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Comment by jandrese | Hacker News Reader

I'm guessing the technology would need to improve a bit before that becomes a possibility. It needs to be made reliable enough to not require an operator monitoring it 24/7. Probably built into a wheelchair.

What would be really amazing is if we could replace defibrillators with these in stores, malls, etc... Instead of trying to restart someone's heart you have a system that's simple enough that a layperson can slap on a dying person to keep them alive while the ambulance arrives. Maybe in the form of a cuff that you clamp over someone's wrist that can use computer vision to identify veins and automatically insert the needles and run the machine. Too complex to be affordable with today's tech, but something that could definitely be possible in my lifetime I think.

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> Maybe in the form of a cuff that you clamp over someone's wrist that can use computer vision to identify veins and automatically insert the needles and run the machine.

There's a reason they put the lines in the femoral vessels - these cannulas are like hosepipes - you need to access the large vessels to get sufficient blood flow through the whole circulation.

But if you're going to have 1 machine, you need to build it big enough to get enough flow for recovery. And once you install that hosepipe, why bother changing.

The amount of flow needed to only sustain someone that hasn't been severely deoxygenated must be a lot less.

A smaller system might be able to initially infuse an oxygen-carrying booster (as Tour de France cyclists do) to get away with lower flow rates.

Actually, reducing it much while keeping the current functioning principle would be difficult.

ECMO not only oxygenates, but pumps to assist the heart. Red blood cells would not resist infusion through small cannulas at high speed. Hemolysis already is a problem with the current size femoral cannulas.

So if what you're after is flow, size is a severe limitation.

Indeed - see Poiseuilles equation [https://www.openanesthesia.org/poiseuilles_law_iv_fluids/]

Blood is non Newtonian. Poiseuilles doesn't really apply.

I'm aware that's what's taught in med school, though. At the maroscopic level, it works ok.

Remember that the system also needs to remove CO2.

Severe hypercapnia symptoms are bad.

During a full on cardiac arrest, even getting a small trickle of oxygen to the brain for a few extra minutes can be life altering.

During a cardiac arrest the primary problem is a pump failure - blood is not flowing through the vasculature. A trickle of oxygen into the wrist will not help if the blood is not being circulated.

Automated catheter insertion is one of those problems that seems simple to solve, but really isn't.

What you describe only exists in very limited form in research labs.

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