Decompression illness (DCI) encompasses decompression sickness (DCS) and arterial gas embolism. The term decompression illness refers to inert bubble-induced dysbaric disease regardless of the location of the bubbles, which may be in the tissues or in the intravascular spaces. The bubbles arise due to a rapid drop in atmospheric pressure or due to pulmonary barotrauma.
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Epidemiology
Decompression illness can occur in:
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divers if ascent to the surface is too rapid
the reported incidence in sports divers is 3 in 10,000 dives
in commercial divers the incidence is up to 10 in 10,000 dives
workers leaving a caisson (pressurised chamber)
during unpressurised flight to high altitude
extra-vehicular activity in space
Clinical presentation
Symptoms depend on the location of the bubbles, and vary from mild to severe:
bone and/or muscle pain, typically in the shoulders, and less frequently in the elbows, knees or ankles
headache and focal neurological deficits, such as paralysis, visual disturbances or vertigo
death
For a further discussion please see decompression sickness.
Pathology
According to Henry's Law, the solubility of a gas in a liquid is proportional to the partial pressure of a gas over the liquid. For divers, pressure increases by one atmosphere for every additional 10.06 meters in depth, causing more gas to be dissolved in blood and body fluids. Oxygen is metabolized, but gases like nitrogen and helium accumulate. On ascent these gases leave solution and the gas bubbles expand. If ascent is too rapid this causes decompression illness.
Pulmonary barotrauma can occur during diving descent (lung squeeze) or ascent (pulmonary overinflation syndrome). Gas can enter lung parenchyma or vessels through tears and can cause arterial gas embolism.
Bubbles can block vessels, cause spasm or cause endothelial damage which activates both the clotting cascade and inflammatory mediators leading to increased permeability, edema and ischemia.
Radiographic features
Chest radiograph is important to exclude pneumothorax prior to treatment in a hyperbaric chamber.
For further discussion please see decompression sickness.
Treatment and prognosis
General treatment options include:
FiO2 100% oxygen
hyperbaric chamber if there is no inner ear barotrauma