Selecting the Best Wheelchair Cushion
Although your wheelchair and cushion are separate purchases, which chair you choose is significantly affected by the type of cushion you will use. Chair and cushion are a team, each influencing the other. The proper combination of chair and cushion will enable you to sit in a neutral and stable posture and to operate the chair safely. Cushions come in various depths and sizes which need to be accommodated by the size of your wheelchair frame. The actual length of footrests, the height of the chair back, the position of armrests, and other features are influenced by how high or low you will be sitting on a cushion. Clearly, you need to decide which cushion is best for you before you can make a final decision about which chair is best, certainly before you specify the exact dimensions of your chair.
Wheelchair cushion development is quite lively, as designers and engineers continue the quest for the ideal cushion. A number of manufacturers, such as Jay and Roho, exist solely for the design and production of seating and support systems for wheelchairs. Most of the major wheelchair makers, including Everest & Jennings, Invacare/Pindot, and Otto Bock Reha also offer an assortment of cushions. Cushion design is by no means a simple topic, and there are many choices to make as you decide on the right one for you. This chapter discusses the four basic types of cushions--foam, gel, air floatation, and urethane honeycomb--as well as designs and systems for more specialized needs.
Cushion function What kind of cushion you choose will depend on a variety of factors, including how much time you spend in your chair, how much you move around in your chair, and how stable your posture is. One important task of the wheelchair cushion is the prevention of pressure sores. Since, when we sit, only one third of the body's surface is supporting all of its weight, blood flow is restricted. In the presence of muscle atrophy--which is experienced in particular by many people with spinal cord injuries--circulation is limited further by the loss of muscle which once served as a sort of natural cushion. An additional risk of sitting is shear force, as we tend to slide forward in the cushion, causing stress across the surface of the skin. Resulting pressure sores (decubitus ulcers) can be very serious, leading to hospitalization, surgery, and--though rare--even death. The right cushion is a primary tool for maintaining the health of your skin. The other crucial task for a cushion is postural stability. Even if you are able to walk or are an amputee with sufficient built-in cushioning, the right cushion helps to support your spine. If you already have some asymmetry in your body, you need to be supported in a way that will not increase any spinal deformity.
For manual chair users, greater stability in your chair also means you can push the wheels with more confidence and strength. It can't be repeated often enough--posture is key. Bob Hall of New Hall's Wheels puts it well: The wrong seating system leads to poor posture, which leads to physical problems, which leads to becoming more sedentary, which leads to a negative emotional and personal experience. It's a dangerous chain of events. Foam cushions Foam technology has come a long way. No longer just the soft, airy stuff of the past, foam now comes in a range of densities and with varying degrees of "memory," holding its shape as you sit, contributing to your stability. The new foams can adapt to any shape, and still provide even support, spreading pressure across the sitting surface. Different foams are often used in combination, layered for their various properties of softness, even support, and memory. Foam is relatively inexpensive, and it is easy to cut. A therapist can experiment with shapes free of financial risk.
If you have an area of skin that is broken down or on the verge, pressure can easily be reduced by cutting out a portion of the cushion. (You should not do this on your own, though, because only a doctor or therapist can identify the changes in your cushion that will help relieve pressure while still maintaining appropriate support.) On the downside, foam wears out faster than other materials and loses its shape, but because of its lower price, this might not concern you. If you choose a foam cushion, be sure to replace it when its time is up. Old foam that is compressed can allow pressure points to form that can lead to a sore. If you choose a gel or air flotation cushion for daily use, it is a good idea to have a backup foam cushion since gel and air flotation cushions can leak. Gel cushions Gel cushion designs attempt, in effect, to replace the consistency and support of atrophied muscle tissue. Highly engineered gel fluids are placed in pouches and usually attached to a foam base, so that the cushion conforms to the pressures placed on it. As a result, gel cushions provide excellent pressure distribution and are very comfortable. Many gel products also offer supplemental inserts to stabilize your legs.
Your knees might tend to fall together (adduction) or apart (abduction), so such an accessory can help keep your legs straight which also aids your overall posture. Unfortunately, gel cushions are much heavier than other types, which can cancel out some of the benefits of your lightweight wheelchair. Gel suppliers such as Jay and Flofit offer lighter, active-use designs, but these might not be appropriate for you if you are unable to do your own pressure-relief lifts. If you bounce up and down curbs, or commonly experience similar impact in your chair, a gel cushion might not be ideal. When you sit in a gel cushion, there is no further "cushiness" to absorb impact, a concept known as impact loading. Other cushion types are better able to absorb impact. Another drawback to gel cushions is the possibility of them "bottoming-out" as the gel is pushed aside by your weight. You can help prevent this distribution problem by kneading your gel cushion once a day, keeping the fluids loose and spread evenly. Look for a design that divides the gel portion into several sections so that all of the gel cannot push to the sides.