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Method and apparatus for detecting blood pressure by blood pressure sounds in the presence of significant noise

  • US 5,680,868 A
  • Filed: 06/17/1996
  • Issued: 10/28/1997
  • Est. Priority Date: 06/17/1996
  • Status: Expired due to Fees
First Claim
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1. A method for detecting a blood pressure sound in a patient, comprising the steps of:

  • (a) placing a first microphone on the patient near the location of an artery, the first microphone producing a first microphone signal in response to blood pressure sounds and noise picked up by the first microphone;

    (b) placing a second microphone on the patient having a center separated a distance from a center of the first microphone such that a blood pressure sound picked up by the first microphone will be picked up out of phase by the second microphone, the second microphone producing a second microphone signal in response to blood pressure sounds and noise picked up by the second microphone;

    (c) applying pressure to the artery such that the artery will be forced closed during part of a heart beat cycle and will be forced open during part of the heart beat cycle when the patient'"'"'s blood pressure exceeds the pressure applied to the artery, the opening of the artery causing a blood pressure sound to be produced;

    (d) selecting portions of the first and second microphone signals having characteristics corresponding to blood pressure sounds;

    (e) multiplying the selected portions of the first and second microphone signals at selected points in time to generate a microphone signal product; and

    (f) indicating the detection of a blood pressure sound when the microphone signal product is negative for multiple consecutive selected points in time corresponding to a selected time period.

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