OP
Fatigue after deco dives
- Thread starter TracyN
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I'm just sorry you had to bear witness to it.
Maybe one day I'll let you make it up to me. I do kind of miss your dorkiness.
flyingvisit
Registered
I think others have already stated that some of this should have been covered in your course, but a lot of it is learning yourself, and learning how your body reacts.
A few points though -
Cold - funny subject. I believe that there was some research (I need to find the links/sources...) some time back, that strangely enough when a diver is cold, and the blood vessels constricted, that actually limits gas ontake, and divers that were cold throughout a dive actually bubbled less at the end. However, note that I said THROUGHOUT the dive. The big risk for divers, and the most common situation - is when they start off warm/hot at the start of the dive, so that the tissues are well perfused with blood and therefore on gassing is more effective, and then get cold towards the end of the dive, the blood vessels constrict, and off gassing is far less effective. That is a recipe for DCS.
The other point is that its very hard to draw a line of "bent" / "not bent" - remember, when you get out of the water you're still decompressing (off gassing). That's exactly why you don't then jump on a plane, or drive to the top of a mountain. Learning about decompression, as I understand it, is a lot to do with learning what is and isn't effective for yourself (and I'm yet to do a proper AN/DP course, but I try to understand the theory because it still relates to recreational diving...but thats a whole other argument...). However, as many have stated, padding stops at the shallower depths, might help, but you need to look at it as an overall picture. It sounds like the type of deco you are doing is almost "bend and mend" - stops all in the shallows. Do you even do a half depth stop? If it's a 30m (100ft) dive, I'm starting some stops, even recreationally, at 15m, to try and slow bubble formation and off gas better - and I normally feel better for it.
N.B. There is a limit to how effective the deep stops are before you start on gassing again.
A computer, or even back up tables, aren't set in stone. It doesn't take into account your thermal capacity, or how you feel that day, etc etc. Its a learning process, and you might find in time that your "conservative" computer is not very conservative compared to how you like to dive.
A few points though -
Cold - funny subject. I believe that there was some research (I need to find the links/sources...) some time back, that strangely enough when a diver is cold, and the blood vessels constricted, that actually limits gas ontake, and divers that were cold throughout a dive actually bubbled less at the end. However, note that I said THROUGHOUT the dive. The big risk for divers, and the most common situation - is when they start off warm/hot at the start of the dive, so that the tissues are well perfused with blood and therefore on gassing is more effective, and then get cold towards the end of the dive, the blood vessels constrict, and off gassing is far less effective. That is a recipe for DCS.
The other point is that its very hard to draw a line of "bent" / "not bent" - remember, when you get out of the water you're still decompressing (off gassing). That's exactly why you don't then jump on a plane, or drive to the top of a mountain. Learning about decompression, as I understand it, is a lot to do with learning what is and isn't effective for yourself (and I'm yet to do a proper AN/DP course, but I try to understand the theory because it still relates to recreational diving...but thats a whole other argument...). However, as many have stated, padding stops at the shallower depths, might help, but you need to look at it as an overall picture. It sounds like the type of deco you are doing is almost "bend and mend" - stops all in the shallows. Do you even do a half depth stop? If it's a 30m (100ft) dive, I'm starting some stops, even recreationally, at 15m, to try and slow bubble formation and off gas better - and I normally feel better for it.
N.B. There is a limit to how effective the deep stops are before you start on gassing again.
A computer, or even back up tables, aren't set in stone. It doesn't take into account your thermal capacity, or how you feel that day, etc etc. Its a learning process, and you might find in time that your "conservative" computer is not very conservative compared to how you like to dive.
mdax
Contributor
Have you taken AN/DP?
Are you using O2?
Are you using O2?
I think she said she's taken AN & DP with Paul.
Haha.... she got DP from Paul. That's just naughty.
Haha.... she got DP from Paul. That's just naughty.
JamesK
Contributor
Thanks man. Now everyone inside the weapons simulator is looking at me like I am crazy. Lol
SkimFisher
Contributor
I was taught to do a half-stop for two minutes unless my first required stop is deeper than half depth. But I was also taught to run tables and use my computer as a backup, and the tables we were taught I've noticed are a bit more conservative than my DC (much more so on deep stuff) unless I use a Gradient Factor. Tables are RGBM, DC is Buhlmann.
If your first stop is @ 20' then it stands to reason that there's either A.) not much of a deco obligation, or B.) Something screwy with whatever you're using to base your stops on.
Either way in an ideal scenario - hydrated, warm, proper deco plan, in-water sit, minimal post-dive exertion - fatigue shouldn't be an issue.
If your first stop is @ 20' then it stands to reason that there's either A.) not much of a deco obligation, or B.) Something screwy with whatever you're using to base your stops on.
Either way in an ideal scenario - hydrated, warm, proper deco plan, in-water sit, minimal post-dive exertion - fatigue shouldn't be an issue.
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Cave deco is often a bit different from open water deco, in that the place where you might like to do a stop may not be amenable to stopping (crazy flow, very narrow passage). Cave profiles often look a lot more Buhlmannesque (bend & mend) than open water profiles. In addition, cave dives don't tend toward the deep dive/short bottom time shapes that most open water decompression dives have -- they are often very long bottom times at moderate depths, and I'm not sure anybody knows what the best decompression is for such dives. Cave profiles also quite frequently have significant reverse sections in them. You have to go where the cave goes.
I remember reading something a while back about Ginnie in particular seeming to be a place with an unusually high DCS rate, but the writer was unsure if it was simply because it's a cave that's used by a lot of people, and a lot of novices, or whether there was something about the dives there (which tend to be long swims at 100 feet) that wasn't working for the approach to deco used by the divers there.
I think it's Rick Murchison here who wrote that every staged decompression dive is an experiment you are running on your own body; keep careful notes. There's a lot of truth to that, I suspect.
I remember reading something a while back about Ginnie in particular seeming to be a place with an unusually high DCS rate, but the writer was unsure if it was simply because it's a cave that's used by a lot of people, and a lot of novices, or whether there was something about the dives there (which tend to be long swims at 100 feet) that wasn't working for the approach to deco used by the divers there.
I think it's Rick Murchison here who wrote that every staged decompression dive is an experiment you are running on your own body; keep careful notes. There's a lot of truth to that, I suspect.
Crush
Contributor
I am not trained in deco diving, but I have a good understanding of dive physiology. Others have mentioned these, but I'd like to highlight two problem areas that I feel might apply in your case:
- The stress of being cold can rob you of strength and energy reserves, leading you to feel tired. The cooling is slow, therefore subtle, but your body burns a lot of calories trying to keep you at normal operating temperature; and
- Being cold can complicate DCS. Tissues which are warm at the beginning of a dive are well-perfused (i.e., have good blood flow into and out of them) and will on-gas and off-gas as predicted by standard models. Tissues which are cold at the end of a dive are not well-perfused so they will on-gas and off-gas much more slowly than is predicted by standard models. In summary:
- Being warm at the beginning of a dive and warm at the end of a dive is OK;
- Being cold at the beginning of a dive and cold at the end of a dive is OK;
- Being cold at the beginning of a dive and warm at the end of a dive is OK; but
- Being warm at the beginning of a dive and cold at the end of a dive is likely to increase your risk of DCS. This last point is based upon Doppler studies of microbubble formation which may, or may not, be indicative of the onset of DCS. I am sure that someone will argue against this theory but the point is that the best physiological studies we have indicate that being warm at the beginning of a dive and cold at the end of a dive is likely to increase your risk of DCS.
Crush
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