Drowning is defined as the process of experiencing respiratory impairment from submersion or immersion in a liquid. The life-threatening event is the inability to breathe, which leads to a lack of oxygen reaching the brain and other organs. Airway compromise—the blocking of the passage for air—is the immediate danger, and it can occur through various physical and physiological mechanisms. The obstruction of the airway can happen rapidly through the body’s own protective reflexes, the introduction of foreign materials, or structural issues related to trauma.
Immediate Physiological Blockage
The body’s involuntary defense mechanisms can cause an immediate and severe closure of the airway. The most well-known of these is laryngospasm, which is a reflexive, sustained tightening of the vocal cords in the larynx. This spasm occurs when water, even a small amount, contacts the sensitive tissues of the throat or vocal cords, causing them to clamp shut in an attempt to block fluid entry into the lungs.
This response can completely seal the airway, preventing both water and air from passing. While the reflex is intended to be protective, a prolonged spasm leads to asphyxiation because no oxygen can be inhaled. In many cases, the spasm relaxes as the victim loses consciousness due to oxygen deprivation, allowing water to enter the lungs, but the initial closure is itself a mechanism of compromise.
A secondary physiological blockage occurs with the loss of consciousness. As the brain becomes starved of oxygen, the muscles in the jaw and throat relax completely. This relaxation causes the tongue to fall backward against the posterior pharyngeal wall, physically obstructing the upper airway. This mechanical blockage from the tongue is a common cause of respiratory distress in any unconscious person.
Obstruction by Internal and External Materials
The airway can be physically blocked by materials originating from the victim’s body or the surrounding environment. One of the most significant internal obstructions is the aspiration of gastric contents, which is common during drowning incidents. The stress of the event, the ingestion of water, and the body’s lack of oxygen often trigger vomiting. This vomitus, containing food particles and acidic stomach fluid, can be forcefully inhaled, or aspirated, into the lungs.
Aspiration of these materials causes severe inflammation and chemical injury to the lung tissue, leading to respiratory failure. The thick particulate matter can also cause a direct, physical blockage of the bronchioles. Rescuers must be prepared to manage this possibility, as the presence of gastric contents greatly complicates attempts at ventilation.
External materials are another source of blockage, particularly in natural bodies of water. The struggle of the victim can lead to the inhalation of foreign debris, such as sand, mud, silt, seaweed, or small aquatic objects. These materials become lodged in the upper or lower airways, creating a physical barrier to airflow and contributing to the overall respiratory impairment.
Positional and Traumatic Airway Compromise
Structural injuries and body positioning can compromise a drowning victim’s airway. The possibility of an associated traumatic injury, such as a cervical spine injury, is a major concern, particularly in high-impact incidents like diving into shallow water or falls from height. When the head and neck are improperly moved, a fractured or dislocated vertebra can injure the spinal cord, leading to paralysis that affects breathing muscles.
Even without a spinal cord injury, improper head positioning can physically distort the airway’s anatomy. The head and neck must be kept in a neutral, in-line position, especially during rescue and removal from the water, to maintain an open passage for air. Tilting the head back or forward can severely pinch or obstruct the trachea and pharynx. Rescuers are trained to maintain spinal motion restriction when there is any suspicion of trauma, as this protective measure is necessary to prevent a mechanical obstruction.