I watched my best friend die of colon cancer 12 years ago. He was on a vent and you could actually see his coma-induced body still fighting it, trying to eject it. IMO, it is nothing but torture.
About 25 yrs ago, after bypass surgery, my Dad was in an ICU on a ventilator. One time his eyes opened, he looked at me and indicated with his raised thumb that he wanted it out. I explained to him that he needed it to breath, that he had very strong sedatives in him and couldn’t do it on his own, but he either didn’t understand or care. He got quite agitated. Had his arms not been restrained I’m certain he would have pulled it himself. A minute or less later a nurse came in, added something to one of his IVs and he went back under.
I asked him about it afterward, but he had no memory of it.