Traveller's thrombosis
Hot topic (24 February 2004)
Hot topics provide a short list of up-to-date references, books/reports/videos held by the BMA Library, and links to other relevant web resources, on a current news topic. Literature searches have been carried out using the Library's MEDLINE Plus service. Results cover the last five years and have been limited to items held in BMA Library stock. References listed may be ordered via the Library's document delivery service for members. If you would like to suggest an area to be included as a future "hot topic" please email Clare Aitken Sub-Librarian (Development).
- References from MEDLINE
- File for download into reference manager software
- Request free email updates on this topic (members only)
- Books/reports held by the BMA library
- Additional web resources
Recent references from MEDLINE
1. Aerospace Medical Association. Medical Guidelines for Airline Travel, 2nd ed. Aviation Space & Environmental Medicine 2003; 74:A1-19.
2. Cesarone MR et al. The LONFLIT4-Concorde--Sigvaris Traveno Stockings in Long Flights (EcoTraS) Study: a randomized trial. Angiology 2003; 54:1-9.
Abstract: The LONFLIT1/2 studies have established that in high-risk subjects after long ( > 10 hours) flights the incidence of deep venous thrombosis (DVT) may be between 4% and 6%. The LONFLIT4 study was aimed at evaluating the control of edema and DVT prevention in low-medium-risk subjects. In this study prophylaxis of edema with specific travel stockings was evaluated in 2 separate studies involving flights lasting 7 hours and 10-12 hours. Part I. Subjects at low-medium risk for DVT were contacted; 55 subjects were excluded for several nonmedical, travel-related problems or inconvenient evaluation time; the remaining 211 were randomized into 2 groups to evaluate prophylaxis with elastic stockings in 7-8-hour, long-haul flights. The control group had no prophylaxis; the treatment group used below-knee, Sigvaris Traveno elastic stockings (Ganzoni, Switzerland, producing 12-18 mm Hg of pressure at the ankle). Color duplex scanning was used to evaluate the possible presence of DVT; edema/swelling were evaluated with a composite score including the presence of edema (with an edema tester), variations in ankle circumference and leg volumetry, subjective swelling, and discomfort (scale ranging from 0 to 10). Results: Of the 103 included subjects in the stockings group and 108 in the control group (total 211), 195 subjects completed the study. Dropouts (16) were due to low compliance or traveling and connection problems. Age, sex distribution, and risk factors distributions were comparable in the 2 groups. Stockings Group: Of 97 subjects none had DVT or superficial thromboses. Control Group: Of 98 subjects none had thrombosis. The level of edema at inclusion was comparable in the 2 groups of subjects. After flights there was an average score of 6.4 (1.3) in the control group, while in the stockings group the score was on average 2.4 (SD 1), 2.6 times lower than in the control group (p < 0.05). In the control group 83% of the subjects had an evident increase in ankle circumference and volume that was visible at inspection and associated with discomfort. The control of edema with stockings was clear, considering both parametric data (circumference and volume) and nonparametric (analogue scale lines) measurements. Part II. In this part of the study 200 subjects at low-medium risk for DVT were contacted; 35 subjects were excluded for several nonmedical, travel-related problems or inconvenient evaluation time; the remaining 165 were randomized into 2 groups to evaluate prevention in flights lasting between 11 and 12 hours. The control group had no prophylaxis; the treatment group used Traveno stockings. Of the 83 included subjects in the stockings group and 82 in the control group (total 165), 146 subjects completed the study. Dropouts were due to low compliance or connection problems. Age/sex distribution were comparable. Of 75 subjects completing the study in the stockings group and 71 in the control group, none had thrombosis. The average level of edema at inclusion was comparable in the 2 groups (1.1). After the flight there was a score of 8.9 (2) in controls; in the stockings group the score was 2.56 (1.3) (p < 0.05). The control of edema and swelling with stockings even after 11 hours of flight was clear, considering both parametric (circumference, volume) and nonparametric (analogue scale lines) measurements. The tolerability of the stockings was very good and there were no complaints or side effects. In conclusion Sigvaris Traveno stockings are very effective in controlling edema in long-haul flights
3. Cesarone MR et al. The LONFLIT4--Concorde Deep Venous Thrombosis and Edema Study: prevention with travel stockings. Angiology 2003; 54:143-154.
Abstract: BACKGROUND: The LONFLIT1+2 studies have established that in high risk subjects after long flights (> 10 hours) the incidence of deep venous thrombosis (DVT) is between 4% and 6%. The LONFLIT4 study was designed to evaluate the control of edema and DVT in low-medium risk subjects. The aim of this study was to evaluate edema and its control with specific stockings (ankle pressure between 20 and 30 mm Hg) in long-haul flights. The first part of the study included flights lasting 7-8 hours and the second part included flights lasting 11-12 hours. Ultrasound scans were used to assess thrombosis before and after the flights and a composite edema score was used to evaluate edema and swelling. A group of patients with microangiopathy associated to edema (diabetes, venous hypertension, anti-hypertensive treatment) were also included to evaluate the preventive effects of stockings during flight. Part I: DVT evaluation: Of the 74 subjects in the stocking group and 76 in the control group (150), 144 completed the study. Dropouts were due to low compliance or traveling and connection problems. Age and gender distribution were comparable in the 3 groups as was risk factor distribution. In this part of the study there were no DVTs. Edema Evaluation: The level of edema at inclusion was comparable in the two groups of subjects. After the flight there was an average score of 6.9 (1) in the control group. In the stocking group, the score was on average 2.3 (1), three times lower than in the control group (p < 0.05). Part II: DVT evaluation: Of the 66 included subjects in the stocking group and 68 in the control group (134), 132 completed the study. Dropouts were due to low compliance or connection problems. Age and gender distribution were comparable in the two groups. In the stocking group no DVT was observed. In the control group, 2 subjects had a popliteal DVT and 2 subjects had superficial venous thrombosis (SVT); in total 4 subjects (6%) in the control group had a thrombotic event; the incidence of DVT was 3%. The difference (p < 0.02) is significant. EDEMA EVALUATION: The composite edema score at inclusion was comparable in the two groups. After the flight there was a score of 7.94 (2) in the control group, while in the treatment group the score was 3.3 (1.2). MICROANGIOPATHY STUDY: In all these subjects, the level of edema was very high in the control group and significantly lower in the compression stocking group. Stockings are effective in controlling edema during flights even in subjects with microangiopathy and edema. Compression was well tolerated in normal subjects and in patients. CONCLUSION: The Kendall Travel Socks (Tyco Healthcare, Mansfield, MA, USA) which provide 20-30 mm Hg pressure at the ankle, are effective in controlling edema and reducing the incidence of DVT in both low-medium-risk subjects and in patients with microangiopathy and edema in long-haul flights (7-11 hours)
4. Cesarone MR et al. The LONFLIT4-Venoruton Study: a randomized trial--prophylaxis of flight-edema in venous patients. Angiology 2003; 54:137-142.
Abstract: The aim of this independent study was to evaluate the protective effects, on the development of flight edema, of Venoruton. The study included patients with venous disease traveling in economy in long-haul flights (9 hours). Edema is a relevant aspect of long-haul flights affecting both patients with venous disease and normal subjects. Microcirculatory variations during flights cause a microangiopathy and biochemical and coagulation alterations. This condition may be defined as flight microangiopathy. A group of 203 subjects with chronic venous disease (uncomplicated varicose veins) at low-medium risk for DVT were contacted; 43 subjects were excluded for several nonmedical, travel-related problems or inconvenient evaluation time; the remaining 160 were randomized, after informed consent, into 2 groups to evaluate 2 prophylaxes in 7-8-hour, long-haul flights: The treatment group received Venoruton (hydroxyethyl rutosides) 1 g twice daily for 3 days (2 days before the flight and the day of the flight). The control group received comparable placebo. The edema score was based on the edema tester, ankle circumference, volume measurements, subjective swelling, and discomfort score. Items 1, 4, and 5 are based on an analogue scale line (1 to 10) directly defined by the subjects before and after the flights. Of the 160 included subjects 139 completed the study. Dropouts (21) were due to poor compliance, traveling, and/or connection problems (11 in the control group, 10 in the treatment group). Age and sex distribution were comparable in the 2 groups as were risk factors distributions. The level of edema at inclusion was comparable in the 2 groups of subjects. After the flight there was an average score of 7.2 (sd 2) in the control group, while in the Venoruton group the score was on average 3.2. (sd 1.1) (p < 0.05), 2.25 times lower than in the control group (p < 0.05). In the control group 89% of the subjects had an evident increase in ankle circumference and volume, which was clearly visible at inspection and associated with discomfort. In the Venoruton group edema was clearly present in 12% of subjects (associated with discomfort between 5 and 7 on the analogue scale line) and it was mild-moderate, not associated with symptoms (pain, discomfort between 2 and 4 on the analogue scale line). Therefore, the control of flight edema with Venoruton was clear both considering parametric data (circumference and volume) and nonparametric (analogue scale lines) measurements. The combined evaluation of the edema score is significantly favorable for patients treated with Venoruton. No deep vein thrombosis or superficial vein thrombosis was observed in this study
5. Crosby A et al. Relation between acute hypoxia and activation of coagulation in human beings. Lancet 2003; 361:2207-2208.
Abstract: The risk of venous thrombosis may be increased during aeroplane flights, which may, partly, relate to activation of coagulation by hypoxia that is caused by the reduction of pressure in the aircraft cabin. To find out whether hypoxia activates coagulation, we exposed eight healthy human participants to 8 h of isocapnic hypoxia and 8 h of air as a control. Venous blood was sampled before and after the exposure and analysed for markers of activated coagulation. There were no significant changes. We conclude that hypoxia has no major effect on coagulation in the general population
6. DeHart RL. Health issues of air travel. [Review] [31 refs]. Annual Review of Public Health 2003; 24:133-151.
Abstract: Every day in the United States the airline industry boards over 1.7 million passengers for a total of 600 million passengers per year. As these passengers enter the cabin of their aircraft few are aware of the artificial environment that will protect them from the hazards of flight. Passengers are exposed to reduced atmospheric pressure, reduced available oxygen, noise, vibration, and are subject to below zero temperatures that are only a quarter inch away-the thickness of the aircraft's skin. Over the past decade there have been both technical and lay articles written on the perception of poor cabin air quality. Studies have, in part, supported some of those concerns, but, in general, the air quality exceeds that found in most enclosed spaces on terra firma. Since the events of September 11th, passengers have not only been exposed to the physical stress of flight, but also to social and emotional stress preceding departure. There has been a significant increase in air rage on board aircraft, which poses a threat to flight safety and a fear of harm to passengers and crew. The phrase "economy class syndrome" has received popular press attention and refers to the possibility of deep vein thrombosis (DVT) in the tight confines of an aircraft cabin. Studies have been conducted that demonstrate DVT can occur in flight just as it occurs in other modes of transportation or with prolonged sitting. In part, because of the stress related to commercial flight it is not a mode of transportation for everyone. Certain cardiovascular, pulmonary, and neuropsychiatric conditions are best left on the ground. Although medical problems and death are rare in flight, they do occur, and one major airline reported 1.52 medical diversions per billion revenue passenger miles flown. To provide medical support at 36,000 ft (11,000 m) most airlines now carry on-board medical kits as well as automatic external defibrillators. A recent survey conducted by a major airline revealed that there was at least one physician on 85% of all its flights. Both passenger and cargo aircraft have proven to be vectors of disease in that they transport humans, mosquitoes, and other insects and animals who, in turn, transmit disease. Transmission to other passengers has occurred with tuberculosis and influenza. Vectors for yellow fever, malaria, and dengue have been identified on aircraft. Although there are numerous health issues associated with air travel they pale in comparison to the enormous benefits to the traveler, to commerce, to international affairs, and to the public's health. [References: 31]
7. Arya R et al. Long-haul flights and deep vein thrombosis: a significant risk only when additional factors are also present. British Journal of Haematology 2002; 116:653-654.
Abstract: To address the association between travel and deep vein thrombosis (DVT) we examined the risk factors for DVT in 568 consecutive patients with suspected DVT attending King's College Hospital in London. No significant link between DVT and long-haul travel was demonstrable in this cohort, with an odds ratio of 1.3 (CI 0.6-2.8). Risk of DVT was only increased in long-haul travellers if one or more additional risk factors were present, with an odds ratio of 3.0 (CI 1.1-8.2). Such individuals may benefit from prophylactic measures to minimize risk
8. Belcaro G et al. Prevention of edema, flight microangiopathy and venous thrombosis in long flights with elastic stockings. A randomized trial: The LONFLIT 4 Concorde Edema-SSL Study. Angiology 2002; 53:635-645.
Abstract: The LONFLIT1/2 studies have established that in high-risk subjects after long (> 10 hours) flights the incidence of deep venous thrombosis (DVT) is between 4% and 6%. The LONFLIT4 study has been planned to evaluate the control of edema and DVT in low-medium-risk subjects. The aim of this study was to evaluate edema and its control with specific flight stockings, in long-haul flights. In the first part of the study 400 subjects at low-medium risk for DVT were contacted; 28 were excluded for several nonmedical problems; 372 were randomized into 2 groups to evaluate prophylaxis with stockings in 7-8-hour flights; the control group had no prophylaxis. Below-knee, Scholl, Flight Socks, producing 14-17 mm Hg of pressure at the ankle, were used in the treatment group. The occurrence of DVT was evaluated with high-resolution ultrasound scanning (femoral, popliteal, and tibial veins). Edema was assessed with a composite score based on parametric and nonparametric measurements. Part II: In this part of the study 285 subjects at low-medium risk for DVT were included and randomized into 2 groups to evaluate edema prophylaxis in 11-12-hour flights; the controls had no prophylaxis while the prevention group had below-knee, Scholl, Flight Socks (comparable to part I). RESULTS: Part 1: DVT evaluation. Of the 184 included subjects in the stockings group and 188 in the control group, 358 (96.2%) completed the study. Dropouts were due to compliance or connection problems. Age/sex distributions were comparable in the groups. Stockings Group: of 179 subjects (mean age 49; SD 7; M:F = 101:78), none had DVT or superficial thromboses. Control Group: of 179 subjects (mean age 48.4; SD 7.3; M:F = 98:81), 4 (2.2%) had a DVT. There were also 2 superficial thromboses. In total, 3.35% (6) subjects had a thrombotic event. The difference (p<0.002) is significant. Intention-to-treat analysis detects 15 failures in the control group (9 lost + 6 thromboses) out of 188 subjects (7.9%) versus 5 subjects (2.7%) in the stockings group (p <0.05). All thrombotic events were observed in passengers sitting in nonaisle seats. The tolerability of the stockings was very good and there were no complaints or side effects. Thrombotic events were asymptomatic. No difference was observed in the distribution of events between men and women. The 3 women who had a thrombotic event were taking low-dose, oral contraceptives. Edema evaluation: The level of edema at inclusion was comparable in the 2 groups. After the flight there was a score of 6.7 (3.1) in controls; in the stockings group the score was 2.9 times lower (p<0.05). The control of edema with stockings was clear considering both parametric (circumference, volume) and nonparametric (analogue scale lines) data. Part II: DVT evaluation. Of the 285 included subjects, 271 (95%) completed the study. Dropouts were due to low compliance or connection problems. Age/sex distributions were comparable in the groups. Stockings Group: of 142 subjects (mean age 48; SD 8; M:F = 89:53), none had DVT or superficial thromboses. Control Group: of 143 subjects (mean age 47; SD 8; M:F = 87:56), 3 had a popliteal DVT and 3 a superficial thrombosis. In total, 4.2% (6) subjects had a thrombotic event. The difference (p<0.02) between groups is significant. Intention-to-treat analysis detects 14 failures in the control group (8 lost + 6 thromboses = 9.7%) versus 6 (all lost = 4.2% in the stockings group) (p<0.05). Four of 6 events (3 DVT + 1 SVT) were observed in non-aisle seats. The tolerability of the stockings was very good. No difference was observed in the distribution of events between men and women. Edema evaluation: The level of edema at inclusion was comparable in the 2 groups. After the flight there was a score of 8.08 (2.9) in controls while in the stockings group the score was 2.56 (1.5) (p < 0.005). In conclusion. Scholl Flight Socks are very effective in controlling edema. Also this type of compression is effective in significantly reducing the incidence of DVT and thrombotic events in low-medium-risk subjects, in long
-haul flights. CONCLUSIONS: Considering these observations, Flight Socks are effective in controlling edema and in reducing the incidence of DVT in low-medium-risk subjects, in long-haul flights (7-11 hours)
9. Giangrande PL. Air travel and thrombosis. [Review] [36 refs]. British Journal of Haematology 2002; 117:509-512.
10. Isayev Y et al. "Economy class" stroke syndrome?[comment]. Neurology 2002; 58:960-961.
Abstract: The authors report three cases of ischemic stroke in young adults that occurred during or after an airplane flight. Workup was negative for any cause of stroke other than the presence of a patent foramen ovale (PFO). There is an increasing awareness of deep vein thrombosis and pulmonary embolism occurring in relation to long flights. Individuals with a PFO under these circumstances may be vulnerable to stroke from paradoxic embolism. "Economy class" stroke syndrome may be underdiagnosed and is an eminently preventable cause of stroke
11. Jacobson BF et al. Risk factors for deep vein thrombosis in short-haul cockpit crews: a prospective study. Aviation Space & Environmental Medicine 2002; 73:481-484.
Abstract: BACKGROUND: Venous thrombosis is a concern receiving international attention, especially for passengers traveling on long distance flights. However, there are no data on the effect on cockpit crew of multiple short duration flights. METHODS: Cockpit crew flew two or more internal flights per day. At sign on, 15 ml of blood was venesected from the subjects; at sign off, 20 ml of blood was venesected. All flights originated and terminated at Johannesburg Airport. A full blood count, differential, and D-dimer levels were determined. All participants completed detailed questionnaires stating their ages, alcohol consumption 24 h prior to flight duty, the amount of liquid consumed during flying time, the number of times they went to the toilet, and the amount of time spent sitting during flights. RESULTS: Blood tests on 27 cockpit crew were performed. D-dimers were reduced from 163 ng x ml(-1) to 133 ng x ml(-1) (p = 0.03). Hemoglobin levels dropped from 16.0 g x dl(-1) to 15.8 g x dl(-1) (p = 0.004). Hematocrit levels decreased from 47.2 ml x 100 ml(-1) to 46.9 ml x 100 ml(-1) (p = 0.04). Platelets increased from 221 x 10(9) x L(-1) to 241 x 10(9) x L(-1) (p = 0.001). White cell counts increased from 6.4 x 10(9) x L(-1) to 7.01 x 10(9) x L(-1) (p = 0.0063). Correlation analysis was performed between blood test results and the parameters of the questionnaire. No correlation was found between any of the parameters and the blood results. CONCLUSION: There is no evidence of sub-clinical thrombotic events in this group of subjects. Cockpit crew who fly multiple short duration flights do not suffer sub-clinical thrombotic events as evidenced by an absence of increased D-dimers
12. Kesteven P et al. Incidence of symptomatic thrombosis in a stable population of 650,000: travel and other risk factors. Aviation Space & Environmental Medicine 2002; 73:593-596.
Abstract: Despite recent intensive media interest, the incidence of traveler's thrombosis is unknown. We have undertaken a study of all symptomatic cases of venous thrombosis, presenting to a hospital, in a fixed population of 650,000. There were 1,250 cases of venous thromboembolism diagnosed over a 2-yr period. Of these, only 47 (3.8%) answered positively to the question" did you make a journey of more than 100 mi in the 4 wk prior to diagnosis?" Among the travelers, 60% had traveled by air, 36% by road, and the remainder by rail. At least one medical risk factor for venous thrombosis was present in all but three of our cohort. We conclude that, taking into consideration the enormous number of passengers who travel, the relative risk of traveler's thrombosis is likely to be low. The incidence of this complication in the North East of England is 1 per 27,660 of the whole population
13. Mendis S et al. Air travel and venous thromboembolism. [Review] [36 refs]. Bulletin of the World Health Organization 2002; 80:403-406.
Abstract: There has recently been increased publicity on the risk of venous thrombosis after long-haul flights. This paper reviews the evidence base related to the association between air travel and venous thromboembolism. The evidence consists only of case reports, clinical case-control studies and observational studies involving the use of intermediate end-points, or expert opinion. Some studies have suggested that there is no clear association, whereas others have indicated a strong relationship. On the whole it appears that there is probably a link between air travel and venous thrombosis. However, the link is likely to be weak, mainly affecting passengers with additional risk factors for venous thromboembolism. The available evidence is not adequate to allow quantification of the risk. There are insufficient scientific data on which to base specific recommendations for prevention, other than that leg exercise should be taken during travel. Further studies are urgently needed in order to identify prospectively the incidence of the condition and those at risk. [References: 36]
14. Pheby DF et al. Pulmonary embolism at autopsy in a normal population: implications for air travel fatalities. Aviation Space & Environmental Medicine 2002; 73:1208-1214.
Abstract: BACKGROUND: Much attention has been focused on the apparent risk to long-haul air travelers of venous thromboembolism [deep vein thrombosis (DVT) and pulmonary embolism (PE)], following a number of well-publicized cases. However, there is little epidemiological data to elucidate the problem. PE tends to be under-diagnosed as a cause of death in the general population. This study sets out to establish the level of risk of fatal PE among long-haul passengers arriving in the UK, on the basis of a reappraisal of the role of PE in mortality in the general population. METHODS: Autopsies carried out at Gloucester in 1996-2000 were reviewed to determine age-specific mortality rates for PE for West Gloucestershire. These rates were applied to long-haul air travelers arriving in the UK, for whom the number of passenger-years at risk were calculated, to estimate the expected numbers of deaths in this group. RESULTS: In 3764 autopsies, PE was the primary cause of death in 221 cases (5.9%), while in 304 (8.1%) it was present as an incidental finding. This suggests that PE was involved in approximately 13.9% of deaths, and is more common with age. Passenger years at risk per annum among long-haul passengers arriving in the UK were estimated (mid-range) at 21,830.482; it was anticipated that 6.55 deaths involving PEs, but not related to air travel, could be expected annually in this group. CONCLUSIONS: It appears that the risks of venous thromboembolism due to air travel are overstated. Some deaths are bound to occur inflight, but there is no evidence to suggest an increase, though clearly there are predisposing risk factors for DVT present on long journeys
15. Scurr JH. Travellers' thrombosis. [Review] [5 refs]. Journal of the Royal Society of Health 2002; 122:11-13.
Abstract: Anecdotal reports have suggested a link between flying and the development of blood clots. A recent prospective study looking at passengers before and after flying has demonstrated a much higher incidence of asymptomatic venous thrombosis than we expected. In the same paper, graduated elastic compression stockings reduced this incidence of asymptomatic venous thrombosis. Further studies are required to see how many passengers develop symptomatic deep vein thrombosis and to assess the overall incidence of venous thromboembolic disease. A major epidemiological study, an interventional study to assess the efficacy of mechanical methods of venous thrombosis prophylaxis and the effect of graduated compression stockings, and studies to look at the effect of the cabin environment on thromboembolism are planned. [References: 5]
16. Yeung JM et al. Flight related deep vein thrombosis. [Review] [43 refs]. Scottish Medical Journal 2002; 47:123-126.
17. Bagshaw M. Traveller's thrombosis: a review of deep vein thrombosis associated with travel. The Air Transport Medicine Committee, Aerospace Medical Association. [Review] [28 refs]. Aviation Space & Environmental Medicine 2001; 72:848-851.
Abstract: There is an increasing suspicion among the travelling public and the international media of an association between the occurrence of deep venous thrombosis (DVT) and air travel. It was noted by the UK House of Lords Select Committee on Science and Technology that up to 20% of the total population may have some degree of increased clotting tendency. It follows that some air travellers are at risk of developing DVT when, or soon after, travelling. There have been no epidemiological studies published which show a statistically significant increase in cases of DVT when travelling in the absence of pre-existing risk factors. The literature was reviewed. Current evidence indicates that any association between symptomatic DVT and travel by air is weak, and the incidence is less than the impression given by recent media publicity. [References: 28]
18. Belcaro G et al. Venous thromboembolism from air travel: the LONFLIT study. Angiology 2001; 52:369-374.
Abstract: The LONFLIT study was planned to evaluate the incidence of deep venous thrombosis (DVT) occurring as a consequence of long flights. In the Lonflit study 355 subjects at low-risk for DVT and 389 at high-risk were studied. Low-risk subjects had no cardiovascular disease and used no drugs. All flights were in economy class. The average flight duration was 12.4 hours (range, 10-15 hr). The mean age of the studied subjects was 46 years (range 20-80 yr, SD 11; 56% males). DVT diagnosis was made by ultrasound scans after the flights (within 24 hours). In low-risk subjects no events were recorded while in high-risk subjects 11 had DVT (2.8%) with 13 thromboses in 11 subjects and 6 superficial thromboses (total of 19 thrombotic events in 389 patients [4.9%]). In the Lonflit2 study the authors studied 833 subjects (randomized into 422 control subjects and 411 using below-knee stockings). Mean age was 44.8 years (range, 20-80 yr, SD 12; 57% males). The average flight duration was 12.4 hours. Scans were made before and after the flights. In the control group there were 4.5% of subjects with DVT while only 0.24% of subjects had DVT in the stockings group. The difference was significant. The incidence of DVT observed when subjects were wearing stockings was 18.75 times lower than in controls. Long-haul flights are associated to DVT in some 4-5% of high-risk subjects. Below-knee stockings are beneficial in reducing the incidence of DVT
19. Brown TP et al. The possible effects on health, comfort and safety of aircraft cabin environments. Journal of the Royal Society of Health 2001; 121:177-184.
Abstract: A consultation was undertaken to investigate the views and concerns of stakeholders in the aircraft industry about the possible harmful effects on personal health, comfort and safety of aircraft cabin environments. Stakeholders were identified from a variety of sources including Government agencies, the Internet, House of Lords inquiry, and suggestions of interviewees. They represented: aircraft crews, aircraft constructors and engineers, government departments and authorities, holiday/flight companies, insurance companies, non-governmental organisations, occupational health physicians, passenger representatives, and independent researchers and consultants. Eighty-seven were contacted of which 57 were interviewed over the telephone using a semi-structured questionnaire. Their concerns were transcribed into a standard format and analysed qualitatively. Key stakeholders, along with Government officials, were invited to a workshop to discuss and prioritize the issues raised during the interviews. The main concerns expressed by the participants fell into five main areas: deep vein thrombosis, air quality, infection, cosmic radiation, and jet lag and work patterns. In addition, a number of safety concerns were raised as well as comments on the provision of appropriate advice to passengers. It was generally felt that further research was required on each of these subjects, as well as an improvement in the quality, quantity and availability of information provided for passengers prior to boarding a flight
20. Brundrett G. Comfort and health in commercial aircraft: a literature review. [Review] [75 refs]. Journal of the Royal Society of Health 2001; 121:29-37.
Abstract: 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. The wide bodies of many new aircraft permit the airlines to have very flexible seating options. Airline operators currently have an important role in determining the comfort and spaciousness of the seating in their aircraft. Passengers who remain seated for the bulk of a flight may risk oedema or deep vein thrombosis. This could be particularly important for larger people in certain economy class seats. The absence of smoking on planes has encouraged designers to cut back on the rate of cabin ventilation and hence introduce filtered recirculated air to the aircraft cabin. In new planes the ventilation rate is under pilot control and savings (economies) can be achieved by using decreased ventilation. A lower ventilation rate may lead to 'less comfortable air quality' in some parts of the plane and an increased risk of possible cross-infection from other passengers on the flight. Technological advances in jet engine design has permitted larger passenger planes to fly longer distances and at greater altitudes than ever before. The higher flying altitude is associated with a lower cabin pressure, which has an important physiological effect on oxygen saturation in the blood of both crew and passengers, particularly for the very young, the elderly and those who are less fit. [References: 75]
21. Cheung B et al. Pre-existing pulmonary thromboembolic disease in passengers with the "economy class syndrome". Aviation Space & Environmental Medicine 2001; 72:747-749.
Abstract: BACKGROUND: Pulmonary emboli, which have occurred in association with air travel, in the past have been thought to have arisen from deep venous thromboses (DVT) which formed during the flight. HYPOTHESIS: This study was performed to test the idea that not all pulmonary emboli which occur following air travel are the result of inflight DVT formation. METHODS: Fourteen cases of fatal "economy class syndrome" were examined histologically to determine the age of the fatal thromboemboli. RESULTS: In 5 of the cases, evidence of pre-existing pulmonary thromboembolic disease was present and in 4 of these cases the fatal thromboemboli observed in the lung tissue pre-dated the flight. Fresh perimortem thrombus without evidence of organization or hemosiderin deposition was observed in 9 cases. CONCLUSIONS: The commonly held pathological mechanism that the conditions of the flight lead to DVT formation and subsequent pulmonary embolism are not applicable in all cases of "economy class syndrome" and thus other pathophysiological mechanisms must be entertained
22. Kesteven PJ et al. Clinical risk factors for venous thrombosis associated with air travel. Aviation Space & Environmental Medicine 2001; 72:125-128.
Abstract: BACKGROUND: Recent reports have linked air travel with venous thrombo-embolism (VTE). Risk factors and associated features of this link are poorly understood. We have accumulated clinical data from a relatively large cohort of patients with traveler's thrombosis. METHODS: A total of 86 patients who developed venous thromboembolism within 28 d of flying were questioned concerning traveling habits, medical history (including risk factors for VTE) and characteristics of the index flight. RESULTS: Of the patients, 72% had at least one risk factor for VTE (excluding thrombophilia) prior to their flight. Of interest, 87% of VTE cases occurred following either a return trip or after an outward journey involving long trips made up of sequential flights. In only two cases could no identifiable risk factor or earlier journey be found. Duration of flights ranged from 2 to 30 h. Of responders, 38% presented with chest symptoms; 92% with VTE developed symptoms within 96 h of their flight. CONCLUSION: We conclude that the majority of VTE associated with air travel occur in those with identifiable risk factors prior to their flight, and that sequential flights may increase this risk
23. Scurr JH et al. Frequency and prevention of symptomless deep-vein thrombosis in long-haul flights: a randomised trial.[comment]. Lancet 2001; 357:1485-1489.
Abstract: BACKGROUND: The true frequency of deep-vein thrombosis (DVT) during long-haul air travel is unknown. We sought to determine the frequency of DVT in the lower limb during long-haul economy-class air travel and the efficacy of graduated elastic compression stockings in its prevention. METHODS: We recruited 89 male and 142 female passengers over 50 years of age with no history of thromboembolic problems. Passengers were randomly allocated to one of two groups: one group wore class-I below-knee graduated elastic compression stockings, the other group did not. All the passengers made journeys lasting more than 8 h per flight (median total duration 24 h), returning to the UK within 6 weeks. Duplex ultrasonography was used to assess the deep veins before and after travel. Blood samples were analysed for two specific common gene mutations, factor V Leiden (FVL) and prothrombin G20210A (PGM), which predispose to venous thromboembolism. Asensitive D-dimer assay was used to screen for the development of recent thrombosis. FINDINGS: 12/116 passengers (10%; 95% CI 4.8-16.0%) developed symptomless DVT in the calf (five men, seven women). None of these passengers wore elastic compression stockings, and two were heterozygous for FVL. Four further patients who wore elastic compression stockings, had varicose veins and developed superficial thrombophlebitis. One of these passengers was heterozygous for both FVL and PGM. None of the passengers who wore class-I compression stockings developed DVT (95% CI 0-3.2%). INTERPRETATION: We conclude that symptomless DVT might occur in up to 10% of long-haul airline travellers. Wearing of elastic compression stockings during long-haul air travel is associated with a reduction in symptomless DVT
24. Kesteven PL. Traveller's thrombosis. [Review] [25 refs]. Thorax 2000; 55 Suppl 1:S32-S36.
25. Kraaijenhagen RA et al. Travel and risk of venous thrombosis.[comment]. Lancet 2000; 356:1492-1493.
Abstract: In 1998 the term economy class syndrome was coined to describe the association between travel and thrombosis. A fair risk estimate, however, has not been done. We report the results of a prospective study, in which we kept the effect of bias to a minimum. We compared travel history in 788 patients with venous thrombosis with that of controls with similar symptoms but in whom the disease had been excluded. For air travel alone, the odds ratio was 1.0 (95% CI 0.3-3.0); also, no association was recorded for other methods of transportation. We have shown that, there is no increased risk of deep vein thrombosis among travellers
26. Cable GG. Hyperhomocysteinaemia and upper extremity deep venous thrombosis: a case report. Aviation Space & Environmental Medicine 1999; 70:701-704.
Abstract: A case is presented of a 24 yr old military aircrew applicant who developed a right axillary subclavian deep venous thrombosis following physical exertion. Investigations revealed damage to the right axillary subclavian venous system and limitation to flow. Coagulation studies also showed an elevated plasma homocysteine level. Hyperhomocysteinemia has recently been recognized as a risk factor for venous thromboembolic disease. Damage caused by the thrombosis, the hyperhomocysteinemia and environmental factors encountered in flight, may predispose him to recurrent episodes of thrombosis. This complex case involves aspects of hematology and the nature of coagulation which are only just being elucidated and as yet are poorly understood, and highlights some serious aeromedical implications for pilots afflicted with these conditions
27. Ferrari E et al. Travel as a risk factor for venous thromboembolic disease: a case-control study.[comment]. Chest 1999; 115:440-444.
Abstract: BACKGROUND: The link between travel and the risk of venous thromboembolic disease (VTED) has been widely suspected. However, only cases or series of cases have been reported in the literature. STUDY OBJECTIVES: By means of a case-control study, we sought to confirm this relationship and to determine the main features, if any, of these posttravel VTEDs. DESIGN: The history, in particular the history of recent travel, of 160 patients presenting in our department with VTED was scrupulously investigated. All journeys undertaken during the preceding 4 weeks and lasting > 4 h by whatever means of transport were considered. The same questionnaire was submitted to a control group. RESULTS: When the two groups of patients are compared, a history of recent travel is found almost four times more frequently in the VTED group (p < 0.0001). The odds ratio for having a VTED in patients who traveled was 3.98 (95% confidence interval, 1.9 to 8.4). Means of travel used included the train in 2 cases, airplane in 9, and car in 28. Mean duration of travel was 5.4+/-2.1 h. These posttravel VTEDs are not confined to a specific location, seem to involve no particular predisposition, and are more often "idiopathic." This fact supports the hypothesis that travel alone can produce vein clot formation. CONCLUSIONS: A history of recent travel is a risk factor for VTED. Posttravel venous thrombotic events can occur after short journeys in patients with no other risk factors or concomitant disease
File for download
If you would like to import this hot topic into a reference manager programme, please download from the right hand menu. For guidance please refer to our MEDLINE Plus frequently asked questions.
Request free email updates on this topic (members only)
We can send you a monthly email update on this topic (or any other); please contact us at info.medline@bma.org.uk with your membership number and the email address to which you would like the updates to be sent. If you would like to modify the requirements, please let us know as much detail as possible, and give a telephone number on which you can be contacted during the day.
Books/reports held by the BMA Library
Griffin J. Deep vein thrombosis and pulmonary embolism. Office of Health Economics, 1996.
BMA location: R 2592 [Borrow]
Videos held by the BMA Library
Deep vein thrombosis. 1996. 9 mins.
Importance of diagnosis of deep vein thrombosis to prevent complications. Physical signs in diagnosis are explained.
BMA location: BMA 309V [Borrow]
Diagnosis of deep vein thrombosis. 1986. 9 mins.
Discusses the difficulty of accurate diagnosis of deep vein thrombosis and demonstrates different methods. The importance of early treatment is stressed.
BMA location: BMA 344V [Borrow]
Medical review : deep vein thrombosis. 1994. 17 mins.
Mr. John Scurr, consultant surgeon, stresses the importance of early diagnosis and treatment. As large surgical procedures are as much of a risk factor as age and past history, patients coming into hospital are now being given prophylactic treatment, including compression hosiery and drugs. Actuality of female patient with varicose veins. N.B. Includes commercial break.
BMA location: BMA 1270V [Borrow]
Additional web resources
Airhealth.org
Airhealth.org is a US non-profit organisation "dedicated to ending the suffering and deaths caused by flight-induced blood clots". The site includes information on clots, risk, lists US lawsuits, and comments on current research.
http://airhealth.org/
Aviation health institute
A UK charity formed in 1996, the Aviation health institute aims to promote the health and well-being of air passengers worldwide. The site features articles on DVT and other flight related health issues, in particular monitoring the various cases being brought by passengers against airlines.
http://www.aviation-health.org/
BMA library factsheet: Aviation medicine
Our aviation medicine factsheet covers the library's print and selected online resources, and lists organisations and libraries in the area.
http://www.bma.org.uk/ap.nsf/Content/LIBAviationMedicine
BMA library factsheet: Travel medicine
Our factsheet covers all aspects of travel medicine featuring our print resources, many websites, and contact organisations in the UK.
http://www.bma.org.uk/ap.nsf/Content/LIBTravelMedicine
British Airways
This British Airways page highlights research, risk factors, signs and symptoms, and offers advice to avoid development of DVT.
http://www.britishairways.com/travel/healthdvt/public/en_
Department of Health: advice on travel-related Deep Vein Thrombosis
From the Department of Health, an overview for travellers on it's current views on DVT, with links to further advice and information.
http://www.dh.gov.uk/PolicyAndGuidance/HealthAndSocialCareTopics/BloodSafety/DVT/fs/en
Medlineplus: Traveler's health
This US site is produced by the National Library of Medicine and National Institutes of Health and is aimed at the general public although it links to much technical information. Contains news, overviews, pictures, prevention/screening, research, specific aspects, genetics, dictionaries, directories, organisations, and specific links to advice for children and teenagers.
http://www.nlm.nih.gov/medlineplus/travelershealth.html
Originally as Economy Class Syndrome: Updated 5 December 2001
Revised 26 February 2004
Amended 10 June 2004