100% this. I'd been curious why I wasn't seeing discussion of negative pressure ventilators, also known as iron lungs, but more recent commentary that I've seen

100% this. I'd been curious why I wasn't seeing discussion of negative pressure ventilators, also known as iron lungs, but more recent commentary that I've seen notes that the positive pressure is needed in part to force oxygen into the blood. Apparently with Coronavirus sick lungs are wet lungs and wet lungs don't work as well. That would imply that you also are going to need a supply of oxygen at a higher concentration than in the air which would imply either an oxygen generator or reliable tank based supply system. Other discussions I saw excluded concerns about significantly increased volume of aerosolized infectious droplets from improperly used ventilators.