Transcript No Slide Title

BSAC Ocean Diver Training
What happens if …..?
OT6.1
08/02
What happens
if…..?
What happens if ….?
Aims
Potential problems
 Decompression Illness (DCI)
 Gas bubbles
 Lung damage
 Nitrogen narcosis
 Oxygen toxicity
 Breathing gas
 Contamination
 Loss
 Effecting a rescue
OT6 2
08/02
What happens
if…..?
DCI - Nitrogen
Nitrogen release
 An ascent will not release all
nitrogen absorbed on dive
 Ascent has to be controlled
 Nitrogen continues to be released
for many hours
 Another dive within this time period
adds to nitrogen level
 Manage nitrogen to minimize risk of
DCI
 Tables and computers
 Dive practice
 Use a breathing gas with O2 > 21%
OT6 3
08/02
What happens
if…..?
DCI - Gas Bubbles
Cause
 Inadequate elimination of
nitrogen during ascent - bubbles
 Gas embolism during ascent
Effects
 Bubbles can form in tissues
 Distort and disrupt tissue
 Compress, damage blood vessels
 Reduces oxygen delivery to
‘downstream tissues
 Bubbles can form in/enter blood
 Block blood flow
 Reduces oxygen delivery to
‘downstream’ tissues
OT6 4
08/02
What happens
if…..?
DCI - Lung Damage
Cause
 Ascent too fast
 Breath hold ascent
Effects
 Over expansion - physical
damage to lung tissue
 Collapsed lung (Pneumothorax)
 Bubbles between organs and
tissues (Emphysema)
OT6 5
08/02
Pleural
Membrane
What happens
if…..?
DCI - Signs and Symptoms
Signs and symptoms appear from
seconds to many hours after surfacing
DENIAL
OT6 6
08/02
What happens
if…..?
DCI - Signs and Symptoms
 Chest discomfort, pain
 Voice change, crepitation
 Shortness of breath
 Itches and/or rashes
 Aches in joints
 Numbness, tingling
 Visual disturbances, dizziness
 Nausea, headaches, confusion
 Weakness, paralysis
 Unconsciousness
OT6 7
08/02
What happens
if…..?
DCI - Treatment
ONLY ONE !
 Recompression Chamber
 Reduces bubble size and may
restore circulation to affected area
 Specialist supervision from a
diving medic
Divers’ first aid tool - Oxygen
 Increased oxygen level improves
delivery to damaged tissues
 Assists in nitrogen elimination
OT6 8
08/02
What happens
if…..?
Nitrogen Narcosis
Cause
 Thought that nitrogen under
pressure affects nerve impulse
transmission - noticed below 30
metres
Signs
 Generally similar to the effects of
alcohol
Resolution
 Re-ascending to shallow depths
immediately resolves narcosis
OT6 9
08/02
What happens
if…..?
Oxygen Toxicity
Oxygen can be toxic depending upon:
 Depth
 Time
 Mix
Signs
 Visual or auditory disturbances
 Muscular twitching
 Convulsions
OT6 10
08/02
O2
What happens
if…..?
Oxygen Toxicity
Resolution
 Abort the dive, return to surface
Prevention
 Each mix has a “Maximum Operating Depth” (MOD)
32% - 35 metres for NO-STOP dives
36% - 30 metres for NO-STOP dives
 Analyse Nitrox mix before use
 Do NOT exceed the MOD for your gas mix
OT6 11
08/02
What happens
if…..?
Contaminated Breathing Gas
Cause
 Problems with compressor
Detection
 Oily taste or smell
 Reduces lungs’ efficiency
 Possible carbon monoxide level too high
 Reduces oxygen delivery by blood cells to
tissues
 New cylinder or abort dive immediately
OT6 12
08/02
What happens
if…..?
Contaminated Breathing Gas
Effects on diver
 Nausea
 Dizziness or disorientation
 Headache following a dive
Resolution
 Abort the dive
 Buddy to assist if necessary
 Advisable not to dive again on same day
 Consider seeking medical attention
 Report to Dive Manager
 Report to filling station
OT6 13
08/02
What happens
if…..?
The Incident Pit
Normal
activity
Minor
incidents
Emergency
Fear
Serious
Fatal
Panic
Death
Resolving an underwater problem early
prevents more serious consequences
OT6 14
08/02
What happens
if…..?
Preventing Problems
Diving has a very good safety record
Safety does not happen by
accident and problems are
prevented by:
 Dive planning and anticipation





Training, practice and experience
Equipment, buddy checks
Monitoring during a dive
Common sense
Support of other divers in group
 Oxygen administration
 Rescue management
 Seeking diving medical expertise
OT6 15
08/02
What happens
if…..?
Prevention and Resolution
Prevention is better than cure
Act early - Regain control
Resolve problem or
assist/rescue
Buddy monitoring
Practice, practice, practice
OT6 16
08/02
What happens
if…..?
Rescues Alternative Supply (AS)
Cause
 Failure to monitor gas supply
 Equipment failure - rare
Resolution
 AS is a “back up” system
 Dive should be aborted
 Rescuer to fully inflate own BC
on surface
 Inflate casualty’s BC by mouth
AS ascent
OT6 17
08/02
What happens
if…..?
Rescues - Controlled
Buoyant Lift (CBL)
Cause
 An incapacitated buddy
 An unconscious buddy - rare
Resolution
 Priority to get casualty to surface
 May involve slightly faster than normal
ascent
 Ensure casualty buoyant on surface
 Give emergency signal
 Alternative means of positive buoyancy?
CBL ascent
 If convulsing (O2 toxicity) wait until
convulsions stop before lifting
OT6 18
08/02
What happens
if…..?
Rescues - Free Ascent
Purpose
 A last resort
Resolution
 May just require finning upwards
 May require release of weight
system
 Will result in positive buoyancy
on ascent
 Exhale continuously
Free ascent
OT6 19
08/02
What happens
if…..?
Rescues - Surface Support
Experienced divers/surface
cover organise assistance
on the surface
 Monitor both rescuer and
casualty
 Administer oxygen first aid if
required
 Seek specialist advice of a
Diving medic
 Arrange urgent recompression
treatment if required
OT6 20
08/02
What happens
if…..?
Summary
Resolving potential problems
 Decompression Illness (DCI)
 Nitrogen Narcosis
 Oxygen Toxicity
 Problems with air
Effecting rescues
Surface support
OT6 21
08/02
What happens
if…..?
OT6 22
08/02