Glucose monitoring system

A method of measuring a glucose concentration in the blood of a patient comprising:

• (a) inserting a plurality of glucose sensor assemblies into a vein of a patient, each of said glucose sensors having a reference electrode, a collector electrode and first and second working electrodes;
• (b) applying a voltage to said electrodes so as to cause first and second electrical currents to flow through said first and second working electrodes, respectively, and measuring said first and second electrical currents, the ratio of said second electrical current to said first electrical current providing a measure of oxygen in the patient's blood;
• (c) placing a glucose oxidase enzyme at said first working electrode, said glucose oxidase enzyme reacting with the oxygen and glucose in the blood such that the amount of oxygen measured at said first electrode is inversely proportional to the glucose concentration in the blood;
• (d) determining the glucose concentration in the blood based on said measure of oxygen and calibration constants associated with each of said glucose sensors;
• (e) comparing the glucose concentration measured by each of said plurality of sensors to determine if the respective plurality of glucose concentration measurements are within a prescribed of each other, and if so, combining the plurality of glucose concentration measurements to form a composite glucose measurement, and if not, rejecting the plurality of glucose measurements as being inaccurate;
• (f) storing the composite glucose measurement as a function of time;
• (g) computing a rate-of-change signal for the composite glucose measurement that indicates how said composite glucose measurement has varied over a specified period of time;
• (h) comparing the composite glucose measurement formed most recently and the rate-of-change signal to preprogrammed limits, and generating an alarm signal in the event the preprogrammed limits are exceeded;
• and
• (i) selectively displaying the composite glucose measurement and rate-of-change signal.

A glucose monitoring system comprising:

• a glucose assembly comprising a plurality of glucose sensors, each glucose sensor comprising an enzymatic glucose sensor adapted to be positioned within a blood stream of a person whose blood glucose concentration is to be measured, each glucose sensor of the glucose assembly providing a respective sensor signal that varies as a function of sensed glucose in the blood stream;
• and
• a glucose monitor electrically coupled to the glucose assembly, said glucose monitor comprising
• means for receiving the sensor signal from each glucose sensor,
• means for processing the sensor signal received from each glucose sensor, said means for processing including means for comparing the sensor signals obtained from each of said plurality of sensors and generating a composite sensor signal only if the respective sensor signals are within a first prescribed amount of each other,
• means for storing the composite sensor signal,
• means for monitoring the composite sensor signal over a prescribed period of time and generating a rate of change signal that indicates how rapidly the composite sensor signal is changing,
• means for selectively displaying the composite sensor signal and the rate of change signal,
• first alarm means for determining if the composite sensor 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 verifying that each glucose sensor of the sensor assembly provides an accurate measure of the glucose concentration in the blood stream, and
• control 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.