I am a CHT presently going through a BSN program. I used to run a hyperbaric department with a multiplace chamber. I am going to give you my two cents.
you may want to check out the baromedical nursing association not real good source for certification information but if you are going to persue your ACHRN or CHRN you are probably going to want to know about and join this association. The RN and tech's will be coming to blows in the future! Lots of chambers are looking to cut expenses/downsize and if you can get one person who can do it all. Techs are good for the "tech' stuff but usually don't have the certs to perform in hospital care. If you are an RN that can drive a chamber you are a hot commodity. MY GOAL!
the NBDHMT has just updated its site to include study material you can download to help with your certification. i think it is nbdhmt.org. or just google it.
Dick Clark is the man! he deals with monoplace chambers only. He has a great library of hyperbaric research. You may notice lots of docs and techs publishing but none too many RNs.
you may also want to check out the UHMS.org site for some links to other chambers and study material.
Best publishing is another source for hyperbaric books.
Give you an earfull?
Best of luck to you!