Drowning

Introduction

The Act of Drowning
Contrary to how it is often depicted in movies, the act of drowning often goes unnoticed. There appear to be three separate actions or body positions people adopt when confronted with the possibility of drowning. Depending on their swimming ability, injuries, or illnesses, some will progress through all three of these stages, while others will not.

1. Those who have some swimming ability (perhaps due to a flotation device) often call for help and are able to actively aid in their rescue. They may be vertical (treading water) or horizontal (actively swimming). 
2. Those who are unable to help themselves assume a vertical position in the water with their arms flailing laterally in a futile attempt to keep their head above water; most do not kick with their legs. They will alternately sink below the surface of the water and reappear. Their mouths are not above the surface of the water long enough for them to speak or breathe and they will quickly sink, usually within 30-60 seconds. They are unable to wave, call for help, or actively aid in their rescue.
3. Those who are unresponsive tend to float on or below the surface of the water.   

​Drowning
In drowning, the victim is submerged under or immersed in water and requires rescue or assistance; not all drowning victims are unresponsive during their rescue; they may be awake, voice responsive, or pain responsive.

Drowning is a process with three possible outcomes:

1. Death
2. Survival with brain damage
3. Survival without brain damage

Ultimately, drowning patients die from a lack of oxygen. Our lungs cannot extract oxygen from water.

Anatomy & Physiology

The lungs are essentially tubes that either contain air or blood.

• The air tubes (bronchioles, bronchi, trachea) terminate in small air sacs (alveoli) where the gas exchange takes place.
• The tubes and air sacs are attached to one another by elastic connective tissue and surrounded by a membrane (pleura).
• The walls of each alveolus are one cell thick and fragile.

• Type 1 alveolar cells are curved and comprise the majority of the surface area of each alveolar sac.
• Type 2 alveolar cells are squarish and release surfactant. Surfactant covers the interior surface of each alveolus and lowers the surface tension where the air interfaces with the alveolar wall; it acts to prevent alveolar collapse at the end of each expiration.
• Large white blood cells (macrophages) roam the interior of the alveoli; they attack and destroy any foreign debris or organisms.

Pathophysiology

Contrary to popular belief, very little water enters the lungs of most drowning victims:

• The majority of non-fatal drowning patients aspirate less than 30 ml (or 1 oz) of water.
• During the autopsy of fatal drowning patients only 1-2 ml/kg of water is typically found in in the lungs; For example, a 200 pound (or 90 kg) person will only aspirate between 90-180 ml (or 3-6 oz).

                                              Why so little?

When water enters the drowning victim's mouth and nose, their epiglottis immediately closes and covers the trachea and they reflexively swallow. As a result, literally liters of water has been found in the stomachs of fatal drowning victims. This reflexive protection typically remains intact until the patient becomes runs out of oxygen and gasps for air or becomes unresponsive, and even then, little water actually enters the victim's lungs.

Unfortunately, it doesn't take much aspirated water to cause problems and interfere with the gas exchange in the alveoli. Patients who have a pulse and are breathing after rescue or resuscitation, may develop respiratory complications severe enough to cause death minutes to hours after the incident if they aspirate enough water.

Aspirated water irritates the lining of the lower airway and is absorbed by the alveolar capillaries. As the process unfolds it contributes to hypoxemia (low blood oxygen):

• Irritating the lining of the bronchioles causes inflammation and bronchial constriction (similar to asthma).
• Disrupting and washing out the surfactant eventually leads to alveolar collapse.
• Damaging the alveolar-capillary interface causes inflammation and subsequent dilatation of the pulmonary capillaries causing plasma to leak into the alveoli.
• As surfactant mixes with the plasma, foam is created and issues from the patient’s mouth and nose.

• Oxygen and overall metabolic requirements in some patients may be lowered by immersion in cold water (< 68° F/20° C) due to core hypothermia or a diving reflex and preserve brain & organ function for 30-90 minutes.
• The amount of central nervous system damage—due to lack of oxygen and corresponding acidosis (high carbon dioxide levels)—will determine the patient’s ultimate outcome.
• If the period of oxygen loss is limited, the acidosis minimal, or the victim rapidly develops core hypothermia (or a diving reflex), the damage may be limited and the patient may recover with no or only minor neurologic sequelae.

Basic Life Support Assessment & Treatment

• If the patient is not breathing, begin rescue breathing; focus on getting oxygen to the patient’s brain ASAP. Start with five rescue breaths; patients typically respond after a few breaths; trained rescuers should consider rescue breathing while the patient is in the water. The epiglottis is attached to the tongue—combine the head-tilt, chin-lift, & jaw thrust maneuvers when rescue breathing to ensure airway is open.
• Begin immediate CPR if the drowning victim is pulseless and not breathing if they have been submerged for less than 30 minutes in water warmer than 43º F (6º C) and less than 68º F (20º C) or those submerged for less than 90 minutes in colder water. Start with five rescue breaths and continue alternating 30 compressions and two breaths. Less than 10% of drowning patients need defibrillation.
• Use supplemental oxygen if it's available and you are trained in it's use. If the patient is V,P,U assist their breathing using a bag valve mask or connect oxygen to the oxygen port in a simple face mask. If the patient is awake, use a non-rebreather mask or nasal cannula.
• Consider stopping resuscitation efforts after 30 minutes.
• If the patient is VPU and trauma is a potential MOI, support the patient's spine during rescue and transport; however, spinal support should not delay resuscitation efforts.
• Anticipate foam issuing from the patient’s the mouth and nose (right) or vomiting during resuscitation: Breathe through the foam; roll and suction any true vomit or water.
• Treat for hypothermia as necessary.

Follow up Assessment, Treatment, & Evacuation

• Continue to treat for hypothermia as necessary.
• Be prepared for vomiting.
• Rule out traumatic problems as usual in awake patients.
• Even with poor water quality, patients who self-rescue are typically at low risk of developing pulmonary edema (0.6-5%). If a patient is asymptomatic with no S/Sx of respiratory distress and a normal mental status, no evacuation is needed.
• Begin a Level 3 evacuation for patients who present with mild S/Sx post rescue that do not immediately resolve—mild respiratory distress, rales, abnormal mental status—or those that present with foam in their upper airway. Monitor for six hours; if S/Sx worsen, upgrade to a Level 2 evacuation.
• Begin a Level 2 evacuation for all awake and asymptomatic patients after a successful resuscitation (CPR or rescue breathing); upgrade a to a Level 1 evacuation if the patient presented with foam in their upper airway and presented with or develops a severe cough, moderate or severe respiratory distress, or low blood pressure.
• Although poor water quality increases the chance for pulmonary edema and subsequent respiratory infections in non-fatal drownings, prophylactic antibiotics are not recommended.  Antibiotic treatment should be considered if the patient is symptomatic—fever, increased sputum, and abnormal lung sounds—days after the initial event.

---

Interested in learning more about wilderness medicine? Take one of our wilderness medicine courses. Guides and expedition leaders should consider taking our Wilderness First Responder course.

Looking for a reliable field reference? Consider consider purchasing one of our print or digital handbooks; our digital handbook apps are available in English, Spanish, and Japanese. Updates are free for life. A digital SOAP note app is also available.