Surface O2 use and bubbles

[diverrick]

I was reading a thread about using O2 after deep dives in the prevention of DCS, and that got me to thinking about why they would do this.
From what I know, (which is not much) When you come to lower pressures, (ascend), you start to off gas Nitrogen, happens every dive, just a matter of how much.
Nitrogen has a greater ability to attach to the hemoglobin then the O2 does, which can lead to hypoxia.
So I can see how it would help if you were hypoxic, but I cannot see how it would prevent the off gassing of Nitrogen as a result of using O2 after the dive. It would reduce the amount of Nitrogen your taking in after the dive, but the problem is the Nitrogen in your blood stream already in solution, and coming back out to a gas. I understand that if you are truly bent, you should have O2 to assist in your stabilization medically. Am I missing something here?

 

[ColdH2Odvr]

A couple of points to clarify: Nitrogen does not bond with the hemoglobin (I think you're confusing this with CO), it’s effectively inert and is simply in solution. As you descend, the partial pressure of nitrogen in your lungs increases above that of your blood. This gradient drives the nitrogen into your blood which then distributes it throughout your body where the process begins again. Decrease the concentration of nitrogen in your lungs, and you decrees the gradient (ie. nitrox). As you ascend the gradient reverses, driving the nitrogen out of your body/blood. Taking the nitrogen out of your lungs (breathing nitrox or pure O2) increases off gassing without increasing the size of the bubbles in your body.

This is the readers digest condensed version, for more info do a search on the oxygen window, etc.

Hope this helps more than hurts,

Dave

 

[Jai Bar]

In addition, breathing 100% on surface helps the Nitrogen off-gassing. Why? because after the dive the Nitrogen Partial Pressure (PPN2) in your blood/tissues is "X" and in your lungs it is approx. 0.8 (if you are breathing air) --> hence, the PPN2 difference between blood/lungs is "X-0.8". If your breathing 100% O2, then in the lungs PPN2 is "0" (No Nitrogen at all) and the difference between blood/lungs is simply "X". Which means that the gradient is higher and nitrogen goes out more easily.

The mentioned above has *nothing* to do with bubbles. Putting the "silent microbubbles" aside, if you have bubbles in the blood and/or tissues, it means that you have dived beyond NDL limits and/or made a too rapid ascent... 100% O2 will still help, but more likely one will need a recompression chamber for curing DCS/DCI.

 

[Kendall Raine]

By breathing pure O2, you are maximizing the dissolved and free phase inert gas gradient for any given pressure. This facilitates maximal inert gas elimination. In addition, providing 100% O2 to tissue speeds recovery from insult resulting from existing bubble formation.

After deep dives, we see much more rapid drop in post dive bubbles using a post dive oxygen soak than without. In space flight, oxygen pre-breathe during light excercise facilitates much more rapid preparation for EVA.

In addition, breathing 100% on surface helps the Nitrogen off-gassing. Why? because after the dive the Nitrogen Partial Pressure (PPN2) in your blood/tissues is "X" and in your lungs it is approx. 0.8 (if you are breathing air) --> hence, the PPN2 difference between blood/lungs is "X-0.8". If your breathing 100% O2, then in the lungs PPN2 is "0" (No Nitrogen at all) and the difference between blood/lungs is simply "X". Which means that the gradient is higher and nitrogen goes out more easily.

The mentioned above has *nothing* to do with bubbles. Putting the "silent microbubbles" aside, if you have bubbles in the blood and/or tissues, it means that you have dived beyond NDL limits and/or made a too rapid ascent... 100% O2 will still help, but more likely one will need a recompression chamber for curing DCS/DCI.

 

[BigJetDriver]

"The (information) mentioned above has *nothing* to do with bubbles. Putting the "silent microbubbles" aside, if you have bubbles in the blood and/or tissues, it means that you have dived beyond NDL limits and/or made a too rapid ascent... 100% O2 will still help, but more likely one will need a recompression chamber for curing DCS/DCI."

Jai Bar, et al,

The quote above is incorrect. Divers will ALWAYS have bubbles present in their circulatory system. These bubbles will range from microbubbles, to bubbles large enough to cause "bubble trouble".

The term "silent bubbles" is an older term referring to bubbles that are present in the diver but are not large enough to cause symptoms of DCI to appear.

In this usage, it has nothing to do with whether or not the diver has stayed within the NDL's, or with the speed of ascent. If the diver is "asymptomatic" in terms of DCS, then the bubbles in his or her blood are said to be "silent"!

Hope that helps! BJD :anakinpod

 

[iainwilliams]

Hello, I frequently use 100% O2 during the safety stop portion of a NDL dive or on the surface after a dive.

I have noticed that without its use (and deep stops) I used to get really tired. Now after deep stops and using O2, I never become tired.

I will breath O2 for 10-15 minutes after surfacing if I have not used O2 during my safety stops. If I use O2 on my stops I only use it from 5 m up (never deeper due to oxygen toxicity), and then I don't use it on the surface.

Works for me......Iain

 

[H2Andy]

diverrick, this was explained to me this way and it made sense:

goal during decompression is getting rid of excess nitrogen.

you can either inhale 79% nitrogen (air)

or

you can inhale 0% nitrogen (pure 02)

thus making the off-gasing of nitrogen faster.

they also explained why, but i'm afraid they lost me there.