JACKSON, Miss.—Kay Cashion’s first transatlantic flight taught her the folly of spending nine hours glued to a cramped airline seat.

“I had this awful swelling in my feet,” said the teacher at Northwest Rankin High School in Rankin County. “I had to unlace my shoes just to wear them and it took two days for the swelling to go down.”

Later, Cashion learned it could have been much worse. Being cooped up for long hours can cause blood clots to form in the deep veins of the leg, a condition called deep vein thrombosis. If a clot breaks loose and travels to an artery in the lungs, a life-threatening pulmonary embolism can occur.

“When I began to inquire about it, I heard horror stories about people who had actually died,” Cashion said.

One such victim is NBC correspondent David Bloom. Doctors now believe that the blood clots that killed Bloom may have formed during the time he spent confined in a Humvee while covering the war in Iraq.

Clots occur when blood flow is restricted and cramped accommodations contribute to the problem, explained Dr. James Williams, a physician at Methodist Rehabilitation Center in Jackson. “Some people call DVT the ‘economy class syndrome’ because the lack of leg room in the coach section keeps passengers immobilized,” he said.

Williams said travelers who are elderly, pregnant, smokers or overweight are at a greater risk of developing DVT. Other contributing factors include poor circulation, narrow or blocked veins related to injury, surgery or radiation therapy or a history of heart disease, heart attack, stroke or varicose veins. Birth control pills and hormone replacement therapy also raise the risk, as does prolonged bed rest or inactivity.

Williams said travelers should see a physician if they notice DVT symptoms such as warmth, redness, tenderness, pain or swelling in the affected area; a red, hard and tender cord just under the surface of the skin; and/or fever.

A pulmonary embolism is more serious and requires emergency medical attention. Symptoms include shortness of breath, chest discomfort (usually worse with a deep breath or coughing), a general sense of anxiety or nervousness and lightheadedness or blacking out, Williams said.

To prevent travel-related DVT, Williams recommends the following:

• Keep moving. Break up periods of sitting with activity. If you’re on a plane, take a stroll down the aisle once an hour. If you’re in a car, make frequent rest stops and walk around. If must stay seated, flex your legs by pumping your feet like you’re pushing on a gas pedal.
• Try support stockings. If you suffer from swollen legs, ankles or varicose veins, support stockings may be beneficial because they promote circulation.
• Drink lots of water. Avoid dehydration by consuming plenty of water and steering clear of alcohol.
• Take an aspirin. If your doctor approves, a single low-dose aspirin can be taken to thin the blood.

Cashion, who leads tours for the educational travel company EF, takes such advice to heart and makes sure her travel groups do, too. “It frightened me so I wanted to make sure the people who travel with me are aware,” she said. “I give them tips to reduce swelling. And I tell them when they get to their hotel room to lay down and put their feet against the headboard for a while. Doing those things has eliminated the problem.”