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Building a DIY defibrillator in an emergency,
Psi:
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,
jogri:
--- Quote ---One of the people has a medical event and their heart stops beating.
--- End quote ---
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.
Psi:
--- Quote from: jogri on April 24, 2020, 02:13:45 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).
--- End quote ---
Thanks, i think i knew that but had forgot. Have edited post.
--- Quote from: jogri on April 24, 2020, 02:13:45 pm ---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.
--- End quote ---
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.
m98:
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.
--- End quote ---
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.
Psi:
--- Quote from: m98 on April 24, 2020, 03:05:59 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.
--- End quote ---
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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