SIXTY-year-old Steve was looking forward to see his grandchildren in Duluth, Minnesota. His wife, Marianne, died two years ago, and so he had to travel alone – all the way from Manila to Nagoya, Japan and then to Minnesota. Steve never made it. He apparently died of a deep vein thrombosis (DVT) that reached his lungs. He collapsed in St. Paul/Minneapolis airport after complaining of breathing difficulties due to what has been dubbed “economy class syndrome.” 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.
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. “If 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.
“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.”
There are multiple risk factors for developing blood clots in the leg, according to health authorities. 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 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.
Dr. Walter Fister, whose special interest is on public health and works with the Mount Elizabeth Medical Centre in Singapore, says 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.
“DVTs have 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.
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.
“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,” says Dr. Kahn.
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. Haizal bin Haron Kamar, associate professor in medicine and cardiology at the University of Malaya in Kuala Lumpur.
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 Dr. 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.”
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. “If 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.
“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.”
There are multiple risk factors for developing blood clots in the leg, according to health authorities. 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 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.
Dr. Walter Fister, whose special interest is on public health and works with the Mount Elizabeth Medical Centre in Singapore, says 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.
“DVTs have 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.
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.
“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,” says Dr. Kahn.
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. Haizal bin Haron Kamar, associate professor in medicine and cardiology at the University of Malaya in Kuala Lumpur.
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 Dr. 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.”
