When I was in residency training, I was surprised one day to learn that one of my teachers, a young, healthy pediatrician, had been hospitalized after his vacation to California. It turned out he had developed a blood clot in his leg during a flight, and a portion of the clot traveled through his veins to the lungs, producing serious breathing problems.
My teacher, who had experienced what is known as a pulmonary embolus, thankfully made a full recovery.
He was fortunate.
The U.S. Centers for Disease Control and Prevention estimates that more than 100,000 people die from a pulmonary embolus each year, though fewer than half of these are recorded as the recognized cause of death.
Venous thromboembolism, which is a general term applied to this condition, often results from the formation of a blood clot in the deep veins of the leg. The clot may partially or completely block circulation in the veins and may produce symptoms of swelling and pain in the affected leg. This can be accompanied by redness, tenderness or increased warmth over the skin.
This is referred to as deep venous thrombosis, and most people know it as DVT. The principal danger of DVT is the risk that the clot, or a portion of it, may dislodge from the vein and travel through the circulation to the lungs, which may pose an immediate threat to life.
Symptoms of pulmonary embolus may include the sudden onset of chest pain and shortness of breath, similar to a heart attack. Less specific symptoms may include dizziness, fainting or anxiety. A very large pulmonary embolus may produce sudden death.
There are many risk factors for venous thromboembolism. Nearly 1 in 150 Americans suffer from blood disorders that increase the risk for blood clots such as sickle-cell trait or hemochromatosis.
Other risk factors include obesity, cancer, congestive heart failure or a recent major surgery. The risk increases with age. Pregnancy or the use of estrogen-containing contraceptives also increases the risk among women.
The risk of blood-clot formation related to travel is an interesting case. This is because of prolonged immobility. Studies have shown that the type of travel, whether by car, bus, train or plane, does not matter.
However, duration of immobility – such as remaining seated on a flight in excess of four hours, influences risk. It should be noted that the overall risk of a travel-related blood clot is small – on average of 1 in 4,600 flights, for example. However, risk increases by almost 20 percent for each additional two hours of travel time.
Moving leg muscles promotes better venous circulation. According to recommendations from the American College of Chest Physicians, travelers should remain well-hydrated, avoid constrictive clothing around the waist and legs, and regularly exercise the calf muscles of each leg during long-duration travel.
So when the captain turns off the seat-belt sign, consider yourself free to move about the cabin.
Dr. Matthew A. Clark is a board-certified physician in internal medicine and pediatrics practicing at the Ute Mountain Health Center in Towaoc.