Table.

Risk of venous thromboembolism prophylaxis in air travellers

	Definition	Recommendations	Quality of evidence*
Low risk	Flight time less than 8 h or distance less than 5000 km	Avoid constrictive clothing around waist and lower extremities; avoid dehydration; move about cabin several times or do calf-stretching exercises	Grade 1C
Moderate risk	Flight time more than 8 h or distance more than 5000 km, and: obesity, large varicose veins, pregnancy, hormone-replacement therapy, tobacco use or oral contraceptives, or relative immobility	Low-risk measures and: wear properly fitted below-knee compression stockings providing 15–30 mm Hg of pressure at the ankle; aisle seating	Grade 1C and grade 2B
High risk	Flight time more than 8 h or distance more than 5000 km, and: history of previous venous thromboembolism; hypercoagulable state (eg, factor V Leiden); major surgery 6 weeks before air travel (including hip or knee arthroplasty); known malignancy	Moderate-risk measures and: low-molecular-weight heparin injected before departure in individuals who are not on warfarin	Grade 1C and grade 2B

Data are based on references 38, 40, 41, 51, 52, 53, 57.

^*Grade 1C is a strong recommendation, but existing evidence is of low quality and benefits clearly outweigh risk or burden. Grade 2B is a weak recommendation derived from moderate quality evidence, and benefits of therapy are balanced with risk and burden.⁵²