I actually have yet to hear any reports of improvised ventilators being used outside of ventilating multiple patients from a single ventilator. A big reason is that doctors and nurses simply aren't trained to use improvised devices in a way they can trust to be safe.

First, do no harm.

They describe such usages in the first sentence of the article. Mt. Sinai researchers are actively working on converting BiPAP machines into ventilators.