DCS from O2 decompression

[Thalassamania]

May I shift the focus for a moment? Let's say that the conditions were met for the creation of an O2 bubble. How long might that bubble persist in the face of the active utilization and transport of oxygen within the body?

 

[gcbryan]

This is very controversial. Some people agree with you. Some people disagree with you. I for one do not see how it can, but others (especially UTD theorists) are fervid in their belief that it does.

This is no real controversy however. Medical science (and Henry's law) vs UTD "theorists" is not much of a controversy. It's more like a misunderstanding of facts. Most UTD divers who have read the underlying facts don't even buy this.

...
When there is no N2 in your lungs, then the ambient pressure is irrelevant as far as N2 is concerned. You have increased the pressure gradient between what is in your tissues (including blood) and the gas you are breathing, so the offgassing goes much faster.

It is simply wrong to say that ambient pressure is irrelevant. Offgassing goes much faster because you aren't taking in any more. However you wish to describe it that's still all that is going on.

 

[boulderjohn]

This is no real controversy however. Medical science (and Henry's law) vs UTD "theorists" is not much of a controversy. It's more like a misunderstanding of facts. Many UTD divers don't buy this as well.

I am not arguing the point. I am just reporting. UTD cites a chapter in a book by Dr. Bennett of DAN. I do not have access to the book. I asked DAN, and their replies, which I had trouble following, also seemed to support the idea that the O2 vacancy created by high PPO2 speeds up N2 releasing.

I believe this question deserves its own thread.

It is simply wrong to say that ambient pressure is irrelevant. Offgassing goes much faster because you aren't taking in any more.

We are not communicating well, and I am willing to accept blame for the problem. I honestly am not understanding what you are saying and am afraid that my replies are only increasing the confusion.

 

[PfcAJ]

Ya, I think we're all saying the same thing but in different terms.

 

[gcbryan]

Boulderjohn in reviewing some of the past posts I think we are saying more or less the same thing in the recent posts.

My original point to your original post regarding spending more time at 20 fsw before switching gas is that I don't think it's needed as the algorithm takes care of getting you to 20fsw without exceeding the M-value in the controlling compartment and changing the inspired gas from backgas to O2 doesn't result in any increase in the n2 level. It comes out faster because you are not taking it in anymore.

There is nothing going on that should exceed the M-value. ICD is different as that's going from a mixture lower in helium to one higher in helium.

Part of the confusion as far as our responses are concerned I believe is that I was addressing PfcAJ and his comments regarding the oxygen window and you answered so I made the comments I would have addressed toward him to you.

 

[deepmaxim]

May I shift the focus for a moment? Let's say that the conditions were met for the creation of an O2 bubble. How long might that bubble persist in the face of the active utilization and transport of oxygen within the body?

The bubble must contain all gases and not only O2. If you have O2 inside a bubble (becouse you have like me a counterdiffusion on 6m), you need a time, to eleminate this gas (O2) from bubble. For O2 you the same time, as for N2... And next problem is, that a concentration from O2 molecule in blood is very high, its means, that the O2 in Bubble cann stay longer...
The gas breaks can help, to eleminate O2 from a bubble... So paradox is it...

 

[Thalassamania]

I guess what I am really asking is what role does active transport of oxygen by the hemoglobin play in speeding the resolution of an oxygen bubble as opposed to an inert gas bubble that lacks this mechanism.

 

[deepmaxim]

Problem is not a hаemoglobine or O2 transport. The problem, is not solved О2 again (it all the same will be accepted by tissue faster, than chemically attached to haemoglobin), but oxygen in the gas form (inside the bubble). Gas molecules should pass in the beginning through bubble walls, and for this purpose they need time. That will be out of a bubble any more so interestingly.
Sorry for my english

 

[Thalassamania]

I thing that you have misunderstood my question, sorry.

 

[boulderjohn]

I have started a new thread that could be a better home to this question.