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3
Abstract (1):
The DCIEM Heliox diving tables [2] are wide-spread in
professional use [1] and considered conservative due to a low
rate of DCS ([1] & [2] and all the references therein).
Their counterpart tables from the United States Navy (USN), the so-called
surface-supplied Heliox (He-O2) tables have had a long history: the first
version from Momsen et al. appeared in 1939 with heavy field-tests along the
epic rescue & salvage efforts for the U.S.S. SS-192, the submarine
„SQUALUS“ [3]. The latest empirical changes resulted in Revision 4, Change
A (1-March-2001) and have been tested successfully with ca. 140 dives on
the USS MONITOR ([12] for SAT dives, but all the other references therein).
However, in the topical, more than 5 years-effort and 232 skilfully designed
and successfully completed man-dives, NEDU revised these USN surface-
supplied Heliox tables again and proposed a candidate replacement table,
the:
„Twenty-First Century Surface-Supplied Heliox Decompression Table”.
4
Abstract (2):
This table was designed with a statistical probability of contracting a
decompression sickness [P(DCS)] of less than ca. 2.3 % ([4], [5], [6] and all
the references therein).
We selected three Heliox diving schedules as primary, first dives on the day,
and compared the new „Twenty-first century surface-supplied Heliox
decompresson tables“ from USN / NEDU (ss He-O2), which have been
designated as the “final candidate replacement” [4], pp. B-2, where
operationally possible, with the DCIEM tables.
Thereafter we tried to map these schedules on a seasoned perfusion model
(ZH-L16) and recompute them with and without a pair of simple gradient
factors [8].
The benchmarked parameters have been the TTS with and without air breaks
and the K-values [9].
5
Methods (1):
We selected only three profiles as our show cases:
Profile 1: 30 m / 120 min
Profile 2: 170 fswg / 60 min
Profile 3: 230 fswg / 40 min.
Profile 1 is the historical Heliox-jump dive of 1982, tested by Albert Alois
Bühlmann with 12 man-dives and no cases of DCS [7].
The profiles 2 & 3 from the printed DCIEM tables [2] with a Heliox16/84 match
the range of the allowed oxygen-contents in the candidate replacement ss-
HeO2 tables [4] & [5]. However, the decompression staging and the gas-
mixes for the deepest and intermediate stops are different: for DCIEM it is Air,
for NEDU it is the bottom-mix or/and EAN50.
As both tables / methods exploit 30 & 20 feet stops on oxygen, the
K-value [9] is a benchmark parameter besides the raw TTS;
(the TTS = time-to-surface, defined as:
sum of all stop times + (bottom depth / ascent speed ) [+ air breaks] )
7
Methods (3):
The DIVE framework [10] has been used two-fold
for this benchmark:
➔as a pure number-cruncher
to calculate the K-values (and others) by running
the unmodified, printed schedules,
pls. cf. the log-files in the DATA section;
➔as a benchmark partner with a ZH-L16-type of perfusion model
with or without gradient factors (GF).
The profile-simulations with DIVE have had used the following parameters:
➔water density as per slide # 6
➔ascent speed 9.3 m / min
➔Bühlmann Safety Factor
➔breathing gas mixes:
➔bottom mix Heliox 16/84
➔deepest & intermediate stops: Air
➔9 & 6 m: „pure“ Oxygen.
8
Methods (4):
As the unmodified ZH-L16C system for N2, and, as well
the ZH-L16A coefficients for Helium decompression, are
usually lacking a certain conservativism in comparison to DCIEM and even
the seasoned USN procedures [11], we used then throughout the following
gradient factor system (GF):
➔GF High = GF Low = 0.9
If a 1st. deep stop appeared 3 m deeper than the deepest stop without a GF,
then this stop time was added to the stop-time, where the gas-switch from
bottom mix to Air / EAN50 took place.
The change from bottom mix to air/EAN50 was simulated after the ascent to
the deepest stop, the change from air to oxygen was simulated after the end
of the 12 m stop.
Then the TTS for the 9 & 6 m stops has been calculated with fO2 = 0.9,
balance N2, but the stops themselves have been simulated with fO2 = 1.0
for the assessment of the K-values and to achieve a maximum
comparability with the methods used for the 21st. century tables.
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Results (3) for Profile 3:
Table / Profile:
Deepest
Stop
K
-value
[./.]
TTS
[min]
Air
Breaks
TDT
[min]
DCIEM
230
ft / 40 min
(
Heliox, Air, O2)
120 fsw 977,993 152 + 5 3 x 170
NEDU
230
fswg / 40 min
(
Heliox, EAN50, O2)
90 fswg 1,301,322 199 + 7 5 x
206 +
25
DIVE 3_11
GF .9 / .9
70.62 m / 40 min
(
Heliox, Air, O2)
(42) 39 m 387,757 158 + 8 4 x
166 +
20
DIVE 3_11
GF .8 / .8
70.62 m / 40 min
(
Heliox, EAN50, O2)
39 m 682,452 156 + 8 4 x
164 +
20
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Discussion & Conclusion:
The divergent philosophies / algorithms between
the NEDU / USN, DCIEM and ZH-L16 are already described
at great length elsewhere.
What stays here to ascertain are the relative similarities
in the TTS despite the differences in staging and decompression-mixes
and thus the K-values.
As well there is comforting serendipity that the run-times from the ZH-L16 C
with a GF 0.9 resp. 0.8 do not vary by much, if we concede the inaccuracies
of dive-computers/depth-gauges/oxygen-analyzers and the time-delays in
following a run-time through communication with top-side!
So there is hope for a bright future of the new
“21st. century ss He-O2” tables!!!
(*) וה-קומע םי הי
(*) hebrew for:
Hoo-Yah Deep Sea
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References (1):
[1] DCIEM Diving Manual, DCIEM No. 86-R-35: Part 1 AIR Diving Tables and
Procedures, Defence and Civil Institute of Environmental Medicine, Canada,
March 1992
[2] DCIEM Diving Manual, DCIEM No. 92-50: Part 2 Helium-Oxygen Surface-
Suppplied Decompression Procedures and Tables; Defence and Civil Institute
of Environmental Medicine, Canada, October 1992
[3] Rosenblat, Miri & Vered, Nurit. (2022). The diving medical detectives:
when diving medicine books are completely wrong; Part IV: Synopsis.
10.13140/RG.2.2.12077.97760.
https://dx.doi.org/10.13140/RG.2.2.12077.97760
[4] Wayne A. Gerth; F. Gregory Murphy; David J. Doolette
Twenty-First Century Surface-Supplied Heliox Decompression Table
Development, NEDU TR 23-11
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References (2):
[5] David M. Sherrier, Wayne A. Gerth; David J, Doolette; F. Gregory Murphy
Man-Trial of the Twenty-First Century Surface-Supplied Heliox (He-O2)
Decompression Table, NEDU TR 23-37
[6] Wayne A. Gerth, David J. Doolette
VVal-79 Thalmann Algorithm Metric and Imperial Air Decompression Tables
NEDU TR 16-05
[7] Salm, Albi. (2020). ZH-L 12 : Validation of an old (1982)
experimental Heliox jump dive (30 m, 120 min).
10.13140/RG.2.2.24608.20482/1.
DOI: https://dx.doi.org/10.13140/RG.2.2.24608.20482/1
[8] Salm, Albi & Vered, Nurit & Rosenblat, Miri. (2023).
Gradient Factors: on the rise? 10.13140/RG.2.2.20301.20963.
DOI: https://dx.doi.org/10.13140/RG.2.2.20301.20963
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References (3):
[9] Vered, Nurit & Rosenblat, Miri & Salm, Albi. (2021).
An agile implementation of the "K-value": a severity index for CNS-and
pulmonary oxygen-toxicity. 10.13140/RG.2.2.17583.87205.
https://dx.doi.org/10.13140/RG.2.2.17583.87205
[10] Rosenblat, Miri & Vered, Nurit. (2021).
Synopsis & Fact Sheet: update per 11/2021 for DIVE Version 3_11.
10.13140/RG.2.2.17024.56326.
https://dx.doi.org/10.13140/RG.2.2.17024.56326
[11] Rosenblat, Miri & Vered, Nurit & Salm, Albi. (2024).
Emulation of selected DCIEM Heliox schedules via a
decompression shareware. 10.13140/RG.2.2.21830.04161.
https://dx.doi.org/10.13140/RG.2.2.21830.04161
[12] Rosenblat, Miri & Vered, Nurit & Salm, Albi. (2023). On the "USS
MONITOR" saturation dives. 10.13140/RG.2.2.26284.74887.
https://dx.doi.org/10.13140/RG.2.2.26284.74887