SPARC: Catheter‐Free Wireless Measurement of Feline Bladder Pressures Using Intravesical Sensor

Abstract

Introduction and ObjectiveIn research animal models, catheterization for cystometry requires anesthesia which affects neuro‐urological pathways, or animal restraint, limiting measurement time and social behaviors surrounding natural bladder filling and micturition. To overcome this, we developed a catheter‐free, wireless, intravesical pressure sensor for use in conscious, untethered felines. This study validated sensor function and physiologic outcomes over 4‐week implantations, including (to our knowledge) the first untethered catheter‐free wireless recordings of bladder pressure during bladder filling and voiding.MethodsSensor performance was first validated on the bench. Sensors were then encapsulated in layers of medical epoxy and silicone and sterilized by ethylene oxide gas prior to implantation. Implantations were performed on 6 male felines: 2 were sham (no device), 2 implants were inactive devices, and 2 used active devices measuring 18 mm × 12 mm × 5.6 mm. Devices were implanted into the bladder lumen through a 10‐cm detrusor incision, which was stretched on insertion and then sutured. Anesthetized cystometry and urine collection was performed immediately before and after surgery, and at 2 and 4 weeks after implantation. Conscious data collection and behavioral video recordings were performed 3 times/week. Data collection used a small animal‐worn radio harness which received sensor transmissions and logged data to a MicroSD card. Devices were explanted after 4 weeks.ResultsAll animals showed a similar decrease in bladder capacity following surgery (sham surgery and implant). All devices remained patent without obstructing the bladder for 4 weeks; one device stopped transmitting at 12 days and one worked through 4 weeks. Wireless pressure data was linearly correlated with spontaneous reflex contractions during anesthetized urodynamics (R2 = 0.96). Conscious data recording was performed on 11 occasions, producing over 200 minutes of catheter‐free pressure recordings. Animals entered and used litter boxes freely while data were recorded to the radio harness. Recorded pressures during voiding were confirmed against simultaneous video recording.ConclusionsSmall wireless, intravesical sensors permitted catheter‐free recordings of bladder pressure in felines for 30 days, including voluntary voiding contractions. Translation of this technology could enable urethrally‐inserted sensors for catheter‐free, wireless ambulatory urodynamics over longer time periods than is feasible with catheters.Support or Funding InformationThis work was funded by the NIH Stimulating Peripheral Activity to Relieve Conditions (SPARC) program, NIH grant number OT2OD023873.