Talk:Trimix (breathing gas)

Untitled
Edit conflict, now merging. --mav

Collabi 04:16 Dec 15, 2002 (UTC): Heh, sorry about that; I guess I took your advice a little too swiftly to heart.

Trimix is also a type of intercavernosal injected erectile dysfunction therapy. Containing three vasodiolators, including papaverine, phentolamine and PGE1, it is administered via direct intercavernosal injection in to the side of the penis, in a similar manner to the more well known Caverject. Like Caverject, it is typically effective in most men, producing an uncommanded full erection for approximately 1 hour depending on the quantity used. Unlike oral ED therapies, no direct stimulation is required, and it can be used by patients who cannot tolerate traditional ED drugs such as Viagra. —Preceding unsigned comment added by 69.180.28.120 (talk) 20:38, 26 January 2008 (UTC)

Off gassing
The articles states: "Helium off-gasses rapidly and it does not enter slow tissues as readily as nitrogen" (emphasis added). My understanding was that the reverse was true - helium actually enters tissues faster than nitrogen, but because it off gasses faster, the penalty is limited, and deep divers consider it an acceptable trade off for the reduction in narcosis. Does anyone have citations (for either view)? --Legis (talk - contribs) 19:22, 27 July 2008 (UTC)


 * That sentence is not well-phrased. Graham's Law postulates that the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight. The result is that both on-gassing and off-gassing will be faster for He (molecular weight = 4) than for N2 (M.W. = 28) by a factor of sqrt(7) if classical diffusion is the predominant mechanism of gas exchange.
 * However, I suspect that the sentence was also alluding to the fact that N2 is much more soluble in both water and lipids  than He (the second ref is probably not a WP:RS, but illustrates a table in "The Physiology and Medicine of Diving" by Peter Bennett and David Elliott, which is as good a cite as I can find). This is of course mainly of relevance to saturation diving where the total load of He is much less that would be if N2 were used.
 * Be WP:BOLD and reformulate the article to match your understanding - I'm sure we can find good cites (or probably User:Gene Hobbs can!) to back it up. Cheers --RexxS (talk) 10:35, 28 July 2008 (UTC)

David Shaw
According to David Shaw (diver) he was trying to recover a body found during an earlier record dive and not commencing a record dive itself. Maybe this article should be corrected? --Anttix (talk) 22:02, 21 August 2009 (UTC)
 * No, Deon Dreyer died on a comparatively shallow dive, and his body fell to the depths where Shaw located and tried to recover it. --Legis (talk - contribs) 02:36, 22 August 2009 (UTC)

Hyperoxic mix
Folks, the article uses the term 'hyperoxic' to refer to low O2, shouldn't it be 'hypoxic'. The section says "In fully closed circuit rebreathers that use trimix diluents, the mix can be hyperoxic in shallow water because the rebreather automatically adds oxygen to maintain a specific ppO2." 70.91.78.109 (talk) 15:10, 24 August 2009 (UTC)


 * No, it correctly uses 'hyperoxic' to refer to mixes that have more than 21% O2. In that section, it explains that in shallow water, the fraction of oxygen may exceed 21%. For example, with the ppO2 set to 1.4 bar, at 10 metres depth, you'd be breathing 70% O2 (2 bar ambient x 70% = 1.4 bar). Hope that helps. --RexxS (talk) 17:38, 24 August 2009 (UTC)

Photo?
Does anyone have a photo that could add a bit of visual punch to the article? Even a simple shot like a pair of doubles with a custom mix or trimix stickers on them, or a blending station. I think articles just look very dry without any images at all. --Legis (talk - contribs) 16:04, 24 November 2009 (UTC)


 * I cropped Mark Murphy's photo to use in Nitrogen narcosis - it's available at File:Gas blending equipment cropped.jpg, but although it's a station, it's not very "punchy". However, there's a cave diver called Andrew Ward – – who has lots of photos that he kindly pointed me to:
 * http://www.lot46.com/
 * http://a-m-ward.blogspot.com/
 * http://www.flickr.com/photos/amward
 * Work your way through that lot and see what you think! You can see our conversation at User talk:RexxS. I'm sure if we asked him to release a picture, he'd be happy to do so (although we might have to guide him through the process). See if you can find one or two that would fit what you want for this article. --RexxS (talk) 20:40, 24 November 2009 (UTC)

Merge proposal
Proposal is to merge Heliair into Trimix (breathing gas) as a section. Heliair is a subset of Trimix and will fit seamlessly into this article. Peter (Southwood) (talk): 18:57, 4 November 2011 (UTC)
 * Sorry I neglected to comment on this earlier, Peter. Heliair would fit perfectly as a section of this article, I'd just merge and redirect Heliair to the section. You could drop a note to Mark Murphy's talk page as he was the original author. --RexxS (talk) 23:40, 1 March 2012 (UTC)
 * Done, I will leave it a few days in case he wants to comment. Peter (Southwood) (talk): 06:29, 2 March 2012 (UTC)
 * Fine by me. Mark.murphy (talk) 23:21, 3 March 2012 (UTC)

Standard ratios
The section on standard mixes doesn't really clearly specify which number in the ratios are oxygen and which are helium. It should be stated clearly whether it's a helium to oxygen ration or oxygen to helium. — ★ Parsa ☞ talk 17:14, 1 March 2012 (UTC)
 * Two sections earlier (Naming), it spells out that the first number is oxygen and the second is helium. I accept that someone who only read one section of the article would not have that understanding. Perhaps you can suggest an alternative form of words for "a number of "standard" mixes have evolved (such as 21/35, 18/45 and 15/55)" that is not too cumbersome? --RexxS (talk) 23:33, 1 March 2012 (UTC)
 * I have made edits which may satisfactorily deal with this problem. Cheers Peter (Southwood) (talk): 06:49, 2 March 2012 (UTC)

Partial Pressure Units
Sorry about this, but I take objection to use of numbers without units.

''Advantages of reducing oxygen in the mix

Lowering the oxygen content increases the maximum operating depth and duration of the dive before which oxygen toxicity becomes a limiting factor. Most trimix divers limit their working oxygen partial pressure [PO2] to 1.4 and may reduce the PO2 further to 1.3 or 1.2 depending on the depth, the duration and the kind of breathing system used [open circuit vs closed circuit rebreather].[1][2][6][7]''

I assume these partial pressures are in bars as these units are used later in the article? I dare not edit it directly as the choice of pressure units is speculation on my part... Tony.wallace.nz (talk) 08:58, 4 March 2012 (UTC)
 * Quite correct, bar or atm would be the appropriate units (they are close enough in value for this purpose to be considered the same within the customary tolerances) and thanks for pointing it out. Cheers, Peter (Southwood) (talk): 15:58, 4 March 2012 (UTC)

Maximum ppO2
The bald recommendations of 1.2 bar, 1.4 bar, 1.6 bar as maximum partial pressure of oxygen in different circumstances obscure the considerable nuances surrounding those values. The issues were discussed at length in and it is fascinating reading for anyone interested in seeing what evidence was considered and how large a margin of safety was incorporated into those numbers. I'm not sure to what extent the material in that pdf ought to be included in this encyclopedia article, but some may feel that there could be an elaboration on the 'fuzziness' of the current limits. Thoughts? --RexxS (talk) 19:06, 4 March 2012 (UTC)
 * Do you think this article is the best place to go into that sort of detail? I will read the DAN workshop proceedings, that sort of information should go somewhere, but is Trimix the place. Maybe an article on the practical aspects of Oxtox in diving: How to avoid it, the risks, CNS clock, Repex tables etc? Cheers, Peter (Southwood) (talk): 21:06, 4 March 2012 (UTC)
 * I actually doubt that this is the place for much more detail, but I wanted other opinions to make sure that it wasn't just my bias. The workshop proceedings are absolutely fascinating as it reads like a playscript in parts, and shows how the personalities involved shaped how our current recommendations were arrived at. Most contributors thought 1.6 bar was fine (which of course it is except for a tiny number of extra-susceptible people), and 1.4 bar really evolved from that as sort of "let's be absolutely certain", although the military decided they'd stick with 1.2 bar, because ... well, because they could? The current paranoia about exceeding 1.4 bar is probably a good thing because it keeps folks well away from any possibility of problems, but it does sometimes strike me as "Beyond this, there be dragons!" Cheers --RexxS (talk) 23:35, 4 March 2012 (UTC)

Heat loss from trimix
I just reverted this text: because it is unsourced and replaced text that was sourced. It would be interesting to see how much of the above can be salvaged by being cited to reliable sources. The stuff about capillaries is pure red herring because it occurs whether air, argon or helium is used to inflate the drysuit. Everyone I know who dives dry in very cold conditions agrees that they are warmer using argon, but that's anecdote, not sourcing. Similarly, the poster 125.60.195.229 has a point that heat is lost through breathing out helium (although a given volume of air has a higher heat capacity than the same volume of helium †) - but only if you're open-circuit. Helium mixtures, including trimix, in a rebreather soon warm up the gas in the loop and I don't believe they represent the main source of heat loss in that scenario. I always feel that my head is the main source of heat loss, but that's probably because I can't stand a hood that's too tight or too thick. Anyway, that's anecdote as well, but so is the text above unless somebody can find a reliable source that supports it.
 * "The main source of heat loss in a diver using trimix is through breathing. One of defense mechanism for a body being cooled is for a the capillaries in the extremities to contract so as to conserve heat in the body core. This results in a cold feeling to the skin.Often helium breathing divers carry a separate supply of a different gas to inflate drysuits. This is mistakenly to avoid the risk of hypothermia caused by using helium as inflator gas. Argon, even though differences in heat loss due to changing the drysuit inflator gas is minimal."

† Air has a specific heat Cp of about 1 kJ/kg K, while He has Cp of 5.2 kJ/kg K. But air has a molecular weight over 7 times that of He, which means a given volume of air will take about 7/5 times the amount of heat per degree of warming as He requires for the same volume and pressure. Helium is of course 6 times more conductive to heat than air, but that's not what 125.60.195.229 was acknowledging. --RexxS (talk) 00:23, 20 September 2012 (UTC)

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