| August, 2001 |
|
Driving with Your Head: head controlled power wheelchair access methods
May 7, 2001
by Michelle L. Lange, OTR, ABDA, OTR
There are several available head controlled power wheelchair access methods. What are they and how do you decide which is best for a client?
Here are some options and features:
Proportional Head Controls have been around for a long time and are available through the major power wheelchair manufacturers. These were also known as RIM controls in the past. Basically, a head rest is mounted to a joystick placed behind the head. Pushing back on the headrest moves the wheelchair forward and turning the head to the side moves the wheelchair in that direction. A reset switch toggles between the forward and reverse functions. This system is designed for a client with good head control.
Pros: the client has full 360 degree control, using the reset switch. The client also has proportional control, meaning that the further the joystick is deflected, the faster the wheelchair goes.
Cons: If the client tends to forcefully extend the neck with increased muscle tone or startle, this access method is unsafe. I have found that in clients with increased muscle tone, sustaining pressure on the headrest to move the wheelchair forward further increased tone. This made stopping the wheelchair more difficult and led to unsafe situations. The Proportional Head Control is also a rather unstable access method, as the whole headrest moves dynamically with the client's head. For clients who already lack stability, this can make access more difficult. This headrest is designed only for driving, not for providing head support, also due to this instability. Finally, if the client does not have refined head control, their speed may be erratic.
Electronic Head Array
This is a three piece headrest with proximity switches built into each pad. By being in proximity to the switch imbedded in the center pad, the client moves the wheelchair forward. Activating the side pads moves the chair in the corresponding direction. A reset switch toggles between the forward and reverse functions. These are made by Adaptive Switch Laboratories (ASL) and Switch It. This system is designed for a client with fair to good head control.
Pros: The proximity switches do not require any pressure to activate, which usually prevents muscle tone from increasing further. Personally, I have worked with a number of clients who were unable to control the Proportional Head Control who are able to use this access method efficiently. The headrest is also stable, which can be helpful for clients requiring this stability and allows the head array to be used as a headrest (though only when the chair is not in drive mode!)
Cons: This head array does not offer full directional control, but rather 4 directional controls (forward, reverse, left and right). By activating the rear pad and a side pad simultaneously, diagonal control is achieved. Proportional speed control is also unavailable. If the client tends to forcefully extend the neck with increased muscle tone or startle, this access method is unsafe, as the client may not be able to stop. The ASL version has a built-in stop switch to stop the wheelchair if excessive force is exerted on the center pad, but I have found this unreliable.
Magitek
The Lautzenhiser Drive Control is a small, proportional sensor that can be worn on the top of the head (i.e. on a headband) or placed elsewhere on the body. By moving the sensor out of it's neutral zone, the wheelchair moves. The distance and direction the sensor is moved out of it's neutral zone determines the direction and speed of the wheelchair. This system is designed for a client with good head control.
Pros: full directional and proportional speed control. The sensor can be calibrated for an individual, allowing the client to utilize available range of motion, even if this range is asymmetrical. No reset switch is required for reverse.
Cons: The client must be able to quickly and accurately return to the neutral zone to stop the power wheelchair. This neutral zone can be adjusted, but may still be difficult for some clients to find, especially as there is no physical template. This access method is rather abstract, which can be challenging for clients with cognitive limitations. Reverse is controlled by tilting the head back, which can elicit tonal changes or reflexes in some clients. The system automatically recalibrates each time the wheelchair is turned on. This can be a pro or a con. If the client happens to be looking down when the system is turned on, the control is calibrated with the head in a downward position. This system is not appropriate for a client who needs the support of a headrest.
PeachTree Proportional Head Control
PeachTree is a very high tech access method for a head control that has been around for a long time. This head control reads the head's movements within a radio field and translates those movements into proportional control of the wheelchair. This system is designed for a client with good head control.
Pros: full directional and proportional speed control. The system can be calibrated for an individual, allowing the client to utilize available range of motion, even if this range is asymmetrical. No reset switch is required for reverse.
Cons: This access method is rather abstract, which can be challenging for clients with cognitive limitations. Reverse is controlled by tilting the head back, which can elicit tonal changes or reflexes in some clients. This system is not appropriate for a client who needs the support of a headrest.
Chin control
Pros: full directional and proportional speed control, depending on client's range and strength. No reset switch is needed.
Cons: some clients experience cervical or jaw pain with long term use of a chin joystick. Chin drives can be difficult to use over rough terrain and may even get away from the driver. The joystick is difficult to stabilize against, as it is moveable. This system is generally not appropriate for a client who needs the support of a headrest.
Other switch arrays
Any combination of mechanical or electrical switches can be placed around the head. In general, the client needs at least 3 switches for forward and directional control. A reset can be added to toggle forward and reverse or an actual reverse switch can be added. I often place switches on either side of the head for directional control and find another site for forward control. This is helpful for clients who have a lot of extensor tone and may get stuck on a switch placed behind the head.
Many head controlled access methods are available for power wheelchairs. These are helpful for clients who have fair to good head control and perhaps limited control elsewhere. Many of these products were designed for clients who are paralyzed below the neck, however these access methods are also helpful for many clients with increased muscle tone. Often, increased muscle tone effects the extremities more so than the trunk and neck. A client with very little volitional control of the arms or legs may have fairly isolated control of the head.
Michelle L. Lange is Clinical Director of The Assistive Technology Partners of The Children's Hospital, 1245 E. Colfax Avenue, Suite 200, Denver, Colorado 80218, 303-315-1289,
D.
(reprinted with permission by the Author and www.rehabcentral.com)
(http://www.rehabcentral.com/art-adee.cfm?artID=9062)
Not everyone would consider chin control as head control, but a chin mounted joystick requires head movement. The chin sits in a cup shaped joystick handle and is usually controlled by neck flexion, extension and rotation. This system is designed for a client with good head control.
Lange.Michelle@tchden.org
