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Dynamic filter for real-time artifact removal from waveforms

  • US 5,503,160 A
  • Filed: 10/12/1993
  • Issued: 04/02/1996
  • Est. Priority Date: 10/12/1993
  • Status: Expired due to Fees
First Claim
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1. A patient monitor, receiving a cyclical cardiac signal and a composite signal containing cardiac artifacts from a patient, comprising:

  • a sampler, detecting the composite signal at a fixed rate, generating composite samples from the composite signal;

    a cardiac event detector, detecting the cyclical cardiac signal, a marked stable reference point for each cardiac cycle;

    a cardiac interval detector detecting the marked stable reference points and generating a cardiac output signal having a variable cardiac frequency and associated harmonics, wherein the variable cardiac frequency corresponds to a cardiac interval between adjacent marked stable reference points;

    memory, detecting and storing the composite samples, having a newest and an oldest composite sample pointer;

    a first digital filter, connected to the memory, having an adaptive window with two edges defining a length, wherein one edge corresponds to the newest composite sample pointer and the other edge corresponds to the oldest composite sample pointer, for removing events which occur at the variable cardiac frequency and the associated harmonics and producing a filtered composite signal; and

    memory controlling means connected to the memory and detecting the cardiac output signal, for advancing the newest composite sample pointer by one composite sample and gradually adjusting the oldest composite sample pointer such that the length of the adaptive window is equal to the cardiac interval when the newest composite sample pointer is at one of the marked stable reference points;

    wherein the filtered composite signal is produced by removing events which occur at the variable cardiac frequency and the associated harmonics of the cardiac frequency from the composite signal such that the cardiac artifacts are reduced.

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