Stephan Moll, MD writes… Can the patient with acute DVT or PE safely fly, or should he/she wait for a few weeks before embarking on airline travel? It appears safe to fly early: There is no evidence that flying early after the diagnosis of VTE leads to an increased risk of recurrent VTE or embolization from a DVT, as long as the patient is on adequate anticoagulation.
Airline travel and Thrombosis
a) The person NOT on anticoagulation
Airline travel is an established (mild) risk factor for DVT and PE in the patient who is NOT on anticoagulation [1,2]; the longer the travel, the higher the risk for thrombosis . 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 hypobaric atmosphere in the airplane cabin might lead to coagulation activation and an increased risk for VTE, particularly in persons with one or more of the above underlying risk factors for VTE [ref 4], but neither have data on this issue been consistent, nor is it clear whether such changes are clinically relevant.
b) The patient with VTE who is on anticoagulation
- Is there an increased risk for recurrent DVT or PE or embolization from a DVT? It is not known whether the risk for recurrent VTE or the risk for a DVT to embolize is increased with airline travel in the patient who is on anticoagulation for a previous VTE. Any potential coagulation activation by the hypobaric cabin environment is likely counteracted by the fact that the patient is on anticoagulation. Thus, an increased anticoagulation failure rate (i.e. progression of DVT or PE; increased risk of DVT leading to PE) is not likely. And while the reduction in ambient cabin pressure per se leads to a small reduction in a patient’s partial pressure of oxygen (PO2) and this may lead to mild vasodilatation and an increase in cardiac output, this is not likely to increase the risk of embolization from a DVT.
- Do patients with DVT develop increased leg swelling while flying? The patient with acute DVT (or postthrombotic syndrome) and leg swelling may experience somewhat more leg swelling during or after the flight – because of leg edema from an increase in capillary permeability in the hypobaric cabin environment, not because of DVT progression. Also, the distances to walk and the prolonged standing in the airport may lead to worsened leg edema. However, this is not expected to lead to progressive or recurrent DVT.
- Do patients with PE develop increased shortness of breath while flying? The patient who has a large PE or has other underlying hypoxic lung disease (COPD, etc.) may have some worsening of shortness of breath during flying – not because of new PE, but because the cabin’s environment is mildly hypoxic.
Rules by the International Air Transportation Association (IATA) limit the decrease in cabin pressure in commercial aircraft to an equivalent altitude of 8,000 ft (564 mmHg, 0.74 ATA), although most planes maintain their pressures at an equivalent altitude of around 5,000 ft (632 mmHg, 0.83 ATA). Thus, the predicted decrease in a patient’s arterial PO2 is small, and would be clinically significant only for people with pre-existing hypoxemia.
In general, I discuss with the patient who has an acute DVT or PE and wants to fly soon that…
- he/she can fly, even immediately after the VTE diagnosis, as long as he/she is on full-dose anticoagulation.
- that airline travel is not expected to lead to an increased risk of recurrent VTE or embolization from a DVT.
- leg swelling in the patient with DVT may temporarily worsen during and in the few days after airline travel due to the hypobaric pressure in the airline cabin.
- shortness of breath in the patient with a 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.
- 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