Pushrim Activated Power Assist Wheelchairs - Clinical Benefits and Considerations

Hello all!

This month, let's talk about Pushrim Activated Power Assist Wheelchairs (PAPAWs). Let's focus on the clinical benefits and considerations associated with their use.

Let's begin by defining what a PAPAW is. This is a regular manual wheelchair – either an adjustable folding frame wheelchair or a rigid frame wheelchair – to which motorized wheels are added to provide power to the wheelchair. A PAPAW may be considered to be a hybrid between a manual wheelchair and a power wheelchair¹. A person using a PAPAW continues to hand propel the wheelchair using the pushrims; however, motors in the hubs of the wheels are activated by the force on the pushrims of the wheels. The motors in the hubs of the wheels engage only when there is force directed through the pushrims. In essence, the motors allow for greater distance to be traveled with one push stroke compared to the use of a regular wheelchair.

The power assist wheels can be prescribed either at the time of the original manual wheelchair prescription or as an addition to an existing manual wheelchair. The quick release axles on the power assist wheels allow for the easy exchange between the power assist wheels and regular wheels on the manual wheelchair. Thus, a PAPAW can convert easily back to a manual wheelchair, if required.

The method by which the power assistance is delivered in a power assist wheel varies by manufacturer; nevertheless, PAPAWs have been studied extensively by researchers and reported on in the literature. It should be pointed out that there have been new advances in the technology of the power assist wheels since many of these articles were written, and as such, perhaps even greater clinical benefits may be seen with the use of PAPAWs. For example, there is a PAPAW available that allows a person with hemiplegia to operate the PAPAW using one hand and one foot.

Clinical Benefits

Manual wheelchair propulsion with the upper extremities puts people at risk of repetitive strain injury (RSI) due to the repetitive motions under force. A person is moving not only his/her own body weight, but also the weight of the wheelchair and seating system. PAPAWs provide mechanical efficiency that reduces the risk of RSI. One study found that propelling a PAPAW required one-third less power to propel when compared to subjects' own manual wheelchairs at the same speed and resistance. The study also found that there was an increased mechanical efficiency in propulsion by an average of 80% when using the PAPAW.² Another study found that the use of a PAPAW decreased the upper extremity joint range of motion in shoulder flexion and wrist extension and decreased the frequency of strokes taken when compared to propelling a subject's own manual wheelchair.³ By decreasing the upper extremity range of motion and decreasing the number of strokes required to propel a manual wheelchair, the risk of RSI is reduced.

Studies have also found that the metabolic demands associated with manual propulsion of a wheelchair are decreased when using a PAPAW.^3,4,5 The average heart rate and oxygen consumption was lower for people using a PAPAW than compared to a regular manual wheelchair. For people who fatigue easily, the use of a PAPAW may assist to conserve energy to enable improved function in other areas, such as transfers or leisure activities.

When tested in the community, one study found that the average speed travelled was greater for individuals using a PAPAW versus a person's own manual wheelchair.⁶ This allowed individuals to propel the PAPAW at a "normal walking speed required to safely cross the streets."^{6 (p. 827)}

In addition, the use of a PAPAW has been found to improve a person's ability to climb obstacles compared to manual wheelchair use.⁷ The use of a PAPAW enables an individual to propel over carpets, up steep inclines, and over uneven surfaces, such as grass and gravel, with less effort due to the mechanical advantage provided by the power assist wheels. The chart below demonstrates the power assist that is provided to an individual at different inclines. The blue squares represent the power of force provided by the individual to the power assist pushrims, while the green squares represent the power provided by the power assist wheels. When travelling along a flat surface, less assistance may be required by an individual. More assistance is provided to climb a slight incline and even greater assistance is provided to climb a steep incline. The PAPAW also assists to control the speed going downhill to ensure safety.

Considerations

While there are many clinical benefits of using a PAPAW, there are some considerations that must be taken into account. One consideration is that the overall width of the wheelchair is increased by the addition of power assist wheels as the small motors are located in the hub of the wheels, adding to the width of the manual wheelchair. For some people, this added width may cause accessibility issues in confined spaces when compared to a regular manual wheelchair.

Another consideration is transportability. An advantage of a PAPAW over a power wheelchair is the ability to transport the mobility device without requiring any vehicle modifications. The power assist wheels can be removed from the manual wheelchair and the wheelchair and wheels can be lifted into the vehicle. It should be noted, however, that due to the weight of the wheels (approximately 17 pounds per wheel for one model of PAPAW), some individuals may not be able to lift the power assist wheels into a vehicle independently.⁶

There are many factors to consider when deciding if a PAPAW is an appropriate choice for an individual. Ding et al. (2008) provide an excellent summary:

"When choosing between a PAPAW and a manual wheelchair or a power wheelchair, it is important to consider a user's preference, life style, physical conditions such as the injury level and upper limb strength, and environmental factors such as accessibility conditions at home including steps at entrance, stairs, doorways, and maneuvering spaces, and transportation issues with motor vehicles." ^{(p. 828)}

While the above authors were studying people with tetraplegia, it is important to note that the use of a PAPAW can benefit not only people with tetraplegia, but also people who have an "arm injury, insufficient arm strength or low cardiopulmonary reserves. Also, subjects who have difficulty propelling a wheelchair in a challenging environment can benefit from power-assisted wheelchair use."^{1 (p. 1.)}

References

1. Kloosterman, M.G., Snoek, G., Van der Woude, L.H., Buurke, J.H., & Rietman, J.S. (2012). A systematic review on the pros and cons of using a pushrim-activated power-assisted wheelchair. Clinical Rehabilitation, 0(0), 1-15.
2. Arva, J., Fitzgerald, S.G., Cooper, R.A., & Boninger, M.L. (2001). Mechanical efficiency and user power requirement with a pushrim activated power assisted wheelchair. Medical Engineering and Physics, 23, 699-705.
3. Algood, S.D., Cooper, R.A., Fitzgerald, S.G., Cooper, R., Boninger, M.L. (2004). Impact of a pushrim-activated power assisted wheelchair on the metabolic demands, stroke frequency, and range of motion among subjects with tetraplegia. Archives of Physical Medicine and Rehabilitation, 85, 1865-71.
4. Haubert, L.L., Requejo, P.S., Newsam, C.J., & Mulroy, S.J. (2005). Comparison of energy expenditure and propulsion characteristics in a standard and three pushrim-activated power-assisted wheelchairs. Topics in Spinal Cord Injury Rehabilitation, 11, 64-73.
5. Levy, C.E., Chow, J.W., Tillman, M.D., Hanson, C., Donohue, T., & Mann, W.C., (2004). Variable-ratio pushrim-activated power assist wheelchair eases wheeling over a variety of terrain for elders. Archives of Physical Medicine and Rehabilition, 85, 104-112.
6. Ding, D., Souza, D.D., Cooper, R.A., Fitzgerald, S.G., Kelleher, A., & Boninger, M.L. (2008). A preliminary study on the impact of pushrim-activated power-assist wheelchairs among individuals with tetraplegia. American Journal of Physical Medicine & Rehabilitation, 87, 821-829.
7. Algood, S.D., Cooper, R.A., Fitzgerald, S.G., Cooper, R., & Boninger, M.L. (2005). Effect of a pushrim-activated power-assist wheelchair on the functional capabilities of persons with tetraplegia. Archives of Physical Medicine and Rehabilitation, 86, 380-386.