Army Aviation

Pulmonary Embolism

Ask the Flight Surgeon / By LTC Theresa M. Long, M.D., F.S., M.P.H.: 

Q: I am a 37-year-old CH-47 pilot. I have done multiple overseas deployment. Until my most recent redeployment, I was in excellent health. I was a marathon runner, with no chronic medical problems other than seasonal allergies. The only medications I take are birth control pills and seasonal allergy medications as needed. A few days after reaching state-side I started having some shortness of breath and was subsequently diagnosed with a pulmonary embolism. What is a pulmonary embolism and how is it going to affect my flying career for both the Army and civilian sector?

FS: With the exercise community gaining traction and speed nowadays the supplement market has exploded in popularity and diversity of products. With many of these products being over the counter (OTC) you may wonder why so many of these products are not flight compatible. The answer, while being multifactorial, is quite simple. At the end of the day we want to mitigate risk in the flight environment. If our aircrew are taking supplements that are not regulated by the U.S. Food and Drug Administration (FDA), that have varying side effects for different people, may have adverse reactions with current medication profile, and may be taken to overcome some underlying medical issues (joint pain, weakness, etc.), unwanted risk enters the flight environment. This is why we have to strictly limit what aircrew can and can’t take. For a brief synopsis there are three classes of “herbal and dietary supplements” in the Army Aeromedical Policy Letters (APLs).   

Pulmonary embolism (PE) is a medical condition where a blood clot from a larger vein travel to the lungs and blocks the blood flow to the lungs. With decreased blood flow to the lungs, less blood will be oxygenated, which leads to shortness of breath.

There are a number of risk factors that predispose people to form blot clots in their legs or other body parts with larger veins (deep vein thrombosis, DVT).)  Avoidable risk factors include smoking, obesity, supplemental estrogen (as seen in birth control pills, patches, rings, injections, and implants). Pregnancy also increases a risk of developing a blood clot. Prolonged immobility, such as bed rest after surgery or during prolonged air or road trips can decrease the flow of venous blood in the lower legs and contribute to the formation of blood clots. Certain cancers such as brain, ovarian, pancreas, colon, stomach, lung and kidney and some cancer treatment increase the risk of blood clot formation. Traumatic injury or surgery also increase an individual’s risk of developing a DVT or PE. Some individuals are genetically predisposed to form blood clots because they have deficiencies or abnormalities in the proteins involved in the blood clotting cascade, such as Leiden factor V deficiency.

If a DVT or PE is small and caught early, it can be treated relatively easily with oral medication in an outpatient setting. However, PE can be life-threatening – one third of undiagnosed PEs cause death. When a blood clot cuts off the circulation to an area of the lung for a prolonged period, that portion of the lung will infarct or die, resulting in permanent damage.

Unfortunately, long redeployment flight and oral birth control most likely increased your risk of developing a blood clot. As you go through the treatment for PE, doctors will confirm that you don’t have any complications or other factors that predispose you for a blood clot. All of these factors will be taken into consideration for safety of flight risk assessment in consideration of requesting and granting a waiver for a single non-recurrent thrombolytic event.

Treatment Options

Many treatment options are available after an individual has a DVT or PE, both nonsurgical and surgical. Most PE are treated with an anticoagulant, also called a blood thinner. Anticoagulants will prevent the existing clot from enlarging while dissolving it, and prevent additional clots from forming. Thrombolytic (clot dissolvers) could be given within hours to dissolve a large, life-threatening clot, but it could cause severe bleeding. Hence, thrombolytic medications are reserved only for cases that meet certain criteria.

Clot removal can be a lifesaving surgical intervention, necessary for very large clots. In cases where a patient is unable to take anticoagulant therapy or has had recurrent blood clots while taking anticoagulants, a filter can be surgically implanted in the body’s main vein (inferior vena cava) to keep clots from going from your legs to your lungs.


Risk mitigation is the best strategy for prevention of DVTs and PEs. Some preventive measures include drinking plenty of fluids and avoid alcohol consumption to prevent dehydration. Moving legs, flexing ankles every 15-30 minutes, getting up and moving around and or wearing compression stockings will increase the blood flow, preventing a clot. These strategies are especially important during a prolonged air or ground travel that you experienced with your redeployment travels.


Per Army Aeromedical Policy Letters, a waiver for DVT or PE will be considered on a case-by-case basis for acute, nonrecurring conditions after anticoagulation therapy has been stopped. When history and laboratory assessment are normal, with no predisposing factors, such as an underlying cancer or blood clotting disorder identified, a waiver might be feasible. If the individuals develop complications such as pulmonary hypertension, requires on-going anticoagulation medications beyond aspirin, or surgical intervention these conditions are also disqualifying and would require a separate waiver.

For your civilian career, the FAA will need documentation in accordance with 14 CFR § 67.401. The FAA regulations allow for pilots to be granted a Special Issuance certificate to fly while taking medications used in the treatment and prevention of pulmonary embolisms and deep vein thromboses, provided that no other complications exist.
I hope this information was helpful.

Questions for the Flight Surgeon?
If you have a question, email it to This email address is being protected from spambots. You need JavaScript enabled to view it.; we will try to address it in the future. See your unit flight surgeon for your personal health issues.

The views and opinions offered are those of the author and researchers and should not be construed as an official Department of the Army position unless otherwise stated.

Above The Best!

pulmonary embolism

Image: Pulmonary Embolism by Nick Youngson CC BY-SA 3.0

LTC (Dr) Theresa M. Long is a flight surgeon at the School of Army Aviation Medicine, Fort Rucker, Alabama.