Watch out for the killer legs!

By Henrylito D. Tacio

Blurb: Air travelers are at increased risk of blood clot

FORMER American Vice-President Dan Quayle never knew what hit him. He was promoting his memoir, Standing Firm, when he experienced severe shortness of breath and had trouble finishing his speeches.

He thought it was just bad cold and didn’t bother to see a doctor. It was a bad decision.  On November 27, 1994, he was brought to the emergency room at the Indiana University Medical Center.  The doctor’s diagnosis: “walking pneumonia.”

Quayle, then 47, was sent home and thought it was over.  The following day, however, his breathing difficulty worsened and was admitted to the emergency room again. After further tests, doctors re-diagnosed his condition as a “pulmonary embolism” or having a blood clot in his lung.

“You’d be surprised how often a pulmonary embolism is missed, even with most skilled physicians,” Quayle said in a statement following his release. “Misdiagnosis is common. I was lucky…very lucky.”

He was indeed very lucky.  According to the National Institute of Health, more than 600,000 people in the United States have a pulmonary embolism each year, and more than 60,000 of them die. Experts say that most of those who die do so within 30 to 60 minutes after symptoms start.  

In most cases, pulmonary embolism is a complication of a medical condition called deep vein thrombosis (DVT), in which a blood clot forms inside the deep veins of the lower legs, thighs, or pelvis.  Although there is no single, simple cause, a DVT may be due to
injury to the lining of the vein, changes in the pattern of blood flow (like compression, turbulence, and stagnation), and increased tendency for blood to clot and for that clot not to naturally dissolve again.
“One out of three causes usually does not trigger a DVT and three out of three is fortunately uncommon,” says Dr. Rene De Jongh, South Asia medical director of the assistance services of International SOS in Singapore. 

While DVT has given much attention in the United States and Europe, such is not the case in Asia .  “Authorities in Asia, especially governmental organizations, tend to be very conservative and overly cautious about going public regarding health issues like DVT,” says Dr. Walter Fister, whose special interest is on public health and works with the Mount Elizabeth Medical Centre in Singapore .  (He cites the initial responses to the SARS and bird flu outbreaks as examples of this approach.)

As such, “information about DVT leaves a lot to be desired in this part of the world,” adds Dr. Haizal bin Haron Kamar, associate professor in medicine and cardiology at the University of Malaya in Kuala Lumpur.   “In fact, the public is not aware of the potential health risk of blood clots.”

Clotting the blood is “nature’s way of trying to prevent bleeding,” says Dr. Rafael Castillo, a cardiologist and chair of the department of medicine of the Manila Sanitarium and Hospital. But when nature’s protective mechanism goes awry, there is a danger of blood clots resulting in a DVT.

Health authorities claim DVT is instigated by prolonged periods of physical immobility. “I f a person is just sitting around and not moving, say, during a very long flight, he may risk himself of developing a DVT,” says Dr. Gary Raskob, dean of the college of public health at the University of Oklahoma Health Sciences Center.

How does DVT happen?  It starts with blood clots forming in the veins of the legs during hours of immobility (that is, long-haul flights). When mobility resumes (for instance, once a passenger deplanes) the clots can break free of the vein, and travel to the lungs causing a pulmonary embolism that may result to death.  

In a study published in Aviation Space and Environmental Medicine, 87 percent of identify DVT cases identified occurred following either a return trip or after an outward journey involving long trips made up of sequential flights.   In France, researchers from the Hospital Pasteur claim that air travelers who sit for more than five hours on planes are more likely to develop blood clots in their leg than non-travelers.  

At Narita hospital near Tokyo’s International Airport, records show an average of 100 to 150 passengers are treated for DVT immediately upon arrival each year; three to five percent of those die.

“Only one percent of air passengers suffers from DVT,” Dr. Farrol Kahn, head of the United Kingdom-based Aviation Health Institute.   “Other passengers who have predisposing factors have a higher risk of between five to six percent.   About 10-15 passengers on a jumbo jet (Boeing 747) could develop a DVT.”

In the popular press, DVT is sometimes called “economy class syndrome.” Thomas Lamb, 68, had been sitting in his economy class seat for almost a day from London to Australia in 2000.  When he arrived in Melbourne, he had breathing difficulties and was taken to the hospital where he fell into a coma and later died.

The term “economy class syndrome,” in use since 1977, is slightly misleading. For instance, American President Richard Nixon, who suffered DVT after visiting China in 1972, was not flying economy; he was on his presidential jet. “It’s wrong to assume that it is limited to economy class passengers,” argued Dr Kahn, who has authored several books on aviation health and medicine.  ” Air-travelers DVT is a better name.”

Although DVT is mostly associated with elderly travelers, younger ones are not spared.   Briton Emma Christofferson was only 28 when she succumbed to DVT.  She was traveling home to London from a three-week trip to Australia, on a flight via Singapore in 2000. After disembarking at Heathrow, in London, she made her way to the arrival hall with the other passengers. Suddenly, unable to breathe, she collapsed and died before reaching a hospital. 

There are multiple risk factors for developing blood clots in the leg, health authorities claim.   There are genetic risk factors and then superimposed on that are risk factors such as having surgery or a trauma.  “It is likely that most individuals who develop a DVT during or after a long plane flight also have an additional risk factors,” maintains Dr. Raskob. 

This has been confirmed in a study which appeared in British Journal of Hematology.  It concluded that the risk of DVT was only increased in long-haul travelers if one or more additional risk factors were present.

According to Dr. Fister, the risk of DVT is greater in the following people: older persons (over 40 years of age); have had previous blood clots; with a family history of blood clots or an inherited clotting tendency; suffering from or who have had treatment for cancer; with certain blood diseases; being treated for heart failure and circulation problems; have had recent surgery especially on the hips or knees; and pregnant.

Obese, smokers and tall people are also at risk.  “Women who take birth control pills or undergoing hormone replacement therapy are also likely to suffer from a DVT because estrogen is a risk factor for clotting,” informs Dr. Raskob.
In fact, DVT is not just caused by air travel.  In 2003, American television anchorman David Bloom, 39, died from DVT after riding hours upon hours, day after day in a cramped tank while covering the war in Iraq.  Since reported DVT cases around the world are sketchy despite well-publicized by media, airline officials are rejecting the idea of any link between flying and DVT. 

“DVTs has been reported in medical journals as early as the 1950s but we still don’t have a clear idea on the actual incidence of DVT in travelers and its associated morbidity or mortality,” says Dr. Fister, who has been advising travelers about the hazards of DVT. “Further study is needed to clarify.”

In 2001, the Geneva-based World Health Organization convened a symposium of medical experts and 16 airline officials. In a statement issued after the meeting, the airline industry representatives conceded that there “probably exists an association between venous thrombosis and travel in general,” and that more research is needed into DVT triggered by travel.

So be it, argues Dr. Kahn.  “There is a greater likelihood of a DVT occurring in flight than on ground transport because the three factors that can cause it to develop are found in the cabin environment: prolonged sitting, dry air, and lower oxygen levels that trigger blood clots,” he says.

Almost half the time, DVT strikes without warning.  “Up to 50 percent f all DVT cases are unknown — most likely even higher – since most people may not experience any symptoms at all,” says Dr. Fister.  “Most likely lots of people get DVT without any knowledge and where the clot forms and dissolves all on its own and they are none the wiser.”

In most instances, doctors misdiagnose DVT. “The symptoms and signs are very ‘non-specific,’ meaning they may be caused by many different medical conditions,” explains Dr. Raskob.   “DVT is frequently mistaken for other conditions such as muscle strains, skin infections, heart failure, dependent edema and ruptured Baker’s cyst,” informs Dr. Haron.

In instances where symptoms do present themselves, they may include: deep muscle pain, muscular tenderness, swelling or tightness, discoloration of the affected area, and skin that feels unusually warm.  “More often that not, these classical symptoms are found in only a minority of cases,” says Dr. Jongh.

Pulmonary embolism, DVT’s fatal complication, is also hard to diagnose.  Just as the symptoms and signs of a DVT are not unique to it, the presenting or warning signs of a PE are not characteristic either, as some, many or none of the following may be evident: sweating, fainting, feeling short of breath, feeling pain or tightness in the chest, having a fast pulse, and coughing up blood-stained phlegm, among others,” says Dr Jongh.

“DVT does not occur during the flight but after the flight hours or days later,” reminds Kahn.  “Even two to three weeks later, anyone who experienced some symptoms should consult their doctors. They should tell them that they have been on a flight and ask to check them for possible DVT.”

Symptoms alone are not the only basis for a person to be diagnosed of suffering from a DVT.  Dr. Mark Ebell, associate medical professor of the Michigan State University, says the most commonly used diagnostic tests for DVT include ultrasound (test blood flow through the veins), constant venography (monitoring the progress of dye injected into the bloodstream), chest x-ray/scan (for people with breathing difficulties), arterial blood gas (to measure the amount of oxygen and other gases in the blood), and magnetic resonance imaging (MRI).

“In many parts of the world, including Asia, patients and doctors simply do not have access to the technologies to make the diagnosis quickly and painlessly,” deplores Dr. Jongh.

Drugs that thin the blood and allow it to flow more easily are the primary treatment for DVT or similar problems with clotting of the blood. On diagnosis of a DVT, this usually initially involves giving high doses of the drug heparin by injection.  Patients are also prescribed a similar drug, warfarin, in tablet form, which they may take for several months.

When taking these blood-thinning drugs patients usually have regular blood tests to make sure they are getting the right dose and are not at risk of a hemorrhage. “The use of heparin should be stopped once the dose of warfarin has stabilized,” says Dr. Kamar.

Doctors say a simple aspirin tablet taken a few hours before take-off thins the blood during long periods of inactivity. The number of victims would fall significantly if more air passengers followed this advice.

In its website, Singapore Air Lines recommends to air travelers to exercise during flights. “The safety of our passengers is always of paramount importance and we refer to the possible effects of flying in our in-flight magazine.”

Japan Airlines, the biggest user of Narita airport, advised its passengers to stretch their legs.  “If you can’t walk during the flight, flex your ankle up and down, as if you are stepping on the accelerator in the car,” says Dr. Fister. “Do this exercise about 20 times every two to four hours you are in flight.”
Another problem: Plane air is dry, and fliers can easily become dehydrated. “When you are dehydrated, your blood becomes thicker, increasing risk of clots,” says Dr. Kamar. “To avoid dehydration, drink plenty of water.  Avoid alcohol and coffee, if possible.”

Other experts advise passengers to dress comfortably and in loose clothing. “Avoid tight garments and shoes.  For a long flight, pack slippers or an extra pair of warm socks.  These not only keep your feet warm but also allow the blood in your feet to circulate more freely,” says Dr. Castilo.

“Wear approved compression stockings to cover the length of the whole leg to give support to the veins and reduce swelling,” recommends Dr. Jongh. Studies have shown that flight socks are effective in controlling edema and in reducing the incidence of DVT among low-medium-risk people in long-haul flights (7-11 hours).

The problem of DVT is expected to be more prevalent as air travel is becoming increasingly more accessible to people both through the availability of cheap flights and because the airlines are now able to cater for individuals of all ages and disabilities. – ***


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