The Drowning reference article from the English Wikipedia on 24-Jul-2004
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Drowning

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Drowning is death due to asphyxia caused by immersion in fluid, usually water. Near drowning is initial survival of a drowning accident which can lead to serious secondary complications including death; cases of near drowning therefore require attention by medical professionals. Secondary drowning is death due to chemical and biological changes in the lungs after a near drowning incident or exposure to chemicals.

In many countries, drowning is one of the leading causes of death for children up to 14 years.

Table of contents
1 Occurrences
2 The drowning process
3 Rescue and Treatment
4 Prevention
5 See also
6 External links

Occurrences

About 6500 drowning deaths occur in the United States every year, and about 140,000 worldwide (estimate). Near drowning incidents are estimated to be 2 to 500 times the number of drowning incidents. Most of the victims are either young children, especially boys, or young adolescent males. Drowning is the second most likely cause of injury and death for children up to 14 years after car accidents. Surveys indicate that 10% of the children under 5 experienced a situation with a high risk of drowning. Males in general are much more likely to drown than females. Also, 90% of the drownings occur in freshwater. Drowning related injuries is the fifth most likely cause of accidental death in the US. The drowning cases in the US can be sorted as follows:

The drowning process

Situations leading to drowning

Drowning is caused by immersion in fluid. This requires the victim to be immersed in fluid and to be unable or unwilling to rescue himself. Most drownings occur when the victim
passes out or is exhausted and unable to access air. This may be for example a swimmer with a heart attack in the ocean, exhaustion and coma due to hypothermia after breaking through the surface of a frozen lake, or merely a drunk person passing out in a small puddle. A few centimeters of water are sufficient for drowning if the victim lies face down on the water. Another cause of drownings are adverse water and weather conditions, including waves and currents like tides and rivers. Drowning may also be due to strong negative buoyancy, were a denser than water item forces the victim underwater. Finally drowning may be the cause due to another person forcing the victim under water, i.e. murder. (For a list of causes see swimming)

Initial Reactions to Submersion

Submerging the face into water causes the mammalian diving reflex, which is found in all mammals, but especially in marine mammals as for example whales and seals. This reflex puts the body into energy saving modus to maximize the time a person can stay under water. The effect of this reflex is larger in cold water than in warm water, and includes three factors: Thus both a conscious and an unconscious person can survive longer without oxygen under water than in a comparable situation on dry land.

Initial Oxygen starvation

A conscious victim 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 blood stream and accelerates the time to unconsciousness.

The victim can voluntarily hold their breath for some time, but the breathing reflex will increase until the victim will try to breathe, even when submerged. The breathing reflex in the human body is related not to the amount of oxygen in the blood but the amount of carbon dioxide. During apnea, the oxygen in the blood is used by the cells, and converted into carbon dioxide. Thus, the level of oxygen in the blood decreases, and the level of carbon dioxide increases. Increasing carbon dioxide levels lead to a stronger and stronger breathing reflex, up to the breath-hold breakpoint, at which the victim can no longer hold their breath. This occurs at a partial pressure of carbon dioxide of 55mm Hg, but depends heavily on the individual and can be increased by training. Decreasing oxygen levels, however, lead to a sudden loss of consciousness without warning, usually around a partial pressure of 25 to 30mm Hg. This condition of inadequate oxygen is called hypoxia. Trained apnea divers can hold their breath and resist the breathing reflex until they pass out. The loss of consciousness due to hypoxia is called shallow water blackout when it occurs as the victim is ascending from a dive; the decreasing water pressure around the victim causes the partial pressure of oxygen in the blood to also decrease. The loss of consciousness due to hypoxia is more likely when rapid breathing before apnea decreased the level of carbon dioxide in the blood without increasing the level of oxygen, as the blood is usually saturated with oxygen. Therefore, black out may occur without warning before a breathing reflex is felt. (Note: Breath holding in water should not be preceded by rapid breathing to store oxygen, and should always be supervised by a second person.)

Water entering the upper airways

If water enters the airways of a conscious victim, the victim will try to cough up the water, or swallow it, therefore involuntarily inhale more water. Upon water entering the airways, conscious or unconscious victims show laryngospasm, i.e. the Larynx or the vocal cords in the throat constrict and seal the air tube. This prevents water from entering the lungs. Due to this laryngospasm, water enters the stomach in the initial phase of drowning and only very little water enters the lungs. Unfortunately, not much air enters the lungs, either. In most victims, the laryngospasm relaxes some time after unconsciousness, and water can enter the lungs, a so called wet drowning. However, about 10-15% of the victims maintain this seal until cardiac arrest, a so called dry drowning, as no water enters the lungs. (In forensics, water in the lungs indicate that the victim was still alive during drowning. The absence of water in the lungs may be either a dry drowning or a death before submersion.)

Unconsciousness due to Oxygen Starvation

Due to oxygen starvation, the victim will become unconscious. Interviews with near drowning victims indicate that the last thought before unconsciousness is to imagine other peoples reaction to one's drowning, and feeling embarrassed and ashamed for being stupid enough to drown, believing that most people think that smart people would have been able to prevent drowning.

An unconscious victim rescued while the airways are still sealed due to laryngospasm has a good chance of experiencing no ill after effects. Also, since little water has entered the lungs, no water has to be removed from the lungs before rescue breathing. In most victims, the laryngospasm relaxes some time after unconsciousness, and water fills the lungs, i.e. a wet drowning occurs. Freshwater contains less salt than the blood, and will therefore be absorbed by the blood stream due to osmosis. In animal experiments, this changed the blood chemistry and lead to cardiac arrest in 2-3 minutes. Salt water is much saltier than blood, and due to osmosis, water will leave the blood stream and enter the lungs. In animal experiments, the thicker blood requires more work from the heart, leading to cardiac arrest in 8 to 10 minutes. However, autopsies on drowning victims do not show indications of these effects, and there appears to be little difference in drowning in salt water or fresh water. Water, regardless of freshwater or saltwater, will damage the inside surface of the lung, collapse the alveoli and cause a hardening of the lungs with a reduced ability to exchange air. This may cause death even hours after rescuing a conscious victim and is called secondary drowning.

Cardiac Arrest and Death

Due to lack of oxygen or due to chemical changes in the lungs, the heart may stop beating. This cardiac arrest stops the flow of blood, including the transport of oxygen to the brain. The cardiac arrest is also known as clinical death. At that point, there is still a chance of rescue. However, the brain cannot survive long without oxygen, and the lack of oxygen in the blood combined with the cardiac arrest will lead to the deterioration of the brain cells, causing brain damage and eventually brain death. In medicine, this is considered the point of no return, and the victim is truly dead. On surface, the brain will die after approximately 6 minutes. However, if submersed in cold water the metabolism can slow down significantly, and one case is documented where a child survived drowning after being submerged in cold water for 70 minutes, and another case of an 18 year old man, surviving 38 minutes under water. Even after brain death some cells of the body will continue to live, and for example hair may grow. After death, rigor mortis will set in and stay for about two days, depending on many factors as for example the water temperature.

Rescue and Treatment

If a swimmer is missing or after a victim was seen for the first time, bystanders should be called for help immediately if possible. In a pool, call the Lifeguard immediately. Emergency medical services and Paramedics should be contacted as soon as possible.

The first step in rescuing a drowning victim is to bring the victims mouth and nose above the water surface. For further treatment it is advisable to lift the victim out of the water, for example, onto dry land or a boat. Conscious victims may be in panic and may hinder rescue efforts. Often, they cling to the rescuer and try to push themselves above water, in the process pushing the rescuer under water. To avoid this it is recommended to approach the panicking victim with a buoyant object, or from behind, twisting his arm on the back to restrict his movement. If the victim pushes the rescuer under water, it is advisable to dive downwards to get away from the victim, whose main goal is to move upward. If the victim is physically much stronger than the rescuer there may be cases where it is advisable for the rescuer to wait until the victim passes out so that the victim does not accidentally drown the rescuer.

After successfully approaching the victim, negatively buoyant objects may be removed, for example a weight belt. The priority is then to transport the victim to the water's edge in preparation for removal from the water. The victim is turned on his back. In the case of panicking victims, the secure grip is used to tow the victim from behind, with both rescuer and victim laying on their back, and the rescuer swimming a breaststroke kick. A cooperative victim may be towed in a similar fashion by holding him at the armpits, and the victim may assist with a breaststroke kick. Unconscious victims may be pulled in a similar fashion by holding him at the chin and cheeks, ensuring that the mouth and nose is well above the water.

There is also the option of pushing a cooperative victim laying on his back with the rescuer swimming on his belly and pushing the feet of the victim, or both victim and rescuer laying on the belly, with the victim hanging from the shoulders of the rescuers. This has the advantage that the rescuer can use both arms and legs to swim breaststroke, but if the victim pushes his head above the water, the rescuer may get pushed down. This style is often used to retrieve tired swimmers. If the victim wears a flotation device that stabilizes his position with the face up, e.g. a life jacket or a buoyancy compensator, only one hand of the rescuer is needed to pull the victim, and the other hand can also provide forward movement or may help in rescue breathing while swimming, using for example a snorkel.

Special care has to be taken for victims with suspected spinal injuries, and a back board (spinal board) may be used for the rescue. In water, CPR is very difficult, and the goal should be to bring the victim to a stable ground fast and then start CPR.

If the approach to a stable ground includes the edge of a pool without steps or the edge of a boat, special techniques have to be used to move the victim over the obstacle. For pools, the rescuer stands outside, holds the victim by his hands, with the victims back to the edge. the rescuer then dips the victim into the water quickly to achieve an upward speed of the body, aiding with the lifting of the body over the edge. Lifting a victim over the side of a boat may require more than one person. Special techniques are also used for helicopter rescue, although a rescue helicopter is usually accompanied by professionals from the Coast Guard, and no knowledge is necessary to the layman.

After reaching dry ground, all victim should seek medical assistance, especially if unconscious or if water - even small amounts - have entered the lungs. An unconscious victim may need artificial respiration or CPR. The Heimlich maneuver is needed only for obstructed airways, not for water in the airways. 100% Oxygen is highly recommended, including an intubation if necessary. Treatment for hypothermia may be necessary. Water in the stomach need not be removed. Other injuries should also be treated (see first aid). Victims that are alert, awake, and intact have an almost 100% survival rate.

Drowning victims should be treated even if they have been submerged for a long time. The rule "no patient should be pronounced dead until warm and dead" applies. Children have a good chance of survival in water up to 3 minutes, or 10 minutes in cold water (10-15C). There is one documented case where a child survived drowning after being submerged in cold water for 70 minutes, and another case of an 18 year old man, surviving 38 minutes under water, although this is very rare.

Prevention

Learn to swim and arrange for your dependents to learn to swim!

See also

External links