WO2008076574A2 - Compensation de température pour des électrodes à enzyme - Google Patents

Compensation de température pour des électrodes à enzyme Download PDF

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Publication number
WO2008076574A2
WO2008076574A2 PCT/US2007/084993 US2007084993W WO2008076574A2 WO 2008076574 A2 WO2008076574 A2 WO 2008076574A2 US 2007084993 W US2007084993 W US 2007084993W WO 2008076574 A2 WO2008076574 A2 WO 2008076574A2
Authority
WO
WIPO (PCT)
Prior art keywords
temperature
electrode
sensor
current
catheter
Prior art date
Application number
PCT/US2007/084993
Other languages
English (en)
Other versions
WO2008076574A3 (fr
Inventor
Todd Fjield
Michael J. Higgins
Kenneth Curry
Patrick Carlin
Original Assignee
Edwards Lifesciences Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Edwards Lifesciences Corporation filed Critical Edwards Lifesciences Corporation
Priority to EP07871509A priority Critical patent/EP2088927A2/fr
Priority to CA002667243A priority patent/CA2667243A1/fr
Publication of WO2008076574A2 publication Critical patent/WO2008076574A2/fr
Publication of WO2008076574A3 publication Critical patent/WO2008076574A3/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
    • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
    • C12Q1/001—Enzyme electrodes
    • C12Q1/005—Enzyme electrodes involving specific analytes or enzymes
    • C12Q1/006—Enzyme electrodes involving specific analytes or enzymes for glucose
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/14532—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue for measuring glucose, e.g. by tissue impedance measurement
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1486—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using enzyme electrodes, e.g. with immobilised oxidase
    • A61B5/14865—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using enzyme electrodes, e.g. with immobilised oxidase invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1495—Calibrating or testing of in-vivo probes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2560/00—Constructional details of operational features of apparatus; Accessories for medical measuring apparatus
    • A61B2560/02—Operational features
    • A61B2560/0242—Operational features adapted to measure environmental factors, e.g. temperature, pollution
    • A61B2560/0247—Operational features adapted to measure environmental factors, e.g. temperature, pollution for compensation or correction of the measured physiological value
    • A61B2560/0252—Operational features adapted to measure environmental factors, e.g. temperature, pollution for compensation or correction of the measured physiological value using ambient temperature

Definitions

  • the invention relates generally to enzyme electrodes. More particularly, the invention relates to temperature compensation for enzyme electrodes.
  • glucose monitoring system When diabetics control their blood sugar (glucose), they are more likely to live and stay healthy. They may monitor and test for glucose in the blood using a prior art glucose monitoring system, such as an amperomelric glucose detector.
  • the glucose monitoring system is designed to control amperomctric biosensors in a static and stable environment, such as a medical laboratory.
  • the amperomctric biosensors may be coaled with chemicals, such as glucose oxidase, dehydrogenase or hcxokinase, which combine with glucose in the blood sample. Some sensors measure the amount of current generated by the sensor in the blood sample, while others measure how much light reflects from it. These measurements are further analyzed and quantified by the glucose monitoring system to determine the glucose level in the blood sample.
  • FIG. 10005 The biosensors are calibrated to provide actual measurements at a specific temperature.
  • Figure 1 is a graph illustrating the relationship between the glucose level in the blood sample and the current measured from the biosensors at varying temperatures. The measurements obtained from the biosensors are dependent on the temperature of the surroundings. If the temperature of the surroundings changes, an error occurs in the measurements. An increase in temperature increases the slope of the curve, while a decrease in temperature decreases the slope of the curve. If the slope increases, the computed glucose level is lower than the actual glucose level. In contrast, if the slope decreases the computed glucose level is higher than the actual glucose level. Hence, a change in temperature of the surroundings provides an error in the computed glucose level.
  • Figure 2 is a graph illustrating current change as a function of temperature.
  • Zone A represents clinically accurate measurements.
  • Zone B represents measurements deviating from the reference glucose level by more than 20% but would lead to benign or no treatment.
  • Zone C represents measurements deviating from the reference glucose level by more than 20% and would lead to unnecessary corrective treatment errors.
  • Zone D represents measurements that are potentially dangerous by failing to detect and treat blood glucose levels outside of desired target range.
  • Zone E represents measurements resulting in erroneous treatment. As shown in the Clark Error grid of Figure 3, some of the error measurements were close to the Zone B, thereby deviating from the reference by more than 20%. Hence, when no temperature compensation is employed there are large errors. [0008] There arc many factors that can affect a change in the temperature surrounding the sensor.
  • the temperature of the body may affect the sensor readings.
  • the body temperature may be higher or lower than the temperature at which the sensors were calibrated.
  • the sensors may also be affected by the room temperature prior to insertion in the human body.
  • the infusion of fluid through a lumen in the catheter can have an affect on the sensor's measurements.
  • the fluid may have a different temperature from the human body, and accordingly, would affect the sensor's readings during fluid infusion.
  • the present invention fills this need by providing a temperature compensation method for an enzyme electrode by measuring an operating temperature of the enzyme electrode, measuring the current generated by the enzyme electrode, determining a deviation in temperature between the operating temperature and the reference temperature, determining a glucose concentration corresponding to the measured current at the operating temperature, and compensating the glucose concentration measurement for the deviation in temperature.
  • Figure 1 is a graph illustrating the relationship between the glucose level in the blood sample and the current measured from the biosensors at varying temperatures.
  • Figure 2 is a graph illustrating current change as a function of temperature at several glucose concentrations.
  • Figure 3 is a Clark Error Grid illustrating prior art glucose measurements, without temperature compensation, in relation to true glucose concentration values.
  • Figure 4 illustrates a catheter with a temperature element included for the purpose of temperature compensation.
  • Figure 5 is a cross-sectional view of the catheter of Figure 4 along line 5-5.
  • Figure 6 is a cross-sectional view of the catheter of Figure 4 along line 6-6.
  • Figure 7 is a graph illustrating the change in temperature as a function of time.
  • Figure 8 is a graph illustrating the glucose concentration measurement, with and without temperature compensation, relative to true glucose levels as a function of time, when the sensor is subjected to the temperature variation as shown in Figure 7.
  • Figure 9 is a Clark Error Grid illustrating glucose measurements, with temperature compensation, in relation to true glucose concentration values.
  • Figure 10 is a cross-sectional view of the sensor with a temperature compensation element.
  • a sensor electrode operable in an environment with varying temperature is provided.
  • the sensor provides glucose measurements with acceptable accuracy for clinical setting, specifically to guide therapy.
  • the sensor may be used in an access device, such as a catheter, for both venous and arterial environments.
  • the catheter may be configured to allow for the infusion of fluid.
  • the fluid may infuse into the body at a temperature different from the body temperature.
  • Figure 4 illustrates an example of a catheter 1 1 (e.g., a glucose monitoring catheter).
  • Figure 5 is a cross-sectional view of the catheter 1 1 of Figure 4.
  • Figure 10 is a cross-sectional view of a sensor (e.g., an enzyme electrode or a glucose electrode or sensor) with a temperature sensing device or temperature compensation element 15.
  • the catheter 11 has at least one opening 12 that exposes one or more sensor electrodes 13.
  • underneath the sensor electrodes 13 is a temperature sensing device, such as a thermistor 15, held in place by adhesive or filling material 16, as shown in Figure 6.
  • the catheter 1 1 also has one or more pathways, such as lumens 17, along its length for infusion of fluid in the blood.
  • the flow of fluid in pathways 17 of the catheter 11 can have an affect on the sensor's measurements.
  • the fluid may have a different temperature from the human body, and accordingly, would affect the sensor 13 readings during fluid infusion.
  • the current produced by the sensor electrode 13 for a given analyte concentration is based on a number of factors. For example, it depends on the concentration of enzymes and the diffusion rates through the membrane containing or encapsulating the electrodes, such as a polyurethane, hydro-polymer or gel membrane. The turnover rate of the enzymes and the diffusion rates through the membrane are typically temperature dependent. While the purpose of the sensor electrode 13 is to produce a known magnitude of current for a known concentration of an analyte, a small temperature variation can introduce an error in the measurement. Typically, errors resulting from temperature variation range from 2 to 7 %.
  • One way to mitigate the error introduced by temperature variation is to control the temperature of the sensor 13 and/or solution containing the analyte of interest, such that the temperature remains constant.
  • controlling the temperature of the sensor 13 and/or solution is not feasible. Foi example, body temperature changes or a temperature and/or rate of an infusion fluid would affect the sensor reading. Accordingly, temperature compensation is necessary to obtain accurate measurements.
  • the catheter 1 1 may be an intravascular catheter.
  • the temperature compensation or sensing element 15 may be attached to the sensor 13, located adjacent to the sensor 13, co-located on the same plane or membrane as the sensor 13, integrated into the sensor 13 itself, attached to a device in which the sensor 13 is located, placed in the vicinity of the sensor 13, placed at a location that is representative of the temperature around the sensor 13, or placed in a location that tracks the temperature variation around the sensor 13.
  • the temperature sensing element 15 and/or the sensor 13 may be positioned within the catheter 1 1.
  • the temperature sensing element 15 measures temperature at the sensor 13 to compensate for blood or infusates traveling through the catheter 1 1.
  • the temperature sensing element 15 may be configured or positioned so that it can measure the temperature of the sensor 13 or a change in temperature due to an external condition (e.g., body temperature) or an internal condition (e.g., infusates). The infusate rate may also need to be calculated during the internal condition. In one embodiment, the temperature sensing element 15 directly measure the temperature of the sensor 13 that is in contact with the blood stream.
  • an external condition e.g., body temperature
  • an internal condition e.g., infusates
  • the infusate rate may also need to be calculated during the internal condition.
  • the temperature sensing element 15 directly measure the temperature of the sensor 13 that is in contact with the blood stream.
  • the temperature sensing element 15 may be insulated from the infusion fluid using insulating structures, as disclosed in U.S. Pub. No. 2002/0128568, and Incorporated herein by reference.
  • Various insulating lumens 17 and insulating members may be used to insulate the temperature sensing element 15 from the infusion fluid, which might otherwise degrade the accuracy of the temperature measurement.
  • Temperature compensation may be achieved by using a temperature compensation element that corrects/calibrates for the error in the current measurement due to a temperature change. Under predetermined operating conditions, the effect of temperature on the calibration curve of the temperature compensation element may be an increase in the first order term at higher temperatures and a change in the offset. For electrodes 13 with linear or nearly linear characteristics, the first order term is the slope.
  • the temperature compensation for electrodes 13 with linear or nearly linear characteristics may be expressed in the following form:
  • AT is the change in temperature from the temperature at which the electrode 13 was calibrated
  • T ⁇ mif is the temperature coefficient (change in slope per degree); and slope is the change in analytc concentration divided by the change in current.
  • Equation (1) holds true for glucose electrodes 13 with linear or nearly linear characteristics where there is no infusion of fluid through the catheter over the temperature range in which the correction factor remains linear or nearly linear with temperature.
  • a calibration curve may also be used for a sensor 13 with non-linear characteristics, where fluid is infused into the body through lumen 17 in the catheter 1 1.
  • An "absolute" or “relative” calibration curve may be determined for glucose electrodes 13 with non-linear characteristics.
  • a correction factor or calibration curve is ascertained at specific measured temperatures, whereas for a "relative” calibration curve, a correction factor is determined based on a temperature change from the temperature at which the electrode 13 was calibrated and/or another reference temperature.
  • a temperature compensation method for glucose electrodes with linear or non-linear characteristics the temperature of the area or solution surrounding the sensor 13 or the temperature of a device to which the sensor is attached is measured by the temperature sensing element 15. Based on previous measurements, an individual calibration curve at the measured temperature is predetermined. As the temperature changes, due to an infusion of fluid, for example, various calibration curves may be substituted, such that each calibration curve reflects the current produced as a function of analyte concentration at the measured temperature.
  • the temperature deviation from the temperature at which the electrodes 13 was calibrated is measured by a temperature sensing element 15. Based on this deviation, calibration curves may be substituted, such that each calibration curve reflects the current produced as a function of analyte concentration at the measured temperature deviation.
  • Figure 8 is a graph illustrating the change in glucose concentration over a period of time. As shown in Figure 8, the solid line illustrates the true glucose concentration at a specific time, the dotted line represents the measured glucose concentration without temperature compensation, and the dashed line represents the measured glucose concentration with temperature compensation.
  • the temperature compensation used in Figure 8 was in the form: glucose concentration — slope ⁇ current • e """ '"' (2) whcrc, slope Is the change in glucose concentration divided by the change in current; current is the current generated by the electrode 13;
  • T c oeff is the temperature coefficient of the sensor(s);
  • T Ca i is the temperature at which the electrode 13 was calibrated
  • T is the temperature of the electrode 13 measured by the temperature sensing element 15.
  • the temperature compensation was described in the context of sensor 13.
  • the temperature compensation of the invention may be applied to other enzyme electrodes and/or other biosensors affected by temperature change.
  • one temperature sensing element 15 measures the body temperature (Tl) while the second temperature sensing element measures the temperature (T2) of the infusion fluid.
  • Tl body temperature
  • T2 temperature
  • the temperature results may be calibrated and correlated to obtain an analyte calibiation curve that is compensated by a function of temperature (TI) and temperature (T2).

Abstract

L'invention concerne un procédé de compensation de température pour une électrode à enzyme par mesure d'une température fonctionnelle de l'électrode à enzyme, mesure du courant généré par l'électrode à enzyme, détermination d'un écart de mesure entre le courant généré et un courant de référence à la température fonctionnelle, détermination d'une concentration en enzyme correspondant au courant mesuré et étalonnage de la concentration en enzyme pour compenser l'écart de mesure.
PCT/US2007/084993 2006-11-16 2007-11-16 Compensation de température pour des électrodes à enzyme WO2008076574A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP07871509A EP2088927A2 (fr) 2006-11-16 2007-11-16 Compensation de température pour des électrodes à enzyme
CA002667243A CA2667243A1 (fr) 2006-11-16 2007-11-16 Compensation de temperature pour des electrodes a enzyme

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US85958606P 2006-11-16 2006-11-16
US60/859,586 2006-11-16

Publications (2)

Publication Number Publication Date
WO2008076574A2 true WO2008076574A2 (fr) 2008-06-26
WO2008076574A3 WO2008076574A3 (fr) 2009-02-05

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EP (1) EP2088927A2 (fr)
CN (1) CN101541239A (fr)
CA (1) CA2667243A1 (fr)
WO (1) WO2008076574A2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2450699A4 (fr) * 2009-06-30 2017-05-17 ARKRAY, Inc. Dispositif d'analyse et procédé d'analyse

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI458979B (zh) * 2011-03-18 2014-11-01 Eps Bio Technology Corp 補償環境溫度效應的生化感測器及其方法
EP3510165B1 (fr) * 2016-09-07 2020-12-30 Roche Diabetes Care GmbH Procédés pour tester des capteurs électrochimiques à base d'enzymes

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4431004A (en) * 1981-10-27 1984-02-14 Bessman Samuel P Implantable glucose sensor
US4703756A (en) * 1986-05-06 1987-11-03 The Regents Of The University Of California Complete glucose monitoring system with an implantable, telemetered sensor module
US20050177035A1 (en) * 2003-12-18 2005-08-11 Elliot Botvinick Implantable biosensor and methods of use thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4431004A (en) * 1981-10-27 1984-02-14 Bessman Samuel P Implantable glucose sensor
US4703756A (en) * 1986-05-06 1987-11-03 The Regents Of The University Of California Complete glucose monitoring system with an implantable, telemetered sensor module
US20050177035A1 (en) * 2003-12-18 2005-08-11 Elliot Botvinick Implantable biosensor and methods of use thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2450699A4 (fr) * 2009-06-30 2017-05-17 ARKRAY, Inc. Dispositif d'analyse et procédé d'analyse

Also Published As

Publication number Publication date
CA2667243A1 (fr) 2008-06-26
EP2088927A2 (fr) 2009-08-19
CN101541239A (zh) 2009-09-23
WO2008076574A3 (fr) 2009-02-05

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