On our website, we have many calculators related to medicine and clinical research, but this one might be the most interesting and useful. So, what are pulmonary embolisms, what causes them, how dangerous are they, and how can this calculator determine whether you are at risk of one or not.

Answers to these and many more questions on this topic are in the post below.

Pulmonary Embolism – Definition

A pulmonary embolism is a condition in which one or multiple arteries that supply blood to your lungs get clogged up. It is a very dangerous condition, and in many cases, it is fatal, however, using the Wells score, you can prepare to fight it. To understand why you need to understand what blood does in your body.

As you might already know, blood is liquid tissue, which has two functions. The first one is to supply each and every single cell in your body with food and O2, with the other being to carry away waste and CO2. Because of this, there are two types of blood that flow in your body: oxygenated (arterial) and deoxygenated (venal).

So, arteries are essentially the blood vessels that feed your organs. All the major internal organs have major arteries that supply them with food and oxygen, and the lungs are no exception. The arteries that lead blood to the lungs are pulmonary arteries, hence the name “pulmonary embolism“. When one of them gets clogged up, the corresponding part of the lungs does not get the blood it needs to function, and as a result, will die off.

Pulmonary Embolism – Cause

As we said, an embolism occurs when an artery gets clogged up, thus not allowing a certain organ or tissue to receive everything it needs to survive. They can occur anywhere in the body, with an artery and any organ. The question remains: “What causes them?”, and the answer is “It depends.”. There are different types of embolisms, and they all have different causes.


Thromboembolism is caused by a blood clot. Blood clots naturally form on the walls of your blood vessels. In some cases, however, the bloodstream can tear the clot from the wall of the blood vessel, at which point it starts traveling with the blood. It will travel until it reaches a narrow part of the artery. Once it does, it will stop, blocking the vessel either completely or partially. Both of these are dangerous, however, as an organ that receives some blood, but not enough, is also going to lose some function.

Fat embolism

Fat embolism is caused by fat droplets that find their way into your bloodstream. It can get there if an oil-based solution is injected intravenously (into the vein). This should never be done, and every medical worker should be aware of that. It can also be caused by fat embolism syndrome, where fat emboli systematically manifest in a person’s bloodstream. Because fat is not soluble in water, which is a big part of blood, the fat droplet will act almost like a solid body in the artery. Again, once it reaches a narrower part of the artery, it will stop and act as a blockade, thus not allowing blood to get to the organ the artery supplies it to.

Air embolism

Air embolism is caused by air bubbles. So, air is not as harmless as it might seem, as just one bubble inside your bloodstream can be the cause of your death. Once again, the cause can be an improper intravenous injection. Right before injection, the syringe mustn’t have any air in it, as it could cause an air embolism. This is why you see medical workers turn the syringe upside down, and squeeze the air out. It can also be caused by decompression sickness (DCS), and a few others.

Septic embolism

Septic embolism is the consequence of sepsis, which is the presence of many bacteria inside a person’s bloodstream. Bacteria can enter the bloodstream via any openings in the cardiovascular system. This is why disinfection and sterilization are of utmost importance in medicine. Sepsis itself is very dangerous, even without the possibility of an embolism. The principle is the same as with the others. A clump of microorganisms blocks the blood vessel, not allowing blood to flow, thus causing an embolism.

Tissue embolism

Tissue embolism is very self-explanatory. A piece of tissue is torn and inserted into the bloodstream through an opening of a blood vessel. It is very rare but can happen with malignant tumors. Namely, malignant tumors spread to other organs by sending pieces of the tumorous tissue through blood or lymph. A piece of the tumorous tissue could block the blood vessel it is traveling through, thus causing an embolism.

Foreign body embolism

Foreign body embolism is also very self-explanatory, and even rarer than the previous one. It could happen with an open wound, with a small object gaining access to the bloodstream, in most cases a hair or a nail.

Amniotic fluid embolism

Amniotic fluid embolism is caused by amniotic fluid, which is the fluid that surrounds the fetus during pregnancy, as well as by fetal cells, hair, or any other debris that enters a mother’s bloodstream via the placenta.

Pulmonary Embolism – Symptoms

A PE has several symptoms, many of which are very general, but combined, they can set a clinical diagnosis for a PE. The most general ones are:

  • Sudden shortness of breath
  • Lightheadedness, dizziness and fainting
  • High heart rate (tachicardia)
  • Irregular heartbeat
  • Sweating

These are seen with many conditions, which is why they are not an instant giveaway of the condition. The more specific symptoms are:

  • Chest pain – usually located where the embolus is
  • A feeling of anxiety
  • Coughing up blood
  • Low blood pressure

Once enough of these symptoms are present, a clinical diagnosis for PE can be set.

The PE could also be caused by deep vein thrombosis (DVT), which has the following symptoms for the affected leg:

  • Pain
  • Swelling
  • Soreness
  • Tenderness
  • Redness

Pulmonary Embolism – Diagnosis

As I mentioned before, all the symptoms are common with many other conditions. Because of this, it is very difficult to set a clinical diagnosis for PE in patients. Along with a complete medical history and physical exam, tests that are useful for discovering the embolus are:

  • Chest x-rays – a diagnostic test used to assess the lungs and heart
  • Ventilation-perfusion scans – a diagnostic test which is used to evaluate blood flow within the lungs of a patient, using a small amount of a radioactive substance
  • Pulmonary angiogram – a diagnostic test in which a contrast is injected into a thin flexible tube inside the artery, allowing the blood vessels to show up on the x-ray
  • Computerized tomography (CT or CAT scan)
  • Magnetic resonance imaging (MRI)
  • Duplex ultrasound (US) – a diagnostic test used for assessing the blod floow and structe of blood vessels inside the legs
  • Various lab tests
  • Electrocardiogram (ECG)

Pulmonary Embolism – Treatment

The treatment consists of destroying the embolus. If the embolus is a blood clot, anticoagulants can be used.

Anticoagulants are essentially blood thinners, and their goal is to soften up the blood clot, so it turns back into liquid blood. Thrombolysis or fibrinolytic therapy is not used with all clinical patients. In fact, it is used only in life-threatening situations because it can lead to bleeding, which can be very dangerous.

The percutaneous thrombectomy is a procedure in which a long, thin, hollow tube, similar to a catheter is threaded through the blood vessel, with the help of an x-ray. The tube is then used to destroy the blood clot. For severe cases, where the embolus can’t be destroyed any other way, a pulmonary embolectomy is performed, which is a surgical procedure, where a surgeon takes the embolus out manually.

Wells Score – What is it?

Now that you know what a pulmonary embolus is, what causes it, and what it can do, we can move on to prevention.

The Wells score is a set of criteria that we use to establish the probability of a PE in a clinical patient. Doctors use it with patients whose history and examination suggest a high probability of an acute pulmonary embolism.

There are, of course, some similar ways to calculate the probability of a PE, such as the pulmonary embolism rule-out criteria, and the Geneva score.

Wells Score – Criteria

There are 7 criteria in the Wells score, and they all carry a different score. In the following text, we are going to carefully go over and explain each one.

Clinical signs and symptoms of deep vein thrombosis (DVT)

Deep vein thrombosis (DVT) is a condition that occurs when a blood clot is inside a deep vein. It usually happens in the lower extremities, although it is not uncommon for it to happen in the upper extremities and the neck.

Clinical patients with DVT have reported the following signs and symptoms of the disease:

  • Swelling in the affected leg, with rare cases including swelling in both legs
  • Pain that is similar to soreness or cramping; the pain usually starts in your calves, and spreads to the rest of your leg
  • Discoloration of the affected leg
  • Increased temperature of the affected leg

In the Wells criteria for a PE, it carries a score of 3.

The possibility of a different diagnosis being more likely

This one boils down to the rest of the symptoms. Essentially, if, after reviewing the patient’s symptoms, the health care provider evaluates that another disease is more plausible than a pulmonary embolism. So, a NO should be put for this one. If the pulmonary embolism is the most likely disease, or equally likely to another one, you should put YES.

In the Wells criteria for a PE, it carries a score of 3.


Tachycardia is the medical term for a heart rate that is higher than 100 beats per minute. It is not necessarily always bad, as your heart rate naturally increases during exercise or stress. The problem is when your resting heart rate is above 100 beats per minute. At that point, you should consider consulting a medical professional. If you don’t treat this, some tachycardia patients may have a higher probability of a heart attack, a stroke, or sudden cardiac death.

In the Wells criteria for a PE, it carries a score of 1.5.

Immobilization or surgery

If you have been immobilized for 3 or more days consecutively, you should put YES on this one. Similarly, if you have had surgery in the past 4 weeks, you should put a YES.

In the Wells criteria for a PE, it carries a score of 1.5.

Diagnosed with deep vein thrombosis or a pulmonary embolism in the past

This one is also very self-explanatory. If you had a diagnose of either DVT or a pulmonary embolism in the past, you should put a YES on this one.

In the Wells criteria for a PE, it carries a score of 1.5.


Hemoptysis is the medical term for coughing up blood, or blood-stained mucus, with the blood originating from your respiratory tract. It happens as a consequence of many respiratory diseases, most notably tuberculosis, lung cancer, and in this case, a pulmonary embolism.

In the Wells criteria for a PE, it carries a score of 1.


Malignancy is the medical term used to describe a disease that gets progressively worse. It is most often associated with cancer. So, if a malignant disease is present, the person is on medication for it, was on medication for it in the past 6 months, or is in palliative care, a YES should be put on this one.

In the Wells criteria for a PE, it carries a score of 1.

Wells Score – Interpretation

Once you have done the calculation, you can check the interpretation. The maximum possible score is 12.5, with split into three tiers.

0-1 is the low-risk tier. For this tier, the pulmonary embolism rule-out criteria (PERC) can be considered, as well as the D-dimer. A D-dimer is a protein fragment in the blood after a blood clot degradation. We use the D-dimer test to rule out the possibility of a serious blood clot.

2-6 is the moderate risk tier. For this tier, the D-dimer could be considered, although it is not recommended. As well as that, a CT pulmonary angiography should be done. A CT pulmonary angiography is a test for the state of the pulmonary arteries evaluation.

6-12.5 is the high-risk tier. The D-dimer test is not recommended, and a CT pulmonary angiography is a must.

Wells Score Calculator for Pulmonary Embolism – How to Use?

The Wells score calculator is pretty straightforward. Simply evaluate all the criteria then use the interpretation to get the final result. Of course, you should always consult your health care provider before making any decisions in terms of treatment.

Wells Score Calculator for Pulmonary Embolism – Example

As an example, let’s make up an imaginary clinical patient, assign him a state, and then go through the calculator.

Our patient is a 50-year-old female who has never been diagnosed with a pulmonary embolism or any kind of cancer. She does, however, have deep vein thrombosis, hemoptysis, and a resting heart rate of 120. As well as that, she didn’t have surgery in the past 4 weeks and hasn’t been immobilized in 5 years.

She also recently visited her doctor, who, after reviewing all the tests and examinations, concluded that a pulmonary embolism is the most likely condition.

If you’re curious, you should always measure your resting heart rate in the morning right as you wake up, as the results will be the most accurate at that point in time.

So let’s get calculating. Since she has deep vein thrombosis, the first criteria is a strong YES, as well as the second one. Her resting heart rate is 120, so for tachycardia, we are also going to put YES. She hasn’t been immobilized or had surgery in recent times, so that is a NO. For the 5th criteria, we will also put a NO, since she hasn’t been diagnosed with a pulmonary embolism in the past, and is, at this moment, suffering from deep vein thrombosis. For hemoptysis, we will also put a YES, and finally, a NO for malignancy.

After calculating, we can see, that she gets a score of 8.5, which falls into the high-risk tier.


How is the Wells score calculated?

The Wells score is calculated based on 7 pre-determined criteria that lead to an increased risk of a pulmonary embolism.

What is a 2 level Wells score?

The 2 level Wells score for a pulmonary embolism consists of the low-risk tier (0-4) and the high-risk (4-12.5) tier.

What is a pulmonary embolism?

A pulmonary embolism is a condition in which one or multiple arteries that supply blood to your lungs get clogged up.

How to prevent a pulmonary embolism?

To avoid a pulmonary embolism, a healthy lifestyle with a balanced diet and regular exercise are key. If you think you are at risk of a pulmonary embolism, you should consult your medical health care provider.

What is the survival rate of a pulmonary embolism?

When untreated, the mortality rate goes up to 30%, but when treated, the mortality rate is 8%. Acute attacks of pulmonary embolism can cause people to die suddenly 10% of the time.