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Super simple low cost ZERO SOFTWARE ventilator controller
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wraper:

--- Quote from: Edwin G. Pettis on April 14, 2020, 01:02:21 am ---
--- Quote from: drussell on April 14, 2020, 12:27:57 am ---timer ≠ ventilator controller

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If you had taken the time to actually read and understand the project first before commenting, you would have seen that it actually works, it's simple and reliable and would work in a pinch until the real thing was available, that is all it is.  A ventilator doesn't have to have a CPU and a hundred bells and whistles to work, check out the older models that didn't have CPUs or even electronics, just a mechanical machine to do the work and that likely wasn't as reliable as this circuit and cost a lot more.....so where's the beef?

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I've read it and completely agree with drussell. Timer is not a ventilator controller. I guess it's trendy to talk "ventilator" about just anything. Medical ventilator is about supplying particular pressure to lungs, not turning air pump on/off.
wraper:

--- Quote from: MisterDiodes on April 14, 2020, 12:39:02 am ---Please see the University of Florida project.  It's an EMERGENCY ventilator design.

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Looking into attached documents it's about how to kill patient very painfully by forced ventilation of lungs. It's not how medical ventilator works. Real ventilators either supply pressure above ambient to ease lung operation or if pressure is modulated, they sync it with lung operation, not force air into lungs. What you posted here is a torture device if used as ventilator controller.
floobydust:
It would be fine with a ventilator bag as you can't overfill the lungs and damage them, but a bit dangerous with pumps. Older, simple ventilator designs used mechanical pressure relief valves and regulators, and lots of solenoids.
Ideally it would have a supervisor portion that looks at pressure and the pressure pulse to detect an open mask or hose; another op-amp and pressure transducer. These are used: Amphenol NovaSensor NPA Series Surface-Mount Pressure Sensors

Many cutesy 3D designs for ventilators are here: https://grabcad.com/library
drussell:
The basics are reasonably well covered in this video:

MisterDiodes:
DRussel - I think you need to reconsider just a little.  I 100% agree - if you could put flow controller and solenoid valves and pressure sensors and ran the thing on a Core-i7 PLC that would be great.  I know that.

The problem is - in the spirit of an emergency device you can't use up parts that are used in any real ventilator.   Want a pressure sensor to sense the actual pressure on inhalation?  Great!! Except:  Good luck finding any medically approved sensors right now - for instance the popular medical breather range 0 - 0.58psi (0-40cm H2O) sensors are pretty hard to get right now, even if you wanted one.  They are generally already bought and vendors like Honeywell / NXP etc. are months behind, busy filling orders for the big players.  Waiting months might not be an option for some remote communities.

The University of Florida project can be built with simple mechanical means for max pressure and PEEP (Positive End Expiratory Pressure).  For instance PEEP can be controlled with nothing more than an airway-connected tube inserted in a bucket of water - with the end of the tube at the desired cm distance pressure below the surface of the water, and the patient exhales against that steady pressure that is enough to create bubble flow at the bottom of the pipe.  A second tube is set 40cm below the water surface, and that's the overall system safety pressure.  An anti-asphyxiation valve is nothing more than a ping-pong ball trapped in a pipe so that as long as positive pressure applied from the system it seals.  If the system inline pressure fails and the patient inhales, the ball lifts off the seal and allows normal airflow - you never want a vacuum in the patient lines.  And so on.  Don't think solenoids and lots of complex valving -  Think about how to do it with what is available.

Low pressure bardon tube gauges (round dial) can be used as long as they are available - and in absence of that you switch over to a U-shaped clear tube stapled to the wall filled with an appropriate amount of colored water with a measuring tape stuck along side.  There's your very accurate manometer tube gauge.

Does the patient need warm humidifed air?  That's easily done with a common CPAP style water tank and heated airway tube (Lots in supply for CPAP machines) - in a pinch a resistive warmer in the airline can be added along with an airstone bubbler along the route.  Even a repurposed aquarium pump and airstone can work.

In all cases what closes the feedback loop on a timer-controlled emergency ventilator is the attending nurse keeping an eye on the patient at all times.

Is it ideal?  Of course not.

But in the spirit of an emergency, remember that something like University of Florida project will be FDA approved ONLY IF there are no real ventilators available.

If you don't want to call it a "Ventilator" controller, that's fine.  The schematic specifically says it isn't for medical use - because I had you in mind <Laughing>.  Just call it a low power timer/ pulser for AC loads.  I simply repurposed an existing circuit and applied proper resistor values to make a way to power a valve on and off, and that valve happened mounted on some PVC pipe and a bucket of water contraption that is saving someone's life.

Let's hope none of us ever has to use it!! 

In the meantime enjoy the circuit as a fun way to teach someone about how 555 timers and comparators work.  Make a Halloween decoration.  Make a flashing light for your driveway.  Put a heavy relay on it and cycle that million volt Tesla coil in the front yard.  That would be cool!

HEY-  You can even modify the circuit to use a 556 timer.  That way if you can mount a simple breath sensor switch on the inhalation line and use the second timer as a classic missing pulse detector to trigger an alarm!

Lots of ways to do it for sure.  Not one right way.

If any open-source ventilator saves a life in a situation where a real ventilator wasn't available - well then it's a great design, right?  By whatever name you call it.








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