title: Interstitial fluid shifts in simulated long-haul flights monitored by a miniature ultrasound device.
abstract: BACKGROUND
  Long-haul flights (LHF) are known to be connected with an increased risk of deep vein thrombosis. There is still some lack of clarity about the impact of hypoxia and lower levels of air pressure and humidity on passengers during flight. This cross-over study researched interstitial fluid shifts traced by measurements of tissue thickness (TT) under controlled simulated conditions of a LHF.
  
  
  METHODS
  There were 18 male volunteers (28.4 +/- 8.1 yr) who were subjected to both procedure 1 (altitude: 2500 m/humidity: 15%)and procedure 2 (altitude: 0 m/humidity: 50%), each lasting 8 h. Measurements forTT at tibia (TT-t) and forehead sites (TT-f) were made using a miniature A-mode ultrasonic device. Fluid intake, bodyweight, heart rate, oxygen saturation, and systolic and diastolic blood pressure were recorded over time. Blood samples were collected before (t0) and after 8 h (t8) to analyze plasma viscosity (PV).
  
  
  RESULTS
  We found an increased TT-t over time at an altitude of 0 m (t0: 4.8 +/- 1.2; t8: 5.2 +/- 1.3) and 2500 m (t0: 4.7 +/- 1.2; t8: 5.3 +/- 1.2), respectively, without differences between study groups. TT-f increased significantly over time at 2500 m (t0: 4.6 +/- 0.8; t8: 4.9 +/- 0.8) with significantly higher TT compared to 0 m at t8 (4.5 +/- 0.7). No further significant differences were found.
  
  
  CONCLUSIONS
  This study suggests that the controlled variable "sitting position" seems to have the strongest influence on leg edema formation during LHF. PV appears not to be affected as long as passengers receive adequate fluid intake. Further studies should be conducted to investigate different methods of preventing venous congestion. These pre-emptive efforts could be tested easily using a miniature handheld ultrasound device.
authors.affiliation: Department of Anesthesiology and Intensive Care, University of Luebeck Medical School, Luebeck, Schleswig-Holstein, Germany. peter.iblher@uk-sh.de
authors.forename: Peter
authors.initials: P
authors.lastname: Iblher
authors.forename: Hauke
authors.initials: H
authors.lastname: Paarmann
authors.forename: Kristina
authors.initials: K
authors.lastname: Stuckert
authors.forename: Andreas
authors.initials: A
authors.lastname: Werner
authors.forename: Friedrich K
authors.initials: FK
authors.lastname: Klotz
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eichler
mesh_terms: D000328:Adult; D000337:Aerospace Medicine; D000399:Air Pressure; D000531:Altitude; D001794:Blood Pressure; D001809:Blood Viscosity / Q000502:physiology; D018592:Cross-Over Studies; D004487:Edema / Q000209:etiology; D045604:Extracellular Fluid / Q000000981:diagnostic imaging / Q000502:physiology*; D018495:Fluid Shifts / Q000502:physiology*; D005546:Forehead / Q000000981:diagnostic imaging; D006339:Heart Rate; D006801:Humans; D006813:Humidity; D000860:Hypoxia / Q000150:complications; D007103:Immobilization / Q000502:physiology*; D007866:Leg / Q000000981:diagnostic imaging; D008297:Male; D008904:Miniaturization; D010092:Oximetry; D013997:Time Factors; D014465:Ultrasonics / Q000295:instrumentation; D014463:Ultrasonography; D020246:Venous Thrombosis / Q000209:etiology; D055815:Young Adult