Ventilator (2023 Update)

You are thinking about a patient that is "intubated". Many uses of lung ventilators do not presume intubation; a face mask is sufficient.

I do not know whether intubation would be required with a typical coronavirus patient.

Modern ventilators are versatile, subtle, expensive and scarce.

Early ventilators were crude, cheap and simple. I do not know what might /sufficient/ for /some/ coronavirus patients

You certainly don't provide pure O2 - that would destroy the lung tissue. But higher than normal O2 percent is fine, as long as it is controlled.

And quite simply, a CPAP ventilator works by having a /small/ constant positive air pressure. Enough to help, not enough to cause damage.

The principle of this kind of ventilator is not difficult - making sure it is properly regulated, and knowing the right values to regulate at, are the hard parts, and the reason why home-made junk is likely to be a very bad idea.

Home brew by people who know what they are doing could be fine. But most people don't know what they are doing, and that's where you get the risks.

What else is a few years of appropriate medical training. You just don't ho ok people up to a pump and leave them. These machines are instrumented to m ake several vital readings for a reason. The operation needs to be monitore d by an acute care respiratory therapist. You could just as easily kill the patient as save them. And you need additional lab grade instruments to sup plement the ventilator.

Clifford, I've plowed through all my old files unsuccessfully looking for my copy, but in 2016 I was able to download the operator and theory of operation manual for a popular ventilator directly from the manufacturer's site.

I think you'd find it a comprehensive treatment.

Alas, I've been through multiple computers, notebooks & tablets and I can't find my download, otherwise I'd point you straight to it.

Cheers, James Arthur

Just a sketch of the systems / function --

o fail-safe battery backup

o measure volume inspired/expired, pressure o modes: force respiration rate, or detect & assist patient breathing effort o monitor patient's 02 saturation o alarm, for various out-of-bounds conditions

I've not seen masks used in the ICU; all the vents I saw required intubation, with an inflatable balloon used to seal the tube in the patient's airway.

This page is a decent start...

Here's the manual for a portable unit:

Note that it is *illegal* to manufacture, sell, or use w/o FDA approval.

HTH, James Arthur

James, thanks.

"Illegal" in the USA has (for decades) been under the control of a cartel of medical, legal and insurance industries which has deprived US citizens of the basic affordable health care that's standard in almost every other part of the world. That cartel must be broken, and this is quite possibly the trigger to do it (though ventilators are probably not the first brick to be removed from the wall).

People's appetite for risk changes when their loved ones start dying unnecessarily.

CH.

There are good reasons for the law controlling the sale of medical devices.

The US medical industry isn't one of those reasons. "Cartel" isn't inappropriate.

Change cause (the medical cartels) not the effect (expensive equipment and treatment)

Have you made any progress in your quest for a home made ventilator that you can share?

I've done the required research to know many of the pitfalls, and decided that I would only do it in a full-on Mad Max situation.

But yeah, I know how to do it McGuyver-style, with things I have here. It might even save someone rather than kill them.

CH

It is appropriate, but the health care workers aren't party to it.

Liability lawyers are mostly responsible (taking advantage of your hyper-individualistic politics), and then insurance companies.

Manufacturers certainly don't mind having very high barriers to entry - that's one of the factors that determine the profitability of an industry.

Strangely enough, insurance co's love big payouts, because it gives them a reason to extract and pocket more of the nation's GDP in premiums.

Cartel is exactly the right term.

CH

I don't disagree, other than to note I'm neither American nor in the US, so the politics aren't mine :)

It is a variant of Eisenhower's military-industrial complex.

Somehow I doubt James will agree.

Ahh. Ok, sorry, forgot who I was answering.

One of the key protections *must* be to prevent over-pressurizing the lungs; they're essentially bags of wet tissue-paper. And you have to ensure the previous load of air has been expelled before you dare force a new load in.

Some sort of external strap to cyclically squeeze someone's chest might simplify some of those life-and-death considerations, and also avoid the infection risks that come with intubation or masking someone who has fluid in their lungs, and is coughing up material loaded with viral and/or bacterial pneumonia pathogens.

James Arthur

Has anyone used an air bag, sort of a big blood pressure cuff, to squeeze the chest periodically and push air in and out? That, and oxygen, should help, but I haven't heard of it being done.

That would only be of use if a person can't work their diaphragm and/or chest muscles. A solution can't help if it doesn't actually address the problem. The problem is the lungs filling with fluid.

What you are suggesting is like giving CPR to someone who's heart is beating just fine.

You'd have to squeeze the stomach as well. Just squeezing the chest would just move the diaphragm down, and the ribs wouldn't like it much either.

I'd expect John Larkin to be grossly ignorant about human anatomy, but James Arthur should have known better.

Here's the result of one of the open source efforts. It uses a standard "bag" such as ambulance staff are trained to use. They require skill and judgement, but presumably have some safeguards built in.

And a book on Ventilator design:

What about the Bird Mark 8 Ventilator?

Doesn't look that complex. 3D print that enclosure, stuff inside is just "vacuum-logic", looks like. Probably some vacuum switches that would work off the shelf. Automotive?

Doesn't even need electrical power to work it runs off the O2 pressure.

These things are not a panacea, though. In Italy they've had critical care patients hooked up to proper, commercially-built and certified ventilators but these patients have still been dying - and they can't work out why.