In most people, the laryngospasm relaxes sometime after unconsciousness, and water can then enter the lungs, causing a "wet drowning." However, about 7–10% of people maintain this seal until cardiac arrest. This has been called "dry drowning", as no water enters the lungs. In forensic pathology, water in the lungs indicates that the person was still alive at the point of submersion. An absence of water in the lungs may be either a dry drowning or indicates a death before submersion.Aspirated water that reaches the alveoli destroys the pulmonary surfactant, which causes pulmonary edema and decreased lung compliance, compromising oxygenation in affected parts of the lungs. This is associated with metabolic acidosis, secondary fluid, and electrolyte shifts. During alveolar fluid exchange, diatoms present in the water may pass through the alveolar wall into the capillaries to be carried to internal organs. The presence of these diatoms may be diagnostic of drowning. Of people who have survived drowning, almost one-third will experience complications such as acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). ALI/ARDS can be triggered by pneumonia, sepsis, and water aspiration. These conditions are life-threatening disorders that can result in death if not treated promptly. During drowning, aspirated water enters the lung tissues, causes a reduction in alveolar surfactant, obstructs ventilation, and triggers a release of inflammatory mediators which ultimately results in hypoxia. Specifically, upon reaching the alveoli, hypotonic liquid found in freshwater dilutes pulmonary surfactant, destroying the substance.
These lung injuries can be contributed by water aspiration and also irritants present in the water such as microbial pathogens leading to complications such as lung infection that can develop in adult respiratory disease syndrome later on in life. Some literature suggests that occurrences of drowning can lead to acute kidney injury from lack of blood flow and oxygenation due to shock and global hypoxia. These kidney injury can cause irreversible damage to the kidneys and may require long-term treatment such as renal replacement therapy. Infant Risk
Children are overrepresented in drowning statistics, with children aged 0–4 years old having the highest number of deaths due to unintentional downing. In 2019 alone 32,070 children between the ages 1–4 years old died as a result of unintentional drowning, equating to an age-adjusted fatality of 6.04 per 100,000 children. Infants are particularly vulnerable because while their mobility develops quickly, their perception concerning their ability for locomotion between surfaces develops slower. An infant can have full control of their movements, but simply wont recognize that water does not provide the same support for crawling as hardwood floors would. An infant’s capacity for movement needs to be met with an appropriate perception of surfaces of support (and avoidance of surfaces that do not support locomotion) to avoid drowning. By crawling and interacting with their environment, infants learn to distinguish surfaces offering support for locomotion from those that do not, and their perception of surface characteristics will improve, as well as their perception of falls risk, over several weeks.