An air embolism, or more accurately, a gas embolism, occurs when one or more gas bubbles enter a vein or artery. This can block the passage of blood, and it can be life-threatening.
Depending on where the blockage occurs, symptoms and severity vary. Air embolism is one of the leading causes of death in the diving community.1
Air embolism can be caused by a number of factors – most commonly diving – but certain medical procedures can also cause gas bubbles in the blood. The exact prevalence of air embolisms is not known; more minor cases may go untreated and can be without symptoms.
This article will look at the causes, symptoms and diagnosis of air embolism. It will also include ways to avoid the condition when diving.
Fast facts on air embolism
Here are some key points about air embolism. More detail and supporting information is in the main article.
Air embolisms are most often formed during scuba diving
Air bubbles in the veins are not as serious as those in arteries
Arterial gas embolisms can cause strokes
Just 2-3 ml of air injected into the cerebral circulation can cause death
Some medical procedures can cause air embolism
An estimated 57% of orthopedic surgeries produce air embolisms
Symptoms of air embolism include aching joints, feelings of stress, chest pain and tremors
The best treatment for air embolism is recompression in a hyperbaric chamber
Ways to avoid embolisms while diving include avoiding alcohol and resurfacing slowly.
What is an air embolism?
An air embolism is a gas bubble trapped within a vein or artery.
An embolism, in general, refers to anything untoward that has become trapped within the vascular system.
An air embolism, specifically, is a bubble, or bubbles, of gas trapped within the blood vessels. The bubbles will, at some point, cut off the blood supply to a particular area of the body.
Air embolism can easily cause significant and permanent damage to the central nervous system and as such must be treated as an emergency.
A venous embolism is not as serious as an arterial embolism, which is itself not as serious as a cerebral embolism. However, all of the above have the potential to cause severe damage to organs and systems if left unchecked.2
Some medical procedures can cause small amounts of air to enter the venous system; via an intravenous drip, for instance. In general, these are stopped at the lungs and do little or no harm. In rare cases, they can reach the heart and disrupt its workings.
Arterial gas embolisms are much more serious. The embolism might potentially prevent oxygenated blood from reaching the target organ and cause ischemia (an inadequate blood supply to an organ); if the heart is affected it can produce a heart attack.
If an arterial gas embolism reaches the brain, it is referred to as a cerebral embolism and can cause a stroke.
An injection of 2-3 ml of air into the cerebral circulation can be fatal. Just 0.5-1 ml of air in the pulmonary vein can cause a cardiac arrest.3
Diving is the most common cause of air embolism.
Decompression sickness: also known as “the bends,” an embolism can occur when a diver surfaces too rapidly. As a diver descends, their body, along with the gas they are breathing (oxygen and nitrogen) is under increasing pressure. The diver constantly uses the oxygen, but the nitrogen pools in the diver’s tissues.
If the diver returns to the surface too swiftly, the nitrogen is not given the chance to be reabsorbed into the blood and will leave the tissue as bubbles of gas.
A good analogy to help understand this process involves a bottle of carbonated soda. When the bottle is sealed, the carbon dioxide cannot be seen because it is under pressure. However, if the pressure is quickly released by opening the cap, the carbon dioxide forms into readily visible bubbles.
If the cap is slowly released in stages, the bubbles will not form.
Pulmonary barotrauma: if a diver holds their breath during a rapid ascent, trauma can be caused to the lining of the lungs. As the pressure decreases during the ascent, the volume of the air in the lungs increases. If the breath is held voluntarily, the small air sacs of the lungs (alveoli) can rupture. These tears can allow gas to pass into the blood.
Other causes of air embolism can be iatrogenic (caused by a medical intervention). These can include:
Intravenous drip: most commonly via disconnected central venous catheterization
Hemodialysis: treatment for kidney failure
Laparoscopic insufflations: otherwise known as keyhole surgery, air is sometimes pumped into the space between the organs and the skin to clear a passage for the surgeon to work
Open heart surgery
Lung biopsy: removal of a section of lung for examination
Radiologic procedures: specifically where the injection of dye is necessary
Childbirth: particularly cesarean section
Endoscopic retrograde cholangiopancreatography (ERCP): a procedure designed to examine the pancreatic and bile ducts, ERCP involves injecting a dye into the region via an endoscope.4