So, there was a research paper published in 2019 that intended to create an Open-Source CPAP machine for low-income countries who are often unable to afford the high cost of traditional CPAP machines, and they published their hardware specifications and code: http://www.ub.edu/biofisica/dwn/CPAP.pdf. This is a great start by a handful of talented individuals, and it'd be cool to see people take this even further.

hey @dabell me too! if not, lets start it up again! Im currently hacking my old Philips system one. I've had great success with backpacking with LiPo batteries when I take the humidifier off. My next goal is to actually tear it down and minimize the weight. Might be feasible to do my own embedded system too.

Is there any activity on this project? I'm interested in building something small/simple/low-power to facilitate off-grid travel/hiking while continuing to breath at night. 

My Airsense10 blower motor finally died just past the 2year warranty. I found a replacement brand new in box for $120 on Ebay. It went in and works perfectly, so now I have the old blower to dissect. I will post pictures of this and then I'll 3D model the impellers( there's 2 front and back.) I'll change the design so that the motor is external to the overall airflow. Like I predicted below, when the motor gave up, I had the lovely experience of breathing the hot coil varnish of this lovely flow-thru design. Must have designed been from a jet engine perspective, but not cool breathing the motor dreggs. Of note: don't use the ozone cleaners on this model, it will eat the bearings which is why I think if failed ultimately. -Lee

My Resmed airsense10 cpap blower died finally just after the 2yr warranty. I took it apart to see how it was made. The air blows from the intake,1st impeller, across the motor coils then 2nd impeller then out. if you have this type, DO NOT run one of those ozone cleaner though it, or alcohol on the input filter, like I did. The ball bearings and races on the output side disintegrated.

About 1 year into it, my motor started to whine, so I got some food grade silicone oil and drilled tiny holes so I could oil the bearings.

The whine went away for about a year till now. After the dissection, the oil was all brown and gooey. I fairly sure the ozone started the whine adversely impacting the bearings. 

Found a new in box replacement on ebay. (Very hard to find these, often listed for $100 used.)

Going to model the impellers (identical) sometime and make an RC motor replacement and somehow keep the motor out of the breathing airflow.
recap: if you cpap blower motor is in the airflow: DONOT run one of those ozone cleaner thought it, or alcohol on the input filter, like I did.

There is a real need for cpap machines all over the world to treat covid 19 patients (especially in third world countries).  I am in touch with 150 engineers trying to build simple ventilators, who now may shift their efforts to building cpap devices because of poor covid patient survival on ventilators.  I have also designed a method to modify the cpap mask and add a hepa filter to the cpap expired air (which if not filtered will aerosolizes the virus and endanger medical support staff). You can go to you tube, type "larrygessman" into the search engine to see my ventilator and cpap filtering designs.  Please email me at larrygessman@gmail.com if interested in building cpap devices for treatment of covid 19 patients. 

Just a note on how not to design a thing: Resmed Airsense 10. The motor is an inline 3phase brushelss turbine/impeller that is enclosed in such a way that the air hits the impeller, runs thru the body of the motor and out. So basically as this motor ages, you breath in any coil enamel or motor detritus etc. My motor developed a bearing whine after about 1 year of operation. I lubed it with miniscule amount of a fine silicone "food grade" lubricant( amazon) using a syringe. This worked for about a month, then the whine came back. 

This lube can't be good for you to breath in quantity, but a necessary evil. I'm not going to re-lube it.

I don't know what the designer was thinking, but any benefit of having the motor cooled in the airflow is no benefit to the user. I also disabled the sms( w/ sim card) cell phone module it has inside, that anyone can hack.

Also the water humidifier tank is a 3 piece nightmare that breaks after a few month and leaks water all over your night table. The lower section is made of a shallow stainless pan molded with a plastic reservoir. The water level is several times the height of the metal pan, so it depends on some shoddy sealing that fails too often. End of rant. -Lee

Look for Micro Air pressure fans on Alibaba:

https://www.alibaba.com/product-detail/Micro-6V-12V-24V-DC-brush_1800584447.html?spm=a2700.7724857.normalList.13.73e57ac9nGnJEy&s=p

Those are limited to about 10 l/min. For CPAP we need more like 100 l/min at maybe 30 cmh2o.

Like this https://www.mouser.com/ProductDetail/Delta-Electronics/BFN0724SS-01?qs=%2Fha2pyFaduhoBbNUZXQEnT%252BfkOwgWh8oTsxbKb7%2F2YSusIzAt%2Fzfeg%3D%3D

I like this: 

Dremel turbine by Landru

https://www.thingiverse.com/thing:13188

Dremel Turbine Video:

https://www.youtube.com/watch?v=Xxc1hbhf9cg

The files can easily be modified for a brushless RC motor.

The video look promising in pressure and flow....

20180611 Lee Studley

This one might be comparable:

https://www.amazon.com/Greenworks-24102-Variable-Sweeper-Battery/dp/B00860RKHW/ref=sr_1_1?s=lawn-garden&ie=UTF8&qid=1526592733&sr=1-1&keywords=Cordless+Leaf+Blower&refinements=p_n_feature_keywords_browse-bin%3A2831320011#customerReviews

I think an RC 3 phase brushless motor, rc ESC motor drive, Arduino Uno or similar( to close the loop and display information), and a 3D printed impeller and body, etc could work well as the next step.

The controller should implement a compatible log of data format to these open source programs for data analysis of the cpap function:

 https://sourceforge.net/projects/onkor/

-or- 

https://gitlab.com/sleepyhead/sleepyhead-code

BR,

Lee Studley

Thank you, you're doing excellent work! I would not have thought of trying leaf blowers. (They're not very common in South Africa.)

I have also not thought of interfacing with analysis software: Sleepyhead would be my primary choice, because I've used it before. 

Cool! I'll look more into that one then :-)

LOG:UPDATE:20180517:

I bought a leaf blower that looked small enough and highly hackable:https://www.amazon.com/gp/product/B01N1ES69P/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

It was on sale for $39, but seems to now be ~$60. I found it produces very constant pressure w/o feedback into the control loop at 9v-11vdc. I found and will order a new sensor at mouser from Honeywell that is inexpensive and new:  https://www.mouser.com/ProductDetail/Honeywell/MPRLN0300YG00001A?qs=sGAEpiMZZMvWgbUE6GM3OavE8y1%252bdF%2fwhYe9lyQzJGamIIJFxPMqcg%3d%3d

I've used the open loop setup for about 2 weeks now while waiting for my prescribed unit and it is awesome. The only downside has been lack of humidity. I tried an impromptu mason jar with a custom 2 port lid with 1/2" pvc fitting: an in and out port, 1/2 filled with water( fail:not enough moisture). Then I added a wicking tube ( fail:not enough moisture), then I added a wicking "screen curtain" made of medical gauze( fail:not enough moisture), so tonight I'll put a hole in the side of the bucket and run a ultrasonic humidifier so a percentage gets sucked in the input of the blower. Note: I live in AZ where its very dry anyway.

I figured I could experiment with voltages for speeds. I made a cpap hose adapter for the hose to fit 1/2 length of one of the blower tubes as an air reservoir.
I got the mask, hoses, and blower from amazon. I found it works really well and surprisingly constant pressure at ~10volts all night. I need to make a manometer also as a reference: 

Andrew Senske, President CPAP-Supply.com did a great blog on how to do this:

http://www.cpap-supply.com/Articles.asp?ID=132

I put it all in a home depot bucket with a towel as an impromptu air filter, then in a cardboard box to keep the sound low. Over all it works well. and I've slept much better like I remember doing in years back:

Points 4 and 5 could be negated initially, as you could use commercial products to start with. They are not cheap (£100ish) but they are at least a quarter of the price of a CPAP and fifth of the cost of an APAP.

Once the CPAP design is done then you could look to designing a cheaper mask or nasal pillows.

I agree. Tube and mask are not priorities, but if someone wants to start work on that, it could one day start saving patients money. The masks wear out, and an affordable replacement would help. 

the tubes can be bought cheaply on eBay. A mask with a replaceable seal like the resmed quattro fx would be an idea to keep cost of consumables down.

Can't buy on eBay in Africa :-(

Brilliant idea, Stuart!

Here's an article that shows what a CPAP machine looks like on the inside. 

http://www.cpap-supply.com/Articles.asp?ID=134

Our's doesn't have to look like that.

Can anyone volunteer and give sketches for how a Cpap machine works? I can provide 3D models that are 3D printable or laser cut. CPAP machines are quite expensive and itnwould go a long way to make one inexpensively.

I've added a block diagram to the details above.