Drift compensation for implanted capacitance-based pressure transducer
First Claim
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1. A method for ambient pressure measurement, the method comprising:
- sensing, in a heart of a patient, a time-varying ambient pressure that varies in accordance with a cardiac cycle of the heart, using a pressure sensor having a capacitance that varies depending on the time-varying ambient pressure, so as to produce a sensor-output waveform that also varies in accordance with the cardiac cycle;
while the pressure sensor is measuring the time-varying ambient pressure in the heart, intermittently applying to the pressure sensor a calibration voltage, which further contributes to the capacitance in addition to a contribution of the time-varying ambient pressure;
automatically identifying one or more first time-intervals in which the calibration voltage was applied and one or more second time-intervals in which the calibration voltage was not applied;
comparing the sensor-output waveform during the one or more first time-intervals to the sensor-output waveform during the one or more second time-intervals, to determine a difference between the sensed pressure in the first and second time-intervals;
calibrating a dependence of the capacitance on the ambient pressure, based on the applied calibration voltage and the corresponding determined difference between the sensed pressure in the first and second time-intervals; and
outputting an output indicative of a calibrated ambient pressure, based on the calibrated dependence.
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Abstract
A method includes, in a living organ (28) in which an ambient pressure varies as a function of time, sensing the ambient pressure using a pressure sensor (36, 90, 174), which has a capacitance that varies in response to the ambient pressure, so as to produce a time-varying waveform. A calibration voltage, which modifies the capacitance and thus the time-varying waveform, is applied to the pressure sensor. The time-varying waveform is processed so as to isolate and measure a contribution of the calibration voltage to the waveform. A dependence of the capacitance on the ambient pressure is calibrated using the measured contribution of the calibration voltage.
147 Citations
31 Claims
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1. A method for ambient pressure measurement, the method comprising:
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sensing, in a heart of a patient, a time-varying ambient pressure that varies in accordance with a cardiac cycle of the heart, using a pressure sensor having a capacitance that varies depending on the time-varying ambient pressure, so as to produce a sensor-output waveform that also varies in accordance with the cardiac cycle; while the pressure sensor is measuring the time-varying ambient pressure in the heart, intermittently applying to the pressure sensor a calibration voltage, which further contributes to the capacitance in addition to a contribution of the time-varying ambient pressure; automatically identifying one or more first time-intervals in which the calibration voltage was applied and one or more second time-intervals in which the calibration voltage was not applied; comparing the sensor-output waveform during the one or more first time-intervals to the sensor-output waveform during the one or more second time-intervals, to determine a difference between the sensed pressure in the first and second time-intervals; calibrating a dependence of the capacitance on the ambient pressure, based on the applied calibration voltage and the corresponding determined difference between the sensed pressure in the first and second time-intervals; and outputting an output indicative of a calibrated ambient pressure, based on the calibrated dependence. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An apparatus for ambient pressure measurement, the apparatus comprising:
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a pressure sensor, which is configured to be fitted in a heart of a patient, and to sense in the heart a time-varying ambient pressure that varies in accordance with a cardiac cycle of the heart, the pressure sensor having a capacitance that varies depending on the time-varying ambient pressure, so as to produce a sensor-output waveform that also varies in accordance with the cardiac cycle; an integrated circuit (IC), which is coupled to the pressure sensor and in configured to intermittently apply to the pressure sensor, while the pressure sensor is measuring the time-varying ambient pressure in the heart, a calibration voltage that further contributes to the capacitance in addition to a contribution of the time-varying ambient pressure; and a processor, which is configured to; automatically identify one or more first time-intervals in which the calibration voltage was applied and one or more second time-intervals in which the calibration voltage was not applied; compare the sensor-output waveform during the one or more first time-intervals to the sensor-output waveform during the one or more second time-intervals, to determine a difference between the sensed pressure in the first and second time-intervals; calibrate a dependence of the capacitance on the ambient pressure, based on the applied calibration voltage and the corresponding determined difference between the sensed pressure in the first and second time-intervals; and output an output indicative of a calibrated ambient pressure, based on the calibrated dependence. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification