How do deep free divers survive decomp sickness?

[wonbok]

Hi!

I watched the movie "The Grande Blue" the other day and was wondering how the deep free divers, who go as deep down as 400 feet and ascend within a span of few minutes, survive decompression sickness.
Could someone enlighten me?

Regards,

 

[mempilot]

They aren't breathing compressed air under pressure is the simplest explanation.

 

[wonbok]

They aren't breathing compressed air under pressure is the simplest explanation.

Maybe I should go back to diving 101, but I thought the cause of decomp is the water pressure affecting the solubility of nitrogen in the blood stream.
So, as long as the diver is not inhaling nitrogen, are you saying the nitrogen leven in the bloodstrem should not increase regardless of the depth?

 

[scubatoad]

Maybe I should go back to diving 101, but I thought the cause of decomp is the water pressure affecting the solubility of nitrogen in the blood stream.
So, as long as the diver is not inhaling nitrogen, are you saying the nitrogen leven in the bloodstrem should not increase regardless of the depth?

It's a depth vs time thing. They probably don't spend enough time breathing at depth to build up the extra nitrogen.

 

[Wildcard]

You can only absorb so much nitrogen from one lung full of air in a couple of minutes.

 

[RonFrank]

It's a depth vs time thing. They probably don't spend enough time breathing at depth to build up the extra nitrogen.

If you are not breathing at pressure there is no chance of DCS.

I never realized the amount of time some people can hold their breath... amazing...

Regardless, the reality is that if one is at 33ft the amount of O2 and Nitrogen is 2X as much as at sea level. At 66 feet, 3x. So if at 66ft one is getting 3x the amount of nitrogen than if at sea level... there is the problem. We all offgass nitrogen as a normal part of our system. I'm offgassing RIGHT now!!!

But offgassing 3x, or more as we go deeper is a factor. Add to that, the fact the bubbles are easily passed at depth, but expand as we surface.... The nitrogen does not poison us (as O2 can) per say, but it takes a while to off gass, and more so at sea level vs. under pressure.

Freedivers do NOT go through ANY of this, hence no DCS.

Ron

 

[Wildcard]

I met the static breath holding womens champ here a while back 5:59! Don't know how she holds her breath that long, she sure can't shut up at the surface.

 

[BillP]

If you are not breathing at pressure there is no chance of DCS.

Never say never (grin). Scubatoad and Wildcard are on the right track with their depth/time/available-nitrogen-in-one-breath comments as far as record-breaking freedivers is concerned, but there are reports of venous bubbles and decompression symptoms in aggressive repetitive freedivers. See:

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1490974

We all offgass nitrogen as a normal part of our system. I'm offgassing RIGHT now!!!

Well, yeah, that's true, I guess. But unless you've just undergone an ambient pressure change or a change in your breathing mix you are at a steady-state and "in-gassing" nitrogen as much as "off-gassing" with no net change.

But offgassing 3x, or more as we go deeper is a factor. Add to that, the fact the bubbles are easily passed at depth, but expand as we surface....

I guess I'm not quite sure what you're getting at here. I was under the impression that bubbles "passing" is not thought to be a significant factor in decompression illness unless there was some anatomical problem.

The nitrogen does not poison us (as O2 can) per say, but it takes a while to off gass, and more so at sea level vs. under pressure.

I'm confused again. Are you saying that you think that nitrogen off-gasses faster when you're at depth than when you're on the surface breathing the same mix?? Perhaps you meant that it takes longer to off-gas nitrogen breathing air at sea level than it does when breathing oxygen under pressure (say in a chamber)?

 

[Walter]

I ordinarily would have passed this thread by, then I saw a name I haven't seen in a long time. Bill, it's great to have you back! I hope we will be able to dive together again soon.

 

[BillP]

Thanks for the kind comments. Always good to hear from you, too.