Drowning

Drowning is a type of suffocation induced by the submersion of the mouth and nose in a liquid. Submersion injury refers to both drowning and near-miss incidents. Most instances of fatal drowning occur alone or in situations where others present are either unaware of the victim's situation or unable to offer assistance. After successful resuscitation, drowning victims may experience breathing problems, confusion, or unconsciousness. Occasionally, victims may not begin experiencing these symptoms until several hours after they are rescued. An incident of drowning can also cause further complications for victims due to low body temperature, aspiration, or acute respiratory distress syndrome (respiratory failure from lung inflammation). Drowning is more likely to happen when spending extended periods near large bodies of water. Risk factors for drowning include alcohol use, drug use, epilepsy, minimal swim training or a complete lack of training, and, in the case of children, a lack of supervision. Common drowning locations include natural and man-made bodies of water, bathtubs, and swimming pools. Drowning occurs when a person spends too much time with their nose and mouth submerged in a liquid to the point of being unable to breathe. If this is not followed by an exit to the surface, low oxygen levels and excess carbon dioxide in the blood trigger a neurological state of breathing emergency, which results in increased physical distress and occasional contractions of the vocal folds. When significant amounts of water enter the lungs, it is most often later in the process, when they irresistibly force an inhalation. While the word "drowning" is commonly associated with fatal results, drowning may be classified into three different types: drowning that results in death, drowning that results in long-lasting health problems, and drowning that results in no health complications. Sometimes the term "near-drowning" is used in the latter cases. Among children who survive, health problems occur in about 7.5% of cases. Steps to prevent drowning include teaching children and adults to swim and to recognise unsafe water conditions, never swimming alone, use of personal flotation devices on boats and when swimming in unfavourable conditions, limiting or removing access to water (such as with fencing of swimming pools), and exercising appropriate supervision. Treatment of victims who are not breathing should begin with opening the airway and providing five breaths of mouth-to-mouth resuscitation. Cardiopulmonary resuscitation (CPR) is recommended for a person whose heart has stopped beating and has been underwater for less than an hour.

Risk factors

Many behavioral and physical factors are related to drowning: Drowning is the most common cause of death for people with seizure disorders, largely in bathtubs. Epileptics are more likely to die due to accidents such as drowning. However, this risk is especially elevated in low and middle-income countries compared to high-income countries. The use of alcohol increases the risk of drowning across developed and developing nations. Alcohol is involved in approximately 50% of fatal drownings, and 35% of non-fatal drownings. Inability to swim can lead to drowning. Participation in formal swimming lessons can reduce this risk. The optimal age to start the lessons is childhood, between one and four years of age. Feeling overly tired reduces swimming performance. This exhaustion can be aggravated by anxious movements motivated by fear during or in anticipation of drowning. An overconfident appraisal of one's own physical capabilities can lead to "swimming out too far" and exhaustion before returning to solid footing. Free access to water can be hazardous, especially to young children. Barriers can prevent young children from gaining access to the water. Ineffective supervision, since drowning can occur anywhere there is water, even in the presence of lifeguards. Risk can vary with location depending on age. Children between one and four more commonly drown in home swimming pools than elsewhere. Drownings in natural water settings increase with age. More than half of drownings occurring among those fifteen years and older occurred in natural water environments. Familial or genetic history of sudden cardiac arrest (SCA) or sudden cardiac death (SCD) can predispose children to drown. Extensive genetic testing and/or consultation with a cardiologist should be done when there is a high suspicion of familial history and/or clinical evidence of sudden cardiac arrest or sudden cardiac death. Individuals with undetected primary cardiac arrhythmias, as cold water immersion or aquatic exercise can induce these arrhythmias to occur. Population groups at risk in the US are the old and the young. Youth: drowning rates are highest for children under five years of age and people fifteen to twenty-four years of age. Minorities: the fatal unintentional drowning rate for African Americans above the age of 29 between 1999 and 2010 was statistically significantly higher than that of white people above the age of 29. The fatal drowning rate of African American children of ages from five to fourteen is almost three times that of white children in the same age range and 5.5 times higher in swimming pools. These disparities might be associated with a lack of basic swimming education in some minority populations.

Oxygen deprivation

A conscious person will hold their breath 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 their breath for some time, but the breathing reflex will increase until the person 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 an 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 person can no longer voluntarily hold their breath. This typically occurs at an arterial partial pressure of carbon dioxide of 55 mm Hg but may differ significantly between people. When the body is submerged into cold water, breath-holding time is significantly shorter than that in air due to the cold shock response. The breath-hold breakpoint 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. Following this, a blackout may occur before the diver feels an urgent need to breathe. This can occur at any depth and is common in distance breath-hold divers in swimming pools. Both deep and distance free divers often use hyperventilation 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. A continued lack of oxygen in the brain, hypoxia, will quickly render a person unconscious, usually around a blood partial pressure of oxygen of 25–30 mmHg. In some instances, laryngospasm closes the airways, and the drowning victim is found to have gone into cardiac arrest as a result of asphyxiation without inhaling water; an unconscious person rescued with a sealed airway stands a good chance of a full recovery. Artificial respiration is also much more effective without water in the lungs. At this point, the person stands a good chance of recovery if attended to within minutes. More than 10% of drownings may involve laryngospasm, but the evidence suggests that it is not usually effective at preventing water from entering the trachea. The lack of water found in the lungs during autopsy does not necessarily mean there was no water at the time of drowning, as small amounts of freshwater are absorbed into the bloodstream. Hypercapnia and hypoxia both contribute to laryngeal relaxation, after which the airway is open through the trachea. There is also bronchospasm and mucous production in the bronchi associated with laryngospasm, and these may prevent water entry at terminal relaxation. The hypoxemia and acidosis caused by asphyxia in drowning affect various organs. There can be central nervous system damage, cardiac arrhythmia, pulmonary injury, reperfusion injury, and multiple-organ secondary injury with prolonged tissue hypoxia. 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 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 after six minutes from which recovery is generally considered impossible. Hypothermia of the central nervous system may prolong this. In cold temperatures below , the brain may be cooled sufficiently to allow for a survival time of more than an hour. The extent of central nervous system injury, to a large extent, determines the survival and long-term consequences of drowning. In the case of children, most survivors are found within 2 minutes of immersion, and most fatalities are found after 10 minutes or more.

Diagnosis

The World Health Organization in 2005 defined drowning as "the process of experiencing respiratory impairment from submersion/immersion in liquid." This definition does not imply death or even the necessity for medical treatment after removing the cause, nor that any fluid enters the lungs. The WHO classifies this as death, morbidity, and no morbidity. There was also consensus that the terms wet, dry, active, passive, silent, and secondary drowning should no longer be used. Experts differentiate between distress and drowning. Distress – people in trouble, but who can still float, signal for help, and take action. Drowning – people suffocating and in imminent danger of death within seconds.

Forensics

Forensic diagnosis of drowning is considered one of the most difficult in forensic medicine. External examination and autopsy findings are often nonspecific, and the available laboratory tests are often inconclusive or controversial. The purpose of an investigation is to distinguish whether the death was due to immersion or whether the body was immersed postmortem. The mechanism in acute drowning is hypoxemia and irreversible cerebral anoxia due to submersion in liquid. Drowning would be considered a possible cause of death if the body was recovered from a body of water, near a fluid that could plausibly have caused drowning, or found with the head immersed in a fluid. A medical diagnosis of death by drowning is generally made after other possible causes of death have been excluded by a complete autopsy and toxicology tests. Indications of drowning are unambiguous and may include bloody froth in the airway, water in the stomach, cerebral edema and petrous or mastoid hemorrhage. Some evidence of immersion may be unrelated to the cause of death, and lacerations and abrasions may have occurred before or after immersion or death. Diatoms should normally never be present in human tissue unless water was aspirated. Their presence in tissues such as bone marrow suggests drowning; however, they are present in soil and the atmosphere, and samples may be contaminated. An absence of diatoms does not rule out drowning, as they are not always present in water. A match of diatom shells to those found in the water may provide supporting evidence of the place of death. Drowning in saltwater can leave different concentrations of sodium and chloride ions in the left and right chambers of the heart, but they will dissipate if the person survived for some time after the aspiration, or if CPR was attempted, and have been described in other causes of death. Most autopsy findings relate to asphyxia and are not specific to drowning. The signs of drowning are degraded by decomposition. Large amounts of froth will be present around the mouth and nostrils and in the upper and lower airways in freshly drowned bodies. The volume of froth is much greater in drowning than from other origins. Lung density may be higher than normal, but normal weights are possible after cardiac arrest or vasovagal reflex. The lungs may be overinflated and waterlogged, filling the thoracic cavity. The surface may have a marbled appearance, with darker areas associated with collapsed alveoli interspersed with paler aerated areas. Fluid trapped in the lower airways may block the passive collapse that is normal after death. Hemorrhagic bullae of emphysema may be found. These are related to the rupture of alveolar walls. These signs, while suggestive of drowning, are not conclusive.

Prevention

, and describes treading water. |390x390px It is estimated that more than 85% of drownings could be prevented by supervision, training in water skills, technology, and public education. Measures that help to prevent drowning include the following: Learning to swim: Being able to swim is one of the most recommended methods against drowning. It is recommended that children learn to swim in a safe and supervised environment when they are between 1 and 4 years old, but learning to swim is recommended at any age. Surveillance: The surveillance of swimmers, especially children, is essential, because drownings may be silent and go unnoticed. A drowning person may be unable to wave, shout or even speak, and remain below the surface or unconscious. The highest rates of drowning globally are among children under five years-old. People who already know how to swim could need certain surveillance too. Many pools and bathing areas have lifeguards or a drowning detection system, and local legislation may require surveillance methods. Non-professional bystanders are important in detecting and notifying drownings. Lifeguards can be called by mobile phone in many cases. Evidence shows that alarms in pools are unreliable. The World Health Organization recommends that the most crowded hours be addressed by increasing the number of lifeguards at those times. |alt= Education and awareness: The WHO recommends wide training of the public in first aid, including cardiopulmonary resuscitation (CPR), and to behave safely in the water. Swimmers need to understand how to swim within their own abilities with regard to currents, depth, temperature or waves, and to be informed of the state of the sea. Even good swimmers may drown due to hazardous water conditions and other circumstances, so it is recommended that everyone learns how to select safe places to swim that have surveillance, to understand the local conditions, and to follow the rules. Many people who drown fail to follow the local safety guidelines or pay attention to signs indicating swimming restrictions and lifeguard duties. Shallow water and obstructions: Local conditions may include shallow water and obstructions. It is not prudent to jump into the water without knowing the depth, especially if entering head-first. Between 1.2% and 22% of all spinal injuries are from accidents diving into shallow water or hitting hidden obstructions such as submerged trees. Up to 21% of shallow-water diving accidents cause spinal injury, risking permanent paralysis, or death. Alcohol and drugs: Alcohol and drugs increase the risk of drowning, and this risk increases for bars near water and parties on boats. For example, Finland sees several alcohol-implicated drownings every year at the Midsummer weekend as Finns celebrate in and around lakes and beaches. Anxiety and panic in water: The anxious movements produced by fear during drowning can render swimmers exhausted. Additionally, underestimating one's own stamina can cause a situation in which the swimmer finds themselves too exhausted to exit the water. Reducing the rhythm of swimming can mitigate the chances of suffering a cramp or contracture (muscle spasm), it is recommended to keep calm, move towards the shore (or pool's border), and ask for help if necessary. The stings of forms of marine life can also produce panic, but after receiving a sting of most types, it is possible to get out of the water without serious problems, even if some pain appears. For most swimming problems, it can be useful to assume a horizontal position in the water, facing up, because it can reduce the effort required to float. Awareness of medical conditions: Some medical conditions, such as epilepsy, syncope, cramps or seizures, demand caution when in water, or near water. They may require controlled conditions for swimming (and even washing) and a good understanding of the individual's limitations. State of the water: It is recommended to be aware of turbulences, dangerous waves, undertow, wind and weather conditions, dangerous animals, and water temperature. Currents of water (as river currents and sea rip currents) can carry the swimmers away with great force, so authorities in safety often recommend to the users of swimming areas avoiding useless efforts in the opposite direction, but, instead, taking some advantage of the current direction while swimming or floating outwards. Safety equipment: All boats and pools must be equipped with adequate safety equipment, such as lifejackets or lifebuoys; often this is a regulatory requirement. Any recreational activity on a boat or near water requires that a lifejacket be worn, especially by children who cannot swim and others at risk of drowning. Lifejackets must be well-fitting and properly fastened, and their wearers must understand that they have to jump into water with one of them, and use it by fastening the strap properly and grabbing the front neck area with both hands. Emergency flotation equipment, such as a circular lifebuoy, can be thrown to the swimmer if available, but, if not, any other flotation device, including inner tubes, water wings or foam tubes, can be used. Navigation safety: Navigation accidents are a cause of drowning that can be prevented staying informed about the state of the sea, having the proper safety instruments (especially lifejackets on board, as mentioned before) and with any other advisable measure that can be applied. Rescue robots and drones: Remote-controlled devices may assist a water rescue. Floating rescue robots can navigate to the victim to hold on to and even help to recover them. Aerial drones are fast, can help locate victims, and even drop life jackets. Swimming in pairs ("buddy system"): Pairing up swimmers, so they keep surveillance of each other, and are available to help in case of any problem (because of a purpose of safety, not for competitive reasons). Pool fencing: Every private and public swimming pool should be fully fenced, with child-proof latches on the gates. Many countries, including most Australian states since 1998 and France since 2003, require the fencing of pools. Objects (such as toys and others) can attract children to the water. Pool drains: Swimming pools may have filtration systems that circulate the water. Filtration drains without covers, or too strong, can injure swimmers by trapping hair or other parts of the body, leading to immobilization and drowning. Many small drainage holes are usually preferred to a single large one. Periodic inspections can check that the system is safe. Paying heed to warning signs, flags and advices: Because they indicate the safety of swimming and warn about any danger.

Management

Medical care

People with a near-drowning experience who have normal oxygen levels and no respiratory symptoms should be observed in a hospital environment for a period of time to ensure there are no delayed complications. The target of ventilation is to achieve 92% to 96% arterial saturation and adequate chest rise. Positive end-expiratory pressure will improve oxygenation. Drug administration via peripheral veins is preferred over endotracheal administration. Hypotension remaining after oxygenation may be treated by rapid crystalloid infusion. Cardiac arrest in drowning usually presents as asystole or pulseless electrical activity. Ventricular fibrillation is more likely to be associated with complications of pre-existing coronary artery disease, severe hypothermia, or the use of epinephrine or norepinephrine. While surfactant may be used, no high-quality evidence exist that looks at this practice. Extracorporeal membrane oxygenation may be used in those who cannot be oxygenated otherwise. Steroids are not recommended.

Prognosis

People who have drowned who arrive at a hospital with spontaneous circulation and breathing usually recover with good outcomes. Early provision of basic and advanced life support improve the probability of a positive outcome. A longer duration of submersion is associated with a lower probability of survival and a higher probability of permanent neurological damage. Contaminants in the water can cause bronchospasm and impaired gas exchange and can cause secondary infection with delayed severe respiratory compromise. Low water temperature can cause ventricular fibrillation, but hypothermia during immersion can also slow the metabolism, allowing longer hypoxia before severe damage occurs. Hypothermia that reduces brain temperature significantly can improve the outcome. A reduction of brain temperature by 10 °C decreases ATP consumption by approximately 50%, which can double the time the brain can survive. The younger the person, the better the chances of survival. In one case, a child submerged in cold ( ) water for 66 minutes was resuscitated without apparent neurological damage. However, over the long term significant deficits were noted, including a range of cognitive difficulties, particularly general memory impairment, although recent magnetic resonance imaging (MRI) and magnetoencephalography (MEG) were within normal range.

Children

Drowning is a major worldwide cause of death and injury in children. An estimate of about 20% of non-fatal drowning victims may result in varying degrees of ischemic and/or hypoxic brain injury. Hypoxic injuries refers to a lack or absence of oxygen in certain organs or tissues. Ischemic injuries on the other hand refers inadequate blood supply to certain organs or part of the body. These injuries can lead to an increased risk of long-term morbidity. Prolonged hypothermia and hypoxemia from nonfatal submersion drowning can result in cardiac dysrhythmias such as ventricular fibrillation, sinus bradycardia, or atrial fibrillation. Long-term neurological outcomes of drowning cannot be predicted accurately during the early stages of treatment. Although survival after long submersion times, mostly by young children, has been reported, many survivors will remain severely and permanently neurologically compromised after much shorter submersion times. 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.

Epidemiology

The World Health Organization estimates that drowning causes around 300,000 deaths worldwide each year, with 92% of drowning deaths occurring in low- and middle-income countries. It is the fourth leading cause of death among children aged 1-4 years and the third leading cause of death among children aged 5-14 years. In many countries, drowning is one of the main causes of preventable death for children under 12 years old. In the United States in 2006, 1100 people under 20 years of age died from drowning. The United Kingdom has 450 drownings per year, or 1 per 150,000, whereas in the United States, there are about 6,500 drownings yearly, around 1 per 50,000. In Asia suffocation and drowning were the leading causes of preventable death for children under five years of age; a 2008 report by UNICEF found that in Bangladesh, for instance, 46 children drown each day. Due to a generally increased likelihood for risk-taking, males are four times more likely to have submersion injuries. In the fishing industry, the largest group of drownings is associated with vessel disasters in bad weather, followed by man-overboard incidents and boarding accidents at night, either in foreign ports or under the influence of alcohol. Scuba diving deaths are estimated at 700 to 800 per year, associated with inadequate training and experience, exhaustion, panic, carelessness, and barotrauma.

United States

In the United States, drowning is the second leading cause of death (after motor vehicle accidents) in children aged 12 and younger. People who drown are more likely to be male, young, or adolescent. There is a racial disparity found in drowning incidents. According to CDC data collected from 1999 to 2019, drowning rates among Native Americans was 2 times higher than among non-Hispanic whites while the rate among African-Americans was 1.5 times higher. Surveys indicate that 10% of children under 5 have experienced a situation with a high risk of drowning. Worldwide, about 175,000 children die through drowning every year. The causes of drowning cases in the US from 1999 to 2006 were as follows: According to the US National Safety Council, 353 people ages 5 to 24 drowned in 2017.

Society and culture

Old terminology

The word "drowning"—like "electrocution"—was previously used to describe fatal events only. Occasionally, that usage is still insisted upon, though the medical community's consensus supports the definition used in this article. Several terms related to drowning which have been used in the past are also no longer recommended. These include: Active drowning: people, such as non-swimmers and the exhausted or hypothermic at the surface, who are unable to hold their 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. Dry drowning: drowning in which no water enters the lungs. Near drowning: drowning which is not fatal. Wet drowning: drowning in which water enters the lungs. Passive drowning: people who suddenly sink or have sunk due to a change in their circumstances. Examples include people who drown in an accident due to sudden loss of consciousness or sudden medical condition. Secondary drowning: physiological response to foreign matter in the lungs due to drowning causing extrusion of liquid into the lungs (pulmonary edema) which adversely affects breathing. Silent drowning: drowning without a noticeable external display of distress.

Capital punishment

, anonymous period painting, Musée d'histoire de Nantes In Europe, drowning was used as capital punishment. During the Middle Ages, a sentence of death was read using the words , or "with pit and gallows". 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 it was carried out by Jean-Baptiste Carrier at Nantes.

Experience

People who have experienced drowning have reported slowing of time, but this is suggested to be a function of recollection, not perception. If the person is conscious after the initial struggle and breath-holding, they may feel a burning or tearing sensation on aspirating water. This burning sensation does not depend on the type of water. Following this painful feeling, many report peaceful perceptions, hallucinations, diminished pain and even euphoria. Sensations of tranquility are not limited to drowning, and similar perceptions have also been reported in near-death experiences from other causes. The euphoria and calmness can be attributed to cerebral hypoxia and consequent changes in neurotransmitters. These experiences vary by person, because the rate of oxygen loss in the blood (and resulting hypoxia) depends on the circumstances.

References

Text derived from https://en.wikipedia.org/w/index.php?oldid=1378240449 under CC BY-SA 4.0; modifications have been made.

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