From Air to Trimix at depth

[shoredivr]

No I don't understand, any use of trimix, for what I have read the divers using trimix don't use air ( low % I think ), but my question was in case somebody had tried this or maybe as part of a tec class, just as to see the difference in state of mind or other.

The reason I mention CO2 is because the experts mention that the effects of CO2 mimic like the N2 narcotic effects.

Yes, I've switched from Trimix to air at 140' in the darker, colder waters of the St Lawrence River after a trimix class to see how it affected me on that day at that depth. With the 18/30 my perception was there was lots of light, I could see expansively and notice detail in the rocks. Switching to air, things got darker, my perception narrowed and details disappeared. This was a good lesson for me, as I'm quite comfortable at 150' on air. The amount of detail I lost was instructive.

 

[rivers]

Ever get a headache while working hard on a dive? CO2.
https://www.globalunderwaterexplorers.org/carbon-dioxide-narcosis-and-diving

 

[chrisch]

... Nitrogen narcosis and CO2 retention have a syngergistic effect and will significantly increase the narcotic effect than either alone.....

I think we are in danger of leaving the OP behind. CO2 retention is an important issue and another reason to use more helium. However, air doesn't have much CO2 in it - the CO2 is excreted by the body as a product of respiration. If the CO2 is exhaled then it is heading up the water column to the atmosphere. A small amount is re-inhaled as it is in the 2nd stage as the gas changes direction. The so called "dead space" of the regulator.

There's a big thread on it here: http://www.scubaboard.com/forums/basic-scuba-discussions/224684-co2-retention.html

 

[Lorenzoid]

Ever get a headache while working hard on a dive? CO2.
https://www.globalunderwaterexplorers.org/carbon-dioxide-narcosis-and-diving

That's the most comprehensive "CO2 article" I've seen yet. Thanks.


There are at least three recent threads about narcosis, CO2, and related factors, and I've gotten quite a bit out of them.

 

[Adobo]

Have you experience a significant change in your state of mind and behavior by switching from air to trimix at 40m depth ?

The question is pointed out to nitrogen narcosis.

I guess it you are under the influence of CO2 it dosen't matter if you switch from air to trimix right ?

Yes I have less than 25 dives, does it offend you that I'm asking this, then more likely you will give an anal answer, and I'm not askign for those answers, my questions is directed to the divers that want to aport a positive in educated answer from which I can learn and make questions in a class room later or in another discussion with other more experienced divers.

I understand why you ask that question - you want to know what data other divers have on A-B comparison of both breathing gases, all else being equal. There are a couple of problems with the question though:
- It would be odd for recreational (non-commercial) divers to switch from air to trimix during a dive. Or to switch from trimix to air. Whatever conclusions you might draw from the test might not be applicable to normal dives as one would not normally dive this way.
- Briefly switching from one bottom gas to another might give you an idea of benefits/drawbacks that become apparent immediately but will not give you an idea how each gas affects your performance over the entirety of the dive and perhaps even after the dive.
- Similarly, a brief switch in gases only gives you a data point under seemingly benign conditions. I assume that you would only do a test like this when everything is honky and dory. As such, the test wouldn't highlight the differences between the gases in a situation where the fit is hitting the shan.

I think another way to pose the question is, what are the benefits and the drawbacks of air vs. something like triox on a dive to 40m/133ft?

 

[MXGratefulDiver]

I'm not an expert ... I can only report on what I have experienced, and that is as follows ...

- In one of my tech classes (I forget which one, actually), my instructor invited me to try the nitrox-to-trimix experiment at about 110 feet. I was using EAN32 ... he was using 25/25. When he handed me his reg I did notice a slight difference, but not very significant. After about two minutes, I switched back from his reg to mine ... and I noticed a rather stark difference almost immediately. I'll leave it to the "experts" to speculate why.

- In numerous deeper dives using air or EAN28 (aka "slightrox") ... I've never noticed any significant difference in narcosis symptoms between the two.

- I've noticed two significant symptoms of CO2 retention ... a feeling of "I can't get enough air", and sometimes a moderate headache. During those times when those symptoms were noticeable, I've never felt like I was narc'ed ...

... Bob (Grateful Diver)

 

[dreamdive]

I think we are in danger of leaving the OP behind. CO2 retention is an important issue and another reason to use more helium. However, air doesn't have much CO2 in it - the CO2 is excreted by the body as a product of respiration. If the CO2 is exhaled then it is heading up the water column to the atmosphere. A small amount is re-inhaled as it is in the 2nd stage as the gas changes direction. The so called "dead space" of the regulator.

There's a big thread on it here: http://www.scubaboard.com/forums/basic-scuba-discussions/224684-co2-retention.html

Dear Chrisch,

you are missing my point. You are absolutely correct that air does not contain much CO2. However, as a byproduct of respiration and oxygen metabolism, we are producing CO2.

When you are working hard in the water (swimming or breathing) and at increasing depths, you will produce more CO2 because of increased gas density, scuba equipment, fitness level, etc, ..you may not be able to expire all the CO2 you produced. That is how people get CO2 hits. Also, some people may be less sensitive to rising levels of CO2 and "naturally" retain. I have a whole lecture on this and I cannot explain it all in this forum.

However, to state that CO2 is not narcotic is incorrect. Moreover, CO2 plus N2 is synergistically narcotic! Although the use of Helium in recreational depths is usually less warranted, it may play a role however with increased work-loads as it decreases gas density. For comparison: air has a density of 1.2 vs He of 0.16. Now obviously you would not be breathing pure He. But you can do your own calculations for a He mix and compare it to Air.

So He serves two rather than just one major purpose regarding "clear heads":
1. It decreases Nitrogen narcosis by decreasing nitrogen in the mix
2. It improves work of breathing thus reducing CO2 production

Your dead space in your regulator is a minor player for OC. However a malfunctioning mushroom valve in CCR is quite a different story. But that is a different discussion all together.

Regards,

 

[TSandM]

Yes, we have played with this, and had results similar to what's already been reported. You don't notice a huge difference going from Nitrox to 21/35, but you sure notice the fog coming in when you go back.

There are significant data indicating that some, if not many, scuba divers retain CO2 while diving, even if they are not making a specific effort to skip breathe. Elevated CO2 levels almost certainly contribute to narcosis -- CO2 is definitely a narcotic gas, as can be noted in ill patients who are unable to clear their CO2. The deeper you go, the denser the gas, and the less linear the flow through the small airways is. At what depth this actually begins to impede CO2 eliminated is not entirely clear, and the big effects are probably at significant deeper depths than 40 meters. But CO2 retention can be markedly worsened by ineffective breathing strategies (panting) or overexertion at depth, at which point the diver might note a marked narcotic effect (or his buddies might ).

 

[ubp_sanity]

I've seen a video. I had some friends who had a chamber ride, just for fun and experimentation. At about 180' you could see everyone was all giddy and definitely feeling the effects. They switched to breathing trimix (no idea what composition) and it seemed like almost instantly everyone sobered up after they had been breathing it.

 

[boulderjohn]

No I don't understand, any use of trimix, for what I have read the divers using trimix don't use air ( low % I think ), but my question was in case somebody had tried this or maybe as part of a tec class, just as to see the difference in state of mind or other.

I did this in a tech class. I was on 21/35, and my instructor was on air. We were at about 150 feet, IIRC. We switch for about 2 minutes. When we surfaced, he said he could tell a huge difference both ways. As for me, I could barely tell a difference. I guess it shows how different we all are in this regard.