Helium

[madisonbadger]

thank you for the info.
I called the TDI shop I got certified at and the told me I needed to go through advanced Nitrox, which means a new reg for the 50% and above, deep air, and then trimix
The below are a few of the things I found using google. This is why I asked the question in the first place.

http://www.mtsinai.org/pulmonary/books/scuba/sectionl.htm

WHAT IS TRIMIX?

Trimix is a mixture of oxygen, helium and nitrogen. Nitrogen, usually in a small percentage (e.g., 15%), is added back to heliox to create trimix, in order to lessen the risk of the high pressure nervous syndrome seen with helium breathing. Nitrogen slows down nerve conduction.

Trimix is used for the deepest scuba dives, usually greater than 400 feet. Like Heliox, Trimix is strictly for non-recreational use: military, scientific, commercial, and advanced technical diving.

http://forums.deeperblue.net/archive/index.php/t-40642.html

Keith S.
December 19th, 2003, 11:10
On Thu, 18 Dec 2003 00:56:26 +0000, Rob Forey -- The Man With No Nails wrote:


> I, for example, get narced pretty shallow, around 30m. I would love to be able
> to enrol in a trimix course to decrease my narcosis at this depth, but there
> aren't any trimix courses available for the type of recreational diving I want
> to do. I know trimix is considered to be in the realm of technical diving and
> for use deeper than recreational limits, but surely it can still be of
> application to divers going to 30m? Why do I have to learn how to go to 50m on
> air and be able to do deco diving just to enrol in a course that decreases my
> narcosis? I fail to see how trimix and deco are inherently linked.

OK, let's consider you do an air dive to 30m for 20 mins. Something you
could do on air and get away with doing any deco if you follow PADI
tables and don't do their 'safety stop'.

Now you want to do the same dive on trimix to get less narcosis. You
choose 21/35 as your backgas - same as air but with an END of 12m, nice
eh? But wait, you've got 10 mins of stops to do now, according to DDPlan.
This is why trimix divers will always deco on something other than
backgas.

Now do you see why trimix and deco are 'inherently linked'?

_ keith

the same link as above farther down the page

Alasdair Allan
December 19th, 2003, 13:00
Imorital wrote:
> Does anyone think tmx diving is safe without deep stops?

As others have mentioned helium is very unforgiving of quick ascents, I
wouldn't dive it without putting in deep stops, I wouldn't regard it as
being safe...

Al.

Thank you all for your input. PS are there any double blind studies on oxygen narcotic value? I see numbers quoted all over the map.

I am sorry but I do not agree that just because a gas is nobel it won't form bubbles.

 

[chickdiver]

http://gue.com/classroom/tech1.shtml

This is an overview of the entry level GUE tech course. I beleive they also teach a strictly recreational version (RecTriox), but I don't have any info on it.

There are other normoxic trimix classes out there. These typically do not require Adv. Nitrox (since they are no- deco courses).

NAUI Tec also has a recreational Helitrox class (an instructor specified specialty)- check it out at http://runawaylobster.com/ScubaClasses/nauihelitrox.htm

 

[Charlie99]

The below are a few of the things I found using google. This is why I asked the question in the first place.

http://www.mtsinai.org/pulmonary/books/scuba/sectionl.htm


http://forums.deeperblue.net/archive/index.php/t-40642.html

It's all about tradeoffs. Let's assume that you do need to use a slower ascent and/or include short deep stops for what would otherwise be an NDL dive on air or nitrox. A lot of people find that to be a small price to pay compared to the value of reducing narcosis, and something like 30/30 trimix is their preferred gas for even short dives in the 100-120' range.

 

[lamont]

Agreed with Jeff and Charlie, from my understanding the only gas we can take a reasonable amount of at various depths (obviously oxtox being an issue) is Oxygen as we can use it (metabolise i think is the term), any other gasses are stored up in tissues and released back into the blood stream as pressure is reduced - this could be any gas, but typically nitrogen and helium are the most commonly used. Their reactivity (position on the periodic table) is pretty much a non-factor as we cant use these gases, so they are on-gassed on descent and during the dive and off-gasses on ascent, during stops and after the dive.

I think the deal with O2 (correct me if i've got this wrong) is that it binds to hemoglobin and therefore a lot of the O2 isn't a dissolved gas in the blood. I also think you can actually get O2 DCS, but you need to have very high ppO2s where you've saturated the binding of O2 to the hemoglobin and the O2 starts to just dissolve in the blood and behaves like any other dissolved gas.

It'd be cool if you could inject yourself with something that was biologically inert but behaved hemoglobin-like in binding to He or some other breathable gas that didn't cause issues at high partial-pressures. That should give you DCS-less diving if you could do it...

 

[simbrooks]

I think the binding thing is what i refer to as metabolising, same thing, different phrasing. We all know too much of a good thing is bad for you and that includes O2, we have the exposure limit tables for both short term/one off and longer term (24hr) that give us an idea of what are acceptable times at certain exposures (partial pressures), but beyond that i dont know, nor could hypothesise about O2 DCS style hits and saturating with O2 - have no medical training, nor advanced nitrox training, anyone else want to step in and advise yeh or ney?

 

[madisonbadger]

what drives the 25-30% in the "standard" mixes.
just trying to maximize the amount of HE before it becomes a deco issue?

I appreciate the help and the links provided.
Thank you for your time and have a good day

 

[BigJetDriver]

Mon ami, Charles,

The answer is actually: Right. Right. Right.

Originally Posted by CNTdiver
Due to helium being an inert and therefore considered a "noble gas", it cannot cause DCS.

Wrong. Wrong. Wrong.
If this were really true, we'd all just dive heliox and ignore decompression.

As I said on the first page when I answered the original poster, in essence, the inert gas (and here insert your choice of inert gas___________) does not, in and of itself, CAUSE a case of DCS to occur.

It is, of course, the situation in which the DIVER, for whatever reason, exceeds the allowable or critical dose-loading of that particular inert gas, and then changes his or her ambient pressure too rapidly, such that the inert gas attempts to equilibrate by coming out of the tissues and solutions in his or her body at a rate that is too fast which CAUSES a case of DCS (or "bubble-trouble" as Dick Rutkowski would say) to occur.

N'est pas, mon ami???

Rob

 

[MonkSeal]

I am a DAN member, do you think I should give them a call? I would hate to bother them with something like this.

I won't commnet those things how He is dangerous. In my opinion if you want to do recreational trimix do it with GUE if you have the oportunity. The path is DIR-F, Rec Triox. Diving rec triox doesn't have anything with advanced nitrox or deep air.

Regarding a being DAN member pay attention on policy conditions. AFAIK He diving is not covered with basic policy - additional coverage is needed.

 

[Dr Deco]

Hello readers:

Several questions are on this thread that I can address. Technical diving questions should go to a different forum.

Noble Gas DCS :umnik:

The fact that helium is chemically inert is not the reason that it is used for diving. Yes, it will form gas bubbles in a supersaturated condition. [Actually, as all readers of “Ask Dr Deco” should know, the bubbles are there already -- as micronuclei. Supersaturation must be above a certainly level to counteract the contracting pressure (“Laplace pressure”) resulting from surface tension of the water-bubble interface. You do remember that, do you not?)

Helium dissolves with pressure and can exsolve (yes, a real word) when the pressure is reduced. Nitrogen is inert at body temperature, and yet it will form bubbles. (Actually they grow from nuclei. Right?)

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.

“Oxygen Bends”

It is possible to demonstrate what is known as “oxygen bends.” Specifically, goats were exposed to pressures where they displayed evidence of DCS when decompressed. Then they were exposed to somewhat reduced pressure and no DCS presented. Then oxygen was added such that the pressure exceeded the first case. The goats displayed signs of severe DCS (actually it was a profusion of bubbles in the venous system) and the goats recovered shortly as the oxygen was metabolized.

Dr Deco :doctor:

 

[madisonbadger]

so to recap the original question,
Are there any case studies of Helium DCS?
I am trying to get a sense for %occuring, Severity of DCS, treatment schedule, and post treatment follow up, for helium DCS.
thank you for your time and have a good day.