My dad has vascular dementia and pneumonia he is being risk fed. hes sat up smiling ATM which he hasn't done in his 7 wks in hospital. I live 5 mins away,I'm thinking as he's sat up smiling would it be safe for me to leave him for just 20 mins or could he rapidly worsen within minutes??
If he is generally improving then leaving for a short while should not be a problem. As he has been in hospital for 7 weeks and is still alive it would appear that he is generally improving. Aspirating food is a common problem in the elderly but it is a good sign that he is actually accepting food. Always remember that when people are dying they often want to spare their loved ones the pain of watching them die so will wait till no one is in the room.
There really is no right or wrong answer to your question but as CM says you need to get away at times just to go home and change clothes etc,
So go ahead and try leaving for a short while and depending on circumstances and your comfort level gradually lengthen the time you are away.
My personal feeling is that it is ok to leave if you need a break. Did they give you a prognosis for his pneumonia? Did the doctor discuss asking for a hospice evaluation? My grandpa had pneumonia last year and just did not fully recover from it and declined over about a month. He was in his late 90s and he was just really weak by that point. We asked for hospice and they were able to help keep him comfortable though at that point he was asleep most of the time. His last day he had taken a decline but was pretty much at the same level all day. We did leave to go home for dinner -- at that point we were really not sure what would happen but thought he might have a couple more days. We went back at night, thinking we might go home to sleep for a few hours depending on how stable he was, but the nurse took his pulse and it was slowing. She suggested we stay with him, and he only stayed with us another hour or so. Another sign she showed us what that his extremities were starting to get little bluish purple spots -- it was most noticeable on his toes at first. The marks moved up toward his knees as the night went on and also showed up on his hands. It was sad, but also a relief that she could tell us what to look for. I don't think these things always happen but if you see those signs, it is an indication that he is in the process of slowing down and is probably a good idea to stay. (Hopefully the nurse will be able to tell you if she sees those signs too.)
I think what Veronica said is true -- some people wait till they are alone, even if the family just go for a short time to get a coffee or something. If that happens it is not your fault. It sounds like you have really been there for your dad. He must know you care about him. Again I am so sorry.
But in any case, you can't sit at his bedside 24/7 indefinitely. Is there any one else you could ask to come and be with him?