It involves formation of blood clots in veins in the legs after sitting for long periods. The clots may travel through blood vessels to lodge in the lungs. Almost 900,000 Americans develop DVTs annually, and 70,000 die.
Nobody knows how many result from extended periods of sitting during travel.
Estimates range from 5 percent to 60 percent of the total. ECS got its name years ago after doctors found a link between blood clots and sitting in the cramped economy class seating on long-haul airline flights. Muscle contractions in the legs during walking squeeze blood vessels and helps to move blood back to the heart. Clots may form in the stagnant blood. Doctors in some cities, for instance, see an increase in DVT almost every spring.