A proposal for a low cost CPAP device
Caveat: if anyone reading this sees a potential problem with the approach or that it’s simply bad medical practice please let me know and I’ll take the post down.
Last year I created a simple device to help with high altitude sickness in an emergency, but progressed it only to a demo. Now, being in the middle of a pandemic with a shortage of ventilators I’m just putting it up as an idea to help in some circumstances.
Critical cases of COVID-19 see patients suffer from ARDS that requires mechanical ventilation. For patients with milder symptoms who need help with breathing it has been proposed that Continuous Airway Pressure (CPAP) or BiPAP devices might help, as discussed here and requested for here. Perhaps my altitude idea might work and be low cost enough to be used widely?
The basic components are simple:
- A re-breathing mask and tube
- A flexible air tight bag connected to the tube, big enough for a single breath
- A standard computer fan driven by 12v or 5v power supply.
In my test these were:
When assembled:
The fan pushes normal air into the bag, increasing the pressure relative to the surrounding air. The increase will be related to the speed (and size) of the fan compared to the size of the bag itself. I used an 8cm fan as the larger the fan the more efficient it is. The pressure in the bag will increase until the force pushing air out matches the force pushing in, as the bag remains open this will stop the pressure rising too high.
The patient breathes in from the bag. Breathing out is through one-way valves in the mask as the bag will be re-inflating, so air pressure will be temporarily lowered to make this out breath easier.
The power in my example was via USB, so it can use mains power or a small battery pack which should last several hours.
My open questions to anyone are:
- Would the air pressure be raised enough to be useful?
- How high does the pressure get raised?
- Is it hygienic enough?
- How much would it cost? My version cost about £11 to make, but in bulk would be cheaper.
If this is of interest please feel free to use. As I said before, if I’ve suggested something dangerous please say so and I’ll remove, I certainly don’t want to make things worse.
