Disease: Pulmonary Embolism
(Blood Clot in the Lung)

    Pulmonary embolism facts

    • Pulmonary embolism (PE) is the blockage of a pulmonary artery or one of its branches by a blood-borne blood clot or foreign material.
    • Causes of pulmonary embolism include prolonged immobilization, medications, 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:
      • chest pain,
      • shortness of breath, and
      • a cough that produces bloody sputum
    • If not treated promptly, pulmonary embolism may lead to 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 medication is the treatment 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 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.
    • 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 added to the blood from the air we breathe into 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 thus 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.
    • 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) through the heart and become 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:

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

    The signs and symptoms 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

    Source: http://www.rxlist.com

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