Pamela Gerrard, Clare Kelly, Lisa Molloy
Background
With the embarkment into a new millenium, we are fortunate to have the world at our feet through improved and increased accessibility to air travel. Coinciding with this, we have experienced an increasing worlwide media interest in air travel related venous thromboembolism(VTE) incidents.
VTE has been recorded since 1954 in relation to land and air travel(Gallus & Barker 2001) and was labelled the economy class syndrome in 1988 by Cruickshank et al. This name was based on the hypothesis that long-term sitting in a cramped position was a contributing and initiating factor for the development of VTEs(Landgrafet al 1994). Morgan (2001) refers to Simpson’s observations in WWII where he noted an increased incidence in VTE-related deaths (24) coinciding with the London blitz during Sept-Oct 1940. Prolonged periods spent sitting in cramped conditions in air-raid shelters led Simpson to conclude that the increased risk was due to calf compression. This caused obstruction leading to stasis, therefore he recommended the installation of bunks in shelters. By December 1940 there was a significant decrease in reported cases.
Today it is generally speculated that prolonged travel in a seated position can cause venous stasis (Landgraf et al 1994, Kesteven et al 2001). However, at present these suggestions have no concrete basis and the evidence therefore remains circumstantial. It is thought that this limited space can contribute to a large number of ‘rheological and biochemical alterations affecting all three variables in Virchow’s triad’ (Arfvidsson and Eklof 2001).This triad is a mechanism on which the formation of VTEs is based:
- Stasis
- Endothelial Damage
- Hypercoagulability
(Landgraf et al 1994)
Predisposing factors that contribute to VTE in long haul flights are listed below.
Substantial Risk
Recent surgery/trauma, previous DVT, malignant disease, thrombophilia, Factor V Leiden(FVL), paralysis of the lower limbs, gene mutation.
Moderate Risk
- Age >40 years, immobility, dehydration, pregnancy/post-partum, cardio-respiratory disease, oral contraceptive/HRT, varicose veins(Driver 2001).
- Additional environmental factors and habits of the traveller which may also contribute:
- seating posture, seat design, caffeine/alcohol/drug intake
- Venous stasis due to prolonged seating in a limited space has been considered to be an important factor in the formation of VTEs especially in long haul flights (Landgraf et al 1994). Today’s airline seats are considered to be a modified form of torture, especially in economy class, due to the lack of individual space (Burnard and Smith 2001). Seat pitch (ie. space between back of cushion to the seat in front) is no longer regulated and now 28-31 inches is the normal in most economy cabins, where as 40 inches was the recommended space. In US domestic flights, the width of seats is only 17.2 or 18 inches while on longer flights the width is increased to 18.5 inches. Office chairs usually have a minimum width of 19 inches. It has also been shown that the height of the seat is not appropriate for very tall or small passengers due to increased likelihood of more pressure points, facilitating VTE formation. A combination of these points limits passengers’ ability to change posture thereby encouraging immobility and possibly the formation of VTEs (Murphy 2001, Streshinsky 2000).Regulations now regarding the number of seats on a plane are related to the number of emergency exits on a plane and not passengers’ comfort, even though there are rules defining the minimum space for the transportation of live animals (Murphy 2001, Aviation authority 2001 and Time 2001). For economy class passengers to have extra legroom would incur a higher ticket price.
