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NITROX and SWB

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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eightwgt

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Jun 5, 2005
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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....
 
i know a lot of other people will have more detailed replies then me, but i know just from reading here and common sense that you should NEVER EVER breathe off of a tank at depth and then dive without it. Especially if you take a breath at 20 feet and then dive to 70, then go all the way back to the surface on that one breath, you are at a HUGE risk for damaging your lungs by the air in them exceeding the total lung capacity your lungs can handle. As to the swb issue, i think that anything that reduces your ability to feel contractions and oxygen levels would put you at a much greater risk for swb. Its your choice in the end i guess, but i strongly advise that you dont do that, and im sure that others will agree
dive safely,
rory
 
Rory

Thanks for the input - I just wanted to say I am VERY aware of Lung Expansion Injury problems associated with breathing compressed air at depth and ascending while holding your breath... Thats why I noted " I know the diving rules"

Thanks...
 
"In other words - does the fact you are breathing higher O2 'trick' the body as does hyperventilation ??"

First let me agree with what Rory said.

I don't know if 'trick' is the right word, but you would take the body where it's never been before. I've read a few accounts of divers that tried surface statics with 100% O2 and it's not something you'd do outside of a lab. In your 'what if' scenario, you would have about the same amount of useable O2. My guess is a small increase in dive time (CO2 limited) and a huge increase in danger from SBO, embolism and ?.

Aloha
Bill
 
Bill

Yes I here you......

I wanted to make clear that breathing Nitrox was not being done to attempt to prolong my breath hold..... I simply hand a pony bottle over the side of the boat sometimes on a 15-20 cord and suspend under the boat - with 2-3 dives to 50-60 feet... thats it, and usually only if I see fish. Thats why I asked the question because I really didnt know. I definately didnt push it the other day when I was doing it..... but thought about SWB afterwards.
By the way I am also aware 'bounce diving' is asking for the bends (hence why I only dive 2-3 times) and even then I ascend slowww.... I am also very aware the dive times come into play regarding the tables and any possible repeat dives on scuba and I do not do this often nor after I dive on Scuba.....
I know its not a real 'smart' thing to do.... and not promoting it.....
 
Tom,

You are definitely inventive aren't you?

I have no experience to give you with this one, but some observations that probably have already occured to you... or you wouldn't have tried this, or even gone fishing for answers after the fact.

On the issue of OE injuries, it wouldn't happen to an aware scuba diver/freediver, but it's certainly possible that you could get confused and forget your start depth, if you varied the formulas. Of course a little exhalation along the way could prevent the problem. (Hell I forgot to look around on one of 150 free dives on a recent oil rig trip and ran into a damn pipe on one ascent! Ouch!)

About SWB... a conditioned caused by low PO2 on ascent, most often achieved by exceeding the CO2 trigger by a normal air breathing freediver. But start out with an elevated PO2??? Could you get to the same low PO2, or are you just better off, like all nitrox tank divers?

Hmmm? You raise some interesting questions!

I'd like to hear from any divers with real experience in this realm, if there are any?

Chad
 
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I was with some nitrox divers in 1999 at the G.B. Church and I was going to try nitrox freediving, taking a breath off nitrox at the surface. There is already another detailed thread on this topic if you search.

Of course, all the warnings apply such as you must know exactly what you are doing and so on.

In the end, if you took a normal breath of nitrox and then did a freedive, you risk a blackout at the bottom from CO2. The extreme oxygen pressure will blunt the breathing reflex from the CO2, (this is different from low CO2 from hypereventilating).

The only way to avoid that is to hyperventilate a LOT, then take a breath of nitrox, but now you are playing with fire since there is really no way to know if you hyperventilated too much (low O2 blackout risk), or too little (CO2 blackout on bottom risk).
 
Effatah
Regarding the hyperventilation ...
What you are suggesting (or mentioned) does sound like suicide ! I am simply asking that if I am suspended at 15-20 NORMAL breathing on nitrox - take a deep breath and dive to depth, am I at higher risk - THATS IT... Im not trying to do anything special just hangin under the boat using a 30CF pony bottle is all and chadsin fish to depth if I see fit..... thats it - I take a deep breath and dive....

Chad....

Yea - I guess I am allways thinkin..... It is an interesting subject to explore and I like you would like to hear some more insight into this......

I was real close to heading your way tomorrow to dive but had no one to dive with..... tommorrow is the ole B-Day and I always try to dive.... but guess Im sittin at home buildin my new speargun instead.... :hmm
 
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It sounds like a pretty good way to get bent to me.

As far as the nitrox side of it goes, you have to be careful about C02 retention when breathing nitrox to begin with so freediving while breathing it would be like skip-breathing to the extreme. This can bring up all kinds of problems that you learned about in class and you should guard against any symptoms (v.e.n.t.i.d.)

Are you doing this with a buddy? Are you doing this after scuba diving- wondering why you would just have a 30 cu.ft. bottle of 36% laying around. Unless, it was a pony bottle left over from a scuba dive you just did.

I could see freediving for a day and then hanging out, not freediving, on a bottle of 50% or 100% at the end of the day to clean you out, especially if they had been deep dives.

The only advantage I can see from it comes to ear clearing- since your starting out with more gas in your lungs by taking a breath @ 30' compared to the surface, but that could be done on air and I still would be worried aobut getting bent from all that bouncing around.

Whatever you decide to do make sure you have a buddy watching you who can help you out if needed.


Happy birthday

Jon
 
Crazy stuff , I suggest if you learn to freedive better you won't need that pony bottle anymore anyway. Mixing scuba and freediving and then playing with gas mixes is right out on the fringe and the risks go way beyond your question on "swb". Bit like worrying about whether you locked the door when you left for work but plan to drive on the wrong side of the freeway all the way there....ie the door isn't what you should be worrying about. :duh Go scuba OR go freediving but whatever fish you are chasing it can't be worth the risk of mixing the scuba with freediving in the way you have described it......they're not that expensive!
 
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Jon

It is a good way to get bent -IF you maintain the dives - I only do it 1-2 times if I see a big fish....

I said above I did not do it before, or after diving (I know better) =)

Again - I was not looking for an advantage to doing this....

I had the pony bottle with me while fishing for the reason I used it - to hangout below the boat without using scuba.... I had it filled with EAN36 because I thought it may be a little safer to do 1-3 bounce dives with as described above...

anyway you look at it - it may not be a good idea..... I was simply curious if using EAN (any FO2) elevates the risk of SWB....

I am noting that you say there is a problem with C02 retention..... hmmm.. I honestly didnt recall this from my EAN training, perhaps a session with the books is needed. I have the books ; Diving Science, Deep Diving,Deep Sport Diving, DIR Fundamentals, and my SSI EAN book- Im going to browse through them all and see if I can find out more....

ADR / yea I know you are right - best not to mix scuba and freedives... and I AM NOT promoting the idea or suggestive that its ok - I was only curious ..... Id like to hear some more science facts on the subject
 
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eightwgt,

The summary is that if you take a normal breath of nitrox and then freedive, you are at high risk of CO2 blackout on the bottom. A CO2 blackout on the bottom means certain death, unlike a shallow water blackout (in which case your buddy MIGHT have a chance of saving you....)
 
I think Eric highlights probabaly enough of an issue all on it's own to move on from the aproach you are using. Before freediving I dabbled for a few years in tech diving and will try to run some profiles through some of the different programs I have to give you some idea of tissue saturations and associated risks but it's harder to do than it sounds when factoring in breath hold. ...the CO2 blackout risk alone is probably reason enough to leave the pony bottle on the boat.
 
Eric, Andy - Thanks - Ill look forward to the data.....

I read a lot last night and could not really find anything on the subject.

I guess I am a little confused why Eric says the risk for a BOTTOM Blackout is seemingly high.... I know that shallow breathing with a regulator does not properly vent off C02 - and hence why some people experiance headaches while diving.... that being said I always make it a habit to breath a lil deeper / fuller than normal when using Scuba at all times.... Thanks again guys - this is a very interesting topic and quite more complex than I had previously thought....
 
Questions such as the one you asked usually receive mixed reviews in this community. Diving is a science full of personal dogma.

Reading over all of this, it doesn't seem like anyone gave you a straight answer except Eric, and it seems that you misunderstood the fact that he gave you some useful info.

The results he talked about with his dives from 0 feet carry over perfectly to your dives from 15-20 feet. The only difference being the option of breathing gases which exists on the surface.

For explanation of the effect google "CO2 Blackout" The effect is related specifically to the breathing gas in question and therefore is a direct answer of your original question.

Personally, If I were engaged in a similar behavior, I think I would stick to compressed air.
 
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