Drowning is a process of respiratory impairment resulting from submersion or immersion in liquid. It involves a sequence of events that can lead to death, or to non-fatal outcomes with or without injury. This process begins the moment a person’s airway is covered by liquid, preventing them from breathing air.
The Body’s Initial Response
Upon submersion, the body instinctively reacts to the presence of water. An initial period of voluntary breath-holding occurs, lasting for about a minute until the urge to breathe becomes overwhelming. During this phase, water may be swallowed.
The entry of water into the mouth and throat can trigger a reflex known as laryngospasm. Laryngospasm involves the involuntary closing of the vocal cords, which can temporarily prevent water from entering the lungs. This protective mechanism, however, also stops air from entering the lungs, contributing to oxygen deprivation.
The Impact of Oxygen Starvation
As oxygen levels in the blood decrease and carbon dioxide levels rise, the laryngospasm may eventually relax, or it may not occur at all in some cases. When this happens, water can be aspirated into the lungs. The presence of water in the lungs interferes with the normal process of gas exchange.
Water in the lungs can wash out or damage surfactant, a substance that helps keep the tiny air sacs (alveoli) in the lungs open. This damage leads to a reduction in blood oxygen levels (hypoxemia) and eventually a complete lack of oxygen in the tissues (anoxia). Brain cells, in particular, are highly sensitive to oxygen deprivation and cannot survive long without it.
Organ System Failure
Prolonged oxygen deprivation has severe consequences for the body’s organ systems. The brain, which has a high demand for oxygen, is particularly vulnerable. Brain cells can begin to die within four to six minutes without oxygen. This cellular damage can lead to loss of consciousness and, if oxygen is not restored, irreversible brain injury.
The heart is also significantly affected by the lack of oxygen. As hypoxemia worsens, the heart muscle weakens and its electrical activity can become unstable, leading to irregular heartbeats (cardiac dysrhythmias). Ultimately, the heart may stop beating entirely, a condition known as cardiac arrest. This cessation of blood circulation prevents the transport of any remaining oxygen to the brain and other organs.
Variations in Drowning Mechanisms
While oxygen deprivation is the ultimate cause of death in all drowning incidents, the mechanisms leading to it can vary. “Wet drowning” occurs when water enters the lungs, which directly disrupts lung function and gas exchange.
“Dry drowning” refers to situations where laryngospasm persists, preventing water from entering the lungs. Despite the absence of water in the lungs, oxygen deprivation still occurs due to the airway being closed, leading to death from asphyxia. Although these terms are sometimes used, current medical consensus often categorizes all these events simply as “drowning” as the underlying cause of harm remains oxygen deprivation.
“Secondary drowning,” sometimes called “delayed drowning,” describes a situation where symptoms appear hours after the initial water exposure. This happens when a small amount of water enters the lungs, causing irritation, inflammation, and fluid buildup (pulmonary edema) over time. Even a small amount of aspirated water can significantly impair lung function, leading to delayed respiratory distress and oxygen deprivation.