CA2188926A1 - Implantable Capacitive Absolute Pressure and Temperature Sensor - Google Patents

Abstract

An endocardial lead (12) for implantation in a right heart chamber (RV) for responding to blood pressure and temperature and providing modulated pressure and temperature related signals to an implanted or external hemodynamic monitor (100) and/or cardiac pacemaker or pacemacker/cardioverter/defibrilator. The lead (12) has a sensor module (20) formed in its distal end and is coupled to a monitor (100) that powers a sensor circuit in the sensor module. The sensor module is formed with a pickoff capacitor (Cp) that changes capacitance with pressure changes and a reference capacitor (Cp) that is relatively insensitive to pressure changes. The sensor circuit provides charge current that changes with temperature variation at the implant site, alternately charges and discharges the two capacitors, and provides timing pulses having distinguishable parameters at the end of each charge cycle that are transmitted to a demodulator (150). The demodulator (150) detects and synchronizes the timing pulses and derives pressure and temperature analog voltage values representative of the intervals between the timing pulses which are digitized and stored in the monitor. The monitor may also be coupled with other sensors (106, 152) for measuring and storing related patient body parameters, e.g. blood gas, ECG, and patient activity.