Use a gag strap?

[doctormike]

From talking to my really deep diver buddy, he points out that he doesn't put a BO reg around his neck for several reasons. One, once you are carrying multiple cylinders, you need to switch to the correct one. Your bottom BO gas could possibly be hypoxic at a point you need to bail out shallower, for example, so just having one BO reg/gas for all situations is not an option. And, two, the training includes switching BO cylinders with your buddy once the person on BO breathes theirs down to half. Swapping doesn't work so well if the reg is around somebody's neck. The skill done in training is the same for all BO cylinders and does not include dealing with a BO reg hose that is around anyone's neck. And, as he says, "if you don't/can't drill on it, then you don't do it during a dive."

Dunno. I don't do any of that deep stuff. I have deep bailout on the left, which is what I would use in an immediate emergency (CO2 hit, torn hose, etc..), and that is on a bungee necklace so that it's that much quicker to deploy should I need to. Yeah, we are all incredibly skilled and practiced with superb training, but from what I understand, all that can quickly go out of the window with a significant CO2 hit. I carry O2 on the right, so in the event that I have to complete deco without going back on the loop, I can deploy that at 20 feet and not be limited by my deep bailout alone. That reg is bungeed, since it would never be an immediate emergency to switch to it, just a regular OC deco gas switch. So no way to bail out to the wrong gas.

His training - and mine - included drilling to be able to deploy the OC reg from where it is stashed on the BO bottle very quickly. I will say that his training does also include having a BOV (on his X - his JJ training did not include having a BOV).

In the words of Mike Tyson, "everyone has a plan until they get punched in the mouth".

I do realize everyone's training is not the same and I'm not trying to say any one way is better than any other way. I'm just trying to discuss the different approaches, to help ME understand them better.

Sure! I always enjoy reading your threads - you really think things through, and are willing to consider other viewpoints.

One thing that seems like it might be relevant is, if you're having a CO2 hit, you CAN stay on the loop for another second (or two or three) if you need to (I think), in order to switch to BO. And if your reason for switching to BO is something else, you probably aren't having the same mental or physical issues, such that pausing your breathing for a moment, if necessary, while you deploy and switch to a BO reg is a major problem. Which means, what I'm trying to say is that I'm not sure the time it takes to deploy a BO from a slung cylinder, versus switching to one on a bungee necklace is a "real" issue. Is it? I don't know. Maybe if you got really unlucky and just sucked a big mouthful of caustic, it could be a problem?

This is a hard thing to have an internet discussion about, since most people haven't really experienced the problem. I'm just going by the few first hand reports that I have read. And, as we say in medicine, "there is a bell curve for everything". So maybe sometimes you can detect a CO2 hit or hyperoxic VENTID symptoms early, and sometimes you can't.

This is sort of OT from gag straps, but all of this is really making me lean more and more towards wanting to have a BOV. I know some people say that they are not needed and you should always detect an oncoming CO2 hit well enough in advance to be able to switch to BO without needing a BOV. But, is there really a downside? I mean, if you ARE able to detect the CO2 building up, you don't have to use the BO, right? You could have it and still dive as if it's not there.

The DSV is simpler, lighter, less bulky and requires less maintenance.

 

[Dsix36]

This is sort of OT from gag straps, but all of this is really making me lean more and more towards wanting to have a BOV. I know some people say that they are not needed and you should always detect an oncoming CO2 hit well enough in advance to be able to switch to BO without needing a BOV. But, is there really a downside? I mean, if you ARE able to detect the CO2 building up, you don't have to use the BO, right? You could have it and still dive as if it's not there.

My reason for not having a BOV is simple and others will argue. I believe that a BOV should always be plumbed into a large volume of breathable gas, regardless of what depth you are at. This is going to require some sort of gas management like swapping hoses or a switch block and either of these (or lack of doing it) is an opportunity for me to end up with the wrong gas. Breathing the wrong gas is a relatively common trait among tech diver deaths.

Muscle memory will train you to use the BOV but if you get shallow and do it with a hypoxic dil it will be lights out. Conversely, if you forget to switch at depth or accidently bump the switch block and change it, you might end up hypoxic as hell in no time.

just my .02

 

[rjack321]

Yes. I emailed with DGX about whether any of their mouthpieces would fit the hole on a Drager DSV. They specifically suggested to NOT use their Seacure one. I have not been able to get confirmation that any of the moldable ones on the market are really big enough.

A buddy did recommend the JJ mouthpiece to me. He uses one on his X and said he has tried a number of different mouthpieces before settling on that one. I ordered one and will try it.

But, after reading the French study article and what some of the experienced people here on SB have posted, I am kind of thinking I might go back to using the stock mouthpiece with gag strap.

I use a Mares mouldable. Out of the box the hole was too small. I opened it up and because the plastic is much harder I had to glue it to my DSV to keep it from leaking around the zip tie. Aquaseal worked, it just peels off Delrin if I want to remove the mouthpiece.

 

[rjack321]

My reason for not having a BOV is simple and others will argue. I believe that a BOV should always be plumbed into a large volume of breathable gas, regardless of what depth you are at. This is going to require some sort of gas management like swapping hoses or a switch block and either of these (or lack of doing it) is an opportunity for me to end up with the wrong gas. Breathing the wrong gas is a relatively common trait among tech diver deaths.

Muscle memory will train you to use the BOV but if you get shallow and do it with a hypoxic dil it will be lights out. Conversely, if you forget to switch at depth or accidently bump the switch block and change it, you might end up hypoxic as hell in no time.

just my .02

How many of us are using really low fO2 BO on a regular basis? I use 15/55 fairly often, I don't have an issue connecting that to my BOV starting on the surface. You can breathe that on the surface (like a freight train) but you aren't going to actually pass out for quite some time. Plenty of time to close the BOV and breathe the atmosphere.

Vs 10/70 BO into my BOV makes me nervous.

 

[JohnnyC]

BOV w/a gag strap on both my rebreathers.

 

[Germie]

Never used and don't see a need to buy and attach one. And I prefer DSV's over a BOV (too heavy).
BO oc main reg is under my neck.

 

[cathal]

I am aware of a recent fatality on a CCR,(this year), on this side of the pond where the deceased was found at the bottom of the shot line immediately after jumping in, with loop out of his mouth and his mouth clenched closed. His buddies could not get the reg into his mouth due to it being clenched. A gag strap would have helped his chances of surviving as it would have mitigated against the triggering LOC event and subsequent ingress of water into the lungs.

 

[stuartv]

Never used and don't see a need to buy and attach one. And I prefer DSV's over a BOV (too heavy).
BO oc main reg is under my neck.

I thought the study of the French Army divers was somewhat compelling in favor of using a gag strap. Do you feel like a gag strap won't really help if you do pass out? Do you feel like passing out is not something that will happen to you, because you manage your dive and equipment in a such a way that it ensures it won't?

I never noticed how heavy my DSV is until I dived it without a gag strap.

I have just ordered the new rEvo BOV. I will use the stock mouthpiece with gag strap on that. I am curious to learn how heavy it feels in my mouth.

 

[doctormike]

I am aware of a recent fatality on a CCR,(this year), on this side of the pond where the deceased was found at the bottom of the shot line immediately after jumping in, with loop out of his mouth and his mouth clenched closed. His buddies could not get the reg into his mouth due to it being clenched. A gag strap would have helped his chances of surviving as it would have mitigated against the triggering LOC event and subsequent ingress of water into the lungs.

Agree. That's sad. Hyperoxic seizure? If so, another failure mode that might be addressed by a gag strap. Not just (hypoxic) LOC.

 

[doctormike]

I thought the study of the French Army divers was somewhat compelling in favor of using a gag strap. Do you feel like a gag strap won't really help if you do pass out? Do you feel like passing out is not something that will happen to you, because you manage your dive and equipment in a such a way that it ensures it won't?

I guess if you really want to do an analysis of this, you have to look at causes of mortality, and see exactly why the French military divers were developing LOC. Was it something that they are subject to that recreational divers might not be subject to?

The problem is that it's hard to get very granular data on this.

So the failure modes where a gagstrap could be definitely helpful would be hypoxic LOC and hyperoxic seizure. But those would both require a buddy who could fix the gas problem without taking you off the loop. Just keeping the loop in won't save you if the loop remains unbreathable. Any buddy could do a dil flush, I would be more concerned about expecting a non-CCR diver to check the PO2 and hit the MAV.

For hypercapnea events, the question remains if gagstrap+BOV is better than no gagstrap with DSV or BOV. I suspect that if you are using a BOV, then that tilts the advantage to gagstrap, since you never need to remove the loop, even in an emergency. But a gagstrap and a DSV might be a poor combination in that case.

And then you have to see if the statistical advantage of the gagstrap is big enough to outweigh the downsides of a BOV for people who wouldn't otherwise use them.

Hard math to do, since we don't really have the data. We have anecdotes on both sides of the question. Good thread, Stuart!