Tony, I didn't take it as a broadside...
Hence my: *** (sorta)***
You were almost too subtle...
And the point you make in your post above is very important not only for others but for me as well... I appreciate your pointing it out.
Is a long safety stop beneficial?
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Hence my: *** (sorta)***
You were almost too subtle...
And the point you make in your post above is very important not only for others but for me as well... I appreciate your pointing it out.
The Iceni
Medical Moderator
100 days said
". . .this seems to indicate there is a point at which there are diminishing returns in too slow an ascent rate from longer dives."
I hope you don't think that is what I was saying! I was just going back to basic principles so we could decide on this proposed extended 6 metre stop.
I have to agree 100% with Ungle Pug who said
"The best course is to do minimum deco stops for all dives within the NDL of 1 minute at 30', 20', and 10' with very slow ascent rates between stops and especially the last stop to surface. This is not staged decompression diving... it is prudent NDL diving... "
At least I think that is what I was trying to say. No point hanging about at 6 metres any longer than you have to, but you must, must, must ascend slowly as you approach the surface!
I think we are now all agreed.
". . .this seems to indicate there is a point at which there are diminishing returns in too slow an ascent rate from longer dives."
I hope you don't think that is what I was saying! I was just going back to basic principles so we could decide on this proposed extended 6 metre stop.
I have to agree 100% with Ungle Pug who said
"The best course is to do minimum deco stops for all dives within the NDL of 1 minute at 30', 20', and 10' with very slow ascent rates between stops and especially the last stop to surface. This is not staged decompression diving... it is prudent NDL diving... "
At least I think that is what I was trying to say. No point hanging about at 6 metres any longer than you have to, but you must, must, must ascend slowly as you approach the surface!
I think we are now all agreed.
100days-a-year
Contributor
DrPaul,we are all in agreement.My point was mostly in semantics.It is so easy to mis-construe anothers meaning given the variety of languages,dialects and educational levels present.You'all couldna unnerstood my uzhual speech,I am literate only thanks to a keyboard doncha know.
It is easy to see why training agencies are apt to stick with a poor solution rather than try to get a new one understood by the masses.....that and frivolous litigation.Personally I use 60fpm>100' 30fpm 100'-30' <10fpm from30' no stops unless directed by either computer or tables.Waiting for a computer with a Doppler detection sensor.
It is easy to see why training agencies are apt to stick with a poor solution rather than try to get a new one understood by the masses.....that and frivolous litigation.Personally I use 60fpm>100' 30fpm 100'-30' <10fpm from30' no stops unless directed by either computer or tables.Waiting for a computer with a Doppler detection sensor.
Dr Deco
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Dear Readers:
The idea of combining a Doppler bubble detector with a decompression computer is interesting but not as useful as it might seem. This is because there is a considerable delay between the appearance of gas bubbles in the blood stream and the occurrence of unfavorable supersaturation. This means that gas bubbles will be found at some duration after you have exceeded the safe stop or surfacing depth. When you hear the bubbles, it will already be too late. :upset:
This does not mean that a diver cannot pause at some stop depth for decompression until the bubbles cease. It is just that this will not occur in most cases in recreational dives until they have reached the surface. We are therefore speaking more of monitoring during the surface interval rather than at a stop. If this were done, probably a separate Doppler device would work better than something built into a dive computer. One could certainly input the Doppler information into the computer and have it estimate a more appropriate surface interval. This might be until all of the bubbles are gone; in this case, only the Doppler device is needed.
Individually tailored decompression profiles were the early goals of the Doppler researchers (in the 1970s), but this did not work out.
Dr Deco
:doctor:
The idea of combining a Doppler bubble detector with a decompression computer is interesting but not as useful as it might seem. This is because there is a considerable delay between the appearance of gas bubbles in the blood stream and the occurrence of unfavorable supersaturation. This means that gas bubbles will be found at some duration after you have exceeded the safe stop or surfacing depth. When you hear the bubbles, it will already be too late. :upset:
This does not mean that a diver cannot pause at some stop depth for decompression until the bubbles cease. It is just that this will not occur in most cases in recreational dives until they have reached the surface. We are therefore speaking more of monitoring during the surface interval rather than at a stop. If this were done, probably a separate Doppler device would work better than something built into a dive computer. One could certainly input the Doppler information into the computer and have it estimate a more appropriate surface interval. This might be until all of the bubbles are gone; in this case, only the Doppler device is needed.
Individually tailored decompression profiles were the early goals of the Doppler researchers (in the 1970s), but this did not work out.
Dr Deco
:doctor:
100days-a-year
Contributor
Thanx Doc,I was thinking more along the line of Tri-Mix or long deco dives.Would the info be more relavent by the time you were starting your 10' stop say 30 min to an hour into deco?
rcohn
Guest
Thanks Doc,
Why didn't tailoring decompression using the Doppler ultrasound work? It seems that some of the tech divers today are tailoring their decompression based on how well they feel after a dive. Any idea how that would compare to using Doppler ultrasound to determining how sucessful a decompression profile was?
Thanks.
Ralph
Why didn't tailoring decompression using the Doppler ultrasound work? It seems that some of the tech divers today are tailoring their decompression based on how well they feel after a dive. Any idea how that would compare to using Doppler ultrasound to determining how sucessful a decompression profile was?
Thanks.
Ralph
FastDen
Registered
Hi-
I'm by no means even a semi-knowledgable diver on this subject, but for what it's worth:
I ususally take a pretty long safety stop at 20ft, coupled with as slow an ascent as I can manage, since I've not heard or read anything so far that would indicate that a long safety stop is problematic. I use the stop to practice fine-tuning my bouyancy --staying still at 20ft without using a line, with a fairly empty tank, and in a current (like in Cozumel) isn't as easy as it sounds, at least to this relatively new diver!
And I actually enjoy the slow ascent- it's the finale to the dive, the last few moments in the water, and a great time to practice....ascending! I can't figure out why anyone in their right mind would "pop" to the surface anyway- unless they don't mind (possibly) getting hit by a boat!
FastDen :rainbow:
I'm by no means even a semi-knowledgable diver on this subject, but for what it's worth:
I ususally take a pretty long safety stop at 20ft, coupled with as slow an ascent as I can manage, since I've not heard or read anything so far that would indicate that a long safety stop is problematic. I use the stop to practice fine-tuning my bouyancy --staying still at 20ft without using a line, with a fairly empty tank, and in a current (like in Cozumel) isn't as easy as it sounds, at least to this relatively new diver!
And I actually enjoy the slow ascent- it's the finale to the dive, the last few moments in the water, and a great time to practice....ascending! I can't figure out why anyone in their right mind would "pop" to the surface anyway- unless they don't mind (possibly) getting hit by a boat!
FastDen :rainbow:
Dr Deco
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Dear Ralph:
There are several problems with Doppler bubble detection and decompression.
[sp][1.] The early (1970s) use of Doppler bubble detection to monitor the ascent for a diver was unsuccessful. It was initially believed that bubbles would appear just prior to DCS. This was in accordance with the Haldane concept of DCS. In actuality it was found that many divers on US Navy tables demonstrated gas bubbles in the venous system and never got the bends. It became clear that venous bubbles and DCS were not related (ie, "silent bubbles"), and this type of deco monitor was not operationally feasible.
[sp][2.] The current idea of DCS is that bubbles that form in a localized area of the body sre the cause. Circulating gas bubbles have little to do with the joint-pain process.
[sp][3.] The bubbles detected with the Doppler devices arise primarily in the muscle and adipose (= fat) tissues. These tissues are not responsible for joint-pain DCS. There is therefore a disconnect between the bubbles in muscles and those in tendon and ligaments (the latter probably are related to DCS).
[sp][4.] In recreational diving, the incidence of DCS is very low and likewise the Spencer-Johanson bubble grades are low, or zero (mostly). It is therefore difficult to titrated the biomarker when there is not biomarker. This is different from altitude decompression where the incidence of venous (Doppler) bubbles is appreciable.
[sp][5.] The divers who use oxygen in their decompression find that they are less lethargic and feel better. This is an actual (apparently) improvement and results in what would presumably be a better decompression. I can imagine that the bubble grades would change in these two situations (with and without more oxygen, or deep stops). This is by no means certain however, and I would be very curious, if someone were to actually test it (Doppler monitoring), what were the results.
[sp] This is a variety of information that I would not be able to obtain in my present work situation (at NASA), since we do not deal with scuba diving.
If I think of something else, I will add to the posting.
Dr Deco:doctor:
There are several problems with Doppler bubble detection and decompression.
[sp][1.] The early (1970s) use of Doppler bubble detection to monitor the ascent for a diver was unsuccessful. It was initially believed that bubbles would appear just prior to DCS. This was in accordance with the Haldane concept of DCS. In actuality it was found that many divers on US Navy tables demonstrated gas bubbles in the venous system and never got the bends. It became clear that venous bubbles and DCS were not related (ie, "silent bubbles"), and this type of deco monitor was not operationally feasible.
[sp][2.] The current idea of DCS is that bubbles that form in a localized area of the body sre the cause. Circulating gas bubbles have little to do with the joint-pain process.
[sp][3.] The bubbles detected with the Doppler devices arise primarily in the muscle and adipose (= fat) tissues. These tissues are not responsible for joint-pain DCS. There is therefore a disconnect between the bubbles in muscles and those in tendon and ligaments (the latter probably are related to DCS).
[sp][4.] In recreational diving, the incidence of DCS is very low and likewise the Spencer-Johanson bubble grades are low, or zero (mostly). It is therefore difficult to titrated the biomarker when there is not biomarker. This is different from altitude decompression where the incidence of venous (Doppler) bubbles is appreciable.
[sp][5.] The divers who use oxygen in their decompression find that they are less lethargic and feel better. This is an actual (apparently) improvement and results in what would presumably be a better decompression. I can imagine that the bubble grades would change in these two situations (with and without more oxygen, or deep stops). This is by no means certain however, and I would be very curious, if someone were to actually test it (Doppler monitoring), what were the results.
[sp] This is a variety of information that I would not be able to obtain in my present work situation (at NASA), since we do not deal with scuba diving.
If I think of something else, I will add to the posting.
Dr Deco:doctor:
GI and JJ and the rest of the WKPP have done extensive doppler testing after their dives. The tests were conducted scientifically and yielded a great deal of information, I believe. This seems to be the kind of information that you're looking for. I'm not sure where (and if) the results were published/are available, but perhaps someone else does. You could always contact GI for the information.
100days-a-year
Contributor
:idea:Thanx Doc,I understand now.So it would seem that a clean Doppler sample post dive would be indicative of a "clean"deco but during the dive it would not be indicating accurately the phenomena of localised bubbles in cartilaginous tissue?
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