Pulmonary Embolism
(Blood Clot in the Lung)

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Pulmonary embolism facts

  • Pulmonary embolism is a diagnosis that should be considered in patients with chest pain and/or shortness of breath, and is one of the causes of sudden death.
  • The diagnosis of pulmonary embolism may be difficult to make, and is often missed. Diagnostic strategies need to be individualized to each patient and situation.
  • Anticoagulation is the treatment of choice for pulmonary embolism and the patient may be required to continue treatment for 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 exchange of oxygen and carbon dioxide between the air we breathe and 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 near each other. The distance between the air in the lungs and the blood in the capillaries is very small, and 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.
  • The heart is a two-sided pump.
  • Oxygen-carrying blood travels from the left side of the heart to all the tissues of the body. The oxygen is extracted by the tissue, and carbon dioxide (a waste product) is delivered back into the blood.
  • The blood, now deoxygenated 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 is returned to the blood from the air we breathe in, which fills the lungs.
  • 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.

The oxygen is carried in the red blood cell by a molecule known as hemoglobin. When this combination of oxygen and hemoglobin occurs, the 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. This is often referred to as an “ET finger”, since the apparatus when attached to the finger glows red.

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) through the heart and become lodged in the one of the branches of the pulmonary artery of 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:

  • fat emboli from a broken femur,
  • an amniotic fluid embolus in pregnancy, and
  • in some cases, tumor tissue from cancer.

The signs and symptoms are the same as that of a blood clot, and is caused by blockage of part of the arterial tree of the lung, and prevents 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 6/30/2014

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Pulmonary Embolism

Serena Williams Battles a Pulmonary Embolism and a Hematoma

Whenever a young and healthy athlete gets sick, it always gets the attention of the press. The news is even more dramatic when the condition can be life-threatening, as in the case of Serena Williams, who reportedly developed a pulmonary embolism in late February 2011. While it is possible to recover fully from a pulmonary embolism, it is indeed a serious condition and requires serious medications. In addition, Ms. Williams also reportedly required treatment for a hematoma, a collection of clotted blood that forms outside of a blood vessel.

A pulmonary embolism (PE) happens when a blood clot (thrombus) forms in one of the body's large veins (known as deep vein thrombosis or DVT), breaks off, and travels (embolizes) in the circulatory system back to the heart and out into the arteries that carry blood to the lungs to load up oxygen. There the clot in the lungs (embolus) then clogs the artery that provides blood supply to part of the lung, preventing the normal exchange of oxygen and carbon dioxide. It also reduces the blood supply to the lung tissue itself. Lung tissue can die (infarct) if circulation is impaired.