Deep Stops Increases DCS

[igor p]

Igor, can I ask exactly what you mean by "real dive profiles with known outcome"?

Simon M

Hi Simon,

Obviously I mean what is writen:
dives actualy dived with known outcome. Nothing more and nothing less.

 

[Dr Simon Mitchell]

Hi Simon,

Obviously I mean what is writen:
dives actualy dived with known outcome. Nothing more and nothing less.

Igor, well, let me put it like this, how does BRW know what dive profiles were actually dived?

Simon

 

[igor p]

Well let me put it like this: ask BRW and his peer's.

Simon we have been through this already. I do not agree with your about the subject for more you will never agree with me about anything regarding the same subject just because Ross is involved.
So here again our debate ends.

 

[Dr Simon Mitchell]

Well let me put it like this: ask BRW and his peer's.

I sense an evasive answer Igor.

My question addresses the most fundamental determinant of the credibility of the work, and I must say that given this is a study you repeatedly cite, you don't appear to understand it very well.

Simon M

 

[igor p]

Sorry Simon,

you sense wrong. It was my decision time agoo not to argue with you for reasons I posted. I posted BRW papers as info that needed to complete information about deep stop deco strategies. For more the first one that explains why A2 bent divers was posted by someone else. And need to say I read quite some very interesting toughts about the subject that were posted by other members.

As I wrote - ask BRW and his peer's for explanation. I understand his aproach quite well, and do not have problems with that.

I know you will never accept you could be wrong.

Talking about VPM-B. Yes there is place to improve. I can make conservatism setting for VPM that will be probably better than actual ones E. Baker designed, but you will never accept it for Ross being part of VPM history.

Now I am going back to read forum in silence...

Safe dives,

Igor P

 

[Dr Simon Mitchell]

Simon we have been through this already.

Actually, I don't recall ever asking you about the profiles in the BRW work previously but since you are citing the paper again it is time I did.

As I wrote - ask BRW and his peer's for explanation. I understand his aproach quite well, and do not have problems with that.

In that case, what could possibly be difficult about explaining how he obtained his profiles. It is a very simple uncomplicated question, but one that gets to the heart of the credibility of the work you repetitively cite. If you are going to rely on a body of work to strengthen an argument you are trying to make I think it is a bit unreasonable to refuse to answer questions about key aspects of it (especially when you claim to know the answers). One conclusion that people might draw is that there is some aspect you are trying to hide or avoid discussing.

Safe dives,

Thank you. You too.

Simon M

 

[leadduck]

For DCS risk, the area below the curves ("integral supersaturaion") is relevant to compare, not their maximum. And the x-axis better be time, not depth for that comparison. You can see in your own plots that the area below the NEDU-A2 profile is smaller than the one below the VPM-B+0 profile, which means that NEDU-A2 protects the fast tissues even more strongly than VPM-B+0, while ZHL-16C puts the most stress on them.

For the rest of your plots I think you miss the difference between compartments and show only the fast ones. Deep stops shift the supersaturation stress from the fast to the medium and slow compartments, so you're completely missing the point if you look only on a few faster compartments or just sum up all of them. UWSojourner's plot of integral supersaturation vs all compartment indices show this. There you can also see how similar NEDU-A2 and VPM prioritize fast vs slow compartments in terms of supersaturation, although their stop times and depth are different.

Simon, if you want to attack those adhoc methods, then go ahead. But please leave alone the peer reviewed, scientifically valid, published models like VPM, like RGBM. They don't need your fixing and fiddling.

All models including VPM and RGBM, and GF addition to ZHL, demand scrutiny. These in particular, because
(1) Unlike many other models and tables, their parameters were not calibrated with controlled experiments to minimize DCS risk, but were just set so that their runtime is similar to older methods and the curves look somehow familiar. If you use such an uncalibrated model with no experimental link to DCS risk, then you might as well just guess a runtime, take a paint program and just draw a curve that you feel looks right, and dive it.
(2) It's conspicuous how these uncalibrated and untested models were and still are pushed commercially with dive planning software and licensing to dive computer vendors. They promote an unhealthy habit of deep stopping among technical divers.

 

[igor p]

Actually, I don't recall ever asking you about the profiles in the BRW work previously but since you are citing the paper again it is time I did.

... not completely true... you already questioned it on other foums...not me directely but you did..

In that case, what could possibly be difficult about explaining how he obtained his profiles. It is a very simple uncomplicated question, but one that gets to the heart of the credibility of the work you repetitively cite. If you are going to rely on a body of work to strengthen an argument you are trying to make I think it is a bit unreasonable to refuse to answer questions about key aspects of it (especially when you claim to know the answers). One conclusion that people might draw is that there is some aspect you are trying to hide or avoid discussing.

Simon M

... I did more than you ask for. I pointed (BRW) Bruce Wienke to this thread. I asked him, if he feels something is to comment, to cime in.

Soo.... I have nothing to hide. Beside this he explain data collection in his papers too..

The only thing I avoid discusing with YOU is the deep stop tema for reasons I wrote in my previous post. I do comment (from my decision on) only on ocasions I decide information is not complete and a part is missing. Same I did this time.

 

[igor p]

All models including VPM and RGBM, and GF addition to ZHL, demand scrutiny. These in particular, because
(1) Unlike many other models and tables, their parameters were not calibrated with controlled experiments to minimize DCS risk, but were just set so that their runtime is similar to older methods and the curves look somehow familiar. If you use such an uncalibrated model with no experimental link to DCS risk, then you might as well just guess a runtime, take a paint program and just draw a curve that you feel looks right, and dive it.
(2) It's conspicuous how these uncalibrated and untested models were and still are pushed commercially with dive planning software and licensing to dive computer vendors. They promote an unhealthy habit of deep stopping among technical divers.

Not completely true.... RGBM is calibrated against LANL database of dives with known outcome. You can read it in BRW papers. Corelation paper show how relate other models to LANL database.

 

[shoredivr]

There is a strong signal in the available data that over-emphasising deep stops (which almost certainly includes the level of “deep stopping” prescribed by bubble models) is disadvantageous. I am aware (through attending presentations and collegial discussions) of two further studies involving tech diving-relevant profiles with differing emphasis on deep stops that are being prepared for publication. These are not my studies and I will say nothing further about them, but Ross will find them “interesting”.

Simon M

Thank you for taking the time to reply. These new studies should be interesting, and as someone who does tech diving, keeping up with actual research is important.