NITROX and SWB

I have what may seem like a funny question. When one freedives we are not supposed to hyperventilate for the fact that this 'tricks' our body - this is why the urge to breath is prolonged....Right ? (please correct me if I am wrong in any way)

So this brings me to my next question..... If I am breathing 36 EAN - it has a higher O2 than air.... so if Im sitting below a boat at 20' breathing off a tank, and dive down without the tank to say 65'-70' am I at GREATER risk for a SWB ? In other words - does the fact you are breathing higher O2 'trick' the body as does hyperventilation ??

I was doing this last weekend - Down to about 70'..... This is why I am asking....By the way I know the diving rules, Im EAN Certified, etc.... (before anyone asks)

Thanks everyone....

EIGHTWGT:

I have what may seem like a funny question. When one freedives we are not supposed to hyperventilate for the fact that this 'tricks' our body - this is why the urge to breath is prolonged....Right ? (please correct me if I am wrong in any way)

So this brings me to my next question..... If I am breathing 36 EAN - it has a higher O2 than air.... so if Im sitting below a boat at 20' breathing off a tank, and dive down without the tank to say 65' am I at GREATER risk for a SWB ? In other words - does the fact you are breathing higher O2 'trick' the body as does hyperventilation ??

I was doing this last weekend - Down to about 70'..... This is why I am asking....By the way I know the diving rules, Im EAN Certified, etc.... (before anyone asks)

Thanks everyone....

Click to expand...

I'm not sure I get that...:06:Can you re-phrase the question??? :06:

No.

You get SWB when your body runs out of oxygen before CO₂ builds up enough to trigger the urge to breath. If you're diving with scuba gear, you are breathing constantly, not holding your breath. So, no, you won't discover what SWB is like...

teknitroxdiver:

No.

You get SWB when your body runs out of oxygen before CO₂ builds up enough to trigger the urge to breath. If you're diving with scuba gear, you are breathing constantly, not holding your breath. So, no, you won't discover what SWB is like...

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I am not breathing constantly - I am asking if I am breathing Nitrox 36 at 15' (the tank is hanging on a line off the boat) and I then dive to depth holding my breath - am I at higher risk of SWB than if I was doing the same on air or hyuperventilating on the surface....

I hope I cleared up my question... sorry guys...

I don't think so, but I am willing to be corrected if I am missing something here.

Breathing EAN shouldn't increase the risk of SWB if you are not hyperventilating. Hyperventilating leads to SWB because it depresses the amount of carbon dioxide in your lungs, so that you run out of oxygen before feeling the strong need to breathe again.

If you increase the amount of oxygen in the breath you take before diving, but take a normal breath and don't hyperventilate, I don't think you will have done anything to reduce the amount of carbon dioxide in your lungs, and you should still feel the need to breathe at about the same time you would if breathing air.

I'm not sure that's correct, because I'm no expert on physiology, but that at least explains why I don't think breathing EAN should increase the risk of SWB. I'm not sure the elevated oxygen level in EAN will do very much, if anything, to *decrease* the risk of SWB, either, but that may be possible.

shallow water blackout is CO2 related

your "urge" to breathe is not caused by lack of O2. it's caused by too much
CO2 in your system.

by hyperventilating, you "flush" your system of CO2, thus lessening your need to
breathe. you can pass out before you "know" you need to breathe.
in other words, because the CO2 level in your blood is not high enough to
trigger the "breathe now" feeling, you can progress with a dive and deplete
the O2 in your blood before you realize it, thus passing out.

or, more realistically, as you ascend, your expanding lungs literally suck
the O2 out of your blood and there is no more... thus, most cases take
place within 15 feet of the surface.

so how does a higher percentage of O2 in your mix affect this?

my guess is that it will probably help you. since you are breathing more O2 in your
mix, you will have more time before you deplete the O2 in your system and
there will be more O2 for your expanding lungs to use.

however, the difference, if any, is going to be pretty small.

i am not a doctor. i don't know what i'm talking about.

Go to http://forums.deeperblue.net/ and and ask your question. These guys are into the free diving heavy and some one there will probable have an answer for your question. If you do go to deeperblue and get an answer, could you let us know what it is. I don't really think the EAN would contribute to SWB, but then like every one else said I could be wrong.

CO2 buildup is associated with a higher incidence of oxygen toxicity.

So you would not want to allow a CO2 buildup from breath holding at relatively high PPO2's (1.4-1.6). But on the other hand this is unlikely to occur free diving as your "loop" PO2 on 36% would be well below that at 60'-70' and the O2 percentage of the gas remaining in your lungs would be reduced by the time you got there anyway. It is however still a good idea to keep this in mind and be careful not to push it as your CO2 levels would on average be much higher than a scuba diver on 36% at comparabel depths. For example, I would not consider consider doing 70' dives on 50% Nitrox.

Your biggest risk would be starting the dive from 20 ft with a full breath and then surfacing at the end of the dive without exhaling.

DA Aquamaster:

Your biggest risk would be starting the dive from 20 ft with a full breath and then surfacing at the end of the dive without exhaling.

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This I am very aware of.... I was not really sure about the tox issues involved, hmmm, interesting....I only did a few 'dives' to the bottom..... and I came back up to the regulator - not the surface.....

Excuse my ignorance, What does SWB stand for???