Cardiac pacemaker using 4000 CMOS!  - Page 1
Forum section: electronics / general

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 28, 2015, 09:52:39 pm
content: http://youtu.be/Mj9hPSi-aeQ

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 28, 2015, 10:42:12 pm
content: Looks like Youtube has broken the end off - re-uploading..

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 28, 2015, 11:04:15 pm
content: Full version

author: Richard Head
author_rank: Frequent Contributor
timestamp: March 01, 2015, 07:49:09 am
content: Fascinating.I wonder if they can recharge the internal batteries nowadays with a small induction loop so periodic surgery isn't required.I would love you to do a teardown of a modern hearing aid.

author: SeanB
author_rank: Super Contributor
timestamp: March 01, 2015, 09:52:58 am
content: They simply replace it every 10-15 years with a new, as by then you would be getting into the end of the bathtub curve for reliability.As to those PM3 flatpacks, they are aerospace rated devices, and very reliable. They survive being launched on unmanned missions and even are used in missiles. They just use a drop of thermosetting epoxy to glue them to the board during assembly, so the solder joints do not have to handle stress. Leak testing during manufacture is 100%. They are very reliable, much more than overmoulded DIP devices. Only drawback is that the package cost is so much more than the chip inside, even if you are only making one wafer of chips to package in there. Just like the old Intel ceramic packaged processors, where the cheapest part was the die inside.

author: Stonent
author_rank: Super Contributor
timestamp: March 01, 2015, 11:05:28 am
content: Darn, no 555.

author: Stonent
author_rank: Super Contributor
timestamp: March 01, 2015, 11:15:58 am
content: If you still have the battery how about doing a torture test on it?

author: SeanB
author_rank: Super Contributor
timestamp: March 01, 2015, 11:20:27 am
content: Quote from: Stonent on March 01, 2015, 11:05:28 amQuiescent current is too high. The whole board will likely draw under 1mA in operation when pulsing, and in standby likely less than 10uA. Most of that charging up a capacitor in the monostable that was used to generate the slow ( programmable using the reed relay and the counter to increment the presettable comparator for the delay period) clock for the periodic powering up of the active circuitry in the hermetic can.As to the Lithium iodide battery it likely will only fail silently, not generating any gas as it has no liquid inside but a solid electrolyte. Gross overcharging will likely only result in it going short circuit or venting only a very limited volume of hydrogen gas or iodine gas as a failure product.

author: Kjelt
author_rank: Super Contributor
timestamp: March 01, 2015, 12:58:06 pm
content: Excellent video Mike, loved it.Small remark since there also will be young inexperienced people watching could you please show better safety precautions when diamondwheelcutting? I mean holding the device in one hand cutting with the other is asking for accidents

author: German_EE
author_rank: Super Contributor
timestamp: March 01, 2015, 05:52:21 pm
content: I am fairly sure that this device has not been used. Normally the pacemaker is glued to the shoulder blade then the wire goes through a blood vessel to the heart (this explains the silicone coating, to prevent blood clots). When the pacemaker is replaced they just disconnect the wire and plug in a new unit.One thing I have never discovered is how they remove a pacemaker from the shoulder blade. Maybe the glue has low shear strength. Are there any surgeons on the EEVBlog?

author: SeanB
author_rank: Super Contributor
timestamp: March 01, 2015, 06:07:58 pm
content: You just break it off, the glue is only temporary to hold it in place, the body grows bone that fuses to the titanium housing, so it is held fast after the bone cement has cured and is invaded by natural bone recovering the calcium carbonate in it.

author: Kjelt
author_rank: Super Contributor
timestamp: March 01, 2015, 06:43:37 pm
content: My girlfriend works at the cardiac dept, of a hospital. She only knows that nowadays a pacemaker is clamped behind a muscle to the bone and the muscle holds it in place. No glue.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 01, 2015, 08:51:24 pm
content: Quote from: Kjelt on March 01, 2015, 06:43:37 pmAsk her to keep an eye open for any explanted units going spareQuoteWhat's wrong with cable ties...

author: grumpydoc
author_rank: Super Contributor
timestamp: March 01, 2015, 09:18:54 pm
content: Quote from: mikeselectricstuff on March 01, 2015, 08:51:24 pmIf you want more enquire at your local hospital mortuary - pacemakers are removed prior to cremation (the undertakersreallydon't like exploding batteries) and the mortuary usually has a box full of them.Typical placement is in a pocket formed in the left pectoral muscle. Pacemakers have to detect the heart's own electrical activity to ensure that they deliver a pulse at the correct part of the cardiac cycle and will not pace the heart if it is going fast enough on it's own - the VVI designation means that the left ventricle is sensed, and paced and pacing will be inhibited by the heart's own electrical activity. More complex pacemakers may pace both ventricles or even sense the atria and pace the ventricles.The reed switch is so that a magnet can placed over the pacemaker which will then respond by turning off sensing and inhibition and any clever stuff and act as a simple fixed rate pacemaker, typically at 72 beats per minute.

author: mtdoc
author_rank: Super Contributor
timestamp: March 02, 2015, 04:33:28 am
content: Cool Video!Never heard of or seen of a pacemaker attached to a shoulder blade (or other bone).As grumpydoc says they go into the soft tissue of the left chest.Magnets have variable effects on modern pacemakers depending on the manufacturer.Used to be when a patient with a pacemaker died - a magnet held over it would produce a predictable effect - no more.It would be great to see a teardown of a more modern one. One with a built in defibrillator would be especially cool. I'll have to ask my buddy who puts pacemakers in if he can get me a "dead" one - or ask the mortuary next time I hear of a patient with one dying.

author: Stonent
author_rank: Super Contributor
timestamp: March 02, 2015, 07:36:01 am
content: Quote from: mtdoc on March 02, 2015, 04:33:28 amLike this?

author: Kjelt
author_rank: Super Contributor
timestamp: March 02, 2015, 08:21:18 am
content: Quote from: mikeselectricstuff on March 01, 2015, 08:51:24 pmWill do. She has one but wants to keep that one herselfShe will keep her eyes open, however she does not work on the surgery dept. but on the cardiac aftercare/support dept.

author: mtdoc
author_rank: Super Contributor
timestamp: March 02, 2015, 05:45:36 pm
content: Quote from: Stonent on March 02, 2015, 07:36:01 amHa! Yes - thanks - I hadn't seen that one!Often implantable defibrillators are combined with pacemakers in the same package.

author: Stonent
author_rank: Super Contributor
timestamp: March 02, 2015, 05:56:38 pm
content: Quote from: mtdoc on March 02, 2015, 05:45:36 pmHe's got some more. 2 AEDs, some pill cams, blood sampling machine, a few xray machines also.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 02, 2015, 07:35:50 pm
content: Quote from: Stonent on March 02, 2015, 05:56:38 pm..and another type of pill-cam incoming....

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 02, 2015, 09:05:44 pm
content: Quote from: SeanB on March 01, 2015, 06:07:58 pmIt is fairly interesting what "bone cement" is, learned that a few years ago.I would neve have thought that "bone cement" is a fairly common substance every hosehould most likely has some of.Bone cement is PMMA, poly methyl methacrylate or commonly known as plexiglas.

author: Seekonk
author_rank: Super Contributor
timestamp: March 02, 2015, 10:15:32 pm
content: My mentor was head of biomedical engineering at a teaching hospital. You would have to be old to remember these, but they used to sell metronome modules epoxy potted in cupcake tins in the back of magazines like Popular Electronics for $2.95. He made external pacemakers with them with the addition of a speaker transformer to boost the pulse voltage. I asked him if he wasn't concerned that these are usually made with crap surplus parts. He said that there were always nurses around monitoring the patients. This was early in the history of biomedical engineering. He did some amazing work with video and x-ray imaging.