Decompression Theories, Models

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DecompressionTheories, Models Tables

• Karl E. Huggins
• USC Catalina Hyperbaric Chamber
• Wrigley Marine Science Center
• Catalina Island, CA

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Missions of theUSC Catalina Hyperbaric Chamber

• Treatment of Scuba Diving Casualties
• Educational Programs focused on Promotion of
  Scuba Diving Safety, Accident Response, and
  Treatment
• Reporting Information on Diving Accidents and
  Diving Practices
• Hyperbaric / Diving Research
• Equipment Testing

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Location of the Chamber

• USC Wrigley Marine Science Center
• Big Fisherman Cove
• West End of Catalina Island

• Near Two Harbors
• Isolated Location
• Rugged Terrain
• Where the Divers Are

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Popular Dive Sites within Minutes of Catalina
Hyperbaric Chamber
LionsHead?
EmeraldCove?
Ship Rock?
Eagle Reef ?
Bird Rock?
IsthmusReef?
Blue Cavern ?
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Farnsworth Banks
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USC Catalina Hyperbaric Chamber Where Do the
Patients Come From?
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Decompression Models,Tables Computers
What do they do?
What dont they do?
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The Case of the ShrinkingNo-Stop Times(100 fsw
No-Stop Limit - mid 1980s)

• 25 min. - U.S. Navy
• 20 min. NAUI / PADI / HUGI / BSAC
• 18 min. - Suunto SME-ML
• 17 min. - German Tables
• 15 min. - DCIEM Tables (Canada)
• 12 min. - Dacor Microbrain
• 11 min. - Dacor Microbrain Pro
  Plus
• 9 min. - Tekna Computek
• 8 min. - 1 Maximum
  Likelihood Tables

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WHAT ARE THEYALL TRYING TO DO?
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PREVENTDecompression Sickness
Symptoms resulting from the evolution and growth
of gas bubbles in the body fluids and tissues,
following a reduction in ambientpressure.
DCS The BENDS Caissons Disease
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BUBBLE FORMATION BLOOD VESSEL OBSTRUCTION TISSUE
DISTORTION DISRUPTION
DCS
PATHOPHYSIOLOGY
Platelet Aggregation Arterial Thrombosis Fibrinoly
sis Venous Clotting Slugging of Venous
Blood Plasma Loss
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Decompression SicknessVicious Cycle
Bubbles Form
Decreased Blood Flow
Decreased Elimination of Gas
Tissue Hypoxia
Edema
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Blow-Ups From Deep Dives
A 44-year-old male scuba diver died shortly after
a solo dive in great depth. He used a dry diving
suit and breathed Trimix diving gas with a
composition of 9.3 oxygen, 53.4 helium, and
33.9 nitrogen. According to witness state-ments,
he literally spurted out of the water, making
movements with his arms and rapidly losing
conscious-ness. After being rescued by
diving colleagues, he suffered a cardiopulmonary
arrest. Resuscitation attempts were futile.
Analysis of the diving computer showed a diving
depth of 100 to 125 m and a diving duration of
25 min.
Thomas Plattner, et. al., J Forensic Sci,
November 2003
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Decompression TermsSATURATIONExists whenThe
nitrogen pressure in the tissueis equal to the
nitrogen pressure in the breathing gas.
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Dive to 80 fsw
Nitrogen in Breathing Gas 80 fsw 33 fsw 113
fsw absolute x 0.79 (N2 fraction) 89.3
fswNitrogen Pressure in breathing gas
Nitrogen in Body Tissues 0 fsw 33 fsw 33 fsw
absolute x 0.79 (N2 fraction) 26.1 fswNitrogen
Pressure in body tissues
Nitrogen Gradient
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Nitrogen Pressure over Tissue RangeBody
Saturated at Surface (1 ata)
Fast
Slow
Tissues
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Nitrogen Pressure over Tissue RangeBody at 33
fsw (2 ata)
Fast
Slow
Tissues
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Nitrogen Pressure over Tissue RangeBody at 33
fsw (2 ata)
Fast
Slow
Tissues
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Nitrogen Pressure over Tissue RangeBody at 33
fsw (2 ata)
Fast
Slow
Tissues
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Nitrogen Pressure over Tissue RangeBody at 33
fsw (2 ata)
Fast
Slow
Tissues
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Nitrogen Pressure over Tissue RangeBody
Saturated at 33 fsw (2 ata)
Fast
Slow
Tissues
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Nitrogen Pressure over Tissue RangeBody at
Surface (1 ata) after33 fsw (2 ata) Saturation
Fast
Slow
Tissues
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Nitrogen Pressure over Tissue RangeBody at
Surface (1 ata) after33 fsw (2 ata) Saturation
Fast
Slow
Tissues
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Nitrogen Pressure over Tissue RangeBody at
Surface (1 ata) after33 fsw (2 ata) Saturation
Fast
Slow
Tissues
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Nitrogen Pressure over Tissue RangeBody
Re-Saturated at Surface (1 ata) after33 fsw (2
ata) Saturation
Fast
Slow
Tissues
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Decompression TermsSUPERSATURATIONExists
whenThe nitrogen pressure in the tissueexceeds
the total ambient pressureexerted on the
body.PtN2 gt Pamb
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N2
SEA LEVEL
.79 ATA
PA 1.0 ATA
PT PN2 SATURATED
PN2 0.79 ATA
PT lt PA
PT TISSUE N2 PRESSURE
33 FSW
PA 2.0 ATA
PN2 1.58 ATA
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Shallow SupersaturationStudy
Percent of Divers with Corresponding VGE Score
Of Divers
Depth (fsw)
4
3
2
1
0
0.0
0.0
4.0
16.0
80.0
25
12.0
1.9
14.8
16.7
22.2
44.4
54
16.0
18.8
15.6
15.6
21.9
28.1
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20.5
Eckenhoff - 1990
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Early 1900sLinear Decompression100 fsw / 20
min. 1 ata / 20 min.
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• HALDANE CONCEPT- - - -

NUCLEI ARE NOT PRESENT PRIOR TO DECOMPRESSION
Bubbles spontaneously form
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Decompression TermsCRITICALSUPERSATURATIONThe
maximum nitrogen tissuepressure tolerated at
any giventotal ambient pressureExpressed as a
ratio of PtN2 to PambCRITICAL RATIO PtN2 /
Pamb
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Haldanes Assumption
PT/PA gt S.S. RATIO Nitrogen bubbles form in the
body
PT/PA lt S.S. RATIO Nitrogen eliminated though
lungs
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Haldanes Observations
Supersaturation Ratio 1.58/1
Sea Level (1 ATA)
N2 Pressure 1.58 ATA
33 fsw (2 ATA)
Saturation Time Goats 3 hours Man 5 hours
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Haldanes Observations
Sea Level (1 ATA)
Supersaturation Ratio 3.95/2.5 or 1.58/1
49.5 fsw (2.5 ATA)
N2 Pressure 3.95 ATA
132 fsw (5 ATA)
Saturation Time Goats 3 hours Man 5 hours
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J.S. HaldaneDecompression ModelCompartment
Half-Time
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J.S. HaldaneDecompression ModelCompartment
Half-Time
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J.S. HaldaneDecompression ModelCompartment
Half-Time
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J.S. HaldaneDecompression ModelCompartment
Half-Time
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J.S. HaldaneDecompression ModelCompartment
Half-Time
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J.S. HaldaneDecompression ModelCompartment
Half-Time
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J.S. HaldaneDecompression ModelCompartment
Half-Time
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J.S. HaldaneDecompression ModelCompartment
Half-Time
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J.S. HaldaneMathematical Model
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J.S. HaldaneDecompression Model Calculations
100 fsw / 20 min.
OK _at_ 40 fsw
OK _at_ 30 fsw
5-min N2 pressure 3.03 ATA 3.03 ATA / 1.58
1.92 ATA (1.92 ATA 1 ATA) x 33 fsw/ATA 30.3
fsw FIRST STOP AT 40 FSW
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J.S. HaldaneDecompression Model Calculations 40
fsw / 1 min.
OK _at_ 30 fsw
5-min N2 pressure 2.87 ATA 2.87 ATA / 1.58
1.82 ATA (1.82 ATA 1 ATA) x 33 fsw/ATA 26.9
fsw OK TO ASCEND TO 30 FSW
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J.S. HaldaneDecompression Model Calculations 30
fsw / 3 min.
OK _at_ 20 fsw
5-min N2 pressure 2.41 ATA 2.41 ATA / 1.58
1.53 ATA (1.53 ATA 1 ATA) x 33 fsw/ATA 17.3
fsw OK TO ASCEND TO 20 FSW
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J.S. HaldaneDecompression Model Calculations 20
fsw / 5 min.
10-min pressure 2.02 ATA 2.02 ATA / 1.58
1.28 ATA (1.28 ATA 1 ATA) x 33 fsw/ATA 9.2
fsw OK TO ASCEND TO 10 FSW
OK _at_ 10 fsw
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J.S. HaldaneDecompression Model Calculations 10
fsw / 11 min.
20-min N2 pressure 1.57 ATA 1.57 ATA / 1.58
0.99 ATA (0.99 ATA 1 ATA) x 33 fsw/ATA -0.2
fsw OK TO ASCEND TO SURFACE
OK _at_ Surface
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J.S. HaldaneDecompression Model Calculations
100 fsw / 20 min.
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Linear vs. StagedDecompression
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Testing Haldanes Tables

• Chamber Dives - Series of seven decompression
  dives to a maximum of 180 fsw
• Openwater Dives Twenty staged decompression
  dives to a maximum depth of 210 fsw
• Only symptoms Skin Itches
• Tables presented to British Admiralty and
  promulgated to the fleet
• Occurrence of DCS greatly reduced

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• U.S. Navy
• Decompression
• Tables

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1915U.S. Navy Decompression Tables

• Calculated from Haldanes Model
• Used on Salvage of USS F-4 Submarine
• 306 fsw Hard Hat Dives on Air
• No Reported Problems

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Submarine Escape Training 1930s
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U.S. Navy Tables (1930s)Modifications to
supersaturation ratios
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Evaluation of 1937 U.S. Navy Decompression
Schedules
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U.S. Navy Decompression Model(1956)

• Problems with 1937 tables on short deep dives
  long shallow dives
• Put 5 10-min. compartments back into model
• Change 75-min. compartment to 80-min.
• Add 120-min. compartment to model
• Six compartment Haldanian Model
• M-value concept introduced

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U.S. Navy Model 1956M-VALUES

• The maximum amount of nitrogen
• pressure (expressed in fsw units)
• allowed in a specific compartment at
• a specific depth.
• M Mo (?M x Depth)
• Where
• Mo Surface M-Value
• ?M Change in M-Value per fsw (Delta M)

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U.S. Navy Model 1956Mo-VALUES

• The maximum amount of nitrogen
• pressure (expressed in fsw units)
• allowed in a specific compartment at
• sea level.
• Directly related to the compartments
• Critical Supersaturation (S.S.) Ratio
• Mo S.S. Ratio x 33 fsw

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U.S. Navy 1956 Air Decompression Model
No-D Depth Depth at which N2 pressure in air
equals the Mo value
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60 fsw No-Stop Limit DeterminationDepth
Equivalent Pressures t 0 min.
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60 fsw No-Stop Limit DeterminationDepth
Equivalent Pressures t 5 min.
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60 fsw No-Stop Limit DeterminationDepth
Equivalent Pressures t 10 min.
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60 fsw No-Stop Limit DeterminationDepth
Equivalent Pressures t 20 min.
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60 fsw No-Stop Limit DeterminationDepth
Equivalent Pressures t 30 min.
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60 fsw No-Stop Limit DeterminationDepth
Equivalent Pressures t 40 min.
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60 fsw No-Stop Limit DeterminationDepth
Equivalent Pressures t 50 min.
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60 fsw No-Stop Limit DeterminationDepth
Equivalent Pressures t 60 min.
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60 fsw No-Stop Limit DeterminationDepth
Equivalent Pressures t 64.5 min.
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120 fsw No-Stop Limit DeterminationNitrogen
Pressures t 0 min.
120 fsw 33 fsw 153 fswa 153 fswa x 0.79
120.9 fswaN2
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120 fsw No-Stop Limit DeterminationNitrogen
Pressures t 5 min.
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120 fsw No-Stop Limit DeterminationNitrogen
Pressures t 10 min.
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120 fsw No-Stop Limit DeterminationNitrogen
Pressures t 12.4 min.
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120 fsw No-Stop Limit DeterminationNitrogen
Pressures t 15 min.
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120 fsw No-Stop Limit DeterminationNitrogen
Pressures After 60 fsw/min. Ascent
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U.S. Navy Tables (1950s)60 fsw/min. Ascent Rate

• Haldane Tables (1908) No Faster than 60 ft.
  /min. to avoid missing first stop
• USN Diving Manual (1916) No faster than a foot
  per second
• USN Diving Manual (1943) No greater than 25
  feet per minute
• Hard Hat Divers wanted 25 fsw/min.UDT Divers
  wanted 100 fsw/min.
• Compromise of 60 fsw/min. put in 1959 USN Manual
  and remained for 40 years
• USN Diving Manual (1999) 30 fsw/min.

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U.S. Navy Tables (1950s)Repetitive Group
Designators

• How to handle repetitive dives?
• Initial idea 6 sets of tables based on each
  compartment
• RGD represents calculated nitrogen pressure in
  the 120-min. compartment
• Each group represents approximately 1.58 fsw
  nitrogen pressure
• Minimum 10 minute Surface Interval is to ensure
  none of the other five compartments will control
  a repetitive dive

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U.S. Navy Air TablesDefinition of Repetitive
Group Designators
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120-min. Compartment PressuresFrom
No-Decompression Table Entries
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35 fsw for 120 min. 39.90 fswN2 in 120 min.
compartment I 38.71 40.29 fswN2
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U.S. NAVYE-L ALGORITHM VVAL 18

• Nitrogen is absorbed in an exponential manner
  (Haldanian)
• Nitrogen is released in a linear manner
  (Non-Haldanian)
• Assumes presence of bubbles once nitrogen
  pressure exceeds ambient pressure
• Programmed in U.S. Navys Dive Computer SEAL
  Team Operations
• New USN Tables - 2008

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E-L Algorithm vs. Haldanian Model
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-34
-78
-37
n/a
-8
n/a
-2
-1
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Time to Reach New RGD from Group Z
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OTHER DECOMPRESSION MODELS AND TABLES

• Modified U.S. Navy Tables
• Other Haldanian Models Tables
• Pseudo-Haldanian Models Tables
• Non-Haldanian Models Tables

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• BRITISH
• Royal Navy Physiological Lab
• Model and Tables

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Development of HemplemansTissue Slab Model
(1952)
Capillary
N2
N2
Tissue
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BSAC 88 Tables

• Derived from RNPL Model
• Seven Tissue Codes A-G
• Four Surface Pressure Ranges
• 28 End of Dive Tables
• Surface Interval Table
• No Math Calculations

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• SWISS
• (BUHLMANN)
• MODEL TABLES

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Bühlmann Model Tables(ZH-16 Model)

• Continual Development from 1960s 1990s
• 16 Compartments (2.65 635 min.)
• No-Stop limits shorter than U.S. Navy limits
  (lt130 fsw)

• 80-min. Compartment used to control Repetitive
  Diving Calculations
• Two Altitude Ranges
• 0 700 m (0 -2300 ft.)
• 700 2500 m (2300-8300 ft.)
• Modified versions of modelused in many dive
  computersand PC decompressionprograms

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• CANADIAN
• (DCIEM)
• TABLES

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Serial vs. Parallel Model
Serial Model
C1
Cn
C3
C2
Pa

Pa
C1
Cn
C3
C2

Parallel Model
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DCIEM Model Compartment Pressures
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DCIEM Decompression Tables

• Full Set in DCIEM Diving Manual
• DCIEM Sport Diving Card
• Repetitive Factors
• DCIEM E-Z No- Calculation Tables

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• THE
• DOPPLER
• REVOLUTION

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No-Decompression Time Comparison(Spencer, et al
vs. US Navy)
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Reduction of No-Stop LimitsBased on Doppler
Bubble Detection
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Jeppesen Tables
Stay within the Red Line
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PADI / DSATRecreational Dive Planner

• Haldanian Model
• 9 Compartments (5 120 minutes)
• Mo Values based on Spencers reduced
  No-Decompression Limits
• 60-minute Compartment used to compute Repetitive
  Group Designators
• 3 6 Hours to clear residual nitrogen
• Two versions - Table Wheel

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HUGI / MICHIGAN SEA GRANT TABLES

• 6 Compartments (5 120 minutes)
• Mo Values based on Spencers reduced
  No-Decompression Limits
• All 6 Compartments used to computer the
  Repetitive Group Designators ( of Mo value)
• 12 15.5 Hours to clear residual nitrogen

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Two-Phase Bubble Models

• Control micro-nuclei bubble growth
• Varying Permeability Model (University of Hawaii)
• Reverse Gradient Bubble Model (Wienke Los
  Alamos Laboratory)
• Finding use in some Dive Computers and PC
  Decompression Programs

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• E.N. HARVEY CONCEPT - - -

NUCLEI ( GAS SEEDS) ARE PRESENT PRIOR TO
DECOMPRESSION
Bubbles grow from seeds
These are two-phase models.
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Varying Permeability Model(Tiny Bubble Group)
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Varying Permeability Model(Tiny Bubble Group)
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Reduced Gradient Bubble ModelBruce
Wienke Los Alamos Labs
?
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Gernhardt Bubble Growth Calculations165 fsw / 12
min.Air vs. Oxygen at 10 fsw stop
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STATISTICALLY BASEDDECOMPRESSION MODELS

• Decompression Sickness is a probabilistic event
• Use historical data (Chamber and Openwater
  studies)
• Maximum Likelihood Method to determine Best Fit
  Model
• Model will best fit dives similar to the
  historical data
• Model can be adjusted as new data becomes
  available

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Dose-Response Curve
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Saturation Pressure vs. DCS(Haldanes Goats)
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No-D Limit for a dive to 60 fswfollowing a dive
to 80 fsw for 25 min.
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Dive Table Problem
SI 240
?
53 / 40 min.
65 / 20 min.
85 / 25 min.
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Dive Table Problem
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Dive Computers Origins

• 1951 Committee for Undersea Warfare and
  Underwater Swimmers
• Groves Monk report on how to control free
  swimming diver
• Preliminary design for diver-carried
  decompression device
• Pneumatic computer design sent to Foxboro

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Foxboro Decomputer Mark 1
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SOS Decompression Meter

• A.K.A.

• THE BEND-O-MATIC

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DCIEM Pneumatic Dive ComputerKidd Stubbs
Serial Model

• Four compartment pneumatic computer
• Extensively tested ????
• Expensive to maintain
• Basis of Kidd Stubbs model

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DCIEM DIGITAL DECOMPRESSIONCOMPUTERS XDC-3
(Cyberdiver)
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Dive Computer Revolution - 1983
EDGE 12 Compartment Model (based on Spencer,
et. al. Doppler studies reduced No-D
limits) DECOBRAIN Swiss Tables Bühlmann (5
sets MLD allowed)
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• Dive Computer Tests

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Dive Computer Tests130 fsw Multi-Level Dive
PADI / DSAT Recreational Dive Planner
Tests Profile 12 19 Person-Dives 0 Cases
DCS 2 Cases Grade I VGE
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Dive Computer Tests130 fsw Multi-Level Dive(28
min. _at_ 45 fsw)
Required Decompression Time
No-Decompression Time
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Dive Computer Tests165 fsw / 12 min.
Decompression Dive
?
Catalina Hyperbaric Chamber 165 fsw Orientation
Dive Modified 170 fsw / 15 min. DCIEM Deco
Schedule 6 min. _at_ 30 fsw 7 min. _at_ 20
fsw 10 min. _at_ 10 fsw on O2 gt1000 Person
Dives 1 Questionable DCS 10 VGE (Grades I or
II)
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Dive Computer Tests 165 fsw / 12 min.
Decompression Dive (Time to Clear Decompression
Obligation _at_ 30 fsw)
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?
WHAT IS A DIVE COMPUTER?
A TOOL!
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DIVE COMPUTERSHOW DO THEY WORK?

• Depth Time Input
• Decompression Status computed from pre-programmed
  model
• Decompression Status displayed to diver
• Diver uses this status as one other piece of
  information to make decisions about the dive,
  while understanding the limitations of the Dive
  Computer

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Device Housing
Clock
ROM
RAM
Microprocessor
PressureTransducer
A/D Converter
Ambient Pressure
Battery
DISPLAY
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• THEORY

• MODEL

• TABLE

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U.S. Navy No-D Table Dive Profile Resolution 140
PossibleDepth/Time Entries
147
Dive Computer Profile Resolution(Transducer
Resolution 0.5 fsw / Update Interval 3
sec)10 fsw Depth Range over 1 minute400
Square-Wave Profiles / 2020 Total Profiles
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Initial Pressure
New Pressure
No-D / Deco Time
Mo Value
Pi(1)
Pf(1)
T(1)
M(1)
Pi(2)
Pf(2)
T(2)
M(2)
Pi(3)
Pf(3)
T(3)
M(3)
Pi(4)
Pf(4)
T(4)
M(4)
Pi(n)
Pf(n)
T(n)
M(n)
Ambient Pressure
Decompression Status
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Square Wave vs. Multi-Level DiveDive Computer
with U.S. Navy Model
Actual Multi-Level Profile
Square Wave Profile
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5
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Dive Computers

• Advantages
• No Max Depth / Entire Bottom Time Rule
• Uses Actual Depth of Dive (51 vs. 60 fsw)
• Integrates Dive Profile
• Entire Model Used to Calculate MLDs
• Computational Reliability
• Accurate Depth Readings (1-2 fsw)
• Ascent Rate Warnings
• Dive Profile Recording

• Disadvantages
• No Max Depth / Entire Bottom Time Rule
• Uses Actual Depth of Dive (51 vs. 60 fsw)
• Integrates Dive Profile
• If Computer pushed to Limit Model Pushed to
  Limit (Model Testing?)
• Possible Mechanical or Electrical Failure
• Diver Needs to Under-stand the Limitations of
  the Computer
• Possible Crutch

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Theories and Models vs. Reality Factors
Influencing DCS Susceptibility
Depth Time Ascent Rate Temperature Profile
Sequence Breathing Mixture Exertion
Level Physical Condition Limb Positioning Hydratio
n Level Age Body Composition What Do The Dive
Computers Know?
152
Dive Computer Advertisement This calculation
model takes into account dissolved as well as
gaseous nitrogen formation (microbubbles) in the
Venous and Arterial blood supply and tissue
groups relative to ascent rate, decompression,
etc. The model employed is adaptive because
it factors in human physiological changes that
can affect time versus Saturation / Desaturation,
during diving Work output, body temperature,
etc.
Things are not always what people say they are
Death ray, fiddlesticks! Why, it doesn't even
slow them up.
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Abuse of Dive Compuers

• Pushing dive computers to their limits
• Exceeding model and/or tested limits
• Blindly trusting the dive computer
• Exceed dive computer operational limits
• Ignore decompression requirements
• Turn off dive computer to clear residual nitrogen
• Continue to dive with a dive computer which did
  not turn on for the first dive
• Switching dive computers during a day of diving
• Hanging dive computer to clear warnings and
  prevent freeze-up

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When Dive Computers are Witness
es
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Summary

• Dive computers are only tools
• Over 75 dive computers models in 2003 Many more
  older models
• Very limited human subject testing
• Many allow algorithm adjustments
• Selection tends to be based on the features and
  functions desired
• They do not know what is going on in your body,
  no matter what their advertising says
• They can provide valuable post-dive information
• and REMEMBER

162
NO TABLE ORDIVE COMPUTERIS100 EFFECTIVEIN
PREVENTINGDECOMPRESSION SICKNESS!!
163
They know where they are
They just dont remember how they got there
164
A Mathematical Model

• PT(n) P0(n)
• (Pa - P0(n))
• (1 e(kt/T½(n)))
• M(n) M0(n)
• ?M(n) Depth

Does Not A Body Make!
165
Models, Tables, and Computers Produce Dive
Profile Envelopes that are hopefullySAFE FOR
MOST OF THE PEOPLE MOST OF THE TIME
166
What about Safety Stops?DO THEM!

• Decreases Decompression Stress
• Reduces Bubble Formation
• On shallow dives they help slow down ascents
• Dont blow by Safety Stop because you are near
  your No-D limit
• Breathing Oxygen at Safety Stop?
• Blowing Safety or Deco Stops on a Rescue Dive?

167
What about Deep Stops?

• Direct ascent from deeper depths to the Safety
  Stop produces a large pressure gradient in fast
  tissues
• Short Deep Stop helps reduce the pressure
  gradient
• Stop Half-Way between depth of dive and Safety
  Stop Depth for 1 min. (Depth 100 fsw Safety
  Stop 20 fsw Stop at 60 fsw for 1 min. on
  ascent to 20 fsw)
• This time should be considered part of your
  Bottom Time
• Some recent studies question effective- ness of
  deep stops in deco. dives

168
Activities Diving

• Hydration Before and After Dive(? blood
  perfusion gas exchange)
• Heavy Exertion
• Before the Dive (? micro bubble formation?)
• During the Dive (? inert gas uptake)
• After the Dive (? micro bubble formation )
• Mild Activity at Safety Stop (? inert gas
  washout)
• Holding Things Tightly or Bending Limbs Tightly
  During the Dive, esp. on Ascent at the Safety
  Stop (? inert gas washout)
• Laying Down or Sleeping After the Dive (? inert
  gas washout)

169
Exercise in Man the Day Before DivingMaximum
Bubble Grade (Median, Hi, Lo, 25 75)(18 msw
/ 80 min ? 3 msw / 7 min.)
Dujic, et. al., 2004
170
Nitric Oxide Releasing AgentBefore DivingMean
Rat Survival Time (700 kPa / 45 min)
Wisløff, et. al., 2004
171
Divers Responsibilities

• Acknowledge risk involved
• Understand limitations of Dive Computers and
  Tables
• Dont push Dive Computers or Tables to their
  limits
• Add Safety Factors
• Dont think of Dive Computers as anti-DCS
  Talismans
• Use COMMON SENSE!

172
It was YELLOW
What Dive computer were you using?