title: Evaluation of a modified piezoresistive technique and a water-capsule technique for direct and continuous measurement of intra-abdominal pressure in a porcine model.
abstract: OBJECTIVE
  Intravesical pressure measurement is considered to be the gold standard for the assessment of intra-abdominal pressure. However, this method is indirect and depends on a physiologic bladder function. We evaluated a modified piezoresistive technique and a water-capsule technique for direct and continuous intra-abdominal pressure measurement.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Animal research laboratory.
  
  
  METHODS
  Eleven male domestic pigs.
  
  
  METHODS
  In anesthetized and mechanically ventilated animals, CO2 was insufflated to stepwise increase the intra-abdominal pressure to 30 mm Hg. Pressure was then held constant for 9 hrs followed by decompression. Piezoresistive measurement and water-capsule measurement probes were placed intra-abdominally.
  
  
  RESULTS
  Readings of intravesical pressure measurement, piezoresistive measurement, and water-capsule measurement were taken hourly. Mean difference to insufflator readings, confidence intervals, and limits of agreement were calculated. Differences between applied pressure and intra-abdominal pressure readings were assessed using a two-factor analysis of variance. No significant differences between methods could be observed. During stepwise pressure increase, limits of agreements were -3.6 to 3.6 mm Hg. Confidence intervals were -3.4 to 3.5 (intravesical pressure measurement), -1.6 to 1.5 (piezoresistive measurement), and 0.5 to 2.9 mm Hg (water-capsule measurement). In the presence of constantly elevated intra-abdominal pressure, limits of agreement ranged from -8.2 to +8.2 mm Hg. Confidence intervals were -0.4 to 6.2 (intravesical pressure measurement), -0.2 to 2.7 (piezoresistive measurement), and 1.1 to 5.1 mm Hg (water-capsule measurement).
  
  
  CONCLUSIONS
  Both piezoresistive measurement and water-capsule measurement had smaller confidence intervals than intravesical pressure measurement, indicating higher precision, whereas water-capsule measurement had a significant offset. Piezoresistive measurement could be the most suitable device for continuous direct intra-abdominal pressure monitoring in specific patients.
authors.affiliation: Department of Surgery, Technical University of Aachen, and Department, of Visceral and Thoracic Surgery, Central Hospital of the German Armed Forces, Koblenz, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Schachtrupp
authors.forename: Dietrich
authors.initials: D
authors.lastname: Henzler
authors.forename: Sandra
authors.initials: S
authors.lastname: Orfao
authors.forename: Werner
authors.initials: W
authors.lastname: Schaefer
authors.forename: Robert
authors.initials: R
authors.lastname: Schwab
authors.forename: Peter
authors.initials: P
authors.lastname: Becker
authors.forename: Volker
authors.initials: V
authors.lastname: Schumpelick
mesh_terms: D000005:Abdomen; D000704:Analysis of Variance; D000818:Animals; D003161:Compartment Syndromes / Q000175:diagnosis*; D016001:Confidence Intervals; D008297:Male; D008365:Manometry / Q000295:instrumentation*; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D015203:Reproducibility of Results; D013552:Swine; D014160:Transducers, Pressure