What Is a Pulmonary Embolism?

Medically Reviewed by James Beckerman, MD, FACC on December 06, 2022
4 min read

Your blood goes from your heart to your lungs through your pulmonary artery. In the lungs, the blood is supplied with oxygen, and then it goes back to the heart, which pumps the oxygen-rich blood to the rest of your body.

When a blood clot gets caught in one of the arteries that go from the heart to the lungs, it’s called a pulmonary embolism (PE). The clot blocks the normal flow of blood.

This blockage can cause serious problems, like damage to your lungs and low oxygen levels in your blood. The lack of oxygen can harm other organs in your body, too. If the clot is big or the artery is clogged by many smaller clots, a pulmonary embolism can be deadly.

Pulmonary embolisms usually travel to the lungs from a deep vein in the legs. Doctors call this deep vein thrombosis (DVT). These clots develop when the blood can’t flow freely through the legs because your body is still for a long time, say during a long flight or drive. It might also happen if you’re on bed rest after surgery or illness.

The risk factors are the same as those for DVT. Doctors refer to these as Virchow’s triad. They are:

  • Not moving for a long time or having changes in normal blood flow. This often happens if you’ve been in the hospital or on bed rest for a long period of time. It could also happen during a long flight or vehicle ride.
  • Blood that’s more likely to clot. Doctors call this hypercoagulability. It could be caused by medications, like birth control pills. Smoking, cancer, recent surgery, or pregnancy can also put you at risk.
  • Damage to a blood vessel wall. Injury to your lower leg can lead to this.

In rare cases, an artery in the lung can be blocked by something other than a clot, like an air bubble or part of a tumor. If you break a big bone, fat from the bone marrow can sometimes come through the blood and cause blockage.

The best way to prevent a PE is to try to stop blood clots from forming deep in your veins. This can be challenging if you’ve been on bed rest after a surgery or illness, or if you just took a long flight.

If you’re at risk, here are a few things that may help lower your chances of getting these dangerous blood clots:

Blood thinners

Doctors call these anticoagulants. They keep your blood from forming clots. Your doctor may prescribe them to you while you’re in the hospital for surgery. They might also suggest that you keep taking them for some time after you go home.

Your doctor might also recommend blood thinners if you’ve been hospitalized after a stroke or heart attack, or if you have complications from cancer.

Compression stockings

These are long socks that squeeze your legs. The extra pressure helps blood move through your veins and leg muscles. Your doctor may recommend that you wear them for a while after surgery.


Get out of bed and walk when you’re getting over a long stay in the hospital or an illness that’s kept you in bed for too long. It’ll keep the blood in your legs flowing so it doesn’t have a chance to pool.

Stretching during trips

If you’re on a long flight, try to walk around every few hours. If you can’t stand up, flex your ankles by pulling your toes toward you.

Here’s another stretch you can try to do while seated:

  1. Pull your leg up toward your chest with one hand.
  2. Hold the bottom of that leg with the other hand.
  3. Keep this pose for 15 seconds, and then try it with the other leg.
  4. Do this up to 10 times per hour.

If you’re driving a long distance, stop every hour and stretch your legs.

Also, be sure to drink extra fluids to help you stay hydrated.

Lifestyle changes

Other steps you can take include:

In life-threatening cases of pulmonary embolism, your doctor may decide to give you drugs called thrombolytics to break up the clot. It may even need to be taken out or broken up with surgery, though this is rare.