Breathing off the BC

Genesis · Jul 17, 2003

is ok in an emergency, other than possibly ending up with a respiratory infection (which beats drowning!)

REBREATHING the BC is VERBOTEN! Beyond the CO2 problem there is a much more serious issue - that of the PO2. As you ascend, the PO2 falls. A sufficient PO2 to sustain normal consciousness (0.16 or so) at 33' will be cut in HALF by the time you reach the surface. Each "rebreathe" will cut the FO2 of the gas in the wing, and as you ascend the PO2 falls. That's an ugly and extremely dangerous cycle that is very likely to kill you. O2-insufficiency (hypoxia) blackout is not preceded by "air hunger" as hypercapnia (excessive CO2) is, and the PPCo2 will also be reduced as you ascend, making a hypoxic blackout without warning VERY likely.

REBREATHING THE BC BLADDER IS ASKING TO PASS OUT ON THE ASCENT WITHOUT WARNING. DON'T DO IT UNDER ANY CIRCUMSTANCES!

Popeye · Jul 17, 2003

Genesis once bubbled...
is ok in an emergency, other than possibly ending up with a respiratory infection (which beats drowning!)

REBREATHING the BC is VERBOTEN! Beyond the CO2 problem there is a much more serious issue - that of the PO2. As you ascend, the PO2 falls. A sufficient PO2 to sustain normal consciousness (0.16 or so) at 33' will be cut in HALF by the time you reach the surface. Each "rebreathe" will cut the FO2 of the gas in the wing, and as you ascend the PO2 falls. That's an ugly and extremely dangerous cycle that is very likely to kill you. O2-insufficiency (hypoxia) blackout is not preceded by "air hunger" as hypercapnia (excessive CO2) is, and the PPCo2 will also be reduced as you ascend, making a hypoxic blackout without warning VERY likely.

REBREATHING THE BC BLADDER IS ASKING TO PASS OUT ON THE ASCENT WITHOUT WARNING. DON'T DO IT UNDER ANY CIRCUMSTANCES!

This couldn't be less true.

First, if I hold my breath, (exhaling for ascent), my lungs will be using the same amount of O2 from that quantity of gas if I was instead blowing it in and out of a bag, plus I have to bleed the precious gas away to avoid overexpansion.

Secondly, in any case you would be doing this, you have two choices:

Breathe the BC,

Breathe water.

Now, that may be a very difficult choice for some of you, but, I came around to my decision pretty quick.

To really put this to the test, sit on the couch, and time a breath hold. If you really want to be accurate, vent your ooooooooooooo sound like you were ascending.

See how long you got.

Take a bag, or your BC, and breath into that.

Since I know we all maintain our gear properly, it should be clean inside.

No overexpantion danger here.

Don't do it till you pass out, you'll get plenty of warning.

Have someone else there if you're nervous.

Compare your time.

There's your answer.

How long is an ESA from 90 ft (my average drift depth)?

30ft/m preferable, 60ft/m probable.

90-180 seconds.

Let's see ya hold your breath for 3 minutes in a high stress situation.

The Chairman · Jul 17, 2003

teaches to "re-breathe" the BC.

In penetration diving, breathing off of the BC comes about when you are sharing air on a set of doubles or an H valve. You have donated your long hose (right post) and then have a problem with a free flow of your bungeed reg (left post) and have to turn it off. Since your inflator valve is ALSO connected to the right post, you breathe off of it. There is a fair amount of timing with this method and the first time you try it your buoyancy control goes down the tubes. But you breathe in and then exhale into the WATER.

This is NOT an open water technique. This is NOT for the casual or novice diver. It will NOT work when you are diving a single tank and are OOA.

The best you can hope for in an OOA situation is to suck the air out of your BC and hope that your buoyancy is not too reduced so that you can get up. You should NEVER re-breathe air. You should exhale the waste air into the water. It's not just the reduced O2 but also the increased CO2. The perfusion of CO2 out of your lungs works only if there is sufficient tension between the CO2 in your blood and the CO2 in the air you are breathing. If the CO2 can't get out (due to an increased PPCO2 in the bladder), then the mechanism to allow more O2 into your blood will be disturbed.

The very best way to deal with an OOA is to prevent it.
1) Check your gear and your buddy's gear before the dive. Two sets of eyes are better than one! Make sure you breathe both regulators and look at the SPG while doing so. The needle should remain steady.
2) Check your gauges often... more often the deeper you go.
3) Check your buddy's gauges as well.
4) STAY WITH YOUR BUDDY! (ten second rule)
5) Any equipment malfunction will end the dive (usually before all of the air goes flooey).
6) Switch to your buddy's air BEFORE you reach 0 psi! 200-300psi will give you just a tad more latitude on the surface. End the dive but don't forget your safety stop if you have sufficient air.
7) In the unlikely event that you find yourself OOA and OOB (Out of Buddy) at the same time, do an ESA. An ESA is best done with the right hand above you (like superman) and your left hand on the inflator valve and raised as well. Then, you will kick briskly to the surface, making the "n" sound (not a vowel, please) on the way up. Every thirty feet or so try your reg for additional air. There is a good chance you will find it! Once on the surface orally inflate your BC so that you have buoyancy. Watch for any signs of distress, barotrauma or DCS. 100% Oxygen would probably be a great idea.
8) Boyle's law will make sure you have enough air for the trip up (You won't need to reduce your buoyancy by breathing your BC).
9) Figure out where you need to improve your air management and buddy skills so it never ever happens again.

Popeye · Jul 17, 2003

NetDoc once bubbled...
The best you can hope for in an OOA situation is to suck the air out of your BC and hope that your buoyancy is not too reduced so that you can get up. You should NEVER re-breathe air. You should exhale the waste air into the water. It's not just the reduced O2 but also the increased CO2. The perfusion of CO2 out of your lungs works only if there is sufficient tension between the CO2 in your blood and the CO2 in the air you are breathing. If the CO2 can't get out (due to an increased PPCO2 in the bladder), then the mechanism to allow more O2 into your blood will be disturbed.

Totally irrellelavent when your alternative is breathing water.

You'll be using precisely the same air that you would have been -attempting- to keep in your lungs, plus whatever O2 rich gas is possibly in your BC, plus you'll retain air that you would otherwise be forced to vent to avoid overexpansion. Since you retain air that you would vent, you buoyancy would be -as positive- or more.

You'll be breathing this gas for a very short time, as a last resort to drowning.

<snip the power of positive thinking, since, we're discussing what to do -during- OOA. I think most folks here have a glimmer that avoiding one is preferrable>
7) In the unlikely event that you find yourself OOA and OOB (Out of Buddy) at the same time, do an ESA. An ESA is best done with the right hand above you (like superman) and your left hand on the inflator valve and raised as well. Then, you will kick briskly to the surface, making the "n" sound (not a vowel, please) on the way up. Every thirty feet or so try your reg for additional air. There is a good chance you will find it! Once on the surface orally inflate your BC so that you have buoyancy. Watch for any signs of distress, barotrauma or DCS. 100% Oxygen would probably be a great idea.
8) Boyle's law will make sure you have enough air for the trip up (You won't need to reduce your buoyancy by breathing your BC).

What if your path to the surface isn't clear, or your gear is hung up, or fishing line wraps around your fin? Kelp?

fins wake · Jul 17, 2003

... is an interesting discussion for people to follow.

Beyond the CO2 problem there is a much more serious issue - that of the PO2. As you ascend, the PO2 falls.

Correct, there is a ppO2 issue, but to be honest, the 0.16 (or even 0.15) mark will likely not be hit in a fast ascent, assuming an FO2 of 0.19-0.20 or so in the bladder at 10 metres (33 feet) when diving air. ppCO2 will however be an issue at any depth. But yes, oxygen fractions are also an issue. Incidentally, hypercapnia symptoms vary widely and cannot be relied on.

First, if I hold my breath, (exhaling for ascent), my lungs will be using the same amount of O2 from that quantity of gas if I was instead blowing it in and out of a bag,

I don't understand the thinking, but it seems like an irrelevant topic. O2 metabolism will always be the same irrespective of mode of breathing. Breathing into a bag and then inhaling again would obviously involve breathing gas with smaller fractions of oxygen, but I don't see how this has anything to do with the issue (other than reinforcing Genesis' point above).

Let's see ya hold your breath for 3 minutes in a high stress situation.

This is an aside, but I don't like seeing the term "breath-hold" used at all when discussing ESA's or ascents in any way, shape or form. Serious lung-over expansion injury can occur with only a 2 feet+ movement up the water column. Never hold your breath, folks.

There is a fair amount of timing with this method and the first time you try it your buoyancy control goes down the tubes. But you breathe in and then exhale into the WATER.

This is my understanding of GUE:s technique as well, and again, we're talking highly advanced divers being trained by highly skilled instructors. I'm sure MHK can comment on this.

This is NOT an open water technique. This is NOT for the casual or novice diver. It will NOT work when you are diving a single tank and are OOA.

Agree entirely. I find NetDoc's post as a whole very good, his 9 points for avoiding this situation are excellent.

You'll be using precisely the same air that you would have been -attempting- to keep in your lungs, plus whatever O2 rich gas is possibly in your BC,

Plus whatever CO2 is in your every single exhalation, between 2% to 5% a go (yes, I have measured this on myself under supervision while doing a DMT-type course).

Since you retain air that you would vent, you buoyancy would be -as positive- or more.

Yes, it would rapidly become very positive. In fact, you'd probably have to breathe out into the water in order to avoid an uncontrolled ascent with all its attendant risks of lung-expansion injuries, AGE and decompression sickness.

You'll be breathing this gas for a very short time, as a last resort to drowning.

Any form of useful information lies in this sentence, with a focus on very short time and an absolutely last resort to drowning.

However, NetDoc and others have suggested better ways of BC-breathing and they have emphasized that an OW diver OOA on a leisure dive really shouldn't end up in this situation, and given some good pointers on how to avoid it. Teaching newbie divers to plan for OOA:s using their BCD will - IMHO - lead to more incidents, accidents and fatalities, not less.

RICHinNC · Jul 17, 2003

actually from what i have seen on most boat dives....OOB's are not only common but the norm. I would define an OOB as one where the "B" is so far away as to be useless or not paying attention at all to where you are...or a combination of the two.

Laser · Jul 17, 2003

NetDoc once bubbled...
teaches to "re-breathe" the BC.

The best you can hope for in an OOA situation is to suck the air out of your BC and hope that your buoyancy is not too reduced so that you can get up.

I rarely have any gas in the wing when my tank is near empty?

JohnStrr · Jul 17, 2003

Hey, you talkin' bout my buddy? Seriously, I got paired up with a total idiot (I hate to say stroke) on my first ocean dive, I barely even saw him, and this is after talking about it on the boat. I guess he hit the water and forgot everything. Needless to say I stayed with the DM, he for one didn't mind having an extra tank nearby him

.

Popeye · Jul 17, 2003

Well, at least this ...
... is an interesting discussion for people to follow.

quote:
--------------------------------------------------------------------------------
Beyond the CO2 problem there is a much more serious issue - that of the PO2. As you ascend, the PO2 falls.
--------------------------------------------------------------------------------

Correct, there is a ppO2 issue, but to be honest, the 0.16 (or even 0.15) mark will likely not be hit in a fast ascent, assuming an FO2 of 0.19-0.20 or so in the bladder at 10 metres (33 feet) when diving air. ppCO2 will however be an issue at any depth. But yes, oxygen fractions are also an issue. Incidentally, hypercapnia symptoms vary widely and cannot be relied on.

But a theoretical chance of hypercapnia beats a 100% chance of drowning.

At least for me.

quote:
--------------------------------------------------------------------------------
First, if I hold my breath, (exhaling for ascent), my lungs will be using the same amount of O2 from that quantity of gas if I was instead blowing it in and out of a bag,
--------------------------------------------------------------------------------

I don't understand the thinking, but it seems like an irrelevant topic. O2 metabolism will always be the same irrespective of mode of breathing. Breathing into a bag and then inhaling again would obviously involve breathing gas with smaller fractions of oxygen, but I don't see how this has anything to do with the issue (other than reinforcing Genesis' point above).

So, what you're saying is, that re-breathing the air, as opposed to keeping it in your lungs, uses the same O2?

You'd be reinforcing me, not Karl.

Plus, you just may have some gas in the BC, enriching your mixture.

Plus, you keep O2 content you would otherwise vent.

Yet it's easily vented if necessary, for ascent control.

I'm -really- missing your logic, here, Fin.

It seems to me that during the finite period of an ESA, rebreathing your wing has the clear ability to provide you with -more- O2 than expelling your -last breath- while ascending.

quote:
--------------------------------------------------------------------------------
Let's see ya hold your breath for 3 minutes in a high stress situation.
--------------------------------------------------------------------------------

This is an aside, but I don't like seeing the term "breath-hold" used at all when discussing ESA's or ascents in any way, shape or form. Serious lung-over expansion injury can occur with only a 2 feet+ movement up the water column. Never hold your breath, folks.

Well, we were on the couch, but it never hurts to restate the perfectly obvious: (from above) "First, if I hold my breath, (exhaling for ascent), my lungs...".

quote:
--------------------------------------------------------------------------------
There is a fair amount of timing with this method and the first time you try it your buoyancy control goes down the tubes. But you breathe in and then exhale into the WATER.
--------------------------------------------------------------------------------

This is my understanding of GUE:s technique as well, and again, we're talking highly advanced divers being trained by highly skilled instructors. I'm sure MHK can comment on this.

Makes no sense during a single tank OOA. First, control of buoyancy is an ESA issue. You'll need to make adjustments whatever the case. Secondly, why waist air when we have a small and finite supply? Third, we're only doing this because our trip up has been delayed.

One of you makes the point that it will reduce buoyancy, one says it increases buoyancy.

Hmmmmmmmmm.

I say, either way, with the volume of gas that we'll have, it's inconsequential.

Buoyancy adjustments will have to be made at any rate.

quote:
--------------------------------------------------------------------------------
This is NOT an open water technique. This is NOT for the casual or novice diver. It will NOT work when you are diving a single tank and are OOA.
--------------------------------------------------------------------------------

Agree entirely. I find NetDoc's post as a whole very good, his 9 points for avoiding this situation are excellent.

Good info(the 9 points), but as Rick Murchisom pointed out, completely off topic. Maybe Rick can start a thread split on how to avoid OOA. I'm sure that Doc wouldn't have a single thing to say that I wouldn't agree with.

But it's just obfuscation here, for lack of substance.

As far as the Not,Not,Not, thing, hookus.

It's an individual choice, which you are telling everyone else here that they are too stupid to make for themselves.

I'm getting that itch again.

quote:
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You'll be using precisely the same air that you would have been -attempting- to keep in your lungs, plus whatever O2 rich gas is possibly in your BC,
--------------------------------------------------------------------------------

Plus whatever CO2 is in your every single exhalation, between 2% to 5% a go (yes, I have measured this on myself under supervision while doing a DMT-type course).

Absolutely. Inconsequential, that is. It's elevated CO2, or elevated seawater...

You have to be alive to get a headache.

quote:
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Since you retain air that you would vent, you buoyancy would be -as positive- or more.
--------------------------------------------------------------------------------

Yes, it would rapidly become very positive. In fact, you'd probably have to breathe out into the water in order to avoid an uncontrolled ascent with all its attendant risks of lung-expansion injuries, AGE and decompression sickness.

No different from any ESA. At least your chances of surfacing are greater.

quote:
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You'll be breathing this gas for a very short time, as a last resort to drowning.
--------------------------------------------------------------------------------

Any form of useful information lies in this sentence, with a focus on very short time and an absolutely last resort to drowning.

An option you'd deny to others, whatever the consequence.

However, NetDoc and others have suggested better ways of BC-breathing and they have emphasized that an OW diver OOA on a leisure dive really shouldn't end up in this situation, and given some good pointers on how to avoid it.

A factually baseless statement. Thanks, however, for stating that NetDoc does, infact, advocate BC breathing in some cirumstances.

Just like me.

I find it odd that the nay sayers dance gingerly around the solo diving issue, and the possibility of getting hung up.

Teaching newbie divers to plan for OOA:s using their BCD will - IMHO - lead to more incidents, accidents and fatalities, not less.

A grand opinion, opposite mine, of course.

I don't advocate teaching it to "newbies". Any certified diver has the same er, aegis, as you over what they wish to learn, regardless of experience.

I think that they're more interested it their own opinion of their capabilities, than one from an elitist.

Like solo diving, cave diving, teck diving, ect, the decision, and responsibility, belong to them, and them alone.
__________________

Popeye · Jul 17, 2003

JohnStrr once bubbled...
Hey, you talkin' bout my buddy? Seriously, I got paired up with a total idiot (I hate to say stroke) on my first ocean dive, I barely even saw him, and this is after talking about it on the boat. I guess he hit the water and forgot everything. Needless to say I stayed with the DM, he for one didn't mind having an extra tank nearby him .

According to others here, that makes you pooly trained.

I'd say it's a simple reality.

What are your thoughts?

Breathing off the BC

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