title: Aneurysm sac pressure monitoring: effect of pulsatile motion of the pressure sensor on the interpretation of measurements.
abstract: OBJECTIVE
  To determine the effect of pulsatile motion of graft-attached pressure sensors on the accuracy of aneurysm sac pressure measurement.
  
  
  METHODS
  Pressure inside a pressure box was measured with a sensor attached to a stent-graft (Sensorgraft) facing a sensor in fixed position (Sensorbox). Maximum inter-sensor variation of Sensorgraft and Sensorbox was determined in static experiments. Experiments with pulsatile circulation were performed with a compliant and a noncompliant stent-graft at 120/80 mmHg and 160/95 mmHg. Pressure measurements in the box were repeated after the box pressure was increased from 0 to 120 mmHg. Sensorgraft motion was measured by ultrasound. Measurements with Sensorgraft were compared to those with Sensorbox using Pearson correlation coefficients to determine the concordance between the sensors.
  
  
  RESULTS
  The maximum inter-sensor variation was 4 mmHg. Increased box pressure induced progressive pulsatile graft and sensor motion during all experiments. During the experiments with the compliant graft at systemic pressures of 120/80 and 160/95 mmHg, the maximum inter-sensor variation was exceeded at box pressures of 65 and 75 mmHg, respectively. The sensor motion at these box pressures was 214+/-2.70 microm and 210+/-0.93 microm, respectively. Measurements of Sensorgraft were higher than Sensorbox, up to 13 mmHg at a box pressure of 120 mmHg. The Pearson correlation coefficients during these experiments were 0.99 and 1.00 (p < 0.001), respectively. In the experiments with the noncompliant graft, the maximum inter-sensor variation was not exceeded, and sensor motion was only 7 +/- 0.46 microm and 26 +/- 1.48 microm, respectively. The Pearson correlation coefficient during these experiments was 1.00 (p < 0.001).
  
  
  CONCLUSIONS
  Pulsatile sensor motion can influence the accuracy of pressure measurement. More compliant grafts are more susceptible to this phenomenon. Despite false high pressure measurements, stent-graft-attached pressure sensors seem appropriate to follow pressure trends in the aneurysm sac.
authors.affiliation: Department of Surgery, Section Vascular Surgery, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Jan-Willem
authors.initials: JW
authors.lastname: Hinnen
authors.forename: Olivier H J
authors.initials: OH
authors.lastname: Koning
authors.forename: Ester
authors.initials: E
authors.lastname: Vlaanderen
authors.forename: J Hajo
authors.initials: JH
authors.lastname: van Bockel
authors.forename: Jaap F
authors.initials: JF
authors.lastname: Hamming
mesh_terms: D000704:Analysis of Variance; D017544:Aortic Aneurysm, Abdominal / Q000503:physiopathology* / Q000601:surgery; D001794:Blood Pressure; D001807:Blood Vessel Prosthesis; D006801:Humans; D066298:In Vitro Techniques; D009038:Motion; D011673:Pulsatile Flow; D012815:Signal Processing, Computer-Assisted; D015607:Stents