By David Wright, Vice President, Medical Affairs at BTG International
Whenever your legs are below the heart blood must be actively pumped back to the heart or the blood tends to pool, becoming static and at higher than normal pressure which results in swelling. This high pressure is only overcome by getting your legs level with your heart or continuous exercise. This happens to everyone not just those with varicose veins.
The most demanding circumstance is during long-haul flight, anything over 4 hours is considered a risk. Of course it starts earlier with travel to the airport, standing in line, or sitting in the lounge, but once airborne your legs are particularly still. The swelling causes discomfort, pain and heaviness in the legs which contribute to the overall sensation of Jet lag.
In addition to this, the lack of motion in the blood increases the risk of a blood clot (thrombosis) forming, the vast majority of these go un-noticed but occasionally they may progress and cause obstruction which causes more swelling and pain in the days after the flight. If you have these symptoms that do not resolve, or get worse in the 7-10 days after a flight seek medical help urgently. Even more unlikely is for a thrombus to break free and travel to the lung causing pulmonary embolus, which can be fatal.
Although the risk is very small it is well worth wearing compression for the benefit they provide in improving the way your legs feel at the end of a long flight, car or bus journey.
The only realistic way to combat this sequence is to wear good fitting compression socks or stockings providing adequate compression force (no less than 20mmHg at the ankle), they only need be worn up to the knee.
They should be put on at the start of the day of the flight and worn continuously until the next time you go to bed. They should always be the correct size and the material should be smoothed and remain as a single layer. Bad-fitting compression garments may be worse than nothing, a significant minority are not well served by over the counter products.