Hi-
I have trismus, and have gotten great results using the Therabite (a device that helps you stretch your jaw). I've never heard of using hyberbaric oxygen, but I have heard of stretching under sedation. An oral surgeon mentioned this to me as an option- I could go under, and he would "stretch the heck" out of my jaw, and when I woke up it would be painful, but I would follow it up with aggressive stretching on my own with the Therabite. But the idea was, that he could stretch it much harder while I'm asleep than I can when I'm awake, and that extra part would give me a head start on my own stretching.
The Therabite definitely works, but you have to commit to doing it and sticking with it.
There is tons of information here in old posts about trismus, let me know if you are still here on the forum and I can help you find it. A good place to start would also be the trismus section of the main OCF site.
http://www.oralcancerfoundation.org/dental/trismus.htmMelissa