Hi jmsdiver:
I'll see what I can do to help answer your questions. I know a little about how physicians get "certified" in diving medicine in the US, but less about how non-physicians get certifications and very little about how other countries handle things.
Your second two questions are easier to answer. Yes, there are certifications for non-physicians. As Bob3 has already pointed out, you can get certified as a diving medical technician (DMT) through a commercial diving school. NOAA also trains DMT's. (
http://www.ndc.noaa.gov/sitemap.html) I know of one certification agency for DMT's. The National Board of Diving and Hyperbaric Medical Technology (NBDHMT) requires training and an exam in order to become a certified DMT. (
http://www.nbdhmt.org/index_ns.htm) Nurses can become certified hyperbaric nurses through the Baromedical Nurses Association. (
http://www.hyperbaricnurses.org/).
There are
many courses in diving medicine and physiology that go
well beyond the training that you get in a typical scuba certification class. DAN offers quite a few courses on a regular basis on dive medicine and physiology. (
http://www.diversalertnetwork.org/cme/) The Undersea and Hyperbaric Medical Society (UHMS) also offers quite a few courses. (
http://www.uhms.org/Courses/Courses.htm) There are other groups and organizations that also offer courses, often in tropical vacation spots. Most of these courses are advanced enough that they would probably assume that attendees have general training and knowledge in both medicine and diving (if not dive medicine) before attending.
Your first question is the hardest, and the best answer is "depends". How you get the certification depends on what kind of certification you want to get, how you want to get it, and what you want to do with it once you've got it. For example, I'm interested in dive medicine just for fun, so took a UHMS sponsored course in diving and hyperbaric medicine a few years ago. That course got me a fancy certificate for the wall that said I was certified as a Diving Medical Officer (DMO) by the International Board of Undersea Medicine (IBUM). I even got an IBUM t-shirt. It was a very good course (an ex-Navy DMO in the class said he got a better education in that one course than he did during his whole service in the Navy) but I don't think that I would be comfortable practicing dive medicine based on that one week course. In order to be included in DAN's physician referral network, I believe you have to complete the more comprehensive course in diving and hyperbaric medicine offered by NOAA. If a physician wants to get a
real board certification in Undersea and Hyperbaric Medicine in the US, they need to complete approved training and pass an exam. (
http://www.abprevmed.org/html/uhm.html) If I were to ever practice diving medicine for a living, I would do a fellowship and get that ABPM board certification like Watergal mentioned. But since it's just a hobby, I don't plan on putting in that much trouble and expense.
If you're interested in getting a certification for yourself, you might look into the requirements of the above organizations and see if they offer what you're looking for.
HTH,
Bill