Wireless, Ultra-Low-Power Implantable Sensor for Chronic Bladder Pressure Monitoring

Abstract

The wireless implantable/intracavity micromanometer (WIMM) system was designed to fulfill the unmet need for a chronic bladder pressure sensing device in urological fields such as urodynamics for diagnosis and neuromodulation for bladder control. Neuromodulation in particular would benefit from a wireless bladder pressure sensor which could provide real-time pressure feedback to an implanted stimulator, resulting in greater bladder capacity while using less power. The WIMM uses custom integrated circuitry, a MEMS transducer, and a wireless antenna to transmit pressure telemetry at a rate of 10 Hz. Aggressive power management techniques yield an average current draw of 9 A from a 3.6-Volt micro-battery, which minimizes the implant size. Automatic pressure offset cancellation circuits maximize the sensing dynamic range to account for drifting pressure offset due to environmental factors, and a custom telemetry protocol allows transmission with minimum overhead. Wireless operation of the WIMM has demonstrated that the external receiver can receive the telemetry packets, and the low power consumption allows for at least 24 hours of operation with a 4-hour wireless recharge session.

Suburothelial Bladder Contraction Detection with Implanted Pressure Sensor

“…Measured sensor parameters previously reported [19;20] are omitted here for brevity, but are summarized in Table 1. The pressure sensitivity and function of prototype devices were calibrated just prior to implantation.…”

“…In this new sensing modality there is a chance that localized detrusor contractions, changes in abdominal pressure, or rapid motion could create pressure artifacts superimposed on measured intravesical pressure, and so this study aims to evaluate the in vivo accuracy of our catheter-free pressure sensor [19;20] in the suburothelial location in several animals, using a wired pressure monitor prototype (Fig 1). We chose to use a wired prototype in these studies to focus on device validation, and to investigate the potentially deleterious effects of tethering the detrusor with a wired, submucosal implant.…”

Chronically Implanted Pressure Sensors: Challenges and State of the Field

“…In addition, measurements are plagued by catheterization, such as disturbances along the catheter line and different resonance and response time delays due to fluid inertia. For chronic monitoring, these catheter-type devices are not viable as they are prone to infection and stone formation within the bladder [ 108 ].…”

“…The addition of temperature data may assist the calibration of sensor response in the in vivo environment. Efforts to improve the chronic performance of these sensors make use of an on-board temperature compensation circuit [ 42 , 108 , 121 ] or external signal processing circuitry [ 89 , 118 ]. Appropriate material selection for certain sensing modalities such as SAW type transducers allow for the use of temperature-insensitive quartz, which circumvents the need for compensation [ 121 , 122 ].…”

Nano Size Related Piezoelectric Efficiency in a Large ZnO Thin Film, Potential for Self-Powered Medical Device Application

“…In vivo sensors have a wide application for real-time biomedical monitoring [1]. Single-use or non-rechargeable batteries to support implanted device limits the application of those promising implanted sensors, because of requiring to be surgically replaced at the end.…”