OP
Lost Yooper
Guest
This is precisely what I think too. The understanding is critical.
Take care.
Mike
Deco Procedures
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This is precisely what I think too. The understanding is critical.
Take care.
Mike
First of all, please forgive my ignorance if what I'm asking is obvious.
I've been spending alot of time lately reading up on Decompression theory (LY, thanks for the pointers, they've been invaluable, although at times confusing and above my head).
I understand the basic parts, and using the 'standard' SSI dive tables, I accept the fact that even after I complete a dive, I'm not completely decompressed (residual nitrogen and such). We use surface intervals to complete decompression, otherwise the residual nitrogen reduces the amount of bottom time you can do on subsequent dives.
How does this 'residual nitrogen offloading at surface' apply to deco diving? Once you get out of the water, I would assume that a diver is not *completely* decompressed, and that the computer is trying to get you out of the water with the least amount of time underwater safely, but it isn't trying to get you out of the water *completely* offloaded from nitrogen (I would think this would be nearly impossible without a *REALLY LONG* slow ascent from shallower depths).
Example:
Let's say I'm diving the Doria (no other reason other than it seems to be a fairly well-known 'deep dive'). I want to do multiple dives/day, spread over 2-3 days.
Do the computer tables take into account things like surface intervales, residual nitrogen loading, and the like?
Nate
I've been spending alot of time lately reading up on Decompression theory (LY, thanks for the pointers, they've been invaluable, although at times confusing and above my head).
I understand the basic parts, and using the 'standard' SSI dive tables, I accept the fact that even after I complete a dive, I'm not completely decompressed (residual nitrogen and such). We use surface intervals to complete decompression, otherwise the residual nitrogen reduces the amount of bottom time you can do on subsequent dives.
How does this 'residual nitrogen offloading at surface' apply to deco diving? Once you get out of the water, I would assume that a diver is not *completely* decompressed, and that the computer is trying to get you out of the water with the least amount of time underwater safely, but it isn't trying to get you out of the water *completely* offloaded from nitrogen (I would think this would be nearly impossible without a *REALLY LONG* slow ascent from shallower depths).
Example:
Let's say I'm diving the Doria (no other reason other than it seems to be a fairly well-known 'deep dive'). I want to do multiple dives/day, spread over 2-3 days.
Do the computer tables take into account things like surface intervales, residual nitrogen loading, and the like?
Nate
OP
Lost Yooper
Guest
Originally posted by newton
First of all, please forgive my ignorance if what I'm asking is obvious.
I've been spending alot of time lately reading up on Decompression theory (LY, thanks for the pointers, they've been invaluable, although at times confusing and above my head).
Your welcome. I want to remind everyone who may be lurking to be very wary of the advice you see on these lists -- including mine. I do what works for me, and you should always assume that the whole story isn't being told at any one time. This stuff makes for interesting discussions, but nobody should take it to heart
.
I understand the basic parts, and using the 'standard' SSI dive tables, I accept the fact that even after I complete a dive, I'm not completely decompressed (residual nitrogen and such). We use surface intervals to complete decompression, otherwise the residual nitrogen reduces the amount of bottom time you can do on subsequent dives.
The surface interval doesn't complete decompression per se. After you surface from a dive you will be bubbling for a period time that is determined by several factors: bottom gas used, deco procedures, personnal physical conditions, and other stuff. The bubbles will continue to grow until they "peak" and then begin to dissipate. You can do a repetitive dive while you are bubbling on the surface. That's how I understand it in a very small nutt shell.
How does this 'residual nitrogen offloading at surface' apply to deco diving? Once you get out of the water, I would assume that a diver is not *completely* decompressed, and that the computer is trying to get you out of the water with the least amount of time underwater safely, but it isn't trying to get you out of the water *completely* offloaded from nitrogen (I would think this would be nearly impossible without a *REALLY LONG* slow ascent from shallower depths).
Yeah, that's about right. My goal, as far as deco is concerned, is to surface with as little nitrogen bubbling possible. Using helium mixes, proper deco gasses, deep stops, and slow ascents help this to occur. There are some theories out there that people are experimenting with that are trying to get divers out of the water with no bubbling. I haven't heard much about it, but it includes the use of heliox for bottom mix, 50/50 heliox and O2 for deco (I think).
Example:
Let's say I'm diving the Doria (no other reason other than it seems to be a fairly well-known 'deep dive'). I want to do multiple dives/day, spread over 2-3 days.
Do the computer tables take into account things like surface intervals, residual nitrogen loading, and the like?
Nate
Yeah, you can run repetitive dives over multiple days with the deco programs. There are some theories out there that completely ignore prior dives (except for oxygen exposure), but that stuff is so far against the grain. I am currently studying this stuff, but I don't feel comfortable talking about it in an open forum like this.
Take care.
Mike
First of all, please forgive my ignorance if what I'm asking is obvious.
I've been spending alot of time lately reading up on Decompression theory (LY, thanks for the pointers, they've been invaluable, although at times confusing and above my head).
Your welcome. I want to remind everyone who may be lurking to be very wary of the advice you see on these lists -- including mine. I do what works for me, and you should always assume that the whole story isn't being told at any one time. This stuff makes for interesting discussions, but nobody should take it to heart
. I understand the basic parts, and using the 'standard' SSI dive tables, I accept the fact that even after I complete a dive, I'm not completely decompressed (residual nitrogen and such). We use surface intervals to complete decompression, otherwise the residual nitrogen reduces the amount of bottom time you can do on subsequent dives.
The surface interval doesn't complete decompression per se. After you surface from a dive you will be bubbling for a period time that is determined by several factors: bottom gas used, deco procedures, personnal physical conditions, and other stuff. The bubbles will continue to grow until they "peak" and then begin to dissipate. You can do a repetitive dive while you are bubbling on the surface. That's how I understand it in a very small nutt shell.
How does this 'residual nitrogen offloading at surface' apply to deco diving? Once you get out of the water, I would assume that a diver is not *completely* decompressed, and that the computer is trying to get you out of the water with the least amount of time underwater safely, but it isn't trying to get you out of the water *completely* offloaded from nitrogen (I would think this would be nearly impossible without a *REALLY LONG* slow ascent from shallower depths).
Yeah, that's about right. My goal, as far as deco is concerned, is to surface with as little nitrogen bubbling possible. Using helium mixes, proper deco gasses, deep stops, and slow ascents help this to occur. There are some theories out there that people are experimenting with that are trying to get divers out of the water with no bubbling. I haven't heard much about it, but it includes the use of heliox for bottom mix, 50/50 heliox and O2 for deco (I think).
Example:
Let's say I'm diving the Doria (no other reason other than it seems to be a fairly well-known 'deep dive'). I want to do multiple dives/day, spread over 2-3 days.
Do the computer tables take into account things like surface intervals, residual nitrogen loading, and the like?
Nate
Yeah, you can run repetitive dives over multiple days with the deco programs. There are some theories out there that completely ignore prior dives (except for oxygen exposure), but that stuff is so far against the grain. I am currently studying this stuff, but I don't feel comfortable talking about it in an open forum like this.
Take care.
Mike
You speak of removing the Nitrogen
"Yeah, that's about right. My goal, as far as deco is concerned, is to surface with as little nitrogen bubbling possible. Using helium mixes, proper deco gasses, deep stops, and slow ascents help this to occur"
What are your thoughts on removing Helium
Helium bends are supposed to be way worse than Nitrogen.
Just thought I would open that topic up for a little deco time discution
"Yeah, that's about right. My goal, as far as deco is concerned, is to surface with as little nitrogen bubbling possible. Using helium mixes, proper deco gasses, deep stops, and slow ascents help this to occur"
What are your thoughts on removing Helium
Helium bends are supposed to be way worse than Nitrogen.
Just thought I would open that topic up for a little deco time discution
I understand the basic parts, and using the 'standard' SSI dive tables, I accept the fact that even after I complete a dive, I'm not completely decompressed (residual nitrogen and such). We use surface intervals to complete decompression, otherwise the residual nitrogen reduces the amount of bottom time you can do on subsequent dives.
The surface interval doesn't complete decompression per se.
After you surface from a dive you will be bubbling for a period time that is determined by several factors: bottom gas used, deco procedures, personnal physical conditions, and other stuff. The bubbles will continue to grow until they "peak" and then begin to dissipate. You can do a repetitive dive while you are bubbling on the surface. That's how I understand it in a very small nutt shell.
Right. Complete decompression depends on lots of factors, including the length of the surface interval. As far as I know, the current thinking is that you should be completely off-gassed 24 hours after you get out of the water from doign recreational (aka non-deco dives). Does that hold true for tech dives as well?
How does this 'residual nitrogen offloading at surface' apply to deco diving? Once you get out of the water, I would assume that a diver is not *completely* decompressed, and that the computer is trying to get you out of the water with the least amount of time underwater safely, but it isn't trying to get you out of the water *completely* offloaded from nitrogen (I would think this would be nearly impossible without a *REALLY LONG* slow ascent from shallower depths).
Yeah, that's about right. My goal, as far as deco is concerned, is to surface with as little nitrogen bubbling possible.
Unless your GI3, who likes to do the last 20' bubbling, according to the talk he gave the Dutch (??) where you posted the MP3 a couple weeks back. However, I'm more interested in what normal people do, and I don't consider George 'normal'.
Example:
Let's say I'm diving the Doria (no other reason other than it seems to be a fairly well-known 'deep dive'). I want to do multiple dives/day, spread over 2-3 days.
Do the computer tables take into account things like surface intervals, residual nitrogen loading, and the like?
Yeah, you can run repetitive dives over multiple days with the deco programs.
So, in these kinds of cases, it wouldn't be advisable to use 'standard' tables, but instead either bring you Deco laptop with you on a trip, or plan the trip ahead of time, and *stick* to the trip. Is this a fair assumption? (It would seem to me that this would be overly restrictive, since when doing a trip like the Doria, you don't have a lot of control over things like surface intervales, since that is often dictated by the weather as well as your boat-mates).
It seems in this case, you'd want a deco computer, either strapped to your wrist (*gasp*, am I a hertic?) or more preferrable a laptop that you can use to calculate a new profile for your next dives.
I've got another question re:deco procedures as well, but I'll do it in another post.
The surface interval doesn't complete decompression per se.
After you surface from a dive you will be bubbling for a period time that is determined by several factors: bottom gas used, deco procedures, personnal physical conditions, and other stuff. The bubbles will continue to grow until they "peak" and then begin to dissipate. You can do a repetitive dive while you are bubbling on the surface. That's how I understand it in a very small nutt shell.
Right. Complete decompression depends on lots of factors, including the length of the surface interval. As far as I know, the current thinking is that you should be completely off-gassed 24 hours after you get out of the water from doign recreational (aka non-deco dives). Does that hold true for tech dives as well?
How does this 'residual nitrogen offloading at surface' apply to deco diving? Once you get out of the water, I would assume that a diver is not *completely* decompressed, and that the computer is trying to get you out of the water with the least amount of time underwater safely, but it isn't trying to get you out of the water *completely* offloaded from nitrogen (I would think this would be nearly impossible without a *REALLY LONG* slow ascent from shallower depths).
Yeah, that's about right. My goal, as far as deco is concerned, is to surface with as little nitrogen bubbling possible.
Unless your GI3, who likes to do the last 20' bubbling, according to the talk he gave the Dutch (??) where you posted the MP3 a couple weeks back. However, I'm more interested in what normal people do, and I don't consider George 'normal'
.Example:
Let's say I'm diving the Doria (no other reason other than it seems to be a fairly well-known 'deep dive'). I want to do multiple dives/day, spread over 2-3 days.
Do the computer tables take into account things like surface intervals, residual nitrogen loading, and the like?
Yeah, you can run repetitive dives over multiple days with the deco programs.
So, in these kinds of cases, it wouldn't be advisable to use 'standard' tables, but instead either bring you Deco laptop with you on a trip, or plan the trip ahead of time, and *stick* to the trip. Is this a fair assumption? (It would seem to me that this would be overly restrictive, since when doing a trip like the Doria, you don't have a lot of control over things like surface intervales, since that is often dictated by the weather as well as your boat-mates).
It seems in this case, you'd want a deco computer, either strapped to your wrist (*gasp*, am I a hertic?) or more preferrable a laptop that you can use to calculate a new profile for your next dives.
I've got another question re:deco procedures as well, but I'll do it in another post.
VTWarrenG
Guest
Yoop,
I know where you're coming from re: posting on an open forum.
I sorta like the concept that prior dives are irrelevant. If you deco properly, you're 90% decompressed by the time you break the surface. The last 10% takes many hours, and is neglible when compared to the on-gassing you experience during your next dive. Essentially, if you finish dive 1 with x "amount" of nitrogen in your system, you're going to ongas 100x on your next dive. If you deco conservatively enough, that 1 part in 100 is irrelevant.
GI has also mentioned the first-dive-deep-second-dive-shallow rhetoric is just a paradigm that has yet to shift. He contends it was a choice made long ago when less was understood about physiology, and is now just an arbitrary choice. He does his shallow dives first, followed by his deep dives. The WKPP avoids bounce dives after deep excursions because of the concept that a bounce dive allows venous bubbles to pass through the lungs into the arteries. The theory sounds plausible, but I hear it is yet to be proven.
All in all, we're in an exciting time, because deco theory and understanding is making great strides every year!
- Warren
I know where you're coming from re: posting on an open forum.
I sorta like the concept that prior dives are irrelevant. If you deco properly, you're 90% decompressed by the time you break the surface. The last 10% takes many hours, and is neglible when compared to the on-gassing you experience during your next dive. Essentially, if you finish dive 1 with x "amount" of nitrogen in your system, you're going to ongas 100x on your next dive. If you deco conservatively enough, that 1 part in 100 is irrelevant.
GI has also mentioned the first-dive-deep-second-dive-shallow rhetoric is just a paradigm that has yet to shift. He contends it was a choice made long ago when less was understood about physiology, and is now just an arbitrary choice. He does his shallow dives first, followed by his deep dives. The WKPP avoids bounce dives after deep excursions because of the concept that a bounce dive allows venous bubbles to pass through the lungs into the arteries. The theory sounds plausible, but I hear it is yet to be proven.
All in all, we're in an exciting time, because deco theory and understanding is making great strides every year!
- Warren
I know you should never deviate from your plan, but sometimes stuff happens and it's time for Plan B.
LY mentions he has some tables for different depths and times, but what happens when you stay down too long (found a great relic, got silted out in a wreck, O-ring blew, etc..)
As I understand, the tables are generated with certain assumptions (depth and time), and when you violate one, the table is no longer useful. (True?)
Example:
The plan is 240' for 40 minutes, and I have tables for this. However, I found a porthole, and I stay down for 45 minutes, longer than my table is setup to do.
What now? Obviously, (at least to me), pre-calculated tables can't take into account all of the different possibilities there are.
I'm guessing the answer to this question is
"Don't do technical/deco diving unless you are absolutely committed to your plan, and do not deviate from it."
I can see alot of really good arguments for this, and any budding technical diver *must* be willing to follow these rules to the letter.
However, when I read about the WKPP divers going down into the caves they have *NO* idea how long they are going to be under when they are extending the line. GI3 has a some-what famous post where he talks about extending the line from 14K to 18K. Prior to the dive, he had no idea how long he was going to be down, so how can you plan for such a dive? Do you generate saturate tables for the maximum depth and use them? (I don't think so, since according to the articles I'm reading, even the dives the WKPP folks are doing aren't saturation dives).
UP, what does your Tech 1 course say to this? My DIR-F course didn't talk to *anything* like this. (FWIW, I consider this a good thing, since DIR-F is geared towards rec-diving, and not deco/tech diving)
LY mentions he has some tables for different depths and times, but what happens when you stay down too long (found a great relic, got silted out in a wreck, O-ring blew, etc..)
As I understand, the tables are generated with certain assumptions (depth and time), and when you violate one, the table is no longer useful. (True?)
Example:
The plan is 240' for 40 minutes, and I have tables for this. However, I found a porthole, and I stay down for 45 minutes, longer than my table is setup to do.
What now? Obviously, (at least to me), pre-calculated tables can't take into account all of the different possibilities there are.
I'm guessing the answer to this question is
"Don't do technical/deco diving unless you are absolutely committed to your plan, and do not deviate from it."
I can see alot of really good arguments for this, and any budding technical diver *must* be willing to follow these rules to the letter.
However, when I read about the WKPP divers going down into the caves they have *NO* idea how long they are going to be under when they are extending the line. GI3 has a some-what famous post where he talks about extending the line from 14K to 18K. Prior to the dive, he had no idea how long he was going to be down, so how can you plan for such a dive? Do you generate saturate tables for the maximum depth and use them? (I don't think so, since according to the articles I'm reading, even the dives the WKPP folks are doing aren't saturation dives).
UP, what does your Tech 1 course say to this? My DIR-F course didn't talk to *anything* like this. (FWIW, I consider this a good thing, since DIR-F is geared towards rec-diving, and not deco/tech diving)
OP
Lost Yooper
Guest
That a good question, Doug. As we both know, helium enters and exits tissues very rapidly. Like nitrogen bends and oxygen bends, you can get helium bends from screwing up on deco. This would be a good one for one of the docs to expain more thoroughly than I can.
The bottom line is that helium comes out quicker -- something like 2-3 times as fast as nitrogen -- I don't have a book in front of me. This is why deco times on trimix are comparable to air on short shallower dives and much less for deeper and longer dives.
Take care.
Mike
The bottom line is that helium comes out quicker -- something like 2-3 times as fast as nitrogen -- I don't have a book in front of me. This is why deco times on trimix are comparable to air on short shallower dives and much less for deeper and longer dives.
Take care.
Mike
VTWarrenG
Guest
Yoop,
Diffusivity of He is 2.7 times that of N2.
- Warren
Diffusivity of He is 2.7 times that of N2.
- Warren
Yoop,
I know where you're coming from re: posting on an open forum.
I sorta like the concept that prior dives are irrelevant. If you deco properly, you're 90% decompressed by the time you break the surface.
Except that all of the current models assume that the surface is a 'decompression stop'. At least, that's my reading of the models from the experts on decompression (see LY's previously posted URLs).
You might be 90% decompressed (BTW, I'd like to hear where this number comes from), but you still have some residual nitrogen levels.
(This is especially important when you discuss things like flying after diving. Many of the current WKPP/DIR folks believe that you should be able to dive moments after doing a deco dive, which I believe to be utter foolishness. It's their life to do as they please, but I'd hate to be on the same plane if one of them had a DCS hit during a flight.)
The last 10% takes many hours, and is neglible when compared to the on-gassing you experience during your next dive.
I don't buy that argument. The tissues that would still be loaded are almost certainly the ones with the lowest half-lives, and as such take a very long time to completely off-gas. (This is why He is such a great back gas to use, since it comes out of tissue *MUCH* faster than N2, and as such deco happens more quickly.)
Also, I'd like to see some basis for '90% decod' after using a particular set of tables come from.
GI has also mentioned the first-dive-deep-second-dive-shallow rhetoric is just a paradigm that has yet to shift.
Actually, this is fairly common. Many of the articles on decompression theory explain this as well. It's not rhetoric so much as the lingering effect of our previous lack of knowledge in understand deco theory. When in doubt, be more conservative, especially when it comes to your life.
He contends it was a choice made long ago when less was understood about physiology, and is now just an arbitrary choice.
We're in violent agreement, although I'm more convinced from the deco papers from the mid-90's than in GI3's experience.
GI3 and the WKPP folks are not what I consider to be 'normal'. They are in *way* better shape than most recreational divers, and in better shape than even most technical divers. They have a heavily regimented lifestyle (most, if not all WKPP divers are vegans), and Doppler studies of GI3 show that at least he is more resistant to DCS/bubbling than the average diver. (This could be related to his lifestyle, genetics, or the phase of the moon, but at this time we really don't know why).
Applying his experiences to the rest of the world w/regard to deco (something that varies from day to day in an individual, let alone the variations across individuals) is something that shouldn't be done lightly. Just because he can deco in half the time that the Navy tables doesn't mean his tables are better.
On the other hand, neither can his experiences be ignored, and what I'm seeing in the literature is that their *results* aren't being ignored. They are pressing the envelope and their experiences are causing experts to re-examine some of their assumptions to try and explain
why these folks aren't getting DCS.
IMO, the answer is a combination of personal physiology, experience, and a little bit of luck.
All in all, we're in an exciting time, because deco theory and understanding is making great strides every year!
Amen to that
I know where you're coming from re: posting on an open forum.
I sorta like the concept that prior dives are irrelevant. If you deco properly, you're 90% decompressed by the time you break the surface.
Except that all of the current models assume that the surface is a 'decompression stop'. At least, that's my reading of the models from the experts on decompression (see LY's previously posted URLs).
You might be 90% decompressed (BTW, I'd like to hear where this number comes from), but you still have some residual nitrogen levels.
(This is especially important when you discuss things like flying after diving. Many of the current WKPP/DIR folks believe that you should be able to dive moments after doing a deco dive, which I believe to be utter foolishness. It's their life to do as they please, but I'd hate to be on the same plane if one of them had a DCS hit during a flight.)
The last 10% takes many hours, and is neglible when compared to the on-gassing you experience during your next dive.
I don't buy that argument. The tissues that would still be loaded are almost certainly the ones with the lowest half-lives, and as such take a very long time to completely off-gas. (This is why He is such a great back gas to use, since it comes out of tissue *MUCH* faster than N2, and as such deco happens more quickly.)
Also, I'd like to see some basis for '90% decod' after using a particular set of tables come from.
GI has also mentioned the first-dive-deep-second-dive-shallow rhetoric is just a paradigm that has yet to shift.
Actually, this is fairly common. Many of the articles on decompression theory explain this as well. It's not rhetoric so much as the lingering effect of our previous lack of knowledge in understand deco theory. When in doubt, be more conservative, especially when it comes to your life.
He contends it was a choice made long ago when less was understood about physiology, and is now just an arbitrary choice.
We're in violent agreement, although I'm more convinced from the deco papers from the mid-90's than in GI3's experience.
GI3 and the WKPP folks are not what I consider to be 'normal'. They are in *way* better shape than most recreational divers, and in better shape than even most technical divers. They have a heavily regimented lifestyle (most, if not all WKPP divers are vegans), and Doppler studies of GI3 show that at least he is more resistant to DCS/bubbling than the average diver. (This could be related to his lifestyle, genetics, or the phase of the moon, but at this time we really don't know why).
Applying his experiences to the rest of the world w/regard to deco (something that varies from day to day in an individual, let alone the variations across individuals) is something that shouldn't be done lightly. Just because he can deco in half the time that the Navy tables doesn't mean his tables are better.
On the other hand, neither can his experiences be ignored, and what I'm seeing in the literature is that their *results* aren't being ignored. They are pressing the envelope and their experiences are causing experts to re-examine some of their assumptions to try and explain
why these folks aren't getting DCS.
IMO, the answer is a combination of personal physiology, experience, and a little bit of luck.
All in all, we're in an exciting time, because deco theory and understanding is making great strides every year!
Amen to that
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