Drowning

20th January 2021

To begin with, let’s just forget “near-drowning”, “dry drowning”, “wet drowning”, “freshwater drowning”, “saltwater drowning” and “secondary drowning”.

These terms are outdated and no longer accepted (1) by The World Health Organization (2), the United Kingdom Resuscitation Council (3), International Liaison Committee on Resuscitation (4) , the Wilderness Medical Society (5) , the International Lifesaving Federation (6), the American Heart Association (7) who all discourage the use of these terms.

Unfortunately, these terms still slip past the editors of medical journals, allowing their use to be perpetuated. These terms are most pervasive in the nonmedical press and social media to add an illusion of gravitas, where the term drowning seems to be synonymous with death.

The currently accepted definition of drowning from the World Congress on Drowning (8)  is:

“Drowning is the process of experiencing respiratory impairment from submersion or immersion in a liquid.”

Key to this are:

• Drowning is a process, not the end result.  The definition of drowning does not include death.

• There must be respiratory impairment.   If a casualty is rescued from the water with no respiratory distress, they did not drown or ‘near drowned’, they were simply rescued.

• Submersion occurs where the whole body is submerged, including the airway.  Immersion is where the body is within a liquid but not covering the airway.

• Drowning is limited to liquids.   Casualties submersed in powders (which behave as free-flowing fluids) are asphyxiated.

Once it is determined a drowning incident has occurred, there are 3 possible outcomes (8):

• Mortality (death)

• Morbidity (illness or injury)

• No morbidity

Drowned casualties either die as a result of respiratory impairment,  are rescued with consequential illness or injury following their respiratory impairment or have no illness or injury as a result.

The Process of drowning

 Stage 1: Cold Water Immersion Response (0-2 minutes):

Sudden immersion in cold water causes an immediate fall in skin temperature which triggers several body reflexes (9) collectively (and annoyingly) known as the “cold-shock” response, and they last for just the first few minutes after falling in. 

The cold water immersion responses include:

1. spontaneous gasping for air

2. sudden increase in breathing rate

3. sudden increase in heart rate

4. sudden increase in blood pressure

5. dramatic decrease in breath-holding time (from around 60 seconds to just 20-25 seconds (10).

A combination of gasping and a decreased ability to hold one’s breath causes the casualty to inhale water.  And this is the fundamental cause of drowning – respiratory distress.

Inhaling water appears to cause laryngospasm in the first instance (although this is debated) but real problems occur when water enters the lower airway, in particular, the alveoli; only a small amount of water is required to cause significant problems – less than 4ml/kg (11,12).

• Regardless of the salinity of the water, the inflammatory response leads to increased permeability of alveoli capillary membrane and exacerbates fluid, plasma and electrolyte shifts into the alveoli resulting in pulmonary oedema leading to decreased oxygen and carbon dioxide exchange and some bronchospasm.

• Water in the alveoli also causes surfactant washout and dysfunction, leading to reduced lung compliance and alveoli collapse.

The fundamental cause of death from drowning is hypoxia, leading to arrhythmias and cardiac arrest.

It is for this very simple reason that lifejackets and PFD save lives by keeping the airway above the water during the first few minutes of uncontrolled breathing. 

Shallow Water Blackout

A combination of inhaled water and hyperventilation might, at this stage cause shallow water blackout:

Ordinarily, as we hold our breath our oxygen levels are decreasing whilst our carbon dioxide levels are increasing.   The desire to breathe is triggered by elevated CO2 levels which usually occurs before our O2 levels drop below a particular threshold at which point we go unconscious or ‘blackout’.

If the casualty has been hyperventilating, they have a normal amount of oxygen in their bloodstream but vastly reduced CO2 levels.  As they attempt to hold their breath, they reach the low 02 thresholds of blackout before their raising C02 levels have triggered a desire to breathe.

Stage 2: Functional Disability (2-30 minutes)

If the casualty has survived the ‘cold-shock’, rapid cooling of the muscles reduces contractility preventing normal muscle movement; the casualty may be unable to swim or may have lost manual dexterity preventing them from grasping rescue lines or ordinarily climbing out.

It is this loss of muscle control which is why drowning may not appear as drowning (13):

• A drowning casualty may not be physiologically able to call out for help due to uncontrolled breathing.

• A drowning casualty may not wave for help, as their instinct or priority is to use their arms to keep their airway above the water.

These casualties may be conscious but rescued with respiratory distress and hypoxia.

Stage 3:  Hypothermia (> 30 minutes).

After prolonged exposure, the casualty will become hypothermic.  Unconsciousness can be expected when the core temperature reaches 30-32oc but even in very cold water this can take over an hour to achieve.  If the casualty was not wearing a life jacket or PFD, it is likely they died of drowning rather than hypothermia.  If the casualty’s airway is protected by a life-jacket and they are breathing normally, they are not a Drowned casualty, they are a hypothermic casualty and should be treated as such.

Further reading - Hypothermia

To rescue or not?

National Operation Guidance decision tool (14) based on the work of Dr Mike Tipton (15) is a model is designed to give casualties every reasonable chance of rescue and resuscitation and is balanced against the risk of harm to responders when carrying out rescues.

The length of time submerged and the temperature of the water are the two main factors determining survivability:

• Generally, the longer a casualty is submerged and the warmer the water, the lower the chances of survival due to hypoxia.  

• Casualties have a longer survival time in very cold water due to the protective measures of hypothermia reducing the body’s requirement for oxygen.

Further considerations include the age and / or size of the casualty, as smaller and/or younger people can survive longer than larger people or adults.

1.  Start The Clock
The main factors are the length of time the casualty has been submerged and the water temperature.  It is not possible to know for certain when a casualty became submerged, so the clock should start when the first responder arrives on the scene.  It should not be assumed that the person has been submerged for longer than this.

2.  Risk Assess
A risk assessment should balance the likelihood of casualty survival and the likelihood and severity of harm to rescuers.  The decision will consider whether an immediate rescue can be started or if one should await specialist resources.

3.  At 30 minutes
If rescue has commenced, a further Risk Assessment should be considered given the reduced likelihood of survival combined with a revision of the danger to rescuers which may be increased due to darkness, cold, exposure, fatigue, changing tides or river levels, for example.

If the water is ‘icy-cold’ (below 7oc) the casualty should be considered survivable, although the likelihood of survival reduces as time passes.  If not, the operation should move to the recovery of the body, if it is considered safe to do so.

4.  At 60 minutes
If rescue operations have continued at 60 minutes a further assessment should be made.  If the water is ‘icy-cold’ and the casualty is known to be young and/or small they should be considered survivable, although again their chances are further reducing as time passes. The risk assessment should be revisited to decide if a rescue should continue or if the incident should switch to body recovery.

5.  At 90 minutes
After 90 the decision should be taken to switch to body recovery because the circumstances are regarded as no longer survivable.

Rescue of the casualty

• Avoid entry into the water whenever possible. If entry into the water is essential, use a buoyant rescue aid or flotation device.

• Remove the victim from the water and start resuscitation as quickly and safely as possible.

• Cervical spine injury is uncommon in drowning victims (approximately 0.5%). Spinal immobilisation is difficult in the water and delays removal from the water and adequate resuscitation of the victim.

• Consider cervical spine immobilisation if there is a history of diving, water slide use, signs of severe injury, or signs of alcohol intoxication.

• Despite the potential spinal injury, if the victim is pulseless and apnoeic remove them from the water as quickly as possible (even if a back support device is not available) whilst attempting to limit neck flexion and extension.

• Try to remove the victim from the water in a horizontal position to minimise the risks of post-immersion hypotension and cardiovascular collapse.

Ventilation (3)

• Prompt initiation of rescue breathing or positive pressure ventilation increases survival. If possible supplement ventilation with oxygen.

• Give five initial ventilations as soon as possible.

• Rescue breathing can be initiated whilst the victim is still in shallow water provided the safety of the rescuer is not compromised.

• If the victim is in deep water, open their airway and if there is no spontaneous breathing start in-water rescue breathing if trained to do so.

• In-water resuscitation is possible, but should ideally be performed with the support of a buoyant rescue aid.

• If normal breathing does not start spontaneously, and the victim is less than 5 min from land, continue rescue breaths while towing.  If more than an estimated 5 min from land, give rescue breaths over 1 min, then bring the victim to land as quickly as possible without further attempts at ventilation.

Regurgitation (3)

• Expect the casualty to vomit.

• If regurgitation occurs, turn the victim’s mouth to the side and remove the regurgitated material

• There is no need to clear the airway of aspirated water as this is absorbed rapidly into the central circulation.

• Do not use abdominal thrusts or tip the victim head down to remove water from the lungs or stomach.

Chest compressions (3)

• As soon as the victim is removed from the water, check for breathing. If the victim is not breathing (or is making agonal gasps), start chest compressions immediately.

• Continue CPR in a ratio of 30 compressions to 2 ventilations.

• Most drowning victims will have sustained cardiac arrest secondary to hypoxia. In these patients, compression-only CPR is likely to be less effective and standard CPR should be used.

   

Post Rescue Care

After Drop

A phenomenon known as “After Drop” can occur as a result of aggressive rewarming; peripheral vasodilation can lead to a redistribution of blood and a drop in core temperature.  This can occur during treatment or even after recovery.   This can be prevented by moderated warming techniques;   If the casualty has vital signs, is insulated and immobilise, there is no rush to actively warm them.

Circum Rescue Collapse

Particularly evident in immersion hypothermia casualties, ‘Circum Rescue Collapse’ has been attributed to the aggressive repositioning of the casualty from a floating horizontal position to vertical as they were winched out of the sea using a hoist.  Standing up quickly can cause orthostatic hypotension; a drop in blood pressure as the vascular system cannot constrict fast enough in the lower limbs and abdomen to squeeze oxygenated blood up to the brain; this is noticeable by the ‘head rush’ or feeling of light-headedness as the brain is momentarily deprived of oxygen. 

Combined with the immediate loss of hydrostatic pressure which was being exerted on the body whilst the casualty was immersed, this drop in blood pressure can reduce cerebral perfusion to the point of unconsciousness and cardiac perfusion to the point of cardiac arrest.

Both immersion and severely hypothermic casualties are now rescued horizontally and as such, should remain in this position until rescue.

References

1. Hawkings JC, Sempsrott J and  Schmidt A  (2016) “Drowning in a Sea of Misinformation: Dry Drowning and Secondary Drowning”  Emergency medicine News.  https://journals.lww.com/em-news/blog/BreakingNews/pages/post.aspx?PostID=377  Accessed 19th January 2021
   

2. https://www.who.int/en/news-room/fact-sheets/detail/drowning
   
   

3. UK Resuscitation Council  (2019)  “Cardiac Arrest in Special Circumstances” in Advanced Life Support Guidelines.  Ch 12.  113:142
   
   

4. Idris AH, Berg RA, Bierens J, Bossaert L, Branche CM et al (2003)  “Recommended Guidelines for Uniform Reporting of Data From Drowning”.  Circulation.  108[20]:2565
   
   

5. Schmidt AC, Sempsrott JR, Hawkins SC, Arastu AS, Cushing TA, Auerbach PS.  (2016)  “Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Drowning”.  Wilderness and Environmental Medicine. June;27(2):236-51.
   
   

6. Szpilman D, Pearn J, Queiroga AC  (2019)  “Medical Position Statement MPS 22 – Research Needs for Drowning”.  International Lifesaving Federation Rescue Commission 28/08/2019.  https://www.ilsf.org/wp-content/uploads/2020/01/MPS-22-2019-Research-Needs-for-Drowning.pdf  Accessed 19th January 2021
   
   

7. American Heart Association (2005)  “Drowning”.  Circulation. 112(2)  Supp. 13.  IV-133-IV-135.
   
   

8. International Lifesaving (2015)  “World Conference on Drowning Prevention 2015 – Malaysia:  Program and Proceedings”.  ILS.  https://www.ilsf.org/wp-content/uploads/2018/11/WCDP2015_ProgramProceedingsLR.pdf  Accessed 19th January 2021
   
   

9. Datta A and Tipton M  (2006)  “Respiratory responses to cold water immersion: neural pathways, interactions, and clinical consequences awake and asleep”.  Journal of Applied Physiology.  100:6, 2057-2064
   
   

10. Giesbrecht G.  (2000)  “Cold stress, near drowning and accidental hypothermia: A review”.  Aviation, Space, and Environmental Medicine. 71. 733-52.
    
    

11. Matthew JA.  (2016) “Submersion and Diving-Related Illnesses”. In: David S. (eds) Clinical Pathways in Emergency Medicine. Springer, New Delhi.
    
    

12. Schmidt AC, Sempsrott JR, Hawkins SC, Arastu AS, Cushing TA, Auerbach PS.  (2016)  “Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Drowning”.  Wilderness and Environmental Medicine.  Jun;27(2):236-51.
    
    

13. Vittone M and Francesco A.  (2006)  “Drowning doesn’t look like drowning”.  On Scene – the Journal of U. S. Coast Guard Search and Rescue.  Fall.  P.14.  https://mariovittone.com/wp-content/uploads/2010/05/OSFall06.pdf  Accessed 19th January 2021
    
    

14. National Operational Guidance:  Water Rescue and Flooding”.  National Central Programme Office.  https://www.ukfrs.com/pdf/print/node%3A20802  Accessed on 9th January 2021
    
    

15. Tipton MJ, Golden FS.  (2011)  “A proposed decision-making guide for the search, rescue and resuscitation of submersion (head under) victims based on expert opinion”.  Resuscitation.  Jul;82(7):819-24