Impedance measurement and demodulation using implantable device

摘要

An implantable medical device performs impedance measurement and demodulation, such as for obtaining lead impedance measurements, or thoracic impedance measurements, such as for extracting respiration, cardiac stroke, or fluid status information. A 4-point FIR filter demodulator can be used to demodulate a two-phase current excitation waveform. The demodulator can also be used to measure noise for triggering a noise response. Among other things, an increased excitation current level can be used when noise is deemed to be present.

主权项

1. An apparatus comprising:
an implantable impedance measurement circuit, configured to be communicatively coupled to a plurality of implantable electrodes, wherein the impedance measurement circuit includes:
an exciter circuit, configured to apply a test current between at least two of the electrodes;a preamplifier circuit, configured to sense the voltage response to the test current;a demodulator circuit, communicatively coupled to the preamplifier circuit, wherein the demodulator circuit includes a four-point finite impulse response (FIR) filter; and wherein the impedance measurement circuit is configured to determine an impedance measurement between the electrodes using the demodulated sensed voltage response, wherein the exciter circuit is configured to apply a two-phase test current that is limited to two-phases per demodulation, and wherein the demodulator circuit is configured to demodulate the sensed voltage response to the two-phase test current using the four-point FIR filter.