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Method and apparatus to measure bioelectric impedance of patient tissue

  • US 8,412,317 B2
  • Filed: 04/20/2009
  • Issued: 04/02/2013
  • Est. Priority Date: 04/18/2008
  • Status: Active Grant
First Claim
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1. A device for measuring an impedance of a tissue of a patient, the device comprising:

  • calibration circuitry comprising an impedance;

    at least four electrodes configured to couple to the tissue of the patient, the at least four electrodes comprising at least two measurement electrodes and at least two drive electrodes;

    drive circuitry coupled to the at least two drive electrodes and the calibration circuitry to pass a current through the tissue and the calibration circuitry simultaneously, the drive circuitry configured to increase the current from a first current amount at a first frequency to a second current amount at a second frequency, the second frequency greater than the first frequency;

    measurement circuitry configured to couple to the at least two measurement electrodes and the calibration circuitry, the measurement circuitry configured to measure a calibration signal from the calibration circuitry and a tissue impedance signal from the at least two measurement electrodes; and

    processor circuitry comprising a tangible medium configured to determine the impedance of the tissue in response to the calibration signal and the tissue impedance signal.

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