Epidemiology
Drowning remains a leading cause of unintentional death and unintentional injury [1]. The Centers for Disease Control (CDC) place the incidence of non-fatal drowning at between 4,000 and 7,000 cases per year [1–5]. Fatalities range from 3,200 and 6,000 cases per year [1,4,5]. The incidence of non-fatal drownings ranges from one to four times that of fatal drownings [3]. Over 50% of all non-fatal drownings require hospitalization [1].
Drowning and near drowning are the second most common unintentional injuries for ages 1–4 and 15–19 [2,6]. In infants less than 1 year old, most drownings occur in the bathtub [7]. For children less than 4 years old, most drownings occur in private pools. For age greater than 15 years the predominant drowning locations include natural water settings such as beaches and lakes [8]. Fatalities are higher for victims less than 4 years old. Compared with females, males have twice the rate of non-fatal and five times the rate of fatal drowning [1]. Over half of adolescent and adult drownings involve alcohol or illicit substance use [8,9]. Approximately 35% of persons who drown under the age of 20 are classified as accomplished swimmers [10]. Preexisting medical conditions may play a role as well, as noted in children with seizures having a four-fold increase in risk compared to the general population [3].
Drowning accidents involving children commonly result from lapses in adult supervision. In the majority of child drownings, the child was under the care of one or both parents and was “out of sight” for less than 5 minutes [9]. While surveyed pool owners favor cardiopulmonary resuscitation (CPR) requirements, less than half of these households actually have a CPR-qualified individual. Of pool owners favoring isolation fencing around pools, only one-third had their pool fenced. The risk of drowning or near drowning is 3–4 times higher in unfenced than fenced pools [5].
Epidemiological and public health data highlight the role of education, planning, and other community-level interventions in drowning prevention. Estimates of preventable drowning deaths are as high as 80% [3]. Many EMS systems participate in drowning prevention efforts, such as education and water safety programs.
Pathophysiology of drowning
Drowning is commonly defined as suffocation and death as the result of submersion in a liquid environment [5,9,10]. Historically, two types of drowning have been described: wet and dry. “Wet drowning” is the aspiration of material such as water, sand, vomitus, etc [11–13]. This material can lead to pulmonary edema, pneumonitis, and surfactant dysfunction, impairing gas exchange. “Dry drowning” involves minimal aspiration; the inhaled liquid triggers laryngospasm, resulting in suffocation. Experts have questioned the mechanisms and clinical significance of this differentiation. Some postulate that decreasing level of consciousness and increasing hypoxia will eventual break any “spasm,” allowing liquid to enter the lungs [9,14]. Submersion describes the airway opening beneath the surface of the liquid medium–air interface, while immersion is the splashing of liquid in or about the airway.
Classically, drowning begins as a period of panic and struggle, but in a minority of cases (for example, cervical trauma or seizure), this initial phase may not be present [9,12]. Death from drowning ultimately results from suffocation, tissue hypoxia, and cardiac arrest. Successful resuscitation after a drowning-induced cardiac arrest is rare.
Historically, drowning education materials have emphasized differences in fresh-water and salt-water drowning, citing the theoretical electrolyte and fluid shifts occurring with each situation. However, current practice downplays the importance of these differences [5,11]. Some consideration of the water contaminants may be clinically important in the hospital setting, and the EMS insight into those scene variables may be helpful to hospital staff.
Cerebral hypoxia plays a significant role in the functional recovery of the victim. Many drowning survivors suffer some permanent neurological damage, with up to 10% suffering severe lasting effects [13,15]. The duration of hypoxia is correlated with submersion time and is an important determinant of recovery [11,13]. Another important consideration is the neuroprotective effect of hypothermia. The medical literature and the lay press are replete with examples of survival after lengthy submersion in frigid or near freezing water. Cold-water submersion does not guarantee survival but may play a significant role in management decisions during and after the resuscitation [11,16].
The term “secondary drowning” typically refers to patients who survive the submersion injury for some period of time, yet later develop respiratory failure and death attributed to the original submersion event [5]. This deterioration may occur from hours to days later [8,13]. While the term “drowning-related death” has been proposed to describe deaths occurring more than 24 hours after a submersion, this definition is not widely used [10].
“Near drowning” is defined as immediate survival after a submersion event [13]. While most of these individuals may survive, many will deteriorate. The definition has some variability among authors and published sources, with some including asphyxia or loss of consciousness in the definition [5,9,10]. There remain ongoing efforts to better formalize definitions, including the use of the term “drowning” (defined as a process resulting in primary respiratory impairment from submersion and immersion in a liquid medium) to classify all events regardless of outcome as drowning [3]. To date, this has not been widely accepted in medicine or by the lay public. The remainder of this chapter will distinguish drowning (death) from near drowning.
