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Thread: Dive Risk Factors, Gas Bubble Formation, and Decompression Illness

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    Re: Dive Risk Factors, Gas Bubble Formation, and Decompression Illness

    I read someone mention recreational dives from the study .... Need to point out I understood the dives in the study were of all levels - DAN sums al of them in recreational diving... Cave, tech, deco...they all fall in recreational divies.

    The medium tissues mentioned I am not sure were the same ht as seen in heet maps from NEDU study... Need to check...

    Yes lot of question rising from the study..
    Unfortunately dr.Marroni is not on the forum. Andy, if wanted I can send him your questions and ask for comments... But can not promise answers...

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    Last edited by Igor P; 15th February 2018 at 13:07.

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    Re: Dive Risk Factors, Gas Bubble Formation, and Decompression Illness

    Quote Originally Posted by rjack  View Original Post
    The medium tissues were the same ones that appeared (based on the HEAT maps) to have peak surfacing loads and presumably bend divers in NEDU's deep stop study...

    Recreational divers might do 4 or more dives a day, those add up on "slow tissue" loads so that after surfacing at the end of a day, with air or perhaps 32% safety stops, the medium and slower tissues are going to be leading. It seems the GFs were developed/modeled from the profiles afterwards, not measured with physical data.
    The dives in the study were of all types... Deco, rec, cave, shore.... They are all sumed in recreational diving....
    At least I understood so ...

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    Last edited by Igor P; 15th February 2018 at 13:06.

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    Re: Dive Risk Factors, Gas Bubble Formation, and Decompression Illness

    Quote Originally Posted by rjack  View Original Post
    The medium tissues were the same ones that appeared (based on the HEAT maps) to have peak surfacing loads and presumably bend divers in NEDU's deep stop study...

    Recreational divers might do 4 or more dives a day, those add up on "slow tissue" loads so that after surfacing at the end of a day, with air or perhaps 32% safety stops, the medium and slower tissues are going to be leading. It seems the GFs were developed/modeled from the profiles afterwards, not measured with physical data.
    Thanks for that, had forgotten about the HEAT maps.

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    Re: Dive Risk Factors, Gas Bubble Formation, and Decompression Illness

    I would have appreciated some form of reasonable conclusion that I could apply to my life but I take away the knowledge that being a fat lazy diver doesn't seem to increase my DCS risk and most DCS is an undeserved hit so do what you wish and hope for the best

  5. #15
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    Re: Dive Risk Factors, Gas Bubble Formation, and Decompression Illness

    Quote Originally Posted by dreamdive  View Original Post
    I am surprised by the lack of more interest measured by responses of this article.
    That may well just be a reflection of how quiet this place (and other diving related forums) is nowadays...

  6. #16
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    Re: Dive Risk Factors, Gas Bubble Formation, and Decompression Illness

    Quote Originally Posted by dreamdive  View Original Post
    Thank you Silent Running for finding this article "Sex and the cardiovascular system: the intriguing tale of how women and men regulate cardiovascular function differently"

    Some thoughts:

    "Under conditions of cardiovascular stress (e.g., exercise, loud noises, or psychological stress) men respond by increasing mainly vascular resistance (TPR in*Eqs. 2*and*3), which is manifested as an increase in mean Pa*(blood pressure) (2), whereas women predominantly increase HR (Eq. 1), thereby increasing CO. In both cases, there is an appropriate cardiovascular response, but there are potentially different outcomes."

    An increase in vascular resistance suggests a decrease in gas uptake, whereas an increase in HR might increase gas uptake

    "Recall further that the control of blood pressure involves actions of the autonomic nervous system. On the one hand, there is a sympathetic drive (by analogy, the accelerator) to the heart and periphery. Increases in sympathetic activity in the heart results in both elevated contractility, which leads to increases in SV, and increases in HR. Either or both actions lead to an increase in CO. In the periphery, increases in sympathetic activity results in resistance vessel constriction with an increase in TPR. Reduction or withdrawal of sympathetic activity is analogous to taking one's foot off of the accelerator, thereby reducing SV, HR, and TPR. On the other hand, the parasympathetic (vagal) system (by analogy, the brake) slows the heart; withdrawal of parasympathetic activity unmasks the sympathetic drive.

    Recent studies of blood pressure control and cardiac function in healthy men and women have demonstrated that women and men use the two arms of the baroreflex system differently. At all ages, women were found to have reduced sympathetic activity (reflected by lower TPR and Pa) and enhanced parasympathetic activity relative to men"
    .

    An increase in parasympathetic activity would suggest a reduction in gas uptake but also a decrease in off-gassing. Increased sympathetic activity with increased cardiac output suggests an increase in gas uptake but coupled with peripheral vascular constriction, decreasing gas uptake. Net effect? An net increase in cardiac output could aid in off-gassing.

    This pertained to "healthy" males and females. People who have altered cardiovascular system due to hypertension/coronary disease/diabetes etc, have altered perfusion characteristics. It appears by this article that there exists a genetic difference between male and female compensatory mechanisms.

    Looking over the DAN Europe study, in the DCS group, I noticed that the age distribution of females between 10 years of age to 82. The male age distribution was between 23 - 67 years of age, although the mean was 37/42.

    The DAN Europe study also points out that although females had a higher propensity of getting bent notwithstanding similar bubble formation compared to males. Suggesting (indirectly) that gas uptake and off-gassing characteristics where similar?

    While looking for "triggers" of DCS, it appears that studies of this phenomena need to differentiate their approach to allow for gender differences.

    You're welcome Claudia, thanks for the excerpt and clarification. There are so many factors affecting how our bodies exchange gas that are not part of the models, it's really amazing there is not more significant DCS. Until we get more studies with more thorough methodology, we won't even know whether imputing our age, sex weight and height would help the models manage our risks.

    If we could learn why some bubbles bunch up and had a way to detect those types of bubbles in real time, that would be much better than any model...

  7. #17
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    Re: Dive Risk Factors, Gas Bubble Formation, and Decompression Illness

    Quote Originally Posted by Igor P  View Original Post
    I read someone mention recreational dives from the study .... Need to point out I understood the dives in the study were of all levels - DAN sums al of them in recreational diving... Cave, tech, deco...they all fall in recreational divies.

    The medium tissues mentioned I am not sure were the same ht as seen in heet maps from NEDU study... Need to check...

    Yes lot of question rising from the study..
    Unfortunately dr.Marroni is not on the forum. Andy, if wanted I can send him your questions and ask for comments... But can not promise answers...

    Igor P

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    Hi Igor, I forgot to answer this post, thank you very much for the offer. I think there are a variety of questions members might have, and I would encourage members to pose questions in this thread which hopefully can be passed along.

    I would like to know if any of the authors have theories as to why some bubbles are harmful and others are not. What makes some bubbles stick together and others are slippery enough to prevent aggregation? -Andy

  8. #18
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    Re: Dive Risk Factors, Gas Bubble Formation, and Decompression Illness

    Quote Originally Posted by dreamdive  View Original Post
    I am surprised by the lack of more interest measured by responses of this article. As rebreather divers and thus most of us doing decompression dives, has anybody wondered how GF's are supposed to be applicable to recreational divers?

    The article states that increased GF's presuppose you to getting bent - based on data collected from recreational dives.

    ????
    Andy also asked about an apparent lack of interest in this thread.

    I am not sure this is the case. I am often one to volunteer the simple even dumb question. I also am guilty of posting while under the influence of adult beverages. But I have not a lot to say about the article. Even to those stuck in a room with me.

    One thing that has been made clear to me is that there is little consensus about best practices using GF.

    I am not sure this study provides much clarity. Also I note that others draw different conclusions than I do. For instance I thought I should take some solace in my lean, low bmi. Someone plumper on here read into the piece reasons for comfort in his largeness.

    I think I shall crack a beer and re re read the piece.

    If I have something to say, I shall keep it to myself until sober. For now, I am not convinced that the methodology is conducive to drawing any too firm conclusions.

    I am interested though..

    Peter

  9. #19
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    Re: Dive Risk Factors, Gas Bubble Formation, and Decompression Illness

    Quote Originally Posted by PeterVICEG  View Original Post
    Andy also asked about an apparent lack of interest in this thread.

    I am not sure this is the case. I am often one to volunteer the simple even dumb question. I also am guilty of posting while under the influence of adult beverages. But I have not a lot to say about the article. Even to those stuck in a room with me.

    One thing that has been made clear to me is that there is little consensus about best practices using GF.

    I am not sure this study provides much clarity. Also I note that others draw different conclusions than I do. For instance I thought I should take some solace in my lean, low bmi. Someone plumper on here read into the piece reasons for comfort in his largeness.

    I think I shall crack a beer and re re read the piece.

    If I have something to say, I shall keep it to myself until sober. For now, I am not convinced that the methodology is conducive to drawing any too firm conclusions.

    I am interested though..

    Peter
    Paying attention, even after a few beers is all anybody can do Peter!

    To my mind, the fact this study raises so many questions ought to provoke lots of discussions. Unless there is some underwater consumer grade Doppler device coming we need better models. And that's not going to happen without more targeted studies. So let the discussion begin!

  10. #20
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    Re: Dive Risk Factors, Gas Bubble Formation, and Decompression Illness

    Quote Originally Posted by silent running  View Original Post
    Paying attention, even after a few beers is all anybody can do Peter!

    To my mind, the fact this study raises so many questions ought to provoke lots of discussions. Unless there is some underwater consumer grade Doppler device coming we need better models. And that's not going to happen without more targeted studies. So let the discussion begin!

    I have had a beer but... any study based on self reported data is suspect.

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