As someone who speaks professionally for a living, I spend a lot of time on airplanes.  A lot.  Long international trips (a recent trip to Bangkok consisted of a 5 hour, then a 15 hour, and finally a 7 hour flight), medium length flights across the U.S., and shorter flights up and down the east coast.  In addition to the lousy food, stuffy air, and constant crowds ubiquitous to airports, there are actually real health dangers associated with air travel.  Whether like me you travel frequently, or if you only rarely board a plane, there are a handful of simple precautions you can take to protect yourself from both more common troublesome and rare life-threatening consequences of air travel.

During your normal daily activities, the muscles of your thighs, legs, and feet are often active.  You’re walking, turning, bending, getting in and out of chairs or your car.  All of your routine daily activities utilize the muscles in your thighs, calves, and feet.  And this frequent contraction and relaxation of your legs muscles affects the blood within the veins that travel through those muscles.  All of that muscle activity squeezes the blood within the veins, helping to pump the blood and support active blood flow.

Also throughout the day, you’re taking in fluids.  Whenever you get thirsty, you drink.  Water, juice, and other liquid intake ensures that your blood volume remains adequate, your blood vessels full, as water absorbed from your drinks replenishes water lost from your circulation, and any extra fluid is simply released in your urine.  (Note that coffee, tea, sodas, and energy drinks containing caffeine, as well as alcohol and certain other drinks, do not replenish your blood volume, as they promote fluid loss through excess urination.)

But these normal activities, the frequent use of your leg muscles and the regular intake of fluids, are greatly curtailed during air travel.  You’re stuck for hours, immobilized in a cramped coach seat.  You wait endlessly until finally offered that tiny plastic cup filled with juice or (worse, because it furthers dehydration) a caffeinated drink.  The bone-dry plane air pummels you from that little spout above your seat.

This combination of lower extremity immobility and mild to moderate dehydration lead to “venous stasis,” the slowing of blood flow within the veins of the thighs, calves, and feet.  And when blood flow slows enough, small blood clots can form within these veins.  The formation of such lower extremity blood clots is called deep vein thrombosis (DVT) formation, and the clots are referred to as DVTs.

It is likely that many air travelers develop DVTs and never know it.  For these symptomless individuals, the blood clots cause no problems, and the body breaks down and reabsorbs the clots soon after formation.  Others are not so lucky, and the blot clot (DVT) obstructs blood flow within the vein, causing swelling of the lower leg, ankle, and/or foot, and redness, warmth, and real pain which requires medical treatment.  And for a very unlucky few, the blood clot in a deep vein actually breaks free of the vein wall and travels in the blood stream, eventually lodging in the lung.  This catastrophic event, called a pulmonary embolism (PE), causes sudden shortness of breath and can even first present itself as a sudden death.  PE requires immediate, emergent treatment to prevent serious complications and death.

All air travelers are at risk for DVT, but several factors clearly increase your risk of developing a DVT when taking a trip.  First, long flights of over 4 to 6 hours increase your risk of clot development.  For the over 300 million travelers who take flights of this or greater length annually, the risk of DVT development is as high as 12%.  Age impacts risk, with travelers of forty years and older at a greater risk of clot development.  And women are at slightly greater risk, a risk that is further increased in women taking oral contraceptives.  And obese individuals also have an elevated risk, as do those with varicose veins and folks with a known predilection to blood clot development.  And all of these risks are increased by immobility (absence of leg muscular activity) and dehydration.

I take a lot of 4 to 6 hour and longer flights.  And I am over forty.  So what do I do?  First of all, I drink.  A lot.  Once through security, I buy water or juice and begin chugging before I ever get on the plane.  And then while on the plane.  And when the flight attendant offers me that tiny cup of apple juice, I politely ask for the whole can (they always say yes).  And then I drink that can during the remainder of the trip.

And I get up.  Often.  I stroll, usually to the bathroom, which is a frequent need given all that water and juice that I’m drinking.  Honestly, I feel reassured when I repeatedly have to pee, reassured that my blood vessels are full and the blood in the veins of my legs is flowing, as demonstrated by the excess fluid that my body is releasing on every trip to the lavatory.  And when I can’t get out of my cramped seat (particularly during boarding, while we taxi to the runway, and for the first thirty or so minutes of each flight), I pump my venous blood by flexing and extending my feet at the ankles (which you feel tightening and loosening the calf muscles) and, to the extent possible, extending and flexing my knee and hip joints.  (No doubt those sitting next to me are amused…or disturbed.)

So drink before, during, and after your flight.  And get up frequently.  When confined to your seat, flex and extend your ankle, knee, and hip joints.  And for those at increased risk, consider wearing elastic compression stockings during your flight (available in most pharmacy departments), as these decrease venous blood stasis and clot formation.  (If you have a medical condition which greatly increases your risk of blood clot development, speak with your physician partner, who may suggest medication to further decrease your DVT risk during flight.)

The other obvious risk of air travel is contracting a virus resulting in a cold, the flu, or stomach distress which ruins the vacation or business trip waiting at the end of your flight.  The airport and your airplane are filled with people who are filled with contagious viruses.  Many common viruses are spread through microscopic respiratory droplets which can travel several feet through coughing, sneezing, or even just talking.  And some viruses are tough; they can survive and remain infectious after landing on surfaces such as chairs and counter tops, waiting until you unknowingly pick them up on your hands and then touch your mouth or nose or eyes, transferring viruses into your body.

So what do I do?  A couple of things.  First of all, I wash my hands frequently before, during, and immediately after every flight.  Soap and water is fine, but if you wish to also carry a small bottle of alcohol gel on the plane, that’s fine (though likely less broadly effective than simple soap and water).  Secondly, studies demonstrate that appropriate use of zinc reduces the duration of a cold, and while studies are mixed as to the power of zinc to prevent a cold, there is enough support (plus my personal experience) and no health risk, leading me to pop a zinc lozenge to suck before boarding my flight. 

So if you’re on an airplane, and you notice a gentleman sucking away on a lozenge while drinking heartily from an apple juice can and frequently going back and forth to the lavatory, say “hi.”  It’s me.  The guy who has no interest in blood clots or infections interfering with my post-flight plans.

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