title: Comparison of air-charged and water-filled urodynamic pressure measurement catheters.
abstract: OBJECTIVE
  Catheter systems are utilized to measure pressure for diagnosis of voiding dysfunction. In a clinical setting, patient movement and urodynamic pumps introduce hydrostatic and motion artifacts into measurements. Therefore, complete characterization of a catheter system includes its response to artifacts as well its frequency response. The objective of this study was to compare the response of two disposable clinical catheter systems: water-filled and air-charged, to controlled pressure signals to assess their similarities and differences in pressure transduction.
  
  
  METHODS
  We characterized frequency response using a transient step test, which exposed the catheters to a sudden change in pressure; and a sinusoidal frequency sweep test, which exposed the catheters to a sinusoidal pressure wave from 1 to 30 Hz. The response of the catheters to motion artifacts was tested using a vortex and the response to hydrostatic pressure changes was tested by moving the catheter tips to calibrated heights.
  
  
  RESULTS
  Water-filled catheters acted as an underdamped system, resonating at 10.13 ± 1.03 Hz and attenuating signals at frequencies higher than 19 Hz. They demonstrated significant motion and hydrostatic artifacts. Air-charged catheters acted as an overdamped system and attenuated signals at frequencies higher than 3.02 ± 0.13 Hz. They demonstrated significantly less motion and hydrostatic artifacts than water-filled catheters. The transient step and frequency sweep tests gave comparable results.
  
  
  CONCLUSIONS
  Air-charged and water-filled catheters respond to pressure changes in dramatically different ways. Knowledge of the characteristics of the pressure-measuring system is essential to finding the best match for a specific application.
authors.affiliation: Advanced Platform Technology Center, Louis Stokes Veterans Affairs Medical Center, Cleveland, Ohio, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Cooper
authors.forename: P C
authors.initials: PC
authors.lastname: Fletter
authors.forename: P J
authors.initials: PJ
authors.lastname: Zaszczurynski
authors.forename: M S
authors.initials: MS
authors.lastname: Damaser
mesh_terms: D000388:Air; D016477:Artifacts; D057785:Catheters; D004209:Disposable Equipment; D004867:Equipment Design; D006874:Hydrostatic Pressure; D008422:Materials Testing; D009038:Motion; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D014160:Transducers, Pressure; D014546:Urinary Catheterization / Q000295:instrumentation*; D014563:Urodynamics; D014867:Water
chemical_list: D014867:Water