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.
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.
A pulmonary embolus may be caused by:
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: cancer
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."