1. Shallow Water Blackout & Secondary Drowning
Amy Peden
National Manager – Research and Policy, Royal Life Saving Society – Australia and
Associate Professor Richard Franklin, James Cook University and Royal Life Saving Society – Australia
Amy

2. Drowning in Australia
292 people on average drowned in Australia each year for the past 10 years
The 2014 Royal Life Saving National Drowning Database found that 266 people drowned in 2013/14
81% of all drowning victims were male
Amy

3. Drowning in Australia 2013/14
Largest number of drowning deaths occur in rivers, creeks and streams
Swimming pools overtook beaches as the second leading location for drowning
Amy

4. Drowning in Australia 2013/14
There are a diverse range of activities being undertaken prior to drowning in Australia
Amy

5. Drowning Defined
“Drowning is the process of experiencing respiratory impairment from submersion/immersion in liquid.”
Drowning outcomes should be classified as: death, morbidity, and no morbidity.
There was also consensus that the terms wet, dry, active, passive, silent, and secondary drowning should no longer be used.
Amy

6. The Physiology of Drowning
Mouth, nose submerged
Aspiration
Breath hold
Cold shock
Diving response
Autonomic conflict
Laryngospasm
Inhalation of Water
Ingestion
Cardiac Arrest
Richard

7. Shallow Water Blackout – How does it happen?
Shallow Water Blackout (SWB) occurs because the normal, protective ‘breakpoints’ have not been triggered before unconsciousness (due to cerebral hypoxia).
There are two chemical sensors in the body which detect the levels of oxygen and carbon dioxide (Co2) & protect us from a lack of oxygen.
Richard

8. Shallow Water Blackout – How does it happen?
The CO2 sensor is the most sensitive.
Hyperventilation i.e. ‘blowing off’ too much Co2 before submerging can interfere with the sensor which is not triggered early enough to prevent blackout.
Richard

9. The “Break Point”
Richard

10. Also Known As Shallow Water Blackout Hypoxic Blackout
Underwater blackout
The Long dive
Long breath holding
Surface Blackout
Deep water blackout
Freediver blackout
Latent hypoxia
Richard
Surface blackout occurs when a diver surfaces after being underwater, has begun breathing, yet blacks out before the inhaled oxygen has time to reach the brain

11. Why?
The activity of breath-holding is common and often an essential part of some underwater sports, such as underwater hockey, synchronised swimming and free-diving (the activity of seeing how deep/ far a person can swim on one breath).
It also occurs recreationally while trying to swim as far as possible underwater on a single breath.
Richard

12. Shallow Water Blackout
There are challenges around quantifying the role of SWB in broader drowning fatalities
Often the activity prior to drowning is unwitnessed so hard to know if the deceased was participating in breath-holding activities
No autopsies to rule out other potential causes such as cardiac arrhythmias and seizure disorders (Long QT Syndrome)
Richard

13. Differential Diagnoses
Voluntary endurance underwater swimming with pre-submersion hyperventilation
Hypoxic seizures (convulsions) can result from hypoxia following pre-dive hyperventilation.
Hypoxic triggering of cardiac dysrhythmia consequent upon pre-existing genetic or acquired electrical conduction abnormalities of the heart.
Cardiac dysrhythmias secondary to the normal diving response, conduction defects sensitised by pre-existing cardiac conditions.
Association with the normal physiological “cold shock” response.
Richard
While associated with endurance underwater swimming, other differential diagnoses include:

14. Prevention Strategies
A number of prevention strategies proposed. These include:
Increasing awareness of the dangers of hyperventilation
Use of lifeguards & facility staff to discourage the practice at venues
Ensuring the practice of hyperventilation is not part of any sport; and
Where breath-holding is undertaken, appropriate medical and rescue personnel, devices and procedures must be in place.
Richard
If they do want to train for it – appropriately supervised, oxygen on hand and potentially someone in the water with scuba diving equipment

15. Known deaths in Australia
Drowning deaths associated with Shallow Water Blackout in Australia commonly fall into one of three categories:
Free-divers and spear fishermen: most commonly in the ocean
Those training to complete in activities such as underwater hockey or free-diving: most commonly in public pools
Those recreating in home swimming pools and holding breath
Amy – how it links to prevention

16. Known deaths in Australia
Between 1 July 2002 and 30 June 2012, there were 16 deaths known to be related to SWB.
8 deaths involved males between the ages of 16 and 35 swimming laps underwater, in swimming pools (5 public and 3 private).
There were a further 8 deaths among 21 to 40 year old males whilst free-diving for the purposes of spear fishing in the ocean
Amy

17. SWB – Prevention Strategies
Public awareness & public education through fact sheets
Royal Life Saving Fact Sheet on Shallow Water Blackout
Amy

18. SWB Prevention Strategies
Diver specific education
Undertaken by Divers Alert Asia Pacific
Amy

19. Policies Amy – name check others but focus on development of it
International Life Saving Federation Policy Statement no 12 on Shallow Water Blackout & Medical Position Statement
RLS Medical Statement
US RED CROSS / INTERNATIONAL SWIMMING???

20. Case Studies & Media Attention
Recent media has highlighted the dangers related to activities involving breath-holding and pre-immersion hyperventilation:
What follows are three real life cases from recent years
Amy

21. Case Study 1
Amy
Prevention – awareness of th eissues, understanding own limitation, if they’d had scuba gear – get air into him quicker
A 19 year old man drowned at Hutchison Reef free-diving.
Authorities said he was with 3 friends when he black out near the surface and sank 30 metres in “what appeared to be an unconscious state.”
He was brought to the surface after his friends dove 30metres without breathing to retrieve his body, however he could not be revived. The group had gone out for the day spear fishing and free-diving.

22. Case Study 2 Amy Awareness – no safe number of times to do it
Physical limitations
Competition
Awareness – had been done multiple times and they hadn’t thought about the dangers
Challenge around this – no safe number of times to do it – how to raise awareness
CONSIDER PLAYING VIDEO HERE
A 34 year old man drowned whilst trying to hold his breath underwater in his brother’s swimming pool on Australia Day.
The deceased was practising holding his breath ahead of a scuba diving trip. His family said he went underwater for a third time that day and did not resurface.
His wife and brother dragged him from the water and attempted CPR but it was too late. “Both he and his brother would always just like to have a competition to see who could hold their breath the longest. He could hold his breath for about two minutes and fifty seconds” said the deceased man’s wife.

23. Case Study - 3
An 18 year old male has drowned in a public pool due to shallow water blackout. The male was swimming laps of the pool whilst holding his breath for the purposes of training for underwater hockey. The deceased had completed between 4 and 6 laps of the 50m pool underwater using flippers and a face mask. The deceased had swum two of the laps completely underwater and decided to try swimming another on a single breath without flippers.
Amy
Awareness
Training Situation
Discouiraging the behaviour at the facility
Supervision by life guards – do you want this to happen in your pool
Lane beside the edge of the pool
Defib on hand
Easy access – someone walking alongside – challenging if people want to understake this behaviour how to stop it?
An 18 year old male has drowned in a public pool due to shallow water blackout.
The male was swimming laps of the pool whilst holding his breath for the purposes of training for underwater hockey.
The deceased had completed between 4 and 6 laps of the 50m pool underwater using flippers and a face mask. The deceased had swum two of the laps completely underwater and decided to try swimming another on a single breath without flippers.

24. Long QT Syndrome
What is it?
Richard

25. Long QT Syndrome Triggers
It is important that a genetic autopsy following unexpected drowning in young people including SWB is undertaken. It is best practice, if a coroner identifies a good swimmer who drowns, for the first degree relatives (parent, child or full siblings) to also be tested.
Richard

26. Secondary Drowning – A variety of terms
Dry drowning
Delayed drowning
Passive drowning
Terms such as these should be discouraged
Please use the term drowning and add appropriate outcome (e.g. fatal, non-fatal, morbidity, no morbidity)
Richard

27. Secondary drowning
Secondary Drowning occurs when someone breaths in small amounts of water.
This triggers the muscles in the airway to spasm and makes breathing difficult. Fluid builds up in the lungs and causes trouble breathing.
What are the risks?
Secondary or dry drowning is not common, and is estimated to account for 1-2% of drowning
Richard
There is a secondary term for people who drown without aspiration of water
2 meanings
1 is for people who drown without water in the lungs (no aspiration)
2 is for people who die or are hospitalised post aquatic activity

28. Secondary drowning Prevention
Supervision is key, especially for children and inexperienced swimmers
Restricting Access to water – especially for children
Resuscitation
Richard
Do you do anything differently for these cases? With respect to resus? NO
Dry or Secondary Drowning should be treated the same way as a drowning
Quick, effective CPR and transportation to hospital

29. Acknowledgements Professor John Pearn
National Medical Advisor, Royal Life Saving Society - Australia

30. Any questions?