Oxygen and dcs

[rwpatterson357]

Hope this is simple question with simple answer.

Why doesn't oxygen pose a risk for getting bent? I mean, don't you build up an excess of O2 in your tissue at depth that would bubble out if you shot out of water like a Trident missile?

thanks,
russ

 

[chrispete]

Your body metabolizes the O2. A state where there is too much O2 in the body would be O2 toxicity which is of concern to nitrox/mix/deep, deep air divers. At the point where your body can no longer metabolize all/enough of the available O2 it becomes overwhelmed and you simply pass out. Nitrogen cannot be metabolized, which is why it builds up.

 

[Kendall Raine]

There was some research on oxygen hits (DCS, not CNS tox) years ago. See Bennett & Elliott. Conclusion was this was not an issue. Suspect metabolic process and inherent unsaturation prevent O2 from being a DCS problem.

 

[Dr Deco]

Hello rw:

The body converts the food that we eat to energy and the building blocks for our body, and it metabolizes the oxygen. This gas does not exist for very long in the tissues as dissolved gas. It is quickly gone, and what little might be in a bubble is also quickly used.

Dr Deco :doctor:

 

[pipedope]

But good ascent controll prevents it.

Even if O2 bends does happen it resolves very quickly.

I have sent an email to JJ (of GUE) asking to quote a post he made on this subject. He is the man with direct experience.

 

[BRW]

All,

Tend to put "O2 DCS" in the mythical category,
sort of like that "DCS hit after an 8,000 ft
altitude excursion following non-diving" (which
means by now 10,000s of passengers should have
been so afflicted considering the millions upon
millions of passenger trips logged, plus using a
low incidence rate of 1/100,000 from real FAD
stats as quoted in my earlier posts).

Here's why, plus some other comments:

1) -- no stats, data, studies, nor reports
implicate nor corroborate O2 DCS (any
out there missed);

2) -- yet, even n=1 would be interesting;

3) -- assuming bubbles cause DCS, O2
diffusion across lipid and aqueous
bubble interfaces is very rapid
compared to DCS time scales (not
so for inert gaes like N2 and He).
So, even with inherent unsaturation
differing across venous, arterial, lung,
and tissue sites, O2 pressures in
bubbles would equilibrate rapidly with
their surroundings (venous and arterial
blood, inspired air in lungs, and tissue
sites). Check out Thermodynamic
Decompression by Hills for more on
same, plus other reasoning. Bottom
line is O2 likely doesn't cause DCS
bubble probs (like growth because
inside and outside O2 pressures
equilibrate rapidly across bubs
and venous, arterial, lung, and tissue
beds)

4)-- diffusion calcs for O2 across lipid
and aqueous skins (using material
properties)for arbitrary mixes
support above in theory too (see
RGBM In Depth and mass transport
coefficients therein listed for
diffusion calcs, and also Basic Deco
Theory And Apps, plus things in TDID);

5) -- same said for water vapor (H2O)
in the body, plus other trace
gases.

OXTOX, of course, is a different ball game
for sure. That's chemistry on top of mass
transport. Very tough problem.

Bruce Wienke
Program Manager Computaional Physics
C & C Dive Team Ldr

 

[pipedope]

Here is what Jarrod Jablonski had to say on O2 bends, reposted from the Quest List by permission of the author.

">jarrod jablonski wrote:
> >
> > The studies I mentioned were largely type II in animals though type I is
> > sometimes hard to identify in subjects that are not human; therefore, some
> > type I was likely also the case. These episodes are likely indicative of
> > significant oxygen bubbles that resolve quickly before sustained damage
> > occurs. I personally have only experienced transitory type I hits that
> > seemed to be O2 related. This occurred when we used to do all our Wakulla
> > deco in a dry habitat on oxygen at 30' and then ascend slowly once done.
> > The pain would be fairly significant in a joint but resolved within about
> > 30seconds. Now we do our deco at 30 and then a longish stop (about 20) at
> > 20' followed by a very slow (about 1min per foot) ascent to the surface.
> > The aforementioned symptoms no longer occur.
> >
> > Best,
> > JJ"

IOW It is not something to be worried about as it takes special conditions to happen and then does not do any serious damage. Modern procedures prevent O2 DCS completely.

 

[IndigoBlue]

rwpatterson357 once bubbled...
Hope this is simple question with simple answer.

Why doesn't oxygen pose a risk for getting bent? I mean, don't you build up an excess of O2 in your tissue at depth that would bubble out if you shot out of water like a Trident missile?

thanks,
russ

You would be at risk for CNS ox tox long before you were ever susceptible to DCS on pure oxygen. That is probably why there is no data nor evidence of DCS from oxygen.

 

[The Iceni]

BRW once bubbled...
. . .

3) -- assuming bubbles cause DCS, O2
diffusion across lipid and aqueous
bubble interfaces is very rapid
compared to DCS time scales
. . .

5) -- same said for water vapor (H2O)
in the body, plus other trace
gases.

Bruce Wienke
Program Manager Computaional Physics
C & C Dive Team Ldr

Yes indeed,

The oxygen rapidly dissolves and diffuses but it is also necessary for metabolism.

I guess any tissue damage would be limited by the fact that oxygen is present within the bubble and therefore in close proximity to the tissues that would readily be damaged by any block in the microcirculation caused by an inert nitrogen bubble.

For what it is worth, molecule for molecule, the oxygen is metabolised to carbon dioxide, which like oxygen is highly soluble and rapidly diffuses into the capillary tree and thence to the veins.

Same applies, toxicity is a problem with CO2 DCI is not.