I don't think there are hard and fast rules about how much deco you can "blow off" and expect to walk away from it, chamber or no. But I don't know about the rest of you, but I don't do my technical or cave dives with strangers. I do them with friends. Some of them are very close and very dear friends, and one of them is my husband. If I had someone unconscious underwater and breathing (unlikely, but possible) I'd manage them through at least some of our decompression. I think I could do that -- it's not easy, but I have brought people up in classes with pretty decent control. If they aren't breathing, you have very little time to end up with a neurologically intact person -- probably in the neighborhood of about 8 minutes. (Note that CPR classes will say something more like 4, but they are not talking about a patient who has been breathing a high ppO2 before the breathing stops. When we are intubating patients and have had them on a ppO2 of 1.0 before trying, and the patient is of normal body habitus, it is estimated we have about 8 minutes before serious damage occurs.)
So you need to have that person on the surface in 8 minutes or less. And if you are going to do any of your deco, you've got to manage a gas switch in the middle of ascending this unresponsive and unhelpful diver. It's not going to be easy, and my guess is you probably wouldn't try, but would just come up on backgas. If I had a huge obligation (which I doubt I ever will) I might stop at 20 feet and send the person up from there, and then do a huge, long, Buhlmann-type hang. Or I might take them all the way up. It would in part depend on how much risk I was taking on, who it was, and what the conditions on the boat are. I've dived off one boat that has a suited up safety diver at all times -- there, I'd probably be more likely to send someone up. Somebody's father driving my boat . . . I'd probably try very hard to go to the surface with the injured person.
The prognosis for someone who stops breathing underwater is poor, unless you are talking about severe narcosis in the 400 foot range. But I couldn't live with myself if my friend Kevin or my dear friend Kirk or my husband Peter died, and I wasn't totally sure I had done everything I could to save them.
Things like this are why staged decompression diving is not something to be undertaken lightly. Anybody can go down and come back up in stops, and even switch gas. But what you do when things go sideways is why this stuff isn't trivial at all.
