An introduction to programming power wheelchairs

Power wheelchairs (PWCs) come in many shapes and sizes, from small foldable devices to standing devices. If you are newer to prescribing complex PWCs, programming may not be something you have thought much about, or even know what it could be. Drive wheel configurations, power seat functions, and even suspension are often easier to see, understand and apply to the user you are working with. Programming unfortunately can then become almost an afterthought, or an ‘if I have time’ plan at delivery. The potential for programming is huge in complex PWCs, and so is the functional impact it can have for a user. 

Here we will explore some of the possibilities of programming, and our upcoming webinar in June will take this a step further as it explores the impact programming can have on function and how programming can be completed. The programmability and ease of programming does vary significantly across PWCs with more basic models offering little to no programmability, and high-end complex PWCs offering numerous options. Therefore, knowing what programming may be essential to the user you are working with may also influence the PWC models worth trialling.

June webinar registration: https://attendee.gotowebinar.com/register/5045105144510555486?source=NZ+Other  

Why program?

How a PWC is programmed can be a defining experience for a user during a trial. If you have had users say things like – “it is too fast”, “it is too sensitive”, “it doesn’t go where I want it to” – these could all be due to the programming rather than the PWC itself. Sadly, it may mean that a PWC is ruled out as a solution based only on its speed and responsiveness, both which could have potentially been easily adjusted to meet the user’s needs. Before programming changes, the user should have an appropriate seating system that provides a stable and functional base of support. 

Let’s say you had a user with Parkinson’s disease as well as anxiety who experiences resting tremors, causing you to be considering their suitability for a PWC. An alternate joystick handle (see right) may provide additional control but will not negate the challenge of resting tremors unintentionally activating the PWC. Utilising and adjusting the tremor dampening and/ or deadband zone options would result in the PWC not activating with the smaller joystick deviation caused by tremors. Further, the acceleration could be reduced so that the PWC responds slower to that activation, allowing more cognitive processing time and postural stability, which could be less anxiety provoking.

Customisation may also be a consideration such as individualised wedges on the footplate. Supporting the foot when there is limited reducibility of deviation, can reduce the risk of further postural deformity. Additional supports on the footplate may need to be considered to assist in maintaining appropriate alignment. Think about the points of control and opposite and equal forces and how this can be achieved.

Programming is often an essential component for users such as:

• Users who need specific positions in their PWC to efficiently and consistently go about their daily activities
• Users who apply significant force through the joystick, perhaps requiring multiple repairs or struggle with controlling joystick deflection direction
• Users who have difficulty physically deflecting the joystick, or who may get fatigued
• Users who may unintentionally deviate the joystick, such as tremors
• Users who require a very responsive PWC for immediate feedback
• Users who require a slower acceleration due to cognitive processing, facilitating learning, or to assist in maintaining their physical position
• Users with multiple power seat functions, or who may need additional prompts to the icons
• Users whose function or weight is expected to change over time, and may require alternate access, controls or settings
• Users with an additional attendant control, or who mount the controller in different orientations
• Users who mobilising their PWC in different environments, requiring different speed, torque and acceleration settings between these environments

What can be programmed? 

Please note that options discussed are based off Permobil PWCs, including Power Platform. Different models and manufacturers may or may not offer the same options. 

Joystick/ controller: 

Changing how quickly the PWC accelerates and drives when the joystick is deflected, as well as decelerates once contact is removed.  

• Changing the distance of joystick deflection required to elicit PWC movement, known as the deadband or neutral zone. 
• Tremor dampening is another option to reduce unintentional PWC movement from joystick activation.
• Changing the direction the joystick deflection moves the PWC, which can be beneficial if the controller needs to be rotated, or if it is easier to pull back than push forward, for example.
• Changing to a joystick which takes greater, or reduced force to move it from the centre. 

Attendant control: Up to the same options as the main control. 

Profiles: A profile remembers parameters such as ranges of speed, acceleration and power settings. Once a profile is created, speed can still be adjusted on the controller (within the parameters of that specific profile), but other settings such as acceleration, torque and stopping speed cannot. Created profiles can be accessed through the controller. Examples could be: 

• An indoor profile may be set to have a slower maximum speed and slower acceleration. This could make it easier to move through tighter spaces.
• An outdoor profile could have a range with a higher minimum speed than indoor to the maximum speed, increased acceleration time and increased torque. This makes it quicker and more efficient when moving in larger spaces and mobilising over uneven surfaces.
• Labelling a profile such as ‘indoor, ‘outdoor’, ‘transport’ or ‘slow’ could also make it easier to understand how the profile may perform.

Memory positioning: Options are dependent on the power actuator(s) (or which power seat functions) are on the PWC.  

• When a created memory position is selected, all the relevant actuators will move at the same time to reach a chosen position. Some can be made to all start and finish together.
• These can be individually named to make it easier to understand how the PWC will move, for example ‘drive’, ‘relax’, ‘pressure redistributing’, or ‘up’ rather than ‘elevate’.
• These can be accessed through the control module or a separate switchbox.

Independent Repositioning Mode: Specifies an order for power seat functions, often tilt, then elevating leg supports, then recline. Reduces user displacement compared with a memory position. 

Latching: This is when one input (such as pressing a button) creates a complete action from the PWC, rather than requiring continual input (such as holding a button and the PWC moves until you let go or the action is finished). Examples include: 

• Creating a latched memory position of PSF: When that feature is selected, the actuator(s) will continually move to the end of that created position or until the user pulls back on the joystick to cancel the sequence.
• Consider whether an emergency stop switch may be needed if the latching is related to mobilising the PWC. If, for example, the PWC is programmed so one input moves the PWC 3m forward, and then someone walks in their way, the PWC will continue to move the entire 3m unless an emergency stop option is included and selected.

Assigning buttons: Tactile buttons on the controller can perform multiple commands each with the input typically being a short or long hold. These could be for a huge variety of options such as a specific PSF, memory position, or light setting.

A switchbox is an additional item which acts like a ‘quick access’ to power seat functions. The order of these can be changed depending on preferred functions and visuals.

User weight: The user weight should be programmed into the chair. There are weight ranges used, so if the user has significant weight changes, this needs to be updated.  

The suspension will be set to the relevant user weight range.  

• The weight range selected will determine: 
  • at what PSF degree the maximum speed will be reduced (yellow icon)
  • at what PSF degree the PWC cannot be driven (red icon)
• Higher weight ranges may reduce PSF ranges and/ or speeds to maintain the base’s stability. 

How does programming occur? 

Historically, a technician or dealer was typically required. They would have access to programming software from the manufacturer on a device, which then required a dongle (see image right) to physically connect the device to the relevant PWC. Once connected, changes could be made to the listed options.  

It can be challenging especially for therapists to understand the software without further training due to the software layout and unfamiliar terminology. The technician or dealer would often have the responsibility of explaining the different programming options available to the therapist and user.

More recently, a completely wireless programming tool has become available allowing all programming to be completed through an app. The app also allows for the changes to be made from either the device itself, mirroring the degrees of the power seat function(s) as it is, or through graphics or inputted degrees on the app, which then will change the range on the PWC.  

The app graphics and design aids in simplifying the options available without limiting them. This may assist therapists and users to have greater understanding and therefore involvement in programming a PWC. 

Please reach out to our team if you have any questions. We hope to see you at our webinar on the 13^th June where the functional benefits of programming will be explored. Please register here: https://attendee.gotowebinar.com/register/5045105144510555486?source=NZ+Other 

Author

Roseanna TegelBHthSc/MOT

Clinical Services Specialist