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Tips to prevent clots

Dom DeLuise, Ian Anderson of Jethro Tull, Vice President Dan Quayle, and David Bloom: What do a comedic actor, rock and roll icon, politician, and reporter have in common? Deep vein thrombosis (DVT), a clot forming deep inside the legs that has the capacity to kill. It killed David Bloom in 2003 while he was reporting from Iraq. Pilots also need to be alert to this particular ailment.

Oxygen and nutrient-rich blood is pumped around the body by the heart and travels through muscular arteries that transmit the strong, cardiac contractions maintaining good blood pressure. On reaching tissues throughout the body, large-diameter arteries branch into ever-smaller arteries, arterioles, and eventually tiny capillaries, tubes that allow oxygen and food elements to diffuse out, and carbon dioxide and waste products to diffuse in. The force from the original heart pulsation becomes ever less as the tubes narrow and spread out, and as the waste-product-rich blood leaves the capillary bed it enters small venules which coalesce to become veins. These nonmuscular tubes ride alongside arteries and pick up some pulsatile force from them to encourage the venous blood on its journey back to the heart. Additionally, in the legs, the veins can be found inside calf and thigh muscles, and as we walk muscular contraction exerts a squeeze on the veins helping drive blood back to the heart. Of course, you can imagine how much harder it is for this muscular pump to encourage blood uphill maybe three or four feet when we are standing up. 

Several things can lead to thrombosis, commonly called a clot. First, anything that makes the blood “thicker,” such as being dehydrated or consuming alcohol, can increase the risk. Certain drugs such as oral contraceptives can raise the tendency to clot whereas aspirin has the opposite effect. Smoking, obesity, high fat levels in the blood, a low oxygen environment, and being sedentary also have a major impact. Prior pelvic surgery or being pregnant, a previous episode of DVT, varicose vein surgery, or anything that impedes the return of blood from legs to heart, such as a constrictive item of clothing, or the edge of the seat pressing in on the back of the knee can also induce a clot to form. 

When a DVT occurs it may have no symptoms at all or cause fever, pain, heat, and swelling in the affected area (most commonly the calf), and limitation of movement in the afflicted limb. For instance, with the knee straight, pulling back on the foot causes pain in the calf, something we call Homan’s sign. A diagnosis is confirmed by using a Doppler ultrasound to look at flow in leg veins and if a DVT is seen, a long period of anticoagulation therapy is commenced to prevent the feared complication of pulmonary embolus. This is where a chunk of clot breaks off and travels up to the lung where it can cause sudden death or at best, a bloody cough, breathlessness, and residual scarring.  

So, given that the above description firmly puts DVT in the category of things I do not want to have, what can you do to avoid this problem?

  1. Watch your weight.
  2. Stop smoking.
  3. Get your blood lipid levels checked regularly.
  4. Be well hydrated and avoid alcohol when flying (obviously I am referring to commercial aviation here; for piloting it should be a given).
  5. Consider a small daily dose of aspirin—81mg—if in discussion with your doctor you are deemed to be at risk. Remember, also, that aspirin is a reportable medication on your FAA medical application (MedXPress).
  6. Wear support stockings when flying.
  7. Avoid constrictive clothing such as tight pants or belts.
  8. Exercise regularly.
  9. Do foot, ankle, and leg exercises on board every 15 minutes or so. When on an airliner, get up and take a walk.
  10. Consider some newer exercise modalities. 

I recently met Jerry Collins, CEO of Treadwell, and as he is a fellow pilot, I was intrigued to see the Tredlr exercise tool his company has developed. A flywheel-driven device, the Tredlr allows low-impact exercise mimicking pressing rudder pedals alternating right and left. Such movements may improve blood flow and limit the risk of DVT. How nice that one of our own is thinking about this topic. 

When David Bloom died I was involved in an awareness campaign on this topic and some of the folks mentioned in my opening sentence participated in public service announcements. The slogan that stuck with me came from Ian Anderson, whose song "Too old to rock and roll, too young to die!" became an anthem for his message. Let’s all agree we are too young to die, and ensure we take care of our health.

Jonathan Sackier

Dr. Jonathan Sackier is an expert in aviation medical concerns and helps members with their needs through AOPA Pilot Protection Services.

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