On one Heliox Jump dive

Abstract

During our evaluation of some ZH-L16x Helium coefficients [1], we found certain interesting aspects on how dive computers calculate a box dive profile with Heliox21 mixture as the sole breathing gas and how diving contractors would handle the same profile in a completely different way. One keyparameter for our comparison was the K-Value index for CNS-OT [2].

Full text

1
On one Heliox Jump dive
25.08.2022
Miri Rosenblat, TAU
Nurit Vered, Technion Haifa
Yael Eisenstein & Albi Salm,
SubMarineConsulting
DOI:

2
On one HELIOX jump dive
Abstract:
During our evaluation of some ZH-L16x Helium coefficients [1], we found
certain interesting aspects on how dive computers calculate a box dive profile
with Heliox21 mixture as the sole breathing gas and how diving contractors
would handle the same profile in a completely different way. One
keyparameter for our comparison was the K-Value index for CNS-OT [2].
Introduction: slides # 3 & 4
Methods: slide # 5
Data: slides # 6  11
Historical Reference: slide # 12
Results: slide # 13
Discussion & Conclusion: slide # 14
References: slide # 15

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On one HELIOX jump dive
Introduction (1):
In [1] we evaluated diver carried computers (dive computers) with a box
profile of 42 m bottom depth and 25 min bottom time; as a sole breathing gas
we choose Heliox21 (i.e. 21 % O2, 79 % Helium) due to the same inertgas
content as regular, compressed breathing air: thus different methods of
calculating decompression times and / or modified Helium-coefficients
are unveiled across the various products very quickly.
But in most commercial decompression tables, the tables entries for the
bottom time @ 42 m are either 20 or 30 min with normally Heliox16, thus
we compiled a list of the various run-times across the used tables with just
these parameters. As the diving-methods and decompression algorithms
across these tables are at maximal variance, we decided to evaluate the TTS
(the time-to-surface) along with the K-Index for the CNS-OT, the K-severity
index for the oxygen toxcicity for the central nervous system ([2] and all the
references therein) as the two parameters of choice for our comparison.

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On one HELIOX jump dive
Introduction (2):
We compared 6 well-known, proven and world-wide respected tables.
In alphabetical order these were the:
 DCIEM 1992
 Diving Contractor Table (10/1996)
MNT 2013
(NEDU Report 1-65)
 USN 1999
USN 2018

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On one HELIOX jump dive
Methods:
The tables entries were directly compared along the screen shots from
the tables in question, pls. cf. the DATA section.
The CNS-OT K-Value was evaluated with DIVE along the diving profiles
from these tables [2].
The thus resulting K-Value is tabulated in Table I, slide # 13
in the order of increasing TTS.
The reduction of the K-Values during the recovery phases with
air breaks was not considered.

6
On one HELIOX jump dive
DCIEM Diving Manual: Table 7 , p. 2B-9 from:
DCIEM No. 92-50 (1992) Part 2 Helium-Oxygen Surface-Supplied
Decompression Procedures and Tables;
Defence and Civil Institute of Environmental Medicine, North York, Ontario,
Canada

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On one HELIOX jump dive
Diving Contractor Table (10/1996) Heliox 16  Heliox 20
p. 5, 140 feet = 42.67 m

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On one HELIOX jump dive
MT 92 / MNT 2013: 24. May 2019, p. 62

9
On one HELIOX jump dive
MT 92 / MNT 2013: 24. May 2019, p. 145

10
On one HELIOX jump dive
U.S. Navy Diving Manual, FM 20 -11, 20.01.1999
Volume 3, Chapter 14, Table 14-7, p. 14 - 31
140 feet = 42.67 m

11
On one HELIOX jump dive
U.S. Navy Diving Manual, Revision 7, Change A, 30. April 2018
Volume 3, Table 12-4, p. 643
140 feet = 42.67 m

12
On one HELIOX jump dive
As a historical point of reference serves the U.S. Navy Table with Heliox32
140 feet = 42.67 m, as there is no 30 min. entry (400 test dives, no DCS)
Source: Workman, R.D. & Reynolds, J. L. (1965), NEDU Report 1-65

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On one HELIOX jump dive
Table I: Synopsis of all table entries with CNS-OT K-Value & TTS
Stage /
Method: 21 m 18 m 15 m 12 m 9 m 6 m 3
m CNS-OT K Index
(without Recovery @
Air Breaks)
TTS Rem.:
(*): 100 % O2
[min.] [min.]
MNT 2013 3 5 5 15
(*) - 43,712 31 Heliox 28 - 30
MNT 2013 3
(Air) 3
(Air) 5
(Air) 10
(*) 15
(*)
+ 5
10
(*) - 123,583 53 Heliox 17-18; incl.
1 * Air Break 5’
DCIEM 1992 2
(Air) 4
(Air) 4
(Air) 37
(*) - - 114,798 55 In-Water decompression
U.S.N. 1999 10
(*) 45
(*) - - - 777,671 58 140 feet
U.S.N. 2018 H50:
10 H50:
10 18
(*) 30
(*) - 125,819 82 140 feet, incl.
2 * Air Breaks,
each 5 min
Diving
Contractor
Table
10/1996
10
(EAN
50)
9
(*) 8
(*) 25
(*) 799,837 83 Incl. 3 Air Breaks @ 5
min.,
+ 10 min slow bleed
to surface
Results for 42 m / 30 min, Heliox, sea water:

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On one HELIOX jump dive
The parameters on the efficiency of a certain run-time
are, besides the security record, i.e. the
# of documented DCS cases
complexity & cost, i.e. # of used breathing gases
TTS (time-to-surface), sum of all stop times + (bottom depth / ascent
speed)
a CNS-OT index, i.e. the risk of an CNS-oxygen toxicity convulsion
As the pO2 here is usually > 1.6 atm, the NOAA guidelines can not be used;
in particular there is no defined procedure for NOAA CNS-doses > 100 %.
Instead, the K-Value algorithm offers a suitable measure for high pO2 and
long exposures. Especially useful is the mapping of the K-Value to the risk of
contracting a CNS-OT convulsion ([2] and all the references therein).
Furthermore, tables/procedures/divecomputers, esp. in the so-called „TEC“
domain, should replace the NOAA / OTU calculations with the K-Value.
Discussion & Conclusion:

15
References:
[1] Miri Rosenblat, TAU; Nurit Vered, Technion Haifa; Yael
Eisenstein & Albi Salm, SubMarineConsulting (16.08.2022)
On the arbitrariness of the ZH-L Helium coefficients
DOI: 10.13140/RG.2.2.19048.55040
[2] Salm, A; Rosenblat, M;
An agile implementation of the "K-Value" severity index for cns- and
pulmonary oxygen toxicity (CNS-OT & P-OT)
DOI: 10.13140/RG.2.2.17583.87205