Ask HN: Is anyone working on open source DIY artificial ventilators/respirators?

There's a possibility the spread of COVID-19 leads to a lot of people needing help to breathe and not enough equipment.

Is anyone working on easy-to-build DIY versions?

What are the requirements?

- Made of ubiquitous simple components

- Provides "clean" air

- What flow rate?

- What cadence?

- What feedback mechanisms? Can it (or an operator) close the loop with cheap fingertip O2 sensors?

What's the starting point - designs from the 1800s/1900s?