Deneen,
I too am so sorry to hear about your friend, this is one of the tougher parts of life, dealing with a friends imminent passing.
Many hospice publications on death and dying write about the pre-passing energy surge. It's been a long time since I read the information but if I remember correctly is something to do with the person's spiritual need to gather strength for the journey, and also to say goodbye to loved ones if possible. The image I get is something similar to the hollywood deathbed scenes, where the dying person speaks to his relatives one last time.
Thing is it can be anything from one last deep breath if the person is in a coma, to actually a more alert state of conciousness, depending on the patient. Problem is, it can't be predicted, especially if the patient is in a coma.
Thing is to be there for him and his family, talk to him, let him know your feelings.
Again, sorry to hear about all is happening, God Bless and take care
Bob S.