Decompression Tables
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Mr Carcharodon
Contributor
In a recent edition of Alert Diver DAN reported that DCS cases were around 1% of all diving related accidents. DCS is uncommon enough that it is unlikely that a significant difference could be discerned in real world divers where fitness, hydration, ascent rates and dive profiles are all uncontrolled. Also type I and type II bends tend to get lumped in together when there is a significant difference in outcomes.
Richard Pyle, and the ratio deco advocates, have used fatigue and subjective feelings of wellness as leading indicators of DCS. They advocated deep stops and padding the stops of subsequent dives as preventative measures based on those personal observations. That may be a better approach than creating a one size fits all algorithm that is conservative enough to catch the four or five sigma outliers on the curve. In any case a discussion of what mild DCS symptoms are, and how to prevent them might be more useful than trying to discern differences between models.
Richard Pyle, and the ratio deco advocates, have used fatigue and subjective feelings of wellness as leading indicators of DCS. They advocated deep stops and padding the stops of subsequent dives as preventative measures based on those personal observations. That may be a better approach than creating a one size fits all algorithm that is conservative enough to catch the four or five sigma outliers on the curve. In any case a discussion of what mild DCS symptoms are, and how to prevent them might be more useful than trying to discern differences between models.
The tables were written with a 5% rate of bends. It's an acceptable risk for the Navy.
It seems like people are accepting that risk?
I've noted several people claiming to use Navy Tables for backup so I'm assuming they are accepting it. It's my opinion there are better options that reduce the risk without undo conservatism. Navy dive tables assume an on-board chamber to limit the risk to the diver so 5% is acceptable because they can be fixed on the spot.
LeadTurn_SD
Contributor
Regarding reasons for using Navy tables
: 1.) That was what I was trained on in the 70's
2.) Bends risk was/is acceptable if you don't push the limits!
3.) We were informed about the risks when we first started using the tables for the exact reasons mentioned in previous posts, and #2 above was strongly emphasized.
4.) Based on #2 & #3, most of us built in a "buffer" that was more conservative than PADI's current RDP.
5.) Unlike PADI's RDP, we used the Navy tables to plan and execute deep air deco dives. (And no, I would not do that today!)
6.) The Navy tables are based on a square profile, we used them on multilevel dives; so in general my profiles using Navy tables were more conservative than my current dive computer for the same dive.
7.) Now I just refer to them (or PADI RDP) for planning purposes, and carry them in my dive bag "just in case".
Best Wishes.
Regarding reasons for using Navy tables
1.) That was what I was trained on in the 70's
2.) Bends risk was/is acceptable if you don't push the limits!
3.) We were informed about the risks when we first started using the tables for the exact reasons mentioned in previous posts, and #2 above was strongly emphasized.
4.) Based on #2 & #3, most of us built in a "buffer" that was more conservative than PADI's current RDP.
5.) Unlike PADI's RDP, we used the Navy tables to plan and execute deep air deco dives. (And no, I would not do that today!)
6.) The Navy tables are based on a square profile, we used them on multilevel dives; so in general my profiles using Navy tables were more conservative than my current dive computer for the same dive.
7.) Now I just refer to them (or PADI RDP) for planning purposes, and carry them in my dive bag "just in case".
Best Wishes.
IMO your rule number 1, and physical conditioning associated with the military are the two most commonly violated aspects of diving Navy Tables by the general public. Of course everyone is free to assume their own risks.
1.) That was what I was trained on in the 70's
2.) Bends risk was/is acceptable if you don't push the limits!
3.) We were informed about the risks when we first started using the tables for the exact reasons mentioned in previous posts, and #2 above was strongly emphasized.
4.) Based on #2 & #3, most of us built in a "buffer" that was more conservative than PADI's current RDP.
5.) Unlike PADI's RDP, we used the Navy tables to plan and execute deep air deco dives. (And no, I would not do that today!)
6.) The Navy tables are based on a square profile, we used them on multilevel dives; so in general my profiles using Navy tables were more conservative than my current dive computer for the same dive.
7.) Now I just refer to them (or PADI RDP) for planning purposes, and carry them in my dive bag "just in case".
Best Wishes.
#1 is a lame answer... Sorry. Do you still dive a horsecollar and use J Valve? From the looks of your Avatar, I'd have to say, "no" - Just because you learned that 30 years ago doesn't make it still good today. There is a lot more study done now than there was then. The fact is. The science behind decompression has progressed beyond where it was 30 years ago. Now Nitrox is available to the public, and people dive Trimix, and even Rebreathers.
#2 - Getting Bent is never the answer... is it? Acceptable risk? I think not.
How about using a good dive computer, or planning software like V-Planner? If you're showing up to a boat, and have to use Navy tables... something is wrong.
The US Navy currently uses VPM (V-Planner is VPM) hmm...
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