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Abstract

An apparatus and method for obtaining pressure data using a body implantable pressure sensor includes a measurement capacitor which is responsive to pressure changes of a body fluid. Non-constant, multiple current source charging of the measurement capacitor provides for a significant increase in sensitivity to conditions of pressure of a body fluid. Pressure data is obtained by charging the measurement capacitor at a first charge rate during a first charge period of an integration cycle and, during a second charge period of the integration cycle, charging the measurement capacitor at a second charge rate. The first charge rate is preferably greater than the second charge rate. The duration of the first and second charge periods may be varied. A signal indicative of a pressure change of a body fluid imparted to the measurement capacitor is produced by the pressure sensor. The signal may be a signal indicative of a change in a time of integration. The signal, indicative of a time of integration, has a sensitivity to pressure changes which is greater than a mechanical capacitive sensitivity of the measurement capacitor to such pressure changes. The signal may alternatively be a signal indicative of a change in capacitance of the measurement capacitor, such as a voltage signal, or a signal having a duty cycle indicative of the pressure change. The pressure sensor may be implemented in a pacemaker, a pacemaker/cardioverter/defibrillator (PCD) or a hemodynamic monitor.

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