Glucose monitoring system

  • US 5,497,772 A
  • Filed: 11/19/1993
  • Issued: 03/12/1996
  • Est. Priority Date: 11/19/1993
  • Status: Expired due to Term
First Claim
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1. A glucose monitoring system comprising:

  • an enzymatic glucose sensor adapted to be positioned within a blood stream of a person whose blood glucose concentration is to be measured, said glucose sensor including means for generating a sensor signal that is inversely proportional to the concentration of sensed glucose in the blood stream, said glucose sensor comprising an oxygen detector that detects the amount of oxygen in a region of a prescribed enzyme held within said glucose sensor, and wherein glucose and oxygen in the blood stream react with said prescribed enzyme such that the amount of oxygen is inversely proportional to the glucose concentration, and wherein said oxygen detector comprisesa first working electrode (W1), a collector electrode (C), a reference electrode (R), and a second working electrode (W2), all of said first and second working electrodes, reference electrode and collector electrode being enclosed within a first membrane wherein an ionic solution is maintained, and said first membrane being enclosed within a second membrane,said prescribed enzyme being confined to a window region near said first working electrode,electrical means for causing an electrical current to flow between said collector electrode and said first and second working electrodes, andmeans for measuring how much current flows from said first and second working electrodes when a prescribed trim voltage is maintained across said reference electrode and said first and second working electrodes, the ratio of said currents comprising said sensor signal, which sensor signal provides a measure of oxygen in the blood stream in the vicinity of said glucose sensor; and

    a glucose monitor electrically coupled to the glucose sensor, said monitor comprisingmeans for receiving the sensor signal,means for processing the sensor signal and generating a glucose concentration data signal therefrom,means for storing the glucose concentration data signal,means for monitoring the glucose concentration data signal over a prescribed period of time and generating a rate of change signal that indicates how rapidly the glucose concentration data signal is changing,means for selectively displaying the glucose concentration data signal and the rate of change signal,first alarm means for determining if the glucose concentration data signal exceeds a preset level limit, and if so, generating a first alarm signal,second alarm means for determining if the rate of change signal exceeds a preset trend limit, and if so, generating a second alarm signal,calibration means for periodically calibrating the sensor so that it provides an accurate measure of the glucose concentration in the blood stream, andcontrol means for controlling the monitor so that it performs at least one of a plurality of monitoring functions as selected by a user of said monitor.

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