After far too long things are starting to move. The project has not been idle all this time. I have been doing a lot of research into various parts trying to find good fits for the project.
I now have a blower (scavenged from an old RemStar Classic (considered an antique these days)). I'll just be using that blower for experimentation. The plan is to find an inexpensive, readily available blower down the road.
The blower in question is a good choice because it is basically just an AC motor. So if I can get things working with it I should be able to use any ac blower of appropriate size.
I've also gotten my hands on a very nice SSR that can be controlled either by potentiometer or PWM to control the speed of the AC motor. The plan now is to use an Arduino to control the SSR via PWM, the SSR will control the speed of the AC blower and thus the pressure.
At this point I'll be using a manometer to check the pressure. In Stage 2 I'll add a pressure sensor to the mix and thus the Arduino should be able to set and maintain the correct pressure without the manometer. Of course pressure will always be verified with the manometer until we are very sure things are working correctly.
Stay tuned! Hopefully there will be news of a successful Stage 1 unit in the next few weeks.
So, Why an open CPAP machine project? You may ask.
Well allow me to explain. I was recently diagnosed with sleep apnea. No biggie, I knew it was very treatable. And so I began my journey into the world of CPAPery. The first thing I discovered is, that how it is DX'd and RX'd is very different from what I knew from years gone by.
Firstly Dx'ing it is much easier then days gone by. You just wear an oximiter for a night and from that they can get an idea of Yes or No and roughly how bad, (what your AHI index roughly is). It is what came after this that surprised me. In days gone by, one would go in to hospital for a "sleep study" where they would hook you up to a bunch of stuff and see just what was going on. It seems that because of advances in the CPAP machines this is largely no longer necessary.
What happens now is you get sent home with an advanced auto titrating (it adjusts the pressure as necessary) CPAP machine for a month. The machines usually have telemetry (cellular modem) that sends the data about what is going on with your breathing back to the service provider (Yep, not a hospital, but some type of private sleep therapy place). From all this data they can determine how you are doing on the CPAP machine and what pressure you need. They then try to sell you a CPAP machine.
The thing about this whole process that really struck me were:
The Cost of the machines.
New machines run many hundreds to over a thousand dollars. Understanding technology I can plainly see that there is NOTHING in the machine that justifies that kind of price.
Monetizing the patient.
The machines are now set up in such a way as to foster the belief in the patient that they REQUIRE the private sleep therapy provider. For a large percentage of the population this is simply not true. Once you know your pressure, you can set up your CPAP machine and you are good. Usually for years. In the old days you'd go in for a sleep study at the hospital about once every 2 years just to check that your needs hadn't changed, and the machine was functioning correctly. But guess what, the machine can tell you that now. In fact more advanced machines will automatically adjust the pressure to what you need.
But instead of going down a more honourable and IMHO professional route the Standard is now to try hide the pressure settings on the machines and give that info only to the privatized sleep centers. It goes further then that. Both the sleep centers and the machines software foster the idea that one needs to be going to the sleep center regularly. For filters, machine checks, accessories, Check-ups, etc. All of this is nothing but an attempt to monetize (IMHO rip off) the patient.
So this is why OpenCPAP.
In order to:
- Create a machine that reflects that actual cost of the parts.
- Return control to the patient.
- To put the focus back on treating the Apnea and off of making money.
Let me explain a bit of why I say that the machines can't cost what they are charging. When most non-techie people look at a CPAP the see a "magic box" that does whatever to fix their apnea.
When I look at a CPAP I see:
- A SBC (single board computer) $2-25
- A blower motor - lets say we need a really nice one $100
- A couple of sensors (pressure, humidity, temp) about $5-$15
- A heater for the humidifier $5
- Housing and plumbing $15
- Display $5
- Control buttons $5
This put us MAX around $200.00 and I'm not buying bulk or wholesale. So how on earth can a mass produced machine be worth $800-$1500?
The software you say, you forgot the magic software that runs the machines.
Again, The software in these machines isn't rocket science. As a programming problem it's pretty basic.
Lets take a quick look..
Basic 1 pressure CPAP:
- Tell the software the pressure.
- SBC spins motor at the right rate to make that pressure.
Getting just a little fancier we'll add the pressure sensor:
- Tell the SBC the desired pressure.
- SBC spins the motor, reads the sensor,
- Too high? slow a bit.
- Too Low? speed up a bit.
- Repeat last 3.
The fact is once we have the SBC and the various sensors it's basically just a matter of reading the sensors and doing the right things. Sure advanced features like ERP (expiatory pressure relief) might take a while to get right. But even that is just seeing the pressure changes caused by person, breathing in (pressure in hose drops a bit), or out (pressure in hose goes up a bit), and adjusting the pressure accordingly. NO MAGIC HERE
For all these reasons I feel that it is long past time for there to be an open hardware, freedom respecting, free software CPAP machine.
This is the blog for the OpenCPAP Project a Project to build a pressure accurate, safe, affordable, open hardware CPAP machine for everyone.
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