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Method and apparatus for noninvasively determining hematocrit

  • US 5,642,734 A
  • Filed: 02/16/1996
  • Issued: 07/01/1997
  • Est. Priority Date: 10/04/1990
  • Status: Expired due to Term
First Claim
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1. A system for noninvasive determination of hematocrit of blood in a body portion of a patient, the system comprising:

  • signal generation circuitry to produce alternating and quadrature signals at various frequencies;

    processing, sensing, and application circuitry to provide current signals through the body portion in response to the alternating signals, and to sense the current signals being applied and produce current indicating signals in response thereto, and to sense voltage signals over a section of the body portion and produce voltage indicating signals in response thereto;

    processing and demodulation circuitry to receive and mix the current indicating signals and the alternating and quadrature signals to produce inphase and quadrature current representing signals, and to receive the voltage indicating signals and mix the voltage indicating signals and the alternating and quadrature signals to produce inphase and quadrature voltage representing signals; and

    evaluation circuitry to receive and process the inphase and quadrature current representing signals and inphase and quadrature voltage representing signals to determine the hematocrit.

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