CPAP machines generate continuous positive pressures though, they assist breathing. I know they have slow ramp capabilities for comfort reasons (start off at low positive pressure when you fall asleep and then increase) but I don't think they can swing pressure fast enough to enable inhalation and exhalation.

You need: -Gas blending (relatively trivial) -A source of pressure (CPAP has this) -A way of modifying pressure up and down quickly and precisely enough to stimulate breathing (Don't think CPAP has this) -A way of measuring flow and pressure (Does CPAP have this with good time resolution? I doubt it as not required for CPAP) -A controller which uses the flow and pressure data to vary the system pressure (CPAP doesn't have the right software but presumably this is less time constrained than the others)

So I'm really not sure that you can do this with a modified CPAP machine.

BTW I'm not sure that you can print oxygen valves, maybe air valves or patient valves. High pressure inlet oxygen parts need to be oxygen compatible and many 3d printed materials may combust under those conditions.

CPAP machines technically can't but CPAP has become a generic term that also encompasses bi-level/APAP machines that can swing pressure fast enough to track inhalation/exhalation. Both mine do. They're not that old but they're not top-end either.

I don't know how many active machines are pre-APAP/BiPAP/A-Flex (there are different names for it). A comment below says 90% but this seems very high to me.

I wonder if it's possible some doctors don't realise the machines have this feature or it's importance? When I first was prescribed CPAP the machine did not come with bi-level flex enabled, it made it very hard to tolerate. I pushed through it for months but when I "cracked" the doctor-only DRM (i.e. looked up the cheat code on Google) and enabled A-Flex it instantly became way easier to handle the machine and my AHI scores were super low; big success. Doctor was quite happy with my altered configuration. I was just surprised such a basic thing hadn't been explained to me.

I suspect a lot of CPAP machines support bi-flex but it either isn't activated or could be added via a software update. I don't think you need extra components.

Oxygen valves come from here: https://learningenglish.voanews.com/a/volunteers-produce-3d-...

Very interesting, thanks. If that is the case then it may indeed simply be a software thing. Specifically for treating ARDS you need:

-High PEEP (obviously any CPAP machine can do this)

-Low plateau pressure (probably possible, that's just software)

-Low tidal volume and high breathing rate. Breathing rate is just a cycling variable so should be software only issue. Managing low tidal volume will require the machines to have a flow sensor. Do you know if any of your machines do? If so, then this is likely fixable with only software.

My interpretation of that article is it must refer to the patient valve as those are one-time use (as they in contact with contaminated patient exhalations) rather than O2 inlet valves which are not disposable. Patients are breathing high-ish O2 but obviously not HP pure O2 so 3d printed is fine for that.

3D printing is useful for cases like that where due to logistics there is a temporary shortfall in local supply. I suspect that 3 months from now we are unlikely to be using those measures as global production and distribution of ventilator consumables ramp up.

Yes, they all have flow sensors. They track vast quantities of data, in fact they track and record the flow of every breath on SD card and can upload that data via Bluetooth.

There's an open source app called SleepyHead that can show you all the data in detail. It appears the maintainer burned out but the downloads are still available.

So it seems modern CPAP has all that's needed? Doctors can even monitor it remotely or via the cloud. It's intended to let clinics monitor patient progress without needing visits, so it's all pretty easy to use.

A CPAP is fixed pressure, what your thinking of is a APAP or the bilevel type of positive air-pressure machines. And there lies the problem with you're miniumum feature set; not all *PAPs are fully-featured machines. Maybe only 10% or so are suitable for ventilator duty, which means they too are supply-limited

I own two CPAP machines and yes they both implement bi-level/APAP features. CPAP is a bit of an ambiguous term these days; whilst there are technical differences between them, most people call all such devices CPAP machines. For instance,

https://www.usa.philips.com/healthcare/product/HCNOCTN447/dr...

It's advertised as "CPAP & Bi-Level therapy".

To be clear, I'm talking about the ones that implement bi-level pressure. The difference is (as far as I know) primarily a matter of software; perhaps older machines can be upgraded if pricing/selling upgrades is taken out of the equation?

I've had my machines for I think a couple of years now and they were all bi-level from the start. I'm not sure when that started becoming standard or where you got that 10% figure from, you may well be right. But there are 300,000+ sleep apnea patients being treated in the UK alone. If even only 10% of them use modern machines (seems low given how much better bi-level makes it), that's still 30,000 portable ventilators available to be requisitioned at short notice. Sleep apnea patients don't have a critical need for them.