Alternate Names : Lung Embolus
An embolus is any material that travels through the bloodstream and then gets stuck in a blood vessel. When an embolus occurs in the veins that lead to the lungs, it is called a pulmonary embolus.
What is going on in the body?
A pulmonary embolus can occur for many different reasons. The embolus travels through the bloodstream until it reaches a blood vessel to the lungs that is too narrow. The embolus then gets stuck in the blood vessel and keeps the blood from flowing beyond it. A pulmonary embolus may be tiny and never noticed, or it may be large enough to cause death.
What are the causes and risks of the condition?
A pulmonary embolus may be caused by:
air bubbles, which may occur in scuba divers who return to the surface too quickly or during medical procedures
the amniotic fluid that surrounds a baby in the womb. This sometimes happens in pregnant women around the time of delivery.
a deep venous thrombosis, which is a blood clot in a vein in the legs or pelvis. These blood clots break off from the wall of the vein and travel to the lungs and are the most common cause of pulmonary embolus.
fat globules, which usually come from broken bones such as a hip fracture
foreign material in the veins, which sometimes occurs in people who abuse intravenous drugs
a piece of tumor, which may occur in some cases of cancer that metastasizes, or spreads through the body
Since deep venous thrombosis (DVT) is the most common cause of pulmonary embolus, factors that increase the risk of DVT are also risk factors for pulmonary embolus. Risk factors that increase an individual's risk of developing DVT include:
increased thickness of the blood. This can occur for many reasons, including an inherited tendency to form blood clots.
injury or trauma
pregnancy, especially around the time of delivery
a prolonged period of inactivity, such as long-term bed rest or sitting at a desk for many hours
surgery, especially in the pelvis or abdomen
the use of estrogen medications. These include oral contraceptives and hormone replacement therapy.
Recently, there have been conflicting research reports about the role of long airplane flights in deep venous thrombosis. One study of people with DVT found no significant travel patterns in these individuals. The results were true whether they traveled by car, plane, bus, or train.
A second study, however, showed a relationship between airline travel and an increase in the blood's tendency to form clots. The researchers attributed the increased risk of clot formation to the low pressure and reduced oxygen on the planes. The clotting was also increased by the dehydration and inactivity on long flights.
A third study looked at individuals hospitalized with DVT. These people were four times more likely to have gone on a long trip recently than those treated at the hospital for other conditions. Because of findings like this, deep venous thrombosis is often referred to as "economy class syndrome."