Thromboembolic disease and flying (fitness to fly)

• thromboembolic disease
  • acute thromboembolic disease e.g. DVT/PE is an absolute contraindication to flying - also see notes below (1,2,3,4,5)
    
    
  • patients with a history of pulmonary embolism or DVT should be considered for full oral anticoagulation

The risk factors for thrombosis are well known and are listed below:

• Thrombophilia enhancing clotting activity
• Recent major surgery
• Trauma or surgery of the lower limbs
• Family history of deep vein thrombosis
• Age over 40 years
• The oral contraceptive pill

Prophylactic measures should be undertaken according to the degree of risk (4,5)

Simple, effective measures are to move about the aircraft cabin and to carry out the lower limb exercises shown in airline videos and in-flight magazines.

Any specialised prophylaxis should be targeted at those at the highest risk and include:

• properly fitted anti-embolism stockings giving graduated compression to the limb (if no contraindications),
• subcutaneous low molecular weight heparin, which is highly effective and has a low risk of bleeding and in extremely high risk cases oral anticoagulation.

It is important to emphasise that the risk of side effects from the use of aspirin outweigh any potential anti-thrombotic effect and its use is not recommended (4)

In a patient with a history of a DVT undertaking a long-haul flight, and not already on long-term oral anticoagulant therapy, then another possible management strategy might be (2):

1. a patient with a history of a previous DVT should wear blow-knee compression stockings
2. if the patient has only had one episode of DVT and there are no other risk factors then no other measures are indicated
3. if the patient has other conditions that increase the risk of DVT e.g. inherited or acquired thrombophilia state, gross obesity, a plaster of Paris of the lower limb, or has very long legs in a small seat space, then some would recommend a prophylactic injection of low molecular weight heparin before leaving the airport. This is in addition to use of compression stockings.

Notes:

• it has been stated that if there is a history of a DVT/PE and the patient is stable and anticoagulated then the patient should not fly for 10 to 14 days (3)
  
  
• these are only guidelines and each airline has its own regulations and medical standards
  
  
• Deep venous thrombosis is not intrinsically dangerous but the complications of pulmonary embolism can be life threatening (4)
  • has been shown that DVT can occur in many other forms of travel, as described by Homans in 1954. The World Health Organisation Research into Global Hazards of Travel (Wright) Project recently reported and the key determinant for deep venous thrombosis is immobilisation and the risk of thrombosis is increased by travel of greater than 4 hours
    • therefore "travellers' thrombosis" is the most appropriate term to use, rather than "economy class syndrome"
    • no evidence that the cabin environment activates the coagulation system of normal individuals. The absolute risk, as shown in the Wright Study, was one in 4656 flights of more than 4 hours duration.

Reference:

1. 'Medical guidelines for air travel', Aviation, Space and Environmental Medicine, October 1996: 67: 10- 11.
2. Pulse (2002);62 (28): 64.
3. Doctor (April 2005). Ready Reckoner - fitness to fly.
4. Civil Aviation Authority. Fitness to Fly (Accessed 11/12/19)
5. International Air Transport Association. Medical Manual 11th Edition (2018).