Pulmonary Embolism

What Is pulmonary embolism?

A pulmonary embolism (PULL-mun-ary EM-bo-lizm), or pulmonary embolism, is a sudden blockage in a lung artery, usually due to a blood clot that traveled to the lung from a vein in the leg. A clot that forms in one part of the body and travels in the bloodstream to another part of the body is called an embolus.

Pulmonary embolism is a serious condition that can cause:

  • Permanent damage to part of your lung from lack of blood flow to lung tissue

  • Low oxygen levels in your blood

  • Damage to other organs in your body from not getting enough oxygen

If the blood clot is large, or if there are many clots, pulmonary embolism can cause death.

Overview of pulmonary embolism

In most cases, pulmonary embolism is a complication of a condition called deep vein thrombosis (DVT). In DVT, blood clots form in the deep veins of the body-most often in the legs. These clots can break free, travel through the bloodstream to the lungs, and block an artery.

This is unlike clots in the veins close the skin's surface, which remain in place and do not cause pulmonary embolism.


At least 100,000 cases of pulmonary embolism occur each year in the United States. Pulmonary embolism is the third most common cause of death in hospitalized patients. If left untreated, about 30 percent of patients with pulmonary embolism will die. Most of those who die do so within the first few hours of the event.

What causes pulmonary embolism?

Major Causes

In 9 out of 10 cases, pulmonary embolism (PE) begins as a blood clot in the deep veins of the leg (a condition known as deep vein thrombosis). The clot breaks free from the vein and travels through the bloodstream to the lungs, where it can block an artery.

Clots in the leg can form when blood flow is restricted and slows down. This can happen when you don't move around for long periods of time, such as:

  • After some types of surgeries

  • During a long trip in a car or on an airplane

  • If you must stay in bed for an extended time

Veins damaged from surgery or injured in other ways are more prone to blood clots.

Other causes

Rarely, an air bubble, part of a tumor, or other tissue travels to the lungs and causes pulmonary embolism. Also, when a large bone in the body (such as the thigh bone) breaks, fat from the marrow inside the bone can travel through the blood to the lungs and cause pulmonary embolism.

Pulmonary embolism disorder picture

Pulmonary Embolism Symptoms

What are the signs and symptoms of pulmonary embolism?

A pulmonary embolus may present with the sudden onset of chest pain and shortness of breath. The pain is classically sharp and worsens when taking a deep breath, often called pleuritic pain or pleurisy. There may be cough that produces bloody sputum.

The patient may have stable vital signs (blood pressure, heart rate, respiratory rate, and oxygen saturation) but frequently presents with an elevated heart rate. If the blood clot is large enough, it can block blood from leaving the right side of the heart thus preventing blood from entering the lungs. There is then no blood entering the left side of the heart to pump to the rest of the body. This can result in circulatory collapse (shock) and death.

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