very interesting observations Geoff - I have been thinking many of the
same things. That is partly why my wiseDX allows the setup to be so
flexible (commercial interest?). It is also why it is so important to
have a grasp of the clients cognitive profile other than 'he seems
bright'. The thing in your last paragraph about nomenclature is also
interesting - I have given up trying to explain to clients dad's
(particularly if they are technical) how the system works - its so much
easier to let the client explore and they figure it out - if you get into
the 'now when you hit that switch it does this but only when that light
is on but not at the same time unless......' it sounds more complicated
than it is.
The thing about switch use is that there is clearly more to it than one
would think as you have stated. There is also the issue (particularly
with integrated systems but also with VOCAs and computers) of levels of
ability with switches. ie you might be reasonable with one switch and a
bit rubbish using a second switch - however - you may find the second
switch useful for the odd task or two that doesnt require really good
control and not often used. Just what task you offer that switch will
depend on the clients level of skill with it. I see it as making use of
the clients maximium abilities. and now I am in danger of drivling on -
but an interesting topic.
Colin Clayton
At 08:59 24/06/2006, you wrote:
Hello
Richard.
I am interested to hear you mention the problems with symmetry, I have
long been wondering about the ethics of the possibility of someone ending
up with an Acquired Postural Deformity through the use of a switch or
joystick in a location that requires the repetitive use of a posture that
is "unbalanced". Sometimes though there would seem to be no
practical option if someone is to achieve their mobility goals. Similarly
some people chose to adopt a poor posture in order to remain
functional.
I read the article by Linda Burkhart and it was informative, although is
seems to concentrate on the lower range of cognitive ability. The
situation with two switch scanning for a scanning wheelchair direction
controller is even more complex than that for use with a communication
aid.
Firstly, A communication aid is inherently a two dimensional scenario.
The client uses MOVE to advance the highlighted word through either
column or row and the CHOSE switch to make selections. There are no
timing considerations and the visual and cognitive load are all focussed
on the one device, the one physical area. With powered mobility, the
client has to concentrate first on the wheelchair scanner - and recognise
that the spatial layout of the lights on the scanner are a representation
of the possibilities of the direction of movement within a much larger
three dimensional volume of space, which is not necessarily an easy thing
to do. Then having selected their required direction, they have change
their focus of attention to the environment around them, literally
changing their optical focus, and at the same time, engage with their
CHOSE switch in order to initiate movement. Having achieved some movement
in the required direction, they must then shift their focus of attention
back to the scanning display and re-chose the next direction. This can be
an extremely laborious and time consuming process, where the cognitive
load is constantly shifting from one task to another and back
again.
Secondly, the operation of the CHOSE switch now becomes a timed task.
They must decide when they can press the switch and when they must
release it. The consequences of mis timing can be frustration in not
achieving their goal, or at the other extreme, damage to equipment or
injury to themselves or others. With a communication aid, it doesn't
matter how long they hold the CHOSE switch, the desired outcome will be
the same. The situation with the MOVE switch is slightly different
depending if the location highlight continues to move when the switch is
held down, or if it requires a press-and-release to move from location to
location. If the highlighted location continues to move when the MOVE
switch is held down, then this again becomes a timed function in deciding
when to let go.
Thirdly, where the client is already using two switch scanning for their
communication aid access, this is invariably a "momentary"
switch selection activity, (Simon's comments not withstanding),
particularly for the CHOSE switch. With a scanning wheelchair controller,
the pattern of movement must be re-learnt, as the CHOSE switch must now
be held down for an extended period of time in order to maintain travel
in the required direction. This is particularly difficult when the head
is used to operate the switches as sometimes a "muscular
impulse" is used to initiate an inertial movement of the head which
may have no force behind it when it gets to the switch. This nevertheless
operates the switch in a momentary manner. When you have to hold down the
switch, you need to use continuous muscular force to maintain contact
with and operation of the switch. Mobility switches often have a higher
spring rate in them in order to ensure that they are less likely to stick
in the ON position with all the possible consequences that were mentioned
before. This then returns us to the problem of Acquired Postural
Deformity where a task or effort is predominantly biased to one side or
direction.
FInally, consider the situation where we integrate a communication aid
onto a powered wheelchair with a scanning direction indicator using two
switch scanning for both functions. When the client is communicating they
must use a short press to CHOSE. When the client is driving they must
remember to use their long press to CHOSE. This is an added cognitive
load over and above the use of either device. There is also the problem
of nomenclature. When using a scanning wheelchair direction
controller, the client must use their MOVE switch to CHOSE
which direction they want to move, and then use their CHOSE switch to
MOVE in that direction. I an not sure what the solution to
this one is.
You or I without any physical or cognitive impairment can do all of the
these things without much effort, much like driving a car. The situation
is somewhat different for an eight year old with CP, possibly poor head
control and a learning difficulty.
Sorry to have gone on a bit, but as Simon has said, there is very little
of this written down anywhere.
All I need to do now is learn how to store it on the WIKI
Best regards,
Geoff Harbach. I.Eng MIED IIPEM
Registered Clinical Technologist
LEPMIS
Special Controls for Special People
Integrated Systems for an Integrated Life Style
on the Web
LEPMIS.co.uk
e-mail
[log in to unmask]
In a message dated 23/06/2006 16:39:22 GMT Daylight Time,
[log in to unmask] writes:
- My own experience with head switching underlines the importance of
symetry
- in movement where at all possible. A CP boy of ten years drove
his
- wheelchair at school very sucessfully with three head switches for a
period
- of four years. He was symptom free thoughout. However, he later
accessed his
- VOCA using a single head switch, as prescribed by the speech
therapist.
- Within a short time he complained of neck pain, which prompted a
fundimental
- review of his access.
- More multidisciplinary communication required!
- Richard Taylor BDS B Eng. MSc.
- Assistive Technologist
- Registered Clinical Technologist
- Bournemouth
- ----- Original Message -----
- From: "Richard Walter"
<[log in to unmask]>
- To: <[log in to unmask]>
- Sent: Thursday, June 22, 2006 11:59 PM
- Subject: Re: Step Scanning with Head Switches
- > I must admit to being a little confused (- becoming
increasingly
- > frequent these days).
- >
- > What do you usually set for a scanning mode using two
switches?
- >
- >
- > Generally step scanning removes the need for timing but the
student does
- > obviously need to be able to physically operate the two
switches.
- > Something to watch is that two switch scanning (especially head
scanning
- > can (does) have repercussions on the whole physical posture and
tone of
- > the student.
- > I sometimes try the choose switch as a hand switch and the move
switch
- > as a single head switch.
- > Most of our pupils if thy are using head switches have poor
hand/arm
- control
- > Since the choose switch is used less frequently it can be
operated by a
- > less controlled movement.
- >
- > Actually very few of our pupils are capable of controlling
scanning
- > access but It is also much easier to assist scan in a step
scanning mode.
- > for example see Linda Burkhart's article on
- >
www.lburkhart.com/hand2sw4s.htm.
- >
- > Richard Walter
- > Meldreth Manor School
- >
- > Judge Simon wrote:
- > > It only occured to me today that Step Scanning has a big
advantage over
- any
- > > other scanning method for head switching... So I documented
it here:
- > >
- http://assistech.org.uk/doku.php?id=experiencebase:generalat:switch_scanning
- > > _with_head_switches (-;
- > >
- > > No doubt it is only me that has just twigged this.
- > >
- > > Cheers
- > >
- > > Simon
- > >
- > > Clinical Scientist
- > > ACT
- > > 0121 627 1627 ex 53245
- > >
- >
Colin Clayton BSc, CEng, MIEE, MIPEM
Great Ormond Street Hospital for Children
The Wolfson Centre
Mecklenburgh Square
London WC1N 2AP
Tel: 020 7837 7618
Fax: 020 7833 9469
visit
www.wisedx.com
email: [log in to unmask]