DEAR DOCTOR K: Last year I developed deep vein thrombosis (DVT) — blood clots in my legs — during a long international flight. One of the clots got loose and went to my lungs. I’m fine now and am off all medications. Is it safe for me to fly again?
DEAR READER: Yes, you can fly again if you take some precautions. Before I describe them, though, a little background information is in order:
Deep vein thrombosis (DVT) is a blood clot that forms inside deep veins in your legs or pelvis. Part of the clot can break away and move through your bloodstream to your lungs. If the clot blocks one or more of the blood vessels in your lungs, it is called a pulmonary embolism (PE). If the clot is big enough, it can damage the lungs. It can even cause sudden death.
We are all at some risk for developing DVT if we do something that slows the blood flow in the veins of our legs. When blood isn’t moving, it tends to clot. One of the things that keep blood moving through the veins of the legs are your leg muscles. When you use those muscles — when you walk, for example — they squeeze the veins and keep the circulation going.
When you’re sitting on a long flight, you’re not doing much, if any, walking. Sitting in a cramped plane seat also slows the flow of blood at the knee. When your leg is stretched straight out, blood flows easily through the veins. But when the knee is bent, blood flow slows.
Still, most people who sit on a plane for many hours, never walking and always with their knees bent, will not develop DVT.
The fact that you developed a DVT and a PE indicates that you may have been born with a tendency for your blood to clot more easily than is the case for most people. Having one DVT or PE means you are at high risk for another. If you were my patient, I would perform tests for various inherited conditions that cause blood to clot easily. I would also consider whether you should take an anticoagulant medication, such as warfarin, to help protect against blood clots indefinitely.
Now back to airline travel: Prolonged sitting and dehydration — common on long flights — create ideal conditions for blood clots to form. Everyone embarking on a long flight should do these things to minimize the chances of developing a DVT or PE:
—Stay hydrated. Drink enough water during the flight to make you get up and use the restroom several times.
— Avoid alcohol, which can dry you out.
— Move your muscles. Stand up and stretch your arms and legs at least once an hour. Walk up and down the aisle, or walk in place. While standing or sitting, do simple exercises such as straightening your knee and stretching your leg and pointing your toes up and down.
— Consider compression stockings. Elastic support stockings keep blood flowing by gently squeezing the legs and moving blood back to the heart. Consider using these when you travel in a seated position for many hours.
Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115