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Adaption of a COMEX procedure for recreational bounce dives on air

Authors:
  • Independent Researcher

Abstract

Adaption of a COMEX procedure for recreational bounce dives on air: a COMEX decompression procedure, once developped for deep experimental and saturation dives with Heliox is adapted for the use in the deep diving range for recreational & technical bounce dives on regular breathing air. As well a comparison is done between different staging protocols and decompression procedures, for. eg. from the United States Navy and the Buehlmann SAT tables.
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Adaption of a
COMEX procedure for
recreational bounce dives
on air
DOI: 10.13140/RG.2.2.: t.b.d.!
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Info COMEX:
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Info COMEX:
Compagnie maritime d'expertises:
C&R and SAT dives;
and deep diving experiments:
for e.g.: 1992, Hydra-X, 701 m
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Info COMEX:
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COMEX procedure
simple procedure:
without any compartments or half-times
without supersaturations
only one free parameter (λ)
„Best Fit“ to many successful C&R and SAT dives,
and a lot of deep diving experiments,
for e.g.: Hydra series, up to 700 m,
data base: pls. cf. next slide
Legend:
SAT : saturation dives, dive time > 72 h
C&R : construction & repair diving
Sources: [1], [2] & COMEX homepage
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COMEX data base
# days # divers
# man dives
The data base of the COMEX
commercial SAT dives
and the deep diving experiments from
1967 until 1999:
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The COMEX procedure
The COMEX procedure:
D0
D(t) = ------------------------------------
1 + λ * T-5/2 * D0-3 * (t T)
with the following parameters:
D(t) : (actual) diving depth [m] as a function of diving time t, t > T
T : bottom time [min]
D0 : bottom depth [m]
λ : empirical parameter [min2m3], used to fit for:
breathing mix, Helium- and Oxygen fraction
water- / ambient temperature
workload
decompression chamber- or working dive (with immersion)
Sources: [1], [2]; pls. cf. slide #20
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The COMEX procedure
y axis: actual diving depth D(t)
x axis: diving time t, after bottom time T, i.e.: t > T
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The COMEX procedure
Due to the technical nature of SAT dives &
the deep diving experiments, there is headspace
in the decompression procedures. There are
different values for the parameters for:
workload of divers
Helium fraction
pO2 @ bottom, @ decompression
ambient temperature, …
risk appetite of the company
In the COMEX procedure this is reflected via the parameter λ.
As an example pls. cf. the next slides: decompression from
a SAT dive in the AQUARIUS habitat (Florida, 18 m):
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Decompression from the AQUARIUS habitat
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Decompression from the AQUARIUS habitat
USN SAT procedure: 1140 min: 4 h + 15 h = 19 h (Air only)
Bühlmann SAT 20: 660 min: 11 h (with 6 h @ 100% O2)
Aquarius procedure: 990 min: 16,5 h (with 1 h @ 100 % O2 @ 60 feet)
COMEX procedure: 1190 min: 19,8 h (Air only) with λ = 999.990.000.000
DIVE V 3_09: 1860 min (upper limit of ascent rate)
2700 min (lower limit of ascent rate, AIR only)
DIVE V 3_09: 1600 min (upper limit of ascent rate, from 10 m @ 100 % O2)
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Decompression from the AQUARIUS habitat
USN SAT procedure: 1140 min: 4 h + 15 h = 19 h (Air only)
Bühlmann SAT 20: 660 min: 11 h (with 6 h @ 100% O2)
Aquarius procedure: 990 min: 16,5 h (with 1 h @ 100 % O2 @ 60 feet)
COMEX procedure: 1190 min: 19,8 h (Air only) with λ = 999.990.000.000
DIVE V 3_09: 1860 min (upper limit of ascent rate)
2700 min (lower limit of ascent rate, AIR only)
DIVE V 3_09: 1600 min (upper limit of ascent rate, from 10 m @ 100 % O2)
Legend:
USN: SAT procedure per USN Diving Manual, Rev. 7 2018,
Chapter 13, Table 13 9:
Bühlmann SAT 20: table from the DKL-USZ, pls. cf. next slide
Aquarius: proprietary procedure in the habitat, which rests on the
sea bed, after decompression the divers ascend to the surface
COMEX: procedure with λ= 9.999 exp 11
13
Decompression from the AQUARIUS habitat
USN SAT procedure: 1140 min: 4 h + 15 h = 19 h (Air only)
Bühlmann SAT 20: 660 min: 11 h (with 6 h @ 100% O2)
Aquarius procedure: 990 min: 16,5 h (with 1 h @ 100 % O2 @ 60 feet)
COMEX procedure: 1190 min: 19,8 h (Air only) with λ = 999.990.000.000
DIVE V 3_09: 1860 min (upper limit of ascent rate)
2700 min (lower limit of ascent rate, AIR only)
DIVE V 3_09: 1600 min (upper limit of ascent rate, from 10 m @ 100 % O2)
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The COMEX procedure
The formula describes the diving depth D(t)
in relation to the diving time t, after bottom time T.
As there are no PTC/bells available for rec/TEC dives, a continuous
ascent is technically not feasible: decompression is done in stages,
usually 10 feet / 3 m apart. The stop times are listed with each stage.
Thus for a rec/TEC bounce dive, the times from the COMEX procedure
have to be integrated (summed up) around a median, i.e.: (N * 3) +/- Δ.
Example with Δ = 1.5 m for a 6 m stop (N = 2):
the integration in the time-domain for this 6 m stop is then done from
6 + 1.5 = 7.5 6 1.5 = 4.5 m
This rationale is feasible for deep rec/deep TEC dives, usually much
like a box profile due to limited supply of breathing gas & thermal
protection:
if it fits to SAT diving, it fits even more so to bounce dives, since the
more sensitive body tissues are not affected by short bounce dives.
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the test dive: D0 = 42 m, T = 25 min,
parameter λ
Integration in time-domain is done from:
N * 3 m - / + Δ
Example for N = 2, i.e.: 6 m stop with Δ = 1.5 m, i.e.: 7.5 4.5 m
stop time at 6 m is:
t2 – t1
t2
t1
16
the test dive: D0 = 42 m, T = 25 min
Output from DIVE Version 3_09:
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the test dive: D0 = 42 m, T = 25 min
Output from DIVE Version 3_09:
λ = 122.0 exp 6 matches a standard ZH-L16 C decompression schedule
top of slide # 16, with TTS = 28 min
λ = 100.5 exp 6 conservative, similar to VPM: TTS = 37 min
λ = 165.0 exp 6 aggressive, similar to RGBM: TTS = 22 min
details: pls. cf. the next 2 slides
Legend:
TTS: time-to-surface, i.e.:
(bottom depth/ascent rate) + sum of all stop times
VPM: Varying Permeability Model, Ref. [3]
RGBM: Reduced Gradient Bubble Model, Ref. [4]
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the test dive: D0 = 42 m, T = 25 min
Output from DIVE Version 3_09:
λ = 100.5 exp 6 matches a conservative ZH-L16 C
decompression schedule with gradient factors
GF High = 0.9 / GF Low = 0.8
and deeper stops like VPM:
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the test dive: D0 = 42 m, T = 25 min
Output from DIVE Version 3_09:
λ = 165.0 exp 6 matches an aggressive ZH-L16 C
decompression schedule with gradient factors
GF High = 1.2 / GF Low = 0.6, short deep stops and
truncated shallow stops, like aggressive RGBM:
20
Sources / References:
[1] Bernard Gardette (November 2009) : THEORIE GENERALE
UNIFIEE DE LA DECOMPRESSION;
Directeur Scientifique COMEX, BG/sc-060/09
[2] Alexis Blasselle, Michael Theron, Bernard Gardette, Emmanuel
Dugrenot (2020) A new form of admissible pressure for Haldanian
decompression models
[3] Yount, D.E. Hoffman, D.C. (1986) On the use of a Bubble
Formation Model to calculate diving tables
[4] Wienke, B. R. (2003) RGBM in-depth
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Bonus Material:
Source for
DIVE Version 3_09
Download free of charge:
DIVE V 3_09
(https://www.divetable.info/DIVE_V3/index.htm)
and the german manual
https://www.divetable.info/DIVE_V3/DOXV3_0.pdf
The release train for
the english version (V3_04) is somewhat slower
https://www.divetable.info/DIVE_V3/V3e/index.htm
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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“)
Buehlmann Safety Factor („B“)
last stop depth („LS“)
And with: „awe recieve the complete decompression prognosis;
i.e.: the stop times in min per stage, modulo 3 m
and the responsible leading compartment & the rounded up TTS in
min. The latest DIVE Version for beta testing is always staged there:
https://www.divetable.info/beta/index.htm
along with information on production date, size in bytes, new features and
the checksums for verifying the download.
Fine tuning of DIVE:
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The test dive from above via the commands,
the input of commands and parameters are in the quotes: „ “
(ZH-L 16 C is the default coeffcients matrix)
„d“ (simulation of a box profile with these parameters:)
„42.“ (bottom depth)
„25.“ (bottom time)
„a“ „“ (yields this standard decompression prognosis):
the COMEX procedure is simulated via: „cp
pls. cf. slides #16, 18 & 19
the dialogue to manipulate the gradient factors is invoked with: „GF“
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