Deep venous thromboses are blood clots that form in the deep veins of the body, particularly those of the lower extremities. If a piece of one of these blood clots breaks off, it can travel through the body’s circulatory pathways and reach the lungs, causing a pulmonary embolism. A pulmonary embolism can be fatal, as it can completely cut off the blood supply to the lungs. According to the National Heart, Lung, and Blood Institute, one of the risk factors for the development of deep venous thromboses is sluggish or slow blood flow, which can occur when someone is sitting and not moving their legs for prolonged periods of time, for example during long flights. There are several strategies you can follow to prevent the formation of blood clots during long flights, one of which is the use of compression or support stockings.
Risk Factors
There are several factors that increase the possibility of developing blood clots during long flights. According to the Centers for Disease Control and Prevention, these include obesity; recent surgery to the chest or abdomen; major bone surgery; use of oral contraceptives or hormone replacement therapy; pregnancy; being older than 40; and having a condition that makes the blood clot easier than normal. A 2007 study by the World Health Organization called the Global Hazards of Travel, or WRIGHT, Project, found that, for people flying after their first blood clot, air travel that lasts longer than four hours doubled their chances of developing another thrombosis.
Symptoms
The symptoms of a blood clot in the legs include swelling and tenderness, particularly of the calves; increased warmth and redness of the skin overlying the area of the clot; pain with movement of the affected extremity; and a knotting, painful sensation. If you develop a pulmonary embolus, symptoms can range from sudden shortness of breath, chest pain and dizziness, to sudden cardiac arrest and death.
Compression Stockings
Studies suggest that compression leg stockings decrease the chances of developing blood clots, including pulmonary embolisms, in people on long-distance flights. According to a Cochrane Reviews study published in 2006, compression stockings work by applying gentle pressure to the lower legs, especially around the ankle area, to improve blood flow. In general, leg movement promotes circulation of blood through the veins in the lower extremity. During long periods of immobility, the blood can pool within the veins, increasing the possibility of clotting. Compression stockings provide pressure that, when combined with leg movement, increases the circulation of blood, decreasing the chances of deep venous thrombosis. These stockings also decrease leg swelling and discomfort.
Prevention
Apart from compression stockings, there are other things a person on a long flight can do to decrease the risk of deep venous thrombosis. The CDC recommends drinking plenty of non-alcoholic beverages fluids, and doing leg exercises while sitting to keep the legs moving. The American College of Chest Physicians recommends that travelers in flights longer than eight hours should avoid constrictive clothing around the legs, maintain adequate hydration throughout the flight, and contract the calf muscles frequently. For those travelers with risk factors for deep venous thromboses, compression stockings that provide pressure around the ankle, or a single injected dose of low-molecular-weight heparin, an anticoagulant that prevents the formation of clots, are recommended.
References
- Cochrane Reviews; Compression Stockings for Preventing Deep Vein Thrombosis in Airline Passengers; Clarke MJ, Hopewell S, Juszczak E, Eisinga A, Kjeldstrøm M.; 2006
- Centers for Disease Control and Prevention: Deep Vein Thrombosis & Pulmonary Embolism
- National Heart, Lung, and Blood Institute: What Is Deep Vein Thrombosis?
