Life on Wheels (57 page)

When you operate a chair with rearwheel drive, you feel as though you are being pushed forward. There is a greater sense of control over the chair, but rearwheel drive doesn’t afford as much agility.

Tipping is also a concern with rearwheel drive. You may need to use anti-tippers with a rearwheel drive chair, since it’s possible for the casters in front to be lifted off the surface by the power and weight of the drive wheels in back when you accelerate the chair. (Anti-tippers are optional small wheels that attach to the chair frame at the rear and float a few inches above the ground. If the chair begins to tip backward, the anti-tippers touch down and stabilize the chair.)

If the rearwheel drive mechanism extends out of the rear of the chair and is low to the ground, you might have the opposite problem—not being able to tip back enough. This could limit your ability to climb over an obstacle or negotiate a ramp or curb cut.

The mid-wheel drive design uses six wheels altogether: two casters in the rear, the two drive wheels, and two more caster-size wheels in the front that are not in continual contact with the ground but are there to help prevent forward tipping. These front casters are usually spring loaded and adjustable. The main advantage of mid-wheel drive is its tight turning radius; it can almost turn in place, making it helpful for people who must navigate small spaces at home or be able to turn around inside a van.

Mid-wheel drive helps to improve traction because more body weight is over the drive wheels, but forward tipping is a concern. Newer models have each pair of front and rear casters in contact with the ground, adjusting to the terrain with shock absorbers. They have worked to optimize stability, but, necessarily, mid-wheel drive chairs are prone to some degree of forward tipping if the chair or your torso leans forward enough. Sudden stops or going down ramps are more likely to bring the front wheels in contact with the ground. Mid-wheel drives should only be used by people with good upper body balance.

Mid-wheel drive chairs do best on firm surfaces. To use them on rough terrain, the front wheels need to be raised and then more rocking occurs.

Whichever placement of wheel drive you select, there will be a range of wheel sizes from which to choose. The advantage of larger wheels is that they will enable you to drive more easily over changes in grade, possibly even small curbs. The disadvantage is that larger wheels add width to your chair. Use of independent suspension—which allows each wheel to shift upward separately with a change in surface—can make up for the loss of maneuverability in a chair with smaller wheels.

Power chair controls are available in a number of designs, allowing for varying degrees of customization and programming. The most common power chair control is a joystick device, mounted on the armrest. The joystick should be positioned so that it can be comfortably reached by your dominant hand while you are sitting in a well-supported, stable upright posture with your shoulders relaxed. Improper positioning of the joystick would force you to compromise your posture in order to put your body in the right orientation to the control. If the joystick is not accurately positioned, using the joystick can strain your hand, arm, shoulder, and back. If you need to sit close to a desk, you will need a joystick control that is able to swing away to the side. Not all joysticks are designed to do this.

For those unable to use a joystick, several other kinds of controls are available:

Breath controls (sometimes called sip-and-puff) respond to an in or out breath, as if you were sucking on or blowing into a straw.

Chin controls use a small rubber cup placed just below the chin. A chin control works essentially the same way as a joystick.

Head controls employ head movements to the back and side, with nothing obstructing the face.

The settings of your control are crucial, and you will need to work with a competent technician who understands your activities and needs. If you set too slow a deceleration rate, for example, but don’t have sufficient dexterity or skill level, you might find yourself running into your furniture a lot because the chair keeps rolling once you have let go of the joystick.

Safety should be the most important consideration when determining maximum speed. What will happen if you are going fast and a dog or a child suddenly steps out in front of you? A sudden stop might throw you out of your chair if you do not have sufficient upper body balance or are riding without the use of restraints. You might also lose your grasp of the controller in such a situation. Both maximum speed and stopping distance (deceleration) can be programmed in modern controllers, and you would be well advised to err on the side of your own safety—as well as that of any being or anything that might accidentally get in your way. Some of the more sophisticated controllers even allow an automatic acceleration adjustment when you are making a turn.

For use indoors, a maximum speed of five miles per hour is a recommended standard. When you are inside, moving in smaller spaces, a slow speed can feel fast. Traveling the short distance from your desk at work to the restroom, or from your living room to your kitchen, seems to go quickly even though you may actually be moving slowly.

A speed that is comfortable inside feels extremely slow once you are out on the open road. Outside, you usually travel farther, and you are more conscious of how long it takes to reach your destination. Traveling from your home to the corner grocery store four blocks away would seem like an eternity using the same speed you were using inside your home.

Yet, outside, you might be with another person who walks. Walking speed always seems slow to a wheelchair rider, yet you don’t want to make your companions run to keep up with you. Average walking speed is three miles per hour, whereas a moderate running pace is eight miles per hour, numbers you can take into account when choosing your chair. Some chairs are capable of traveling as fast as eight miles per hour.

User definition of speed is now typical of power chairs and scooters. A common feature of modern power controls is a switch that lets you alternate between two programs so you can have a maximum indoor speed and a higher maximum outdoor speed. Another approach is a knob that allows you to adjust maximum speed. The amount of force you apply to a joystick also controls your speed, just as with the accelerator pedal on a car.

Although your wheelchair and cushion are separate purchases, which chair you choose—and the specifications when ordering it—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 drive the chair safely.

Cushions come in various depths and sizes, which need to be accounted for in the size of your wheelchair frame. The 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. You need to decide which cushion is best for you before you can make a final decision about which chair is best. You must know the depth of the cushion before you can specify the exact dimensions of your chair.

A critical function of the wheelchair cushion for those with paralysis 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 conditions—circulation is limited further by the loss of muscle that once served as a sort of natural cushion. An additional risk of sitting is shear force, as we tend to slide forward on 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.

“Pressure-mapping” technology has become widespread in rehabilitation centers, now that it is extremely affordable and runs with a laptop computer. It is a simple mat that is laid over your cushion—or one being considered for you—that produces an image on the computer screen detailing where the pressure points are located and how substantial they are. Using this extremely powerful tool, the therapist doing the fitting can ensure the correct cushion and chair configuration, evenly spreading pressure across your vulnerable points.

The other crucial role of the cushion is postural stability. Even if you are able to walk or are an amputee with sufficient built-in ischial cushioning, the right cushion helps to position and stabilize 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 puts it well:

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, and contributing to your stability. The new foams can adapt to any shape and still provide even support, spreading pressure across the sitting surface. Different types of foam 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. It simply means you must be more earnest about checking on the condition of the cushion, and pay attention to your body if you feel some pressure or notice your posture has changed. 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.