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Methods and apparatus for determining cardiac output

  • US 9,289,133 B2
  • Filed: 10/13/2010
  • Issued: 03/22/2016
  • Est. Priority Date: 02/10/2003
  • Status: Active Grant
First Claim
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1. A method for determining cardiac output to within a constant scale factor, comprising:

  • measuring a physiological signal of a patient using a sensor, the physiological signal indicative of cardiovascular system activity and measured over a plurality of cardiac cycles;

    determining, from the physiological signal, beat-to-beat variability of the physiological signal across multiple cardiac beats;

    determining cardiac output to within a constant scale factor using the beat-to-beat variability information extracted from the physiological signal; and

    presenting the cardiac output on a display of a computing device;

    wherein determining beat-to-beat variability includesconstructing a cardiac contractions timing signal from the physiological signal by forming an impulse train in which each impulse is located at the onset of upstroke of each pulse;

    determining an impulse response, which when convolved with the cardiac contractions timing signal, fits the physiological signal;

    determining a time constant by fitting an exponential function to a tail end of the impulse response; and

    determining cardiac output to within a constant scale factor using the time constant.

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