In June 2017, a 4-year-old boy died 1 week after being knocked over and briefly submerged while playing in knee-deep water. This story was widely reported as a case of a rare occurrence called “dry” or “secondary” drowning, depending on the source.1 The media accounts went viral, spreading fear in parents and others learning about these alleged conditions from the news and social media.
Many alleged cases of dry drowning are reported every year, but each has been found to have a recognized medical source that has a legitimate medically recognized diagnosis (which dry and secondary drowning are not).
Drowning is one of the most common causes of death in children, and so we ought to make sure that the information we share about it is accurate, as it is vital to effective prevention, rescue, and treatment.
Unfortunately, medical providers, medical journals, and the mass media continue to disseminate misinformation on drowning.2 These reports often prevail over updated information and hinder accurate understanding of the drowning problem and its solutions.
Every death is tragic, especially the death of a child, and our heartfelt sympathies go out to the family in this alleged drowning case, as well as to all families suffering the loss of a loved one to drowning. However, in the 2017 case, the cause of death was found on autopsy to be myocarditis not related in any way to drowning. As often happens in such situations, this clarification did not receive any media attention, despite the wide reporting and penetration of the original, erroneous story.
We hope our review will reduce misunderstanding among the public and healthcare providers, contribute to improved data collection, and help to promote interventions aimed at prevention, rescue, and mitigation of drowning incidents.
WHAT IS DROWNING?
A consensus committee of the World Health Organization defined drowning as “the process of experiencing respiratory impairment from submersion/immersion in liquid.”3 The process begins when the victim’s airway goes below the surface of the liquid (submersion) or when water splashes over the face (immersion). If the victim is rescued at any time, the process is interrupted, and this is termed a nonfatal drowning. If the victim dies at any time, this is a fatal drowning. Any water-distress incident without evidence of respiratory impairment (ie, without aspiration) should be considered a water rescue and not a drowning.
Rarely do minimally symptomatic cases progress to death, just as most cases of chest pain do not progress to cardiac arrest.4 Nonetheless, rescued drowning victims can deteriorate, which is why we encourage people to seek medical care immediately upon warning signs, as we do with chest pain. For drowning, such warning signs are any water distress followed by difficulty breathing, excessive coughing, foam in the mouth, or abnormal behavior.
A SERIOUS PUBLIC HEALTH ISSUE
Drowning is a serious and neglected public health issue, claiming the lives of 372,000 people a year worldwide.5 It is a leading cause of death in children ages 1 to 14. The toll continues largely unabated, and in low- and middle-income nations it does not attract the levels of funding that go to other forms of injury prevention, such as road safety.
Nonfatal drowning—with symptoms ranging from mild cough to severe pulmonary edema, and complications ranging from none to severe neurologic impairment—is far more common than fatal drowning.6 For every fatal drowning, there are at least 5 nonfatal drowning incidents in which medical care is needed, and 200 rescues are performed.7–10
In the United States, drowning accounts for almost 13,000 emergency department visits per year and about 3,500 deaths.7,8
In Brazil, with two-thirds the population of the United States, drowning accounts for far fewer hospital visits but about twice as many deaths. In Rio de Janeiro, where a highly effective and specialized prehospital service is provided at 3 drowning resuscitation centers staffed by medical doctors, an analysis of the 46,060 cases of rescue in 10 years from 1991 to 2000 showed that medical assistance was needed in only 930 cases (2%).10 The preventive and rescue actions of parents, bystanders, lifeguards, and prehospital rescue services significantly reduce the number of drowning deaths, but these groups do not consistently gather data on nonfatal drowning that can be included in a comprehensive database.
DROWNING IS A PROCESS
When a person in the water can no longer keep the airway clear, water that enters the mouth is voluntarily spit out or swallowed. Within a few seconds to minutes, the person can no longer clear the airways and water is aspirated, stimulating the cough reflex. Laryngospasm, another myth concerning drowning, is presumed to protect the airways but does not, as it is rare, occurring in less than 2% of cases.11,12
If the person is not rescued, aspiration of water continues, and hypoxemia leads to loss of consciousness and apnea within seconds to a few minutes, followed by cardiac arrest. As a consequence, hypoxemic cardiac arrest generally occurs after a period of tachycardia followed by bradycardia and pulseless electrical activity, usually leading to asystole.13,14
The entire drowning process, from water distress to cardiac arrest, usually takes a few minutes, but in rare situations, such as rapid hypothermia, it can go on for up to an hour.15 Most drowning patients have an otherwise healthy heart, and the apnea and hypoxemia precede the cardiac arrest by only a few seconds to minutes; thus, cardiac arrest is caused by the hypoxemic insult and not by ventricular dysrhythmias.6,16
Drowning can be interrupted at any point between distress and death. If the person is rescued early, the clinical picture is determined by the reactivity of the airway and the amount of water that has been aspirated, but not by the type of water (salt or fresh).
Another myth is that drowning in salt water is different from drowning in fresh water. Both salt water and fresh water cause similar surfactant destruction and washout and disrupt the alveolar-capillary membrane. Disruption of the alveolar-capillary membrane increases its permeability and exacerbates shifting of fluid, plasma, and electrolytes into the alveoli.13 The clinical picture of the damage is one of regional or generalized pulmonary edema, which interferes with gas exchange in the lungs.6,13,17
Animal studies by Modell et al showed that aspiration of just 2.2 mL of water per kilogram of body weight is sufficient to cause severe disturbances in oxygen exchange,17 reflected in a rise in arterial pH and a drop in partial pressure of oxygen. The situation must be similar in humans. In a 70-kg person, this is only about 154 mL of water—about two-thirds of a cup.
The combined effects of fluid in the lungs, the loss of surfactant, and the increase in capillary-alveolar permeability can result in decreased lung compliance, increased right-to-left shunting in the lungs, atelectasis, alveolitis, hypoxemia, and cerebral hypoxia.13
If the victim needs cardiopulmonary resuscitation, the possibility of neurologic damage is similar to that in other cardiac arrest situations, but exceptions exist. For example, in rare cases, hypothermia provides a protective mechanism that allows victims to survive prolonged submersion.4,15
The duration of submersion is the best predictor of death.18 Underwater, people are not taking in oxygen, and cerebral hypoxia causes both morbidity and death. For this reason, reversing cerebral hypoxia with effective ventilation, oxygen, and chest compression is the priority of treatment.