Use a gag strap?

Do you use a gag strap on your CCR?

  • Always

    Votes: 26 31.3%
  • Never

    Votes: 42 50.6%
  • Sometimes

    Votes: 6 7.2%
  • Used to, but don't anymore

    Votes: 3 3.6%
  • Carrots/Other/Meh

    Votes: 6 7.2%

  • Total voters
    83

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This could totally be my newbness showing, so please help me understand where I'm going wrong in these thoughts.

The 3 main things we worry about on CCR are hypoxia, hyperoxia, and hypercapnia. Right?

In all 3 cases, the normal result, if unmitigated, is the diver loses consciousness, then loses the loop from their mouth, then drowns. In the case of hypoxia, even if they don't lose the loop, if the diver is breathing something hypoxic enough, I guess they will eventually die anyway. And if they are hypercapnic, again I suppose that even if they don't lose the loop, they will eventually die, right?

But, am I correct in thinking that, in all cases, if the diver loses consciousness and the loop stays in their mouth and at least somewhat sealed against flooding, their chance of survival is substantially increased?

I feel pretty safe in saying that if you go hyperoxic, have a CNS OxTox hit, and eventually pass out, as long as the loop stays in and doesn't flood, you will survive (pending no other complications, of course, like dropping to the bottom of the Marianna Trench while unconscious).

If you pass out from hypoxia, I am thinking that continuing to breathe a hypoxic mix will still keep you alive for longer than if you inhale water. If you lose depth, your hypoxic mix might even become breathable again and possibly you will revive on your own? Do you stop breathing quickly after losing consciousness from hypoxia? I think you do not, but I don't know for sure.

The big question mark in my mind is hypercapnia. I suspect that if you go hypercapnic to the point of LOC, the only way you are going to even have a chance of coming back from that is if you get much shallower (maybe) or to the surface and have a chance to start breathing surface air. Or if you have a BOV and someone switches it to OC for you.

All of these scenarios seem to make a case in favor of a gag strap. And, really, in favor of a gag strap and a BOV.

Insight from someone who has more experience (which ain't sayin' much!) would be very welcome!!
 
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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.

I just want to emphasize again that the gag strap is stretchy and it is not going to prevent anyone from taking the DSV/BOV out of their own or someone else's mouth.

If you take the DSV out and push it up, to float above the diver's head, the strap might pull the mask strap off as it comes off. If you take it out and down, to position the DSV on the divers' chin area, it won't even do that.

I'm not saying the gag strap creates NO additional risk when only using a DSV. I just think it does not add as much risk or complication as you seem to be thinking.

But, that is presuming a BO reg stowed on its cylinder. If the BO reg is on a bungee necklace, then yes, it would be a bit problematic, I think.
 
I use a BOV and a gag, I came back to diving after a long lay off (nearly 20 years) but knew that I would end up on an RB so intentionally went with that option without going back via OC.

After a lot of reading I was happy that 2 of the pre-requisites for me would be a BOV and a gag. I love the ability to take sanity breaths if it all gets a bit much, the reduced risk of loose lips and a compromised scrubber, the hassle of removing the gag on the surface reduces the risk of removing the mouthpiece with an open loop and flooding the unit, the weight of the BOV is reduced leading to a more relaxed experience and at the beginning of a dive its easier to set the gag up out of the water at say an OHE site, so the risk of a flood/partial at the beginning is also reduced.

I think it may be different diving solely a DSV, but I have only ever used a BOV so don't have the exposure to call it, I am also not using hypoxic dil so this does make a difference obviously.

Thinking through the negatives the main issue i could see with the gag was if the BOV ended up caustic forcing a swift switch, i neck bungee my deep bailout second stage just in case, to reduce fumbling.
 
if the BOV ended up caustic forcing a swift switch, i neck bungee my deep bailout second stage just in case, to reduce fumbling.

I've seen some other posts that alluded to this, too.

I have no experience with a BOV (yet). If the loop goes caustic, why does that mean you can't switch to OC on the BOV? I gather there could still be caustic in the BOV plenum, but wouldn't a quick press on the BOV purge button blow it out, so you could start breathing on it without inhaling (any more) caustic?
 
This could totally be my newbness showing, so please help me understand where I'm going wrong in these thoughts.

The 3 main things we worry about on CCR are hypoxia, hyperoxia, and hypercapnia. Right?

In all 3 cases, the normal result, if unmitigated, is the diver loses consciousness, then loses the loop from their mouth, then drowns. In the case of hypoxia, even if they don't lose the loop, if the diver is breathing something hypoxic enough, I guess they will eventually die anyway. And if they are hypercapnic, again I suppose that even if they don't lose the loop, they will eventually die, right?

But, am I correct in thinking that, in all cases, if the diver loses consciousness and the loop stays in their mouth and at least somewhat sealed against flooding, their chance of survival is substantially increased?

I feel pretty safe in saying that if you go hyperoxic, have a CNS OxTox hit, and eventually pass out, as long as the loop stays in and doesn't flood, you will survive (pending no other complications, of course, like dropping to the bottom of the Marianna Trench while unconscious).

If you pass out from hypoxia, I am thinking that continuing to breathe a hypoxic mix will still keep you alive for longer than if you inhale water. If you lose depth, your hypoxic mix might even become breathable again and possibly you will revive on your own? Do you stop breathing quickly after losing consciousness from hypoxia? I think you do not, but I don't know for sure.

The big question mark in my mind is hypercapnia. I suspect that if you go hypercapnic to the point of LOC, the only way you are going to even have a chance of coming back from that is if you get much shallower (maybe) or to the surface and have a chance to start breathing surface air. Or if you have a BOV and someone switches it to OC for you.

All of these scenarios seem to make a case in favor of a gag strap. And, really, in favor of a gag strap and a BOV.

Insight from someone who has more experience (which ain't sayin' much!) would be very welcome!!

I don't have much more experience than you, but all three scenarios involve the loop being filled with unbreathable gas. So it's unlikely that there will be a spontaneous recovery without your buddy intervening, even if the gag strap keeps your loop in. I gave a class at BTS about mixed OC/CCR buddy teams, and the one thing that I think that every OC buddy should know is how to hold the loop in and do a dil flush, preferably while ascending and venting. Otherwise, what difference does it make if the loop stays in, why would you spontaneously recover?

Once you lose consciousness from hypoxia, that's pretty much it unless you get breathable O2 - it's not like you can survive for a long time breathing a hypoxic mix. I'm sure that you can figure out scenarios where your loop becomes hypoxic and then somehow the solenoid starts working again or something, but that's not likely.

I don't know what happens if you ox-tox, seize, recover from the seizure but are still breathing a hyperoxic mix. Hard to believe that you would just wake up and be OK.

Same with hypercapnea. Unless someone changes the loop contents, you aren't going to just recover. Maybe if you become hypercapneic from overworking and then pass out but keep the loop in, the scrubber will eventually catch up? Not sure about that one...

So I guess a good question for all of the pro-gagstrap people is "do you dive solo"..?
 
I don't have much more experience than you, but all three scenarios involve the loop being filled with unbreathable gas. So it's unlikely that there will be a spontaneous recovery without your buddy intervening, even if the gag strap keeps your loop in. I gave a class at BTS about mixed OC/CCR buddy teams, and the one thing that I think that every OC buddy should know is how to hold the loop in and do a dil flush, preferably while ascending and venting. Otherwise, what difference does it make if the loop stays in, why would you spontaneously recover?

Once you lose consciousness from hypoxia, that's pretty much it unless you get breathable O2 - it's not like you can survive for a long time breathing a hypoxic mix. I'm sure that you can figure out scenarios where your loop becomes hypoxic and then somehow the solenoid starts working again or something, but that's not likely.

I don't know what happens if you ox-tox, seize, recover from the seizure but are still breathing a hyperoxic mix. Hard to believe that you would just wake up and be OK.

Same with hypercapnea. Unless someone changes the loop contents, you aren't going to just recover. Maybe if you become hypercapneic from overworking and then pass out but keep the loop in, the scrubber will eventually catch up? Not sure about that one...

So I guess a good question for all of the pro-gagstrap people is "do you dive solo"..?

But, if the loop is hyperoxic and somebody takes you up, it will become normoxic.

If the loop is hypoxic and you pass out and start to descend, the loop will (presumably) become normoxic.

And yes, I was also wondering if a hypercapnic loop might eventually "catch up" - in particular, if the diver is passed out but still breathing and someone takes the diver up (thus reducing gas density).

The point being, there are cases where an unbreathable loop COULD become breathable without changing the gas contents. And even if they don't, my question was/is isn't that "unbreathable" loop still going to keep you alive longer than having the loop come out of your mouth (during LOC)? I.e. give you at least a little bit better chance of surviving long enough to be rescued.

Something I wonder about regarding having someone else do a dil flush to your loop for you is that a full loop is very hard to breathe on, just like a near-empty loop. So, if someone else was trying to do a dil flush, it would need more than simply jamming on the dil MAV. Is that feasible? If your buddy is also a CCR diver, maybe. If they are only trained for OC? Not sure a quick explanation during the pre-dive conversation is really going to cut it.

It seems even more like having a BOV that someone can flip to get you on a breathable gas is the best way to go. Of course, there is still the issue of possibly having a hypoxic mix connected to the BOV and what happens if someone flips your BOV switch and then tries to surface you. I reckon if I'm going to be diving with hypoxic mixes (sometime, way down the road), I'd probably want to stick to only diving with a buddy that is also a CCR diver and has been thoroughly versed in my rig, as I would need to be for my buddy's rig.

Every time my thinking delves further into diving with hypoxic gases, the idea of it makes me even more nervous. No other prospective diving has ever made me nervous. But, the prospect of hypoxic gases definitely does.
 
Stuart I read of a few incidents that alluded to the cocktail adhering to the BOV given that the common pathway is shared, which was what lead me to include the necklaced bungeed 2nd stage, it replicates doubles and as I dive solo a lot, just enhances confidence.

My BOV feed and secondary are piped in and around the unit to their first stage which stays clipped to the harness and is then fitted to the cyl during kit up.

I am pondering adding a QD to be able to pre-rig the 1st stage to the cyl, but it is additional failure points etc.
 
But, if the loop is hyperoxic and somebody takes you up, it will become normoxic.

Right, that's the buddy thing that I mentioned. You need outside intervention. I would go with a dil flush rather than hoping that a buddy could put me in the breathable PO2 zone solely by ascent, but your way would work too.

If the loop is hypoxic and you pass out and start to descend, the loop will (presumably) become normoxic.

OK, now THAT is some serious wishful thinking! Are you planning dives with a bottom depth that just far enough a hard bottom so that if you pass out from hypoxia, you will land on the bottom at an acceptable PO2? I guess if you are doing a dive over a deep bottom, you can hope that you wake up before you die from hypoxia, but also before you descend into hyperoxia! :D

IAnd yes, I was also wondering if a hypercapnic loop might eventually "catch up" - in particular, if the diver is passed out but still breathing and someone takes the diver up (thus reducing gas density).

Yeah that would be a case where you might have spontaneous recovery, as long as the hypercapnea was from overbreathing and not from scrubber failure.

The point being, there are cases where an unbreathable loop COULD become breathable without changing the gas contents. And even if they don't, my question was/is isn't that "unbreathable" loop still going to keep you alive longer than having the loop come out of your mouth (during LOC)? I.e. give you at least a little bit better chance of surviving long enough to be rescued.

If the loop doesn't become breathable, and nothing changes (apart from the scrubber catching up), I don't see how the extra time being alive but unconscious is going to make much of a difference. It comes down to quantifying "a little bit". There are a lot of things in medicine that are statistically significant but clinically insignificant.

Of course, we can come up with all sorts of unusual scenarios, but then you need to ask if the very small increase in safety is enough to justify using a BOV for people who don't want one for other reasons. Hey, you can reduce your risk of hypoxia by not diving deep with hypoxic dil, right? Like everything else, it's a tradeoff...

Something I wonder about regarding having someone else do a dil flush to your loop for you is that a full loop is very hard to breathe on, just like a near-empty loop. So, if someone else was trying to do a dil flush, it would need more than simply jamming on the dil MAV. Is that feasible? If your buddy is also a CCR diver, maybe. If they are only trained for OC? Not sure a quick explanation during the pre-dive conversation is really going to cut it.

Better than not having a pre-dive conversation. Showing someone how to do a dil flush includes showing them how to dump gas. There is an overpressure valve, and from a practical matter (although I haven't done it for real), I'll bet that if you do a dil flush on an unconscious diver while holding the loop in his mouth (with or without a strap), gas is going to leak around the mouthpiece to some degree before it goes through the OPV. The mouthpiece is just not that tight a seal with an unconscious diver.

It seems even more like having a BOV that someone can flip to get you on a breathable gas is the best way to go. Of course, there is still the issue of possibly having a hypoxic mix connected to the BOV and what happens if someone flips your BOV switch and then tries to surface you. I reckon if I'm going to be diving with hypoxic mixes (sometime, way down the road), I'd probably want to stick to only diving with a buddy that is also a CCR diver and has been thoroughly versed in my rig, as I would need to be for my buddy's rig.

I agree. And ideally, when you bail out your unconscious buddy, unless he or she has had a major medical event, they may wake up and be able to do their own ascent, so hypoxic bailout gas not such an issue. Even if you had to surface an unconscious diver through the hypoxic zone, I would think at that point you would be moving fast enough so that the brief period of additional hypoxia wouldn't be the limiting factor in successful surface resuscitation.

Every time my thinking delves further into diving with hypoxic gases, the idea of it makes me even more nervous. No other prospective diving has ever made me nervous. But, the prospect of hypoxic gases definitely does.

I'm with you, buddy. Let's stay normoxic!
 
OK, now THAT is some serious wishful thinking! Are you planning dives with a bottom depth that just far enough a hard bottom so that if you pass out from hypoxia, you will land on the bottom at an acceptable PO2? I guess if you are doing a dive over a deep bottom, you can hope that you wake up before you die from hypoxia, but also before you descend into hyperoxia! :D

[snip]

Better than not having a pre-dive conversation. Showing someone how to do a dil flush includes showing them how to dump gas. There is an overpressure valve, and from a practical matter (although I haven't done it for real), I'll bet that if you do a dil flush on an unconscious diver while holding the loop in his mouth (with or without a strap), gas is going to leak around the mouthpiece to some degree before it goes through the OPV. The mouthpiece is just not that tight a seal with an unconscious diver.

My wishful thinking was based on thinking that if you are breathing something that is not hypoxic and then it goes hypoxic, it's not going to go from, say 0.16 PO2 to 0.0 instantly. If it drops all the way to 0.12 before you pass out, it still won't require descending all THAT much to get back in the normoxic range. Well, depending on what depth you're at when it goes hypoxic, of course. Obviously, if you're already at or near your max depth, then you're screwed. The specific scenario I was thinking of was a case where my friend was in the water, descending on the shot line, paused to equalize because he had some sinus congestion, and somebody that got in after him didn't have their O2 turned on and passed out just as he passed my friend and his dive buddy. They saw the guy go limp and rescued him. Presumably, that guy's loop was hypoxic but only by virtue of being full of hypoxic dil. Which would have become breathable as he dropped. I'm not saying the guy would have come to. I don't know. I'm just saying that, in that situation it seems like a gag strap would have at least given that guy a SHOT at surviving (if there had not been anyone that saw him and rescued him).

If your loop goes hypoxic because you were on the bottom and ran out of O2, or your solenoid crapped out, or your sensors somehow screwed up in a way that indicated you still had O2 in the loop, well, there's probably nothing but a very good buddy that's going to save you.

As for a buddy doing a dil flush, the rEvo does not have an OPV on the loop that can be manually actuated. I.e. my buddy cannot vent my loop using any OPV. If the loop is full, it would push out past my mouth, but still be full - unless my buddy were to turn me so my mouth/DSV were at the highest point. Then it might vent without help. But, then it could vent to the point that the loop has too little gas in it to breathe. And trust me when I say that the rEvo ADV is unlikely to fire based on the breathing of an unconscious person.

So.... yes! I am sticking to normoxic mixes for a while! I expect to eventually go further in my training, but not any time too soon, for sure!
 
My wishful thinking was based on thinking that if you are breathing something that is not hypoxic and then it goes hypoxic, it's not going to go from, say 0.16 PO2 to 0.0 instantly. If it drops all the way to 0.12 before you pass out, it still won't require descending all THAT much to get back in the normoxic range. Well, depending on what depth you're at when it goes hypoxic, of course. Obviously, if you're already at or near your max depth, then you're screwed. The specific scenario I was thinking of was a case where my friend was in the water, descending on the shot line, paused to equalize because he had some sinus congestion, and somebody that got in after him didn't have their O2 turned on and passed out just as he passed my friend and his dive buddy. They saw the guy go limp and rescued him. Presumably, that guy's loop was hypoxic but only by virtue of being full of hypoxic dil. Which would have become breathable as he dropped. I'm not saying the guy would have come to. I don't know. I'm just saying that, in that situation it seems like a gag strap would have at least given that guy a SHOT at surviving (if there had not been anyone that saw him and rescued him).

Absolutely! Not as much of a shot at surviving as using a checklist, but a shot nevertheless...

:D



If your loop goes hypoxic because you were on the bottom and ran out of O2,

Bailout or SCR mode

or your solenoid crapped out,

MAV

or your sensors somehow screwed up in a way that indicated you still had O2 in the loop,

Ooohh, that's a tough one. Frozen board? Hard to imagine such a wide overreading otherwise... But yup, that would be bad, and a gag strap and a buddy would help.


As for a buddy doing a dil flush, the rEvo does not have an OPV on the loop that can be manually actuated. I.e. my buddy cannot vent my loop using any OPV. If the loop is full, it would push out past my mouth, but still be full - unless my buddy were to turn me so my mouth/DSV were at the highest point. Then it might vent without help. But, then it could vent to the point that the loop has too little gas in it to breathe. And trust me when I say that the rEvo ADV is unlikely to fire based on the breathing of an unconscious person.

I think in that scenario, it would leak around your mouthpiece regardless of orientation. Highest point only an issue for dewatering, if you just have a full loop the gas is going to escape through the path of least resistance wherever it is. Which in this case would be the mouthpiece.
 
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