title: Feasibility of fluid volume conductance to assess bladder volume.
abstract: OBJECTIVE
  Ambulatory urodynamics has the potential to provide measurements of bladder function during activities of daily living; however, no method of real-time continuous bladder volume measurement exists. The present study was conducted to determine the feasibility of using fluid volume conductance to continuously assess bladder volume.
  
  
  METHODS
  Prototype devices consisted of four electrodes mounted on a polymer body. Each was tested in an in vitro organ bath system using latex vessels filled to 500 ml with saline matching the conductivity of urine. One device was selected and used to test the effects of fluid concentration (25%, 50%, 100%, 200%, and 400% physiological saline) in latex vessels as well as the effects of fluid concentration (25%, 50%, 100%, 200%, and 400% Tyrodes solution) and temperature (32, 37, and 42 degrees C) in excised pig bladders.
  
  
  RESULTS
  Conductance demonstrated a linear increase at low volumes but approached an asymptotic value at high volumes. Conductivity increased with increased temperature or concentration. With the exception of the differences between 25% and 50% concentrations, 32 degrees C and 37 degrees C, and 37 degrees C and 42 degrees C temperatures, each concentration and temperature produced statistically different conductance measurements from all others.
  
  
  CONCLUSIONS
  The conductance method is sensitive to changes in both concentration and temperature of the intravesical solution, likely due to changes in solution conductivity. Clinical application of conductance for measurement of bladder volume will require real-time conductivity compensation for the dynamically varying properties of urine. However, improved sensitivity at high volumes is necessary before this method has the potential to provide real-time bladder volume measurement for use in ambulatory urodynamics.
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA.
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Gill
authors.forename: Paul C
authors.initials: PC
authors.lastname: Fletter
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Zaszczurynski
authors.forename: Alfred
authors.initials: A
authors.lastname: Perlin
authors.forename: Daniel
authors.initials: D
authors.lastname: Yachia
authors.forename: Margot S
authors.initials: MS
authors.lastname: Damaser
mesh_terms: D000203:Activities of Daily Living; D000818:Animals; D004553:Electric Conductivity; D004566:Electrodes; D004867:Equipment Design; D005240:Feasibility Studies; D066298:In Vitro Techniques; D008422:Materials Testing; D018670:Monitoring, Ambulatory / Q000295:instrumentation / Q000379:methods; D009929:Organ Size; D009994:Osmolar Concentration; D011312:Pressure; D015203:Reproducibility of Results; D013552:Swine; D013696:Temperature; D001743:Urinary Bladder / Q000033:anatomy & histology* / Q000502:physiology; D014563:Urodynamics