Advanced decompression theory

[Wally1716]

The only thing I learned in adv nitrox that I either didn't already
know or wasn't covered in full cave was how to shoot a bag... seemed like a really
expensive class to learn how to shoot a bag.

Can I ever look forward to a class such as trimix covering more advanced topics
such as the theories behind bubble models, the origin of the oxygen window and
other topics that would allow a dvier to critically compare RGBM, VPM-B, VPM-B/E
and Buhlmann's ZHL-16? I've read through all the documents I can find on the
topics but I would love to have the opportunity to discuss it with an expert.

Finally, is my entry level mix class going to be another big disappointment (END,
EADD, basic understanding of IBCD, He fast, N2 slow, etc)?

..
Like so many other diving courses, it is still the instructor who makes a difference.
Anyone can read the book and run thru the PPT slides and see what is all about.
The instructor should add to all that with his/her experience, knowledge and
ADDITIONAL expertise BEYOND what the course calls for. Shooting of a bag is
only one of the skills to be learned and practiced in Advanced Nitrox; what about
doing a foolproof gas switch or stage exchange? What did you do about your
buoyancy on stage drop-off and recovery; your gas consumption prediction (yes,
students should be able to predict how much gas they'll have at X minutes into
the dive and drill to compare with actual readings)? Practiced the rescue of an
Ox-Toxing buddy (we teach this in Basic Nitrox)? Did you work on your comm
skills with your buddy, with surface personnel ? Did you simulated common
problems or emergencies? Did you realize how your trim changes with your new
configuration?
.
You can certainly look forward many of your questions in higher level mix courses,
but, again, it is the selection of your instructor and his/her dedication to their
courses and students that makes the difference in the outcome. The fact that
the book or slides does not include the topic does not preclude the instructor
from teaching it.
.
As for your last question above, I am afraid that if your instructor just teaches
"the book", you will get similar results.

 

[loosebits]

..
Like so many other diving courses, it is still the instructor who makes a difference.
Anyone can read the book and run thru the PPT slides and see what is all about.
The instructor should add to all that with his/her experience, knowledge and
ADDITIONAL expertise BEYOND what the course calls for. Shooting of a bag is
only one of the skills to be learned and practiced in Advanced Nitrox; what about
doing a foolproof gas switch or stage exchange? What did you do about your
buoyancy on stage drop-off and recovery; your gas consumption prediction (yes,
students should be able to predict how much gas they'll have at X minutes into
the dive and drill to compare with actual readings)? Practiced the rescue of an
Ox-Toxing buddy (we teach this in Basic Nitrox)? Did you work on your comm
skills with your buddy, with surface personnel ? Did you simulated common
problems or emergencies? Did you realize how your trim changes with your new
configuration?
.
You can certainly look forward many of your questions in higher level mix courses,
but, again, it is the selection of your instructor and his/her dedication to their
courses and students that makes the difference in the outcome. The fact that
the book or slides does not include the topic does not preclude the instructor
from teaching it.
.
As for your last question above, I am afraid that if your instructor just teaches
"the book", you will get similar results.

Everything you mentioned here is either part of the full cave curriculum (e.g. bottle handling) or it was material that was already covered in other classes. Shooting a bag was the only thing I learned that I didn't already know (either from other classes or self-study), not the only thing that was covered.

 

[MikeFerrara]

I think the way decompression theory is taught is slowly changing. Still, course requirements are usually centered around the application of specific tables or models although there may be some choices there.

When I used to teach Advanced Nitrox, I introduced students to a variety of decompression softwares and had lots of articles and books to show them. Since some of that isn't required by standards, how much time we spent on it was somewhat dependant on student interest. Since I'm not necessariliy qualified to teach VPM or RGBM (as examples) this time was more "discussion" and a sharing of information sources and doing comparissons.

Some of the tech courses that I took as a student were right out of the book using whatever tables/models that the agency was using at the time. Not to say that's all bad because I think there are a couple of seperate issues. One being decompression theory and stratagies and the other being learning the skills needed to apply whatever stratagies you choose to use. ie, at some point you have to learn to dive a schedule, do gas switches, manage the extra equipment and potential problems that can go with it and so on. Others like my cave and trimix courses were more indepth, largely due to the experience of the instructor. If you have an instructor who does or has done VERY long cave dives (I say cave because they often involve longer run times than the typical OW dive...even a deep one), you'll likely gain some insight beyond what you can read in the book.

Both, my former cave and my trimix instructor have enough experience in caves and wrecks (for instance) to be prepared to discuss lots of things that you're not likely to find in a text book.

I have to agree with Wally that instructor selection is critical. That seems especially true these days with all the recreational instructors I see doing 132 ft dives that require about 2 minutes of decompression trying to get in their 25 "technical dives" to qualify for their agencies latest "tech" course introduction. I've also, at times, been unable to avoid overhearing a couple instructors teaching "tech" classes at the local 90 ft deep quarry. Some of what I heard being taught was a little scary and I couldn't help but get the impression that the instructor hasn't ever done a real "technical" dive in their life.

As always...buyer beware.

 

[Kevrumbo]

Another thread got me thinking about this. I took my adv nitrox along with full cave. The instructor was great and I have no complaints about his teaching ability. It was the material that I take issue with.

For one thing, the material revisited all the same stuff we learned in OW and in nitrox: signs and symptoms of DCS, OTU/CNS calculations, EAD calcs, MODs, blah blah blah.

The only thing I learned in adv nitrox that I either didn't already know or wasn't covered in full cave was how to shoot a bag... seemed like a really expensive class to learn how to shoot a bag.

Can I ever look forward to a class such as trimix covering more advanced topics such as the theories behind bubble models, the origin of the oxygen window and other topics that would allow a dvier to critically compare RGBM, VPM-B, VPM-B/E and Buhlmann's ZHL-16? I've read through all the documents I can find on the topics but I would love to have the opportunity to discuss it with an expert.

Finally, is my entry level mix class going to be another big disappointment (END, EADD, basic understanding of IBCD, He fast, N2 slow, etc)?

This LDS in your area hosts GUE Instructors and Classes:
http://www.emeraldseadivers.com/600Tech.htm#COURSES

Finallly, I recommend taking a Class from Andrew Georgitsis (his write-up on Ratio Deco puts all the present Theory into proper Practice):
http://www.breakthrudiving.com/xducation/pdf/ratiodeco.pdf