Arterial Gas Embolism
Arterial gas embolism is a potentially catastrophic event that occurs when gas bubbles enter or form in the arterial vasculature and occlude blood flow, causing organ ischemia. Arterial gas embolism can cause CNS ischemia with rapid loss of consciousness, other CNS manifestations, or both; it also may affect other organs. Diagnosis is clinical and may be corroborated by imaging tests. Treatment is 100% oxygen and immediate recompression.
(See also Overview of Diving Injuries.)
Gas emboli may enter the arterial circulation in any of the following ways:
From ruptured alveoli after lung barotrauma
From within the arterial circulation itself in severe decompression sickness
Via migration from the venous circulation (venous gas embolism) either via a right-to-left shunt (patent foramen ovale, atrial septal defect) or by overwhelming the filtering capacity of the lungs
Even an otherwise asymptomatic venous gas embolism can cause serious manifestations (eg, stroke) in the presence of a right-to-left shunt. Venous gas embolism that does not enter the arterial circulation is less serious.
Although cerebral embolism is considered the most serious manifestation, arterial gas embolism can cause significant ischemia in other organs (eg, spinal cord, heart, skin, kidneys, spleen, GI tract).
Symptoms occur within a few minutes of surfacing and may include altered mental status, hemiparesis, focal motor or sensory deficits, seizures, loss of consciousness, apnea, and shock; death may follow. Signs of pulmonary barotrauma or type II decompression sickness may also be present.
Other symptoms may result from arterial gas embolism in any of the following:
Diagnosis is primarily clinical. A high level of suspicion is necessary when divers lose consciousness during or immediately after ascent. Confirming the diagnosis is difficult because air may be reabsorbed from the affected artery before testing. However, imaging techniques that may support the diagnosis (each with limited sensitivity) include the following:
Sometimes decompression sickness can cause similar symptoms and signs (for a comparison of features, see Table: Comparison of Gas Embolism and Decompression Sickness).
Comparison of Gas Embolism and Decompression Sickness
Divers thought to have arterial gas embolism should be recompressed promptly. Transport to a recompression chamber takes precedence over nonessential procedures. Transport by air may be justified if it saves significant time, but exposure to reduced pressure at altitude must be minimized.
Before transport, high-flow 100% oxygen enhances nitrogen washout by widening the nitrogen pressure gradient between the lungs and the circulation, thus accelerating reabsorption of embolic bubbles. Patients should remain in a supine position to decrease the risk of brain embolism. Mechanical ventilation, vasopressors, and volume resuscitation are used as needed. Placing patients in the left lateral decubitus position (Durant’s maneuver) or Trendelenburg position is no longer recommended.
Strongly consider arterial gas embolism if patients have neurologic symptoms within minutes after surfacing or manifestations of ischemia in another organ.
Do not exclude arterial gas embolism based on negative test results.
Start high-flow 100% oxygen and initiate transport to a recompression chamber if gas embolism is suspected.