Deep vein thrombosis (DVT) occurs when a blood clot forms in a deep-lying vein, usually in the legs. It affects up to 600,000 Americans per year. The danger of DVT is that a piece of the blood clot can break off and travel to the lungs, causing a sometimes-fatal condition called pulmonary embolism. About 10 percent of people who develop pulmonary embolism die from it.
"Air travel may be associated with heightened potential for developing deep venous thrombosis. When we travel in an airplane, we're often sitting in a very cramped position for long periods of time," says Thomas Wakefield, M.D., a vascular surgeon at the University of Michigan Health System.
Studies show it's the longer flights that put people at risk. So international travel where the flights last eight hours or longer are the biggest concern.
Three conditions increase the odds of developing DVT: Not moving for long periods, clotting disorders or other abnormalities in the blood, and problems with the veins themselves. People on bed rest after surgery, as well as long-distance travelers, risk blood pooling in their veins when they don't move. Certain medical conditions such as stroke, heart attack, cancer and paralysis also put people at increased risk of developing a blood clot.
"Perhaps the most important risk factor is age. We know as we age that our chances of developing deep venous thrombosis significantly increase," says Wakefield, professor of surgery at the U-M Medical School. "There is also mounting evidence that obesity, in and of itself, is a risk factor for the development of deep venous thrombosis."
If you're flying a long international flight, pay attention when the airline shows the video describing exercises you can do in your seat. Wakefield says those moves do help decrease the risk of DVT. In addition, try to switch positions or move around in your seat to avoid sitting with your thighs against the seat edge for long periods.
Not only is sitting still an issue, but the pressurized cabin air decreases the amount of oxygen available. That could cause a decrease in oxygen in the bloodstream, which makes the veins more prone to clotting.
Look out for the beverage cart too. Alcohol and salty snacks will cause dehydration, which can contribute to DVT risk. Wakefield recommends trying to stay well hydrated " so stick to alcohol-free, caffeine-free beverages in flight.
While the decreased oxygen in an airplane cabin and the likelihood of dehydration are specific to air travel, DVT is still a risk if you're traveling long distances by car.
"I often tell my patients when they take long automobile trips to get out of the car every hour or so, to stretch and walk around. Be aware of sitting for too long, especially those who have risk factors for DVT," Wakefield says.
Some signs that a blood clot has developed may be pain, swelling or redness in the leg. But often, there are no symptoms of DVT. If you notice any symptoms after a long flight, see your doctor. Ultrasound is most frequently used to diagnose DVT. Once diagnosed, it can be treated with the blood thinning medication heparin or one of its derivatives.
"It's not a perfect treatment, but you can decrease your risk of thrombus recurrence and pulmonary embolism by about 90 percent to 95 percent once you begin the medication," Wakefield says. "It's a very successful treatment for limiting the development of pulmonary embolism."
Risk factors for DVT:-Increased age-Bed rest, major surgery or other trauma-Prolonged sitting or immobilization-Oral contraceptives or hormone replacement therapies-Malignancy and its treatment-Pregnancy-Stroke-Paralysis-Previous DVT-Obesity-Heart attack or congestive heart failure-Clotting disorders-Inflammatory bowel disease-Nephrotic syndrome-Respiratory failure-Indwelling catheters (a tube that drains urine from the bladder into a bag)-Varicose veins
Symptoms of DVT:"¢ Swelling in the leg"¢ Pain or tenderness in the leg"¢ Increased warmth in the leg"¢ Redness or discoloration
Resources:
U-M Health Topics A-Z: Deep vein thrombosis:http://www.med.umich.edu/1libr/aha/aha_dvthromb_sha.htm
American Public Health Association: Deep Vein Thrombosis:http://www.apha.org/news/press/2003/DVT_whitepaper.pdf
National Heart, Lung and Blood Institute: What is deep vein thrombosis http://www.nhlbi.nih.gov/health/dci/Diseases/Dvt/DVT_All.html
Society of Interventional Radiology: Deep vein thrombosis overviewhttp://www.sirweb.org/patPub/DVTOverview.shtml
NASA: Economy Class Syndrome:http://ohp.nasa.gov/alerts/dvt.html
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