Deep vein thrombosis and airline travel—the deadly duo - Clinical
Kay BallIn November 2000, a 68-year-old businessman flew from Heathrow Airport in London to Melbourne, Australia. On arrival, he complained of breathing difficulties and was taken to the hospital. He went into a coma and died five days later of complications from a pulmonary embolism. (1) In September 2000, a 28-year-old woman who was an avid skier and lover of active sports collapsed in the airport after a flight from Australia to London. No pulse could be detected. Resuscitation was attempted at the airport and the hospital. She was pronounced dead a few hours later. (2) The cause of death was documented as a pulmonary embolism. In October 2000, a physically fit man collapsed and died of a pulmonary embolism shortly after arriving in London on a flight from Barbados. (3)
In March 2002, a 57-year-old woman flew first-class from Miami to London after spending her wedding anniversary in the United States. After the six and one-half hour flight, she complained of breathing problems. She was rushed to the hospital and died one day later of bilateral pulmonary embolism from deep vein thrombosis (DVT). Blood clots had formed in her legs, broken loose, and lodged in her lungs, causing death. The woman had a history of a blood clot 20 years earlier after a surgical procedure, and she also was on hormone replacement therapy. (4) These are only a few of the many documented deaths from pulmonary embolism caused by DVT after airplane travel.
Air travel has become the most popular mode of long-distance travel in the United States and abroad. Figures published by the International Air Transport Association in 1998 suggest an ever-increasing rise in the number of airline passengers--from 1.4 billion in 1997 to 1.5 billion in 1998 with a prediction of two billion airline travelers by 2003. (5)
Given these statistics, it is important to consider the physical effects of traveling long distances by airplane. Approximately 2,000 Americans died from travel-related DVT strokes in 1999. (6) Newspaper headlines, such as "Long Flights Can Cause Blood Clots, Group Warns," "Airlines Sued Over Blood Clots," and "International Carriers Address New Threat: Coach-Class Syndrome," highlight a growing concern about the formation of fatal blood clots after long airline flights as a public health problem. (7)
International airports and hospitals near airports report alarming statistics.
* As many as 400 people per year may be arriving at Sydney Airport in Australia suffering from DVT. (8)
* At least one long-distance airplane passenger dies every month from a blood clot within minutes of landing at Heathrow Airport. (9)
* A nurse from a hospital near a British airport stated that the hospital receives approximately 10 patients per month who are experiencing problems related to air travel. (10)
* Physicians at Ashford Hospital, London, which treats patients who arrive at Heathrow Airport, say that more than 2,000 people die from flight-related DVT every year in Britain. (11)
ANATOMY
To fully understand the formation of DVT, it is important to comprehend the anatomy and functioning of the circulatory system. Blood flow provides the principal means of transporting metabolic necessities throughout the body and removing wastes from the body. Oxygen-rich blood from the lungs is pumped through the body by the heart via a network of arteries. When the blood reaches an organ or tissue, it is diffused through a series of capillaries for oxygenation. The waste product, carbon dioxide, then is carried away from the organ or tissue in reverse through a network of veins that return the blood to the heart for reoxygenation and release of the waste carbon dioxide.
The pressure propelling the blood through the arteries originates from the heart beat but is dissipated when the blood reaches the capillaries. The pressure to return the blood to the heart through the veins is much less vigorous and hampered by gravity. To assist in maintaining an adequate blood flow in the veins, the main leg veins are positioned deep inside the leg muscles and contain a series of valves. With the help of leg muscle movements, the valves in the veins open and close to "stair step" the blood forward. The valves open during the heart beat and close during the resting phase. These valves help to advance the blood through the venous network toward the heart while preventing the back flow of blood in the lower legs.
The blood flowing through the deepest veins in the calf or thigh flows relatively slowly. Inactivity complicates this slow flow because the leg muscles are not assisting with the movement of the blood, leading to the improper closure of the valves in the veins. When the valves do not close properly, venous back flow occurs, leading to swollen veins. Within these expanded veins, blood is allowed to stagnate and coagulate, forming clots on the vessel walls. A DVT can be present without signs or symptoms but may cause swelling or pain, particularly when the foot is flexed sharply upward.
A DVT is not dangerous by itself, but complications can occur when it breaks away and becomes an embolus. Clots can detach days and even weeks after formation. When a DVT forms, it moves so slowly that it can form a solid clot that can become wedged in a vein. If the embolus reaches a blood vessel it cannot flow through, a blockage occurs. The consequence of this obstruction is called an embolism. The most serious blockage is a pulmonary embolism that occurs when the embolus reaches the pulmonary system and cannot pass. Chest pain and breathing difficulty may occur immediately. Death sometimes occurs from respiratory failure. If the clot does not detach, it can cause a venous thrombosis. This may require surgery (ie, embolectomy) to remove the clot or even amputation of a limb.
HISTORY OF DVT LINKED WITH LONG-DISTANCE AIR TRAVEL IN THE LITERATURE
In 1940, the Lancet published an article that documented a marked increase in the monthly incidence of pulmonary embolism among people who spent prolonged periods in the cramped quarters of London air-raid shelters. (12) Fourteen years later, immobility from long-distance airplane travel was reported to be directly associated with venous thromboembolism. (13) The link between DVT incidence and long-distance airplane flights had been documented; however, this issue did not appear to raise significant concern until more than two decades later.
In 1977, two British researchers identified eight patients with pulmonary embolism from a cohort of 182 patients. The embolisms had developed soon after prolonged travel in the coach-class section of an airplane, so the researchers coined the term economy class syndrome. Today, economy class syndrome has been deemed an inappropriate term because deaths also have resulted for passengers sitting in the first-and business-class sections of airplanes. (14)
In 1986, a researcher found that 18% of sudden deaths among long-distance travelers landing at Heathrow airport during a three-year period were caused by pulmonary embolism. (15) Twelve years later, two other researchers reviewed medical records of 134 patients with pulmonary embolism and found that air travel for four or more hours within the preceding 31 days was the most common risk factor for venous thromboembolism (ie, in 50% of the cases). (16) By the 1990s, a definite link had been made between air travel and clot formation, and the media began publishing articles about untimely deaths caused by DVT.
In 2001, researchers concluded that airplane travel is a definite risk factor for pulmonary embolism. These researchers found that 56 of the 135.3 million passengers who arrived at Charles de Gaulle Airport in Paris during an 86-month period experienced pulmonary embolism at the end of or immediately after their flight. They found that the frequency of pulmonary embolism among those who traveled more than 5,000 km was 150 times higher than the frequency among those who traveled less than 5,000 km. (17)
In 2001, a surgeon at Middlesex Hospital, London, and his associates published the results of a controlled study that was conducted to determine whether people flying long distances developed clots in their legs. More than 200 participants who were older than 50 years of age and would be traveling coach class for two sectors of at least eight hours duration within a six-week period were included in the study. Participants were assigned randomly to either a group who wore graduated elastic compression stockings that squeeze the leg to promote blood flow through the deep veins and prevent the deeper veins from enlarging during long periods of inactivity or a group who did not wear compression stockings. In 12 of the 116 passengers who did not wear compression stockings, the researchers were able to detect symptomless small clots using a very sensitive technique called duplex ultrasound examination that assesses the deep and superficial veins. Researchers were unable to detect any clots in the deep veins of passengers who wore compression stockings, showing that compression stockings are effective in the prevention of clot development during long airplane trips. Their conclusions also reflected that symptomless DVTs might occur in up to 10% of long-distance airplane travelers. (18)
THE AIRPLANE ENVIRONMENT
Air travel is relatively safe and comfortable, but there are environmental concerns and physiological stresses that must be addressed. The aircraft cabin environment at cruising altitude is very different from any ground environment. Differences include
* lower barometric pressure and partial pressure of oxygen,
* sustained periods of noise and vibration exposure,
* turbulence,
* variable air circulation and lower air quality,
* temperature changes,
* lower humidity (ie, 2% compared to 50% on the ground),
* disruption of the body's circadian rhythms,
* sustained periods of postural immobility, and
* a varying exposure to low level radiation.
There is a greater likelihood for a condition to develop in flight than when using other modes of transportation because the body responds directly to these significant changes in the aircraft environment. Reduced air pressure can lead to abdominal distension acting against the venous blood return from the legs. The reduced oxygen and pressure leads to increased blood clotting tendencies. Low humidity affects the body fluid content, and excessive consumption of alcohol and coffee in flight can lead to dehydration. Hemoconcentration from decreased fluid intake coupled with water loss in a dry cabin adds to the problem of dehydration and clot formation. Passenger mobility on airplanes is discouraged, which can lead to complications such as clot formation. Cramped seating causes orthostatic stress, and the edge of the seat can compress the popliteal vein, which can lead to clot development. The business-class leg rest can put undue pressure on the calves. The increasing duration of nonstop flights also has contributed to the potential for risk. (19)
SIGNS AND RISKS FACTORS
Signs of DVT formation include
* sudden swelling in the lower extremities,
* enlargement of the superficial veins of the legs (ie, surface veins may be more visible through the skin),
* reddish-blue discoloration of the skin,
* skin that is warm to the touch around the area of the DVT, and
* pain or tenderness in the leg (eg, when the foot is flexed upward).
The signs of a pulmonary embolism include
* instant sweating,
* sudden pallor,
* persistent chest pain, and
* breathlessness.
Many studies have noted that 70% to 90% of those who experienced pulmonary embolism have associated conditions or risk factors, (20) including
* cancer,
* obesity,
* varicose veins, and
* family history (ie, inherited impairment of blood clotting mechanisms). (21)
Deep vein thrombosis formation and pulmonary embolism can occur in anyone, however, regardless of age, gender, and race, including in those without previously diagnosed venous problems.
Factors that lead to some degree of increased clotting tendency may affect 20% of the total population. (22) For example, stress and the fear of flying could be a key factor in causing DVT. Anxiety causes a surge of the hormone adrenaline, which makes blood more likely to clot and causes vessels to constrict. This may be the kick-start needed to form a clot. (23)
Pregnancy also can cause higher risks for untoward effects from long-distance airplane trips. During pregnancy, hormonal changes cause vein walls to relax and stretch. Blood flowing to and from the uterus puts added pressure on the veins. The baby's weight puts more stress on the mother's leg muscles and vein walls. Twenty percent of women who are pregnant develop varicose veins, and, if left untreated, 50% will suffer from varicosities for the rest of their lives. When the back flow of blood is beginning to occur in a pregnant woman's body, the smaller veins near the surface of the skin will become visibly knotted and look like spider webs (ie, spider veins). The first signs of potential clot formation include swollen, aching feet and legs with edema and increasing fluid retention. (24) A list of factors affecting clotting tendency is found in Table 1.
DIAGNOSIS
An untreated pulmonary embolism can kill up to one in 10 people. (25) Immediate identification and treatment, therefore, is mandatory. One in four people who develop blood clots after airplane travel are misdiagnosed by physicians or sent away with bad advice, such as orders to seek physical therapy or simply take a hot bath. (26) Many days can pass before DVT symptoms appear, so recent air flight passengers usually end up consulting their general practitioner instead of being taken to hospitals close to the airport that are more alert to this condition and can provide immediate treatment.
The accepted practice for immediate identification of a DVT involves conducting an ultrasound scan that will detect clots. The ultrasound will show impaired blood flow, indicating a clot. Blood tests also can give a good indication of a thrombosis. One such test measures the levels of a by-product of the clotting material D-dimer.
More recently, magnetic resonance direct thrombosis imaging, which can visualize clots within 12 minutes, has been used. Radio waves in strong magnetic fields generate images of the body's organs and tissues so that the actual blockage can be detected. This diagnostic test is noninvasive, quick, and reliable. (27)
If the patient dies, usually from a pulmonary embolism, identification of DVT may be made during the autopsy. Up to 50% of all people with DVT and/or pulmonary embolism will show no signs or symptoms at all, however, and only one in three cases of suspected DVT subsequently is confirmed during an autopsy. (28)
TREATMENT AND PREVENTION
The main objectives of a treatment plan are to dissolve the clot and prevent other clots from forming. Anticoagulative medications are administered that will thin the blood and allow it to flow more easily. For example, high doses of heparin may be given by injection, or warfarin may be given by tablet. With any anticoagulative therapy, the patient needs to have regular blood tests to make sure the right dose is being given and the patient is not at risk for hemorrhage.
Prevention is paramount during long-distance airplane travel. Preventive measures include (29)
* avoiding alcohol and caffeine before and during the flight;
* avoiding constrictive clothing;
* avoiding leg crossing;
* changing positions frequently while seated;
* moving around in the plane seat and cabin as much as possible (eg, doing isometric calf exercises by flexing and rotating the ankles and wiggling the toes for a few minutes every half hour to prevent blood from pooling in the feet);
* not ingesting sleeping pills;
* not smoking;
* requesting bulkhead seating where there is more room to stretch the legs;
* staying well-hydrated with water or noncaffeinated soft drinks or juices;
* taking only short naps, unless a normal sleeping position can be attained, such as in the first-class recliner seats; and
* wearing compression stockings.
Taking a low-dose aspirin to thin the blood also may help prevent DVT formation; however, this practice still is being examined for effectiveness.
Staying hydrated. Staying well-hydrated is important to diminish the possibility of DVT formation during a long airplane trip. Passengers should drink something each hour on a flight. Unfortunately, airline policies usually do not mandate hourly beverage service in coach class. A Wall Street Journal article noted that during a 10-hour flight from London to Dallas, beverages were offered only six times in the coach section. During a nine-hour flight heading in the opposite direction, business-class passengers received almost constant beverage service, about every 20 minutes. On this same flight, coach passengers were offered beverages only five times during the nine hours. (30)
Use of compression stockings. Using appropriate compression stockings also can help prevent formation of DVT. Graduated compression medical hosiery has been used for years as preventive and therapeutic measures for DVT, edema, varicose veins, and phlebitis. These stockings apply maximum pressure at the ankle with decreasing pressure up the length of the leg (Figure 1). Compression on the leg surface forces the blood to flow from the small surface vessels into the larger, deep venous system. This compression also supports faulty venous valves by preventing back-flow of blood and the subsequent formation of clots. Compression stockings reverse the underlying pathology and restore the function of pumping mechanisms in the legs. Compression stockings should be used as a preventive measure and for the maintenance of an edema-free state, not for edema evacuation.
[FIGURE 1 OMITTED]
The compression level of the stockings is defined in millimeters of mercury (mm Hg). To prevent DVT, the stocking must be rated at least 15 mm Hg to 20 mm Hg compression. There are a number of compression classification systems, including the international system and the well-known German system. The German system often must be followed when reimbursement by health insurance companies is requested. This system includes three classes:
* class I--18.05 mm Hg to 21.05 mm Hg,
* class II--23.31 mm Hg to 32.33 mm Hg, and
* class III--33.83 mm Hg to 45.86 mm Hg.
The measurements within each class measure tolerance. This means a class I stocking can have a minimum compression of 18.05 mm Hg but a maximum of 21.05 mm Hg at the ankle. Tolerance always is measured at the ankle. The compression must decrease gradually from the ankle in the direction of the thigh. Table 2 describes different compression levels and their medical indications.
LEGAL CONSIDERATIONS
Recently, a group of attorneys won the right to pursue a class action lawsuit involving DVT victims and their family members in England and Wales. (31) The high court ruling granted permission for action by relatives of 50 passengers who died after suffering DVT, and as many as 250 victims who survived. (32) This class action suit will serve as a test case for others. The case will hinge on whether the claimants can prove that DVTs were caused by the cramped aircraft seating conditions and that the airlines were aware of the risks and did not take reasonable action to mitigate the dangers or warn passengers. (33) As many as 30 airlines face accusations by nearly 300 claimants that the airlines knew of the risk of DVT in 1968 and have done nothing to prevent them. (34) In Australia, one law firm has filed more than 1,000 DVT claims against six airlines. (35)
Lawsuits will continue to surface, but the causal link between flying and DVT formation must be demonstrated clearly. All lawsuits need to establish liability against the airlines. Any claim will face many hurdles to establish liability. Key issues to resolve include the following questions. (36)
* What specifically about airline travel causes DVT (eg, lack of space, lack of movement, reduced air pressure)?
* Can a causal link be established clearly between the harm suffered and the apparent reason for it?
* Can it be determined that the airline knew about the problem, and if so, could the airline have done more to prevent or warn travelers of the risk?
* Is there a time limit in which the claimant must make the claim?
* In which country or jurisdiction should potential claimants bring a claim?
MAKING THE SKIES SAFER
According to the World Health Organization, airlines tend to focus more on aircraft safety and less on passenger health. (37) This can be remedied if airlines are willing to redesign cabin seating. Seat dimensions should be explored considering passenger health, size, and allowance for seat-space reductions when the seat in front is reclined. Cabin service procedures also need to provide for more beverage accessibility and service on long flights.
A new generation of an "intelligent" airline seat that can warn passengers when they are at risk of developing DVT recently has been introduced. This special seat alerts the traveler when he or she has been sitting in one position for too long. The chair's upholstery contains movement sensing devices that provide an alert when too much or too little movement is detected. (38)
Another recommendation is that a health advisory be announced immediately before takeoff along with the safety briefing. The health advisory should be backed by a standardized written health reminder placed in the seat-back pocket along with the safety card. Further recommendations include offering passengers flight compression stockings and low-dose aspirin as preventive measures.
Some airlines have responded by printing DVT warnings on airline tickets. British Airways now offers health advice in ticket wallets, on the Internet, through on-board videos, via the telephone, and in its in-flight magazine. (39) Qantas Airways sends an "Important Notice Regarding Your Health and Wellbeing Inflight" along with the airline ticket information to help passengers understand the risks of long airplane trips. In addition, Qantas has put health information on its web site at http://www.qantas.com.au/info/flying/inTheAir/yourHealth Inflight to provide a resource and reference for passengers. They also describe and illustrate suggested exercises to prevent DVT during long airplane rides (Table 3).
Support groups focused on passenger health during airplane trips have formed. The Aviation Health Organization is a nonprofit organization that promotes the health and well-being of airline passengers worldwide. Information about this organization is available online at http://www.aviation-health.org. A passenger support group called Victims of Air-Related DVT Association is chaired by a woman whose daughter died in 2000 after a flight from Australia to London. One of the many suggestions from this group includes the discontinuation of the term economy class syndrome in favor of the term flight-related D VT or traveler's thrombosis.
The news media has helped bring this risk to the global forefront. The media can help the public understand the link between DVT and long-distance airplane travel and the preventive measures needed to minimize this risk by providing balanced and accurate information. Written messages, videotaped programs, and news shows can help to fill the knowledge deficiency gap with factual information.
Today, DVT formation during long airplane trips has become a serious medical concern. Even though this condition is relatively rare, it has been shown to affect one or two people in every thousand. Research continues to note the link between long-distance flights, DVT, and death--a medical malady that can be prevented.
Table 1
FACTORS AFFECTING CLOTTING TENDENCY (1)
* Airplane travel longer than four hours
* Any condition that could be complicated by the expansion of body gases associated with airplane travel
* Being more than 6 ft tall or less than 5 ft tall
* Being older than 40 years of age
* Certain blood disorders
* Certain cardiovascular diseases or insufficiencies
* Depletion of body fluids causing increased blood viscosity
* Immobility due to broken leg or recent leg injuries
* Immobilization of the limb for a day or more (eg, due to use of splints or appliances)
* Paralysis or immobility
* Pregnancy
* Recent surgery
* Smoking
* Stress and fear of flying
* Taking sleeping pills during long-distance airline travel (2)
* Use of oral contraception or hormone replacement therapy
NOTE
(1.) "DVT facts file," Aviation Health Institute, http://www.aviation-health.org/dvtfacts.html (accessed 12 Dec 2002); Select Committee Appointed to Consider Science and Technology, Airline Travel and Health (Geneva: World Health Organization, Nov 15, 2000).
(2.) D Derbyshire, "Sleeping pills may increase the risk on long-haul flights," Doily Telegraph (London) (Jan 11, 2001) http://www.newsdirectory.com/go/?f=&r=eu&u=www.telegraph.co.uk (accessed 27 Dec 2002).
Table 2
COMPRESSION LEVELS AND MEDICAL INDICATIONS (1)
Compression Medical indications
8 mm Hg to 15 mm Hg Fluid retention, fatigue or pain in the legs and
feet, mild edema, spider veins, mild
varicosities, preventive measure for at-risk
patients or those with a family history of
varicose veins
15 mm Hg to 20 mm Hg Chronic edema, varicose veins, advanced
varicose veins during pregnancy, phlebitis,
thrombosis, chronic venous insufficiency,
deep vein thrombosis
20 mm Hg to 30 mm Hg Advanced varicosities, advanced venous
thrombosis, ulceration and inflammation of
the lower legs, severe phlebitis, acute edema,
acute venous insufficiency, lymphedema,
thrombophlebitis
NOTE
(1.) Graduated Compression Maternity Hosiery (Hillsborough, NJ: Ames
Walker Support Hosiery, 2001).
Table 3 EXERCISES THAT CAN BE PERFORMED DURING AIRPLANE TRAVEL
Ankle circles
Lift both feet off the floor. Draw a circle with your toes, simultaneously moving one foot clockwise and the other foot counterclockwise for 15 seconds. Reverse the circles for another 15 seconds and repeat if desired.
Foot pumps
Start with both heels on the floor and point your feet upward as high as you can. Put both feet fiat on the floor. Lift your heels high, keeping the balls of the feet on the floor.
Knee lifts
Lift one leg with the knee bent while contracting the thigh muscle. Alternate legs and repeat 20 to 30 times per leg.
Knee to chest
Bend forward slightly, clasp your hands around your left knee, and hug your knee to your chest. Hold the stretch for 15 seconds. Keeping your hands around the knee, slowly lower it. Alternate legs and repeat 10 times.
Shoulder roll
Hunch your shoulders forward, then upward, then backward, then downward, using a gentle circular motion.
Neck roll
With shoulders relaxed, drop your ear to your shoulder and gently roll the neck forward and back, holding each position for five seconds and repeat five times.
Forward flex
With both feet on the floor and the stomach held in, slowly bend forward and walk your hands down the front of your legs toward your ankles. Hold the stretch for 15 seconds then slowly sit back.
(Adapted from "Your Health Inflight," http://www.qantas.com.au/info/flying/inTheAir/yourHealthInflight, with permission from Qantas Airways, Mascot, New South Wales, Australia)
NOTES
(1.) "68-year-old dies after plane trip to Australia," Thomas Crosby Media (Jan 7, 2001) http://archives.tcm.ie/ breakingnews/2001/01/07/story1026.asp (accessed 26 Dec 2002).
(2.) M Trottman, "Fear of Flying: International Carriers Address New Threat: Coach-class Syndrome," The Wall Street Journal, 27 June 2001, A1.
(3.) B Marsh, "DVT action could hit the airlines for millions," Aviation Health Institute (Feb 1, 2002) http://www.aviation-health.org/ Newspage.asp?ArtID=83 (accessed 27 Dec 2002).
(4.) D Derbyshire, "DVT kills first class passenger," Daily Telegraph (London) (March 21, 2002) http://www.telegraph.co.uk/travel/ main.jhtml?xml=%2Ftravel%2F2002%2F03%2F20%2Fetnewsdvt21.xml (accessed 26 Dec 2002).
(5.) G Jantet "Commentary," Venous Digest 6 (February 1999) http://www.venousdigest.com/Past_Issues/1999/issue602/index.html (accessed 26 Dec 2002).
(6.) The Risks and Remedies for "Economy Class Syndrome" Deep Vein Thrombosis (Hillsborough, NJ: Ames Walker Support Hosiery, 2000).
(7.) J E Ansell, "Air travel and venous thromboembolism--Is the evidence in?" The New England Journal of Medicine 345 (Sept 13, 2001) 828-829; Trottman, "Fear of Flying: International Carriers Address New Threat: Coach-class Syndrome."
(8.) "Surgeon Backs Flight Fears of Blood Clots," The Times (London) 11 Jan 2001, sec 4M, 10.
(9.) D Derbyshire, "Long flights cost 2,000 lives a year," Daily Telegraph (London) (Jan 10, 2001) http://www.newsdirectory.com/go/?f=&r=eu&u=www.telegraph.co.uk (accessed 27 Dec 2002).
(10.) "Action call after long-flight death," BBC News (Jan 8, 2001) http://news.bbc.co.uk/1/hi/wales/1105275.stm (accessed 13 Dec 2002).
(11.) "Deep vein thrombosis/travellers' syndrome," Can I Claim? http://www.caniclaim.com (accessed 13 Dec 2002).
(12.) Select Committee Appointed to Consider Science and Technology, Fifth Report: Airline Travel and Health (London: The United Kingdom Parliament, Nov 15, 2000) http://www.parliament.the-stationeryoffice.co.uk/ pa/ld199900/ldselect/ldsctech/121/12102.htm
(13.) Ansell, "Air travel and venous thromboembolism--Is the evidence in?"
(14.) I S Symington, B H Stack, "Pulmonary thromboembolism after travel," British Journal of Diseases of the Chest 71 (April 1977) 138-140.
(15.) R Sarvesvaran, "Sudden natural deaths associated with commercial air travel," Medicine, Science, and the Law 26 (January 1986) 35-38.
(16.) A Mercer, J D Brown, "Venous thromboembolism associated with air travel: A report of 33 patients," Aviation, Space, and Environmental Medicine 69 (February 1998) 154-157.
(17.) F Lapostolle et al, "Severe pulmonary embolism associated with air travel," The New England Journal of Medicine 345 (Sept 13, 2001) 779-783.
(18.) J Scurr et al, "Frequency and prevention of symptomless deep-vein thrombosis in long-haul flight: A randomised trial," Lancet 357 (May 12, 2001) 1485-1489.
(19.) "DVT fact file," Aviation Health Institute, http://www.aviationhealth.org/dvtfacts.html (accessed 13 Dec 2002).
(20.) Ansell, "Air travel and venous thromboembolism--Is the evidence in?"
(21.) "DVT fact file"; Select Committee Appointed to Consider Science and Technology, Fifth Report: Airline Travel and Health.
(22.) Select Committee Appointed to Consider Science and Technology, Fifth Report: Airline Travel and Health.
(23.) B Marsh, "Fears of flying `could increase DVT risk,'" Aviation Health Institute (Jan 24, 2002) http://www.aviation-health.org/Newspage.asp?ArtID=70 (accessed 27 Dec 2002).
(24.) Graduated Compression Maternity Hosiery (Hillsborough, NJ: Ames Walker Support Hosiery, 2001).
(25.) "Deep vein thrombosis," BBC News (May 11, 2001) http://news.bbc.co.uk/1/hi/ health/medical_notes/c-d/986364.stm (accessed 13 Dec 2002).
(26.) J Chapman, J Mills, "Doctors deadly ignorance on DVT," Aviation Health Institute (March 12, 2002) http://www.aviation-health.org/Newspage.asp?ArtID=88 (accessed 27 Dec 2002).
(27.) D Derbyshire, "New DVT test can identify travellers most at risk," Daily Telegraph (London) (Jan 15, 2002) http://www.newsdirectory.com/go/?f=&r=eu&u=www.telegraph.co.uk (accessed 27 Dec 2002).
(28.) Select Committee Appointed to Consider Science and Technology, Fifth Report: Airline Travel and Health.
(29.) "DVT fact file."
(30.) Trottman, "Fear of Flying: International Carriers Address New Threat: Coach-class Syndrome."
(31.) Marsh, "DVT action could hit the airlines for millions."
(32.) Ibid.
(33.) "Deep vein thrombosis/travellers' syndrome."
(34.) V Fletcher, "Airline braced for 200M [pounds sterling] DVT payout battle," Aviation Health Institute (Feb 1, 2002) http://www.aviation-health.org/Newspage.asp?ArtID=77 (accessed 27 Dec 2002).
(35.) The Risks and Remedies for "Economy Class Syndrome" Deep Vein Thrombosis.
(36.) "Deep vein thrombosis/travellers' syndrome."
(37.) Select Committee Appointed to Consider Science and Technology, Fifth Report: Airline Travel and Health.
(38.) B Marsh, "Airline seat that warns if you are at risk of DVT," Aviation Health Institute (July 20, 2002) http://www.aviation-health.org/Newspage.asp?ArtID=131 (accessed 27 Dec 2002).
(39.) M Townsend, "BA hauls in flyers to check DVT risk," Aviation Health Institute (April 14, 2002) http://www.aviation-health.org/Newspage.asp?ArtID=97 (accessed 27 Dec 2002).
Kay Ball, RN, BSN, MSA, CNOR, FAAN, is an independent perioperative nurse educator and consultant, Lewis Center, Ohio.
COPYRIGHT 2003 Association of Operating Room Nurses, Inc.
COPYRIGHT 2003 Gale Group