As someone involved in manufacturing ... I'd like to know what part of GM's existing production equipment they propose to leverage in order to manufacture a completely unrelated product. They need these ventilators NOW or maybe a week or two from now. There is no way you are going to change over production equipment in order to make a completely different product that is put together in a completely different way, so it can only be something rigged up from re-purposed bits and pieces that are already in production.
Conceptual design: A centrifugal blower of appropriate pressure rating, a couple of flapper valves to switch the outlet hose from the discharge to the inlet of the blower in an alternating pattern, a little actuator of some sort to change over the flapper valves (would have to be electric - an air cylinder would require a compressed air supply), and an electrical panel with a small power supply and PLC and contactor sets to make it all work. A potential obstacle is that I don't know how you would synchronise this with the patient's natural attempts to breathe (or if you have to do that) - if the problem is that the patient can only halfheartedly breathe, you want to work "with" and never work "against" the patient's natural attempts to breathe, and I don't know how you would do that.
Something rigged up in a hurry like this will NOT have any meaningful countermeasures against component failures. It will NOT pass FMEA. It will NOT have redundant components in the event of a failure. I am sure that there are standards which apply to medical equipment ... which I am not familiar with, but almost certainly a rigged up contraption would not be in compliance. And it means that any company proposing to build something like this, would have to be protected from liability. In the USA? Good luck with that. In Europe? No CE marking for you - no declaration of conformity - can't import it. I'm sure that under the circumstances, some way of waiving some of these requirements could be arranged ... but the manufacturer has to be protected from liability after all this is over.
maybe it’s assembly of parts?