Chapter 112

• Immersion and diving produce physiologic effects from increased hydrostatic pressure and its effects on the behavior of gases.
• When diving with compressed air or other breathing gases, the body takes up extra nitrogen or other inert gas, which must be allowed to leave through the lungs gradually to avoid decompression sickness (DCS). DCS occurs when gas comes out of solution and forms bubbles in body tissues, which causes pain or neurologic symptoms by obstruction of blood flow and initiation of secondary inflammatory events.
• DCS is treated by prompt administration of high-flow O2 and hydration. Oxygen recompression therapy is definitive treatment for symptom resolution and avoiding recurrence, even if delayed 1 or 2 days.
• Arterial gas embolism is usually the result of pulmonary overpressurization during ascent from diving with compressed gas and may occur at shallow depths. Arterial gas embolism is the second leading cause, after drowning, of fatalities in recreational diving.
• Near drowning (ND) is caused by asphyxia underwater, which may or may not be associated with aspiration. The primary injuries are to the brain, heart, lungs, and kidneys.
• In young adults, ND is often associated with drug or alcohol ingestion and may be accompanied by traumatic injuries.
• ND may be complicated by acute respiratory distress syndrome; its onset may be delayed or aggravated by aspiration of gastric contents or other foreign debris and pneumonia.
• ND may be complicated by pneumonia (or sepsis) caused by unusual pathogens present in contaminated water. Prophylactic antibiotic treatment is not indicated.

Recreational activities involving water are enjoyed by millions of swimmers, boaters, and divers of all ages with various degrees of physical skill and judgment. However, the water environment is deceptively hazardous, and too often, swimmers or divers venture into peril with deadly results. In many situations, they ignore their physical limitations or impair their faculties with alcohol or other drugs. In other situations, such as with young children, the encounter with water is unsupervised or unexpected and frequently results in death by drowning. There are millions of recreational divers and many more recreational swimmers in the United States, which translates to thousands of diving accidents, drowning, and near drowning (ND) episodes each year. The exact number of such aquatic incidents and their effect on the health care system are difficult to estimate, but there may be more than 80,000 episodes per year in the United States. Victims often survive the incident only to die hours or days later in the hospital. Thus, the intensive care specialist should be knowledgeable about the clinical consequences and management of diving accidents and ND.

Underwater environments produce physiologic changes as a result of the direct effects of increased hydrostatic pressure and its effects on the physical behavior of gases. Pressure is measured in units of force per area, which is expressed commonly in several convenient forms (Table 112-1). The pressure of the atmosphere at sea level is approximately 760 mm Hg (14.7 pounds per square ...

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