jwilson8767 / covid-19-ventilator-concept Goto Github PK

(reposting here for visibility)

Rather than 3 on/off valves, why not use 4 valves, all the same, with a "Y" connection to the pressurized air/oxygen input connecting two. Then if the open shut sequence of pairs of valves is made to be break before make, which seems readily guaranteeable if a complementary pair of valves is built as a single unit having a single rotating internal part, it would seem that there would be no need for the one way ball valves (not sure that they work anyways). Then two such dual valves could be stacked on a single keyed shaft (phased appropriately) and one has the basic 4 valve phased operation assemply for this. If driven by a stepping motor and smarts, one would have precise control of duration of each phase. A dumb constant speed motor, perhaps with a few speed options, would give just a few settings for overall periodicity, with the various phase durations set by the internals of the valves (perhaps with build variants). Anyways... time to let a mechanical engineer and a medical professional comment as to whether something so dead simple is actually helpful... Would be nice to imagine a LEGO factory churning out millions of what is needed in just a day or two, if plastic parts would suffice.
-- Kevin Huscroft on Agorize

Air supply may be delivered via any compressed air source, and filter either pre-ventilator or post-ventilator. I imagine that, in a pinch, portable air compressors (the kind that run air tools) could be used, perhaps in a bank of multiple compressors to provide redundancy / overcome duty cycle limitations. I read somewhere that 50PSI was required for inspiration, which sounds high to me, but regardless this concept should be able to be used for any pressure given the right materials.

Now that I've said all that, someone please tell me where I'm wrong.

(reposting this here for visibility)

I would suggest making the motor a third component completely, with just a standard form of drive shaft coming out of the valve box and a set of predrilled attachment points (metric & english) so that a variety of motors can be attached, based on what can readily be manufactured/improvised locally. Then some manfacturers can make valve boxes and others can adapt whatever motors they are already setup to produce to be attached to any such valve box, if the attachment is standardized.
Or instead of shaft protruding from valve box, have an opening where attached motor shaft with its own cog inserts into the valve box to engage internal cog when assembled, with size & offset of motor cog providing some gear ratio flexibility. Would be nice to hear from a medical person whether something this crude would be helpful in the worst case...
-- Kevin Huscroft on Agorize

(reposted for visibility from Neil Schipper on Agorize)

A spec for "Rapidly Manufactured Ventilator System (RMVS)" has been released by UK MHRA (their med/healthcare products regulatory agency). It is of course a different spec. It is longer though not terribly long (9 pages). More importantly, it has been put together with considerable care, and it may reduce confusion for some people here trying to find their footing. It explains operating modes quite well, is quite clear about "need to have", "nice to have" and "even nicer to have", is quite clear about tidal volumes, inh-exh ratios, electrical & oxygen supply issues, what needs to be displayed, operator interaction, and has a nice glossary.
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/874279/RMVS001_Rapidly_Manufactured_Ventilator_Specification__PDF.pdf

Every patient needs a unique set of parameters (rate/pressures/air volume, etc.), a single design for simultaneous multiple patients is complex and beyond the scope.
-- Nam Ly on Agorize

I think this concept could be adapted for a single patient if the rotating half-circle valves were instead arranged such that there was a gap (for expiration) between inspiration from chamber A and chamber B, with air feeding to the (single) patient using either chamber.

One could optionally add contact switches at each end of the chamber (component A) and that get hit each time a valve completes a rotation inside the valve box. Such switches would create momentary closures. These could then be wired to a very simple circuit, perhaps battery powered, that turns on a light and makes a sound (i.e. an alarm) if any of these switches don't close for a period of time. This would just require very few and simple electronic components. I.E. if the unit stops due to loss of pressurized feed, loss of motor power, or any kind of jam or tube disconnection, then an alarm happens.
-- Kevin Huscroft on Agorize

Love this idea, would be super simple to implement and may fulfill some of the need for feedback. Additionally, I believe an O2 sensor should be included on the patient expiration feed(s).

I also want to repost this comment from a related Reddit thread that emphasizes the importance of sensors:

I've been an ICU nurse for 20+ years. Mechanical ventilation is an extremely complex process. Sure, there are very simple machines that can provide basic ventilation ( Here's an example of a simple pneumatic ventilator ) but in the setting of serious illness and and ARDS I'd hate to rely on a primitive machine. Ventilation isn't just delivering a breath to a patient, it is also vital that the machine can provide measurements and feedback to allow practitioners to evaluate how the lung is responding to treatment (pressures, volumes, compliance.) You're pushing positive pressure into a balloon and the balloon is sick. It's hard to do.
-- u/johnnycourage on Reddit