Deep-Vein Thrombosis and Air Travel: Is There a Connection?

By Wesley Hyatt, DAN Communications

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Generally, deep-vein thrombosis is not fatal. In this condition, a thrombus, or blood clot, forms when blood pools in the deep veins of the calf or the thigh after prolonged periods of remaining in the same position. However, a clot that breaks off and moves into the lungs or heart can block circulation and kill a person. Pain, redness, swelling and tender leg muscles can signal DVT. But it can occur with no warning signs or symptoms.

In January 1999, Brad Perkins, his wife Karen, their daughter and son flew overnight from San Jose, Calif., to Miami, Fla., on the first leg of what Brad estimated was 10 hours total of flying time to a diving location off Belize.

"My guess is she developed it on the red-eye flight," said Brad. "It" was deep-vein thrombosis (DVT), a condition Brad attributes as the cause of Karen’s death a day after the plane ride. Like many travelers on overnight cross-country flights, she stayed in her seat and drank nothing, factors that contribute in developing DVT.

In DVT, a blood clot forms when blood pools in the deep veins of the calf or the thigh, the result of a person remaining in the same position for an extended period. Perkins believes his wife suffered a blood clot that broke off and moved into the heart or the lungs.

The Perkinses changed planes in Miami for the three-hour flight to Belize and then caught a passenger plane to their dive site off Belize. The next morning Brad, Karen and their son went scuba diving.

Amid rough currents at the descent line, Karen Perkins joined her husband and son in the water. She kicked to maintain her balance on the line when, her husband believes, a clot that formed in her leg during the flight went through her bloodstream and stopped her circulation. She gasped for air. "She hadn’t even put the regulator in her mouth," Perkins said. "Karen’s eyes rolled back before the crew brought her on board."

The divemaster alerted them to abort their dive. "By the time I and my son got back up, she was on deck getting CPR," Perkins said. "Karen died shortly thereafter."

"When she died, we didn’t know what happened. We guessed a heart attack, because she had gone quickly and had been in good shape. The autopsy in Belize couldn’t find the cause. There was no sign of heart attack or stroke in her autopsy."

A few months later Karen Perkins’ parents, both doctors, heard from a colleague about the belief in a connection between DVT and extended plane travel. They and Brad Perkins now think her death was a result of that condition, often called "economy-class syndrome" and "coach-class syndrome."

‘Economy-Class Syndrome’

The condition was first noticed in 1940 among Londoners who sat long hours in cramped air-raid shelters while Germans bombed their city. It became linked with flying in 1977, when the term "economy-class syndrome" appeared to describe the supposed link between getting blood clots and staying in the tight confines of a coach seat for long periods of time, typically transcontinental airline flights. The phrase, though descriptive, is not accurate; passengers in first- and business classes have also claimed to have suffered DVT.

Nevertheless, some doctors in a hospital near London’s Heathrow Airport, a hub for international visitors to the United Kingdom, attribute 30 deaths over the last three years to "economy-class syndrome." But the most publicized case of DVT from air travel occurred before a victim reached that hospital.

On Sept. 29, 2000, 28-year-old Emma Christofferson headed home to Newport, South Wales from Australia, via a 12,000-mile Qantas flight, which included a seven-and-a-half-hour flight to Singapore, a one-and-a-half-hour stopover for fuel and then a 13-and-a-half-hour flight to London. She collapsed at Heathrow Airport and died shortly thereafter. A post-mortem exam confirmed the cause of death as DVT. Reportedly in excellent health in Australia, Christofferson had been scuba diving in the Great Barrier Reef prior to her departure.

Her death prompted some legal action in Australia and the United Kingdom. The Melbourne, Australia law firm of Slater and Gordon announced in December 2000 it would represent plaintiffs in actions against Qantas, British Airways, Air France and Air New Zealand, since the airlines had not warned passengers of the risk of DVT. And British travel insurer Club Direct said in February it would aid in paying legal fees of up to 25,000 pounds ($37,000 US) for travelers or their relatives who sued an airline over a DVT death or injury. Club Direct officials said they took the action to force airlines to include information on board on how to reduce the chance of DVT.

The issue of DVT during air travel has not gone unnoticed in the United States. In the Jan. 16, 2001 edition of The Los Angeles Times, an editorial titled "Economy-class syndrome" urged airlines to provide more legroom for passengers to help prevent fatal DVT. The Wall Street Journal wrote about it in a front-page story on June 27, 2001. And Perkins said the CBS TV news program 48 Hours has contacted him about a possible story on DVT.

Is the DVT Threat Overpublicized?

DVT occurs spontaneously mainly among those at risk: people who are elderly, have heart conditions, have had previous blood clots or been in a recent operation. It can occur with anyone in a stationary position for too long, from employees working at their desks to patients involved in surgery.

"I think any of us who’ve practiced medicine for a long time have seen these type of cases," said Victor F. Tapson, an associate professor of medicine in the Division of Pulmonary and Critical Care at Duke University Medical Center in Durham, N.C. However, Tapson noted that when it comes to the effects of DVT, "the clinical studies so far don’t indicate a high amount of fatalities."

Approximately 800,000 of about 5 million people who suffer from DVT are hospitalized in America each year. Since no deaths have to be reported to aviation officials, and some occur days after some flights, nobody knows how many DVT incidents originate on airliners. But there have been efforts made recently.

The Airlines and DVT: What Is Being Done

The lack of consensus from these studies has left U.S. airlines mostly unwilling to address the DVT-flying concern in public. Tapson has been asked to serve on an American Airlines committee, which is addressing the issue. "I haven’t heard too much of change in policy. They’ve not seen any real evidence to link DVT to air travel as such," Tapson said, adding that proof that air travel in and of itself causes DVT is not available. 

"However, for many individuals that have additional risks such as cancer, a previous clot, or recent surgery, flying might lower the threshold for DVT. It does represent a form of immobilization, which is a risk for clotting," he said. "We certainly need more data for firm conclusions."

But Tapson added that unless people are already at risk for DVT, including being obese or having an underlying disease, they shouldn’t be paranoid about being harmed by the condition. "It’s not an issue for the vast majority of people," he said.

Some overseas airlines already consider DVT a risk and tell passengers steps they should take to avoid it. Singapore and Thai airlines, for examples, advise travelers to stretch their arms and legs, drink more water and avoid alcohol.

For passengers with no pre-existing conditions for developing DVT and a flight more than a few hours long, Tapson suggests they try to stand up and stretch their legs some at least once. For those with significant risk factors, he recommends more stretching or walking during the flight and wearing the elastic compression stockings used in a study by Dr. John Scurr. (See "What the Studies Revealed," Page 17.)

Himself a victim of DVT, Brad Perkins agrees that air passengers should get up and move more often to prevent the condition. But he does not see that or any other ideas as a perfect response to DVT. "I’m not an activist on this," said Perkins. "I don’t necessarily blame anyone for this. I understand that they are working on class-action lawsuits, which I don’t plan to encourage.

"I think the solution here is not really clear. I don’t think we know what the answer is."

Tapson echoed that concern and said more can and will be done on DVT and flying. "This is an area that is now being explored in more detail," he said.

Tips for travelers on an extended flight

Here are some reasonable measures that, although not proven to be effective, are inexpensive and safe for passengers without significant risk factors for developing DVT: 

  • Stand up and stretch legs some at least once.
  • Even when a person cannot easily stand, he/she can still flex the calves and change position of the legs periodically, which may help prevent blood stasis.

For those with significant risk factors:

  • Stretch or walk during the flight.
  • Wear elastic compression stockings.
  • Drink plenty of fluids.

What the Studies Revealed

So far, no study on DVT and air travel has linked the two definitively. Major observations done up to now include the following:

  • The May 12, 2001 issue of the British medical journal The Lancet revealed a study where 89 men and 142 women over 50 years old with no history of thromboses took flights lasting more than eight hours. They were assigned randomly into two groups, one wearing elastic compression stockings below their knees and one not. Twelve of the 116 people not wearing the stockings, or 10 percent, developed DVT, while none of the 115 people wearing stockings had it.

    "We conclude that symptomless DVT might occur in up to 10 percent of long-haul airline travelers," the report stated. Symptomless DVT involves the development of small clots, most of which will dissolve with no apparent signs or symptoms. "Wearing of elastic compression stockings during long-haul air travel is associated with a reduction of symptomless DVT." The researchers said they believed the DVT detected in the study was attributable to long-haul air travel.

    Some doctors have argued 10 percent is too high in light of the number of people who fly. For their part, Dr. John Scurr, a consultant vascular surgeon at London’s Middlesex Hospital, and his fellow researchers for the study have acknowledged that their participants’ ages could have increased the risk of thrombosis and that the recruitment method was not ideal. Dr. Scurr also noted that the risk of death from DVT via air travel is very rare.

  • An Oct. 28, 2000, report in The Lancet compared the travel history of 186 individuals with confirmed DVT with 602 patients who were suspected of having DVT (clinical tests later confirmed they did not have the condition). All patients were examined between April 1997 and January 1999 and asked if they had traveled by air, car, bus, train or boat for more than three continuous hours in the last four weeks. The researchers found no association between travelling and increasing the risk of DVT. However, few of the airline passengers surveyed took a trip lasting longer than five hours.
  • In February 2001 Dr. Noritake Hata, director of the Intensive Care Unit at the Nippon Medical School Chiba-Hokusoh hospital in Japan, announced that from May 1998 through December 2000, two passengers had died and another 10 were hospitalized after leaving inbound flights from North America, South America and Europe at Tokyo’s Narita airport. All were considered relatively healthy, although the two who died were elderly women ages 66 and 69. Nevertheless, he did not think the results proved air travel caused the patients’ DVT.

References

  • Davis, R. Economy-class syndrome numbers requested. USA Today Jan. 11, 2001.
  • Demaria, A. Medical report fuels ‘economy-class syndrome’ debate. CNN.com Feb. 13, 2001.
  • Economy class syndrome. Los Angeles Times Jan. 16, 2001.
  • Kraaijenhagen RA, Haverkamp D, Koopman MMW, Prandoni P, Piovella F, Büller H. Travel and the risk of venous thrombosis. Lancet 2000; 356: 1492-93.
  • Scurr, JH, Machin SJ, Bailey-King S, Mackie IJ, McDonald S, Coleridge Smith PD. Frequency and prevention of symptomless deep-vein thrombosis in long-haul flights: a randomised trial. Lancet 2001; 357:1485-89.
  • Trottman, M. International carriers address new threat: coach-class syndrome. Wall Street Journal June 27, 2001.
  • Viking, D. Another Problem for Flying Divers. Undercurrent. January 2001.
  • Woman dies from blood clot after long-haul flight. CNN.com Oct. 23, 2000.

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