richhagelin
Contributor
Is there a consensus among divers as to which "tables" are the most accurate/most used? PADI, NAUI, other.
Rich
Rich
Deco Tables
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Most used?
PADI RDP. PADI trains the majority of divers, therefore the tables they tach will be the most widly used.
Most accurate?
There is no accuracy. What do you mean by accurate? You want the one that pushes you to the last minute before getting bent? There are too many factors, differences between individuals, even differences for an individual from one time to another.
What I want is a table that is relatively safe. No table is completely safe. No table is absolutely the most conservative. No table is absolutely the most liberal. In general, DCIEM has very conservative tables as does YMCA. In general PADI's RDP is very liberal.
PADI RDP. PADI trains the majority of divers, therefore the tables they tach will be the most widly used.
Most accurate?
There is no accuracy. What do you mean by accurate? You want the one that pushes you to the last minute before getting bent? There are too many factors, differences between individuals, even differences for an individual from one time to another.
What I want is a table that is relatively safe. No table is completely safe. No table is absolutely the most conservative. No table is absolutely the most liberal. In general, DCIEM has very conservative tables as does YMCA. In general PADI's RDP is very liberal.
I would use any table out there for a recreational dive. The reason is that I don't dive to the limit of any table. You must also consider factors like temp, work load, health, phis cond, how you feel that day, how many days of diving and how many dives/day.
Assuming your using common sense, dive the tables you are the most comfortable with.
Assuming your using common sense, dive the tables you are the most comfortable with.
Dr Deco
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Dear Readers:
Recreational (No Decompression) Tables
All US recreational tables rather similar pedigrees, that it, they can trace the initial set of NDLs to the US Navy tables. After this, there will be some variations by the table designers. If these are for no-decompression diving, the results will be rather similar. British tables have a different origin as do the DCIEM tables, but the results are not all that different, since the results are dictated by nature. I am not aware of any field data that indicates that one recreational scuba table is superior to another.
In some cases, there will be modifications to the tables. This might be under microbubble stress. I guess I cannot argue with the general concept, but I believe that such an inclusion is more wishful thinking than anything else.
Deep Diving Decompression Tables
When we enter this arena, there will be differences. All tables are initially derived by actual dive data and later modified from field use (or some laboratory trials). This data will most likely vary, and the tables will thus differ from one another, a reflection of these inputs of data. I do not know the thinking of all table builders and therefore could not comment on why they did exactly what they did.
I personally believe that slower ascents are physiologically a good idea as are deeper stops. These views are based on the biophysics of nuclei in the body as well as some laboratory studies. In those cases where these are reflected in the table, I would be pleased with that design.
Buffer Zone
There is a zone were DCS is quite certain; this is only used in laboratory studies. Then there is a region where DCS is minimal and this is used in military and commercial tables where on site recompression is possible. Then there is a region where DCS is really quite rare (the recreational no-stop limits), but it can be provoked if divers exercise at depth and load inert gas, or exercise vigorously at surface and nucleate themselves.
The next range is that were DCS is not possible because nuclei in the body are not large enough or in an insufficient number. We see example of this when passengers are on a commercial airplane. At an equivalent cabin altitude of 8,000 feet, do individuals get the bends? Nope. That would require the presence of sufficient micronuclei of about nine microns in diameter. Evidently these do not exist. A diving situation requiring such nuclei diameters would likewise not elicit decompression sickness.:mean:
Dr Deco :doctor:
Recreational (No Decompression) Tables
All US recreational tables rather similar pedigrees, that it, they can trace the initial set of NDLs to the US Navy tables. After this, there will be some variations by the table designers. If these are for no-decompression diving, the results will be rather similar. British tables have a different origin as do the DCIEM tables, but the results are not all that different, since the results are dictated by nature. I am not aware of any field data that indicates that one recreational scuba table is superior to another.
In some cases, there will be modifications to the tables. This might be under microbubble stress. I guess I cannot argue with the general concept, but I believe that such an inclusion is more wishful thinking than anything else.
Deep Diving Decompression Tables
When we enter this arena, there will be differences. All tables are initially derived by actual dive data and later modified from field use (or some laboratory trials). This data will most likely vary, and the tables will thus differ from one another, a reflection of these inputs of data. I do not know the thinking of all table builders and therefore could not comment on why they did exactly what they did.
I personally believe that slower ascents are physiologically a good idea as are deeper stops. These views are based on the biophysics of nuclei in the body as well as some laboratory studies. In those cases where these are reflected in the table, I would be pleased with that design.
Buffer Zone
There is a zone were DCS is quite certain; this is only used in laboratory studies. Then there is a region where DCS is minimal and this is used in military and commercial tables where on site recompression is possible. Then there is a region where DCS is really quite rare (the recreational no-stop limits), but it can be provoked if divers exercise at depth and load inert gas, or exercise vigorously at surface and nucleate themselves.
The next range is that were DCS is not possible because nuclei in the body are not large enough or in an insufficient number. We see example of this when passengers are on a commercial airplane. At an equivalent cabin altitude of 8,000 feet, do individuals get the bends? Nope. That would require the presence of sufficient micronuclei of about nine microns in diameter. Evidently these do not exist. A diving situation requiring such nuclei diameters would likewise not elicit decompression sickness.:mean:
Dr Deco :doctor:
OP
richhagelin
Contributor
Dr Deco,
Thanks, great run-down
Rich
Thanks, great run-down
Rich
Scuba
Contributor
Dr Deco wrote:
Given that it is believed (by some) that microbubbles are bad news for DCS, will you please expound on this.
Given that it is believed (by some) that microbubbles are bad news for DCS, will you please expound on this.
Dr Deco
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Dear Scuba:
Lung Microbubbles
If I understand the manufacturers material, the microbubble feature refers to the presence of microbubbles (what are often referred to as Doppler bubbles) in the blood vessels of the lungs. The thinking goes that these bubbles will block the passage of blood and interfere with gas exchange in the alveoli. It would result in what is referred to by physiologists as a ventilation-perfusion inequality. The alveoli are not matched to the blood flow because of capillary blockage.
We took a look at this at NASA about ten years ago and found, to our surprise, that there is not any decrement in the exchange of inert gas even with high Spencer precordial bubble grades. Most likely this results from the actual dearth of gas bubble present in the venous blood return. While the Doppler device give indications that a vast armada of bubbles the size of the Goodyear blimp are in the circulatory system, this in fact is not true. Measurement, both directly (in sheep) and indirectly (in humans) indicate that there is not really a large volume of gas.
Tissue Bubbles
While there might not be any interference with gas exchange in the lungs, what about nuclei in tissues? Certainly if these bubbles were present, nitrogen would be sequestered (trapped in the bubble itself) and not released. This is a different matter and probably does occur. It is most likely accounted for by the long half time compartments, but that is another topic altogether.
So Whats the Problem?
My only gripe with all of this is that there is a continual addition of fiddle factors to models. The deco meters can not really correct for Dr Ds Trouble Spots. Only the diver can. Additionally I prefer to see the additions given some justification by a test program. We are long on models and short on tests in barophysiology. That is probably because it is relatively easy to adjust the model. A lot easier than testing.
Thank you, ladies and gentlemen. I will now climb down off my soapbox.:box:
Thanks for a very good question!
Dr Deco :doctor:
Lung Microbubbles
If I understand the manufacturers material, the microbubble feature refers to the presence of microbubbles (what are often referred to as Doppler bubbles) in the blood vessels of the lungs. The thinking goes that these bubbles will block the passage of blood and interfere with gas exchange in the alveoli. It would result in what is referred to by physiologists as a ventilation-perfusion inequality. The alveoli are not matched to the blood flow because of capillary blockage.
We took a look at this at NASA about ten years ago and found, to our surprise, that there is not any decrement in the exchange of inert gas even with high Spencer precordial bubble grades. Most likely this results from the actual dearth of gas bubble present in the venous blood return. While the Doppler device give indications that a vast armada of bubbles the size of the Goodyear blimp are in the circulatory system, this in fact is not true. Measurement, both directly (in sheep) and indirectly (in humans) indicate that there is not really a large volume of gas.
Tissue Bubbles
While there might not be any interference with gas exchange in the lungs, what about nuclei in tissues? Certainly if these bubbles were present, nitrogen would be sequestered (trapped in the bubble itself) and not released. This is a different matter and probably does occur. It is most likely accounted for by the long half time compartments, but that is another topic altogether.
So Whats the Problem?
My only gripe with all of this is that there is a continual addition of fiddle factors to models. The deco meters can not really correct for Dr Ds Trouble Spots. Only the diver can. Additionally I prefer to see the additions given some justification by a test program. We are long on models and short on tests in barophysiology. That is probably because it is relatively easy to adjust the model. A lot easier than testing.
Thank you, ladies and gentlemen. I will now climb down off my soapbox.:box:
Thanks for a very good question!
Dr Deco :doctor:
The Pirate
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Don't any of you guys use the BIG computer?
The Pirate
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