Incident on 80m (avg) - 30 min BT dive

[fsardone]

If you have the oxygen on the outside or the richest gas, and the leaner gas under, there is a risk that in a stresssituation you take the richest gas. That is a risk. The outside cylinder is the easiest to grab. This is important if you dive ccr. In a real emergency there is not time to do complete checks. A CO2 hit means asap go to a breathable gas.

Germie,
thanks for your contribution lots of points to ponder.
Only one thing: In a CO2 hit my first tought would be stop producing CO2 and increase ventilatory efficiency.

In my advanced training, my instructor managed to induce a CO2 hit in OC (I was at less than 10 mt). That really showed me that CO2 hits are most of the time induced by inefficient ventilation that is unable to remove the CO2 produced. This could also be due to overexertion.

This said, you go to OC (which reduces work of breathing and removes the risk of rebreathing CO2 due to scrubber or valve failures) but the important step is stop producing CO2 and deeply ventilate.

My point being most of the time switching to a breathable gas will not solve the issue, the ensuing ANXIETY (CO2 induced and situation induced: you do not see a resolution of the emergency) will make for shallower and faster breathing and worsen the capability to remove CO2.

Cheers

 

[Germie]

Not part of the incidentdiscussion, but part of the CO2 discussion. First, you cannot stop produce CO2. It is a product of your metabolism. Every breath out there is new CO2 breathed out. But to remove CO2 from your body you have to do that over your lungs.
Best ist to stay calm and breath deep in and out. BUT:
On a rebreather with a CO2 hit, YOU CAN'T. You breath the CO2 in and out again and produces more CO2. Your breaths are faster and faster and shallower and shallower. The only way is to go on OC. Then at least no CO2 is rebreathed anymore. There is a chance to get off the high CO2 in your body, to find rest again. No time to turn a valve on, no time to be checked by a buddy. A real CO2 hit can be lifethreatening. That is why you must have the bailoutgas easy to grab, AND the valve a little bit open so you can always breath. There are people who where impossible to get off the loop. The BOV/OCB had disadvantages too, but it can help to take some sanitybreaths. If a BOV is needed is another discussion and not needed here. But some CCR divers has their deepest gas with a bungee on their neck. Grabbing a stowed regulator from a bailoutcylinder can be too hard when you have a real CO2 hit. This is why on ccr every diver (in case of teambailout) needs to have at least one bottomgas. Decogases can be shared. At depth you don't want to have shared cylinders. YOU NEED fresh GAS, NOW, NO TIME TO WAIT. A CO2 hit get worser and worser every breath you take. So you need to get off the loop. And then hope and pray you can solve the CO2 hit and find rest again. After a CO2 hit back on loop is notdone.

 

[Nianne]

I don't know if anyone already asked the question, but did he told you before the dive that he was the less experienced diver and may need a little "babysitting" ?
I'm new to tec diving and I have absolutly no shame saying that I'm a baby tec diver (and a baby instructor as well) and that I know what I've learned but need some experience.

Maybe guys don't tend to act the same way ?

 

[beester]

SAC/RMV not important on this level? It is. Being does not mean you can stay 30 minutes at 80+m. I had a student who could do a reasonable dive at 55m, so certifying at normoxic level was possible, but he was not able to get his sac/rmv down. So at 80m, he would have to take a twin15 or 18 to do a normal bottomtime. But how will you handle the decogases? I have told this. I don't know if he really wants to go on the full trimix level, but even if you are capable for doing the dives as have enough skills/bouyancy/no stress/etc, if your sac/rmv is too high, that can be limiting too.
For me if I am a paying customer on a fundive, I don't mind the background of a diver, agency is not important, carrying cylinders left-right not important, doing rotations or not, not important, best mix or standardgases not important and we can discuss (all these things have nothing to do with a non skilled diver, there are really good bestmix left-right no rotation divers), but I want to know if I can do a reasonable bottomtime. So the question will be done about sac/rmv. And of course I want to know if there is extra gas on the boat or there are safetydivers.
Beester, as you wrote he used a lot of ean50 and 100%, I am really curious how much backgas was left. I have seen divers lying about their sac/rmv too. REALLY this happens. Lying about it during the dive about the pressure left in cylinders as they didn't want to be the one who could not do the maximum planned bottomtime. If you see a diver has left not a lot of decogases at the end of the dive, I would ask friendly about his backgas too.

Well of course SAC is very important. To be honest I didn't check his backgas manometer after the dive, but you are right this could have told us something. However his issues only started during ascend so maybe his SAC increased a lot while being taskloaded (this can happen if you aren't watching this when you are taskloaded).

But I'm not discussing SAC with a diver before a dive. I'll discuss MIN GAS (the minimum amount of gas to get a teammember and myself to the next switch) , we'll also calculate deco gas needed (including reserves for lost deco gas) based on the same standard SAC of 20l/min. Finally we'll discuss if based on a standard SAC of 20 l/min if we can make the dive and the planned bottom time.

This all based on a standard SAC of 20l/min. If a diver has a higher SAC in specific normal circumstances (not talking about a CO² hit, or any failure) then he should shout out and make the team aware. But most experienced divers will normally have a SAC of 20 l/min or less.

I'm assuming nothing was wrong on bottom gas consumption because we communicated 25' in and I asked if we could continue for the planned additional 5 until 30'. So I'm "sure" that he was not on min gas. And if he forgot to check his gas consumption regularly he would have known his status at 25' in because I asked and he signaled after checking all ok. For me deliberately going under MIN Gas is of course a big no no, because it's my/team reserve you are playing with. I'm not assuming this was the case.

 

[leadduck]

Heya Leadduck. You are totally right a quick fact check and talk before a dive is very warranted. Specially if you don't know eachother. That is sound advice.

You can't know this but what lured us in not doing this is GUE and it's very standardised way of diving. This means that it's possible to dive with people that you can barely communicate with on the surface (language barrier) but still do technical dives with. Because all procedures are the same, we "speak" the same language underwater. Gas plan is easy, deco is easy, switch depths are easy, deco gasses are easy, how to handle equipment... all that is standardised.

That being said... maybe because it's so standardised we did get lured into safety and didn't have the little talk (maybe with hand and feet if there was a language barrier... or involve the JJ divers who did speak diver X his language).

yes I think this is the core of the issue here, behind all the technical diving details. Nothing wrong about standardization but here it made you think skipping any pre-dive team dive planning is OK for an 80m dive; you thought X is T2 without asking (nobody including X actually said so, you assumed it). Of course X is responsible for his actions as far as he can understand the risks. But just imagine what if the dive went seriously wrong, and only then you learn that he had only 50 dives, OWD and Fundies rec pass, had just begun a trimix course (a misunderstanding by your JJ diver friend), was just too inexperienced and too shy to call the dive (language barrier), and now you have to explain to the jury why you took him to an 80m trust-me dive. You don't want that.

 

[beester]

I need to ask what is the point of tank rotation seems it was something that added to the incident. Tank rotation is not something I have come across given I and many of the people I dive with use the rich right lean left method, seems a lot less fafing around for a gas change. Even if you do insist on leashing off the oxygen why not bring down to the right side for the gas change.

I think (like Germie) that both systems have advantages and disadvantages. I mean clearly donating a long hose with a stage right is more difficult (let alone 2 stages). On the other hand stage position is also something that could catch out an unaware GUE diver. Depending on no of gasses, most GUE divers I know will put the 50% on the outside, bottom gas on the inside left, O² and any other gasses on the leash. This is in a sense also a righty-lefty situation if you are unaware, and although I'm fully aware that the position of a tank is irrelevant I'm most of the time setting up like this (for other reasons as well like having the lighter, bottom stage under the heavy 50% when I'm breathing it empty). Of course all of this is catched in any case by a team check before switching (which i don't see all federations/instructors teach).

You are right that the tank rotation was additional taskloading for diver X (I'm not sure if it was a cause). But to be honest on these kind of dives I would expect your buoyancy and platform to be good enough to be able to handle tank rotations.

Finally with righty richie leftie leany at a certain stage you need to start handling tanks in a different way in any case. During that week we also did 5 stage dives... not sure how you would handle 5 stages but I don't think you'd be able to attach them to your left and right D rings only. At a certain moment you'll need a leash (or a rebreather).

 

[beester]

I don't know if anyone already asked the question, but did he told you before the dive that he was the less experienced diver and may need a little "babysitting" ?
I'm new to tec diving and I have absolutly no shame saying that I'm a baby tec diver (and a baby instructor as well) and that I know what I've learned but need some experience.

Maybe guys don't tend to act the same way ?

Very good remark. I don't want to sound sexist. But this makes in my opinion most female divers better divers than men. Less EGO.

Nianne, don't underestimate peer pressure. Specially if there is a lot "invested" or there is the perception that a lot has been "invested" in an activity. Calling out that you are less experienced, that you are feeling uncomfortable or slightly stress requires you having a lot of trust in your fellow buddies. You trust them not to perceive you as weak when you call out. You trust them to understand you and understand why a dive might be cancelled.

Also underwater we expect our team to call the dive if something is a miss... but when is something a miss? When it's too late?

It's very funny that we do rely on our buddy / team in these kind of dives so there must be trust to be able to perform underwater, but at the same time many times people don't trust their team enough to speak up when they have an issue or feel they need a hand.

I've posted about this before and it's totally of topic but maybe not. To of my buddies had reserved 2 spots on a north sea wreck diving charter. There were no other divers on board they knew. One of the divers felt not totally well (didn't sleep well, etc) and didn't call out arriving at the dock because he felt that by doing so he forced the other diver to cancel as well. Things didn't get better on board, sea sickness, etc but he decided to dive because everybody said visibility on the wreck was great. Just before jumping in (quite a lot of wave action) he slipped and fell on his knee hurting it. His buddy was standing on the board secs before jumping in and shouted, do we jump or not... yeah yeah we'll jump. In the end they finished the dive and he had a slight type 1 hit. (dcs) Only then did he speak out... to his buddy that he hadn't felt well the whole day. If he didn't got hit he probably wouldn't have mentioned any of this but only because of this slight hit did he speak out. Peer pressure in action. Feeling they had invested a lot, not willing to make the call that would force his buddy to also not dive, thinking it would get better underwater... etc etc etc.

I rely on team, but in order for the team to function I expect everybody to speak out when something is not totally right, with him, with me, with the team, with the plan... we are eachothers backup brain and if you or I don't speak up then it becomes less safe.

To be honest that did break down during this incident on a 80m dive as well

 

[beester]

yes I think this is the core of the issue here, behind all the technical diving details. Nothing wrong about standardization but here it made you think skipping any pre-dive team dive planning is OK for an 80m dive; you thought X is T2 without asking (nobody including X actually said so, you assumed it). Of course X is responsible for his actions as far as he can understand the risks. But just imagine what if the dive went seriously wrong, and only then you learn that he had only 50 dives, OWD and Fundies rec pass, had just begun a trimixcourse (a misunderstanding by your JJ diver friend), was just too inexperienced and too shy to call the dive (language barrier), and now you have to explain to the jury why you took him to an 80m trust-me dive. You don't want that.

Maybe a bit over exaggerated because we did do a T1 (normoxic dive) with him beginning of the week. It was a light T1 dive but still he was at ease at that stage. I'm not sure if a OWD/fundies rec student with 50 dives would be able to do this.

But you are right we were eased into not asking the right questions besides the diveplan, because we assumed him being on same level with experience. (maybe he was and just had a bad day).

But to be honest if that is the case (him being way out of his league) it's also his responsibility to speak up and address this at least to the JJ divers that he knew. Then we could evaluate adjusting the dive or doing another dive. I mean we were not so focused on the dive to do whatever. I mean we planned initially for a different dive (a seaplane at 90m) but that was blown out and not diveable that day so we were flexible.

Finally the big risk was of course him hurting himself or us as well (with trying to help him), the big risk wasn't liability. I'm an instructor but he wasn't my student, nor was I doing a course. In this case he was our responsibility underwater like in any team, but I don't think anything would stick in a court of law.

 

[Nianne]

I know nothing about GUE, but maybe he didn't had the necessary training for thoses dives (and knew only a little about GUE like me). Even if he was from another agency and thought he had the same level.

TDI Equivalent Ratings with Other Scuba Diving Agencies | SDI | TDI | ERDI
I'm TDI deco procedures and apparently it's the equivalent of tec 1, but I actually have absolutly no idea how to do a normoxic dive !

 

[RainPilot]

I know nothing about GUE, but maybe he didn't had the necessary training for thoses dives (and knew only a little about GUE like me). Even if he was from another agency and thought he had the same level.

TDI Equivalent Ratings with Other Scuba Diving Agencies | SDI | TDI | ERDI
I'm TDI deco procedures and apparently it's the equivalent of tec 1, but I actually have absolutly no idea how to do a normoxic dive !

Charts like that are sort of ok for choosing a course progression but completely useless for gauging a persons qualification.

With GUE the course path is not directly comparable with an RSTC type agency.

However, almost nobody will brief by course. We don't say "hey we are doing a Tec 45 dive today" we say "Bottom time x, max depth Y, gases Z" which should set off alarm bells if you aren't certified for any of those factors.