What Is pulmonary embolism?
A pulmonary embolism (PULL-mun-ary EM-bo-lizm), or pulmonary embolism, is a sudden blockage
in a lung artery, usually due to a blood clot that traveled to the lung from a
vein in the leg. A clot that forms in one part of the body and travels in the
bloodstream to another part of the body is called an embolus.
Pulmonary embolism is a serious condition that can cause:
- Permanent damage to part of your lung from lack of blood flow to lung
- Low oxygen levels in your blood
- Damage to other organs in your body from not getting enough oxygen
If the blood clot is large, or if there are many clots, pulmonary embolism can cause death.
Overview of pulmonary embolism
In most cases, pulmonary embolism is a complication of a condition called
thrombosis (DVT). In DVT, blood clots form in the deep veins of the body-most
often in the legs. These clots can break free, travel through the bloodstream to
the lungs, and block an artery.
This is unlike clots in the veins close the skin's surface, which remain in
place and do not cause pulmonary embolism.
At least 100,000 cases of pulmonary embolism occur each year in the United States.
Pulmonary embolism is the
third most common cause of death in hospitalized patients. If left untreated,
about 30 percent of patients with pulmonary embolism will die. Most of those who die do so
within the first few hours of the event.
What causes pulmonary embolism?
In 9 out of 10 cases, pulmonary embolism (PE) begins as a blood clot in the
deep veins of the leg (a condition known as
deep vein thrombosis). The clot
breaks free from the vein and travels through the bloodstream to the lungs,
where it can block an artery.
Clots in the leg can form when blood flow is restricted and slows down. This
can happen when you don't move around for long periods of time, such as:
- After some types of surgeries
- During a long trip in a car or on an airplane
- If you must stay in bed for an extended time
Veins damaged from surgery or injured in other ways are more prone to blood
Rarely, an air bubble, part of a tumor, or other tissue travels to the lungs
and causes pulmonary embolism. Also, when a large bone in the body (such as the thigh bone)
breaks, fat from the marrow inside the bone can travel through the blood to the
lungs and cause pulmonary embolism.