Electronics > Projects, Designs, and Technical Stuff

Medical Ventilator Design

<< < (7/8) > >>

Gandalf_Sr:
Guys,

We know that, in the land of litigation (aka USA) that manufacturers of healthcare equipment carry massive insurance overheads which they pass on to their customers in the form of extra equipment cost.  Now imagine that we are in a Wild West situation where people in your town are dying for the lack ventilators and you are the only engineer - that's where the USA seems to be going over the next month or 2.

Enginerding has PMd me with information that is exactly what I was trying to do and his/her work is way ahead of what I could ever do so I'm following that rather than trying to compete.  The main thread of interest is here, scroll down a little bit to find Known Open-Source Projects: under which you'll find a link to a summary of all known (to the writer) efforts in the respect of low cost ventilators; I particularly liked the suggestion of making a PAPR (powered air purifying respirator) which is mentioned in this github thread that would be used to protect the care givers rather than their patients with Covid-19

Kilo Tango:
Some thoughts on the Ventilator project.

Motors, I would avoid brushless model motors, they are built down to a price, not up to a spec. I doubt they could run continuously for long without wearing out. I wonder if Dyson is going to use a standard hoover motor in his ?, I would worry about reliability. UK Gov spec says run for 14 days plus, that's 336 hrs. The average hoover is used once a week for 20mins, and fails after 3 years, that's 52 hrs.

I would stick with standard, well engineered, Industrial grade blower fans. They last for a long time, some are still going after 10 years plus.

Shame we couldn't use a computer fan, they generally run for years without problems, modify a standard cooling fan ?.

Battery, I would choose lead acid, its a mature technology been around for 30+ years so no surprises. easily available in quantity if you stick to burglar alarm sizes. Li-ion potentially better, however charging requirements are complicated, and they still go off with a bang if not treated properly. Also sourcing good quality ones in the 1000's would be difficult.

Standard compressor - no they use oil to lubricate the pump, and put oil mist into the air stream. It tastes crap (! ) and would need a lot of filtering to clear it. However maybe those used to recharge aqualungs would do ?, could they run 24/7, or use a reservoir system and feed 10 people at once ?.

Reliability and notifying faults. Well start with a hardware watchdog system, a retriggerable monostable that has to be reset every sec or so else it causes a hardware reset and sounds the alarm, will ensure the processor doesn't fall asleep. Next every so often the program checks that all sensors are giving allowable values. I remember one 3D printer trying to heat the bed of an unattended printer, nearly caused a fire cause the sensor cable had broken. You could even use a 2nd processor to keep a check on things and if it dissagreed with the current machine state it could also sound the alarm.

I think the Medtronics documents are very useful. Not as a set of DIY build it yourself plans, everyone builds one in their garage and dashes down the hospital with it, but all the clever stuff, the thinking about how it has to work is all done for us. Basically al we got to do is engineer something to meet their spec, and we would be home free, no need to spend years verifying performance is what is needed.

Thoughts ?

profdc9:
Looking around at some CPAP designs, it looks like brushless motors are used in those for the blowers.

Perhaps a 3-D printed shell enclosure and internal wheel could be designed around a common brushless motor.  If they're good enough for CPAP perhaps they are good enough for an improvised ventilator.  A method of pressure regulation could be to actively commutate the motor to vary its speed/torque.  Perhaps look at a HVAC fan?

max_torque:
Once again, people are missing the actual problem!

The problem is NOT designing a new ventilator, the problem is designing a new ventiliator of which you can make lets say 50,000 in less than 3 weeks.

So what motor you want to use is not governed by any engineering factor, no it's governed by "who has 50,000 motors on the shelf i can get delivered to me tomorrow"

This is a "Buying" problem, not an "engineering" problem.........

AndyC_772:
For such a unique specification, and set of circumstances, the NHS spec is missing some really important information:

- estimated quantity required
- time scale for delivery
- details of regulatory approvals that will be required
- (if they're trying to attract manufacturers that aren't usually in the business of designing life critical medical equipment): some kind of guarantee or other reasonable assurance that, when very sick people inevitably die whilst attached to these machines, the manufacturer won't be held liable.

Without that information, the technical requirements are moot. Nobody capable of actually developing a viable product and bringing it to mass production would do so without it.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod