These are exactly the conversations I had to have with my mom in the last year, who, many of you know, died about a month ago.
I talked to lots of nurses who said if they could, they would have "DNR" tattooed on their foreheads, for exactly the reasons described in other posts above--resuscitation can break ribs, and only about 10% of people leave the hospital in the shape they came in. Finally, my best friend from 4th grade, who is an ICU nurse, came to talk with my mom. She's known Susie for 40 years, so was comfortable discussing it with her, and after that she signed a DNR/DNI order. Basically what Susie said was that at her age, resuscitation or intubation would be done only when everything medically possible had been tried, and that neither would change the effectiveness, or lack thereof, of the medical treatments.
These are conversations that really need to be had. That same friend Susie has told me many stories about ICU patients whose families insist on keeping them going far past their bodies' capacity to really live. Once a tube is in, it's a lot harder to take it out, than to never have it placed in the first place.
I spent many hours in the last year talking with my mom about this stuff. It's major emotional heavy lifting, but if you don't do it, your parent may end up in a much worse situation. You have my TOTAL sympathy here. If, Mr. S., Silver is willing to help here, I hope you consider allowing her to do so.
"My predominant feeling is one of gratitude. I have loved and been loved;I have been given much and I have given something in return...Above all, I have been a sentient being, a thinking animal, on this beautiful planet, and that in itself has been an enormous privilege and an adventure." O. Sacks