Arterial gas embolisms are caused by the entry of gas into the pulmonary veins or directly into the arteries of the systemic circulation.

• Gas may enter arteries as a result of overexpansion of lungs by decompression barotraumas or result from paradoxical embolus.
• Emboli can travel to any artery, but the most serious consequences occur when they affect the cerebral or coronary circulation.
• Synonym(s): Gas embolism; Air embolism

Incidence

• Predominant age: Young adult
• Predominant sex: Male > Female.

Prevalence
Estimated (based on injury/mortality reports collected by Divers Alert Network) to occur in ~4/100,000 sport divers per year

• Surgery: Recent craniotomy with patient in upright position, cardiothoracic surgery (with cardiopulmonary bypass), hip replacement, cesarean section
• Scuba: Arterial gas embolism is the most serious and rapidly fatal of all scuba diving injuries and is 2nd only to drowning as the leading cause of death associated with sport diving. Arterial gas embolism occurs on ascent from alveolar rupture; time to the manifestation of symptoms is nearly always < 10 minutes.
• History of patent foramen ovale has been associated with a >4-fold increase in decompression illness events and 2-fold more ischemic brain lesions than in divers without this condition.

• Strict adherence to diver safety protocols
• No diving after any dive injury or with any medical condition until evaluated and approved by a physician knowledgeable about diving medicine

• Cerebral air embolism:
  • Air bubbles occlude the brain vasculature.
  • Intracranial pressure (ICP) increases.
  • Unequal distribution of blood in the brain causes hyperemia and ischemia.
  • Small bubbles irritate vascular wall, causing breakdown of blood–brain barrier; small size allows rapid absorption and may cause only brief interruption of cerebral blood flow.
  • Larger air bubbles take longer to absorb (up to several hours) and can cause primary ischemic injury with diffuse brain edema and increased ICP.
• Coronary air embolism is caused by obstruction of coronary arteries by an air bubble.
  • Temporary ischemia of myocardium
  • Labile blood pressure (BP)
  • Arrhythmias
  • Cardiac failure and/or arrest
• Obstruction is possible in any artery. Small emboli in the vessels of skeletal muscles and viscera are well tolerated.

• Pulmonary barotrauma leading to arterial gas embolism also can cause pneumomediastinum, subcutaneous emphysema, pneumopericardium, pneumothorax, and pneumoperitoneum.
• Always consider the possibility of decompression sickness in addition to arterial gas embolism in any scuba diver who has recently completed a dive.