November 30, 2015
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Pulmonary Embolism
(Blood Clot in the Lung)

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Pulmonary embolism facts

  • Pulmonary embolism (PE) describes the blockage of a pulmonary artery or one of its branches by a blood clot or foreign material.
  • Risk factors for the blood clot (thrombus) that travels to the lung (pulmonary embolism) include prolonged immobilization, medications, including birth control pills, smoking, genetic predisposition, an increased number of red blood cells (polycythemia), cancer, pregnancy, surgery, or damage to blood vessel walls.
  • Symptoms of pulmonary embolism include:
  • If not treated promptly, pulmonary embolism may lead to sudden death.
  • The diagnosis of pulmonary embolism may be difficult to make, and initially may be missed. Diagnostic strategies need to be individualized to each patient and situation.
  • Anticoagulation medication is the treatment for pulmonary embolism, and the patient may be required to continue treatment for a minimum of 3 to 6 months.
  • Prevention is the best treatment for pulmonary embolism, which can be accomplished by minimizing the risk factors for deep vein thrombosis (DVT).

What is a pulmonary embolism?

The lungs are a pair of organs in the chest that are primarily responsible for the uptake of oxygen and removal of carbon dioxide from the blood. The lung is composed of clusters of small air sacs (alveoli) divided by thin, elastic walls (membranes). Capillaries, the tiniest of blood vessels, run within these membranes between the alveoli and allow blood and air to come very near to each other without actually touching. The distance between the air in the lungs and the blood in the capillaries is very small, and this allows molecules of oxygen and carbon dioxide to transfer across the membranes.

The exchange of the air between the lungs and blood are through the arterial and venous system. Arteries and veins both carry and move blood throughout the body, but the process for each is very different.

  • Arteries carry blood from the heart to the body.
  • Veins return blood from the body to the heart.
  • Red blood cells contain hemoglobin, a molecule that facilitates transport of oxygen and carbon dioxide within the bloodstream.
  • Oxygen-carrying blood travels from the left side of the heart to all the tissues of the body. The oxygen attached to a red blood cell is extracted by the tissue, and carbon dioxide (a waste product) is picked up by the now empty red blood cell.
  • The blood, now without oxygen molecules and with higher levels of carbon dioxide, is returned via the veins to the right side of the heart.
  • The blood is then pumped out of the right side of the heart to the lungs, where the carbon dioxide is removed and oxygen, from the air that we breathe, is added to the blood.
  • Now the blood, high in oxygen and low in carbon dioxide, is returned to the left side of the heart where the process starts all over again.
  • The blood travels in a circle and is therefore referred to as circulation.
  • Oxygen is carried within the red blood cell by a molecule known as hemoglobin. When this combination of oxygen and hemoglobin occurs, the oxygen-carrying blood turns brighter red. This blood oxygen saturation can be measured, either by sampling the blood from an artery or by a noninvasive device called an oximeter that can be placed on a finger or earlobe.
  • Oxygen saturation in a healthy individual approaches 100% at sea level.

If a blood clot (thrombus) forms in the one of the body's veins (deep vein thrombosis or DVT), it has the potential to break off and enter the circulatory system and travel (or embolize). It then becomes lodged in one of the branches of the pulmonary artery in the lung.

A pulmonary embolus clogs the artery that provides blood supply to part of the lung. The embolus not only prevents the exchange of oxygen and carbon dioxide, but it also decreases blood supply to the lung tissue itself, potentially causing lung tissue to die (infarct).

A pulmonary embolus is one of the life-threatening causes of chest pain and should always be considered when a patient presents to a healthcare provider with complaints of chest pain and shortness of breath.

There are special types of pulmonary embolus that are not due to blood clots, but instead are due to other body materials. These are rare occurrences and include:

The signs and symptoms of a pulmonary embolus are caused by blockage of part of the arterial tree of the lung, preventing the blood's ability to reach all parts of the lung tissue.

Picture of how red blood cells and platelets form a blood clot
Picture of how red blood cells and platelets form a blood clot
Medically Reviewed by a Doctor on 11/20/2015


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