The Divers Alert Network (DAN) is a 501(c)(3) not-for-profit organization dedicated to scuba diving safety and education. It is funded through a membership association that allows DAN to act as a safety resource for recreational scuba divers. DAN is located in Durham, North Carolina and associated with Duke University Medical Center. DAN also responds to over 16,000 requests for information and assistance each year. This includes over 2,000 emergency assistance calls, almost 14,000 dive safety and medical information requests and over 1.000 e-mail inquiries.

There are approximately 1,000 treated cases of decompression illness reported to DAN each year among U.S. citizens. These cases are reported from treatment facilities around the world. The actual number of cases could be higher since all divers with decompression illness may not seek treatment. There has also been between 67 and 104 recreational scuba fatalities annually since 1990.

Decompression illness (DCI) includes both decompression sickness (DCS) and arterial gas embolism (AGE). DCI was introduced because the clinical signs and symptoms of DCS and AGE are similar and difficult to differentiate, even for a physician trained in diving medicine. Decompression sickness is primarily a disease of exposure to high partial pressures of nitrogen. Exposure means depth and time breathing compressed gas, and can be cumulative, such as the number of dives made per day and number of days diving. Arterial gas embolism is usually the result of pulmonary overpressurization which occurs during ascent to the surface. This overpressurization can produce tiny tears in lung tissue which allows air to enter lung tissue and the pulmonary vasculature and ultimately produce stroke-like cerebral signs and symptoms.

The expansion and compression of a gas volume in the lung can be explained by Boyle’s Law. Boyle’s Law states “If temperature remains constant, the volume of a gas is inversely proportional to its pressure.” This is the principal mechanism of injury resulting in AGE. It is the excess of nitrogen that can produce bubbles in tissue leading to DCS symptoms. Henry’s Law of partial pressure states, “The amount of gas that will dissolve into a liquid is directly proportional to the partial pressure of that gas.” In other words, the diving force for the absorption of the inert gas nitrogen is the pressure gradient created by the increase partial pressure of nitrogen in compressed gas.

There is no single presentation which is classic for decompression illness. Nitrogen will be absorbed by all body tissues and fluids. Symptoms, therefore, may present in any area of the body. A physical and neurological examination will be necessary to diagnose decompression illness. There is rarely any outward sign of injury that would indicate severe or even mild symptoms. There are no lab tests or x-rays that can be performed to detect decompression illness. In the emergency care setting, it is important to begin an accurate record of symptoms and symptom onset in order to establish baseline information on the injury and the evolution of symptoms. A diagnosis does not need to be made prior to arriving in the emergency department. Because decompression illness requires treatment in a hyperbaric chamber, the rescuer should verify the recent history of breathing compressed gas while under water (scuba diving). Emergency care, including 100% oxygen, should not be withheld when DCI is suspected.

Approximately 54% of all symptoms of DCI will occur in the first 30 minutes following the scuba dive. About 68% will occur within the first two hours of the dive and 95% will have developed within 24 hours. Divers may present with both acute severe symptoms, and mild to moderate neurological symptoms hours after diving. There are seven symptoms considered the most frequent symptoms of DCI.