Sorry for your friend. My friend suffered this several years ago, he said that the pain was indescribable. After a few days in hospital, they let him home, and he is fine now. It all depends (IMO) on how much damage has been done - fingers very crossed for your friend.
If things stay as they are then the chances are pretty good average for itu patients is about 85% survival with single organ support (ie the ventilator) if other systems fail it becomes very different though so if they start to use drugs to support blood pressure or start dialysis there is more need to worry. The length of time on the ventilator is significant too and the age and general fitness of the patient before they became ill.
From what I've been told, he originally went into hospital with gallstones and things went downhill, but that was secondhand and my brothers are not the best at passing on information. From the way it was told to me (people taking shifts to be at the bedside 24/7), I was thinking I might have to dust off my funeral suit.
Sqad, as far as I know there are no underlying conditions, and he's in his early 50's.
Had the same thing 18 months ago, though not in a coma or on a ventilator. Heavy doses of antibiotics seemed to cure the immediate problem, had my gall bladder out 10 months later and so far, fingers crossed, no real problems.