Hi Peter,
Thank you. It is so nice to get a Doctor's answer to a medical question. Nothing ruins a rousing discussion like someone with facts. :^))
Matt _D
-----Original Message-----
From: pterren <pterren@xxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Mon, Apr 21, 2014 9:09 am
Subject: Re: [TCML] Tesla coil threat to pacemakers
Re pacemakers
(I am a medical specialist and I have inserted temporary pacemakers. My
fastest time is 20 minutes.)
I also have 40 years of Tesla experience.
I hope that this article is a bit more definitive.
Short answer: Tesla coils are safe for pacemakers.
Intermediate answer: In essence, it appears that it would be difficult to
destroy a pacemaker with a Tesla coil without actual sparks to the person
causing tissue damage and difficult to even stop it functioning to provide a
regular pulse.
Long answer: You need to look at data, rather than speculate. In the
absence of direct Tesla coil data, however, some informed extrapolation can
be made.
Firstly:
Here is an article on induction cooking (24kHz) Looking at loop currents
hand to hand with (non-pacemaker volunteers).
Old model pacemaker sensitivity is 100mV for conducted current. Only 2% of
the conducted current appears across the pacemaker sensing/pacing leads.
Importantly, the pacemaker will not turn off, but default to asynchronous
pacing. This is a minor problem if you are not pacemaker independent when R
on T pacing might induce VT.
Keeping a forearms length away will lower induced voltages to less than
80mV, below all tested pacemakers.
However, apart from 1% of patients with functioning old pacemakers, modern
pacemakers have a median threshhold of 3.5 V (compared with the .09 V of the
exceptional one discontinued 16 years ago).
Not only that, but the higher frequencies would be expected to increase that
threshold. (Tesla coil frequencies are typically 100kHz (40kHz - 4 Mhz).
My extrapolation is that a typical modern generation pacemaker perhaps with
5V threshold to 100kHz to be generated across body (hand to hand) resistance
(they quote 1.2k Ohm) would be 5mA.
This is a large current and if DC would give some muscle spasm and
difficulty breathing. The pacemaker wont even stop working. Not likely to
be achieved with spectator Tesla coil exposure.
http://europace.oxfordjournals.org/content/8/5/377.full
Secondly:
Diathermy uses high frequencies (300 - 500kHz) for cutting and coagulation
similar to a Tesla coil.
There are a lot of theoretical considerations but: ".. the available
published information suggests that surgical diathermy poses a substantially
smaller hazard than many other medical and indeed non-medical
electromagnetic sources"
Bear in mind that the current involved at the point of contact is enough to
cause tissue damage (hence coagulation).
My extrapolation is that similar tissue damage from a Tesla coil at similar
frequencies would require a significant spark giving tissue burns. It is
unlikely that this would occur with spectator Tesla coil exposure. If you
are getting burnt, shift back a bit!
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2001150/
Thirdly:
MRI (magnetic resonance imaging). The magnetic field will trigger VV0 pacing
(ie it continues to work at a baseline rate). Other problems can occur as
well, related to the RF energy. Not recommended.
My extrapolation is that the magnetic field of 1-3 Tesla MRI would not be
approached by any Tesla coil. The RF field is high enough to induce heating
of the pacemaker electrode, much higher than expected from a Tesla coil
which is not a strong RF transmitter having very poor aerial matching.
http://bja.oxfordjournals.org/content/93/1/95.full.pdf
Fourthly:
Defibrillation. A current pulse (uni or bipolar) passes through the skin
impedance of typically 100 ohms. (My best with excellent skin preparation
was 48 ohms between paddles).
Energy is typically 200j monophasic or 130 + 20j biphasic with peak at 10ms.
Voltage is from 5kV unipolar to 2.2kV bipolar. Current is between 20 and 50A
peak. With a pacemaker it is recommended to keep the defibrillation
paddles/pads away from the pacemaker.
It is recommended that an AP paddle position be used but it is not likely to
damage modern pacemakers.
My extrapolation. Even a significant heart - stopping (or restarting) DC or
single 50Hz cycle (somewhat similar to 1 cycle of a biphasic defibrillator)
is unlikely to damage a pacemaker.
http://www.ebme.co.uk/articles/clinical-engineering/12-biphasic-defibrillation?showall=&start=1http://www.resuscitationcentral.com/defibrillation/biphasic-waveform/
Fifthly:
Tasers seem to have no effect on pacemakers or ICD's.
My extrapolation is that short (5 second) bursts of debilitating HV pulses
do not affect a pacemaker.
http://www.ncbi.nlm.nih.gov/pubmed/17491105
Sixthly:
Cellphones - no effect.
http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/HomeBusinessandEntertainment/CellPhones/ucm116311.htm
Sevently:
There are many other situations where energy is applied directly or by RF
fields but the above situations cover many of these.
https://www.heart.org/HEARTORG/Conditions/Arrhythmia/PreventionTreatmentofArrhythmia/Devices-that-may-Interfere-with-Pacemakers_UCM_302013_Article.jsp
Anecdote 1, DC Cox (who died last year) had an ICD (pacemaker and
defibrillator) and I seem to recall him stating that he stayed 20 ft away
from his big coil. Which is probably as close as you would want to stand
anyway from his big coils.
Anecdote 2, I have a little battery powered SIDAC pulsed flyback that gives
1 inch weak sparks for my popular "free shocks". One person stated AFTER
having a shock: "I hope this is safe for pacemakers". Obviously it was and
he walked away happy.
I hope this gives a some clarity to the Tesla coil question. Basically I
believe that a Tesla coil is very unlikely to cause harm to a person with a
pacemaker.
Peter
tesladownunder.com
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