Why don't give these peeps a ring
http://www.demon.co.uk/hyperbar/
They are very pleasant and are more than willing to help, explain things so they don't have to help people.
They also have no problems showing you around the facilitys.
The standby emergency blokes are top lads who actually managed to survive diving in the north sea in the 70's.
MJ
And I just found this which is proberly more than you wanted on the techie side of things
http://www.emedicine.com/emerg/topic790.htm