Socks on a Plane: How Serious is Deep-Vein Thrombosis?

We've all heard of deep-vein thrombosis (DVT) and the risks it brings for frequent flyers. Traditional wisdom is that the best way to stay safe on long-haul flights is by wearing special tight socks and taking frequent strolls (preferably walking backwards, if your ayi is to be trusted) down the airplane aisles. But is really necessary? What is DVT anyway? How careful do I really need to be? Here to explain is Vascular Surgeon Dr. Zhai Mengyao from Beijing United Family Hospital (BJU).  

What is DVT?

DVT is short for deep venous thrombosis (or deep-vein thrombosis). It describes a condition in which a blood clot (thrombus) forms in a vein. This clot can limit blood flow through the vein, causing swelling and pain. 

In human arms and legs, there are superficial and deep venous systems. A superficial vein, like the great saphenous vein in the leg, runs closer to the skin and carries less venous blood flow. A deep vein, like the femoral vein in the leg, runs closer to the central axis of the leg and carries more venous blood flow. Clots in a deep vein (DVT) cause more severe symptoms and worse consequences than superficial venous clots. Most commonly, DVT occurs in the deep veins in the calves, thighs, or pelvis.

Fig 1: Vein systems in the leg (source: Uptodate)

Is DVT a common problem? 

DVT is a rare condition. The accurate incidence is hard to estimate because of misdiagnosis and missed diagnosis. But the risk of DVT rises in certain groups of people.

Who is at risk of DVT?

There are a number of factors that increase the risk of developing DVT. These include:

• Immobilization (e.g. due to hospitalization, recovery from injury, bed rest,  paralysis, or long flights);

• Recent surgery or trauma (especially those involving the hip, pelvis, or knee, which usually cause prolonged inactivity);

• Obesity;

• History of venous clots;

• Cancer;

• Use of birth control pills or hormone replacement therapy;

• Being pregnant or having recently given birth;

• Advanced age;

• Family history of venous clots;

• Heart failure;

• Inflammatory bowel disease;

• Smoking;

• Kidney problems, such as nephrotic syndrome; or

• Inherited or acquired thrombophilia (a problem that causes the blood to clot more easily than normal).

What are the complications of DVT?

Leg DVT usually causes significant pain, swelling, redness, and warmth in the affected leg. 

Fig 2. Left: A clot in a deep vein. Right: Appearance of a leg with DVT (source: designed by vascular surgeon Dr. Huang Liu Huan of BJU)

If a part or all of the blood clot in the vein breaks off from the site where it is formed, it can travel through the venous system; this is called an embolus. If the embolus lodges in the lung, it is called a pulmonary embolism (PE), a serious condition that may lead to death. Among all DVT patients, the incidence of PE is very rare. Timely and proper treatment can further lower the risk of PE.

What are the symptoms/warning signs of DVT?

If you feel a sudden onset of pain, spasm, or tightness in your leg (it’s usually just in one leg), and/or you see that one leg is much bigger than the other, you may have a clot in a vein in your leg. The more risk factors you have, the greater the possibility you have a clot. The warning signs of an acute PE include chest pain, bloody sputum, shortness of breath, or even the feeling that you cannot breathe. If you notice any of these signs, you should call an ambulance or have someone to take you to an emergency room nearby.

Do I really need to pay attention to DVT when I’m on a long-haul flight? 

Long-distance travel, either by air or land, does increase the risk of venous thrombosis. The risk even exists in the first two weeks after travel.  It is reported that the overall incidence of symptomatic venous thromboembolism (VTE) is 0.5% for flights longer than 12 hours, while other studies report rates of asymptomatic VTE as high as 1.5% to 10 percent during extended travel of 24 hours or longer. If you are taking a really long fight, bus ride, or train journey and have one or more other risk factors mentioned above, then you need to do something during the trip to reduce your DVT risk.

What can I do to reduce my risk of DVT? 

In daily life, it is not necessary to do anything to prevent venous clots. But, to help boost the general health of your leg veins, we do recommend avoiding standing or sitting still for a long time. Keeping your body weight within a healthy range is also crucial to preserving your leg vein function. During long-distance travel, here are some suggestions for you to reduce your risk of DVT:

• Walk around frequently (every one to two hours);

• Flex and extend your ankles (to stretch your calf muscles) and knees (to stretch  your thigh muscles) often;

• Avoid agents that may promote immobility or dehydration (e.g., sedative drugs, excessive alcohol consumption);

• Wear a pair of graduated compression stockings (15 mmHg-30 mmHg at ankle level).

For those who have a history of DVT or confirmed strong risk factors for DVT, you should consult with a vascular surgeon for professional suggestions on prevention of DVT.

Fig 3. Flexion and extension of the ankles (source: photo taken by vascular surgeon Dr. Huang Liu Huan of BJU)

Dr. Zhai Mengyao is a general surgeon and a vascular surgeon at BJU. She speaks Mandarin and English. To make an appointment  with her, please call the BJU Service Center at 4008-919191. 

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