There are a couple of interesting videos on YouTube presented by Dr.Charlene Babcock in Detroit.
In one she demonstrates ("suggests", really) how - in dire need - to connect four patients to a single ventilator; in the other she shows how to set up a Respironics V60 BiPAP (NIPPV, really) machine for use as an invasive ventilator.
Note the terminology she uses:- "Off Label".
