I would imagine that hypno-birthing is where you use controlled breathing to manage the pain? In essence, this could help, but I have found that you are in an altered mind-state during labour anyway - it's like being detached from reality, though hyper-aware of certain things.
Do you concentrate on the "spaces" between breaths (before the inhale and exhale) until your whole focus is on your breathing? I've tried this when not in labour and it does make you feel as though you're in a "trance" like state. The only trouble I'd imagine is that contractions only last a minute or so and can have 5-10 mins in-between. How would you build yourself up to the trance-like state for the contraction, without having to concentrate on your breathing and remain "tranced out" for the whole (in my case 42 hour) labour? Or just for each contraction? I mean, a lot of people don't think gas and air works quickly enough to take the edge off the peak of a contraction and that takes effect in, is it, 20 seconds?
I'm sorry if I sound negative, I really don't mean to: I'd be interested to learn more about this too.
x