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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Historical Reference: slide # 12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

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.

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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:

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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