Pulmonary embolism is the sudden blockage of a major blood vessel (artery) in the lung, usually by a blood clot. In most cases, the clots are small and are not deadly, but they can damage the lung. But if the clot is large and stops blood flow to the lung, it can be deadly. Quick treatment could save your life or reduce the risk of future problems.

The most common symptoms are:

  • Sudden shortness of breath.
  • Sharp chest pain that is worse when you cough or take a deep breath.
  • A cough that brings up pink, foamy mucus.

Pulmonary embolism can also cause more general symptoms. For example, you may feel anxious or on edge, sweat a lot, feel lightheaded or faint, or have a fast heart rate or palpitations.

If you have symptoms like these, you need to see a doctor right away, especially if they are sudden and severe.

In most cases, pulmonary embolism is caused by a blood clot in the leg that breaks loose and travels to the lungs. A blood clot in a vein close to the skin is not likely to cause problems. But having blood clots in deep veins (deep vein thrombosis) can lead to pulmonary embolism. More than 300,000 people each year have deep vein thrombosis or a pulmonary embolism.

Other things can block an artery, such as tumors, air bubbles, amniotic fluid, or fat that is released into the blood vessels when a bone is broken. But these are rare.

Anything that makes you more likely to form blood clots increases your risk of pulmonary embolism. Some people are born with blood that clots too quickly. Other things that can increase your risk include:

  • Being inactive for long periods. This can happen when you have to stay in bed after surgery or a serious illness, or when you sit for a long time on a flight or car trip.
  • Recent surgery that involved the legs, hips, belly, or brain.
  • Some diseases, such as cancer, heart failure, stroke, or a severe infection.
  • Pregnancy and childbirth (especially if you had a cesarean section).
  • Taking birth control pills or hormone therapy.
  • Smoking.

You are also at higher risk for blood clots if you are an older adult (especially older than 70) or extremely overweight (obese).

It may be hard to diagnose pulmonary embolism, because the symptoms are like those of many other problems, such as a heart attack, a panic attack, or pneumonia. A doctor will start by doing a physical exam and asking questions about your past health and your symptoms. This helps the doctor decide if you are at high risk for pulmonary embolism.

Based on your risk, you might have tests to look for blood clots or rule out other causes of your symptoms. Common tests include blood tests, , CT scan, electrocardiogram (EKG, ECG), ultrasound, and MRI.

Other symptoms of pulmonary embolism may include:

Shortness of breath that may occur suddenly.

  • Sudden, sharp chest pain that may become worse with deep breathing or coughing.
  • Rapid heart rate.
  • Rapid breathing.
  • Sweating.
  • Anxiety.
  • Coughing up blood or pink, foamy mucus.
  • Fainting.
  • Heart palpitations.
  • Signs of shock.

Pulmonary embolism may be hard to diagnose because its symptoms may occur with or are similar to other conditions, such as a heart attack, asthma, a panic attack, or pneumonia. Also, some people with pulmonary embolism don't have symptoms.