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The Process of Drowning – A Deeper Look at Drowning

Despite the basic concepts of ‘drowning’ being relatively common knowledge for some time, there remains areas of incomplete understanding, and or good quality data to support these long-standing beliefs. There are also varying recommendations for treatment of a drowning patient, appearing in various documents and from various authorities around the world.  Driven by Evidence Based Research, Raven Medical has decided to investigate the details regarding drowning, in hopes to confirm the best possible treatment guidelines for prehospital care of a drowning patient in the wilderness, tactical, or rescue setting. 

Len James, Raven Medical Curriculum Director, has made some interesting findings by examining existing study results, as well as adding concepts from some cutting-edge research. These preliminary findings are providing First Responders with a better understanding of drowning.

What is Drowning?

The current definition is:  Drowning is the process of experiencing respiratory impairment from submersion/immersion in liquid. 

Drowning outcomes are classified as Death, Morbidity (The condition of suffering from a medical condition), or No Morbidity. 

This definition was agreed upon by the World Health Organization in 2005, and eliminated the use of terms such as “dry drowning”, “secondary drowning” etc. All events, are to be referred to strictly as “Drowning Events”. 

To view drowning strictly as a process is an oversimplification. Drowning in reality is a complex network of

  1. Environmental Inputs
  2. Physiological Responses, and
  3. Conflicting Compensation Mechanisms

This network in turn causes three stages in a drowning event:

  1. Inputs
  2. Impacts
  3. Consequences

Strainers & Sweepers

Objects like trees are hazards while navigating the river whether they are in the water or the branches are hanging over top. These hazards should be avoided when on the water and can lead to drowing if they can not be avoided.

Let’s have a closer look at the inputs to a body, when it is immersed (head / face above the surface) in water. For the purpose of this article, water will be considered to be cold, or less than 15 degrees Celsius.

The three primary inputs to the Drowning Process are:

1. The Cold Water Shock

1. The Cold Water Shock

This is the strongest input by far. Cold water stimulates the pain receptors in the skin, causing a sudden increase in Sympathetic Nervous System activity (including an increased heart rate, elevated blood pressure, and accelerated respiration rate). Additionally, it triggers a gasping reflex, leading to immediate hyperventilation. The gasp reflex can overpower any ability to hold one’s breath and may last for 1-2 minutes. Lastly, the cold water shock induces peripheral vasoconstriction, resulting in a substantial change in the body’s blood flow.

2. Fear and Anxiety

2. Fear and Anxiety

The most common emotional state reported by drowning survivors is fear. Fear leads to a panic attack. There is good research to show that patients experiencing a panic attack cannot perform simple motor skills, contributing to the loss of swimming ability. It can also decrease the ability to solve problems or make good decisions.

Panic attacks also stimulate the Sympathetic Nervous System, further causing an increase in heart and respiration rates.

3. Cold Arms

3. Cold Arms

Another interesting input is the muscular impairment brought on by the rapid cooling of the arms. Due to the high surface area to mass ratio, it is thought that the arms cool faster than the rest of the body. This rapid muscle cooling leads to neuromuscular blockage and the loss of purposeful movements. Video analyses of drowning patients have documented unique, ineffective swimming motions, and a loss of the ability to grasp onto a buoyancy aid.

Three additional inputs are present when the patient is submerged in water (head /face below the surface)

4. Face in water. 

4. Face in water. 

The Cold Shock response is the most important input when the patients face is above the water surface, and face in the water is the most important input when the face is below the surface. There is still much we do not fully understand, but in humans, if water is splashed onto the face, or the face is submerged, a unique chain of events occurs, this is known as the Mammalian Dive Reflex. There are three components to this reflex: Breath holding, Parasympathetic Nervous System activation, and peripheral vasoconstriction.

5.Breath Holding.

5.Breath Holding.

There are two impacts on the body when we examine breath-holding through the lens of a drowning input. First, someone struggling to hold their breath will experience laryngospasms, wherein the vocal cords close off the airway. As part of this, a person will also experience unconscious swallowing, referred to as the swallowing reflex. The second and more consequential impact is an increase in the parasympathetic nervous system. This is important as it combines with the mammalian dive reflex but conflicts with the cold shock response.

6. Water in the Mouth. 

6. Water in the Mouth. 

As we have just learned, water in the mouth triggers the Laryngeal Closure reflex, or Laryngospasm. As a result of water in the mouth, a swallowing reflex clears the mouth of water, resulting in a large volume of water entering the stomach. Cold water in the mouth also has a significant cooling effect on tissue, and can increase the rapid cooling of the brain.

These six inputs form a complex network that can result in serious injury or drowning death.

Now, let’s examine how the body’s physiological responses to these inputs can conflict with each other, thereby making the process of drowning so complex.

There are 4 main conflicts:

1. Gasping Reflex  vs. Breath Holding

During the struggle of breath holding, the primary urge to breath comes from the respiratory muscles. However, once the breathing centre in the brain detects high carbon dioxide, the urge to breath increases and causes involuntary breath. The Gasping reflex, causing rapid breathing and hyperventilation, and thus conflicts with breath holding by drastically shortening the time to the ‘breaking point’, or the moment of involuntary breathing, or a gasp. Even the volume of a single gasp is enough to be fatal to a submerged patient. Here’s the conflict: the brain is telling the patient to hold their breath, but the body to telling the patient to gasp and breath. For a short time, this protects a patient’s airway, but only for a few seconds, and eventually the gasping will win. 

2. Remaining Calm vs. Fear and Anxiety

Emotional contributions to drowning are the least studied and most poorly understood; however, there is evidence that it plays a role in the process. Studies have revealed that in disasters at sea, a disproportionate number of young, healthy, fit adult patients died, while other older and less fit adults survived. This was attributed to the survivor mindset and is now thought to be a very significant survivability factor. Fear can paralyze a patient, while anger and panic can lead to poor decision-making. Those who can control their emotional state have a better chance of surviving.

3. Shell (cold arms) vs. Core (cold water in the mouth)

In Shell vs. Core, we are really talking about built-in adaptive mechanisms to protect the brain. For the shell, let’s examine the role that the arms play. The arms cool at a faster rate due to the mass-to-surface area ratio, and coupled with the initial cold shock response, motor control of the arms rapidly disappears. This leads to the inability to swim or self-rescue. In cold water, after 10-20 minutes, the arms will lose all function. The other aspect is the vasoconstriction caused by cold shock, leading to a lack of oxygen supply to the muscles, contributing to swim failure. This preserves the body core by keeping warm, oxygen-rich blood flowing to the vital organs. However, new research is showing us that the core temperature is not uniform, and there can be significant temperature differences between the abdomen and the brain. The brain is selectively cooled faster than the other core organs, enhanced by cold water in the oral cavity. This cooling of the brain is thought to be neuroprotective, providing a possible mechanism for brain survival.

4. Cold Shock vs. Mammalian Dive Reflex

For the final conflict, we will revisit the Cold Shock response and how it reacts against the Mammalian Dive Reflex, initiated when a patient’s face is in the water. In addition to early discussions about Cold Shock and the increase in the sympathetic nervous system, Cold Shock also elevates the heart rate and force of contraction of the heart muscles, increasing cardiac output. Now, when a patient’s face is in the water, this stimulates the mammalian dive reflex. This reflex is strongest in children and weaker in adults but is still present. This reflex stimulates the parasympathetic nervous system, which slows down the heart or reduces cardiac output. So, the heart is simultaneously receiving opposing signals. This has been labeled as autonomic conflict. This can have devastating consequences on cardiac function. In studies, 80% of patients experienced an unusual heart rhythm or arrhythmia. In some cases, the rhythm would oscillate between fast and slow. In some cases, this can be the stressor that causes sudden cardiac arrest in cold water immersion patients. Patients with pre-existing heart conditions are at a much higher risk for sudden cardiac arrest.

So, to summarize. As we look closer at the drowning process, we now know that there are 6 inputs that lead to drowning. To understand these further, we looked at how these inputs can conflict with each other.  Finally, let’s look at the consequences and timelines of the drowning process. 

Let’s assume an adult is submerged in cold water. 

0-6 Seconds

All is good. A patient can hold their breath even under stress. This will not last long… 

0-6 Seconds

6 – 10 seconds.

Gasping takes over due to the cold shock response. If the person is submerged, the first gasp will have a volume of 1-2 Litres, which is sufficient volume to damage the lungs leading to hypoxia, and unconsciousness, and shortly after, cardiac arrest will follow. 

6 – 10 seconds.

10 seconds – 2 minutes.

It is estimated that 60% of drowning victims will experience a cardiac arrest within the first 2 minutes of submersion. There are 4 possible causes; Gasping leading to hypoxia, Autonomic Conflict leading to arrhythmia, Fear and Panic leading to poor decisions, and water in the mouth and stomach making a patient less buoyant and leads to rapid cooling of the brain resulting in unconsciousness.

10 seconds – 2 minutes.

2-10 minutes.

If a patient does not go unconscious or experience a cardiac arrest in the first 2 minutes, they have made it to the onset of swim failure phase of drowning. During this time, the gasping and sympathetic nervous system response slows, and the arms have not yet cooled to the point of swim failure. Environmental inputs can drastically alter this timeline. During this phase, rescues are most successful.

2-10 minutes.

10-20 minutes.

The sympathetic nervous system surge is waring off, and the arms have cooled to the point of reduced strength or swim failure. Core temperature remains stable. During this time frame, a patient is unable to participate in the rescue efforts due top neuro muscular block from the cold.

10-20 minutes.

20-60 minutes.

The onset of hypothermia phase. The muscles in the extremities are not able to function including for the purposes of shivering to generate heat. This results in a drop in core temperature. Approximately 20% of drowning deaths are due to hypothermia .

20-60 minutes.

Circum-rescue collapse.

Circum-rescue collapse is the sudden onset of unconsciousness or Cardiac Arrest in a patient during the process of being rescued. Twenty percent of drowning fatalities happen during Circum-rescue phase. There are 2 key components: ‘afterdrop’, and ‘hemodynamic instability’. Afterdrop is the increased cooling of the body core temperature caused by colder blood in the periphery returning to the core. This can be attributed to increased movement during a rescue. As a result, colder blood, often containing higher than usual levels of metabolic waste products, causes cardiac irritability and can lead to cardiac arrest. When a patient is removed from the water, hydrostatic squeeze that is exerted on a patient while in the water is lost, resulting in a drop in blood pressure. One final aspect of afterdrop is the relief that a patient may feel when rescue is near. This causes a calming of the nervous system, and allows the parasympathetic nervous system to dominate, leading to unconsciousness.

Understanding the physiological responses that a drowning patient experiences is key to selecting the best rescue tactic and providing the best possible pre-hospital care. Factors such as age, fitness, and environment, coupled with the drowning inputs, form the basis for all medical treatment guidelines and tactical decision-making tools. This research is ongoing, and we encourage all rescuers and responders to stay up-to-date on the latest best practices and available research results. To learn more, you can also sign up for a Raven Medical course.

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Research compiled by Len James, Raven Medical Curriculum director.

Len James

Len James

Len has been teaching wilderness medical programs since the mid 1980’s. Len has taught course in 10 countries around the world. From “north of 60” and South America, to teaching the first wilderness medical program in China, he enjoys adopting medical training programs to meet the needs of diverse students.