I was recently asked these questions in preparation for contribution to a magazine article. As I thought about the answers, I realized that I get asked these questions a lot in my educational events. I am sharing the questions as well as my answers here in the hope to get some comments, thoughts, questions from interested readers.
QUESTIONS: Provided by Magazine Editor:
ANSWERS: Provided by Sharon Pratt, PT. Seating Solutions LLC
1) In brief, what are the main tasks a wheelchair seat cushion should accomplish for a wheelchair user?
- The primary four functions of a wheelchair seat cushion are as follow
- Preserve skin integrity
- Accommodate and/or correct dysfunctional postural alignment
- Optimize functional stability
- Facilitate function from a mobility and physiological perspective
2) How does a high-quality, properly fitted seat cushion impact a client’s clinical condition, skin health, comfort and daily functionality?
- I consider my job as “taking the work out of sitting for my clients” In doing so, each time I am involved with a wheelchair / seating prescription, I like to envision the “sitting footprint” of the client. The seat support is a critical component of the Inferior seating support surface (Inferior sitting footprint). I personally like to think of optimizing the clients sitting “footprint” every time I prescribe a seating system. The seat cushion is of course just one critical component of this – another critical inferior support surface is the foot support. It should be noted that the seat support can’t provide a successful outcome in isolation. Other components, such as a back support for example, are also necessary to consider in the big picture.
- When a client is fitted correctly for their wheelchair seat cushion, they should have the predetermined goals in the areas of skin integrity preservation, positioning, stability and function satisfied with positive outcomes which overall should be clearly measurable in terms of sitting tolerance for example. Some clinicians choose to use interface pressure measurement as a tool to assist with measuring outcomes. The number one indictor for success can often be the “ lack of skin integrity issues”.
3) What signs of wear should a provider or clinician looks for when inspecting a seat cushion?
- The client, or provider or clinician should check regularly for signs such as
- Foam compression sets that have a negative impact on the client, for example leaving the client without the necessary “cushioning effect”
- Holes or punctures in cells or compartments that contain fluid/air
- Migration or loss of fluid/air beneath the areas of the pelvis needing greatest protection – for example beneath the Ischial tuberosities.
- Tears in the cover that was designed for that particular cushion
4) What are the signs that a seat cushion should be serviced/replaced?
- Any of the above
5) Cover: What tasks should a seat cushion cover accomplish?
The cushion cover should at a minimum;
- Be stretchy enough to allow optimal immersion of the buttocks into the cushion material without hammocking and negating the benefits of the prescribed cushion materials
- Help manage the negative impact of moisture and heat on the clients skin (microclimatic features)
- Protect the cushion material
- Provide easy removal, washing and drying
6) What role does it play in the overall function of a seat cushion?
- The cover can be instrumental to the success of the cushion performance in terms of posture, skin and function management. For this reason as well as for the purposes outlined above, it is extremely important that the cover that was designed for use with the cushion is in fact the one that is always used.
7) What signs should clinicians and providers look for when assessing whether a seat cushion cover should be replaced with a new one?
- The wheelchair user, clinician and supplier should be vigilant for the following signs of cover wear and tear
- Tears in the fabric
- Broken zippers
- Hammocking perhaps due to shrinkage
- Missing components that may have been built into the cover for the purposes of postural management or skin protection for example fluid pads / foam inserts etc.
8) Base: What is the job of the seat cushion’s base — the part of the cushion nearest the seat of the wheelchair?
- The job of the cushions base where there is a visible or palpable structural base is typically to;
- Provide a stable base of support
- Provide a surface for attaching positioning components
9) What kinds of materials are typically used for a cushion base, and why?
- Typically the bases that are intended to provide postural stability are made of some type of foam.
- Why? Because foam depending on the type can be of varying firmness, can be open or closed cell structure leading some variations to have the potential for cutting/carving and/or added to…
10) Middle/Top Layers: What are the purposes of the seat cushion’s middle/top layers, which are on top of the seat cushion’s base? What purposes do cutouts or indentations in foam potentially serve? Many different types of materials — including foams of varying thicknesses and densities, gel inserts, etc. — are used in this area of the cushion. What do these different media accomplish?
- The purposes of the seat cushion’s middle/top layers are many.
- In consideration of product design and materials used, we have many factors to consider mostly depending upon the clinical goals. If for example, lateral stability is one of the goals for the client, a cushion may be selected for trial that is designed such that the ischials can sink into the materials at least 2” without bottoming out and the precontouring, if it exists, needs to respect the anatomical dimensions of the trochanters and femoral loading area.
- The cover and the materials beneath the cover need to work in harmony creating minimal tension so as to allow this optimal immersion of the ischials.
- If using a fluid material beneath the pelvis, segmentation becomes an important factor. This may reduce the flow of the fluid from one side to another, enhancing stability.
- If skin protection is an identified goal, we need to think about selecting materials that allow immersion without bottoming out as well as optimal envelopment with the goal of pressure redistribution. This means that we want the ischials to sink in while providing an optimal shape relationship with the clients’ unique buttocks and femoral shape so as we have an overall reduction in the magnitude of the pressure.
- A desirable shape relationship can be achieved with fluids for example that have in the design of the container low surface tension and a volume that permits the appropriate depth of immersion.
- Others use the intimacy of custom molding/shaping to achieve this intimate shape relationship.
In summary I would like to share a check list that I use to help me look at all cushions with a critical eye…
- Cover: How stretchable is it? How easy is it to get on and off for laundering?
- Material inside the cover… what exactly is it? How does it behave?
- What’s the immersion and envelopment possibility?Why does this matter?
- Is the cushion customizable for unique positioning needs?
- Is there adjustability for future changes?
- What has been provided to manage potential shear forces?
- What microbial factors are in place– How is heat and moisture managed?
- What is the overall weight?
- How will this cushion effect overall seated height when loaded and in use?
- What’s the anticipated durability?