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Re: Pacmakers and Tesla coils = bad??
This is a little long, but please indulge me !
The note at the end could be placed in the Safety FAQ ??
At 05:48 11/02/2000 -0700, Terry Fritz wrote:
>It appears today's modern computerized RAM, ROM, programmable,
>microprocessor, built in defibrillator, etc. pacemakers may be "confused"
>by things like arc welders, diathermy, x-ray, MRI, Shoplift detectors,
>airport security, etc. equipment that puts out powerful RF or magnetic
>fields.
This is true, to a point.
>My first thought was that Tesla coils beat all those interference sources
>easily!!
No question !
The newer pacemaker units are programmed by inductive coupling. You have a
PC driven programming unit which attaches to a coupling probe which is
placed over the pacemaker (in the person who is wide awake) and the unit is
re-programmed accordingly while you have a chat to the patient.
We usually test the defibrillators with people under light general
anaesthesia, 'cause the jolt is a little unpleasant awake. The unit is
capable of *inducing* VF (ie a cardiac arrest) in the patient, so that the
units response can be checked. In life it only goes off when the person
has an arrest (therefore is unconscious) but to check this awake would be a
little nasty. A TC could easily "instruct" the unit to do this in error !!
CLEARLY, both of these devices have tuned receiving coils which are used
for in situ programming. Both may actually CAUSE arrhythmias in the heart
and close proximity to a TC would be highly inadvisable.
IMPORTANT NOTE: Virtually all of these devices have an in-built safety
feature. Placing a moderately powerful magnet over the control unit
(usually just under the clavicle, or on the side of the chest/abdomen) will
cause them to revert to a standard pre-programmed safety mode. This will
however revert once the magnet is removed.
For example, all operating theatres in Oz (and USA I believe) have
appropriate magnets in the top draw of the anaesthetic machine for exactly
this reason.
>I would think a Tesla coil would be an excellent test bed for pacemakers
>and their susceptibility to nasty electromagnetic fields. It would have to
>be a lab grade device that was consistent. Perhaps a few million bucks
>from a government grant would help out defining how a Tesla coil could be
>used to rate such devices... Apparently, the new pacemaker's ability to
>deal with such emitted energy sources is a very big deal...
Now I was wondering what my next research project could be ;-)
Mark
___________________________________________________________
Mark Finnis Hm: 61 8 8431 2889
Staff Specialist Wk: 61 8 8222 4000
Intensive Care Unit Fax: 61 8 8223 6340
Royal Adelaide Hospital Mbl: 041 2324268
www.health.adelaide.edu.au/icu
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