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Impedance cardiograph and method of operation utilizing peak aligned ensemble averaging

  • US 5,178,154 A
  • Filed: 09/18/1990
  • Issued: 01/12/1993
  • Est. Priority Date: 09/18/1990
  • Status: Expired due to Term
First Claim
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1. An impedance cardiograph comprising:

  • means for applying an excitation signal to the thorax of an animal;

    means, responsive to the excitation signal, for producing a first electrical signal which varies with thoracic impedance changes of the animal;

    means for producing a second electrical signal that corresponds to the first derivative of the first electrical signal;

    means for generating a plurality of periodic samples of the second electrical signal, the samples being divided into a number of groups with the samples in each group representing the second electrical signal during a different cardiac cycle of the animal;

    means for identifying a signal sample in each group which occurs during a cardiac ejection interval and which corresponds to the smallest rate of change of the thoracic impedance;

    means for ensemble averaging the groups of the samples of the second electrical signal to produce a set of ensemble averaged signal samples, said means for ensemble averaging aligning each group of samples of the second electrical signal about a sample in each group which occurs during a cardiac ejection interval and which corresponds to the smallest rate of change of the thoracic impedance; and

    means for computing a cardiac performance parameter value from the ensemble averaged signal samples.

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