oxygen toxicity while free diving

[lordoftheOrings]

just a question .......

me and a few mates have been discussing a problem ......

if you were to breath 100% oxygen at the surface (1ata) and were to dive down to say 20m would you get ox tox
being that your breathing from 1 atmospere and going to 3...

does the partial pressure affect you when you are on a breath held dive? i know that if you were to be on scuba at this depth you would most definately be screwed

but does the pressure affect the pp of O2 when you are on a breath held dive seing its not being constantly breathed

haha just reading through ......no we are not dive geeks but are very passionate and we argue alot

 

[James connell]

lordoftheOrings once bubbled...
just a question .......

me and a few mates have been discussing a problem ......

if you were to breath 100% oxygen at the surface (1ata) and were to dive down to say 20m would you get ox tox
being that your breathing from 1 atmospere and going to 3...

for the same reason you can get bent free diveing, you could oxtox - IF you could stay down long enough. it's not likely to happen - by the same token if you went deep enough,long enough you could tox on air.

ever since the major agaencies have tried to justify rediculous prices for a POS dog simple nitrox course, the O2 tox thing has been blown WAY out of proportion. you don't tox on the first breath of 100% O2 as soon as you go below a given depth.

 

[Brian1968]

James connell once bubbled...


for the same reason you can get bent free diveing, you could oxtox - IF you could stay down long enough. it's not likely to happen - by the same token if you went deep enough,long enough you could tox on air.

ever since the major agaencies have tried to justify rediculous prices for a POS dog simple nitrox course, the O2 tox thing has been blown WAY out of proportion. you don't tox on the first breath of 100% O2 as soon as you go below a given depth.

I would think it even less likely given that on a free dive that deep (why anyone would want to is beyond me but that's for another thread) the alveolar partial pressure of O2 (PAO2) will be steadily dropping and therefore so too will the arterial partial pressure (PaO2). Arterial and alveolar CO2 partial pressures (PaCO2 and PACO2) will be steadily climbing and I think this would be the limiting factor still. Also they will proportionately offset the PaO2 and PAO2 according to Dalton's Law.

One must take in to account that in a free dive there is no movement of air to and from the lungs as there is with SCUBA. Therefore the above mentioned pressures do not stay relatively constant (save for the effects of pressure changes due to depth).

Consider also that even if you were breathing 100% O2 at the surface you do not have a full atmosphere of O2 in the lungs. Again according to Dalton's law it is offset by the PACO2 and humidity in the gas.

It's way too late for me to do the math for all of this though.

Considering how fast CO2 rises during a breath hold, I too doubt that anyone could dive to 20 M for long enough to get a tox hit. If you can, you might consider contacting the Guinness people.

 

[The Iceni]

lordoftheOrings once bubbled...
If you were to breath 100% oxygen at the surface (1ata) and were to dive down to say 20m would you get ox tox
being that your breathing from 1 atmosphere and going to 3...

does the partial pressure affect you when you are on a breath held dive? i know that if you were to be on scuba at this depth you would most definately be screwed

Hi LoR,

CNS or pulmonary oxtox?

At risk of being critcised for overlooking the extreme profiles that some freedivers do, I cannot see any risk of either CNS or pulmonary oxtox.

Pulmonary oxtox

Take a look at the NOAA tables on pulmonary oxtox and you could work out the damage caused to your lungs over an extended period if you were to breathe 100% oxygen on the surface all day and night and then freedive. In practice I suspect the number of OTUs accumulated would be quite acceptable and well below the threshold of 1440 OTU/24 hrs.

Over a week? :- No data.

CNS oxtox

Same analysis. Over what period would the freediver be exposed to a ppO2 in excess of (an arbitrary)1.6 bar? Unless he uses a rebreather (or breathes an atmosphere of 100% O2) to flush-out the nitrogen load prior to the dive it is very unlikely that his alvelolar ppO2 will ever approach 3 bar.

Even then, it is not the avleolar ppO2 that is the critical factor in CNS oxtox, as I understand it the critical factor is a (prolonged) period of elevated tissue ppO2 in the substance of the brain. Metabolism and simple dilution of that slug of oxygen in the lungs means this is very unlikely to reach a critical level for a sufficient period to alter brain metabolism. :mean:

On the other hand there could be theoretical advantages. Perhaps that is the reason for your question? It would seem logical to infer that the more O2 the freediver has on board prior to his dive the less likely he is to suffer from dilution hypoxia during the ascent phase, with an associated loss of conciousness.

I am not sure that even this is a valid argument since oxygen does have a role in respiratory drive.

This would very much be uncharted waters.:doctor:

 

[CincyBengalsFan]

lordoftheOrings once bubbled...
just a question .......

me and a few mates have been discussing a problem ......

if you were to breath 100% oxygen at the surface (1ata) and were to dive down to say 20m would you get ox tox
being that your breathing from 1 atmospere and going to 3...

does the partial pressure affect you when you are on a breath held dive? i know that if you were to be on scuba at this depth you would most definately be screwed

but does the pressure affect the pp of O2 when you are on a breath held dive seing its not being constantly breathed

haha just reading through ......no we are not dive geeks but are very passionate and we argue alot

You could get OXTOX by breathing pure O2 before you freedive but not at 20M. Commercial divers that I know down in Louisianna use pure O2 in their recompression chambers down to 20M.

 

[DeepScuba]

Yeah Cincy, but that's in a chamber, where OxTox isn't as scary, nor as fatal. They use the on-off-on thing probably (O2-Air-O2). As it's obvious that O2 for any length of time WILL cause OxTox and that depth.

I agree with the Doc.

Would it be too simple to say that, the O2 is depleting in your lungs, so even though you're going deeper, the "use" of the O2 is still carrying on, with no replenishment (you're holding your breath). ANd as said, for how long??? Probably not long enough by a long shot.

Doc, is that a decent enough laymans answer?

 

[CincyBengalsFan]

DeepScuba once bubbled...
Yeah Cincy, but that's in a chamber, where OxTox isn't as scary, nor as fatal. They use the on-off-on thing probably (O2-Air-O2). As it's obvious that O2 for any length of time WILL cause OxTox and that depth.

I agree with the Doc.

Would it be too simple to say that, the O2 is depleting in your lungs, so even though you're going deeper, the "use" of the O2 is still carrying on, with no replenishment (you're holding your breath). ANd as said, for how long??? Probably not long enough by a long shot.

Doc, is that a decent enough laymans answer?

I wasn't trying to argue with anyone. And I did say "chamber" so thanks, I did realize I was talking about a "chamber" when I said "chamber". I was just pointing out that at 3 ATA they still occacionally use Pure O2 even though they usually don't take it beyond 2.5 ATA in a "chamber".

 

[The Iceni]

CincyBengalsFan once bubbled...
You could get OXTOX by breathing pure O2 before you freedive but not at 20M.

Not sure I undestand CBF?

Deepscuba once bubbled
Doc, is that a decent enough laymans answer?

That's about how I see it!

 

[CincyBengalsFan]

Dr Paul Thomas once bubbled...

Not sure I undestand CBF?

You can get oxtox by breathing pure O2 then descending below 20M but not by just diving to 20M.

 

[DeepScuba]

Mmmmmm, I don't believe it.

But who's up for proving it?