Being on a ventilator is traumatic. So much so that they generally put you under. Can you imagine waking up with a tube through your mouth and down your throat forcing you to breathe? It happens and people panic and have to be restrained. People get PTSD.
https://www.hopkinsmedicine.org/news/media/releases/ptsd_com...
If you can get the O2 up to a livable level without a ventilator so that the patient is supported enough to get well, that that is a good outcome.