Drowning is a process of respiratory impairment resulting from submersion or immersion in a liquid. It begins when the airway is covered, preventing the exchange of oxygen and carbon dioxide. This immediate respiratory compromise sets in motion a series of physiological responses.
Immediate Bodily Reactions
When submerged, the body’s initial instinct is to hold its breath to prevent water from entering the lungs. This voluntary breath-holding eventually gives way to an overwhelming urge to breathe. As water enters the oropharynx or larynx, a protective reflex called laryngospasm often occurs. This involves the spasmodic closure of the vocal cords and airway, temporarily preventing water from reaching the lungs.
While laryngospasm acts as a protective mechanism, it also prevents air from entering the lungs, leading to oxygen deprivation. For most individuals, laryngospasm eventually relaxes as oxygen levels in the body drop and consciousness fades. Once the airway relaxes, water can then enter the lungs, marking a transition in the drowning process.
Systemic Impact of Oxygen Deprivation
As the body is deprived of oxygen (hypoxia) during drowning, a cascade of events unfolds, impacting major organ systems. The continued lack of oxygen leads to a buildup of carbon dioxide and lactic acid within the bloodstream, resulting in a state of acidosis. This imbalance disrupts normal cellular function.
The brain is particularly vulnerable to oxygen deprivation, with loss of consciousness typically occurring within minutes. Irreversible brain damage can begin after four to six minutes without oxygen. This cerebral anoxia also affects the brain’s ability to control vital functions.
The heart also experiences consequences from the lack of oxygen and increasing acidosis. Initially, the heart rate may slow (bradycardia), and abnormal heart rhythms (arrhythmias) can develop. This physiological stress leads to cardiac arrest, halting the circulation of blood and oxygen to all tissues, which is the primary mechanism of death in drowning.
Water Type Influences
The type of water, whether freshwater or saltwater, leads to distinct physiological differences due to varying osmotic pressures. Freshwater, hypotonic to blood, is rapidly absorbed from the lungs into the bloodstream. This influx can dilute the blood (hemodilution) and may cause red blood cells to swell and burst (hemolysis).
Conversely, saltwater is hypertonic. When aspirated into the lungs, it draws water from the bloodstream and surrounding tissues into the air sacs (alveoli). This fluid shift results in the thickening of the blood (hemoconcentration) and can lead to pulmonary edema.
Despite these physiological distinctions, the immediate clinical management for drowning victims does not differ based on water type. While aspiration of large volumes of either freshwater or saltwater can severely impair lung function, the overriding concern remains oxygen deprivation and its systemic effects. Modern medical approaches focus on restoring oxygenation and circulation regardless of the specific fluid aspirated.
Post-Death Submersion Effects
After death, a body submerged in water undergoes a series of changes influenced by the aquatic environment. The cooling of the body, known as algor mortis, occurs at a rate dependent on water temperature. Livor mortis, the discoloration from blood pooling, and rigor mortis, the stiffening of muscles, can still be observed, though their onset and progression may be altered by the water’s temperature and movement.
Decomposition in water proceeds differently than on land, primarily due to cooler temperatures and a reduced oxygen environment. These conditions slow down the typical putrefactive processes. As decomposition continues, gases produced by bacteria can accumulate, causing the body to bloat and potentially float to the surface.
A unique post-mortem change observed in submerged bodies is the formation of adipocere, also known as “grave wax.” This waxy, soap-like substance forms through a chemical transformation of body fat, and is favored by cold, wet, and anaerobic environments. Adipocere can preserve the body’s contours and features for extended periods.