Diving with gradient factors for a new recreational diver

[boulderjohn]

From a overall risk perspective you are spot on. What frustrates me, though, is reading research that in recreational divers following/executing conservative plans, a large (or by memory, even the larger) portion of DCS cases were undeserved.

Would it shock you to learn that the overwhelming majority of people who die in Germany are German citizens? That must mean it is for some reason not safe to be a German citizen, right? Should Germans renounce their citizenship in the hope of living longer?

Almost everyone who does recreational dives does so within standard recreational limits and following standard ascent protocols. That is why a high percentage of DCS cases are among such people. The percentage of those cases is tiny--something like 0.002 percent. Are you saying that because that percentage of people get bent following standard protocols, you are going to reject those protocols and do something untested instead?

 

[ginti]

From a overall risk perspective you are spot on. What frustrates me, though, is reading research that in recreational divers following/executing conservative plans, a large (or by memory, even the larger) portion of DCS cases were undeserved. Staying within half of the NDL limit (assuming single depth) seem like a notable risk reduction, but feels quite conservative to be practically enjoyable...

besides what @boulderjohn said, keep in mind that DCS event seems undeserved when people follow the computer limits. But is it always the right to blindly follow the computer? There is a story of a guy who got an undeserved case of DCS following the computer in standard mode... after taking an intercontinental flight and drinking a couple of beers.

So there are some factors to keep in mind when analyzing these data:
- did the people claiming undeserved DCS have any medical condition?
- were the people in a good shape for the level of conservatism of the computer? or to dive at all?

I assume that people with medical conditions that could affect deco are not considered in the studies; but what about the others?

 

[scubadada]

Hi @HomeBarista

You might enjoy this post Now it's time to choose a wrist computer. and others from the recent discussion of purchasing a new computer. Many of the issues you have brought up have been discussed many times on SB and can be found through "Search".These discussions are often, but not always, found in the computer forum Computers, Gauges, Watches & Analyzers

It may be more useful to think about unexplained episodes of DCS rather than undeserved episodes.

Best of luck

 

[Angelo Farina]

The usual definition of a technical dive seen around here is a dive in which one no longer has direct access to the surface, due to either a hard(cave/wreck) or soft(deco)ceiling. I'm not sure what "for profit training agencies" have to do with it.

It has to do with the legal liability and economical consequences in case of accidents. This makes it more prudent, for US based organizations, to keep recreactional activities at a lower perceived risk level.

 

[Celt]

I don’t see any harm in practicing stops at various depths as long as you stay inside your NDL and can make a slow assent to the surface if you get fed up. But there’s no need to plan them.

 

[rhwestfall]

I do remember my first deco dive. With all the "no deco" mutterings of the recreational dive community, actually doing some decompression becomes a really big thing. All we did was a 30m/100ft dive for about 40 mins on the bottom with 10 mins of decompression on backgas.

+1! My first planned DECO dive was 45 minutes at 130'. It was so relaxing to be able to explore the entire wreck without fear of the NDL limits of recreational diving.

It still gives me some chuckles when I am on mixed level boats where we will do a light deco, and I am watching some of the lesser trained divers "racing" op the line to avoid the monster of the deep....

 

[rob.mwpropane]

+1! My first planned DECO dive was 45 minutes at 130'. It was so relaxing to be able to explore the entire wreck without fear of the NDL limits of recreational diving.

It still gives me some chuckles when I am on mixed level boats where we will do a light deco, and I am watching some of the lesser trained divers "racing" op the line to avoid the monster of the deep....

It's taught that way though, hell even on the damn dive table cards it's all blacked out like... > "death is waiting". Honestly there should be more emphasis on gas management and ascent rates. The biggest thing I learned after OW was by watching my surfGF was that I was going up way to fast, especially in that last 20 feet.

I dive more conservative now and I take my time coming up (with proper gas planning of course).

 

[doctormike]

I think that it's reasonable - from an educational point of view - to tell divers without the appropriate training that they should not be doing staged decompression, full stop.

Now of course, we can argue across the pond as to what level someone should be trained to before they are allowed to dive independently, that's an educational philosophy conversation. But I don't think that it's fair to mock the approach to OW training standards in the US by implying that it's simply a money thing or a litigation thing.

Yes, any diver who briefly exceeds their NDLs can just follow almost any modern dive computer and it will get them safely to the surface, IF they have enough gas. I think that the reason that we just tell people not to go into deco at the OW level rather than getting into the nuances of N2 loading and allowing "just a little" deco is that you don't want untrained people guesstimating about how much "just a little" is, especially if they may not have enough gas to do that deco. If they think that deco is OK, the tendency is to push that "just a little" definition until they may get into real trouble, if they haven't done the gas planning ahead of time.

And if the European agencies feel that no one should be in the water outside of a discover diving class without having the training and skill to plan a decompression dive, that's OK. It's apparently not what the US agencies feel. The tradeoff of course is that you will have a lot fewer people experiencing diving at all if you make the entry standards too strict. It's fine to argue for either side of that tradeoff, but it definitely exists.

I'm not an instructor, but I think that at this level, you want all divers to have the ability to surface immediately if there is ANY sort of problem without adding the risk of omitted decompression onto all the other risks of that situation.

 

[inquis]

Honestly there should be more emphasis on gas management and ascent rates.

You mean with numbers & stuff? Dunno, sounds pretty technical...

 

[wnissen]

Ahh, if didn't feel this way I wouldn't have started this thread .
Feelings aside, is the standard safety stop insufficient for me? I don't know and don't have the experience to know. I feel tired after diving (probably related to decompression stress), I've never had clinical DCS symptoms, but I also don't have a baseline for what's normal.

You're not out of line at all. The most recent number I saw from DAN was that 80% of the DCS cases they saw were for people diving within the limits. So definitely pay attention to the symptoms that you learned from your training, it's totally possible to get DCS even if you did nothing wrong according to the tables.

As someone who works in the numerical simulation field, I always say, "How can you tell your simulation is lying it you?" And the answer is "It's producing results". No table or dive computer can tell you with 100% certainty that you're not going to get DCS. They have been proven to avoid the vast majority of cases, but they are not measuring your individual physiology. Smarter people than me will tell you we don't really know what causes DCS. So feel free to check into some more conservatism in your dive planning/execution, but if DCS risk is what you're worried about, I would look into improving any dehydration, lack of sleep, alcohol consumption, overexertion, and other factors that appear to influence it. Just my two cents.