Not long Janey, You will feel the BP weaken and the heart rate increase. Breathing is irregular. Hold his hand and talk about the happy times. He can hear you.
Janey, is your dad on Hospice? You could talk to the hospice nurse if he is. Otherwise, does your insurance company have a nurse line? I'm so sorry you're going throufh this without much guidance.
If he's in the hospital, talk to his nurse.