title: Leg edema formation and venous blood flow velocity during a simulated long-haul flight.
abstract: BACKGROUND
  Long-distance traveling in a sitting position may be associated with an increased incidence for venous thromboembolism. As major contributing factors immobility and compression of leg veins are discussed. At present no studies have been performed measuring the time course of lower limb blood flow, leg volume and leg tissue thickness during a long-haul flight.
  
  
  METHODS
  We measured limb volumes (plethysmographic method), lower leg tissue thickness and lower limb venous hemodynamics before, during and after 10 h sitting in modern aircraft chairs under normobaric hypoxia in healthy volunteers (n=12).
  
  
  RESULTS
  Lower leg volume was already significantly increased after 4 h sitting (+109 ml) reaching its maximum after 10 h (+145 ml). These changes were accompanied by an increased body weight, total body water, extracellular water and tissue thickness of the tibia. No significant changes were measured for leg vessel cross-section diameters and maximal flow velocities in superficial femoral veins. After 10 h sitting core temperature, overall surface temperature and skin temperatures in front of the tibia were significantly increased. All parameters returned to baseline one day after sitting.
  
  
  CONCLUSIONS
  Prolonged sitting in modern aircraft seats is associated with a remarkable fluid accumulation in the lower legs which mainly occurred during the first hours. These fluid shifts were independent of lower limb venous hemodynamics and vessel cross-sectional diameters.
authors.affiliation: Department for General and Surgical Intensive Care Medicine, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Mittermayr
authors.forename: Dietmar
authors.initials: D
authors.lastname: Fries
authors.forename: Hannes
authors.initials: H
authors.lastname: Gruber
authors.forename: Siegfried
authors.initials: S
authors.lastname: Peer
authors.forename: Anton
authors.initials: A
authors.lastname: Klingler
authors.forename: Uwe
authors.initials: U
authors.lastname: Fischbach
authors.forename: Hanns-Christian
authors.initials: HC
authors.lastname: Gunga
authors.forename: Eberhard
authors.initials: E
authors.lastname: Koralewski
authors.forename: Martin
authors.initials: M
authors.lastname: Faulhaber
authors.forename: Markus
authors.initials: M
authors.lastname: Simmer
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schobersberger
mesh_terms: D000401:Aircraft; D001783:Blood Flow Velocity; D001823:Body Composition; D001831:Body Temperature; D001835:Body Weight; D004487:Edema / Q000209:etiology*; D006801:Humans; D007866:Leg / Q000098:blood supply / Q000473:pathology*; D010991:Plethysmography; D011187:Posture; D013923:Thromboembolism / Q000209:etiology; D013997:Time Factors; D014195:Travel; D020246:Venous Thrombosis / Q000209:etiology