1) Travel-related thromboembolism: mechanisms and avoidance.

Schobersberger W, Schobersberger B, Partsch H.

Institute for Sports Medicine, Alpine Medicine & Health Tourism, TILAK Innsbruck and Private University for Health Sciences, Medical Informatics and Technology (UMIT), Eduard Wallnöfer-Zentrum 1, 6060 Hall, Austria. wolfgang.schobersberger@uki.at

Abstract

“Evidence regarding the existence of travel-related venous thrombosis and pulmonary embolism is building. Research suggests that travel of all kinds increases the risk by two- to four-fold. Risks are not restricted to air travel alone. For travelers without any known risk factors, the risk of experiencing venous thromboembolism is likely to be very low. However, risks increase significantly in the presence of known risk factors, such as age over 60 years, thrombophilic disorders, varicose veins, history of thromboembolism, obesity, women taking oral contraceptives and travel duration over 12 h. A combination of one or more of these risk factors raises the probability of developing travel-related thromboembolism. Possible contributing factors, such as cramped sitting (with suppressed leg venous flow), moderate hypoxia, low humidity in the aircraft and dehydration, are discussed. Depending on the risk profile of individuals, the use of graduated compression stockings and/or pharmacological interventions (low-molecular-weight heparins are preferred) may be recommended.”

Schobersberger W. Expert Rev Cardiovasc Ther. 2009 Dec;7(12):1559-67.

2) The Tromped: a solution for flight-related deep vein thrombosis?

Collins C, Fitzgerald P, Kennedy DM, Corrigan T, Jerrams S, Bouchier-Hayes DJ.

Faculty of Engineering, Dublin Institute of Technology, Dublin, Ireland.

Abstract

“Flight-related deep vein thrombosis (DVT) is well recognized. Reduced venous return occurs during immobility. This alteration in venous hemodynamics may contribute to DVT development. A prototype design of an in-flight exercise device to stimulate ambulatory bloodflow while seated has been developed, consisting of a foot pedal attached to a base by a hinge mechanism. Four devices of differing resistance were evaluated. Calf muscle pump function was assessed by air plethysmography in 10 healthy volunteers. Ejection volume fraction and RVF were determined in the standing position (control values) and were compared with those achieved by depression of the 4 devices while seated. Similar EVF and RVF values were achieved by the control and 2 of the devices. Plantar flexion against a predetermined resistance can effectively activate the calf muscle pump while seated and may reduce the incidence of flight-related DVT.” Collins, et al. Angiology. 2008 Feb-Mar;59(1):72-6.

3) Effect of leg exercises on popliteal venous blood flow during prolonged immobility of seated subjects: implications for prevention of travel-related deep vein thrombosis.

Hitos K, Cannon M, Cannon S, Garth S, Fletcher JP.

Department of Surgery, University of Sydney, Westmead Hospital, Westmead, NSW, Australia.

Abstract

“BACKGROUND: Venous stasis is an important contributing factor in the development of travel-related deep vein thrombosis. This study examined factors affecting popliteal venous blood flow in order to determine the most effective exercise regimen to prevent venous stasis. METHODS: Twenty-one healthy subjects were randomly assigned to various activities over a 9-week period. Subjects remained seated throughout the investigation and 3660 duplex ultrasound examinations were performed by a single examiner using a SonoSite 180 Plus handheld ultrasound. Baseline popliteal vein blood flow velocity, cross-sectional area and volume flow in subjects sitting motionless were assessed in the first 3 weeks.The remaining 6 weeks involved subjects performing airline-recommended activities, foot exercises, foot exercises against moderate resistance and foot exercises against increased resistance in order to determine the most beneficial method for enhancing popliteal venous flow. Sitting with feet not touching the floor and the effect of sleeping were also assessed. RESULTS: The median age of the subjects was 22 years (range: 18-25.5 years), height 171 cm (162.5-180.5 cm) and body mass index 25.3 kg m(-2) (23.2-26.3 kg m(-2)). Blood volume flow in the popliteal vein was reduced by almost 40% with immobility of seated subjects and by almost 2-fold when sitting motionless with feet not touching the floor. Foot exercises against increased resistance positively enhanced volume flow (P < 0.0001). CONCLUSION: Leg exercise regimens enhanced popliteal venous flow during prolonged immobility of seated subjects, reinforcing the importance of regular leg movement to prevent venous stasis during prolonged sitting, such as in long-distance travel.” Thromb Haemost. 2007 Sep;5(9):1890-5.

4) [Traveler’s thrombosis]

[Article in German] Riedel M, Bohanes V. Deutsches Herzzentrum Lazarettstrasse 36 80636 München, Germany. m.riedel@dhm.mhn.de

Abstract

“It is pathophysiologically conceivable that prolonged sitting in a tight space (e.g., in airplane or other transport vehicle) may lead to leg vein thrombosis. The association between the incidence of venous thromboembolism and long travel has not been sufficiently documented but seems probable. However, this association is only weak and the incidence of symptomatic thromboembolism much lower than the impression given by the recent publicity. In a healthy person, the risk of suffering a clinically relevant leg vein thrombosis solely because of a flight is extreme low. In persons with risk factors for venous thromboembolism, the flight represents an additional, as yet not quantifiable risk. This risk increases with the duration of the travel. The most important cause of thrombosis during long journeys seems to be venostasis due to relative immobilization. It is not clear whether flight travel represents a higher risk of thrombosis compared to other transport vehicles with comparable duration and immobilization. Until more exact information becomes available, it seems reasonable to recommend simple isometric and isotonic leg exercises during long travel. More aggressive measures must be considered for persons with risk factors for thromboembolism, but these measures should be individualized.” Reidel et al. Z Kardiol. 2002 Aug;91(8):605-13.