In the last few years, there has been increasing interest in whether compression stockings (sometimes called 'flight socks') reduce the risk of DVT (blood clots in the legs) and swelling of the legs caused by circulatory problems in airline passengers who are on long flights (greater than four hours). People may not be aware they have a DVT because they do not have any symptoms and the clots do not cause any problems. The only way of knowing they are there is to use ultrasound or scan for them.

• Compression stockings worn by airline passengers: Nine trials

COMPRESSION STOCKINGS FOR PREVENTING DVT (DEEP VEIN THROMBOSIS) IN AIRLINE PASSENGERS

Compression stockings are worn throughout the flight and are similar to those known to be effective in patients lying in bed after an operation. By applying a gentle pressure, to the ankle in particular, compression stockings help blood to flow. Pressure combined with leg movement helps blood in superficial veins to move to the deep veins and back to the heart. The blood is then less likely to clot in the deep veins, which could be fatal if the clot moves to the lungs.

What the synthesised research says

Wearing compression stockings resulted in a very large reduction in symptomless DVT among airline passengers who were allocated to wear compression stockings compared to those allocated not to wear such stockings. People who wore stockings also had much less discomfort and swelling in their legs (oedema) than those who did not wear them.

How it was tested

These conclusions were based on nine trials, which studied over 2800 people about half of whom were randomly assigned to wearing stockings for a flight lasting at least seven hours while the other half did not. None of the passengers developed a DVT with symptoms (slowly developing leg pain, swelling and increased temperature) and no serious events (a blood clot in their lungs (pulmonary embolus) or dying) were reported. Passengers were carefully assessed after the flight to detect any problems with the circulation of blood in their legs, even if they had not noticed any problems themselves. There was a big difference in symptomless DVT between the two groups, equivalent to a reduction in the risk from a few tens per thousand passengers to two or three per thousand.

Side effects and general limitations

Not all the trials reported on possible problems with wearing stockings but in those that did, the researchers said that the stockings were well tolerated, without any problems.

The review could not assess the effect of wearing stockings on death, pulmonary embolus or symptomatic DVT because no such events occurred in these trials. Randomized trials to assess these outcomes would need to include a very large number of people.

Source

Clarke M, Hopewell S, Juszczak E, Eisinga A, Kjeldstrøm M. Compression stockings for preventing deep vein thrombosis in airline passengers. Cochrane Database of Systematic Reviews 2006, Issue 2. Art. No.: CD004002. DOI: 10.1002/14651858.CD004002.pub2.