due to suffocation caused by water entering the lungs and preventing the absorption of oxygen leading to cerebral hypoxia
Near drowning is the survival of a drowning event involving unconsciousness or water inhalation and can lead to serious secondary complications, including death, after the event.
According to the World Health Organization
, drowning is the 3rd leading cause of unintentional injury death worldwide, accounting for 7% of all injury related deaths (est. 388,000 deaths by drowning in 2004, excluding those due to natural disaster
s), with 96% of these deaths occurring in low- and middle-income countries. In many countries, drowning is one of the leading causes of death for children under 12 years old. For example, in the United States, it is the second leading cause of death (after motor vehicle crashes) in children 12 and younger. The rate of drowning in populations around the world varies widely according to their access to water, the climate and the national swimming culture.
Drowning itself is quick and silent, although it may be preceded by distress which is more visible. A person drowning is unable to shout or call for help, or seek attention, as they cannot obtain enough air. The instinctive drowning response
is the final set of autonomic reactions
in the 20 – 60 seconds before sinking underwater, and to the untrained eye can look similar to calm safe behavior. Lifeguard
s and other persons trained in rescue learn to recognize drowning people by watching for these instinct
Drowning occurs more frequently in males and the young. Surveys indicate that 10% of children under 5 have experienced a situation with a high risk of drowning.
ClassificationExperts differentiate between distress and drowning. They also divide drowning into passive and secondary:
- Distress - these are people in trouble and distress, but who still have the ability to keep afloat, signal for help and take actions.
- Drowning - these are people suffocating and in imminent danger of death within seconds, and fall into two categories:
- Passive drowning - people who suddenly sink or have sunk due to a change in their circumstances. Examples include people who drown in an accident, or due to sudden loss of consciousness or sudden medical condition.
Active drowning - people such as non-swimmers and the exhausted or hypothermicHypothermiaHypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...
at the surface, who are unable to hold their mouthMouthThe mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
above water and are suffocating due to lack of air. Instinctively, people in such cases perform well known behaviors in the last 20 - 60 seconds before being submerged, representing the body's last efforts to obtain air.
Notably such people are unable to call for help, talk, reach for rescue equipment, or alert swimmers even feet away, and they may drown quickly and silently close to other swimmers or safety.
Behavior, signs and symptomsDrowning is most often quick and unspectacular. Its media depictions as a loud, violent struggle have much more in common with distressed non-swimmers
, who may well drown but have not yet begun. In particular, an asphyxiating person is seldom able to call for help. The instinctive drowning response
covers many signs or behaviors associated with drowning or near-drowning:
- Head low in the water, mouth at water level
- Head tilted back with mouth open
- Eyes glassy and empty, unable to focus
- Eyes open, with fear evident on the face
- Hyperventilating or gasping
- Trying to swim in a particular direction but not making headway
- Trying to roll over on the back to float
- Uncontrollable movement of arms and legs, rarely out of the water.
Pia notes that drowning begins at the point a person is unable to keep their mouth above water; inhalation of water takes place at a later stage. Most victims demonstrating the instinctive drowning response do not show prior evidence of distress.
), 10% in seawater
). Drownings in other fluids are rare, and are often related to industrial accidents.
People have drowned in as little as 30 mm of water lying face down, in one case in a wheel rut. Children have drowned in baths, buckets and toilets; inebriates or those under the influence of drugs have died in puddles.
Drowning can take place in other circumstances than those in popular awareness, for instance:
- Deep water blackoutDeep water blackoutA deep water blackout is a loss of consciousness caused by cerebral hypoxia on ascending from a deep freedive or breath-hold dive, typically of ten metres or more when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have...
- caused by latent hypoxiaHypoxia (medical)Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
upon ascent from depth, where the partial pressurePartial pressureIn a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture....
of oxygen in the lungs under pressure at the bottom of a deep free-dive is adequate to support consciousness but drops below the blackout threshold as the water pressure decreases on the ascent. It usually strikes upon arriving near the surface as the pressure approaches normal atmospheric pressure.
- Shallow water blackoutShallow water blackoutA shallow water blackout is a loss of consciousness caused by cerebral hypoxia towards the end of a breath-hold dive in water typically shallower than five metres , when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have...
- caused by hyperventilationHyperventilationHyperventilation or overbreathing is the state of breathing faster or deeper than normal, causing excessive expulsion of circulating carbon dioxide. It can result from a psychological state such as a panic attack, from a physiological condition such as metabolic acidosis, can be brought about by...
prior to swimming or diving. The primary urge to breathe (more precisely: to exhale) is triggered by rising carbon dioxideCarbon dioxideCarbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
(CO2) levels in the bloodstream. The body detects CO2 levels very accurately and relies on this to control breathing. Hyperventilation artificially depletes this, but leaves the diver susceptible to sudden loss of consciousness without warning from hypoxiaHypoxia (medical)Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
. There is no bodily sensation that warns a diver of an impending blackout, and victims (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 on the bottom.
- Secondary drowning - Inhaled fluid can act as an irritantIrritationIrritation or exacerbation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant...
inside the lungs. Physiological responses to even small quantities include the extrusion of liquid into the lungs (pulmonary edemaPulmonary edemaPulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...
) over the following hours, but this reduces the ability to exchange air and can lead to a person "drowning in their own body fluid". Certain poisonous vapors or gases (as for example in chemical warfareChemical warfareChemical warfare involves using the toxic properties of chemical substances as weapons. This type of warfare is distinct from Nuclear warfare and Biological warfare, which together make up NBC, the military acronym for Nuclear, Biological, and Chemical...
), or vomit can have a similar effect. The reaction can take place up to 72 hours after a near drowning incident, and may lead to a serious condition or death.
Clinical backgroundA continued lack of oxygen in the brain, known as hypoxia
, will quickly render a victim unconscious usually around a blood partial pressure of oxygen of 25-30 mmHg.
An unconscious victim rescued with an airway still sealed from Laryngospasm
(involuntary sealing of the throat) stands a good chance of a full recovery. Artificial respiration
is also much more effective without water in the lungs. At this point the victim stands a good chance of recovery if attended to within minutes.
OverviewA continued lack of oxygen in the brain, hypoxia
, will quickly render a victim unconscious usually around a blood partial pressure of oxygen of 25-30mmHg. An unconscious victim rescued with an airway still sealed from laryngospasm stands a good chance of a full recovery. Artificial respiration
is also much more effective without water in the lungs. At this point the victim stands a good chance of recovery if attended to within minutes. Latent hypoxia is a special condition leading to unconsciousness where the partial pressure of oxygen in the lungs under pressure at the bottom of a deep free-dive is adequate to support consciousness but drops below the blackout threshold as the water pressure decreases on the ascent, usually close to the surface as the pressure approaches normal atmospheric pressure. A blackout on ascent like this is called a deep water blackout
The brain cannot survive long without oxygen and the continued lack of oxygen in the blood combined with the cardiac arrest will lead to the deterioration of brain cells causing first brain damage
and eventually brain death
from which recovery is generally considered impossible.
A lack of oxygen or chemical changes in the lungs may cause the heart to stop beating; this cardiac arrest
stops the flow of blood and thus stops the transport of oxygen to the brain. Cardiac arrest used to be the traditional point of death but at this point there is still a chance of recovery. The brain will die after approximately six minutes without oxygen but special conditions may prolong this (see 'cold water drowning' below).
As well as the direct effect of oxygen deprivation, there are also dangerous effects on blood chemistry if water is taken into the lungs. The mechanism for this is different for fresh and seawater.
- Freshwater taken into the lungs will be pulled into the pulmonary circulation by osmosisOsmosisOsmosis is the movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides...
. The dilution of blood leads to hemolysisHemolysisHemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...
(bursting of red blood cells). The resulting elevation of plasmaBlood plasmaBlood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
K+ (potassium) level and depression of Na+ (sodium) level alter the electrical activity of the heart often causing ventricular fibrillationVentricular fibrillationVentricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Ventricular fibrillation is a medical emergency and most commonly identified arrythmia in cardiac arrest...
. In animal experiments this effect was shown to be capable of causing cardiac arrest in 2 to 3 minutes. Acute renal failureAcute renal failureAcute kidney injury , previously called acute renal failure , is a rapid loss of kidney function. Its causes are numerous and include low blood volume from any cause, exposure to substances harmful to the kidney, and obstruction of the urinary tract...
can also result from hemoglobinHemoglobinHemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
from the burst blood cells accumulating in the kidneyKidneyThe kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
s, and cardiac arrestCardiac arrestCardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
can also result if cold freshwater taken into the bloodstream sufficiently cools the heartHeartThe heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
- Sea water is hypertonic to blood (more salty). It poses the opposite danger. Osmosis will instead pull water from the bloodstream into the lungs, thickening the blood. In animal experiments the thicker blood requires more work from the heart leading to cardiac arrest in 8 to 10 minutes.
Autopsies on human drowning victims show no indications of these effects and there appears to be little difference between drownings in salt water and fresh water. After death, rigor mortis
will set in and remains for about two days, depending on many factors including water temperature.
Body's reaction to submersionSubmerging the face in water colder than about 21 °C (69.8 °F) triggers the mammalian diving reflex
, found in mammal
s, and especially in marine mammal
s such as whale
s and seals
. This reflex protects the body by putting it into energy saving mode to maximize the time it can stay under water. The strength of this reflex is greater in colder water and has three principal effects:
- BradycardiaBradycardiaBradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
, a slowing of the heart rateHeart rateHeart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
by up to 50% in humans.
- Peripheral vasoconstrictionVasoconstrictionVasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
, the restriction of the blood flow to the extremities to increase the blood and oxygen supply to the vital organs, especially the brainBrainThe brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
- Blood Shift, the shifting of blood to the thoracic cavityThoracic cavityThe thoracic cavity is the chamber of the human body that is protected by the thoracic wall ....
, the region of the chest between the diaphragm and the neck, to avoid the collapse of the lungs under higher pressure during deeper dives.
The reflex action is automatic and allows both a conscious and an unconscious person to survive longer without oxygen under water than in a comparable situation on dry land. The exact mechanism for this effect has been debated and may be a result of brain cooling similar to the protective effects seen in patients treated with deep hypothermia
Oxygen deprivationA conscious victim will hold his or her 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 reduces the time to unconsciousness. The victim can voluntarily hold his or her 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 weakly related to the amount of oxygen
in the blood
but strongly related to the amount of carbon dioxide
). During apnea, the oxygen in the body is used by the cells
, and excreted as 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 voluntarily hold his or her breath. This typically occurs at an arterial partial pressure
of carbon dioxide of 55 mm Hg, but may differ significantly from individual to individual and can be increased through training.
The breath-hold break point can be suppressed or delayed either intentionally or unintentionally. Hyperventilation
before any dive, deep or shallow, flushes out carbon dioxide in the blood resulting in a dive commencing with an abnormally low carbon dioxide level; a potentially dangerous condition known as hypocapnia
. The level of carbon dioxide in the blood after hyperventilation may then be insufficient to trigger the breathing reflex later in the dive and a blackout may occur without warning and before the diver feels any urgent need to breathe. This can occur at any depth and is common in distance breath-hold divers in swimming pools
. Hyperventilation is often used by both deep and distance free-divers to flush out carbon dioxide from the lungs to suppress the breathing reflex for longer. It is important not to mistake this for an attempt to increase the body's oxygen store. The body at rest is fully oxygenated by normal breathing and cannot take on any more. Breath holding in water should always be supervised by a second person, as by hyperventilating, one increases the risk of shallow water blackout because insufficient carbon dioxide levels in the blood fail to trigger the breathing reflex.
Water inhalationIf water enters the airway
s of a conscious victim, the victim will try to cough up the water or swallow it, thus inhaling more water involuntarily. Upon water entering the airways, both conscious and unconscious victims experience laryngospasm
, that is the larynx
or the vocal cords
in the throat constrict and seal the air tube
. This prevents water from entering the lung
s. Because of this laryngospasm, water enters the stomach in the initial phase of drowning and very little water enters the lungs. Unfortunately, this can interfere with air entering the lungs, too. In most victims, the laryngospasm relaxes some time after unconsciousness and water can enter the lungs causing a "wet drowning". However, about 10-15% of victims maintain this seal until cardiac arrest
. This is called "dry drowning
", as no water enters the lungs. In forensic pathology
, water in the lungs indicates that the victim was still alive at the point of submersion. Absence of water in the lungs may be either a dry drowning or indicates a death before submersion.
ManagementRescue involves bringing the persons mouth and nose above the water surface. A drowning person may cling to the rescuer and try to pull himself out of the water, submerging the rescuer in the process. Thus it is advised that the rescuer approach with a buoyant
object, or from behind, twisting the person's arm on the back to restrict movement. If the rescuer does get pushed under water, they should dive downwards to escape the person.
After a successful approach, negatively buoyant objects such as a weight belt are removed. The priority is then to transport the person to the water's edge in preparation for removal from the water. The person is turned on their back with a secure grip used to tow from behind. If the person is cooperative they may be towed in a similar fashion held at the armpits. If the person is unconscious they may be pulled in a similar fashion held at the chin and cheeks, ensuring that the mouth and nose are well above the water.
Special care has to be taken for people with suspected spinal injuries, and a back board (spinal board) may be needed for the rescue. In water, CPR
is ineffective, and the goal should be to bring the person to a stable ground quickly and then to start CPR. Once on ground chest compressions are performed if the patient is pulseless, and if they are not breathing rescue breaths. 100% oxygen is neither recommended nor discouraged. Treatment for hypothermia
may also be necessary.
The Heimlich maneuver is not recommended; the technique may have relevance in situations where airways are obstructed by solids but not fluids. Performing the manoeuver on drowning people not only delays ventilation but may induce vomiting, which if aspirated will place the patient in a far worse situation. Moreover, the use of the Heimlich manoeuver in any choking situation involving solids or fluids has become controversial and is generally no longer taught. For more information on this debate refer to the article Henry Heimlich
Because of the mammalian diving reflex (see above), person submerged in cold water and apparently drowned may revive after a relatively long period. Rescuers retrieving an apparently dead person from water significantly below body temperature should not consider the rescued person dead until he or she is warm and dead.
SurveillanceMany pools and designated bathing areas either have lifeguards, a pool safety camera
system for local or remote monitoring, or computer aided drowning detection. However, bystanders play an important role in drowning detection and either intervention or the notification of authorities by phone or alarm.
EpidemiologyIn the United States in 2006, 1100 people under 20 years of age died from drowning. Typically the United Kingdom suffers 450 drownings per annum or 1 per 150,000 of population whereas the United States suffers 6,500 drownings or around 1 per 50,000 of population. In Asia, according to a study by The Alliance for Safe Children
, suffocation and drowning were the most easily preventable causes of death for children under five years of age; a 2008 report by the organization found that in Bangladesh
, for instance, 46 children drown each day.
People who drown are more likely to be male, young or adolescent. Surveys indicate that 10% of children under 5 have experienced a situation with a high risk of drowning. About 175,000 children die through drowning every year. The causes of drowning cases in the US from 1999 to 2006 are as follows:
31.0% Drowning and submersion while in natural water
27.9% Unspecified drowning and submersion
14.5% Drowning and submersion while in swimming pool
9.4% Drowning and submersion while in bathtub
7.2% Drowning and submersion following fall into natural water
6.3% Other specified drowning and submersion
2.9% Drowning and submersion following fall into swimming pool
0.9% Drowning and submersion following fall into bathtub
Society and cultureIn Europe, drowning was used as capital punishment. In fact, during the Middle Ages, a sentence of death was read using the words "cum fossa et furca," or "with drowning-pit and gallows." Furthermore, drowning was used as a way to determine if a woman was a witch. The idea was that witches would float and innocent women would drown. For more details, see trial by drowning. It is understood that drowning was used as the least brutal form of execution, and was therefore reserved primarily for women, although favoured men were executed in this way as well.
Drowning survived as a method of execution in Europe until the 17th and 18th centuries. England had abolished the practice by 1623, Scotland by 1685, Switzerland in 1652, Austria in 1776, Iceland in 1777, and Russia by the beginning of the 1800s. France revived the practice during the French Revolution
(1789–1799) and was carried out by Jean-Baptiste Carrier
- Drowning prevention information from Seattle Children's Hospital.
- Information on search and recovery of drowning victims
- Canadian Red Cross: Drowning Research: Drownings in Canada, 10 Years of Research Module 2 - Ice & Cold Water Immersion* Canadian Lifesaving Society Canadian National Drowning Report (1991-2000)
- Training video and example of drowning behaviors (Audio missing during 0:17 - 0:58 of the video)
- World Health Organization fact-sheet on drowning with statistics (latest as of December 2010)
- Proceedings and results of World Congress on Drowning, 2002
- Report into Lifeguard effectiveness, also covering drowning facts and risks - CDC, 2001