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Pulmonary Embolus

Pulmonary Embolus

Alternate Names

  • lung embolus
  • Pulmonary arteries and veins


An embolus can be any material, most often a blood clot, that travels through the bloodstream and then gets stuck in a blood vessel. When an embolus occurs in the veins that lead to the lungs, it is called a pulmonary embolus.

What is going on in the body?

A pulmonary embolus can occur for many different reasons. The embolus travels through the bloodstream until it reaches a blood vessel to the lungs that is too narrow. The embolus then gets stuck in the blood vessel and keeps the blood from flowing beyond it. A pulmonary embolus may be tiny and never noticed, or it may be large enough to cause death.


What are the causes and risks of the condition?

A pulmonary embolus may be caused by:
  • air bubbles, which may occur in scuba divers who return to the surface too quickly or during medical procedures
  • the amniotic fluid that surrounds a baby in the womb. This sometimes happens in pregnant women around the time of delivery.
  • a deep venous thrombosis, which is a blood clot in a vein in the legs or pelvis. These blood clots break off from the wall of the vein and travel through the heart to the lungs and are the most common cause of pulmonary embolus.
  • fat globules, which usually come from broken bones such as a hip fracture
  • foreign material in the veins, which sometimes occurs in people who abuse intravenous drugs
  • a piece of tumor from a cancer that metastasizes, that is, spreads through the body
Since deep venous thrombosis (DVT) is the most common cause of pulmonary embolus, factors that increase the risk of DVT are thus risk factors for pulmonary embolus as well.
Risk factors that increase an individual's risk of developing DVT include:
  • cancer
  • an increased clotting tendency of the blood. This tendency can be inherited or can occur for other reasons.
  • injury or trauma
  • obesity
  • pregnancy, especially around the time of delivery
  • a prolonged period of inactivity, such as long-term bed rest or sitting at a desk for many hours
  • surgery, especially in the pelvis or abdomen
  • the use of estrogen medications. These include oral contraceptives and hormone replacement therapy.
Although research findings are not entirely consistent, travel experiences, be they by air, car, or otherwise, in which individuals must sit for long periods of time are believed to be risk factors for DVT. Researchers have attributed increased risk of clot formation to a combination of the low pressure and reduced oxygen on airplanes, coupled with the inactivity and also the dehydration that tends to occur in air travelers.


What can be done to prevent the condition?

Since deep venous thromboses are the major cause of a pulmonary embolus. Measures to prevent DVT will go a long way toward lowering a person's risk of pulmonary embolus. Avoiding long periods of inactivity can reduce the risk of DVT. This is especially important for people who have a history of DVT. For example, it's good to start to walk soon after surgery or an injury.
Although the research is still inconclusive about the effects of airplane trips, people can lower their risk of DVT by:
  • avoiding alcohol or sleeping pills before or during the flight
  • avoiding long periods of sleep during the flight
  • avoiding tight stockings
  • doing exercises in their seat, such as ankle rolls and toe pointing
  • drinking plenty of fluids to avoid dehydration
  • getting up and moving about periodically
  • limiting carry-on luggage so they have plenty of leg room
  • obtaining a seat with as much leg room as possible
  • talking with their healthcare professionals about taking aspirin for its blood-thinning properties
  • walking around the concourse before and between flights
  • wearing loose, comfortable clothing
Blood-thinning medications can help prevent DVT. These include heparin, enoxaparin, and warfarin. Compression stockings can also be used to improve the flow of blood back up to the heart. Scuba divers should follow proper procedure and not return to the surface too quickly. Intravenous drug abuse should be avoided.


How is the condition diagnosed?

The diagnosis of pulmonary embolus starts with a medical history and physical examination. Diagnostic tests may include:
  • arterial blood gases, which measure oxygen and carbon dioxide levels in the blood
  • an electrocardiogram (ECG), which measures the electrical activity of the heart
  • a pulmonary perfusion scan, which shows the blood flow to all areas of the lungs
  • a pulmonary ventilation scan, which looks at the distribution of air in the lungs

Long Term Effects

What are the long-term effects of the condition?

A pulmonary embolus can cause permanent lung damage and death. Congestive heart failure, a condition in which a weakened heart cannot pump enough blood through the body, can also occur

Other Risks

What are the risks to others?

A pulmonary embolus is not contagious and poses no risk to others.


What are the treatments for the condition?

Oxygen and pain medications are given as needed. If the pulmonary embolus is caused by a DVT, bed rest and elevating the leg can help reduce the swelling and pain. People with a deep venous thrombosis are usually given an injection of a blood-thinning medication.
The injection may be given either intravenously or under the skin. These medications, such as heparin and enoxaparin, help prevent further growth of the blood clot. After a few days of blood-thinning medications by injection, the person can be switched to pills. Warfarin is the most common blood-thinning pill.
In some people, blood-thinning medications cannot be used for various reasons. For example, a person may have a high risk of bleeding. In these cases, a surgical procedure can be done. This involves inserting a filter in one of the major veins of the body that leads to the heart. This filter catches any clots that break off, thus keeping them from reaching the lungs.

Side Effects

What are the side effects of the treatments?

Heparin or warfarin can cause abnormal bleeding from any of a number of sources. In unusual cases, the bleeding can be fatal. Warfarin interferes with many other medications. Surgery can be complicated by bleeding, infection, or an allergic reaction to the anesthetic.

After Treatment

What happens after treatment for the condition?

A person's condition after treatment will vary, depending on the cause of the pulmonary embolus. For example, a woman who recovers from a fluid embolus during pregnancy is free to return to normal activities. No further treatment may be needed.
If the cause of an embolus is a blood clot, a person usually needs to take blood thinners, such as warfarin, for several months. A person who has had more than one pulmonary embolus may need to take blood thinners for life. If blood thinners cannot be tolerated for some reason, a person may need to undergo a special procedure. In this procedure, a filtering device is inserted in a major vein leading back to the heart. The filter stops an embolus from getting into the lungs.


How is the condition monitored?

Individuals on blood-thinning medications will have periodic blood tests to monitor the clotting capacity of their blood. Any new or worsening symptoms should be reported to the healthcare professional.


Harrison's Principles of Internal Medicine, 1998, Fauci et al.

Cecil Textbook of Medicine, 1996, Bennett et al.

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