A pulmonary embolism (PE) occurs when a foreign substance blocks an artery in your lungs, stopping blood flow. It’s usually caused by a blood clot, but can sometimes be due to lipid, air, or tumor cells.

A pulmonary embolism (PE) is a serious medical condition. It usually occurs when a blood clot elsewhere in the body breaks loose and travels up to the lungs, blocking a pulmonary (lung) artery.

Experts estimate that up to 900,000 people each year in the United States experience a PE.

Healthcare professionals have identified several risk factors associated with PE. These are mostly modifiable, which means you can take steps to help lower your risk of experiencing a blood clot and PE.

Keep reading to learn more about the primary and secondary causes of PE and possible risk factors.

A PE is most commonly caused by a blood clot in one of the deep veins in your lower body, such as the legs. This is known as deep vein thrombosis (DVT).

If a DVT is left untreated, the blood clot could break loose. Part of it could then travel up through your bloodstream and block one of your lung arteries.

To better understand the causes of blood clots and DVT, experts use the Virchow Triad, developed by Dr. Rudolph Virchow in the 19th century. It outlines three possible changes that can occur in the blood that can cause a DVT:

  • Hypercoagulability: The blood has a higher risk of clotting due to its thickness and stickiness.
  • Hemodynamic changes: Blood flow alterations in the vessels occur, such as due to sitting too long or turbulence (very quick blood flow).
  • Endothelial damage: This refers to damage to the blood vessel walls.

In rare cases, a PE may be caused by other foreign substances blocking the pulmonary arteries.

Pulmonary tumor embolism

In rare cases, a tumor can break loose and cells could travel up to the pulmonary arteries, causing a PE.

According to a 2022 review, a pulmonary tumor embolism (PTE) is most commonly associated with liver cancer and other adenocarcinomas. These are cancers that begin in the cells of the glands that produce mucus.

Other types of cancer that have been linked with PTE include:

Vascular air embolism

A vascular air embolism (VAE) is a rare but serious complication that may occur if air is introduced into the venous system. It’s usually iatrogenic, which means it occurs as a result of treatment like surgery.

The most common causes of VAE are central vascular access and open neurosurgical procedures. Some other high risk surgeries may include:

Fat embolism

Fat embolism (FE) is when you have small deposits of fatty lipids circulating in the bloodstream, which can cause inflammation. It’s usually caused by bone fractures and orthopedic procedures, but may also be caused by:

In rare cases, an FE may affect the pulmonary arteries.

FE may cause serious complications of the lungs, skin, eyes, and central nervous system.

​Amniotic fluid​ embolism

Amniotic fluid embolism (AFE) is a rare but serious complication that may occur during childbirth. It occurs when amniotic fluid (the fluid surrounding the unborn baby) enters the bloodstream. This could affect arteries throughout the body, including the lungs.

AFE is a life threatening complication that may lead to cardiac arrest, shock, and death.

Researchers have identified many different risk factors for PE. Since blood clots and DVT are the most common causes of PE, experts note that the risk factors for PE are generally the same as those for DVT.

Sometimes, however, a PE may have no identifiable cause, which is known as unprovoked PE.

Risk factors for PE may include:

If you’re living with an underlying health condition that may increase your risk of a PE, it’s important to carefully follow your management plan.

Otherwise, some lifestyle changes could help you reduce the risk of blood clots and PE. According to Asthma and Lung UK, these include:

If you’re going to embark on a long journey, such as by flight or car, consider the following tips to reduce the risk of blood clots and PE:

  • wearing compression stockings
  • wearing loose clothing
  • bending, stretching, and moving your legs and toes regularly
  • walking, when possible
  • drinking plenty of water

A healthcare professional can provide you with further tips on reducing your risk of blood clots and PE, especially if you have just had surgery.

The main cause of pulmonary embolism is deep vein thrombosis (DVT) in the legs. This is a blood clot that develops in one of the body’s deep veins.

Some research suggests that acute and chronic stress may be risk factors for pulmonary embolism. However, the researchers note that stress alone is unlikely to provoke a blood clot or pulmonary embolism on its own.

The most common risk factor for pulmonary embolism is DVT. Other common risk factors include long periods of immobility, being pregnant, and having surgery.

A PE occurs when a foreign substance blocks one of the pulmonary arteries. It’s usually caused by a DVT, but it may also be caused by fat, tumor cells, air, or amniotic fluid.

You could help manage your risk of PE by reducing the risk of developing blood clots. This may include exercising regularly, avoiding sitting for long periods, managing any underlying conditions, and staying hydrated.

If you’ve just had surgery or are recovering from a DVT or PE, it’s important to speak with a doctor. They can help develop a management plan to prevent any future PEs.