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Switch Assessment

Switch Assessment
Michelle Lange, OTR, ABDA, ATP/SMS
March 16, 2017


Today we will be covering the topic of switch assessment. There are a number of different switches that are available for our use with clients, particularly to access various assistive technology devices. We are going to talk about access. There are a lot of different access methods that are out there that we can use with our clients so that they can independently control an assistive technology device. If that access method happens to be a switch, we need to determine where to place that switch, so we are going to spend some time on talking about what comprises an ideal switch site. This is part of our assessment process. We are going to look at the hierarchy of available switch sites, and then we are going to look at switch types.

Access: How?

Once we determine where a switch could be placed for an individual client, we need to then determine what type of switch to use. Now switch use is going to vary depending on what we plug it into. If our client is using a switch to control a power wheelchair or a switch toy, a special battery-operated toy that has been adapted for switch use, then the client needs to activate the switch and hold it down with sustained contact or pressure for the amount of time that we want the power wheelchair, or in the case of a toy, to continue moving. Once we release that switch, the power chair or toy will stop. Now particularly for power mobility, this means that the client needs to be able to quickly and consistently let go of the switch because that is how we avoid colliding into obstacles. Other assistive technology such as augmentative communication devices, computers, electronic aids to daily living are primarily accessed when using a switch through scanning. Scanning requires the client to anticipate when their desired selection will be highlighted, and at that time, an activation is required to make the selection. The client has to wait. While they are waiting, their anticipation is building, and for some clients, that can make timing a little difficult. Quick activation is required to make an accurate selection, but release is not usually a timed activity. I really hope that this is a practical course for you, that this can be something that you can use in your job right now or hopefully in the near future when you have an appropriate client.

Think of a client that you are working with right now; a client that perhaps can benefit from switch access to use their various assistive technology devices. Then as we move through this information, think about where you might place a switch and what type of switch you want to try out with the client and write that down. Get a hold of this technology, these switches, to actually try with your client, or work with assistive technology team in your area. Then shoot me an email and let me know what you tried and if it worked for the client.

Ideal Switch Site

  • small movement
  • isolated movement
  • volitional movement
  • controlled activation
  • sustained pressure
  • controlled release

First of all, an ideal switch site is going to use as small a movement as possible. That movement should be isolated and volitional with controlled switch activation. They may need to use sustained pressure if that is required for a power wheelchair, as well as a controlled release. Now sometimes when I am teaching this in a live format, I go ahead and have the participants complete a worksheet as we move along. I would encourage you to grab a piece of paper and take down a few notes particularly as to these particular six features. As we move through, make those notes about the client that you picturing and where you might want to put a switch and what type of switch you might wish to use. Let's look at each of these parameters in a little more detail.

Small Movement

We might see numerous locations on a client that they can use to activate a switch on their body. How do we determine which one to use? We want one that has a small movement. Some of our clients, particularly clients who have a lot of muscle tone, may use quite large movements in an attempt to hit their switch. The problem is sometimes that results in a big wind-up motion as the client is using reflexes, such as an ATNR to drive that movement. This movement involves their head turning to the side, their arm extending, and then finally rotating back towards that switch. The problem with those big huge movements is that it takes a lot of time, a lot of effort, and if the movement is driven with the head, again with a reflex such as that ATNR, it will take the client's eyes off of the task. Instead of the client looking at where they want to drive or what they want to say on a communication device, their eyes are now pulled to the side in an effort to extend that arm. If we can find a smaller movement, that can increase a client's speed and accuracy, we want to do that. This is particularly important in scanning. Scanning is inherently a rather inefficient access method. We want to improve that efficiency as much as we can.

When I was working with Lauren, she was using her hand to directly access her communication device, meaning that she was reaching out with a finger and touching locations on the display. She was able to do this with fair accuracy, but as the day progressed, between fatigue and an increase in tone, she had more difficulty with that accuracy. Due to this, we started exploring switch sites. She was able to readily access a switch mounted by the side of her head, but it felt slow to her because now she was waiting for the scan rather than moving her hand actively over locations on her device. We actually compared the efficiency of the two. We asked her to comprise a specific sentence on her communication device using first her hand and then her head with switch scanning and found that actually the speed and overall accuracy was about the same using either method. Thus, Lauren used her hand in the morning until she became too fatigued. She would develop these back spasms as a result, and then she would switch over to scanning for the rest of her day.

Isolated Movement

We also want this movement to be isolated, meaning that when the client reaches out with whatever body part to activate the switch, that it is not pulling in overflow. One of my teachers used to explain what overflow by using the example of putting on mascara. A person often opens their mouth when putting on mascara in an attempt to really open their eyes wide. Obviously, we do not need to open our mouth to open our eyes, but that is overflow. Some of our clients, in an attempt to activate their switch, will move other parts of their body. Now, this could be technically overflow, or it could be using reflexive, patterns of movement. We want that movement to be as isolated as possible because this helps the movement to be more efficient.

I was seeing Travis for a power mobility assessment. I placed switches by his head for him to drive the chair, but I noticed that every time he was hitting one of those switches, his pelvis was rotating a little bit. This was not a huge deal, but if he had to do this throughout his day to drive his power chair, that overflow was probably going to be more and more exaggerated and would ultimately impact his efficiency. We relocated the problematic switch and he did just fine.

Volitional Movement

We want this movement to be volitional. This might seem like a no-brainer. However, I am surprised how many times I see a switch placed where the client does not have voluntary movement. We also do not want it to be part of a pattern of movement. Jacob had a switch above his right foot. He had to dorsiflex his foot, or lift his toes towards the ceiling, to activate the switch. He did not have voluntary control over that foot at all. He had clonus. The person who had placed a switch there did not realize that clonus was not a voluntary movement for him. Obviously, his access was very intermittent and not a controlled.

Sarah has cerebral palsy, and she had a lot of increased tone. She displayed a lot of extension and adduction in her upper extremities. If she was driving in her middle school and would see some cute boys, her tone would increase causing her arms to cross in front of her and extend. The problem was that her driving switches in front of her at the end of her tray, taking advantage of this pattern of movement. However, with this increased tone, she would drive the chair down the hallway and crash into things. We moved the switches behind her elbows so that she had to not be in that pattern of movement to drive. If she got excited, it would automatically pull her off the switch, and when she was calm enough to drive again, she would do so with that voluntary control.

Controlled Activation

We also need to see controlled activation, both the travel to get to the switch and the pressure required to activate that switch. Brandon, who has muscular dystrophy, required his switches to be placed in the midline and close to his body. He was able to activate switches with his fingers in this position. He also required switches that did not require very much pressure as he does not have a lot of strength.

Part of controlled activation is also speed, being able to activate the switch quickly and accurately, particularly in scanning. When I saw Spencer, he could lift his hand to activate a switch but not with good speed or accuracy. When we opened his seat to back angle in his seating system, we noticed that he had less flexor tone in his upper extremities, and his speed and accuracy increased as a result.

Sustained Pressure

If someone is using switches for power mobility, then sustained pressure is required. If a client has fatigue, perhaps due to muscle weakness, and sustained pressure is required, then we can look at switches that either reduce the amount of travel and activation pressure required or completely eliminate activation pressure. This is where electronic switches can be very helpful for us. Julian has spinal muscular atrophy, and he does not have very much ability to move towards a switch or activate the switch with any force as a result. We needed to accommodate that within his switch set up.

Controlled Release

Release is not as big a deal in scanning, but it is in power mobility because this is how we stop. The client needs to be able to stop consistently and to stop under stress. Amy is a client who is using switches around her head, using an alternative driving method called the head array. She had a switch behind her head and two to the left and right sides of her. She was a very good driver until the fire alarm went off at school. It was very loud. She was already in the hallway, and her extension increased as a result. She became stuck on the switch behind her head and drove pretty much out of control down the hallway until she crashed at the end. Under a stressful situation, she had more difficulty. As a result, we needed to relocate that one switch so that not only would Amy be safe driving, but it would also help her to feel safe.

michelle lange

Michelle Lange, OTR, ABDA, ATP/SMS

Michelle is an occupational therapist with 25 years of experience and former Clinical Director of The Assistive Technology Clinics of The Children’s Hospital of Denver. She is a well-respected lecturer, both nationally and internationally and has authored 7 book chapters and over 175 articles. She is the editor of Fundamentals in Assistive Technology, 4th ed. Michelle is on the teaching faculty of RESNA and the University of Pittsburgh. She is on the RERC on Wheeled Mobility Advisory Board. Michelle is a credentialed ATP, credentialed SMS and is a Senior Disability Analyst of the ABDA.

Related Courses

Dynamic Seating
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Dynamic seating has four primary functions – to allow movement, to diffuse force, to protect the client, and to protect the seating system and mounting hardware. This course will take a look at the product options, discuss clinical indicators and contra-indicators for dynamic components and present case studies to illustrate these points.

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Sensory Technologies: Preparing for the ATP Exam
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The RESNA Assistive Technology Professional certification examination includes questions from a variety of content areas. One of those areas is Sensory Technologies. This module will cover the content area including technologies for people who are hard of hearing, deaf, have low vision, are blind or who are deaf blind.

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A New Era: From EADLs to Alexa!
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Electronic Aids to Daily Living provide an alternative means of controlling devices, primarily within the home environment, including audiovisual equipment, lighting, and thermostats. Advances in consumer home automation technologies have opened new control opportunities for people with disabilities. This course is directly related to the practice of physical therapy and is therefore appropriate for the PT/PTA.

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