injuries and poisoning
Drowning
Oxygen deprivation due to drowning
When people are submerged under water, one of two things can happen: Water enters the lungs. The vocal cords may go into severe spasm, temporarily preventing water from reaching the lungs but also preventing breathing. In either case, the lungs cannot transfer oxygen to the blood. The decrease in the level of oxygen in the blood that results may lead to brain damage and death. Water in the lungs,in very large amounts, causes drowning immediately. Smaller amounts, particularly water that is contaminated by bacteria, algae, sand, dirt, chemicals, or vomit, can cause lung injury that is not apparent until hours after the person has been removed from the water. This problem is sometimes called secondary drowning. Lung injury tends to cause continuing oxygen deprivation. Freshwater in the lungs is absorbed into the bloodstream. Vocal cord spasmmay develop only after a person is removed from the water. If so, it usually occurs within a few minutes. Because water does not enter the lungs, this condition is sometimes called dry drowning. 