Hypothetical question

See the first post for an explanation of the question related to the time to wait before flying.

  • No wait at all

    Votes: 55 65.5%
  • 6 hours

    Votes: 6 7.1%
  • 12 hours

    Votes: 7 8.3%
  • 18 hours

    Votes: 5 6.0%
  • 24 hours

    Votes: 11 13.1%
  • 48 hours

    Votes: 0 0.0%

  • Total voters
    84

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I am fairly new to all this decompression stuff, but doing my best to learn.
In this case, and please correct me if I'm wrong, there seems to be two different issues being talked about. Tissue loading and bubbles.
Seeing how the partial pressure on N is equal to or lower that 1 ata there would be no tissue loading and therefore no need for decomposition or wait time for flying.
Bubbles in the body expand when we ascend and since there is no tissue loading, wouldn't a controlled accent rate take care of the chance of bubbles forming? And once on the surface, with no loading, won't, in theory, all things be equalized? In fact if the partial N is higher on the surface then ongassing would start then.
Again this is my take on it, please let me know if I'm on the right track. Always trying to learn.
 
I can't find the cite anymore, somewhere on PubMed there's an old study that concluded that oxygen doesn't bubble nearly as much as nitrogen. I could never find much about how or why.



Yes but you're not going to metabolize 3 times as much O2 if you triple its content in your breathing mix. The "oxygen window" PP drop in the formula is only around 0.05. "Not bubbling" appears to be the key from what I read so far.
Hemoglobin is nearly completely saturated at 1 atm exposure on air. I don't think dissolved O2 makes up a large reservoir at increased pressures and is likely metabolized quickly. You are comparing inert gases to gas that is actively metabolized. Nitrogen and Helium are not oxygen
 
I am fairly new to all this decompression stuff, but doing my best to learn.
In this case, and please correct me if I'm wrong, there seems to be two different issues being talked about. Tissue loading and bubbles.
Seeing how the partial pressure on N is equal to or lower that 1 ata there would be no tissue loading and therefore no need for decomposition or wait time for flying.
Bubbles in the body expand when we ascend and since there is no tissue loading, wouldn't a controlled accent rate take care of the chance of bubbles forming? And once on the surface, with no loading, won't, in theory, all things be equalized? In fact if the partial N is higher on the surface then ongassing would start then.
Again this is my take on it, please let me know if I'm on the right track. Always trying to learn.

Unless you have no inert gas in your tissues (i.e. you have been breathing 100% O2 long enough to completely outgas all of your compartments), when you ascend, you can form bubbles.

Controlled ascent rates minimize this but don't eliminate it. A controlled ascent rate makes you surface with acceptably low levels of bubble formation, to the point where you won't have clinical symptoms of DCS on the surface.

So the question is, if you have silent bubbles in your system from this ascent - even though your initial N2 loading is no greater than it would have been if you had played tennis instead of gone diving - are those bubbles a clinical risk if you then ascend further to 8000 feet by flying in a commercial pressurized air cabin?

Perhaps they are, perhaps they aren't. But they do exist, because you were exposed to a drop in ambient pressure.
 
I'm sure it's been said, but I'm not reading 4 pages of answers.
Max ppN2 of EAN60 at 2ata is .8
Normal ppN2 of air is .8
You will have less total nitrogen after that dive than you did before you got in

That's the easy part. Read the rest of the thread and see if you can answer my question.
 
I don't think dissolved O2 makes up a large reservoir at increased pressures and is likely metabolized quickly.

I think you are absolutely right -- in a universe where conservation of energy does not exist. I'm not sure it works out quite like that on my planet.
 
That's the easy part. Read the rest of the thread and see if you can answer my question.

that is true, however the military has done a bunch of testing with rapid ascents immediately after diving and there are ways to skin that cat. Airline regulations limit cabin pressure to 8000ft, or .75ata. It's not a huge drop in pressure so while microbubbles are certainly there, I would have no issue making that flight.
 
Unless you have no inert gas in your tissues (i.e. you have been breathing 100% O2 long enough to completely outgas all of your compartments), when you ascend, you can form bubbles.

Controlled ascent rates minimize this but don't eliminate it. A controlled ascent rate makes you surface with acceptably low levels of bubble formation, to the point where you won't have clinical symptoms of DCS on the surface.

So the question is, if you have silent bubbles in your system from this ascent - even though your initial N2 loading is no greater than it would have been if you had played tennis instead of gone diving - are those bubbles a clinical risk if you then ascend further to 8000 feet by flying in a commercial pressurized air cabin?

Perhaps they are, perhaps they aren't. But they do exist, because you were exposed to a drop in ambient pressure.

Ok I see what you are saying. Thank you for taking the time to address my post.
 
The Question: Someone tells you that he or she needs to do a 90 minute dive to a maximum depth of 9 meters/30 feet using 60% nitrox. This person wants to know how long he or she should wait before flying on a commercial airline. What is your answer, and why?
My answer is not based on the math. If someone is asking what they should do, they can't be relied on to do or understand the math - or they wouldn't be asking.

It is safer IMO to not create an expectation in their mind that the no fly time is optional. There is a risk that they will consider it to be in the same category as a safety stop - desirable but optional.

I know if I can't figure out the answer on my own I am observing the no fly guidelines, so I would answer the question on the same basis.

.
 
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