Oxygen as Preventative medicine ? ?

[CD_in_Chitown]

I can't find the thread but I seem to recall some concern voiced over an incident where a high-risk dive of some sort had been undertaken and the diver had surfaced and begun 100% O2 as a just in case preventative. I seem to remember the concern that this practice could prolong the appearance of DCI symptoms, or possibly mask them altogether.

While searching for this thread I did find an interesting discussion on pre-breathing O2 that diverged to post breathing and there were comments from our esteemed medical regulators that breathing 100% O2 post dive was an efficient way to washout, and that the practice would prevent DCI occurance.

Could I ask for some clarification here? I'm almost certain the first concerns were voiced on this board, but cannot find the thread in question. Am I imagining that part?

Chris

 

[Dr Deco]

Dear Chris:

I believe that there was some discussion that oxygen could “mask” DCS. I believe that it was finally understood that DCS is the result of a tissue gas phase. The larger this grows, the more problematic it becomes. In addition, below a certain point (apparently), there are not any problems and we simply have what are termed “silent bubbles.”

Oxygen will prevent the growth of the free-gas phase since there is not any dissolved nitrogen entering the capillaries from the arteries and the lungs. This is not exactly the same as “masking” since the gas phase does not really grow. In addition, the tissue nitrogen that is dissolved is carried away by the capillaries and the bubbles never grow at all. They are not delayed in their growth; they simply do not grow at all.

Thus oxygen breathing in certain situations could be of value when performed both underwater (during decompression) and while on the surface (where the decompression continues).

Dr Deco :doctor:

 

[Genesis]

And took the time and trouble to get DAN on the phone and grill them, as they were the claimed source of the advice to "don't do that."

After a lot of talking with different people, I finally got to a REAL doctor (there are a lot of folks at DAN that aren't!) and once we got past the "standard of care" stuff he agreed with the point that the Dr. above made (and which I had argued) - that if the O2 prevents or delays the onset of symptoms, its helpful, in that if the bubbles don't grow and thus produce no symptoms, you have no hit - and if they DO grow when you stop the O2 treatment, at least they no longer have as much oversaturation to draw from and thus should grow "less".

Bottom line - it might help or even prevent a hit if you have reason to believe you are at risk, and it won't hurt.

On my privately-owned, non-charter boat, I make clear that (1) I have O2 on board, (2) anyone is free to grab and use it, as the refills are extremely cheap, (3) I ain't a MD nor in any other way acting as a professional in the dive business - or captain business - so what you do in this regard is YOUR CALL, and finally (4) if you tell me you have symptoms of DCS or its obvious I'm using the RADIO to get that expert advice and will follow their instructions.

None of this "works" on a chartered boat, where there are legal "standards of care" that attach when you're exchanging money for services. If you ask for the O2 bottle on such a boat, its 90% certain or better that they will treat this as a declaration of DCS symptoms, will call EMS, etc.

I personally think this bites, but its what we get for being "sue happy" folks in this country.....

 

[Kendall Raine]

Genesis;

I saw the DAN admonition about the dangers of prophylactic post-dive O2 and thought their point was, to be nice, odd. It reminded me of Dr. Bennett's editorial that using Nitrox could complicate the HBO therapy if you subsequently took a hit. Remember that gem?

I'm not sure what Boogey men DAN is trying to guard against, but recommendations like this really make one wonder what goes on in that fancy new building.

Using O2 on the surface for, say 30 minutes, following a deco dive just as a precaution, has been SOP for a long time. Your approach to offering it up to anyone who even thinks they want it is right on.

 

[The Iceni]

Hi Chris,

I started the thread aluded to by Genesis .

An important adage in medicine is, "First do no harm".

I must therefore ask what harm could be derived from using 100% oxygen post-dive? The answer is none.

What certain agancies are concerned about is the masking of symptoms that would otherwise have developed, and the risk of a serious neurological DCI going untreated in consequence.

If you think about it, the vast majority of divers will not seek treatment (i.e recompression) if they suffer no symptoms after a dive, even if they have missed stops or had an aggressive profile. (Whether this leads to accumulated neurological damage over such a a diver's career is open to debate).

It therefore seems obvious that if a proven treatment (100% surface oxygen) is used prophylactically and no symptoms develop during or after that prophylactic treatment, a DCI hit has been treated or prevented.

To my mind it matters not which.

However, while 100% surface oxygen is a proven treatment it is not a cure for an established DCI. Recompression is quite obviously mandatory if symptoms develop during or after surface oxygen.

Since recompression "does no harm" I understand most elect to treat any post dive symptom as DCI and recompress.

I regularly used 100% surface oxygen to increase the margins of safety.