Bühlmann Werte im Dekoalgorithmus

[Rob]

Hallo,

ich habe mal eine Frage an die/den Entwickler des Dekoalgorithmus.
Warum werden für die Stickstoff-Halbwertzeiten für die Kompartimente
3,4,6 und 7 und entsprechend die Werte für e2secs, e1min und e10min,
von schlauen-ää blauen Buch (Bühlmann) abweichende Werte angegeben,
während beim Helium genau die von Bühlmann angegebenen Werte verwendet werden.

Danke,
Viele Grüße
Robert

Hello,
i have a Question to the developer of the decompression algorithm.

Why do you use different values for nitrogen-halftimes for the tissues
3,4,6 and 7 and accordingly as values for e2secs, e1min and e10min,
than printed in the blue book (Buehlmann) while for helium,
exacly the Buehlmann values are used.

Thanks,
best regards
Robert

[JeanDo]

Hallo Rob,

Her Bühlmann published several sets of coefficients. Editions 1990, 1995 and 2002 propose different coefficients. And for each one have three versions for nitrogen coefficients (theoretic, optimized for tables, and optimized for dive computers).
Helium history is much simpler. Probably because there is far less data available, and Bühlmann did'nt have time to optimize further the model.

OSTC Model used is 2002 edition, ZH-L16C, option 1a.

Hope this helps,

[Rob]

Hallo JeanDo

>>OSTC Model used is 2002 edition, ZH-L16C, option 1a.

Thats why i ask. The OSTC Model is NOT using these Values for N2!
In My book Buehlmann Tauchmedizin 5. Auflage, Page 158 is the t1/2 N2 time in minutes for Kompartiment 3 12,5 for Komp. 4 18,5 Komp. 6 38,3 and Komp. 7 54,3
OSTC is using 12, 18, 39 and 55 the values for e2secs e1min and e10min are calculated with the rounded OSTC values.

For helium you are using the original Buehlmann values.
The point is that you should use the same base for the halftime values for n2 and He. The same means that the He values in Buehlmann are the n2 halftimevalues divided by 2.65. (Ok, the 2,65 can be discussed but Buehlmann uses this Value so it ist Ok).

My Question was, why do you use not the original Values?

Best regards
robert

[dmainou]

Rob Wrote:
-------------------------------------------------------
> Hallo JeanDo
>
> >>OSTC Model used is 2002 edition, ZH-L16C, option
> 1a.
>
> Thats why i ask. The OSTC Model is NOT using these
> Values for N2!
> In My book Buehlmann Tauchmedizin 5. Auflage, Page
> 158 is the t1/2 N2 time in minutes for
> Kompartiment 3 12,5 for Komp. 4 18,5 Komp. 6 38,3
> and Komp. 7 54,3
> OSTC is using 12, 18, 39 and 55 the values for
> e2secs e1min and e10min are calculated with the
> rounded OSTC values.
>
> For helium you are using the original Buehlmann
> values.
> The point is that you should use the same base for
> the halftime values for n2 and He. The same means
> that the He values in Buehlmann are the n2
> halftimevalues divided by 2.65. (Ok, the 2,65 can
> be discussed but Buehlmann uses this Value so it
> ist Ok).
>
> My Question was, why do you use not the original
> Values?
>
> Best regards
> robert

Because they are more aggressive... The later ones better fit the risk incidence. I think set C is the one deemed suitable for dive computers.

Read "Understanding M-values" from Eric Baker all coefficients are there.

[Rob]

Hi dmainou,

you dont understand my question.

I know this reading and i know the Buehlmann algotithm.

To be clearly.

OSTC is NOT using ZHL16C values for N2 t 1/2 for Tissue 3, 4, 6 and 7!

My question is, why.

regards
Rob

[JeanDo]

Hello Rob,

Yes, you are right.

I guess for historical reasons, the values where rounded at some point. Useless now they are stored in full floating-point resolution...

--> I corrected the values for the next 1.91 beta release.

Actually, that make minor (1') changes in deep runtimes.

Thanks for the feedback !