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Q: I'm concerned about preventing an embolism occurring due to poor circulation in my legs. When I drive long distances, I move my right leg as needed to brake and accelerate. But my left leg just lays there unless I rotate it frequently. What do you think?
A: Circulation is split into two parts. The first part takes the blood from the heart, through the arteries and out to all the tissues of the body. The second part returns the blood from the tissue, through the veins back to the heart and lungs.

Based on your concern about an embolus, I presume your problem is with the circulation in your veins. The legs contain two major groups of veins -- the superficial veins, located just under the skin, and the deep veins, located among the leg muscles.

While the function of both groups is to return venous blood to the heart, the deep veins move most (90 percent or more) of the blood. That's because they are surrounded by calf muscles.

The constricting and relaxing action of these muscles, as occurs, for instance, when you walk, compresses the deep veins, pumping the blood upward. Also, veins contain many one-way valves that keep the blood from flowing back down.

Anything that disrupts this process will cause blood-flow problems, including venous stasis, which is defined as the stoppage or impairment of blood flow through the veins. ("Stasis" is from the Greek for "standing still.")

A major cause of venous stasis is immobility, such as from bed rest after operations, obesity and stroke. With immobility, the leg muscles aren't compressing the veins and the venous blood flow is reduced. Surgery and trauma to the legs also can impact the valves of the deep veins and surrounding muscles.

This reduced functioning results in an accumulation of fluid (edema) in the area. The swelling may cause pain, but it is often painless. Poor circulation and edema also start the process of ulceration, a primary complication of venous stasis.

Venous stasis ulcers are skin-surface sores that typically begin with edema under the skin in the affected area. Over time, the skin becomes red and scaly. Then the pigment of the skin darkens, and the skin tissue begins to break down and ulcerate.

Symptoms that occur with this process include early itching, dull discomfort made worse by standing, and eventually pain when ulceration begins.

And a third problem is the potential for the development of blood clots in the veins. When this happens, a clot can break off (it's then called an embolus) and travel toward the heart.

If the embolus stays intact, it can travel though the heart and into the lungs. This is called a pulmonary embolus. When the blood clot finally stops in smaller blood vessels of the lungs, it will block off part of the blood flow to that section. This in turn will cause pain and shortness of breath. If the blood clot is large enough, it can cause death.

As you are aware, sitting or standing for long periods of time should be avoided. Sitting is a particular problem when there is prolonged pressure on the back of the legs that blocks off the veins.

Repeatedly moving the right foot from break pedal to accelerator will lessen the problem for that leg. But during long-distance driving, holding the accelerator down for extended periods can actually increase the pressure on the back of the leg.

I suggest you adjust your car seat to take pressure off the backs of both legs; use cruise control to allow moving and flexing the muscles of both legs as your drive; and most importantly, stop often and get out and walk around.

Also, check with your doctor to see if treatments such as elastic stocking and anticoagulants may be helpful.

Write to Dr. Allen Douma in care of Tribune Media Services, 435 N. Michigan Ave., Suite 1500, Chicago, Ill. 60611; or contact him at This column is not intended to take the place of consultation with a health-care provider.

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