Spectre
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Well, what are you considering to be 'helium DCS'? People getting bent on HeliOx, or people getting bent on Trimix?
Helium
- Thread starter madisonbadger
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From what i gather from the posts so far in the thread from MadisonBadger, it would seem that they are questioning when trimix might be used, the risks of it in terms of DCS like symptoms and applicability when used in shallower depths (<150 or so) compared to other gas mixes that are common. Trying to organise the various bits of info from around the web regarding stops etc to weigh up the likelihood or desire to take such courses or just general knowledge accumulation to prepare for later use in courses (of course the course would tell you what you want to know, but you dont know what to ask until you have already been taught it - nice viscious circle!).Spectre:
I read a good intro section on various gases, their uses and applicability in the cave diver manual (NSS-CDS), but couldnt completely reproduce the general info off the top of my head, but it seemed to cover the risks and such in there. However compared to other gas mix books out there, this was only an intro text i felt, but that might suffice for you if you have access to it.
lragsac
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madisonbadger:
If I am interpreting Dr. Powell's response correctly...
"Last, you can not escape Supersaturation by employing two gases. At one time it was suggested that a mix of many gases would keep each below its metastable limit and prevent bubble formation. I guess that they thought that when bubbles did form, each gas would be in a separate bubble. That would be a nice way of sorting and purifying gases. Needless to say, it is theoretically incorrect and does not work."...
then it would seem that, at least when diving trimix, it would be impossible to determine which inert gas was the "culprit" in cases of DCS.
Dr. Powell, if you are reading, is this a tenable conclusion?
OP
madisonbadger
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if you dive heliox lets say 130 feet
30% oxygen
70% helium
for 30 minutes and you simply go to the surface at 60 feet per minute.
lets say you had DCS from that experience. How would the decompression chamber modify the treatment due to helium being the major consituant of your breathing gas?
has there ever been a case of someone experiencing DCS from heliox?
seaching the internet I have found several bits of writing indicating how dangerous helium is due to its different ongas and offgas properites.
I wanted to see if there was quantifable evidence regrading the indicence of DCS and how helium has played a part. I shy away from the theories about "it must be...." or "it seems possible because..."
just looking for hard evidence so that I can make an informed decision.
30% oxygen
70% helium
for 30 minutes and you simply go to the surface at 60 feet per minute.
lets say you had DCS from that experience. How would the decompression chamber modify the treatment due to helium being the major consituant of your breathing gas?
has there ever been a case of someone experiencing DCS from heliox?
seaching the internet I have found several bits of writing indicating how dangerous helium is due to its different ongas and offgas properites.
I wanted to see if there was quantifable evidence regrading the indicence of DCS and how helium has played a part. I shy away from the theories about "it must be...." or "it seems possible because..."
just looking for hard evidence so that I can make an informed decision.
Dr Deco
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Hello Iraqsac:
Mixed Gas DCS
Then it would seem that, at least when diving trimix, it would be impossible to determine which inert gas was the "culprit" in cases of DCS.
In a sense, all dissolved gas species contribute to bubble growth and stabilization. However, exactly what may be in bubbles in any one volume of tissue will depend on what gases are present. This depends on the rate of uptake and elimination of the dive gas in addition to what is in the breathing mix. To this must be added gas solubility and diffusability in the tissue surrounding the bubbles. Since these are not the same for helium and nitrogen, the composition of bubbles will be time dependent.
Analysis of (venous) bubbles will give a different internal gas mix than what you get from the breathing mix.
Additionally, one can have oxygen, carbon dioxide, and water vapor in bubbles. At high altitudes, these last three can result in DCS all by themselves.
Dr Deco :doctor:
Mixed Gas DCS
Then it would seem that, at least when diving trimix, it would be impossible to determine which inert gas was the "culprit" in cases of DCS.
In a sense, all dissolved gas species contribute to bubble growth and stabilization. However, exactly what may be in bubbles in any one volume of tissue will depend on what gases are present. This depends on the rate of uptake and elimination of the dive gas in addition to what is in the breathing mix. To this must be added gas solubility and diffusability in the tissue surrounding the bubbles. Since these are not the same for helium and nitrogen, the composition of bubbles will be time dependent.
Analysis of (venous) bubbles will give a different internal gas mix than what you get from the breathing mix.
Additionally, one can have oxygen, carbon dioxide, and water vapor in bubbles. At high altitudes, these last three can result in DCS all by themselves.
Dr Deco :doctor:
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