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Deep Vein Thrombosis

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63775.  Wed Apr 05, 2006 5:22 am Reply with quote

Although it is linked to 'economy class syndrome' in the popular imagination, the factors which can predispose one towards DVT are many and various; air travel is just one, and not a particularly important one as far as I can make out:

The following risk factors for DVT have been identified in many different epidemiologic studies:

    Immobilization longer than 3 days
    Pregnancy and the postpartum period
    Major surgery in previous 4 weeks
    Long plane or car trips (>4 h) in previous 4 weeks

    Previous DVT
    Acute myocardial infarction (AMI)
    Congestive heart failure (CHF)
    Nephrotic syndrome
    Ulcerative colitis
    Multiple trauma
    CNS/spinal cord injury
    Lower extremity fractures

    Systemic lupus erythematosus (SLE) and the lupus anticoagulant
    Behçet syndrome
    Polycythemia rubra vera
    Inherited disorders of coagulation/fibrinolysis
    Antithrombin III deficiency
    Protein C deficiency
    Protein S deficiency
    Factor V Leyden
    Dysfibrinogenemias and disorders of plasminogen activation
    IV drug abuse
    Oral contraceptives
    Heparin induced thrombocytopenia

70950.  Mon May 22, 2006 4:10 am Reply with quote

William Toff, at the University of Leicester, studied 70 volunteers whom he placed in a pressurized (low oxygen) chamber at ground level. He found no evidence that poor air quality causes DVT.

"This cabin pressure represents the worst case scenario to which passengers might be exposed," says Toff, adding that most long-haul jetliners at cruising level typically maintain cabin pressure at an altitude equivalent of 1,524 to 2,134 metres.

Blood was drawn from the volunteers before and after each of the two sessions to test four markers of the early signs of blood clotting. The researchers found no significant difference between the two groups, they report in the Journal of the American Medical Association.

Toff says he thinks the prime cause of DVT in long-distance travel by air, rail or car is simply "prolonged, seated immobility".


Suzanne Cannegieter at the Leiden University Medical Center in the Netherlands has shown that people who spent eight hours flying showed more signs of coagulation than the same people confined for eight hours in cinema seats.

Cannegieter points out that some previous studies have suggested an effect of low oxygen levels on blood clotting. She says this is still the most likely candidate to explain problems during air travel.

Seems like it's still up in the air.


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