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Pulmonary embolism

A pulmonary embolism is a blockage in one of the blood vessels in your lungs. It can be fatal if the obstruction is very large and blocks the main blood supply to the lungs.

  • About pulmonary embolism
  • Symptoms
  • Causes
  • Diagnosis
  • Treatment
  • Prevention
  • Further information
  • Sources
  • Related topics

About pulmonary embolism

A pulmonary embolism happens when a blood clot or piece of a blood clot gets stuck in one of the blood vessels in your lungs. The blood clot forms somewhere else in your body and is carried to your lungs in the bloodstream.

In 70 to 90 percent of people who get a pulmonary embolism, the blood clot comes from one of the legs. The blood clot usually forms in one of the deep veins that run through the centre of your leg. A blood clot in one of these veins is called deep vein thrombosis or DVT for short.


Symptoms of pulmonary embolism include:

  • chest pain
  • breathlessness
  • coughing up blood
  • fainting

The symptoms you have and how severe they are will depend on how big your pulmonary embolism is. Some people who have a small embolism don't have any symptoms at all. However, a large embolism can cause more severe symptoms, shock and sudden collapse.

Although not necessarily a result of pulmonary embolism, if you have any of these symptoms, you should see your GP. If your symptoms are severe or if someone has collapsed, you should call for emergency help.


Most pulmonary embolisms are a result of DVT in the legs. A blood clot can develop in the legs if you are inactive for a long period of time. When you move your legs around, the muscles in your legs contract, pumping blood through the veins. When your legs are inactive, the blood flow can slow down and blood can start to pool in the veins. This can eventually lead to a blood clot.

You are at greater risk of pulmonary embolism if you:

  • have recently had major surgery, particularly on your hip or knee
  • are pregnant or have recently given birth
  • have cancer
  • are confined to bed with a serious illness
  • have a previous history of DVT or pulmonary embolism
  • have an inherited condition called thrombophilia, which means you are more likely to get blood clots
  • have a heart disease or high blood pressure
  • take the contraceptive pill or hormone replacement therapy
  • are travelling for a long distance
  • are obese

Heavy smoking (more than 25 cigarettes per day) may increase the risk of pulmonary embolism even further in women.


About half of people who have a pulmonary embolism get it when they are in hospital or long-term care for another problem. You may also be admitted to hospital as an emergency if you are having trouble breathing or have collapsed.

If you visit your GP with minor symptoms, he or she will ask about your symptoms and examine you. Your GP may also ask you about your medical history. You may have tests, such as an electrocardiogram (ECG) to rule out other conditions that could be causing your symptoms. An ECG measures the electrical activity in your heart to see how well it is working.

Your GP will try to work out the likelihood of you having a pulmonary embolism by asking you a series of questions. He or she may also examine your legs for signs of a DVT. If your doctor thinks you could have a pulmonary embolism, he or she will refer you to a hospital for further tests and treatment.

Tests commonly used to diagnose pulmonary embolism include the following.

  • Blood tests, including a test for a substance called D-dimer - if the test result is negative this can rule out DVT and pulmonary embolism.
  • Chest X-ray, although this is often normal.
  • Computed tomography pulmonary angiography (CTPA) - this test uses X-rays to make a three-dimensional image of the lungs. A dye is injected into your veins so that they will show up on the X-ray image. This is the main imaging test that doctors use to diagnose pulmonary embolism.
  • Isotope lung scanning - this test can see how much blood is getting into your lungs. It's sometimes done before a CTPA.


Once you get to hospital, you will be given oxygen to help you breathe if your doctor thinks you need it. You may also be given painkillers.


  • If your doctor strongly suspects that your symptoms are caused by a pulmonary embolism, you will be given injections of a drug called heparin before your diagnosis has even been confirmed. Heparin is a type of drug called an anticoagulant. Anticoagulants are used to prevent blood clots from forming, or to prevent existing blood clots from getting any worse.
  • If it's confirmed that you have an embolism, you will be prescribed ongoing treatment with an anticoagulant that can be taken by mouth, such as warfarin. You will usually have to take the drug for at least six months. But this will depend on what has caused your embolism and whether you are likely to get another one.
  • If you have a large pulmonary embolism, you may also be given a drug called a thrombolytic (eg alteplase) to try and dissolve your blood clot. This will be given as an injection into a vein.

Other treatments

Occasionally, doctors may suggest putting a filter into the main vein carrying blood to your heart (called the inferior vena cava). This will usually only happen if you are at high risk of getting another pulmonary embolism or you can't take anticoagulant medicine. The filter stops any clots that have formed in your legs from travelling up to your heart and lodging in your lungs.

Special considerations: pregnancy

Your risk of getting a blood clot increases about ten-fold when you are pregnant. Having pre-eclampsia and having a caesarean increases this risk even more.

When you have your first antenatal visit, your doctor or midwife should ask you if you have any personal or family history of DVT of pulmonary embolism. If you do, you may be offered screening for a blood clotting disorder (thrombophilia).

If your doctor thinks you are at particular risk of getting a blood clot you may be given heparin injections during your pregnancy and for six weeks after you have given birth. You may also be given elastic stockings to wear. You might be at high risk if you had DVT or a pulmonary embolism in a previous pregnancy, or while taking the contraceptive pill.


If you are in hospital for surgery or because of illness, your doctor will suggest some leg exercises you can do, to ensure you keep your legs moving. You will be encouraged to drink plenty of fluids (or may have fluids via a drip if you are unable to drink).

If you are having major surgery, you may be given injections of heparin before your surgery to reduce your risk of getting a DVT or pulmonary embolism. You may also be given elastic compression stockings to wear or a device called an intermittent compression pump to keep the blood flowing through your legs.

  • Compression stockings (also called TED or thrombo-embolic deterrent stockings) are usually worn to help maintain circulation and reduce the risk of blood clots forming in the veins of your legs. They come in different sizes and will be checked by nursing staff every day to make sure that they're the correct size and fit for you. You might be asked to wear them after you have had surgery.
  • Intermittent compression pumps help to dissolve blood clots by compressing the calf and/or thigh muscles of your leg. They are usually used straight before or during surgery.

Further information

The Circulation Foundation


  • Venous thrombosis and air travel. The Circulation Foundation. www.circulationfoundation.org.uk, accessed 6 March 2008
  • Prophylaxis of venous thromboembolism. Scottish Intercollegiate Guidelines Network (SIGN), October 2002. www.sign.ac.uk
  • Robinson GV. Pulmonary embolism in hospital practice. BMJ 2006; 332:156-160
  • Kumar P, Clark M. Pulmonary embolism. In: Clinical Medicine. 6th ed. Elsevier, 2005: 844-846
  • British Thoracic Society. British Thoracic Society guidelines for the management of suspected acute pulmonary embolism. Thorax 2003; 58:470-484
  • Goldhaber SZ, Grodstein F, Stampfer MJ, et al. A prospective study of risk factors for pulmonary embolism in women. JAMA 1997; 277(8):642-645
  • British National Formulary (BNF), BMJ Publishing Group, 2007. 55:121-125

Related topics

  • Compression stockings
  • Deep vein thrombosis