Training for "Recreational Trimix"?

[DA Aquamaster]

My usual team mate starts getting noticeably passive and unfocused much past an END 110'. What's worse is that she's also very content at that depth and that's a problematic combination. Consequently, we start adding helium on deeper cave dives to keep the END at or below 110' and we add more helium on even deeper dives to maintain the same shallow END.

I've never had issues functioning and focusing on specific tasks at 130' and always seemed to get through the dive plan at that END, but I do notice very marked perceptual narrowing, and that has a definite impact on SA. It was interesting going back to the same depths and caves on trimix and being stunned by how much I'd missed on previous dives and noting areas not immediately around the line that I never knew existed. It's an eye opener, literally and figuratively and something that makes you not want to return absent some He in the mix.

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Higher flow caves, demanding swims and CO2 retention also seem to play a factor in narcosis and it makes sense given the narcotic effect of CO2 and likelihood of greater impact with higher CO2 levels. We factor that into the dive plan as well and take into account whether it's a scooter dive or a swim dive, Generally speaking I take pains to keep the respiration rate up as needed to properly ventilate and gladly accept the impact on SAC rate to reduce the CO2 levels. If it's a high flow cave we either bring a scooter, or bring more gas, or plan the dive to be out of the flow as much as possible.

 

[kathydee]

70 - 75 is my depth limit on Nitrox in caves now. I can't feel the impairment, but I'm sure it's there.

.

Lynne, I agree with you. 70-75 is also my depth limit in caves on Nitrox.

I can feel a noticeable impairment past this depth, that I do not want in an overhead environment.

 

[NAM001]

Yes it does, When i took the iantd course ART. I left with teh opinion that the recreational part of the name was there because of the o2 content being >20% and hence the only recreational part of it was that you could breath it all the way to the surface. Other thatn that there is nothing that is recreational about the trimix world.

rjack,


c. The upshot (my long-held suspicion) is, *recreational* tri-mix diving is inconsistent with being able to effect an immediate, expeditious, direct ascent to the surface from recreational diving depths. That is, *recreational* tri-mix diving is inconsistent with recreational diving.


Does any of this make sense?

rx7diver

 

[Scott L]

Double AL80's. With He, they aren't too much heavier than a HP130 with nitrox....

 

[rx7diver]

I believe you are about right... which is why some agencies will ONLY sanction helium use in conjunction with "training" that avoids the need for an immediate expeditious, direct ascent.

... Which brings us back to the OP:

We don't expect to move to doubles ... Is the whole thing a bad idea, or could this improve our safety and enjoyment on these deeper dives?

I decided quite a while ago that any tri-mix diving I personally undertake, I will treat as *technical* diving, no matter the particular mix, or how shallow the dive or benign the environment, or whether or not modest or extensive planned deco is involved. I will use at the very least the minimal complement of tech gear (which, for me, includes isolator-manifolded or independent doubles and at least one deco cylinder) and approach planning and logistics, including contingencies, as deliberately as I would for any tech dive.

But, I'm personally extremely cautious (risk-averse?) when it comes to this type of thing ...

Safe Diving,

rx7diver

 

[guyharrisonphoto]

Everyone, the discussion has been great! I will offer the following:

1. I will look into some of the courses that have been mentioned (UTD, IANTD, PASI) and see their requirements.

2. I did some more research and yes it looks like a 40cf pony is best.

3. Even recreational dives with short bottom times can be worth it on some of our spots

4. Physically, doubles are not an issue for me, but are a no-go for my spouse, who will not be able to handle the weight of doubles + pony on a boat. Also, doubles add another layer of training to learn how to manage, plus cost is a factor as you can't rent them, you need to buy two first stages and reconfigure your entire gear, running around $1K price of entry, per person. I would rather not start with such expense and inconvenience for what will be a relatively low percentage of our dives. Would rather invest in the basic "rec" training and then see where it leads.

5. I see the issue with emergency situations and a CESA not being an option, but I never thought of CESA as a "real" option for anything deeper than 60'. From what I see in many of the posts, trimix should make us better able to manage a problem because we will be thinking more clearly.

6. The dives I am talking about are done regularly by divers in large singles using nitrox and as recreational no-deco dives. We have done one of these, to 130, once, including a slow ascent and drifting safety stop, but I know it is pushing the limit although that particular dive went fine with no obvious narcosis or any other issues. I just want to increase the safety and enjoyment factor within these limits.

 

[danvolker]

Everyone, the discussion has been great! I will offer the following:

1. I will look into some of the courses that have been mentioned (UTD, IANTD, PASI) and see their requirements.

2. I did some more research and yes it looks like a 40cf pony is best.

3. Even recreational dives with short bottom times can be worth it on some of our spots

4. Physically, doubles are not an issue for me, but are a no-go for my spouse, who will not be able to handle the weight of doubles + pony on a boat. Also, doubles add another layer of training to learn how to manage, plus cost is a factor as you can't rent them, you need to buy two first stages and reconfigure your entire gear, running around $1K price of entry, per person. I would rather not start with such expense and inconvenience for what will be a relatively low percentage of our dives. Would rather invest in the basic "rec" training and then see where it leads.

5. I see the issue with emergency situations and a CESA not being an option, but I never thought of CESA as a "real" option for anything deeper than 60'. From what I see in many of the posts, trimix should make us better able to manage a problem because we will be thinking more clearly.

6. The dives I am talking about are done regularly by divers in large singles using nitrox and as recreational no-deco dives. We have done one of these, to 130, once, including a slow ascent and drifting safety stop, but I know it is pushing the limit although that particular dive went fine with no obvious narcosis or any other issues. I just want to increase the safety and enjoyment factor within these limits.

I have been on dives with Guy and his wife, and neither is any more likely to "bolt for the surface" and do "Blow and Go" than many of the tech instructors in S Fla. It does not take tech traning to have an advanced diver able to know and act as the only option avaiable is to hold stops as planned, and to maintain perfect buddy proximity and support.

Personally, If Guy and his wife are going to do the hole in the wall...a 140 foot dive, I would rather see them do it with 21-30 in their tanks, than to see them do this with air. This is a choice available, as many of you should know the local spearfishing population gets it's own gas from private( non-dive shop sources constantly...ie., the mix is easy enough to get without a dive shop being involved.). Guy should learn how to analyze, but he is a smart guy, and does not need a teacher to explain something as simple as analyzing.

I would prefer he takes the Trimix course, at least for himself, but if he does not, I would rather see him in the recreational trimix mode, than the deep air mode. Dives like the Hole in the Wall or the HydroAtlantic, will continue to be done, on air, regardless of the whining of tech instructors and shops, or by me. Knowing this, knowing what the ACTUAL choices really are, the bigger evil here for a solid advanced recreational diver, is deep air.

 

[guyharrisonphoto]

Dan, thanks for the kind words. I will contact you to discuss courses and instructors that you might know. We missed you at the GUE demo day but I heard you are working on an interesting project. We might be at the bridge this weekend (the opposite of a trimix dive ) unless this windy spell kills the vis, otherwise will not be diving until the end of the month.

I think this will make a difference in my willingness to go back to the hole in the wall. The one dive we made there was challenging, with a very strong current causing all the divers to have to hold on to or seek out crevases in the reef not to get blown off the site. Although no "overt" narcosis, I felt a little slow and it was clear to me that I could not work my camera controls and also manage the dive and be an effective buddy for Maribi on her most advanced dive at that time, so I left the camera clipped off (too bad as there were lots of goliaths). Although the dive went fine we both recognized it was a risky dive and having any safety edge would be welcome. She has a lot more experience now and, like you, I am confident in her ability to manage a slow ascent and hold any stops necessary.

From what people told me, the trimix makes a very big difference in your awareness and ability to function at a high level which would add greatly to the safety factor and might even allow for a few photos as well, but we will see.

Say hi to Sandra and pm me if you are going to be at the bridge over the weekend (not your favorite time, or mine, but that's what work allows this weel . . )

 

[ianr33]

Good Thread.

2. I did some more research and yes it looks like a 40cf pony is best.

3. Even recreational dives with short bottom times can be worth it on some of our spots

Next question:

What are you going to put in the pony?

1) Air? Cheap,simple, but you might get a narcosis "hit" swapping to it in an emergency at 130 feet.
2)Bottom Mix ? More expense and hassle but same END
3)28% Nitrox.? Same narcosis issue as air (I don't care what anybody says!! ) Best from a deco perspective (but if it was ever used in anger you should be heading straight for the surface anyway so shouldn't be an issue)

I would at least consider the implications of being on ,say,28/20 at 130 feet ,brushing up against NDL, and having to switch to air in an emergency.

 

[danvolker]

Good Thread.



Next question:

What are you going to put in the pony?

1) Air? Cheap,simple, but you might get a narcosis "hit" swapping to it in an emergency at 130 feet.
2)Bottom Mix ? More expense and hassle but same END
3)28% Nitrox.? Same narcosis issue as air (I don't care what anybody says!! ) Best from a deco perspective (but if it was ever used in anger you should be heading straight for the surface anyway so shouldn't be an issue)

I would at least consider the implications of being on ,say,28/20 at 130 feet ,brushing up against NDL, and having to switch to air in an emergency.

Of course, this is far outside of agency guidelines....but it does represent real world choices we know advanced divers make all the time, in spite of agency guidelines...with that disclaimer, I would say that a buddy pair as squared away as Guy and Maribi, would have each other instantly as a redundant source of gas should a failure occur at 140 feet deep. If this happened, one would pass the long hose to the other ( they are both geared DIR style by-the-way) , and they would immediately begin their ascent..using light to signal others in the group they are ascending..... The "only" use I can see for the pony bottle, is to have 100% O2 in it, that they could use at 20 feet to create a better gradient to offgas with, and to represent additional volume of gas for the final 10 minutes of deco they may want to do.

This is a real "buddy team", so planning for separation at 140 feet deep is not of any value. If one lost gas at 140, the other would have plenty of gas to get them up safely to 20 feet, where they would have an O2 stop. They would need to plan their max duration of dive at this depth, based on the amount of gas the two would go through on ascent with stops, to 20 feet.