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How to find components with certain specifications

okaythanksbud

Sep 26, 2023
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for my schools capstone project im building a low cost bulb cpap machine, and this has proven to be much more difficult than I expected. What I am picturing right now is an air pump that pushes air through a tube with its end submerged in a certain amount of water (depending on desired pressure), with an outlet for the patient interface in between. The other main feature I want this to have is a pressure relief valve in case of malfunction to prevent buildup of too much pressure. There's other things I want to add, but a good pressure generator and functional pressure relief valve are my primary concern rn. One of the hardest parts has been finding components that meet the given specifications, and I thought this would be a good place to ask about this.

Here's some examples:

Air compressor/flow generator:
Flow rate of 6-8lpm, pressures of 2cmH2O to ~20cmH2O
I've seen this is typically an inductive diaphragm pump (here) but cannot find any products online that match this. And every other diaphragm pump I find has specifications that exceed the ones stated above drastically. I've found blower fans (WM7040) that meet these specifications but am kind of unsure about using this. I can't tell if I'm missing something--is it possible to use a stronger blower and adjust it to give a lower pressure/flow rate than the value specified? Am I looking in the wrong places?

Pressure relief valve:
Maintains pressures lower than ~20-25cmH2O
This I can't find anywhere. Most pressure relief valves I can find are for like 1 PSI at the very least, with most seeming to be around 25+ PSI, which is way, wayyy too much for my purposes. I've found some adjustable ones around this range but Id rather have something more accurate that's set at a single pressure.

So where exactly can I find these components? Do I need to do something like reach out to a company to get a custom valve/pump? I feel like this must be easier than its been for me but so far Im coming up empty handed. Any help would be appreciated.
 

Delta Prime

Jul 29, 2020
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I feel like this must be easier than its been for me but so far Im coming up empty handed

You really want to assist those with sleep apnea; you're dealing with the human respiratory system.
Are you medical student?
The U.S. Food and Drug Administration (FDA) has issued a final rule, “Classification of the Positive Airway Pressure Delivery System,” effective Oct. 19, 2018, that reclassifies the positive airway pressure (PAP) delivery system, moving it from Class III into Class II. PAP delivery systems continue to be for prescription use only.
Darn it sorry about the font stupid phone
 
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okaythanksbud

Sep 26, 2023
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You really want to assist those with sleep apnea; you're dealing with the human respiratory system.
Are you medical student?
The U.S. Food and Drug Administration (FDA) has issued a final rule, “Classification of the Positive Airway Pressure Delivery System,” effective Oct. 19, 2018, that reclassifies the positive airway pressure (PAP) delivery system, moving it from Class III into Class II. PAP delivery systems continue to be for prescription use only.
This isn't an actual product--its an undergrad capstone project. Its for use in neonates who dont respond to basic treatment and need constant pressure to keep their lungs open. I dont think its supposed to be viable for actual patient use but should have some sort of "novel" design (though I am pretty sure any design that achieves the purpose of the project will suffice). Regardless, I am just looking for these components (or some guidance on how to find/obtain them), I'm going to try to consult with someone more knowledgeable before finalizing what components I will order to make sure they're suitable for use in a bcpap
 

Delta Prime

Jul 29, 2020
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Well if it was me I would start with asking a pediatrician I'm pretty sure they have preemies Using exactly what you have just described.
I know you're trying to do a proof of concept I would try googling
Neonatal CPAP Device components . Manufacturers distributors. Go from there.
 
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Martaine2005

May 12, 2015
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I would think a call to a pneumatics company that deals with air compressors would be able to help.
I used to have a miniature fully functional air compressor. Approximately 6” x 2” with a 12” air line hose. It was built by Alpha pneumatics (I believe) as a rep’s example piece.

Martin
 

kellys_eye

Jun 25, 2010
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I would have thought using a reservoir of air controlled through a valve/pressure regulator would be the way to go. This eliminates the requirement for accurate control of the motor and puts the emphasis on the valve/regulator which is far easier to control and has many more versions available.
 

okaythanksbud

Sep 26, 2023
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I would have thought using a reservoir of air controlled through a valve/pressure regulator would be the way to go. This eliminates the requirement for accurate control of the motor and puts the emphasis on the valve/regulator which is far easier to control and has many more versions available.
Do you know if there's such a thing as an electrically controlled flow regulator? If there is this suggestion would be massively helpful as I need to create an oxygen blender for the project and if I could control the flow of air from the reservoir this could help solve the problem of the flow generator and oxygen blender
 

okaythanksbud

Sep 26, 2023
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I would have thought using a reservoir of air controlled through a valve/pressure regulator would be the way to go. This eliminates the requirement for accurate control of the motor and puts the emphasis on the valve/regulator which is far easier to control and has many more versions available.
Im also curious: just based off the fact that the system is essentially just a blower pushing air through a tube that ends in water, in theory couldn't a blower supplying any pressure be used? The pressure inside the tubing shouldn't be able to build up much since it will just get pushed out
 

Harald Kapp

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The pressure inside the tubing shouldn't be able to build up much since it will just get pushed out
The gas pressure will - for all practical purposes - be the same all over the length of the tube (unless there are changes in the tube's diameter, see note below).
If there were pressure differences between start and end of the tube, this would force gas into or out of the tube until an equilibrium is achieved,
For long and narrow tubes you'll have to account for the friction of the gas on the tube's walls, too.


Note. Artificial restrictions in a tube's diameter are used to create differences in pressure depending on the flow rate of the gas. These differences in turn are used to determine the flow rate, see e.g. this article.
 
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