Table.
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 |
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