More Power to You

Today's power chairs offer users with more mobility and access. Photo MGT.

Power chairs can provide functional mobility for many people with disabilities

One of the most misleading descriptions of wheelchair users is the term “confined to a wheelchair.” The mobility device is actually more liberating than confining, allowing people access to independent activities of daily living, including participation in sports and recreation.

People with upper-body strength typically use manual wheelchairs, propelling them by pushing their arms forward as their hands grab the wheel rims. “Power assist” rims have small, powerful motors that when turned on give standard lightweight manual chairs a strong boost, increasing the user’s range, saving personal energy, and decreasing wear and tear on his/her rotator cuffs.

But someone who can’t push at all may require a chair powered by batteries: an electric-powered wheelchair or, for short, power chair.

In his book Wheelchair Selection and Configuration (Demos, 1998), Rory A. Cooper, PhD, says electric-powered wheelchairs were first invented around the turn of the century, with the first U.S. patent approved around 1940. At that time, the designs were impractical, and there was little demand for this type of chair because the prognosis for people with severe disabilities (the individuals who needed them most) was poor.

However, thanks to medical advances during World War II, more people with severe disabilities survived, and emphasis shifted to long-term rehabilitation. A demand for better wheelchairs, especially the power version, resulted.

Early power chairs used starter motors and automobile batteries. They provided limited mobility for some individuals with upper-extremity issues.
Although the number of power chairs increased during the 1960s and 1970s, they were still bulky, inefficient and unreliable. Reliability improved in the 1980s due to use of microprocessors and metal-oxide-semiconductor-field-effect transistors.

The 1990s brought about frame-design changes. Until then, power chairs were basically iterations of manual wheelchairs. Today, manufacturers have developed chairs with many types of features.

In “Power Chair Lingo” (PN May 2009), Cooper; Joseph Olson, MS; and Rosemarie Cooper, MPT, ATP, note that understanding the language of design and how features change performance can aid in obtaining a chair that fully meets a person’s needs. Excerpts follow.

Drive-wheel Location
Placement of the drive wheels — those turned by the power chair’s motors — determines how the chair will steer and handle. A rear-wheel-drive power chair is a traditional approach that provides good directional stability while moving forward. These chairs handle uneven terrain well.

Front-wheel-drive chairs are harder to drive straight, as small sideways disturbances (uneven surfaces, being pushed, hitting an object, initiating a turn) are amplified. With a front-wheel-drive chair, the rear end swings to the side when turning, so it requires some planning to know where the rear of the chair will move to, but it allows for quick turning.

Mid- and center-wheel-drive chairs have six wheels — two casters in the rear, two casters or antitip wheels in the front, and the drive wheels in between. Mid-wheel chairs’ drive wheels are closer to the driver’s center of mass, so the point about which the chair turns nearly coincides with the user’s center. This makes driving the chair intuitive for many people. Some people note that mid-wheel-drive chairs feel like they rock back and forth as speed changes or when on uneven terrain.

A captain’s seat is standard on most low-cost power chairs. These work well for people not at risk for pressure ulcers, those who do not require postural supports, and individuals who can perform independent weight shifts.

Power seat tilt allows users to maintain the same seated posture while rotating the seat to change the body’s angle with respect to gravity. This helps redistribute the pressure on the body.

Backrest recline is another effective means of providing pressure relief. A concern with using recline alone is the risk of shear forces (the body sliding along the seating surface) developing in the tissue of the back and buttocks that could result in pressure ulcers. The best solution is to use seat tilt and recline in conjunction with one another.

Power seat functions are useful for helping relieve or prevent a variety of other conditions as well:

• Repositioning to ease pain
• Controlling spasticity
• Accommodating contractures
• Reducing fatigue
• Simplifying dressing
• Preventing blood pooling in the legs

Seat elevation is an often overlooked feature. The ability to adjust the seat height can make it possible for users to perform many activities independently and/or to reduce the strain on an assistant.

Seating Hardware
Armrests are essential to provide support for the arms, assist with lateral stability, and serve as a location to mount controls. Flip-up armrests are useful, as they needn’t be removed from the chair for transfers or various tasks.
Footrests are also key components.

The two basic categories are single foot-plate and split. Headrests are important for safety when using a power chair as a seat in a motor vehicle, and to support the head during tilt or recline.

Control Interfaces
Primary controls provide the command signals to drive the chair; secondary controls operate things such as the power seat functions, lights, or for programming control settings.
The standard form of primary control interface is the joystick. Many people operate the joystick or alternative control interface by using one of their hands. However, numerous types of interfaces, various body locations, and even physiological signals (electrical signals from muscles or the brain) can control a power chair.

Essential Equipment
Power chairs are essential to providing functional mobility for many people with disabilities. There is nothing easy about selecting, fitting, and tuning these chairs. It takes an expert team to get it right to provide years of safe, functional and worry-free community mobility.

For information about manual-wheelchair use, see “Ready … Set … Push" in the March 2013 issue of PN Magazine.


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