Pulmonary embolism

Medical Specialties: Emergency medicine, Internal medicine, Pulmonology

Clinical Definition

A pulmonary embolism is a blockage in the lungs’ main artery. It is usually caused by detached fragments from a thrombus in another part of the body. The thrombus moves through the bloodstream and lodges in the pulmonary artery, creating an occlusion. Due to restricted blood flow to the lungs, hypoxia and pulmonary hypertension can develop. Most often, a pulmonary embolism occurs as a result of a deep vein thrombosis. In rare instances, embolization of fat, air or amniotic fluid can also cause a pulmonary embolism. 

In Our Own Words

A pulmonary embolism is a blockage of an artery in the lungs, usually caused by a blood clot. It can occur if the blood clot, which was in another part of the body, moves to the lungs. The blood clot can become stuck in one or more arteries in the lung and block blood flow to the lung.


Decreased blood flow can lead to reduced oxygen levels in the body and increased blood pressure in the pulmonary arteries. Depending on the size of the blood clot and extent of the blockage, a pulmonary embolism can be life threatening.


Usually when a pulmonary embolism develops, it is from a blood clot in a large vein in the leg or arm. Air, fat and amniotic fluid can also travel to the lungs and block the arteries, though these are much less common than a blood clot.

Relevant Conditions
  • Clotting disorders
  • Pregnancy
  • Malignancy
  • Prolonged immobilization
Side Effects
  • Chest pain
  • Shortness of breath
  • Increased heart rate
Share this article
  • Society for Vascular Surgery. “Pulmonary Embolism.” http://www.vascularweb.org. Accessed September 2013.
  • Cleveland Clinic. “Pulmonary Embolism.” http://my.clevelandclinic.org. Accessed September 2013.
  • Kacmarek R., PhD RRT FAARC, Stroller J., MD MS, Heuer, A. Egan’s Fundamentals of Respiratory Care, 10th Edition. Mosby 2012. Accessed September 2013.
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