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Decompression v1.0
DecompressionDecompression
DEC/1May 2007
Decompression v1.0
We will coverWe will cover
• What is Decompression?What is Decompression?
• Causes of Decompression SicknessCauses of Decompression Sickness
• When and how symptoms occurWhen and how symptoms occur
• TreatmentTreatment
DEC/2
Decompression v1.0
What is Decompression?What is Decompression?
• Reduction in ambient pressureReduction in ambient pressure
• Occurs when a diver ascends from depthOccurs when a diver ascends from depth
• Tissue absorption ratesTissue absorption rates
• Gas may remain in some tissues longerGas may remain in some tissues longer
• Bubble formationBubble formation
• Other namesOther names
DEC/3
Decompression v1.0
DepthAbsolute Pressure
Partial Pressures
0
10M
20M
30M
40M
1 Bar 0.8 0.2
2 Bar 1.6 0.4
3 Bar 2.4 0.6
4 Bar 3.2 0.8
PN2 PO2
5 Bar 4.0 1.0
DEC/4
Decompression v1.0
How does the gas enter How does the gas enter the tissues?the tissues?
• Alveoli in the lungsAlveoli in the lungs
• BloodstreamBloodstream
• Body TissuesBody Tissues
• Amount depends on pressure and duration Amount depends on pressure and duration at pressureat pressure
DEC/5
Decompression v1.0
SaturationSaturation
DEC/6
Depth
0 M
10 M
20 M
30 M
40 M
Time
Nitrogen Level in Tissues
Low High
Decompression v1.0
SupersaturationSupersaturation
DEC/7
DepthSaturation Level of N2
0 M
10 M
20 M
30 M
Diver’s Level of N2
Supersaturated
Saturated
Undersaturated
ASCENT
Bubbling Out
Decompression v1.0
PrecautionsPrecautions
• Standard rate of ascentStandard rate of ascent
• Decompression Dive TablesDecompression Dive Tables
DEC/8
Decompression v1.0
Factors Affecting D.C.S.Factors Affecting D.C.S.
DEC/9
• AlcoholAlcohol
• SmokingSmoking
• DehydrationDehydration
• Fatty tissuesFatty tissues
• FatigueFatigue
• DrugsDrugs
• MedicationMedication
• Cold waterCold water
• Heavy exerciseHeavy exercise
Decompression v1.0
When do Symptoms Occur?When do Symptoms Occur?
DEC/10
• Rarely occur immediatelyRarely occur immediately
• 50% begin less than one hour after surfacing50% begin less than one hour after surfacing
• 90% occur within 6 hours90% occur within 6 hours
• Small percentage over 24 hoursSmall percentage over 24 hours
Decompression v1.0
Symptoms of Symptoms of Decompression SicknessDecompression Sickness
DEC/11
• SkinSkin
– DiscolourationDiscolouration
– ItchingItching
• JointsJoints
– AcheAche
– Pain (sometimes severe)Pain (sometimes severe)
Decompression v1.0
Symptoms of Symptoms of Decompression SicknessDecompression Sickness
DEC/11a
• Nervous System Nervous System
– BehaviourBehaviour
– NumbnessNumbness
– WeaknessWeakness
– BalanceBalance
– ParalysisParalysis
Decompression v1.0
Symptoms of Symptoms of Decompression SicknessDecompression Sickness
DEC/11b
• Heart and LungsHeart and Lungs
– Low blood pressureLow blood pressure
– ShockShock
– CyanosisCyanosis
• VisionVision
– Double visionDouble vision
Decompression v1.0
TreatmentTreatment
• First AidFirst Aid
DEC/12
• Recompression ChamberRecompression Chamber
Decompression v1.0
First AidFirst Aid
• Lie victim downLie victim down
• Give 100% oxygenGive 100% oxygen
• Keep warm and reassureKeep warm and reassure
• Treat for shockTreat for shock
• CPR if necessaryCPR if necessary
DEC/13
Decompression v1.0
SummarySummary
• What is Decompression?What is Decompression?
• Causes of Decompression SicknessCauses of Decompression Sickness
• When and how symptoms occurWhen and how symptoms occur
• TreatmentTreatment
DEC/14
Decompression v1.0
QuestionsQuestions
Decompression v1.0
Body tissues absorb gas at :Body tissues absorb gas at :
(a) (a) The same rateThe same rate
(b) (b) Different ratesDifferent rates
Question 1
Decompression v1.0
Body tissues absorb gas at :Body tissues absorb gas at :
(a) (a) The same rateThe same rate
(b) (b) Different ratesDifferent rates
Question 1
Decompression v1.0
The gas which causes The gas which causes
decompression sickness is:decompression sickness is:
(a) (a) OxygenOxygen
(b) (b) Carbon DioxideCarbon Dioxide
(c) (c) NitrogenNitrogen
Question 2
Decompression v1.0
The gas which causes The gas which causes
decompression sickness is:decompression sickness is:
(a) (a) OxygenOxygen
(b) (b) Carbon DioxideCarbon Dioxide
(c) (c) NitrogenNitrogen
Question 2
Decompression v1.0
What percentage of decompression sickness What percentage of decompression sickness
usually occurs within 1 hour of surfacing ?usually occurs within 1 hour of surfacing ?
(a) (a) 35%35%
(b) (b) 50%50%
(c) (c) 70%70%
(d)(d) 90%90%
Question 3
Decompression v1.0
What percentage of decompression sickness What percentage of decompression sickness
usually occurs within 1 hour of surfacing ?usually occurs within 1 hour of surfacing ?
(a) (a) 35%35%
(b) (b) 50%50%
(c) (c) 70%70%
(d)(d) 90%90%
Question 3
Decompression v1.0
Symptoms of The Bends include :Symptoms of The Bends include :
(a) (a) Skin discolourationSkin discolouration
(b) (b) Numbness or weaknessNumbness or weakness
(c) (c) Imbalance or paralysisImbalance or paralysis
(d) (d) ShockShock
(e) (e) All of the aboveAll of the above
Question 4
Decompression v1.0
Symptoms of The Bends include :Symptoms of The Bends include :
Question 4
(a) (a) Skin discolourationSkin discolouration
(b) (b) Numbness or weaknessNumbness or weakness
(c) (c) Imbalance or paralysisImbalance or paralysis
(d) (d) ShockShock
(e) (e) All of the aboveAll of the above
Decompression v1.0
Treatment of decompression Treatment of decompression
sickness is :sickness is :
Question 5
(a) (a) OxygenOxygen
(b) (b) Recompression chamberRecompression chamber
(c) (c) In-water recompressionIn-water recompression
(d)(d) Strong drink i.e. brandyStrong drink i.e. brandy
Decompression v1.0
Treatment of decompression Treatment of decompression
sickness is :sickness is :
Question 5
(a) (a) OxygenOxygen
(b) (b) Recompression chamberRecompression chamber
(c) (c) In-water recompressionIn-water recompression
(d)(d) Strong drink i.e. brandyStrong drink i.e. brandy
