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ELECTRICAL COUPLING OF PULSE TRANSIT TIME (PTT) MEASUREMENT SYSTEM TO HEART FOR BLOOD PRESSURE MEASURMENT

  • US 20170340219A1
  • Filed: 08/18/2017
  • Published: 11/30/2017
  • Est. Priority Date: 09/08/2014
  • Status: Active Grant
First Claim
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1. A wrist-worn device for determining a pressure of blood within a cardiovascular system of a user, the cardiovascular system including a heart and the user having a wrist covered by skin, the device comprising:

  • a first pair of electrodes that non-invasively engage the skin over the wrist of the user when the device is worn on the wrist, the first pair of electrodes including a first drive current electrode and a first sense electrode, the first drive current electrode being configured to transfer a drive current between the first drive current electrode and the wrist, the first sense electrode being configured for sensing a first voltage level of the user;

    a second pair of electrodes that are externally located on the wrist-worn device so as to be interfaceable with the user, the second pair of electrodes including a second drive current electrode and a second sense electrode, the second drive current electrode being configured to transfer drive current between the second drive current electrode and the user, the second sense electrode being configured for sensing a second voltage level of the user, wherein the first and second voltage levels are indicative of an impedance of a thorax of the user;

    a photo-plethysmogram (PPG) or a pulse pressure sensor coupled to the wrist-worn device for detecting the arrival of a blood pressure pulse at the user'"'"'s wrist; and

    a controller configured to;

    process a signal indicative of the sensed voltage levels to generate an impedance cardiogram (ICG) for the user;

    process the ICG to detect when blood is ejected from the left ventricle of the user'"'"'s heart;

    process a signal from the PPG or the pulse pressure sensor to detect when a blood pressure pulse corresponding to the ejected blood arrives at the user'"'"'s wrist;

    calculate a pulse transit time (PTT) for the blood pressure pulse from the ejection of the blood from the left ventricle to arrival of the blood pressure pulse at the wrist; and

    generate one or more blood pressure values for the user based on the PTT.

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