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Thread: 5 min pre-breath at 1.8 PO2 to reduce DCS chance

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    5 min pre-breath at 1.8 PO2 to reduce DCS chance

    Hi, I am looking to see if any divers are doing a 5 min pre-breath at 1.8 PO2 before the dive to reduce DCS chance? It was recommended to me by an hyperbaric physician after a type 1 DSC. You are suppose to perform the pre-breath at 30 feet when entering water during big dives. It does make your CNS clock rise to the roof but reduce by 75% the chance of DCS apparently.

    Anyone doing this procedure?

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    Re: 5 min pre-breath at 1.8 PO2 to reduce DCS chance

    I have heard of such studies and it's not a new concept.

    Making a statement like reducing your chance of DCS by 75% is something that would need to be qualified. It's exciting, but it needs to be qualified before anyone can make an intelligent decision regarding its value.

    Since you have these numbers and this information, can you please post the entire study defining its details, so we can all enjoy the benefit of these conclusions.

    Its great to see new information and I am looking forward to learning more.

    Thanks!

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    Re: 5 min pre-breath at 1.8 PO2 to reduce DCS chance

    There are studies done on de-nitrogenation - this comes from the space/aviation industry and you can find the study on the Add Helium Reference Library. The idea is that you reduce the nitrogen inside micronuclei which are believed to be the "seed" for bubbles. If one gets rid of the "seed" than less bubbles are formed.

    I can also tell you that your physician does not have the numbers to proof his statement. There is no evidence that breathing 1.8 for 5 min will reduce your risk of DCS by 75%. Please pass this on to the doc you said this - so he does not lead anymore people astray.

    The studies also were done in non-decompression open circuit dives as I recall.

    What further complicates this: Even a reduction in bubbles does not reduce your chance of getting bent! New evidence suggests that there is a "cofactor" required to develop symptoms. There are multiple studies underway attempting to identify the/these cofactor/s.

    I don't know what your chance of O2 toxicity to reduction of "potential" DCS is with this maneuver. But until we get the ketotic studies back involving human trials, I would be careful.

    Claudia Sotis MD

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    Re: 5 min pre-breath at 1.8 PO2 to reduce DCS chance

    There was also a study about crushing micro nuclei seeds by spiking depth before starting the dive. Like bouncing down to 80 meters for a second and then ascending quickly back to your 150 foot dive depth. I don't remember the exact numbers and maybe Claudia can help. I think it was a Swedish study and supposedly had good results. But that was years ago and it certainly didn't become a mainstream practice.

    The point is that not everything that shows promise can be proven effective and not harmful. I'll trade a slightly higher risk of DCS for a lower risk of oxtox every time.


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    Re: 5 min pre-breath at 1.8 PO2 to reduce DCS chance

    Quote Originally Posted by kwinter  View Original Post
    I'll trade a slightly higher risk of DCS for a lower risk of oxtox every time.


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    Having seen the results first hand, I'd have to agree. I'd rather have a higher DCS risk, if thats the trade off.

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    Re: 5 min pre-breath at 1.8 PO2 to reduce DCS chance

    Thanks for the input guys. I went to visit the centre for experimental diving and environmental medicine but many researchers had split opinion on this (both the medical and mathematical side). They also work with much different table regarding exposure to CNS clock (which come from a different acceptance of risk since it is mostly for military purpose). As a few of you mentioned, it is a bit early research wise to back the O2 pre-breath procedure. Below are a few studies showing some results.

    http://www.ncbi.nlm.nih.gov/pubmed/19219451

    http://www.ncbi.nlm.nih.gov/pubmed/21199400

    http://www.ncbi.nlm.nih.gov/pubmed/20185629

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    Re: 5 min pre-breath at 1.8 PO2 to reduce DCS chance

    Quote Originally Posted by brown211673  View Original Post
    Thanks for the input guys. I went to visit the centre for experimental diving and environmental medicine but many researchers had split opinion on this (both the medical and mathematical side). They also work with much different table regarding exposure to CNS clock (which come from a different acceptance of risk since it is mostly for military purpose). As a few of you mentioned, it is a bit early research wise to back the O2 pre-breath procedure. Below are a few studies showing some results.

    http://www.ncbi.nlm.nih.gov/pubmed/19219451

    http://www.ncbi.nlm.nih.gov/pubmed/21199400

    http://www.ncbi.nlm.nih.gov/pubmed/20185629
    The old M-Plan deco planner written by Will Smither which predates v-planner had a setting called the Scammahorn slide. It allowed a rebreather diver to spike their PO2 on the initial descent and credited the ascent time based on the higher PO2 exposure at the start. I am not sure exactly how it worked but it sounds like a similar type of thing.
    Cheers,

    Dave....

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    Re: 5 min pre-breath at 1.8 PO2 to reduce DCS chance

    Quote Originally Posted by brown211673  View Original Post
    Thanks for the input guys. I went to visit the centre for experimental diving and environmental medicine but many researchers had split opinion on this (both the medical and mathematical side). They also work with much different table regarding exposure to CNS clock (which come from a different acceptance of risk since it is mostly for military purpose). As a few of you mentioned, it is a bit early research wise to back the O2 pre-breath procedure. Below are a few studies showing some results.

    http://www.ncbi.nlm.nih.gov/pubmed/19219451

    http://www.ncbi.nlm.nih.gov/pubmed/21199400

    http://www.ncbi.nlm.nih.gov/pubmed/20185629
    The first study is in our collection. It was based on 30 minutes 30 meter OC dives and measured bubble scores. Nobody developed DCS.
    The second study is meaningless for what you are arguing - it is NOT about DCS reduction but argues for reduction of ROS (are you actually reading AND comprehending studies like this?)
    The last study has the following statement in its concluding section: "Prebreathing NBO and HBO significantly alleviated decompression-induced platelet activation." Which brings me back (or is trying to bring you back) to my original point that bubbles alone are less important than discovering the potential cofactors to DCS. Do you know what they are talking about? Do you understand cause, effect, implications of platelet activation? Do you have a clue what platelet activation and DCS might mean?

    Considering your choices of studies you are bringing up, are you seriously arguing in favor of this "dive" physician's advice you supposedly received or ....what? I have suggestion, why don't you let that "dive" physician provide you with the studies that back up his claim to you.

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    Re: 5 min pre-breath at 1.8 PO2 to reduce DCS chance

    Quote Originally Posted by wedivebc  View Original Post
    The old M-Plan deco planner written by Will Smither which predates v-planner had a setting called the Scammahorn slide. It allowed a rebreather diver to spike their PO2 on the initial descent and credited the ascent time based on the higher PO2 exposure at the start. I am not sure exactly how it worked but it sounds like a similar type of thing.
    The result was simply a change in the color of the grey... :)

    Those were the days... We were fully aware that we did not know what we were talking about. The bigger challenge today is that many don't realize that...

    Dive Safe!!

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    Re: 5 min pre-breath at 1.8 PO2 to reduce DCS chance

    Quote Originally Posted by dreamdive  View Original Post

    Considering your choices of studies you are bringing up, are you seriously arguing in favor of this "dive" physician's advice you supposedly received or ....what? I have suggestion, why don't you let that "dive" physician provide you with the studies that back up his claim to you.

    Thanks for the info dreamdive. I am not arguing for nor against pre-breath, just getting the opinion from the community on the info provided from a physician. I only have access to the abstract of those studies, please provide the link if you find any full text. I am trying to see if anyone does pre-breath in the tech diving community, its benefits and it downsides. If you do have good info on this, please provide.

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