**Abstract**

Deep vein thrombosis (DVT) of the lower limbs is a serious condition that can lead to pulmonary embolism (PE) in about 15–24% of cases. If it is not diagnosed/ treated timely, nearly 15% of these PE are lethal. The relationship between travel and staying in the same position for a long time is well-known since World War II. Generally, it is more frequent in air flights. It is also associated with the economic downturn in airplanes because passengers have limited space and have greater difficulty of moving. It is estimated that approximately 1–6% of long-haul passengers arrive at their destination with a clot in their veins, but most DVT are asymptomatic.

**Keywords:** thrombosis, travel risk factors

#### **1. Introduction**

The real incidence of deep vein thrombosis is not fully known, due to the fact that the studies were depended only on clinical data (the majority of the reported cases had no clinical signs) without confirmation by laboratory and ultrasound findings. A further reason is that the referred studies investigated either DVT or PE and rarely both of the diseases [1, 2]. D-dimers have prognostic value only in 50% of cases of deep vein thrombosis or pulmonary embolism [3, 4]. Most of the published studies indicate that there is an increased risk of venous thrombosis when the travel duration is more than 4 h [3, 4]. Deep vein thrombosis is a serious health issue involving at least half a million Americans each year, and at least 1 in 10 will die suddenly. It depends on the mode of travel either by air flight company or car, bus, and train based fully on all travel-related risks of thrombosis. It is estimated that the risk of such an episode occurring during a long travel is 3–5%, with no reliable international accurate data [5–8]. The reason for the increased risk of venous thrombosis is an exclusive phenomenon of all travel-related thromboses, which play a role in clot formation. Stasis during the journey, the pressure of the "narrow" seat on the vessels, dehydration, and maybe reduced oxygen saturation are some of the factors that symptoms of venous thrombosis or pulmonary embolism do not always appear immediately. They may occur up to 8 weeks after the travel [9, 10].

Regardless of whether it is a trip by car, train, bus, or plane, travel thrombosis (for flight travel also named "economy class syndrome") will manifest up to 4 weeks after traveling according to the British Committee for Standards in Hematology up to 6 weeks after long-haul flights [9, 10]. It is estimated that 5–15% of all proven venous thromboembolism (VTE) occur in connection with long-haul flights [11, 12]. The risk is highest in the first week and then decreases continuously; the majority (approx. 60–75%) of all travel thrombosis are asymptomatic/low-symptom thrombosis exclusively located in the lower limbs, which is perceived as "unpleasant leg swelling/edema" due to long sitting with the legs hanging down [11, 12].
