Prolonged reflux monitoring: Capabilities of bravo pH and impedance-pH systems

BioMEMS for biosensors and closed-loop drug delivery

The efficacy of pharmaceutical treatments can be greatly enhanced by physiological feedback from the patient using biosensors, though this is often invasive or infeasible. By adapting microelectromechanical systems (MEMS) technology to miniaturize such biosensors, previously inaccessible signals can be obtained, often from inside the patient. This is enabled by the device's extremely small footprint which minimizes both power consumption and implantation trauma, as well as the transport time for chemical analytes, in turn decreasing the sensor's response time. MEMS fabrication also allows mass production which can be easily scaled without sacrificing its high reproducibility and reliability, and allows seamless integration with control circuitry and telemetry which is already produced using the same materials and fabrication steps. By integrating these systems with drug delivery devices, many of which are also MEMS-based, closed loop drug delivery can be achieved. This paper surveys the types of signal transduction devices available for biosensing-primarily electrochemical, optical, and mechanical-looking at their implementation via MEMS technology. The impact of MEMS technology on the challenges of biosensor development, particularly safety, power consumption, degradation, fouling, and foreign body response, are also discussed.

Batteryless implantable dual-sensor capsule for esophageal reflux monitoring

BACKGROUND

Chronic GERD affects approximately 15% of adults in the United States and is one of the most prevalent clinical conditions involving the GI tract. The commercial tools for monitoring GERD include multichannel intraluminal impedance (MII) probes and pH-sensing capsules. However, MII probes cause discomfort, which alters patients' regular activities, whereas the pH-sensing capsule lacks the ability to detect weak or nonacid episodes, misses reflux episodes with similar pH values, and has a limited sampling rate and battery life.

OBJECTIVE

To develop and test an implantable batteryless dual-sensor capsule that can be used to diagnose and monitor GERD.

DESIGN

The implanted capsule is wirelessly powered by an external device. Simulated reflux episodes were created in 3 live porcine models. Impedance and pH data were continuously measured and recorded.

INTERVENTION

The implant capsule was placed in the esophagus along with a commercial pH-sensing capsule for comparison.

MAIN OUTCOME MEASUREMENTS

Precise impedance and pH readouts were obtained and compared with those from a commercial pH-sensing capsule.

RESULTS

The wireless energy supplied by the external unit was strong enough to power the implant. The pH sensor accurately measured pH levels and the impedance sensor precisely located the reflux episodes.

LIMITATION

Simulated reflux events in a pig model.

CONCLUSION

Our wireless sensors are reliable in operation and provide accurate assessment of simulated reflux episodes. The entire device can potentially be used to diagnose and monitor GERD.