Development of a fully implantable wireless pressure monitoring system Robert Tan & Timothy McClure & C. K. Lin & David Jea & Foad Dabiri & Tammara Massey & Majid Sarrafzadeh & Mani Srivastava & C. D. Montemagno & Peter Schulam & Jacob Schmidt Published online: 3 October 2008 # Springer Science + Business Media, LLC 2008 Abstract A fully implantable wireless pressure sensor system was developed to monitor bladder pressures in vivo. The system comprises a small commercial pressure die connected via catheter to amplifying electronics, a microcontroller, wireless transmitter, battery, and a personal digital assistant (PDA) or computer to receive the wireless data. The sensor is fully implantable and transmits pressure data once every second with a pressure detection range of 1.5 psi gauge and a resolution of 0.02 psi. In vitro calibration measurements of the device showed a high degree of linearity and excellent temporal response. The implanted device performed continuously in vivo in several porcine studies lasting over 3 days. This system can be adapted for other pressure readings, as well as other vital sign measurements; it represents the first step in developing a ubiquitous sensing platform for telemedicine and remote patient monitoring. Keywords MEMS . Pressure sensor . Implantable . Patient monitoring . Telemetry . Telemedicine . Bladder . Wireless 1 Introduction There has been significant interest in the medical commu- nity in telemedicine and remote patient monitoring at home and in the hospital (Field and Grigsby 2002). Current patient monitoring instrumentation and practices can be cumbersome and restrictive. For example, in the intensive care unit, blood pressure monitoring can be monitored continuously with an arterial line. This is a catheter that is placed in the artery, and an external transducer detects the pressure. The limitations of this are that the accuracy is highly variable, and the patient is often sedated to prevent him from injuring himself from movement. On the other hand, in standard floor care, while completely non-invasive and burden-free to the patient, standard blood pressure measurements with a cuff are non-continuous point meas- urements typically taken every 2–12 h. The development of critical vital signs between measurements could be missed. Currently, there is no device which provides clinicians with continuous monitoring of vital signs without being ex- tremely invasive and/or cumbersome. A device capable of continuous and real time measure- ment and monitoring without significantly reducing the patient’ s comfort or restricting his movement would fill the gaps in performance and comfort between intensive and standard care. A simple and cost effective solution is to utilize implantable microsystems utilizing wireless teleme- try. Wireless telemetry frees the patient from being tethered to large hospital monitors and can participate in a hospital sensor network, which could increase monitoring efficiency Biomed Microdevices (2009) 11:259–264 DOI 10.1007/s10544-008-9232-1 R. Tan : C. K. Lin : J. Schmidt (*) Department of Bioengineering, University of California, Los Angeles, CA 90095, USA e-mail: schmidt@seas.ucla.edu T. McClure : P. Schulam Department of Urology, University of California, Los Angeles, CA 90095, USA D. Jea : M. Srivastava Department of Electrical Engineering, University of California, Los Angeles, CA 90095, USA F. Dabiri : T. Massey : M. Sarrafzadeh Department of Computer Science, University of California, Los Angeles, CA 90095, USA C. D. Montemagno College of Engineering, University of Cincinnati, Cincinnati, OH 45221, USA