The secret enemy during a flight: Economy class syndrome

The secret enemy during a flight: Economy class syndrome IntroductionAir transportation is becoming popular by day, mainly because of today's modernized airplanes that are fast, safe, and comfortable.However, this brings along with it health problems.Approximately, 1 billion people travel around the world by air every year (1), and at least 5% of them are patients with chronic health problems (2).Venous thromboembolism (VTE) is a clinical condition that involves two related issues, venous thrombosis and pulmonary embolism (PE) (3).It affects approximately 2-3 individuals per 1000 per year.VTE is the third cause of death by vascular diseases, only surpassed by myocardial infarction and ischemic stroke.In addition, it is the most common cause of preventable death in hospitalized patients (4, 5).It is difficult to identify the true incidence owing to asymptomatic cases, and postmortem studies indicate higher incidence of deep vein thrombosis (DVT) than is known.Even though the incidence of symptomatic passenger thrombosis is unknown, it is believed that there are 30,000 cases per year in the UK.The annual incidence is 1/1,000 among the general population, 0.4-3/10,000 (6) among travelers, and 1-2.5/10,000 among airplane passengers (7).The incidence of DVT and pulmonary thromboembolism (PTE) because of age and sex varies.For instance, it may be 10.7% among male patients around the age of 80 years (8).DVT is more common in women in the reproductive age group, whereas it is more common in men after 45 years of age.In general, it is more common in men than in women (1.2/1) (9).The first cases of VTE associated with air travel were reported in 1954; and since then, other cases have been described (10).The vast majority of victims suffer PE and/or DVT; but patients with subclavian vein thrombosis (11), cerebral vein thrombosis (12), stroke, and arterial thrombosis (13) have also been reported.Homans reported the first venous thrombosis seen owing to flight inactivity in a 54-year-old physician during a 14-hour flight from Venezuela to Boston (14).In a cohort of healthy subjects, the absolute risk of VTE on flights lasting more than 4 hours was 1 in 6,000 (15).A metaanalysis involving 14 studies reported 4,055 cases of VTE in trips lasting up to 8 hours (16).These studies included both air and overland trips with the follow-up time after the journey ranging from 2 to 8 weeks.The relative risk for VTE was 2.8 and at each increment of 2 hours in travel time, there was an approximate 18% increase in the risk of VTE.Considering only air travel, this risk increased to 26%, suggesting a cumulative effect of flight time in the genesis of VTE.MacCallum et al. (17) demonstrated that on flights lasting less than 4 hours, the risk of VTE was approximately two times higher than in patients who did not travel and remained high in the 4 subsequent weeks.In long-haul flights (greater than 12 hours as one or more flights), the risk of VTE was around three ABSTRACTDeep venous thrombosis (DVT) and pulmonary thromboembolism (PTE) are the major causes of morbidity and mortality in immobile patients.There is observational evidence that intercontinental air travel is associated with a high incidence of DVT and PTE during or within 48 hours of long-distance flights.This situation is known as the economy class syndrome and can affect both the cabin crew and passengers.The term "economy class syndrome" refers to the occurrence of thrombotic events that mainly occur in passengers in the economy class of the aircraft during long-haul flights.This syndrome results from several factors related to the aircraft cabin and the passenger, acting together to predispose to excessive blood coagulation, which can result in venous thromboembolism.In this review, we have shared the relationship between air travel and the formation of DVT and PTE.