Author Topic: Building a DIY defibrillator in an emergency,  (Read 19133 times)

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Online PsiTopic starter

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Building a DIY defibrillator in an emergency,
« on: April 24, 2020, 01:34:17 pm »
Engineering thought experiment time....
I've always wondered, how feasible is it to build a crude defibrillator in an emergency from random household electronics.
Something that has at least some hope of restarting a heart.

Scenario

- You're an electronics engineer in a group of 3 including you. All are engineers,
- You're in the middle of nowhere, 12 hours away from any help.
- One of the people has a medical event and their heart goes into fibrillation
- You and the other person take turns giving CPR

CPR is very tiring, eventually you will both get too fatigued to continue.
Even with 2 people taking turns you're not going to be able to do it for 12 hours.

So, since the person is going to die before help arrives you both decide to rip apart any electronics available and try to build a crude defibrillator in the hope it might restart their heart. You decide to take turns building while the other does CPR
 

Assumptions for this thought experiment.
- There is 240V power at the location
- There is a house and workshop with a good selection of common tools and equipment.


Initial thoughts about some stuff you will likely have to work with

- 330V DC available in any mains powered device that has a bridge rectifier.
- You could easy hack together a voltage doubler to get 600V.
- You could get 2kV from the microwave, but it only has around 1uF cap
- The kitchen probably has some cooking utensils that have a large flat metal surface and insulated handles for electrodes.
- aloe vera gel and salt can be used to make conductive gel

Unknowns
- How short of a pulse do you need to apply. Can you control it just by touching the electrodes to skin or does the timing have to be critical.

I know modern defibrillators employ lots of advanced timing and pulse shaping to mimic the human heart response and be more effective. But all we are going for is the best we can do with what we have,

 



« Last Edit: April 30, 2020, 08:55:16 am by Psi »
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Offline jogri

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Re: Building a DIY defibrillator in an emergency,
« Reply #1 on: April 24, 2020, 02:13:45 pm »
Quote
One of the people has a medical event and their heart stops beating.

If that happens they are most certainly dead, defibrillation is only usefull when you have ventricular fibrillation (meaning that the heart muscle twitches really fast [up to ~12Hz] without moving blood). What a defibrillator does is apply a really nasty electric shock with ~300J energy that overpowers the chaos in the hope that the signal from the sinoatrial node (who is responsible for firing the heart muscles) can start a controlled stimulation of the heart muscles to get it to beat again.

CPR (the pumping part) is just there to squeeze the heart manually and get the blood to circulate a bit to ensure that the brain doesn't run out off oxygen.

A defibrillator uses a pulse in the 300J range at a few kV, so i'd start collecting capacitors (to store the energy) and making a crude voltage multiplier. I wouldn't worry about building some fancy pads, copper wires and a saline solution should suffice.

Btw, chances are that you don't have the necessary manpower to build something with only two guys as they are both needed for the CPR: One has to pump while the other has to get air into the lungs, otherwise he is most definitely dead after ten minutes when the oxygen in his blood runs out.
 

Online PsiTopic starter

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Re: Building a DIY defibrillator in an emergency,
« Reply #2 on: April 24, 2020, 02:23:19 pm »
If that happens they are most certainly dead, defibrillation is only usefull when you have ventricular fibrillation (meaning that the heart muscle twitches really fast [up to ~12Hz] without moving blood).

Thanks, i think i knew that but had forgot.  Have edited post.

Btw, chances are that you don't have the necessary manpower to build something with only two guys as they are both needed for the CPR: One has to pump while the other has to get air into the lungs, otherwise he is most definitely dead after ten minutes when the oxygen in his blood runs out.

Breathing air into the lungs is no longer considered necessary for CPR. I'm not sure of the details but apparently the lung muscles do move a little while in ventricular fibrillation and you get enough oxygen to keep the brain alive with just chest compression.
However, i'm not sure how well that works for hours on end. so yeah, might need extra person.
« Last Edit: April 24, 2020, 02:30:54 pm by Psi »
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Offline m98

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Re: Building a DIY defibrillator in an emergency,
« Reply #3 on: April 24, 2020, 03:05:59 pm »
Uhm, since we are in a hypothetical scenario, you already somehow know he is in cardiac arrest and has a shockable rhythm ... punch him mildly hard exactly in the middle of the sternum immediately after he dropped, before starting any other measures.
Don't do this in real life unless you exactly know what you're doing.

Quote
Breathing air into the lungs is no longer considered necessary for CPR.
Because way too many people do it wrong, or won't even start CPR because they're disgusted. It will still vastly improve the outcome.

The best measure in such a scenario would probably be to start the most optimal CPR you can manage (after establishing that he actually is in cardiac arrest), rotate positions every two minutes to get consistent and good compressions, and hope he eventually starts cursing you. There also wouldn't really be a point to perform CPR for more than an hour or two without any diagnostic equipment and medications available. You simply can't treat the condition that caused the cardiac arrest, and it most probably is also too late to do so at that point. Especially after 12 hours.
 

Online PsiTopic starter

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Re: Building a DIY defibrillator in an emergency,
« Reply #4 on: April 24, 2020, 03:36:55 pm »
There also wouldn't really be a point to perform CPR for more than an hour or two without any diagnostic equipment and medications available. You simply can't treat the condition that caused the cardiac arrest, and it most probably is also too late to do so at that point. Especially after 12 hours.

What if the condition that caused it was an electric shock. So nothing really wrong with the person other than fibrillation ?
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Offline jogri

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Re: Building a DIY defibrillator in an emergency,
« Reply #5 on: April 24, 2020, 03:52:21 pm »
Quote
Breathing air into the lungs is no longer considered necessary for CPR.
Because way too many people do it wrong, or won't even start CPR because they're disgusted. It will still vastly improve the outcome.

Yeah, the good old "accidentally inflating the stomach" trick... Not pretty

Quote
punch him mildly hard exactly in the middle of the sternum immediately after he dropped, before starting any other measures.

Chances are that you are just breaking off a part of his sternum, leading to him getting stabbed by his own bones every time you compress his chest while performing CPR. That punch is only effective when you already have an ECG hooked up and see him having a heart attack in realtime, but almost all ECGs used by emergency services have a built in defibrillator, so what's the point of punching him before you shock him?

But back to the problem: I'd probably go for the microwave and add a few capacitors, together with a crude rectifier to maintain the voltage at the capacitors. Use an outlet with a switch, that way you can charge your caps by switching on the outlet and shock him while the outlet is off to avoid electrocuting him constantly.
 

Offline m98

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Re: Building a DIY defibrillator in an emergency,
« Reply #6 on: April 24, 2020, 04:38:40 pm »
Chances are that you are just breaking off a part of his sternum, leading to him getting stabbed by his own bones every time you compress his chest while performing CPR. That punch is only effective when you already have an ECG hooked up and see him having a heart attack in realtime,

Quote
since we are in a hypothetical scenario, you already somehow know he is in cardiac arrest and has a shockable rhythm ... punch him mildly hard exactly in the middle of the sternum immediately after he dropped ... Don't do this in real life unless you exactly know what you're doing.

 

Offline Wallace Gasiewicz

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Re: Building a DIY defibrillator in an emergency,
« Reply #7 on: April 26, 2020, 10:42:45 pm »
Having performed thousands of CPRs on patients, I can tell you that if you do not have a shock available within maybe 15-30 min. It is futile.
I am not sure of current recommendations as to when to stop. We almost always went longer.
Defib machines use capacitor discharge and the output is measured in Joules. In v fib there is no timing of pulse.
200 Joules is about 500 Volts charged into 2000 uF caps.
The newer defibs are bi-phasic, I don't think we can make one fast enough.
After all sorts of goofy recommendations, including "stairstep breathing", the CPR gurus found out that just pumping the chest circulates enough air. Not too fast, about one Hz, faster in children.
Precordial chest thumps can work, but you must be careful not to break anything. I have seen it many times, usually in witnessed v tach in the ICU. Can work like magic.
After too vigorous CPR, the rib fractures and dislocations will make CPR ineffective. You need an intact chest for CPR to work.

Without an ECG you do not know if there is any activity in the heart at all. You do not know if the individual is in V fib. You shock anyway when in doubt.
That's all you can do. If there is not electrical activity in the heart, shock will not help, but we try anyway. Maybe the V fib is so fine it is not visible on the ECG machine.
There are asystolic conditions (no electrical heart activity) that respond to pacing either internal or external.

If nothing else was available I would charge up some big capacitors and connect them across the chest. Whatever you have. MacGiver it. Maybe 400-1000 volts.
At this point it cannot hurt
« Last Edit: April 27, 2020, 10:10:29 pm by Wallace Gasiewicz »
 

Online SiliconWizard

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Re: Building a DIY defibrillator in an emergency,
« Reply #8 on: April 26, 2020, 11:04:21 pm »
Without an ECG you do not know if there is any activity in the heart at all. You do not know if the individual is in V fib. You shock anyway when in doubt.

Have you ever done that? Shock while having no ECG? (And if so, has it ever succeeded?)
 

Offline Wallace Gasiewicz

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Re: Building a DIY defibrillator in an emergency,
« Reply #9 on: April 26, 2020, 11:56:32 pm »
The first cardioverter I used was an electron  tube type machine with a CRT. It took a while to warm up. Was about two foot cube. Weighed maybe 100#
The ECG leads were separate from the paddles. Sometimes they fell off. Also took a while for the CRT tube trace to return. I was an orderly back then. The doctors would shock anyway. No pulse etc...
Newer cardioverters have the leads in the paddles but sometimes there is not a good connection because of sweat, dirt or whatever. Makes a real messy trace. Unusable.
If you are not sure, shock, that is the only thing that can save the person. This has happened and can work.

Do I ever recall shocking someone in asystole who recovered?  No. I cannot remember this ever working.
We were talking about a MacGyver approach without access to an ECG machine. I have never tried this at home.
 

Offline SilverSolder

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Re: Building a DIY defibrillator in an emergency,
« Reply #10 on: April 27, 2020, 02:41:07 pm »
[...]  the CPR gurus found out that just pumping the chest circulates enough air. Not too fast, about 60 Hz, faster in children.  [...]

60 times per second?  - typo?
 

Online SiliconWizard

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Re: Building a DIY defibrillator in an emergency,
« Reply #11 on: April 27, 2020, 02:50:55 pm »
[...]  the CPR gurus found out that just pumping the chest circulates enough air. Not too fast, about 60 Hz, faster in children.  [...]

60 times per second?  - typo?

Surely that's more like 60 per minute.

Otherwise - not only are they talking about McGyver defibrillators here, but CPR at 60 Hz, maybe you'd do that with some big vibrator directly connected to mains. :-DD
 
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Offline Wallace Gasiewicz

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Re: Building a DIY defibrillator in an emergency,
« Reply #12 on: April 27, 2020, 10:08:33 pm »
Yea one Hz, sorry.

Yea vibrating... thanks for correcting me.. but this brings up another strange memory.  At one time there were respirators proposed that worked at vibrating frequencies, these, as far as I know, were for use in NICUs. I do not think that any of them were actually made for use but there were studies on animals. Supposedly they were for use in NICUs and were less apt to cause ventilator related lung damage. Supposedly "vibrated" the air in the lungs to mix incoming air with air in aveoli.
« Last Edit: April 27, 2020, 10:16:19 pm by Wallace Gasiewicz »
 

Offline SilverSolder

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Re: Building a DIY defibrillator in an emergency,
« Reply #13 on: April 27, 2020, 10:38:26 pm »

Interesting idea (vibrating the air in the lungs) - maybe it promotes the interchange of gases between the blood and the air, making better use of whatever air is there?
 

Online PsiTopic starter

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Re: Building a DIY defibrillator in an emergency,
« Reply #14 on: April 28, 2020, 10:58:48 am »
Having performed thousands of CPRs on patients, I can tell you that if you do not have a shock available within maybe 15-30 min. It is futile.
...
200 Joules is about 500 Volts charged into 2000 uF caps.
...
If nothing else was available I would charge up some big capacitors and connect them across the chest. Whatever you have. MacGiver it. Maybe 400-1000 volts.
At this point it cannot hurt

Thanks! Some good info there,
Especially interesting that you only have 30min or so to get any DIY solution implemented.

2000uF at 500V is rather large and might make it unfeasible right there,  that's not going to be easy to find in random household devices.

Anyone got ideas on how to build a 2000uF cap using commonly available devices? Even 1000uF would be hard
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Online NiHaoMike

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Re: Building a DIY defibrillator in an emergency,
« Reply #15 on: April 28, 2020, 01:40:28 pm »
2000uF at 500V is rather large and might make it unfeasible right there,  that's not going to be easy to find in random household devices.

Anyone got ideas on how to build a 2000uF cap using commonly available devices? Even 1000uF would be hard
Only have to take apart a few PC power supplies to get enough caps.

I would go for the microwave oven transformer and connect AC power for a split second by swiping two wires together. Very easy to put together on short notice.
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Offline G7PSK

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Re: Building a DIY defibrillator in an emergency,
« Reply #16 on: April 28, 2020, 09:00:19 pm »
https://youtu.be/FnAOmxnQJsM



<iframe width="1280" height="720" src="https://www.youtube.com/embed/FnAOmxnQJsM" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
 
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Online SiliconWizard

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Re: Building a DIY defibrillator in an emergency,
« Reply #17 on: April 28, 2020, 11:10:34 pm »
Ahah, I remember this Mr. Bean episode. :-+
 

Offline tpowell1830

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Re: Building a DIY defibrillator in an emergency,
« Reply #18 on: April 29, 2020, 09:05:26 pm »
A very interesting proposition with some interesting responses.

Having worked at an industry leading company that made implantable defibrillators, I have to say that there is no way that you can be sure that fibrillation is the cause of the patient's "medical event" without observing the heart rhythm with special instruments. All of the defib units that I have seen, whether a portable external unit or an implanted unit, has circuitry and software to detect that fibrillation is in progress. All of the units that I have seen also work automatically and will give a specific joule output to the attachment pads. Unless the group of engineers has instruments that can detect heart rhythm, they cannot know that fibrillation is present, and shocking someone is a bad idea. The reason to shock is to completely stop the heart activity so that the body will sense and restart natural sinus rhythm. The defib units, after giving a specific joule output will start monitoring the heart rhythm and will up the joule output and give another shock if the heart is still in fibrillation and repeat until a natural rhythm is detected. I think most units have a specific number of times that it will shock and then will stop further attempts.

With that said, if there were adequate pieces of electronics around and an oscilloscope, it could be possible to monitor and then defib, perhaps with 10-20% chance of success, which if I were the patient, that is 10-20% more chance than sitting around and waiting for help to arrive, because the longer the heart is in fibrillation , the less chance of brain survival that you have. With someone doing chest pumps, while others are trying their very best, the patient has a better chance.

Just my 2 cents...
« Last Edit: April 29, 2020, 09:16:29 pm by tpowell1830 »
PEACE===>T
 
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Offline JohanH

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Re: Building a DIY defibrillator in an emergency,
« Reply #19 on: September 25, 2023, 03:55:45 pm »

2000uF at 500V is rather large and might make it unfeasible right there,  that's not going to be easy to find in random household devices.


I thought everyone had them in a box somewhere...
 
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Offline Wallace Gasiewicz

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Re: Building a DIY defibrillator in an emergency,
« Reply #20 on: September 25, 2023, 10:45:45 pm »
Someone brought this thread back to life.I do have a MacGiver defibrillator in the house, I just did not realize it ....How about 700V on the plates of a 100 watt amplifier? Like the old Yeasu 101 or the Kenwood 520 or even the old Drakes and Hallicrafter radios?Probably enough juice, just be careful to zap with the DC and not with transmit turned on.Certainly this is not a common household device, but some of you have one.
Or even the volts on the old CRTs although this is very high voltage.
By the way, I am not advocating anyone actually try this.
« Last Edit: September 25, 2023, 10:49:14 pm by Wallace Gasiewicz »
 

Offline amyk

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Re: Building a DIY defibrillator in an emergency,
« Reply #21 on: September 26, 2023, 12:32:47 am »
Someone brought this thread back to life.
Pun intended? ;)

mikeselectricstuff has a few defibrillator teardowns on his channel. I remember one had schematics too.
 

Offline Andy Chee

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Re: Building a DIY defibrillator in an emergency,
« Reply #22 on: September 26, 2023, 03:34:21 am »
Instead of a defibrillator, perhaps a chest compression machine would be an easier contraption to build?



 

Online SiliconWizard

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Re: Building a DIY defibrillator in an emergency,
« Reply #23 on: September 26, 2023, 03:57:52 am »
Instead of a defibrillator, perhaps a chest compression machine would be an easier contraption to build?

In sincerely doubt it.
 

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Re: Building a DIY defibrillator in an emergency,
« Reply #24 on: September 26, 2023, 08:29:42 am »
Having worked at an industry leading company that made implantable defibrillators, I have to say that there is no way that you can be sure that fibrillation is the cause of the patient's "medical event" without observing the heart rhythm with special instruments.
Like an oscilloscope ?
Wonder where an EE would find one of those.  :-DD
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