Virginian diver dead at 190 feet - Roaring River State Park, Missouri

[PullYourselfTogetherMan]

I've read this thread start to finish. I'm still a rec diver but have taken intro to tech (and was told to dive more doubles) and even with my extremely limited understanding of tech diving, at some point the conversation of "hey, what gas are you using and what's your p02" should have been had. My instructor was teaching ITT with a heavy influence of GUE so maybe that's not normal but to me it's incredible that you have an expedition team that somehow failed to see that one of its divers was using a gas woefully inadequate for the job.

Hell, even in rec diving you're meant to ask your dive buddy what they're diving so you have somewhat similar NDL and MOD.

Honestly that expedition team leader should be ashamed of themselves for running such a dive operation.

^ This. I've seen other things about this expedition and team that were just... off. I don't want to say much more.

 

[Nitrogenius]

Increased WOB = more CO2 retention = more narcoses. Its not a set value, but any experianced RB diver would take it into consideration.

Oxygen is has been widely proven to have the same narcotic effects as nitrogen. Diving a nitrox mix does not reduce narcosis in any way.

By no means did I question the relevance of WOB and CO2 congestion. It was simply not the argument I made!
WOB is very relevant just to avoid misunderstandings. I personally know that very well as I am very prone to CO2 retention myself!

As for Oxygen having the same narcotic effect as Nitrogen being widely proven, I beg to differ. \
This is a widely made claim for sure, but one with simply no proof at all.
Thinking it through logically one comes to the conclusion very fast that specifically the "same narcotic effect" can't quite be true.
If it was true that within the mix of air it would have the "same narcotic effect as Nitrogen" this would mean at a ratio of 21/79 the O2 molecule should roughly be 3.8 times more narcotic as N2, which in consequence would mean that in another Nitrox mix the narcotic ponetial would shift.
All body function in diving relate to partial pressure, but all of the sudden this should not apply to xygen by some miracle it constantly is adjusting its narcocity by the given ration in a given Nitrox mix?
Gimme a break.. It is a simplification that has been made in ordere to prevent folks from trying to use Nitrox to somehow prevent and reduce Nitrogen narcosis instead of using the proper Trimix in my opinion.
The only still ongong discussion with the relevant peers is, whether oxygen might or might not have some narcotic effect or not, but it surely is not really relevant to diving practises.
Also keep in mind that oxygen is not an inert gas. Another reason that speaks against the simplification "as narcotic as Nitrogen"

thats not quite accurate - At the transition point there is a range where the ccr PN2 is higher and then OC PN2 catches up - that transition point (depth) will vary depending on the CCR set point

eg 6 ata air is Po2 1.26 and Pn2 of 4.74 and on ccr set point of 1.2 the ppo2 is 1.2 (lower) and the Pn2 is 4.8 (higher) the range that this is applicable is approx 5m

And what exactly is not quite accurate? Nothing what you state here contradicts the quote you are refering to in my opinion. Yes I absolutely agree, as a matter of fact, that the transition point does vary depending on the setpoint. As reasonable setpoints for the "working portion" of a dive range between 1.0 to 1.3 (I personally use 1.0 for various reasons at depth and then 1.4 on deco and flush pure oxy at 6m onwards), it is safe to assume that the PN2 in the loop will have been higher than on air at the depth reported.

Not sure how you derive the applicability range, though the deeper you go at a given setpoint without He in the loop the higher your N2 percentage gets and thus the higher your PN2 and the higher the discrepancy to air PN2.. There is no limit.. Just that the usability to actually dilute your loop gets less and less with depth until the point that you won't be able to dilute at all (which with reasonable setpoints happens even before you reach the transition point depth

While I still calculate END assuming that is true, I seem to recall @Dr Simon Mitchell hinted that may not be so cut & dry a month or two (?) ago. I saw this yesterday about a recent study:
Is Oxygen Narcosis A Thing?

exactly.. there is just not much discussion as with good diving practises (considering Helium also for WOB aspects) any potential narcotic potential of O2 is completly irrelevant

 

[Nitrogenius]

Ether way, its a moot point on this dive. There were stage bottles every 50(?) ft at RR.

There is plenty of indication that for the deceased diver there was no plan to actually tap in those gas reserves and it is questionable if he was even trained to tap into staged reserves, so I do think this is not moot at all..

Agreed, while I don't agree with the team's choices of tanks and contents, it wasn't a factor in the death as the general understanding from the team members that have spoken up that he should've had trimix for this dive.

beaing exactly the point. This is one of the indicative factors that the deceased divers had no means to make use of such stage tanks as otherwise he would have used them for the more approriate gas.

I am mildly familiar with gas planning. Double 50s at 140cf are adequate bailout for me on a 200' dive with a straight exit. I am not familiar with the cave they were diving and I don't know the exit path. The difference between those at 140 cf and double 80s at 154 is marginal in my opinion. If I am planning bailout and 14 cf is the difference between planned and required, I change my plan.

140 cft over two tanks at 200' sufficent with straight exit? No matter the decompression ceiling? Are you accounting for elevated amv induced by a CO2 event at all?
After I endured a CO2 hit (which in hindsight was still a very mild one) at a mere 30m I had a spike to 70 l/min amv for 3 minutes ! After stablising at app. 15 m and after those 3 min I still was up to 35 for another good 10 min and then likely only came back to my normal resting amv being about 15 l/min..

So at 200' --> 7 bar in my mild event the first cave filled 50 would have been empty after about 4 min at depth.. leaving you with the remaining 70 cft for a safe ascent with yet a still elevated breathing rate if that second gas is even safe to breath at depth..
Doable ? surely... but not as a general "is adequate statement" coming from a tech instructor in my opinion. No offense meant here, but to be considered as some folks might get the wrong message there.
Ever since that event I count the first deep BO as empty in my plan and like to have it as big as reasonable considered the circumstances of the rest of my dive. It was quite an eye opener..

 

[Tracy]

140 cft over two tanks at 200' sufficent with straight exit? No matter the decompression ceiling? Are you accounting for elevated amv induced by a CO2 event at all?

It is a cave, his deco bailout would be staged, 140 cf should be able to get him from 100' to 20' with a straight exit.
Depending on reaction time, yes, it should cover increased gas usage for a CO2 hit. You are talking about an 80' ascent. Carrying enough gas for a co2 hit would plan you out of the water. That is why they were staging bottles, you can't carry the capacity for that plan.

 

[tursiops]

Assuming O2 is as narcotic as N2 is meant to be a conservative, safe assumption, not a statement of scientific fact.

We've learned more. This article argues O2 has effectively NO narcotic potential.....

Is Oxygen Narcosis A Thing?

There’s been a long running debate as to whether oxygen is a narcotic diving gas. Training agencies CMAS, GUE, PADI and PSAI include O2 in their equivalent narcotic depth (END) calculations. Others like BSAC, IANTD, NAUI and TDI do not. The problem has been reliably measuring gas narcosis. Enter...

gue.com

 

[Nitrogenius]

It is a cave, his deco bailout would be staged, 140 cf should be able to get him from 100' to 20' with a straight exit.
Depending on reaction time, yes, it should cover increased gas usage for a CO2 hit. You are talking about an 80' ascent. Carrying enough gas for a co2 hit would plan you out of the water. That is why they were staging bottles, you can't carry the capacity for that plan.

There is no indication that "his" deco bailout was staged, the report very much reads that all the stages were put in place for the push divers.
We are definitely not on the same page on planning for CO2 hit, fingers crossed it will never happen to you..
I always account for it and executing cave dives up to 380' I have yet never managed to "plan me out of the water" also when carrying all bailout within the team. Obvioulsy one would not account for multiple CO2 hits.
Yet 200' depth cave or no cave with a reasonable gas distribution and two 50cfts I consider somewhat alpinist depending on the decompression obligation. In my world there I do not believe on a NDL dive to 200' even on a bounce dive ..

 

[Whitrzac]

There is no indication that "his" deco bailout was staged, the report very much reads that all the stages were put in place for the push divers.
We are definitely not on the same page on planning for CO2 hit, fingers crossed it will never happen to you..
I always account for it and executing cave dives up to 380' I have yet never managed to "plan me out of the water" also when carrying all bailout within the team. Obvioulsy one would not account for multiple CO2 hits.
Yet 200' depth cave or no cave with a reasonable gas distribution and two 50cfts I consider somewhat alpinist depending on the decompression obligation. In my world there I do not believe on a NDL dive to 200' even on a bounce dive ..

Lets simplify this for you.

The stage tanks were bailouts for whoever was in the water.

 

[Tracy]

There is no indication that "his" deco bailout was staged, the report very much reads that all the stages were put in place for the push divers.
We are definitely not on the same page on planning for CO2 hit, fingers crossed it will never happen to you..
I always account for it and executing cave dives up to 380' I have yet never managed to "plan me out of the water" also when carrying all bailout within the team. Obvioulsy one would not account for multiple CO2 hits.
Yet 200' depth cave or no cave with a reasonable gas distribution and two 50cfts I consider somewhat alpinist depending on the decompression obligation. In my world there I do not believe on a NDL dive to 200' even on a bounce dive ..

In your post above calling me out, you stated that in your experience, you are consuming 10 cf per minute after a co2 hit. You then post that you are doing cave dives at 380 feet deep. In that same post you say you always consider a co2 hit and plan your bailout gas accordingly.
What is your exit time on said 380' dive? Just on a normal north Florida 100' cave dive, I will frequently have an exit time around 60 minutes. I should be carrying 8 AL80s of bailout on that dive? Does that seem like something that is possible to do?
Like I said, I err to conservatism, but taking a full co2 hit into bailout planning will plan you completely out of the water.
They had staged tanks in the water. The diver did not use them. I would guess that stemmed from his state of mind caused by a poor dil choice, but I nor anybody else will ever know exactly why.

 

[RandallP]

There was enough bail out in the cave to safely exit 3 divers with complete re-breather failures (including CO2 hits). 14+ tanks above 225', the linear penetration to the restriction is around 300' Plus there were fully stocked habitats at 40' and 20'. On non push days this was available to anyone who needed it.

 

[PirateFoxy]

Lets simplify this for you.

The stage tanks were bailouts for whoever was in the water.

Dumb question time since I'm not a diver and definitely not a cave diver with exploration experience - would staged tanks for bailout have regulators on them already or would that have to be set up when you needed to use it? (For emergency purposes having it entirely ready to go seems most useful, but if you have a lot of tanks then that's going to be a lot of $ and a lot of hardware to maintain, so I can see both ways.)