Stephan Moll, MD writes… Can the person with a newly diagnosed DVT or PE safely fly, or should he/she wait for a few weeks before flying? It appears o.k. to fly early. There is no evidence that flying early after the diagnosis of DVT or PE leads to an increased risk of recurrent clots or breaking off of clots from a DVT to form a PE, as long as the patient is on adequate blood thinner treatment.
Airline travel and Blood Clots
a) The person NOT on blood thinners
Airline travel is an established (mild) risk factor for DVT and PE in the patient who is NOT on blood thinners [ref 1,2]; the longer the travel, the higher the risk for clots . Typically, multiple risk factors come together –overweight, hormone therapy (e.g. contraceptives), recent surgery, trauma, or hospital stay, cancer, genetic or acquired clotting disorders, and the immobility from the travel itself. It has also been suggested that the decreased air pressure in the airplane cabin might lead to activation of the clotting system and an increased risk for DVT or PE, particularly in persons with one or more of the above underlying risk factors [ref 4]. However, neither have published data on this issue been consistent, nor is it clear whether such changes are really relevant for the traveller.
b) The patient with VTE who is on blood thinners
- Is there an increased risk for recurrent DVT or PE or clot breaking off from a DVT? It is not known whether the risk for recurrent clot or the risk for a DVT to break off to cause a PE is increased with airline travel in the patient who is on blood thinners. Any potential activation of the clotting system by the decreased cabin pressure while flying is very likely counteracted by the fact that the patient is on a blood thinner. Thus, an increased failure rate of blood thinners (i.e. progression of DVT or PE; increased risk of DVT leading to PE) is not likely.
- Is there worsened leg swelling in the patient with DVT? The patient with acute DVT and leg swelling may experience somewhat more swelling during or after the flight – not because of worsening DVT, but because of increased fluid retention in the legs from the decreased air pressure in the cabin. Many healthy people experience that, too. Also, the distances to walk and the prolonged standing in the airport may lead to increased leg swelling. However, this is not expected to lead to worsening DVT or a new DVT.
- Is there worsened shortness of breath in the patient with PE? The patient who has had a large PE or has other underlying lung disease (COPD, etc.) may have some worsening of shortness of breath during flying – not because of new PE, but because the airplane cabin contains slightly less oxygen than the air at sea level.
In general, I discuss with the patient who has a new DVT or PE that…
- it appears to be o.k. to fly immediately after the DVT or PE diagnosis, as long as the person is on full-dose blood thinners.
- airline travel is not expected to lead to an increased risk of new DVT or PE or breaking off of clots from a DVT.
- leg swelling in the person with DVT may temporarily worsen during and in the few days after airline travel due to the lower air pressure in the airline cabin.
- shortness of breath in the person with a fairly large PE may be somewhat worse during airline travel due to the mildly decreased oxygen content in the airline cabin.
- it may be worthwhile to delay a flight for at least a few days, to be sure that the patient is stable, no unexpected issues occur, and/or the patient has had time to adapt to this new, potentially life-modifying diagnosis and treatment.
As always, individualized medical decisions need to be made.
- Chandra D et al. Meta-analysis: Travel and risk for venous thromboembolism. Ann Intern Med 2009;151:180-190.
- Cannegieter SC. Travel-related thrombosis. Best Pract Res Clin Haematol. 2012 Sep;25(3):345-50.
- Schreijer AJ et al. Activation of coagulation system during air travel: a crossover study. Lancet 2006 Mar 11;367(9513):832-8.
- Schreijer AJ et al. Explanations for coagulation activation after air travel. J Thromb Haemost 2010 May;8(5):971-8.
I appreciate the discussions with Dr. Richard Moon, Medical Director, Center for Hyperbaric Medicine & Environmental Physiology, Duke University Medical Center, Dr. Claude Piantadosi, Interim Chief, Division of Pulmonary, Allergy and Critical Care Medicine, Duke University Medical Center, and Dr. Philip Blatt, Adjunct Professor of Internal Medicine and Hematology, Duke University Medical Center, Durham, NC.
Last updated: July 12th, 2017