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Updated June 5, 2004

Flight risk: 'the tip of the iceberg'

Economy class syndrome: Cramped seating on lengthy flights is causing passengers to die of embolisms, doctors say

January 13, 2001

Brad Evenson
National Post (posted here with permission.)

Except for one fateful minute, Joan MacKay spent the last 14 hours of her life in the cramped window seat of row 47 on a South African Airways flight from Johannesburg to New York City, without even a trip to the restroom. She passed the hours thinking about her husband, waiting at home in Montreal.

Mrs. MacKay, a vivacious 62-year-old, had traveled to the 1998 International Paralympic Championships as manager of Canada's blind lawn-bowling team. She sat beside two of the team members on the plane. Getting up to stretch her legs would disturb them, so she did not.

A warm August dawn lit the runways at JFK International as the Boeing 747 touched down at last. Mrs. MacKay rose stiffly, walked off the plane to make a connecting flight to Montreal, then collapsed in the jetway. Ross MacKay, an advertising executive, had just purchased a bottle of Champagne and red roses to celebrate her journey when he got the telephone call a short time later from Jamaica Hospital in Queens, N.Y. His wife was dead. "We were in shock," recalls their daughter, Sandra MacKay-Nicoll. "We could not believe it."

Even more confusing was the cause of Mrs. MacKay's death. When Mrs. MacKay-Nicoll called the New York City coroner's office, the pathologist who conducted her mother's autopsy had a few puzzling questions. Did Mrs. MacKay have a history of heart trouble? No; a former champion curler, she was extremely fit. Had she traveled a long distance recently? Yes, from South Africa. By plane. After a brief silence, the doctor muttered, "These airlines are diabolical."

What killed Mrs. MacKay was a blood clot, smaller than a peppercorn. It coagulated in a deep vein behind her left knee as she sat immobile in her seat. When she stood up, a portion broke free and streaked through her heart to an artery in her lung, where it blocked the blood flow. Her heart stopped. The autopsy showed airline staff broke at least half a dozen of her ribs trying to resuscitate her heart.

The death certificate lists the medical cause of Mrs. MacKay's death as pulmonary thromboembolization. But most people would recognize it as "economy class syndrome," a term coined by researchers in 1977 to describe blood clots caused by the cramped seating arrangements on commercial flights.

Once dismissed by airlines as a myth, the number of cases appears to be growing as more people fly and more doctors draw links between air travel and unusual deaths.

This week, doctors in England reported economy class syndrome has killed 30 long-distance air travelers at London's Heathrow Airport over the past three years. "These are people who die as they get off the aircraft," says John Belstead, an accident and emergency consultant at Ashford Hospital, near London's Heathrow Airport. Mr. Belstead said at least one passenger a month dies at the hospital of flight-related blood clots. "We're seeing the tip of the iceberg because we're only seeing the people who die," he says. "There must be a lot more people who have chest pains or shortness of breath, or even more people who get leg cramps."

Last August, three members of the British Olympic team were treated for serious blood clots after arriving in Australia for the Sydney 2000 Games. Dr. David Grosser, the surgeon who diagnosed the blood clots in the officials -- all "very fit, healthy people" -- said he believed as many as 12 members of the 600-strong British Olympic team may have suffered from the condition.

British Airways, concerned about the incidence of cases, has begun issuing information to passengers about how to prevent the condition. The health warnings advise long-haul passengers to wear loose clothing, eat light meals and avoid drinking too much alcohol to lessen the risk of potentially fatal blood clots.

The warnings come amid news the British airline and Qantas, Japan Airlines, Air Canada, Air France and Singapore Airways are being sued by a Melbourne law firm on behalf of more than 800 alleged victims of economy class syndrome, of whom 11 say they incurred blood clots while flying on Air Canada jets. Plaintiffs in the suit by the firm Slater and Gordon include families of 36 people reported to have died of blood clots after taking flights. One major Australian airline, Ansett, is preparing an inflight video about the topic for next week.

This week, Dr. Jack Hirsch, a senior scientist at McMaster University in Hamilton, Ont., said he has decided to conduct a study to investigate the blood chemistry of airline passengers for blood clotting. Dr. Hirsch, a member of the Canadian Medical Hall of Fame, hopes the airlines will donate free flights to aid the research.

"These are measures that are long overdue," says Dr. Russell Rayman, executive director of the U.S. Aerospace Medical Association. "We have known about this condition for a long time, and although it is rare, it is preventable."

However, Dr. Rayman says economy class syndrome is a misnomer, because it is not confined to the back of the aircraft. When Dan Quayle was treated in 1994 for a blood clot that reached his lungs, doctors suspected long plane trips caused the former U.S. vice-president's condition. But Mr. Quayle, who grew up in a wealthy family, probably never sat in economy class in his life. "I think a better name would be travel thrombosis, or immobility thrombosis," says Dr. Rayman, noting bus and car passengers also suffer from the condition.

Dr. Rayman finds the airlines' sudden concern for warning flyers a bit ironic. Several years ago, his association sent a free sample pamphlet, containing information about economy class syndrome and ways to avoid it, to all the world's major airlines to distribute to passengers. "To my knowledge, none of them ever used them," he said this week.

Curiously, there is little research that examines flying and blood clots, and there is no regulatory obligation for airlines to report cases to authorities.

The first report on clotting injuries appeared in 1940. It described a rise in deaths from pulmonary embolism (blockage of circulation in the lung by a breakaway clot from a leg vein) in Londoners forced to sit immobile for long hours in air-raid shelters during the Blitz, when German planes bombed the city during the Second World War.

Pulmonary embolisms and painful leg clots, known as venous thrombosis, have also been reported after long bus trips or even at the movies However, long flights appear to be a particular risk.

Dr. John Homans, a Harvard surgeon, published the first description of a leg clot formed on a flight in 1954. Dr. Homans' patient was a 54-year-old doctor who developed a blood clot in his right calf after flying between Boston and Caracas, a 14-hour journey.

Blood clots typically form when passengers sit immobile for too long, forcing the blood to fight gravity on its flow back to the heart. Slow blood flow can cause a conversion of fibrinogen to fibrin in the bloodstream, which causes a clot, or thrombus.

Some experts believe cabin pressure, dehydration and other factors -- such as taking birth control pills or estrogen replacement therapy -- can add to the risk.

In many cases, a chunk of the clot may travel to the lungs. In others, it may reach the brain, causing a stroke. Most frequently, symptoms range from leg stiffness to heart attack-like pains that send people to hospital. Emergency room doctors almost always ask such patients if they have flown recently.

How serious is the problem? An estimated 650,000 to 700,000 cases of serious blood clots occur each year in North America. The risk of a pulmonary embolism ranges from about one in 50,000 in people younger than 40 to about one in 100 in people over 70 years of age. However, only a few studies have looked at the increased risk with air travel.

In 1997, a military study conducted at Tripler Army Medical Center in Hawaii found 50% of blood clots in patients admitted to the 450-bed acute-care hospital over a four-year period had traveled four hours or longer within the previous 31 days. Similarly, a coroner's study found that 12 of 104 natural deaths at London's Heathrow Airport between 1979 and 1982 were due to pulmonary embolisms. "The relative risk of fatal pulmonary embolism was at least 10-fold greater after travel than before," concludes a 1998 article in the Aerospace Medical Association Journal.

In recent years, aviation specialists have criticized airlines for reducing the "pitch" -- the distance between seats -- and forcing a population of increasingly large travelers into tiny seats.

Dr. Stanley Mohler, director of Aerospace Medicine at Wright State University in Dayton, Ohio, says the standard airline seat is primarily designed to meet crash standards, and is intended for a 170-pound, 5-foot-7-inch tall individual. "A 170-pound adult is becoming a thing of the past as far as an average is concerned," he notes. Once tall or heavy passengers get settled in their seats, they tend not to budge, adds Dr. Mohler. Dr. Mohler notices some companies, such as American Airlines, are increasing the distance between seats, but they deny the measure is for health reasons. A spokesman for American Airlines says the change was made for comfort reasons alone. And in December, a Canadian Transportation Agency report said obese airplane passengers who cannot comfortably fit into a single seat should get a second seat at no extra charge.

More than 50% of the economy class seats on Air Canada boast 33 inches from seat back to seat back, says spokeswoman Laura Cook, which is much better than the 24 inches on some American charter flights and regional commuter aircraft.

However, like most airlines, Air Canada does not warn passengers about the potential danger of blood clots, nor about ways to avoid them. Which angers people like Sandra MacKay-Nicoll. In the months following her mother's death, Mrs. MacKay-Nicoll became obsessed with the chronology of events that day. And she began contacting other victims of economy class syndrome.

"I talked to a lady in Australia who just had her leg amputated," she says. "I talked to a lady in England. I talked to people all over the world." When she confronted South African Airlines, she hit a brick wall. Officials said she had no proof the flight contributed to her mother's death. "It's a business," she says wearily. "They don't want to warn people because if they warn people, they're not going to buy [airline] tickets because they're scared."

Mrs. MacKay-Nicoll thinks her mother would be alive today had she known the dangers of sitting immobile for so long: Even if the airline had suggested flexing her ankles to increase blood circulation in the legs, or perhaps drinking extra water, she might be alive today. Others are not so certain. "No one's ever showed that works," says Dr. Hirsch, one of the world's leading experts on blood clots. "It all makes clinical sense ... but we don't know whether it works. It's very hard to measure."

Dr. Hirsch notes a Dutch study published in The Lancet in October, 2000. The survey of the travel histories of 186 patients with confirmed blood clots and 602 others found no association between traveling by air, car, bus or boat and blood clots. People are as likely to get a blood clot while watching sports on TV, one researcher commented. But Dr. Hirsch thinks the Dutch study was too small to prove anything. Instead, he wants to conduct blood tests on volunteers before and after flights.

"There are now very sensitive blood tests that you can do to measure [blood] coagulation," he says. "The tests are so sensitive that only one in 1,000 people who tested positive would actually get a clot. So if they're negative, it means there's no thrombotic process going on." Dr. Hirsch says the study could be done very quickly if airlines co-operated. He hopes Air Canada and other companies will agree to supply free seats for volunteers. "The media is all very interested in this, but I think the first question we have to ask is, 'Is it real?' " he says. "It may be. It may not be. We should find out."