Oxygen poisoning seizure > how to react ?

[beester]

Hi Ginti, yes OT, but no worries.

The big difference is that these are totally different environments:

CAVE: stable environment with relative small number of variables. No time issues (you can start the dive whenever you are ready). Logistics are easier in the water (you can predeploy stages on a previous dive, the number of stages during the dive is constantly diminishing because you drop them), setup pre dive is easy. Relative less equipment stress.
WRECK/SEA: Unstable environment, with a lot of variables (weather, current, waves, shipping traffic, etc), big time issues (specially if tidal currents are involved, but even in general the charter captain will tell you "in 20 min you need to be in the water"), meaning no time to fav about. Setup pre dive is harder, you need to clip everything on on a moving boat under time restraints. Equipment stress is a real thing, you are taking all the stages with you, standing up, moving to the exit, getting in the water, swimming/scootering to the buoy line, dropping in, bubble check in the current, etc... all is done with all your stages attached. 1 stage less makes a difference, specially in the split between 2 vs 3 stages (but also 4 vs 5 stages).

Next we have gas and gas logistics: In a cave that D7/D8,5L bailout is very irrelevant, it's not really going to save your ass, you should have ample bailout gas in stages available, and in emergency even have the bailout stages from your teammembers that are dropped at the same spot as your stages. Also tank management (rotation) is much easier in a cave (well let's say non Florida caves ;-) ). On wrecks it's the oposite. You don't need so much bailout gas to go up to your first deco gas, and taking 2 bailout stages (50% and O2) vs taking 3 (bailout bottom gas + 50% + O2) means you'll handle a stage rotation in the blue while ascending (which in itself is not a biggy if you are experienced and practice this from time to time, but it adds complication).

Finally we have form factor: The standard setup is a much smaller (less wide and also less high) unit than the GUE setup. Yes on wrecks this can also be an issue (mine has seen quite some rust) but less than in a cave.

In a cave GUE setup also works, but I believe the standard 3L setup is a better system. The only real benefit with the GUE setup is that you keep team procedures very clear (everybody is trained in the same way). In open water on wrecks I like the GUE setup a lot. Doing a 60m 45 min bottom time dive is easy peasy with just 2 stages, the fact that it's a bit heavier (well a lot if you don't count the additional stage) and wider is less relevant for me (but could be for a small guy/girl). Pumping the backgas to 280bar you could even do a 90m dive with 2 stages although I probably will take a 3rd at that level.

Mind you I'm a C2/T2 diver with quite some experience in OC, but my rebreather experience is limited to 100h+ on the machine and T1+ (50,60m) dives, so take the above with a grain of salt... I'm just a noob learning as well ;-)

 

[kensuf]

A bit OT, sorry for that...

Why do you like it for sea diving and not for cave diving?

I know I ask this question quite often, but I am still in the process of learning all the differences between these two environments that are important when diving rebreathers... You can answer in PM if you do not want to derail the thread too much

He answered a lot of it, but I want to emphasize a few key points.

The "GUE CCR Configuration" is for all intents and purposes, a set of OC double LP50s (or even AL40s) with a rebreather sandwiched in the middle. Right/left posts are basically identical, with the addition of an extra isolator in the config. It's nice and compact and well suited for dives where getting you and your stuff in the water quickly in a dynamic environment is important - think anytime you're jumping off a boat, especially hot drops in a high current.

The con with the system is gas volume. LP50s pumped up only have about 140 cubic feet (3200L) of bailout gas. In an ow or wreck environment, that should be more than sufficient gas volume to get you to your first deco gas, but it may not be enough to get you 1000m out of a cave that's 100' (30m) deep.

Generally speaking, cave diving is a static environment. You can literally spend hours standing waist deep in the water donning bailout cylinders without missing your target if you choose to do so. In this environment, more bailout gas may be necessary and so other options, such as SM bailout with bigger bottles, may make sense. IMHO, on some really long range cave dives, on-board DIL doesn't always work due to sawtooth profiles; one of our local caves continually bounces between 30' (10m) and 100' (30m) for the first 1500' (450m), so many of us use that left 3L bottle simply for drysuit and wing inflation and one of the SM bottles to drive our DIL.

 

[ginti]

Thank you, @kensuf and @beester; your inputs extended a bit my view

 

[doctormike]

In a full rebreather team, the it is very unlikely that you need to donate because this would mean:
- Compromised rebreather (go of the loop)
- Backup reg bungeed not functioning
- Long hose clipped of to right D ring not functioning

So by the time a donation is needed you probably have already notified the team that something is off, and they can prepare accordingly, (which is the same as donating a bailout tank, there is no need of urgency, because the rebreather diver will first go to his own bailout).

In mixed teams (OC + rebreather) it's a different thing because your bailout gas (on the back in GUE setup) is now also the backup gas of your OC buddy. In these scenarios I will elect (and will tell my OC buddy) that I'll put the longhose over the loop and clip it off. Yes it's still clipped off and in OOG scenarios I need to be fast to unclip but the longhose is already ready to be deployed without me having to come of the loop. Worst case scenario (if I'm slow unclipping) the out of gas OC diver can grab the reg still clipped (drinking from my tit as I call it jokingly).

On donating bailout. The basic premises is that every diver in the team carries all his bailout (no team bailout). I know GUE guys who will do some team bailout on very deep dives (not bottom bailout but for example intermediate deco gasses like an 18/45 (72m) or 21/35 (57m) deco gas being split between the team, one carrying the 18/45 the other the 21/35, because in theory you should be able to do most of the intermediate deco on 1 of these gasses, so if push comes to shove and can't donate you are not in trouble).... but this is getting far from standard practise.

I have to say i'm happy with the setup in open water wreck diving... not so much in cave diving. A good GUE friend of mine elected to revert his JJ back to standard 3L setup using off board bailout and cliping a longhose from this off board bailout to his D, ring... and I can his point of view, specially when it comes to cave diving.

Anyway getting too much off topic I guess.

Right. Long hose donation for me is also usually a mixed team issue. In that case, I may have a long hose on my deep bailout, bungeed onto the tank, with my own reg on a necklace (I don't have BOV).

I guess I just didn't understand the idea of having your rescue plan involve going off the loop. It either is something you need to plan for or it isn't. But the very fact that the configuration involves a long hose OC regulator at all implies that there is a need for it, because of there really wasn't a need for it, it would be better not to involve the risks of having it (LP hose blowout, reg free flow). And I don't like the idea of a flowstop on a reg that's going to be given to a panicked diver.

So going back to my original point, if you need it, it's better to have it easily available and not trapped. If you don't need it, why do you have it? But I agree, this is a bit off topic.

But I do appreciate all the time that you guys are taking to go over this GUE stuff... it's interesting!

 

[beester]

Right. Long hose donation for me is also usually a mixed team issue. In that case, I may have a long hose on my deep bailout, bungeed onto the tank, with my own reg on a necklace (I don't have BOV).

I guess I just didn't understand the idea of having your rescue plan involve going off the loop. It either is something you need to plan for or it isn't. But the very fact that the configuration involves a long hose OC regulator at all implies that there is a need for it, because of there really wasn't a need for it, it would be better not to involve the risks of having it (LP hose blowout, reg free flow). And I don't like the idea of a flowstop on a reg that's going to be given to a panicked diver.

So going back to my original point, if you need it, it's better to have it easily available and not trapped. If you don't need it, why do you have it? But I agree, this is a bit off topic.

But I do appreciate all the time that you guys are taking to go over this GUE stuff... it's interesting!

Well I agree with you, it's not the best system, but it's a good compromise. Like with a lot of GUE stuff, it's not the best solution for a specific problem (and if you hear/see a GUE diver saying otherwise he hasn't been around the block enough), but it's a compromise that works in a number of varied situations.

Same like standard gasses (which by the way most technical agencies now have adopted ), it's not the ideal situation for a specific dive, but it works more or less well in a wide range of dives.

Same with the JJ setup. If experienced rebreather divers try to break it down to it's components they will find things to fault for sure. The point is that the system works in a wide range of situations reasonably well and doesn't have any real big no no's (like the UTD sidemount system had for example), but what makes it very good is the training and procedures, not the system, like with everything in GUE. It's the fact that I can dive in a GUE rebreather team or a mixed oc rebreather team with people I've never dived with, and the amount of discussion will be minimal. Everybody will know how it works... Even the OC guys because it's basically a small OC doubleset with a rebreather sandwhiched in between. You don't have to explain a lot. Out of gas works the same (more or less, with the longhose over the loop), deco will be the same (slight variantions but we are talking minutes here in a typical T1 dive between OC and CCR), planning will be the same, the only thing as a rebreather diver I have to add is (not in detail) go over some of my possible failures (probably not more than, if I say stop I'm analysing something and there are no urgent issues except a bright blinking red HUD and CO2).

Anyway one of my best tech buddies (T2/C2/RB80/JJ... loads of experience) dives his JJ in a standard 3L setup... no issue for me because I know what the changes are, but in a mixed team it requires more explanation, process thought.

So there goes!

 

[Jack Hammer]

Like stated, when diving on the GUE JJ in a CCR team the long hose stays under the loop. Deploying it is quite quick & simple and was practiced ad nauseam in GUEs CCR1 course. It really isn't that big of a deal to do.

With OC divers in the team the long hose stays on top of the loop. Again, deployment is quick and simple. In warm water I don't notice it there at all. In frigid water with thick undergarments I can feel it on top of the loop and am aware of it throughout the dive but not to the point of it "ruining" the dive.

 

[doctormike]

Like stated, when diving on the GUE JJ in a CCR team the long hose stays under the loop. Deploying it is quite quick & simple and was practiced ad nauseam in GUEs CCR1 course. It really isn't that big of a deal to do.

With OC divers in the team the long hose stays on top of the loop. Again, deployment is quick and simple. In warm water I don't notice it there at all. In frigid water with thick undergarments I can feel it on top of the loop and am aware of it throughout the dive but not to the point of it "ruining" the dive.

That makes more sense.