There is no bodily sensation that warns a diver of an impending blackout, and people (often capable swimmers swimming under the surface in shallow water) become unconscious and drown quietly without alerting anyone to the fact that there is a problem; they are typically found at the bottom. Pathophysiology
Drowning can be considered as going through four stages:
Breath-hold under voluntary control until the urge to breathe due to hypercapnia becomes overwhelming
Fluid is swallowed and/or aspirated into the airways
Cerebral anoxia stops breathing and aspiration
Cerebral injury due to anoxia becomes irreversibleGenerally, in the early stages of drowning, a person holds their breath to prevent water from entering their lungs. When this is no longer possible, a small amount of water entering the trachea causes a muscular spasm that seals the airway and prevents further passage of water. If the process is not interrupted, loss of consciousness due to hypoxia is followed rapidly by cardiac arrest. Oxygen deprivation
A conscious person will hold their breath (see Apnea) and will try to access air, often resulting in panic, including rapid body movement. This uses up more oxygen in the bloodstream and reduces the time until unconsciousness. The person can voluntarily hold his or her breath for some time, but the breathing reflex will increase until the person tries to breathe, even when submerged.The breathing reflex in the human body is weakly related to the amount of oxygen in the blood but strongly related to the amount of carbon dioxide (see Hypercapnia).
Factors affecting the probability of long-term recovery with mild deficits or full function in young children include the duration of submersion, whether advanced life support was needed at the accident site, the duration of cardiopulmonary resuscitation, and whether spontaneous breathing and circulation are present on arrival at the emergency room. Prolonged submersion in water for more than 5–10 minutes usually leads to poorer prognosis.Data on the long-term outcome are scarce and unreliable. Neurological examination at the time of discharge from the hospital does not accurately predict long-term outcomes. Some people with severe brain injury who were transferred to other institutions died months or years after the drowning and are recorded as survivors. Nonfatal drownings have been estimated as two to four times more frequent than fatal drownings. Long-Term Effects of Drowning in Children
Long-term effects of nonfatal drowning mainly include damage to major organs such as the brain, lungs, and kidneys. Prolonged submersion time is highly attributed to hypoxic ischemic brain injury in susceptible areas of the brain such as the hippocampus, insular cortex, and/or basal ganglia. Severity in hypoxic ischemic damage of these brain structures corresponds to the severity in global damage to areas of the cerebral cortex. The cerebral cortex is a brain structure that is responsible for language, memory, learning, emotion, intelligence, and personality. Global damage to the cerebral cortex can affect one or more of its primary function, Treatment of pulmonary complication from drowning is highly dependent on the amount of lung injury that occurred during the incident.