Feasibility of Real-Time Conditional Sacral Neuromodulation Using Wireless Bladder Pressure Sensor

Can we improve techniques and patients' selection for nerve stimulation suitable for lower urinary tract dysfunctions? ICI-RS 2023

AIMS

Lower urinary tract dysfunctions (LUTD) are very common and, importantly, affect patients' quality of life (QoL). LUTD can range from urinary retention to urgency incontinence and includes a variety of symptoms. Nerve stimulation (NS) is an accepted widespread treatment with documented success for LUTD and is used widely. The aim of this review is to report the results of the discussion about how to improve the outcomes of NS for LUTD treatment.

METHODS

During its 2023 meeting in Bristol, the International Consultation on Incontinence Research Society discussed a literature review, and there was an expert consensus discussion focused on the emerging awareness of NS suitable for LUTD.

RESULTS

The consensus discussed how to improve techniques and patients' selection in NS, and high-priority research questions were identified.

CONCLUSIONS

Technique improvement, device programming, and patient selection are the goals of the current approach to NS. The conditional nerve stimulation with minimally invasive wireless systems and tailored algorithms hold promise for improving NS for LUTD, particularly for patients with neurogenic bladder who represent the new extended population to be treated.

Transcutaneous neuromodulation versus oxybutynin for neurogenic detrusor overactivity in persons with spinal cord injury: A randomized, investigator blinded, parallel group, non-inferiority controlled trial

STUDY DESIGN

This study is a randomized, investigator-blinded, controlled trial with a non-inferiority design.

OBJECTIVE

To investigate the effectiveness of neuromodulation by transcutaneous electrical stimulation of the somatic afferent nerves of the foot in neurogenic detrusor overactivity (NDO) in persons with spinal cord injury (SCI) and compare its effectiveness with oral oxybutynin.

SETTING

The study was conducted in a rehabilitation in-patient ward of a tertiary care hospital.

METHODS

Twenty-nine persons with SCI with NDO, either sex, aged 18 years and above were randomized into two groups, one group receiving oral oxybutynin (5 mg thrice a day for two weeks) and the other transcutaneous electrical stimulation (5 Hz, 200 µs pulse, biphasic, amplitude up to 60 mA, 30 min/day for two weeks). Bladder capacity was evaluated by clinical bladder evaluation (i.e. bladder capacity measured by adding leak volume, voiding volume if any, and post-void residue using a catheter) and cystometric bladder capacity by one-channel cystometry. Maximum cystometric pressure was evaluated by one-channel water cystometry. Data were analyzed with Fisher's Exact, t-test, and Wilcoxon rank sum tests.

RESULTS

Bladder capacity improved significantly in the oxybutynin and neuromodulation groups as measured by one-channel water cystometry (136 ml vs. 120.57 ml) and clinical evaluation (138.93 ml vs. 112 ml). The increase in the neuromodulation group achieved the pre-decided non-inferiority margin of 30 ml over the oxybutynin group when measured by one-channel water cystometry but not by clinical evaluation. Maximum cystometric pressure did not significantly improve in either group when compared with the baseline.

CONCLUSION

Transcutaneous neuromodulation and oxybutynin effectively increased bladder capacity in persons with SCI with NDO. Neuromodulation by once-a-day transcutaneous electrical stimulation was non-inferior to thrice-a-day oxybutynin when evaluated by one-channel water cystometry.Trial registration: Clinical Trials Registry India identifier: CTRI/2018/05/013735.

From wires to waves, a novel sensor system for in vivo pressure monitoring

Pressure monitoring in various organs of the body is essential for appropriate diagnostic and therapeutic purposes. In almost all situations, monitoring is performed in a hospital setting. Technological advances not only promise to improve clinical pressure monitoring systems, but also engage toward the development of fully implantable systems in ambulatory patients. Such systems would not only provide longitudinal time monitoring to healthcare personnel, but also to the patient who could adjust their way-of-life in response to the measurements. In the past years, we have developed a new type of piezoresistive pressure sensor system. Different bench tests have demonstrated that it delivers precise and reliable pressure measurements in real-time. The potential of this system was confirmed by a continuous recording in a patient that lasted for almost a day. In the present study, we further characterized the functionality of this sensor system by conducting in vivo implantation experiments in nine female farm pigs. To get a step closer to a fully implantable system, we also adapted two different wireless communication solutions to the sensor system. The communication protocols are based on MICS (Medical Implant Communication System) and BLE (Bluetooth Low Energy) communication. As a proof-of-concept, implantation experiments in nine female pigs demonstrated the functionality of both systems, with a notable technical superiority of the BLE.

Wireless and Catheter-Free Bladder Pressure and Volume Sensor

Continuous monitoring of bladder activity during normal daily activities would improve clinical diagnostics and understanding of the mechanisms underlying bladder function, or help validate how differing neuromodulation strategies affect the bladder. This work describes a urological monitor of conscious activity (UroMOCA). The UroMOCA included a pressure sensor, urine impedance-sensing electrodes, and wireless battery recharge and data transmission circuitry. Components were assembled on a circuit board and encapsulated with an epoxy/silicone molded package that allowed Pt-Ir electrode feedthrough for urine contact. Packaged UroMOCAs measured 12 × 18 × 6 mm. UroMOCAs continuously transmitted data from all onboard sensors at 10 Hz at 30 cm range, and ran for up to 44 hours between wireless recharges. After in vitro calibration, implantations were performed in 11 animals. Animals carried the device for 28 days, enabling many observations of bladder behavior during natural, conscious behavior. In vivo testing confirmed the UroMOCA did not impact bladder function after a two-week healing period. Pressure data in vivo were highly correlated to a reference catheter used during an anesthetized follow-up. Static volume sensor data were less accurate, but demonstrated reliable detection of bladder volume decreases, and distinguished between voiding and non-voiding bladder events.

Real-time prediction of bladder urine leakage using fuzzy inference system and dual Kalman filtering in cats

The use of electrical stimulation devices to manage bladder incontinence relies on the application of continuous inhibitory stimulation. However, continuous stimulation can result in tissue fatigue and increased delivered charge. Here, we employ a real-time algorithm to provide a short-time prediction of urine leakage using the high-resolution power spectrum of the bladder pressure during the presence of non-voiding contractions (NVC) in normal and overactive bladder (OAB) cats. The proposed method is threshold-free and does not require pre-training. The analysis revealed that there is a significant difference between voiding contraction (VC) and NVC pressures as well as band powers (0.5-5 Hz) during both normal and OAB conditions. Also, most of the first leakage points occurred after the maximum VC pressure, while all of them were observed subsequent to the maximum VC spectral power. Kalman-Fuzzy method predicted urine leakage on average 2.2 s and 1.6 s before its occurrence and an average of 2.0 s and 1.1 s after the contraction started with success rates of 94.2% and 100% in normal and OAB cats, respectively. This work presents a promising approach for developing a neuroprosthesis device, with on-demand stimulation to control bladder incontinence.

Catheter-Free Urodynamics Testing: Current Insights and Clinical Potential

Lower urinary tract dysfunction not only interferes with the health-related quality of life of patients but may also lead to acute kidney injury and infections. To assess the bladder, urodynamic studies (UDS) have been implemented but the use of catheters leads to discomfort for the patient. Catheter-free long-term UDS would be useful and a potential solution could be ambulatory wireless devices that communicate via telemetry. Such sensors can detect pressure or volume. Numerous types of potential catheter-free sensors have been proposed for bladder monitoring. Despite substantial innovation in the manufacturing of implantable biomedical electronic systems, such sensors have remained at the laboratory stage due to a number of critical challenges. These challenges primarily concern hermeticity and biocompatibility, sensitivity and artifacts, drift, telemetry, and energy management. Having overcome these challenges, catheter-free ambulatory urodynamic monitoring could combine a synchronized intravesical pressure sensor with a volume analyzer but only the steps of cystometry and volume measurement are currently sufficiently reproducible to simulate UDS results. The measurement of volume by infrared optical sensors, in the form of abdominal patches, appears to be promising and studies are underway to market a telemetric ambulatory urodynamic monitoring system that includes an intravesical pressure sensor. There has been considerable progress in wearable and conformable electronics on many fronts, and continued collaboration between engineers and urologists could quickly overcome current challenges. In addition, to the diagnosis of UDS, such sensors could be useful in the development of a long-term closed-loop neuromodulation system. In this review, we explore the various types of catheter-free bladder sensors, inherent challenges and solutions to overcome these challenges, and the clinical potential of such long-term implantable sensors.