INTRODUCTION

While various necessary military occupations put service members at increased risk for drowning, particularly those serving in the Navy and Marine Corps, this risk is mitigated through methodical training and operational risk management processes. However, drowning events in combat and operational environments can occur and are highly influenced by the tactical environment. In civilians, drowning is thought to be preventable in over 90% of cases.1-2 As a result of the significant human, social, and economic tolls of drowning, the World Health Assembly adopted their first resolution regarding drowning prevention in 2023.3 The purpose of this clinical practice guideline provides an overview of drowning and associated conditions based on the best available current medical evidence. It should be used as a standardized framework to guide first responders, prehospital emergency medical service personnel, and medical department personnel in evaluating, diagnosing, and managing common in-water emergencies. Caregivers supporting operations with an increased risk of drowning should review this CPG with the entire medical team including first responders.

MILITARY OCCUPATIONS WITH DROWNING RISK AND EPIDEMIOLOGY

Various military occupations involve significant water exposure and carry a risk of drowning. These include but are not limited to naval operations at sea, military special operations, combat swimmers, divers, and amphibious assault units. Each unit has risk management measures in place to mitigate the risk of drowning events and subsequently provide immediate aid.

Between 2013 and 2017, 359 recreational and line of duty drowning cases were identified amongst active-duty service members. Generally, members of the Marine Corps are at highest risk as well as members working within motor transport occupations. Off duty alcohol related incidents and alcohol use disorder continue to play a significant factor in drowning risk.2,4

Combat related drowning incidents have been associated with a mortality as high as 37.5% and are often related to vehicle roll overs. One 2-year epidemiology study found that combat related drowning represents 3% of all combat deaths.5-6

Man-overboard events aboard naval vessels at sea are uncommon occurrences but are associated with a high mortality when they occur. Between 1970 and 2020 there were 220 man-overboard events on U.S. Naval subsurface and surface vessels involving 352 casualties with an associated 72% mortality.7

Naval vessel collisions at sea impacting the integrity of the ship’s hull can result in highly lethal drowning events. The 2017 USS Fitzgerald and USS John S. McCain collisions with separate large civilian commercial ships both resulted in significant hull breaches below the waterline. In the two events, there were 85 reported casualties from the combined warship crews, 20% (17) died from drowning.

The epidemiology of drowning incidents during amphibious vehicle training is unknown, but they do occur. In 2020 an Amphibious Assault Vehicle (AAV) carrying 15 Marines and 1 Sailor took on water and sunk during a training exercise. Ultimately 8 Marines and 1 Sailor died from drowning. One severely injured Marine required ongoing critical care and respiratory support.8

CIVILIAN EPIDEMIOLOGY OF DROWNING

Reported incidence of 360,000 to over 500,000 civilian deaths attributed to unintentional drowning annually, not including boating accidents or those related to natural disasters. *These numbers are thought to be underreported. 2, 9-10

Worldwide, children ages 1-4 have the highest rates of drowning, followed by children ages 5-9. Boys are twice as likely to die from drowning.3

It is the leading cause of death or contributing factor among scuba divers (100-150/year). Primary etiology of death can be difficult to determine as distinction between equipment malfunction or medical emergency can be challenging.10-12

PATHOPHYSIOLOGY OF DROWNING

Drowning occurs when water fills the airways for any reason. It is important to note that progressive aspiration of water can result in hypoxemia. If loss of consciousness occurs, the continued hypoxemia can result in bradycardia and cardiac arrest. In the lungs, aspiration can cause a washout and destruction of alveolar surfactant resulting in severe hypoxia, alveoli derecruitment, reduced pulmonary compliance and noncardiogenic pulmonary edema, all of which can complicate ventilator management. It should also be noted that there is no such thing as “Near Drowning.” Correct terminology includes “Non-Fatal Drowning” and “Fatal Drowning.”

Immersion in water when associated with panic, exhaustion, inadequate water competency, a medical emergency such as lethal cardiac dysrhythmia or seizure, or effects of hypo/hyperthermia can lead to drowning from one of the following mechanisms:10-15

- Airway below the water’s surface → breath hold breakpoint (inability to resist urge to breathe due to hypercapnia and hypoxemia) → progressive aspiration and subsequent hypoxemia (see below) → loss of consciousness (LOC) → apnea and passive airway flooding → bradycardia → cardiac arrest.1
- Aspiration (either sea water or fresh water) causes a degree of surfactant washout/destruction increased alveolar surface tension and diminished integrity of the alveolar-capillary membrane atelectasis/ derecruitment and disruption of the alveolar capillary membrane → unregulated fluid shifts resulting in noncardiogenic pulmonary edema, reduced pulmonary compliance ( ~10-40% with as little as 1-3cc/kg water) → right to left shunting resulting in hypoxemia.1
- Cold water submersion → inadvertent gasp for air (“cold shock response”) → tachypnea, vasoconstriction, tachycardia from sympathetic surge → arrhythmias (especially in patients with long QT syndrome) or parasympathetic mediated bradycardia (“diving response”), altered mental status, diminished strength, and coordination.1 Table 1 shows expected survival times in cold water.

Table 1. Expected survival time in cold water

DROWNING PREVENTION

In the civilian and military environment, one of the most important principles in drowning management is to first prevent drowning. Examples of prevention and operational risk management in high-risk military occupations include:

- Sailors assigned to naval vessel are indoctrinated in the principles of universal damage control, which among other tenets includes techniques to control (e.g., shoring materials, secure hatches) or remove flooding water (e.g., pumps) when the hull is breeched. Hull integrity is typically controlled with shoring materials such as mattresses, pillows, canvas materials, hydraulic jacks and wooden wedges, beams, plugs or blocks.
- Amphibious operations are a particularly high-risk activity as evidenced by a recent 2020 amphibious assault vehicle tragedy during a training event. Of issues that led to the nine drowning deaths, failure to apply appropriate operational safety protocols contributed, highlighting the importance of prevention.8 With this risk, all personnel assigned to these platforms are required to complete both intermediate level swim qualifications and submersible vehicle egress training. All personnel have received some degree of Tactical Combat Casualty Care training in order to provide buddy aid in the event of an emergency. Training evolutions require the presence of Marine Corps Instructors of Water Survival who are trained for in-water rescue.
- Implementation of risk management measures during dive and other high-risk water operational and training evolutions is critical in prevention of drowning. These measures include pre-evolution safety briefs, trained standby and safety divers, swim buddies, on scene medical providers, water rescue crafts on site, wearing personal flotation devices, drilling man-overboard procedures, and use of light sticks for night training.
- Careful consideration must be given to the potential risks of conducting open sea operations in extreme environmental conditions such as rough sea state or heavy swell. In these extreme conditions, operations or training should be altered (when possible) to mitigate the risk of drowning and other mishaps.
- Divers should undergo thorough review of dive plan prior to scheduled dives to include anticipated depth/time profile ensuring adequate air supply in addition to routine pre-dive equipment safety checks.

PHASES OF TREATMENT 11,15

1. Initial resuscitation
2. Advanced prehospital care
3. Emergency Room (ER) / Intensive Care Unit (ICU) Care