Increased conservatism?

[Dr Simon Mitchell]

From MultiDeco and the supersaturation graphing, you can see how the DAN testing arrived at its results.

Ross,

DAN arrived at its results through empirical testing [1] - not modelling of tissue supersaturation.

Moreover, depending on which table you use, the dive you have cited is either a single no-decompression dive and DAN would recommend a pre-flight surface interval of at least 12 hours, or it is a decompression dive in which case DAN would recommend a surface interval "substantially longer than 18 hours". So, the confluence you imply between DAN recommendations and your predictions based on multideco is more imagined than real.

The Time to Fly formula is sometimes made from those features - The time to get initial SS to 0 (3 hours) + the 16 hours time to reduce SS back to 0 again if you had entered the plane - for this dive about 19 hours.

Can you cite exactly which "time to fly formula" is "made from those features" you describe. Which organisation? Published by who?

I want to be clear that I think multideco is a good tool, and I have purchased it myself. However, you are promoting it here for a purpose it was not designed for, where the validity of the application is very uncertain.

Simon M

1. Vann RD, Gerth WA, Denoble PJ, Pieper CF, Thalmann ED. Experimental trials to assess the risks of decompression sickness in flying after diving. Undersea Hyperb Med 2004;31(4):431-444.

 

[rossh]

Ross,

DAN arrived at its results through empirical testing [1] - not modelling of tissue supersaturation.

Yes, It is nice to see that the current modelling aligns so well with the practical testing.


The example I showed was just one little dive that was on the edge of NDL. A series of typical one day NDL dives can get surface time SuperSaturation up to 6 or 8 hours. A deco dive will start with 10 hours or more surface SS time. Then add the 12 to 18 hours of airplane ride induced SS.

From that one can see how the minimum 24 hour TTF limit was derived. I will leave that as an exercise for the reader to verify.

Can you cite exactly which "time to fly formula" is "made from those features" you describe. Which organisation? Published by who?
Simon M

No, The computer makers do not publish the formula they use. They keep that info to themselves.

But its pretty easy to figure out the basis of the formula, and how it aligns with SS values. The old round Suunto used a formula that was minimum 12 hours + all the accumulated surface SS times - that just comes from observations.

More recently most computers have been extended to the 24 hour minimum, plus some amount of actual SS time. With a little experimenting with MultiDeco, one can see how the SS values are intrinsic to the times from dive computers.

I want to be clear that I think multideco is a good tool, and I have purchased it myself. However, you are promoting it here for a purpose it was not designed for, where the validity of the application is very uncertain.

Simon M

People who actually use MultiDeco, will see it already has this inbuilt warning.

.

 

[Dr Simon Mitchell]

Ross,

I find this line of posting quite confusing. You have come onto thread where I have been having a conversation with Brac about the merits of planning surface intervals before flying using tissue gas calculations versus the empirically derived limits promulgated by DAN. Your first post appears to be supportive of planning these intervals using tissue gas calculations provided by your software. But then after being challenged you reveal that there is a strongly worded warning in your software not to plan pre-flight surface intervals in this way. Why didn't you state this clearly in your first post? Or were you going to let people find this out for themselves after buying it?

Just to pick up on some of your other points (although they are kind of moot now that you have revealed the warning).

Yes, It is nice to see that the current modelling aligns so well with the practical testing.

But as I pointed out it doesn't. At least not for the dive you have chosen.

The example I showed was just one little dive that was on the edge of NDL. A series of typical one day NDL dives can get surface time SuperSaturation up to 6 or 8 hours. A deco dive will start with 10 hours or more surface SS time. Then add the 12 to 18 hours of airplane ride induced SS.

Where in this paradigm does your approach account for bubbles formed after the first dive?

And a related question:

If it can all be done using tissue gas modelling as you are / were (I'm not sure now because of your warning) implying, why did the DAN team that included some of the world's most expert decompression modellers (Vann and Gerth) go to the trouble of performing an 800 man dive / altitude exposure experiment to derive their limits?

No, The computer makers do not publish the formula they use. They keep that info to themselves.

OK, so your statement....

The Time to Fly formula is sometimes made from those features...

....was just speculation.

People who actually use MultiDeco, will see it already has this inbuilt warning.

View attachment 420315

Good. Appropriate. And clearly you are not as confident about the ability to predict safe preflight surface intervals using tissue gas calculations in multideco as you initially appeared to be.

Simon M.

 

[rossh]

Ross,

I find this line of posting quite confusing. You have come onto thread where I have been having a conversation with Brac about the merits of planning surface intervals before flying using tissue gas calculations versus the empirically derived limits promulgated by DAN. Your first post appears to be supportive of planning these intervals using tissue gas calculations provided by your software. But then after being challenged you reveal that there is a strongly worded warning in your software not to plan pre-flight surface intervals in this way. Why didn't you state this clearly in your first post? Or were you going to let people find this out for themselves after buying it?

Just to pick up on some of your other points (although they are kind of moot now that you have revealed the warning).



But as I pointed out it doesn't. At least not for the dive you have chosen.



Where in this paradigm does your approach account for bubbles formed after the first dive?

And a related question:

If it can all be done using tissue gas modelling as you are / were (I'm not sure now because of your warning) implying, why did the DAN team that included some of the world's most expert decompression modellers (Vann and Gerth) go to the trouble of performing an 800 man dive / altitude exposure experiment to derive their limits?



OK, so your statement....



....was just speculation.



Good. Appropriate. And clearly you are not as confident about the ability to predict safe preflight surface intervals using tissue gas calculations in Multideco as you initially appeared to be.

Simon M.

MultiDeco provides tools to show how Supersaturation is encountered, both during the dive and afterward, using the current industry scientific formula. The fact that SS observations aligns well with the practical testing for pre-flight time, is a bonus.


MultiDeco doesn't plan anything to do with flight. There are no TTF numbers anywhere in any of our programs. There is no approved formula for this - only recommendations from DAN and similar.

MultiDeco is a dive planner. If you actually did some dive planning with the program, you would see that.


The SS add Flight time option simply demonstrates how divers really do need that extra surface interval. I added this feature to head off the DIR crowd, who at the time, thought they could avoid all the pre-flight surface interval, which is clearly wrong.



***********

I'm adding useful background information to the discussion, and you are trying to bury it.

Why are you again using ad hominem, and deliberate miss interpretations of my posts and programs.

.

 

[Rich Keller]

Anyone else taking a slower route?

I would consider this a safer route not a slower route. I have been deeper and stayed longer then most divers you will ever meet but that was for work. When I dive for recreation it is usually shallow and long. I am not diving to expand or enhance my skills, I am there to relax and enjoy. I use a minimum of equipment and that equipment is usually the simplest type available that I can field strip and repair myself if needed. What you consider advancing and pushing new limits just looks like more work to me and I am only there to relax.