Dry drowning

Dry drowning occurs when a person's lungs become unable to extract oxygen from the air, due primarily to:

The person may effectively drown without any sort of liquid. In cases of dry drowning in which the victim was immersed, very little fluid is aspirated into the lungs. The laryngospasm reflex essentially causes asphyxiation and neurogenic pulmonary edema (œdema).

Dry drowning can occur clinically, or due to illness or accident. It is also one of the effects of waterboarding.

In normal breathing, the diaphragm contracts, causing the lungs to expand (lungs are above the diaphragm). This expansion draws air into the lungs by generating a negative pressure or vacuum. Air first travels through the rigid larynx and upper airways before filling the inflatable alveoli in the lungs.

When water or other foreign bodies are inhaled, laryngospasm occurs and the person's larynx spasms shut. As a result, the vacuum created by the diaphragm cannot be filled by the inrush of air into the lungs, and the vacuum persists. In an attempt to force air in through the spasmed larynx, the person may breathe deeper and with more effort, but this only increases the vacuum's force inside the chest. The obstruction to the inflow of oxygen causes hypoxia, and the obstruction to the outflow of carbon dioxide causes acidosis, both resulting in death.

In addition, a multifactorial form of pulmonary edema is produced. The heart continues to beat normally during this time, and blood continues to circulate, though pulmonary oxygen and carbon dioxide gas exchange is markedly reduced. The volume of blood in the pulmonary circulation increases, by pulling in more blood from the abdomen, head, arms and legs; abnormally large volumes of this blood enter the pulmonary circulation via the superior and inferior vena cavae (great veins) in response to the persistent partial vacuum. From the vena cavae, the increased blood volume flows through the right atrium and into the right ventricle. The blood volume is great enough to stretch out the ventricle, similar to water entering a balloon.

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