Although your wheelchair and cushion are separate purchases, which chair you choose is significantly affected by
type of cushion you will use. Chair and cushion are a team, each influencing other. The proper combination of chair and cushion will enable you to sit in a neutral and stable posture and to operate chair safely. Cushions come in various depths and sizes which need to be accommodated by size of your wheelchair frame. The actual length of footrests, height of chair back, 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 exact dimensions of your chair.
Wheelchair cushion development is quite lively, as designers and engineers continue quest for ideal cushion. A number of manufacturers, such as Jay and Roho, exist solely for design and production of seating and support systems for wheelchairs. Most of 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 right one for you. This chapter discusses 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 wheelchair cushion is prevention of pressure sores. Since, when we sit, only one third of body's surface is supporting all of its weight, blood flow is restricted. In presence of muscle atrophy--which is experienced in particular by many people with spinal cord injuries--circulation is limited further by 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 cushion, causing stress across surface of 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 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, 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 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 soft, airy stuff of 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 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 verge, pressure can easily be reduced by cutting out a portion of cushion. (You should not do this on your own, though, because only a doctor or therapist can identify changes in your cushion that will help relieve pressure while still maintaining appropriate support.)
On 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 consistency and support of atrophied muscle tissue. Highly engineered gel fluids are placed in pouches and usually attached to a foam base, so that cushion conforms to 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 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 possibility of them "bottoming-out" as gel is pushed aside by your weight. You can help prevent this distribution problem by kneading your gel cushion once a day, keeping fluids loose and spread evenly. Look for a design that divides gel portion into several sections so that all of gel cannot push to sides.
There is also chance of gel leaking. While cushions arrive with patching kits, patches are ineffective when breach is at a seam, which is often case. A leak might be very minor, or it could be an extremely messy affair.
Air or dry floatation cushions Air floatation cushions support body entirely on air. A typical example is Roho cushion, designed with a group of small, interconnected rubber balloons arranged in rows. Pressure is balanced by air shifting out to surrounding balloons, spreading pressure evenly against your skin. The whole system is closed so air floatation cushions can't bottom out way gel cushions can.
