Drowning occurs when a person experiences respiratory impairment due to submersion or immersion in liquid. This prevents the body from taking in oxygen, leading to a cascade of physiological events. The World Health Organization defines drowning broadly to encompass all incidents, regardless of the outcome.
The Body’s Immediate Reaction
Upon submersion, the body instinctively reacts to prevent water from entering the airways. The first response is often a voluntary breath-hold, as the individual tries to keep water out of the lungs. This is quickly followed by an involuntary reflex known as laryngospasm, where the vocal cords spasm and close tightly. This protective mechanism aims to seal off the airway, preventing water aspiration but also blocking air from entering the lungs. Simultaneously, the mammalian diving reflex may activate, especially in cold water, slowing the heart rate and redirecting blood flow to vital organs like the brain and heart to conserve oxygen.
Oxygen Deprivation and Its Effects
The most significant consequence of drowning is oxygen deprivation, known as hypoxia, which progresses to anoxia, a complete lack of oxygen. Without sufficient oxygen, the body’s cells cannot function properly, and vital organs begin to suffer damage. The brain is particularly sensitive to oxygen scarcity; brain cells can begin to die within minutes, leading to loss of consciousness and potential irreversible neurological damage.
Oxygen deprivation also impacts the cardiovascular system; the heart, deprived of oxygen, may develop irregular rhythms, eventually leading to cardiac arrest. Hypoxia and acidosis, caused by increased carbon dioxide, further compromise heart function. Survival and recovery depend on how quickly oxygen is restored to these organs.
The Role of Water in the Lungs
While the body attempts to seal off the airways, water can still enter the lungs, a process called aspiration. Aspirated water can damage the delicate tissues lining the air sacs, known as alveoli. This damage interferes with surfactant, a substance that reduces surface tension and keeps the alveoli open, making it difficult for the lungs to inflate properly.
Water in the lungs impairs the exchange of oxygen into the bloodstream and carbon dioxide out of it. This can lead to fluid accumulation in the lungs, a condition called pulmonary edema, and can trigger inflammation. Even small amounts of aspirated water can cause breathing difficulties and lung problems that may worsen over several hours following the incident.
Understanding Dry and Wet Drowning
While medical professionals use the single term “drowning,” “dry drowning” and “wet drowning” describe different scenarios. “Dry drowning” refers to situations where severe laryngospasm prevents water from entering the lungs, causing suffocation as air cannot reach them. Conversely, “wet drowning” occurs when water overcomes laryngospasm and enters the lungs, a more common type involving significant fluid aspiration. Despite water’s presence or absence, the ultimate cause of severe injury and death in both scenarios is oxygen deprivation to the brain and other vital organs.