Pulmonary embolism (PE) is a type of venous thromboembolism (VTE) that results in blood clots in the lungs. It most often occurs when a blood clot develops elsewhere in the body, such as the legs, and then travels to the arteries of the lungs, causing a blockage.

While anyone may develop PE, this serious condition has multiple risk factors. Class 3 obesity is one such risk factor.

Previously known as “morbid obesity,” class 3 obesity, or severe obesity, describes having a body mass index (BMI) of 40 or higher. Doctors also used the term to describe class 2 obesity (BMI between 35 and 39.9) if you also had obesity-related health problems.

Class 3 obesity may present certain challenges in PE diagnosis, treatment, and outlook. Here’s the important information you need to know about PE and class 3 obesity that you can also discuss with a doctor or healthcare professional for the best possible outcome.

Obesity is just one known risk factor for the development of PE.

First, it’s important to understand obesity itself. While obesity is typically classified based on BMI, with higher numbers usually associated with health problems, this condition is much more complex than simply carrying excess body weight.

One risk factor for obesity is a lack of movement, which can cause your body to store excess fat. Reduced movement may also be a risk factor for PE. It often occurs during long periods of rest, such as bed rest after surgery, a long flight, or during a severe illness.

Still, research supports obesity as an independent risk factor for developing PE. According to one study that analyzed 299,010 people with obesity, researchers found that 0.9 percent had PE. This was more than double the rate in the general population.

Not only may VTE develop from reduced mobility, but obesity may also cause venous stasis and inflammation. These could then contribute to blood clots that may lead to PE.

Another possible risk factor is bariatric surgery, which doctors may use to treat obesity. Experts estimate that 1 percent of people may develop blood clots in the legs following weight loss surgery, with a small chance of these evolving into PE.

Only about half of all people with PE show symptoms, which is one of the main challenges in diagnosing this condition.

Other factors associated with class 3 obesity can also increase diagnostic difficulties. A 2018 review points to a lack of accommodations during crucial imaging tests. This includes tables and scanners that are too small.

Also, it may be more difficult to see blood clots on imaging tests in individuals with class 3 obesity, which can further delay important diagnosis and treatment of PE.

Adjusting the sizes of scanners and tables, and using contrasting dyes, are among some of the solutions to make imaging tests more accurate and useful.

PE is typically treated with blood thinners (anticoagulants) to help lower the risk of blood clots enlarging or multiplying. If doctors consider a blood clot to be life threatening, they may prescribe clot dissolvers (thrombolytics).

However, some of the medications used in treating PE may pose some risks for individuals with class 3 obesity.

According to a 2019 study, having class 3 obesity may increase your risk of bleeding when taking anticoagulants. It may also reduce how effective the medication is. Researchers don’t yet fully understand the reasons for this.

Recent treatments for obesity, such as bariatric surgery, could also influence the effectiveness of anticoagulant medications for PE. A 2020 case study suggests that bariatric surgery may affect overall drug distribution and clearance throughout the body.

There’s also research to support that certain PE treatments may work better in obesity than others. One such study suggests that apixaban may be a better treatment than warfarin for individuals with class 3 obesity. In the study, apixaban showed a lower risk of side effects and VTE recurrence.

PE, with or without obesity, may be life threatening. This is especially true if the clot is large or if there are multiple clots. Other complications associated with PE include permanent lung damage and low blood oxygen, which can damage other organs throughout the body.

But the outlook for people with both PE and class 3 obesity isn’t clear-cut. Some studies have identified an “obesity paradox” in which people with class 1 and 2 obesity may have a lower in-hospital mortality rate after acute PE. Other studies have found that outcomes for people with obesity are no different than for people without.

Researchers don’t yet know the exact outcomes for people with PE and class 3 obesity. However, they have established that obesity remains an acquired risk factor for VTE, which means you can prevent and treat it.

As such, it’s important to discuss with a doctor how treating obesity may also help prevent the development of future PEs. Treating obesity is highly complex and tailored to each individual and may include a combination of the following:

  • dietary changes
  • increased physical activity
  • medications to support dietary changes
  • weight loss surgery

Obesity is among the many risk factors for PE, with class 3 obesity presenting the highest risk of all such classes. Class 3 obesity can also present challenges in diagnosing and treating PE.

While not everyone experiences symptoms from PE, it’s important to see a doctor if you develop possible symptoms, such as chest pain, shortness of breath, and coughing that’s accompanied by blood.

If you have other risk factors for VTE, such as recent surgery, or family history, it’s important to talk with a doctor about ways you can lower the chances of developing PE.