Fatal Drowning: The Process of Death

Forensic investigations are carried out in cases when an unnatural cause of death is suspected. An example of this is when a body is found in a body of water, indicating a case of drowning. Although a large majority of cases are accidental in nature, they are still heavily scrutinised by forensic investigators (McCall & Sternard, 2020).

Deaths from drowning are a significant global burden; approximately 236,000 people die by drowning every year. Children, especially those between the ages of 1 and 5, are considered the most vulnerable. Drownings in bodies of fresh water, such as lakes and pools, account for the majority of cases (World Health Organization, 2021). Drowning as a cause of death is ascertained on the basis of the exclusion of all other causes (McCall & Sternard, 2020). This is because drowning deaths can be difficult to determine when a forensic pathologist is performing an autopsy due to there being minimal macroscopic findings. Whenever a body is found in a body of water, it is not necessarily a case of drowning because there are possibilities of the body having been deposited post-mortem. Therefore, due to reasonable doubt, all other potential causes of death must be eliminated before drowning is deemed the only explanation for death (Armstrong & Erskine, 2018).

Figure 1: Infographic about drowning deaths (World Health Organization, 2021).

This article will describe the physiology of drowning, explaining the process of drowning and identifying tests that can be done to assist in forensic investigation. Different types of drowning cases will then be mentioned to highlight the complexity of ascertaining a person’s cause of death.

What is the Physiology of Drowning?

Forensic pathologists classify drowning deaths as a type of asphyxial death (Armstrong & Erskine, 2018). Asphyxiation is characterised by a state of hypoxia, or an absence of oxygen, in the body. A deficiency of oxygen in the blood can hinder the adequate perfusion of tissues, leading to cellular injury and death. Asphyxia can be a consequence of there being no oxygen in the environment, of a person being unable to perform the action of inspiration, and of a person not being able to utilise oxygen from the environment on a physiological level (such as in cases of carbon monoxide poisoning) (Azmak, 2006). Being submersed under water acts as an obstruction to the airways, preventing the intake of air through breathing. A person can resist taking a breath until a threshold has been reached where oxygen has been depleted and carbon dioxide (a waste product of respiration) has accumulated in the blood. At the point when a person becomes hypoxic, a response to gasp for air is autonomically triggered. Due to this uncontrolled urge to take a breath, there is an aspiration of water in drowning (Bierens et al., 2016).

Figure 2: The process of drowning (Rezhylo, 2023).

Death by drowning can manifest very quickly, often occurring within minutes of submersion in a body of water. Apart from being deprived of oxygen, a person who is drowning is also subject to other physiological processes that similarly cause cellular injury and the termination of function of multiple organs. Osmosis is the process by which water molecules travel from a region of high water content (low concentration of solutes) to an area with a low water content (high concentration of solutes) through a semi-permeable membrane. This process is integral in establishing a balance between the different fluid compartments that exist in the body (Lopez & Hall, 2023). Yet, the mechanism of osmosis is key in facilitating cellular damage when a person inhales water into their lungs or when water enters the stomach through the mouth. Compared to blood, which is abundant in electrolytes, blood cells and solutes, fresh water is hypotonic. In other words, the water that has entered the lungs or stomach has a lower osmotic pressure compared to blood and will favour moving into the blood to dilute it. In turn, the influx of freshwater into the blood can result in haemolysis (the swelling and bursting of red blood cells), the disruption of gas exchange in the alveoli, and the disruption of electrolyte levels. In contrast, the aspiration of salt water, a hypertonic fluid, can lead to the permeation of fluid from blood plasma into the alveoli. Fluid build-up in the alveoli results in oedema that can develop into acute lung injury (Jin & Li, 2017). Being underwater for more than 4 minutes is typically indicative that the person has entered a state of anoxia, a point where there is a complete absence of oxygen making its way to the tissues of the brain. This is often fatal as anoxia is followed by irreversible damage to brain cells. Typically, the onset of hypoxemia is followed by cardiac arrest in individuals who die from drowning (Bierens et al., 2016; Juya et al., 2019; Reizine et al., 2021).

As alluded to earlier, it can be a complex process to ascertain if death occurred as a consequence of drowning or if the body was deposited into a body of water post-mortem. Yet, advances in forensic technology have allowed scientists to come closer to a means of determining drowning as a cause of death. Water aspiration is an integral part of the drowning process. Once water enters the lungs, it is able to enter the blood circulation (Bierens et al., 2016). However, the aspiration of water also encompasses the entry of debris, algae, and microorganisms, present in the surrounding environment, into the body. Diatoms, a type of plankton that inhabits most bodies of water, have been singled out as promising markers that could be identified in victims who died from drowning. The isolation of diatoms in various organs is hypothesised to be possible at high levels only if a person has gone through the drowning process, which involves the movement of water from the alveoli in the lungs, and then to the blood, while a person is still alive (Shalini Dhyani & Kavita Bramhanwade, 2023; Zhou et al., 2020).

Figure 3: Diatom test (Dhyani & Bramhanwade, 2023).

Is "Dry Drowning" Real?

"Dry drowning" or "secondary drowning" are terms that arose after autopsy reports of individuals who were suspected to have died from drowning did not mention the presence of water in the lungs (Modell et al., 1999). Furthermore, the media propagated these terms to describe cases where children who were rescued from bodies of water with seemingly no symptoms died soon after, due to complications from water aspiration (Stern & Thompson, 2022). In reality, both of the terms do not have a medical foundation and should be avoided in articles, research papers and health policies. Instead, drowning should be referred to as non-fatal and fatal, as it is a multi-step process from which a person can recover if prompt treatment is provided. Although macroscopic signs of water may not be observable in rare circumstances, it is almost certain that a person who has died from drowning will have water accumulating in the lungs and stomach on a microscopic level. In addition, the absence of water in the lungs may be an indicator that the person was not a victim of fatal drowning, so the use of "dry drowning" as a diagnosis may lead to the true cause of death remaining undetermined. This can be the case when a person dies due to natural causes, such as a myocardial infarction or a cerebral infarction, near or in a body of water. Under such circumstances, a person would be dead before they are submerged in water, meaning they will not gasp for air and aspiration of water into the lungs would not occur (Armstrong & Erskine, 2018; Szpilman et al., 2018). However, it is still important for a victim of non-fatal drowning to be examined by a medical professional as water aspiration may lead to critical symptoms, like coughing and hyperventilation, a few hours after an incident (Stern & Thompson, 2022).

Drowning While Under the Influence of Alcohol and Drugs

The consumption of alcohol and recreational drugs is a recognised risk factor for fatal drowning, especially in males. Alcohol acts as a depressant when introduced into the body, affecting inhibitory pathways in the central nervous system and altering the actions of neurotransmitters (Costardi et al., 2015). The physiological changes brought on about by alcohol are reflected by changes in behaviour. Individuals who have been drinking can become more likely to engage in risky activities and may be less capable of evaluating how dangerous a situation is. Resultantly, people who have a high level of alcohol in their blood, or those who have taken drugs that similarly impact their cognition and behaviour, can be more prone to entering a body of water (Strasiotto et al., 2022). Studies have shown that the risk of fatal drowning significantly increased for people who had been boating while under the influence of alcohol, compared to those who had undetectable levels of alcohol in the blood (Driscoll, 2004). Researcher Pajunen and colleagues also highlighted that in 1697 drowning cases in Helsinki, 14.5% of the incidences could be attributed to the intake of drugs. Forensic investigators can use toxicology to confirm if a victim of drowning had been under the influence of drugs or alcohol (Pajunen et al., 2017). Sampling the fluid found within the eye, known as the vitreous humour, is seen as an established method of detecting alcohol levels post-mortem (Kugelberg & Jones, 2007).

Figure 4: Alcohol and water safety (Royal Life Saving Australia, n.d.).

Drowning in Cold Water

Fatal drowning predominantly occurs upon submersion in water that is colder than normal body temperature. Water temperatures below 25 degrees Celsius can elicit hypothermia and a phenomenon known as cold shock. When rapidly coming into contact with cold water, sensory receptors on a person’s skin (cold nociceptors) can activate multiple physiological pathways to thermoregulate the body. The body aims to heighten its metabolic rate to compensate for the reduction in body temperature, increasing the pumping function of the heart, the ventilation rate, and blood pressure to achieve this. Moreover, the cold shock response can stimulate gasping for air, interfering with a person’s attempts to hold their breath when they are submerged in water. Therefore, victims have a higher chance of aspirating water and experiencing cellular injury due to hypoxia (Bierens et al., 2016; Tipton, 2003).

Despite the general consensus that fatal drownings generally occur in cold water, extremely cold temperatures can have protective effects. This is demonstrated by the case of Anna Bågenholm, a doctor who was submerged in freezing water, trapped under layers of ice, for approximately 40 minutes. Bågenholm was rescued and brought to the hospital, at which point her body temperature had plummeted to 13.7 degrees Celsius (from a normal body temperature of 37 degrees Celsius) and her heart had not been beating for approximately 2 hours. After a procedure which increased her body temperature back to normal, Bågenholm’s heart was restarted (Cox, 2013). This fascinating case demonstrated how hypothermia has the potential to halt a person’s metabolism to the point where hypoxia caused by asphyxiation does not critically damage tissues in the body, because of their reduced demand for oxygen. Studies have similarly found that considerably decreasing body temperatures can protect cells from DNA damage and prevent cellular injury (Baird et al., 2011).

Figure 5: Cold water shock (Boater's Academy, n.d.).

Conclusion

The incidence of fatal drowning is alarmingly high worldwide, with young children being one of the most vulnerable groups. On the physiological level, drowning is an asphyxial death caused by an individual’s breathing being obstructed. Within minutes, a person is deprived of oxygen, which leads to irreversible cellular injury, brain anoxia and cardiac arrest. Drowning is a cause of death that is challenging to determine, with forensic pathologists needing to exclude all other potential explanations for death before making the diagnosis. Advances in forensic science have aided the understanding of the drowning process, with certain risk factors and unique phenomena being observed. Yet, it is imperative that interventions are made to address the high mortality that is attributed to drowning. Educating the public about what can put them at risk of drowning and dispelling myths about ‘dry drowning’ can act as the first steps to reducing deaths from drowning.

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