We have a friend who passed away about a month ago who was on a ventilator. You have to be put under for it to be installed and also for it to be removed. 

They don’t want to leave it in to long as you have trouble remembering to breath when they take it out. It is not a good experience but it is necessary in some circumstances. Our friend had lung issues and when they removed the ventilator he fought hard to get enough oxygen but wasn’t able to. 

I am not sure any off that helped but that is all I know about them other then I know I don’t want to need one.

Chuck