CHAPTER 132

### KEY POINTS

• Immersion and diving produce physiologic effects from increased hydrostatic pressure and its effects on the physical behavior of gases.

• Diving with compressed air (or other breathing mixtures) causes the body to take up extra nitrogen or other inert gases in proportion to the pressure change. During ascent, these dissolved gases must leave gradually through the lungs to avoid decompression sickness (DCS).

• DCS is caused by gases leaving solution and forming bubbles in body tissues, leading to musculoskeletal pain (bends) or neurologic symptoms due to direct vascular damage, ischemia, edema, and inflammation.

• DCS usually manifests within minutes to hours of surfacing and is emergently treated with high-flow O2 and the administration of fluids. Oxygen recompression in a hyperbaric chamber is the definitive treatment for signs and symptoms and for the prevention of recurrences, even if delayed 1 or 2 days.

• Arterial gas embolism (AGE) is the result of overexpansion of the lungs during ascent from diving with compressed gas. It is usually associated with rapid ascent and CNS symptoms and after drowning, is the second leading cause of fatalities in recreational diving. AGE is a medical emergency that also occasionally occurs in the hospital setting.

• Drowning is defined by asphyxia in water, and is usually associated with aspiration of water. In survivors, the primary injuries are to the brain, heart, lungs, and kidneys. Drowning is common in children, and in young adult males, and is often associated with drug or alcohol ingestion.

• Drowning may be accompanied by traumatic injuries and complicated by acute respiratory distress syndrome (ARDS), often of late onset and often aggravated by aspiration of gastric contents or other foreign debris.

• Drowning may be complicated by pneumonia (or sepsis) caused by unusual pathogens present in contaminated water. However, the prophylactic administration of antibiotics is not recommended.

Water sports are enjoyed by millions of people of all ages throughout the world, but the water environment is deceptively hazardous, and swimmers, divers, and boaters display various degrees of skill, experience, and judgment. Too often, inexperienced swimmers or divers venture into perilous conditions with deadly results. In many cases, they have ignored their physical limitations or impaired their faculties with alcohol or other drugs. In some situations, such as with young children, the encounter with water is unsupervised or unexpected. The exact numbers of such aquatic incidents worldwide and their effect on health care systems are difficult to estimate, but according to the Global Burden of Disease the overall death rate by drowning is around 8.4/100,000 people. This converts to more than half a million deaths per year and probably several times that number of drowning episodes. Many victims survive the incident only to die hours or days later in the hospital. In the United States and other westernized nations, there are also several million active sports divers, and there are several thousand diving accidents each year. Thus, the consequences and management of victims of drowning incidents and recreational ...

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