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design challenges in pacemaker circuitry (interferers) (Read 13720 times)
vivkr
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design challenges in pacemaker circuitry (interferers)
Jul 23rd, 2008, 8:06am
 
Hi All,

Perhaps this is not the best forum but the closest one.

Could someone tell me the kind of environmental constraints an IC faces when built into
a pacemaker apart from the usual low-voltage, ultralow power and very high reliability ones.
I am specially interested in knowing about the noise and interferers which come into play here.
Any links providing more information would also be welcome.

Regards
Vivek
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loose-electron
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Re: design challenges in pacemaker circuitry (interferers)
Reply #1 - Aug 3rd, 2008, 4:01pm
 
Hm.... You have touched upon the major ones already. There is a suite of robustness tests that get done, that are covered under the general list you metioned.

Suggestion - Get in touch with Medtronics (in Minnesot and Arizona) and ask them what tests they use for their pacemakers.
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Jerry Twomey
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vivkr
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Re: design challenges in pacemaker circuitry (interferers)
Reply #2 - Aug 4th, 2008, 12:11am
 
Hi Jerry,

I will do that, but do you think they would share such information with someone working at another company? Our company doesn't make any pacemakers though.

Vivek
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Re: design challenges in pacemaker circuitry (interferers)
Reply #3 - Aug 7th, 2008, 7:36am
 
Hi,
I am not an expert at for this topic but I can recommend the book:
"DESIGN AND DEVELOPMENT OF MEDICAL ELECTRONIC INSTRUMENTATION" ISBN 0-471-67623-3. There the design and implementation of a pacemaker using discrete devices is described.
I think there is a lot of analog signal processing and therefore you have to deal with the design of operational amplifiers. But also digital signal processing is important because a digital filter needs no capacitances Smiley. I know that these companies uses Smart-Power processes (BCD [bipolar cmos dmos]) to integrate high voltage features like defibrillation.
Another topic is the packaging! You have to care about material combinations of the package and electrodes.

Kind regards,
haikom
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loose-electron
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Re: design challenges in pacemaker circuitry (interferers)
Reply #4 - Aug 7th, 2008, 1:49pm
 
Vivek:

The worst they can do is say no. You can also approach it from the perspective of a potential customer who will be having one of these things implanted into you.

"As an electrical engineer who is expected to receive one of these devices as an implant, I want to know what tests you do to insure (ensure?) my safety."

You get the idea....

I actually enjoy doing medical electronics because you get to see the results of your work actually helping someone, rather than the latest cell phone, PDA, laptop  etc. gadget that is going to be obsolete junk in 5 years.

Jerry
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Re: design challenges in pacemaker circuitry (interferers)
Reply #5 - Sep 6th, 2009, 10:21am
 
Addendum -

Read the test standard for medical electronics:

IEC/EIN  60601

The full suite of of qualification criteria is there.
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Re: design challenges in pacemaker circuitry (interferers)
Reply #6 - Jun 21st, 2011, 2:53pm
 
Only has to work at one temperature!  

http://rfcooltools.com
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Re: design challenges in pacemaker circuitry (interferers)
Reply #7 - Jun 22nd, 2011, 6:07am
 
rfcooltools.com wrote on Jun 21st, 2011, 2:53pm:
Only has to work at one temperature!  

http://rfcooltools.com


I would be careful with that comment. While it is true that a pacemaker or other sort of implanted electronic gadget has to work at body temperature (which is a constant), that may not necessarily mean that you design only for this for the following reasons:

1. You obviously need some margin. If you happen to make a circuit which works only over a 20-30 degree range but fails completely outside, then you may have a bad design to begin with.

2. A curious case relates to potential litigation. What happens the wearer of the pacemaker happens to die accidentally of a heart problem or something else and you need to prove that it was not a faulty pacemaker that caused it? The patient may have been outside during a snowstorm and the body might have cooled down quite a bit before being found. If there's any kind of readout electronics in there (I don't know if pacemakers carry such stuff) which logs the activity of the gadget, then atleast this circuitry would need to go on working correctly. Else you cannot prove that your design was not at fault. It does sound a bit weird but I atleast came across such a requirement for an implantable gadget we were once designing although it wasn't a pacemaker.

Vivek
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Re: design challenges in pacemaker circuitry (interferers)
Reply #8 - Jun 22nd, 2011, 2:36pm
 
Newer pacemakers have the equivalent of the "black box flight recorder" within them showing and recording activity, need to intervene in stimulus pacing etc.

and yes, you can download whats been recorded and play it back so you know what has happened.

As for the "one temperature" comment? Sorry, not the case.

Here is a listing overview of the basic tests that any and all medical products must meet:

http://effectiveelectrons.com/medee.html

That is the very basics, specific applications require specific tests, and life support devices require an even more strenuous set of case by case requirements.

Consumer electronics 90% design, 10% regulatory
Medical electronics, 90% regulatory, 10% design

I have redesigned a bunch of medical products, because the original designers were clueless on regulatory issues. Had to trash what they did and start over.
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Jerry Twomey
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