Definition

Pulmonary embolism (PE) is a condition in which the arteries of the lungs are blocked by a detached blood clot. This blood clot comes from another body part, such as an arm or leg, which detaches and follows the airflow to the lungs. Blockage of blood vessels caused by a blood clot can be life-threatening.

Causes

A pulmonary embolism is caused by a blood clot that prevents blood flow to the lungs. This blood clot most commonly originates from the legs due to a disease called deep vein thrombosis (DVT). In most cases, the blockage does not occur in a single vein, so the severity of symptoms varies according to how many veins are blocked. If a specific blood vessel becomes blocked, the lung tissue blooded by it will die, resulting in a lung infarction. Pulmonary infarction causes further disruption of the oxygen exchange process in the lungs, affecting the overall oxygen level.

Apart from being caused by blood clots, pulmonary embolism can also be caused by:

• Fat cells from broken bones or bone marrow
• Part of a tumor
• Air bubbles that enter the blood vessels

Risk factor

Factors that increase the risk of pulmonary embolism include:

• Having certain medical conditions such as heart disease (heart failure), cancer (especially cancer of the brain, ovaries, pancreas, colon or large intestine, stomach, and cancer that has spread or metastasized), blood clotting disorders, and having severe COVID-19 symptoms.
• Family history of pulmonary embolism or blood clotting problems.
• Prolonged bed rest. After a heart attack, leg fracture, major surgery, or severe injury, doctors frequently advise patients to limit their movement and stay in bed. This restriction of movement can cause blood to clot easily. When the lower extremities (legs and feet) are in a horizontal position for a long time, the return (venous) blood flow may slow down and accumulate below, resulting in a blood clot.
• Long-distance travel. Sitting for long periods on airplanes or in cars can cause the return (venous) blood flow to slow and clot.
• Smoking. Tobacco consumption causes blood to clot easily, so people who smoke have a higher risk of pulmonary embolism.
• Using hormonal birth control. Extra estrogen from outside the body, such as pills or hormonal therapy, can raise blood clotting factors, especially if you smoke or are overweight.

Symptoms

Symptoms of a pulmonary embolism vary depending on how much of the lung is affected, the size of the blood clot, and whether or not you have a history of heart or lung disease. Common signs and symptoms are:

• Shortness of breath. This symptom generally appears suddenly and worsens with activity
• Chest pain. The chest pain is sharp and is felt when you take a deep breath. The pain may also be felt when you cough or look down
• Cough. You may cough up blood or blood spots

Other signs and symptoms that may arise are:

• Rapid and irregular heartbeat
• Feeling dizzy or floating
• Profuse sweating
• Fever
• Pain in the legs, with swelling. Swelling can be felt in both legs, especially in the calves
• Pale and cold skin

Diagnosis

Pulmonary embolism is difficult to diagnose, particularly in people who have had previous lung or heart disease. The doctor will ask about your current symptoms, perform a physical examination, and conduct supporting tests such as:

• Blood test. The doctor will examine a d-dimer substance, which can rise when blood clotting. High d-dimer is not only caused by pulmonary embolism, but it can also provide clues for the doctor.
• Chest X-ray. This examination cannot directly diagnose pulmonary embolism; however, it can exclude other diseases with similar symptoms.
• Ultrasound. Ultrasound is a non-invasive test that examines blood flow and detects blood clots. If the doctor does not discover a blood clot in a specific location, pulmonary embolism can be ruled out. However, if a clot is present, treatment will be initiated immediately.

Management

The treatment of pulmonary embolism aims to prevent the blood clot from getting bigger and new blood clots from forming. Prompt and appropriate treatment is essential to prevent death and further complications.

Medications 

• Blood thinners (anticoagulants) are drugs that aim to prevent blood clots from forming. Examples include heparin or warfarin. Because these drugs can cause bleeding, they need to be used under close supervision.
• Blood clot breakers (thrombolytics). Although blood clots can break down independently, thrombolytics must be administered in some conditions to speed up the process.

Measures that may be taken include

• Retrieving the blood clot. If the clot is large enough to be life-threatening, your doctor may recommend removing the clot using a catheter.
• Venous filter. In addition to retrieving the blood clot, the catheter can also insert a filter to prevent the formation of blood clots in the future. This procedure is performed on people who should not take blood thinners.

Complications

Pulmonary embolism can be life-threatening. Approximately one-third of people who are diagnosed and treated late die. If the condition can be detected sooner, the chances of recovery are higher.

Pulmonary embolism can also cause pulmonary hypertension, which is abnormally high blood pressure in the lungs and right heart. When the pulmonary artery is blocked, the heart has to work harder to push blood through the blood vessels, raising blood pressure and weakening the heart muscle.

In some cases, the embolism may block little by little over a long period, resulting in chronic pulmonary hypertension.

Prevention

One way to prevent pulmonary embolism is to prevent blood clots, especially in the limbs. As a result, hospitals implement protocols to prevent blood clots in patients who are hospitalized for a long time, specifically:

• Anticoagulants. These medications are often given to people who are about to undergo surgery, especially those with certain risk factors (cancer, heart attack, or stroke)
• Compression stockings. Compression stockings are specifically designed to help blood flow back to the veins in the leg area. They are a safe, simple, and inexpensive way to prevent blood clots during and after major surgery
• Leg elevation. Keeping the legs elevated, especially at night, can help prevent blood clots.  Elevate your legs by about 10-15 cm with a pillow or stack of books
• Physical activity. Once you can move, you can prevent pulmonary embolism by remaining physically active to the best of your ability. Physical activity can help reduce stagnant or pooled blood in the legs, lowering the risk of blood clot formation

If you are going on a long trip, you can do some of the following things to prevent blood clots:

• Drink enough water to prevent dehydration. Avoid alcohol which can cause fluids to be flushed out of the body
• Change positions from time to time. You can walk around the airplane cabin every 1-2 hours of flight. If you are using a car, you can stop for some time to stretch your leg muscles
• Move your legs every 15-30 minutes
• Use stockings, especially if you have risk factors for blood clots

When to see a doctor?

Pulmonary embolism can be life-threatening, so you need to seek immediate medical attention if you experience shortness of breath, chest pain, or coughing up blood. These symptoms do not always indicate a pulmonary embolism, but they can be life-threatening and require prompt and appropriate treatment.

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