1. BSAC Ocean Diver Training
What happens if …..?

2. What happens if ….? Aims Potential problems
Decompression Illness (DCI)
Gas bubbles
Lung damage
Nitrogen narcosis
Oxygen toxicity
Breathing gas
Contamination
Loss
Effecting a rescue

3. 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%

4. DCI - Gas Bubbles Cause Effects
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

5. DCI - Lung Damage Cause Effects Ascent too fast Breath hold ascent
Over expansion - physical damage to lung tissue
Pleural Membrane
Collapsed lung (Pneumothorax)
Bubbles between organs and tissues (Emphysema)

6. DCI - Signs and Symptoms
Signs and symptoms appear from seconds to many hours after surfacing
DENIAL

7. 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

8. Divers’ first aid tool - Oxygen
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

9. Nitrogen Narcosis Cause Signs Resolution
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

10. O2 Oxygen Toxicity Oxygen can be toxic depending upon: Signs Depth
Time
Mix
Signs
Visual or auditory disturbances
Muscular twitching
Convulsions O2

11. Oxygen Toxicity Resolution Prevention
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

12. 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

13. 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

14. The Incident Pit
Minor
incidents
Normal
activity
Emergency
Fear
Serious
Panic
Fatal
Death
Resolving an underwater problem early prevents more serious consequences

15. 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

16. Prevention and Resolution
Prevention is better than cure
Act early - Regain control
Resolve problem or assist/rescue
Buddy monitoring
Practice, practice, practice

17. 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

18. Rescues - Controlled Buoyant Lift (CBL)
CBL ascent
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?
If convulsing (O2 toxicity) wait until convulsions stop before lifting

19. Rescues - Free Ascent Purpose Resolution Free ascent A last resort
May just require finning upwards
May require release of weight system
Will result in positive buoyancy on ascent
Exhale continuously

20. 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

21. Summary Resolving potential problems Effecting rescues Surface support
Decompression Illness (DCI)
Nitrogen Narcosis
Oxygen Toxicity
Problems with air
Effecting rescues
Surface support