CAPTAIN SINBAD
Contributor
A ScubaBoard Staff Message...
This could easily get off-topic into yet another discussion about ratio deco. However, I believe the main argument for ratio deco is that there's a big difference in trusting factual things, like depth, time, average depth, current temperature, etc. and trusting something which is computationally precise but questionably accurate like decompression. How you feel and other conditions of the dive may play a role in how much or how little deco you do using a UTD ratio deco approach (I make specific mention of the "UTD ratio deco," because the GUE ratio deco is terribly incomplete and only used in emergencies).
Also, you may think ratio deco is complex math, but to me it's really not. It's fairly simple arithmetic, not complex algebra or anything like that. I recently had a discussion with someone about a dive profile, which initially resulted in them running the profile in their program and it determined they needed to spend 55 minutes at 20' on 100% O2. They didn't realize until I told them that there's something terribly wrong with that plan, and it turned out to be a bug in the software (software was set to calculate last stop at 20'). Computers have their issues as well, as much as I hate to admit it (I'm a software developer by day).
Finally, if you compare ratio deco profiles to 30/85 Buhlmann profiles they are strikingly similar, so I wouldn't let ratio deco be the reason that one should avoid a UTD advanced class.
I respect that and if you read my earlier posts I am have been very accepting of UTD's ratio deco. In the past I have had a greater trust in deep stops and VPM etc. Recently Dr. Simon Mitchell's presentation below shows that Deep Stops are not as safe as they convince people to be and that is why Navy has rejected their use.
Based on this, the most appropriate gradient factor (according to all the research as it stands today) is not 30/85 but 50/70. This is what the likes of John Chatterton have been saying, "Get off the bottom!" How would you accommodate this into Ratio Deco which will still force you to do your first stop much deeper?
Secondly, when we look at the study that Andrew did to prove the effectiveness of RatioDeco seemed to actually show the short-comings of it.
UTD Decompression profile study results published
Even Andrew and the UTD community accepted the results that Ratio Deco is dangerous on some profiles. Instead of abandoning it and moving towards Buhlmann's gradient factors Andrew developed "Ratio Deco 2.0"
Why?
I believe that UTD has a lot to offer to the world if it expands its decompression curriculum to include Buhlmann GF's, VPM and RGBM, GUE Ratio Deco VS UTDs as well as Italian study that led to 2.0 along with the Navy Study and why they are not buying any of it. The purpose should be to create a diver who understands all approaches to modern decompression without the agency pressure to accept one as the gospel truth over the other. If they could do that that would be closer to Andrews ideals of the "thinking diver." It would be GUE with all the good practices people love about it but without the things that they are ticked off / discouraged about.
Just something to think about for the higher level UTD instructors.
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