mapping analysis into the wheelchair seating assessment, intervention, and daily follow-up, but until recently, pressure mapping systems have been too costly for many facilities, clinics, and end users to implement. Recently, new software developments and mat design have reduced the overall cost, and helped pressure mapping become an option that fits the budget of virtually any facility.

What Is Pressure Mapping?
A pressure mapping system is a combination of a hardware mat and computer software that work together to produce a visual image of the user’s contact area. This color keyed image somewhat resembles Doppler radar, similar to what one may see on the nightly weather broadcast (ie, red equals strong storm and green equals a gentle rain).

The thin pressure mat is placed on top of the user’s seating surface, between the surface and the client, and each sensor within the mat simultaneously takes three pressure readings per second, producing an average of the readings and displaying the mean reading in millimeters of mercury (mm Hg) on the software image display, which will correlate with a color based on the intensity of the pressure being exhibited.

Experts have often debated about the exact pressure readings that are deemed acceptable when pressure mapping a client, and further research is needed to reinforce current theories; in general, most researchers agree that setting a goal of keeping the peak pressures under the client at or below 80 mm Hg, in conjunction with ensuring the wheelchair user is performing adequate pressure shifts, as often as every 8 minutes, will often ensure success in pressure wound prevention. With any type of seating system intervention, it is important to remember, as clinicians, we cannot remove pressure from an individual, as the amount of gravitational force pushing the client into the seat, as well as the amount of mass contained within the client, will remain relatively consistent. However, we can—and must—redistribute that pressure to be successful.

Benefits of Pressure Mapping: Common and Creative
Myriad benefits are associated with pressure mapping, the most common of which is pressure assessment. Through the use of these systems, the therapist, equipment provider, or wheelchair end user can almost instantaneously see the amount of pressure that exists under the user. Mapping can often detect asymmetries, such as pelvic obliquities or rotation, or peak pressure concerns over bony prominences, which are often undetectable by the naked eye. By simply having the patient sit on the mat, the evaluator sees a much clearer picture of problem areas or adjustments that may be necessary to ensure adequate pressure distribution, and an improved client-equipment fit. This information can be used to assess a user’s current seating situation, enhance a letter of medical necessity with images, or develop creative solutions to difficult seating presentations by gaining immediate feedback about the interventions being implemented.

Many clinicians are aware of the aforementioned benefits pressure mapping confers, but are unfamiliar with some outside-the-box applications that can be very useful in the clinic. End users and clinicians alike find pressure mapping extremely useful in conjunction with air cushions to assess a user’s daily proper inflation. By initially overinflating the air cushion, the client will present with poor pressure distribution, as evidenced by the high pressure readings on the software. As the user or clinician opens the external air valve on the air cushion (if it is a single valve option), the client will sink into the air cells, resulting in improved pressure readings on the mapping display.

After the prime inflation levels are reached, the pressure mapping software will show increasingly poor pressure distribution. Through the use of this simple and quick application of pressure mapping, an everyday wheelchair user can routinely check and ensure the air cushion inflation is ideal, and significantly reduce the risk of increased pressures under the contact area.

Air cushions also may decrease shear forces during scooting or transfer, and the integration of an appropriate cover may improve thermal properties of the cushion. In addition to air cushions, other seating components in the mediums of foam and gel can play a key role in optimizing an overall seating and positioning solution. Foam offers the ability to manipulate the cushion and create contours for the bony prominences of the pelvis, while the availability of viscoelastic foam allows for the conduction of heat away from the skin. The introduction of solid and fluid gel cushions can also assist in conducting heat away from the skin while providing a reduction in shear.

Seating components targeting support and comfort also can help complete an overall seating and mobility solution. Such items include armrests available in a range of styles to pull gravity off the arms and shoulders, as well as headrests to cup and support the user’s head. The use of abductors to separate the knees to prevent adduction contractures, and knee adductors to position the knees out of abduction, also can be important to create an optimized solution. Other accessories such as collapsible wheels may prove helpful for patients who travel frequently. These types of wheels are designed to collapse into size that fit in aircraft storage spaces as well as motor vehicles, and may help reduce shoulder strain when lifted into an automobile.

Therapists routinely work with clients who have experienced a stroke or other diagnoses that result in significant loss of sitting balance or righting capabilities. Therapists can easily incorporate pressure mapping into routine neuro-reeducation treatment, and make treatment fun by turning on the center of gravity option on the mapping system and have the client sit on the edge of a mat or a firm surface, with the display in front of them as a mirror image. Assist the client into reaching a neutral position and place a small sticker on the center of gravity indicator on the display screen while the patient remains stabilized in a neutral sitting position. Allow the patient to return to the baseline, asymmetrical position, and encourage the client to pull into neutral and attempt to line up the center of gravity marker on the display with the sticker on the screen, thus encouraging an ideal neutral position. This center of gravity option also can aid in the assessment of drive wheel placement, frame width, seat to floor height, and self-propulsion efficiency.

Limitations of Pressure Mapping
As with any medical device, pressure mapping must be used with caution, and in accordance with physical assessment. It is not designed to be used as a sole form of assessment, but rather to be incorporated into an overall evaluation or assessment protocol. As a clinician, evaluator, or end user, always be sure to palpate the problem areas that are visualized on the pressure mapping system. Use a hands-on approach and verify that what is being seen on the screen is valid, and not a rolled sensor, undergarment, keys in a pocket, or other false positive.

The other notable, longstanding disadvantage associated with pressure mapping has easily been the price of equipment. The multitude of benefits noted above have long been unattainable for many due to prohibitive cost. The current market does offer pressure mapping systems designed to be affordable, however, and these technologies may be found through diligent research on pressure mapping system manufacturers.

Clinical Features and Applications: What Can Pressure Mapping Do for My Client?
Gauge pressure under the client’s contact areas. Clinicians can thoroughly evaluate static or dynamic pressure distribution through the use of pressure mapping, gaining immediate feedback and continual, live updates, including peak pressure measurements and real time graphics.
Measure anatomical landmarks. Linear measurement features on most systems allow the clinician to incorporate precision measurements into the assessment. One can identify the client’s contact area width, the distance between ischial tuberosities to ensure ideal cushion seat well selection, track the size of pressure areas within the seating system, or identify the severity of pelvic rotation via a few simple mouse clicks.
Identify seating concerns easily and quickly. The presence of pelvic obliquities, pelvic rotation, scoliosis, anterior or posterior pelvic tilt, sacral sitting, lordosis, or any number of postural or positioning concerns can be easily identified, even when not readily identifiable by the naked eye. • Record, freeze, save, and print any and all images. Most pressure mapping systems are designed to record up to 10 minutes of video images and take a variety of data snapshots, which is a “must have” for the clinician to incorporate into letters of medical necessity, or for proper assessment of self-propulsion capabilities and settle analysis.
Create custom seating design. For clinicians required to get creative with seating solutions or improve the accuracy of inflation with air cushion use, pressure mapping aids in verifying proper positioning and fine-tuning seating modifications.
Locate a client’s center of gravity. As previously mentioned, the center of gravity feature will clearly show the clinician, in real time, the client’s center of gravity and aids the user in verifying proper positioning during evaluation. This feature can identify discrepancies in drive wheel placement, which affect the client’s ability to successfully self-propel the wheelchair.
Gain approval for equipment through improved documentation. Improve letters of medical necessity with the incorporation of the freeze frame and snapshot options available with many pressure mapping systems. Most systems allow the clinician to print multiple images of the client’s current presentation as well as alternative cushions or seating systems to thoroughly justify to the client’s funding source, the client’s situation, and equipment requirements.
Educate and verify a client’s pressure relief methods. Use pressure mapping to verify a client’s capability to perform manual pressure relief, or the caregiver’s ability to properly position and adjust the seating system. Real time images provide the client with immediate feedback, ideal for use in client education and reassurance.

Leaders in the Industry
More than 450,000 pressure-related wounds are reported annually among wheelchair users and hospitalized patients. When one considers the average cost of hospitalization due to a pressure-related wound or ulcer is $37,800,3 the implementation of a pressure mapping system and the multitude of advantages that come with it in regard to treatment, assessment, and client education are more than worth the capital expenditure. This is especially true in light of the fact that new technologies, and companies, have opened the door for smaller facilities, individual end users, and the cost-conscious consumer.

It is imperative for the facility, clinician, and end user to gain a good understanding of the various pressure mapping systems currently on the market, and research the features and components key to their needs such as pricing, software, and support. RM

Kirsten N. Davin, OTD, OTR/L, ATP, SMS, is an occupational therapist, Assistive Technology Professional, and Seating and Mobility Specialist, who conducts continuing education seminars and lectures nationwide, which she provides both through Cross Country Education as well as on a private basis. She is the owner of a private practice, Escape Mobility Solutions, LLC, headquartered in Pleasant Plains, Ill, and specializes in wheelchair seating, positioning, and assistive technology provision. Davin also practices clinically at Memorial Medical Center in Springfield, Ill, as a staff occupational therapist and is currently on faculty at Rocky Mountain University of Health Professions, in Provo, Utah. For more information, contact RehabEditor@nullallied360.com.