Last month, we focused on materials commonly used in wheelchair cushions. This month, let’s look at the different types of cushion covers and how the type of cushion cover used may effect skin protection. Cushion covers?! Are they really that important? Well, in a word – yes!
When a manufacturer designs a wheelchair cushion, the cover is integral to the design of the overall cushion. The design and materials used in the cushion cover work in conjunction with the design and materials of the cushion to help achieve seating goals. That is why a cushion cover should not be “swapped” for a cover from a different cushion when one cover is being laundered. It is also the reason why clients should not sit on a cushion base without any cover.
There are many different types of cushion covers. Traditional cushion cover options include: stretch, incontinent and microclimatic. In addition, there are covers that are made with materials that are new to off-the-shelf seating. One material is a stretchable polyurethane fabric with water resistant properties that previously was used only in custom seating. Another material includes silver ions to provide an anti-microbial option.
In addition to helping keep the cushion underneath clean, the cushion cover can have an impact on skin protection for a person by affecting the amount of air exchange that occurs at the seated surface1. As well, the cushion cover can affect the temperature and the amount of moisture at the seated surface. Recall that heat and moisture are two extrinsic factors associated with pressure sores. In addition, the cushion cover can affect the pressure distribution at the seated interface if the cover does not allow for sufficient immersion to occur due to a potential hammock effect2.
So how can a cushion cover help with air exchange and heat and moisture dissipation? Some cushion covers are designed with a layer of open-cell, reticulated foam sewn into the interior of the cover. The open cells of this layer of foam allow for air exchange and the ability to wick away heat and moisture. In addition, the layer of reticulated foam provides comfort for the client when sitting on the cushion. This is an example of the manufacturer considering the design of the cushion cover in conjunction with the underlying cushion.
Let’s look more closely at each of the different types of cushion covers.
I’m sure we are all familiar with an incontinent cover for a wheelchair cushion. Incontinent covers serve to protect the cushion underneath the cover by providing a barrier to prevent any moisture from seeping into the material below. The moisture remains at the surface of the cushion until the client transfers from the cushion. Maceration (softening and breaking down) of the skin results from prolonged exposure to moisture. Thus, an incontinent cover protects the cushion, but how well does it protect the client from potential skin breakdown if the client remains seated in a moist environment?
If an incontinent cover must be used for the cushion, consider the design of the cover. Will there be too much surface tension in the cover when a person is sitting on the cushion to prevent immersion into the cushion (i.e. a hammock effect)? Or does cushion cover allow immersion into the cushion through a design feature, such as pleats that provide for additional material in the cover to allow immersion to occur?
A stretch cover can be considered a general use cover. A stretch cover allows for four-way stretch, which facilitates immersion into, and envelopment by, the cushion material. If the material under the wheelchair cushion cover can be washed easily, such as with closed cell foam or fluid packs, and if there is only infrequent to occasional incontinence, consider the possibility of opting for a stretch cover (with a replacement cover for use during laundering of the first cover) rather than an incontinent cover.
A microclimatic cover facilitates the transfer of heat and moisture away from the body through a layer of spacer fabric. A microclimatic cover can be compared to technical shirts worn by runners that wick heat and moisture away from the body during strenuous activities.
A wipe able cover also is available in an off-the-shelf cushion. The material is a polyurethane fabric that is resistant to moisture and fluids, yet still has four-way stretch. Again, the stretch permits immersion into the cushion material. The wipe able fabric is advantageous for infection control in facilities in which a cushion will be used by multiple people as the cushion cover can be cleaned easily with a disinfectant agent before use by the next person.
Lastly, there are wheelchair cushion covers that are made from a material that is impregnated with silver ions. The silver is non-toxic and acts as an anti-microbial within the fabric to eliminate bacteria and odours. The material is four-way stretch and allows immersion and envelopment to occur with the cushion, addressing skin protection issues through material design.
One final thought with respect to skin protection and cushion covers is the degree to which the material of the cover can affect shearing forces. Recall that shearing is an extrinsic factor associated with pressure sores. (See the Pressure Sores and Skin Protection article for more information on shearing.) A cushion cover that allows for stretch in the material will have lower shearing forces than a cover made of a stiffer, less giving material.
So you can see that wheelchair cushion covers do more than just help to keep the cushion underneath clean! Cushion covers are an integral part of the product design of a wheelchair cushion. Cushion covers can have an effect on skin protection through their ability to allow air exchange, heat and moisture dissipation, immersion and envelopment, and to minimize shear forces.
- Kurfuerst, S. & Chew, F. (2003). Cushion Conclusions. Rehab Management, 16 (7), 52-56.
- Iizaka, S., Nakagami, G., Urasaki, M., & Sanada, H. (2009). Influence of the “hammock effect” in wheelchair cushion cover on mechanical loading over the ischial tuberosity in an artificial buttocks model. Journal of Tissue Viability, 18, 47-54.