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Blood pressure monitoring with improved noise rejection

  • US 5,873,836 A
  • Filed: 07/09/1997
  • Issued: 02/23/1999
  • Est. Priority Date: 07/09/1997
  • 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 near the location of the artery and separated a distance from the first 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) multiplying the first and second microphone signals to generate a microphone signal product;

    (e) wave width filtering the microphone signal product to remove therefrom portions of the microphone signal product having a wave width which is less than a selected minimum wave width value to generate a wave width filtered blood pressure sound detection signal;

    (f) comparing the wave width filtered blood pressure sound detection signal to a noise signal threshold level; and

    (g) indicating the detection of a blood pressure sound when the wave width filtered blood pressure sound detection signal exceeds the noise signal threshold level.

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