title: Aneurysm sac pressure monitoring: does the direction of pressure measurement matter in fibrinous thrombus?
abstract: OBJECTIVE
  This study was conducted to clarify the effect of the direction of pressure measurement on the pressure readout in fibrinous thrombus of the abdominal aortic aneurysm.
  
  
  METHODS
  Three weights of 468 g (weight 1), 578 g (weight 2), and 675 g (weight 3) were molded. A specimen of human fibrinous thrombus was positioned under the weights. Because the surface area of the weights and the thrombus was 400 mm(2), weights 1, 2, and 3 caused pressures of 88, 108, and 127 mm Hg, respectively. Pressure measurements were performed at different angles between the sensor and the applied force (0 degrees , 22.5 degrees , 30 degrees , 45 degrees , 60 degrees , 67.5 degrees , 90 degrees ) Thrombi of 10 different patients were analyzed. Pressure measurements in the thrombi at different angles were statistically compared by a linear mixed model analysis.
  
  
  RESULTS
  The measurements at 90 degrees differed statistically from the measurements at 0 degrees , 22.5 degrees , 30 degrees , 45 degrees , 60 degrees , and 67.5 degrees (P < .001). The pressure readout was only similar to the applied pressure when the pressure sensor was positioned at 90 degrees to the applied force. Pressure measurements in other sensor positions resulted in lower pressure measurements. Pressure changes were detected in all sensor positions. There appeared to be no significant difference between the pressure measurements taken at same angles in the 10 thrombi (P > .05).
  
  
  CONCLUSIONS
  In fibrinous thrombus of abdominal aortic aneurysm, the direction of pressure measurement influenced the pressure readout.
authors.affiliation: Department of Surgery, Division of Vascular Surgery, Leiden University Medical Center, Leiden, The Netherlands. j.w.hinnen@lumc.nl <j.w.hinnen@lumc.nl>
authors.forename: Jan-Willem
authors.initials: JW
authors.lastname: Hinnen
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Rixen
authors.forename: Olivier H
authors.initials: OH
authors.lastname: Koning
authors.forename: Hajo J
authors.initials: HJ
authors.lastname: Van Bockel
authors.forename: Jaap F
authors.initials: JF
authors.lastname: Hamming
mesh_terms: D017544:Aortic Aneurysm, Abdominal / Q000378:metabolism / Q000503:physiopathology* / Q000601:surgery; D001019:Aortic Rupture / Q000378:metabolism / Q000503:physiopathology*; D001794:Blood Pressure; D001795:Blood Pressure Determination / Q000295:instrumentation / Q000379:methods*; D005337:Fibrin / Q000378:metabolism*; D006801:Humans; D016014:Linear Models; D013927:Thrombosis / Q000378:metabolism / Q000503:physiopathology* / Q000601:surgery; D014160:Transducers, Pressure
chemical_list: D005337:Fibrin