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ZH-L 12 : Validation of an old (1982) experimental Heliox jump dive (30 m, 120 min)

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ZH-L12: Validation of an old (1982) experimental Heliox jump dive (30 m, 120 min): Question: could we verify the old ZH-L12 decompression profile with a topical desktop deco software?
Validation of an old (1982)
experimental Heliox jump dive
(30 m, 120 min)
Could we verify the
old ZH-L12
decompression profile
from [4], p. 35
with a topical desktop
deco software?
[4], p. 35
Bühlmann, A.A. (1983): Dekompression - Dekompressionskrankheit,
Springer, ISBN: 3-540-12514-0
Desktop Deco Software:
DIVE Version 3
What is the ZH-L12?
[4], p. 27
The ZH-L12 is the 1983-precursor of the ZH-L 16 decompression algorithms,
used for decompression models of parallel perfused compartments.
ZH = Zuerich / Zürich, capital of Switzerland,
place of the DKL-USZ, the Hyperbaric Chamber Laboratory,
University Hospital Zürich; Albert Alois Bühlmann worked there.
L = linear; the allowed/tolerated inertgas supersaturations per
compartment are simple linear equations.
12 = is not the # of compartments,
instead it is the # of coeffcient pairs for both N2 AND Helium,
pls. cf. next slide:
The ZH-L12:
[4], p. 27
The Profile:
p. 35
The Profile BB-120:
[4], p. 35, enlarged:
The Profile:
[4], p. 20, Table 7
Dive series BB-120 (bottom gas = decompression gas = Heliox21/78)
A: TTS 316 min, deepest stage 15 m (*),
0 cases of DCS, 20 man-dives;
B: TTS 232 min, 3 cases of DCS in 8 man-dives
TTS = time-to-surface,
i.e.: sum of all stop times + (bottom depth / ascent rate)
(*) which is not completely
in-line with the profile from p.35, where the y-axis (pressure in [Bar])
does not really match properly to best-practice.
The Profile:
[4], p. 35:
Dive series BB-120 A , TTS 316 min,
there a graphical manual analysis
of the plotted profile would yield ca.:
Stage [m] run-time [min] stop time [min]
15 0 12 12
12 12 33 21
10 33 57 24
7,5 57 92 35
6 92 142 50
4 142 203 61
2 203 316 113
TTS: 316 min
Result for BB-120 A:
The 1st. stage with 15 m, the stop time of 12 min AND the TTS
aligns perfectly with [4] , but the rest of the stop times per stage are
redistributed due to the somewhat non-standard deco depths.
(*) TTS = time-to-surface,
i.e.: sum of all stop times + (bottom depth / ascent rate)
DIVE Version3
The Profile:
[4], p. 20, Table 7
Dive series BO-120 (bottom gas = Heliox21/78)
(decompression gas = 100 %O2)
A: TTS 83 min, deepest stage 15 m,
0 cases of DCS, 12 man-dives;
B: TTS 65 min, 3 cases of DCS in 8 man-dives
TTS = time-to-surface,
i.e.: sum of all stop times + (bottom depth / ascent rate)
The Profile:
[4], p. 35:
Dive series BO-120 A , TTS 83 min,
there a graphical manual analysis
of the plotted profile would yield ca.:
Stage [m] run-time [min] stop time [min]
15 0 10 10 (2 * 5)
12 10 25 15 (3 * 5)
9 25 40 15 (3 * 5)
6 40 70 30 (6 * 5)
3 70 83 13
TTS: 83 min
Result for BO-120 A:
The 1st. stage with 15 m, the # of stages AND the TTS of 83 min aligns
perfectly with [4]; but the modulo 5 structure resembles very much the old
DRÄGER tables and does not have a physiologic background, but it reveals
clearly „excecutive editing“ of the profile in order to gain insight into the half-
times and tolerated overpressures of some compartments, pls. cf. the
rightmost entries on Tab. 7 !
(*) TTS = time-to-surface, i.e.: sum of all stop times + (bottom depth / ascent rate)
DIVE Version3
back up material:
Next question
Could we make a
serious PoC for
DIVE Version 3_09?
DIVE V 3_09 (
and the manual are in german
The release train for the english version (V3_04) is somewhat slower
Input via keyboard fro BB-120 A:
m“, „.21“, „.78
(adaption of the breathing mix Heliox21 with 1% N2
nc“, „8
(loading the 1983 ZH-L12 N2 Matrix)
hc“, „2
(loading the 1983 ZH-L12 Helium Matrix)
d“, „30.“, „120.
(d like „dive“, the above dive to 30 m & 120 min)
(a like „ascentyields the output of the deco prognosis)
Handling of DIVE:
Input via keyboard fro BO-120 A:
m“, „.21“, „.78
nc“, „8
hc“, „2
d“, „30.“, „120.
„a“, „15.“
(ascent to the first stop @ 15 m)
„m“, „1.0“, „0.“, „0.“ „a“ (yields prognosis)
(decompression gas 100 % O2)
Handling of DIVE:
Fine tuning could be done via the commands:
ascent rate („AR“)
ambient atmospheric pressure at start („L“)
the respiratory coefficient („R“)
the ambient (water)-temperature („te“)
the water density („di“)
And with:
we recieve the complete decompression prognosis;
i.e.: the stop times per stage from 15 to 3 m
and the responsible leading compartment.
The latest DIVE Version for beta testing is always staged there:
along with information on date, size, features and the checksums
for verifying the download.
Handling of DIVE:
Synopsis: PoC of DIVE!
A PoC is a proof of concept, here confirmed for the DIVE decompression
suite Version 3_09 AND the ZH-L12 system from 1983. Even if the methods
match perfectly, this does not imply that both are correct or that the methods
could be extrapolated to longer / deeper dives! It could just reveal that, for
e.g., we in this club did make the same errors! Or different errors which yield
by accident the same outcome!
The deco profile itself is not taken for granted, just because of the # of
uneventful dives, here for BB-120 A it was only n = 20, but:
n > = 185 (sic!) is needed for a serious statistical analysis with a high
selectivity, that is: Power >= 0,85.
Synopsis: PoC of DIVE!
A dive contractor would have handled the dive completely different
(please cf. the last 3 slides at the end of this presentation)!
Especially due to the workload and water temperature and the often
missing immersion: most of these experimental Zuerich dives have been
done without substantial workload in a (warm) deco chamber!
In [4], on p. 20 & 21 we find:
„28 to 30° C“ and „10 min per 1h with 80 Watt“.
Synopsis: PoC of DIVE!
However, a detailed analysis of [4], p. 22 & 23, the „Abb. 4 & 5“ reveals:
the used compartments with half-times of:
Helium: 173 & 205 [min]
N2: 458 & 542 [min]
do not match the published coefficients matrix on p. 27, instead:
by a sudden there are appearing 2 „newcompartments:
i.e.: 173 / 458 min „betweencompartments # 14 & 15
and: 205 / 542 min „betweencompartments # 15 & 16
the indicated FN2 und thus the
calculated inertgas overpressures (p i.g.t) can not be substantiated!
Synopsis: PoC of DIVE!
And, interestingly enough, the
DCIEM Diving Manual (1992) (*) table yields no comparable profile,
Heliox starts @ 36 m , bottom time max: 100 min, TTS = 152 min
NDTT 5. ed. (2019) (*) no heliox at all
DCIEM: Defence and Civil Institute of Environmental Medicine,
the manual could be downloaded for free there:
NDTT: Norwegian Diving- and Treatment Tables, the manual
could be downloaded for free there:
Synopsis: PoC of DIVE!
the new USN table
yields a TTS = 104 min (p. 12-32):
Synopsis: PoC of DIVE!
the MNT 92, Version 2012
yields a TTS = 117 min:
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