Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/14—Devices for taking samples of blood ; Measuring characteristics of blood in vivo, e.g. gas concentration within the blood, pH-value of blood
• • 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
  • A61B5/14532—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
  • 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
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
  • A61B5/053—Measuring electrical impedance or conductance of a portion of the body
  • A61B5/0531—Measuring skin impedance

Definitions

• the present invention relates to an apparatus for measuring blood-glucose, and more particularly, to an apparatus and method for measuring blood-glucose using an electrophoresis phenomenon.
• blood-glucose measuring apparatuses take blood from a human body directly by using lancets, and then measure concentration of glucose contained in the blood.
• blood-glucose measuring apparatuses always take blood in order to measure blood-glucose, thereby making patients experience some amount of pain and fear.
• blood-gathering process may be more stressful to diabetic patients who periodically need to measure their blood-glucose.
• a non-invasive blood-glucose measuring apparatus using an electrophoresis phenomenon has been developed.
• the noninvasive blood-glucose measuring apparatus uses movement of ions contained in body fluids, and in particular, uses a phenomenon that glucose existing in body fluids can be extracted when current flowing in a predetermined direction is applied to the skin. Accordingly, the non-invasive blood-glucose measuring apparatus using the electrophoresis phenomenon does not need to physically extract blood, thereby providing a more user-friendly method.
• An operational principal of the non-invasive blood-glucose measuring apparatus is as follows. Two extraction electrodes are contacted with the skin, and constant current is applied to each extraction electrode. Glucose induced around the electrode to which (-) voltage is connected is extracted, and the extracted glucose reacts with oxidase to generate hydrogen peroxide. The generated hydrogen peroxide is oxidized on a surface of a working electrode to generate current, and then a blood-glucose value is calculated on the basis of the generated current. Disclosure of Invention Technical Problem
• the conventional blood-glucose measuring apparatus always applies voltage having the same polarity to the same extraction electrode, thereby shortening the lifespan of the electrode. That is, when (+) voltage is applied to a first extraction electrode and (-) voltage is applied to a second extraction electrode, current always flows only from the first extraction electrode to the second extraction electrode. Therefore, after a predetermined period of time has elapsed, the life span of the electrode is shortened due to the repetitive oxidizing or reducing reaction taking place thereon.
• the conventional blood-glucose measuring apparatus does not consider that the amount of glucose extracted depends on the skin resistance, thereby making the measurement result inaccurate. That is, the skin resistance formed between different ion conductive mediums varies from several tens of k ⁇ to several hundreds of M ⁇ according to the circumstance. Thus, if the skin resistance is different, even if the same voltage is applied to the same person, the amount of glucose extracted varies, thereby making the measurement result inaccurate.
• the conventional blood-glucose measuring apparatus does not consider the fact that reactivity of oxidase depends on the skin temperature, thereby making the measurement result inaccurate. That is, when the skin temperature varies, activity of glucose oxidase contained in an ion conductive medium varies. Thus, even if the same amount of oxidase reacts with the same amount of glucose, the amount of generated hydrogen peroxide varies, thereby making the measurement result inaccurate.
• the present invention provides an apparatus and method for noninvasively measuring blood-glucose using an electrophoresis phenomenon that can lengthen the life span of an electrode by varying a direction of current which is applied between two extraction electrodes.
• the present invention also provides an apparatus and method for noninvasively measuring blood-glucose using an electrophoresis phenomenon that can calculate an accurate blood-glucose level by compensating a measurement based on a skin resistance.
• the present invention also provides an apparatus and method for noninvasively measuring blood-glucose using an electrophoresis phenomenon that can calculate an accurate blood-glucose level by compensating a measurement based on a skin tern- perature.
• a current flow direction is changed periodically.
• the life span of the extraction electrode can be prevented from being shortened over an oxidizing or reducing reaction.
• blood-glucose data is calculated in consideration of differences of extracted amount and reactivity according to skin resistance and skin temperature, more accurate blood-glucose data can be obtained as compared to a conventional blood-glucose measuring apparatus.
• FIG. 1 is a block diagram illustrating a non-invasive blood-glucose measuring apparatus according to an embodiment of the present invention
• FIG. 2 is a circuit diagram illustrating a constant current generating unit and an extraction electrode alternating unit according to an embodiment of the present invention
• FIG. 3 A is a circuit diagram illustrating an example of an extraction electrode alternating unit according to an embodiment of the present invention.
• FIG. 3B is a circuit diagram illustrating an example of an extraction electrode alternating unit according to another embodiment of the present invention.
• FIG. 4 is a flowchart of a non-invasive blood-glucose measuring method according to an embodiment of the present invention. Best Mode
• a blood-glucose measuring apparatus using an electrophoresis phenomenon including: two different extraction electrodes; an extraction electrode alternating unit applying a constant current to one of the two extraction electrodes; and a microprocessor generating a control signal for selecting one of extraction electrodes.
• the extraction electrode alternating unit may alternately apply the constant current to the selected extraction electrode in response to the control signal.
• the extraction electrode alternating unit may include at least one switch which is opened or closed in response to the control signal.
• the blood-glucose measuring apparatus may include a resistance measuring apparatus to measure skin resistance.
• the blood-glucose measuring apparatus may include a temperature measuring apparatus to measure skin temperature.
• the method may further include measuring a skin resistance of the target patient; and compensating the blood-glucose data according to the measured skin resistance.
• the method may further include measuring a skin temperature of the target patient; and compensating the blood-glucose data according to the measured skin temperature.
• FIG. 1 is a block diagram illustrating a non-invasive blood-glucose measuring apparatus 100 according to an embodiment of the present invention
• the non-invasive blood-glucose measuring apparatus 100 includes a power source converter 105, a constant current generating unit 110, an extraction electrode alternating unit 115, a first extraction electrode 120, a second extraction electrode 125, an ion transmitter 130, a working electrode 135, a microprocessor 140, a key input unit 145, a display unit 150, a communication unit 155, an alarm generating unit 160, a data storage unit 165, a skin resistance measuring unit 170, and a skin temperature measuring unit 175, and these elements will now be described in detail.
• the power source converter 105 receives a reference power source from a power source supplying unit (not shown) to generate a positive power source of +18V and a negative power source of -18V.
• the power source supplying unit may be a re- chargable lithium ion battery of 3.7V and may include a power source charging unit.
• the power source converter 105 may be a DC-DC converter which converts the reference power source in a step-up method.
• the power source converter 105 may be controlled by the microprocessor 140 to change the level of the positive/negative power source.
• the constant current generating unit 110 receives a positive power source from the voltage converter 105 and generates current which is not related to a load resistance. Constant current is applied to the first extraction electrode 120 or the second extraction electrode 125. Constant current may be in the range of 0.25 to 0.5 mA .
• the constant current generating unit 110 may be a voltage division circuit comprised of a resistance and a transistor, and the transistor may be an N- type or P-type bipolar junction transistor.
• the extraction electrode alternating unit 115 provides constant current to the first extraction electrode 120 or the second extraction electrode 125 under the control of the microprocessor 140 and reverses the direction in which the current is applied after a predetermined time has elapsed.
• the period for alternating the first extraction electrode 120 and the second extraction electrode 125 may be 10 minutes, respectively.
• the extraction electrode alternating unit 115 may include a plurality of non-contacting switches controlled by the microprocessor 140.
• the first extraction electrode 120 or the second extraction electrode 125 outputs constant current provided from the extraction electrode alternating unit 115 and thereby sets up a current path beneath a skin of a patient.
• the first extraction electrode 120 or/and the second extraction electrode 125 may be formed of platinum, platinum/ ca ⁇ on, or silver/silver chloride.
• the working electrode 135, and a counter electrode and a reference electrode which are not shown in the drawings may be located around the first extraction electrode 120 or/and the second extraction electrode 125.
• the ion transmitter 130 accommodates glucose introduced/extracted from blood fluids and may be formed of a water-soluble hydrogel.
• the ion transmitter 130 may include glucose oxidase generating hydrogen peroxide when the ion transmitter 130 reacts with glucose extracted from the skin of a patient.
• the ion transmitter 130 directly contacting with the skin transmits the hydrogen peroxide generated from the glucose to the working electrode 135 by using a diffusion method.
• the working electrode 135 is located in a surface of the first extraction electrode 120 or/and the second extraction electrode 125, and is a place where the hydrogen peroxide transmitted from the ion transmitter 130 is oxidized to generate current.
• a counter voltage having a predetermined size is applied to the counter voltage, which may be less than 0.4 V in order to ensure accuracy of analysis.
• the working electrode 135 may be formed of platinum, or platinum/caibon.
• the microprocessor 140 generally controls all modules of the apparatus and calculates a blood-glucose of patient on the basis of generated current which is input via the working electrode 135.
• the microprocessor 140 may display/ store/analyze/transmit the calculated blood-glucose data or display data inputted by a user.
• the microprocessor 140 may compare the calculated blood-glucose data with a threshold value and generate an alert according to the compared result.
• the microprocessor 140 may calculate an initial blood-glucose by changing the generated current according to a predetermined table.
• the microprocessor 140 may compensate the initial blood-glucose calculated according to a skin resistance or/and a skin temperature input from the skin resistance measuring unit 170 or/and the skin temperature measuring unit 175.
• the microprocessor 140 may calculate a final blood- glucose by substituting a generated current, a skin resistance, and a skin temperature into a predetermined algorithm.
• the key input unit 145 which can input commands by hospital staff or a patient, may be a touch-screen type interface.
• the display unit 150 which is a module displaying blood-glucose data or analysis data, may be a liquid crystal display (LCD) or a light- emitting diode (LED).
• the communication unit 155 which is a module transmitting/ receiving data to/from a host computer (for example, a personal computer (PC) or a personal digital assistant (PDA)), may include an RS-232 serial communication port and a communication port for ZigBee communication or BlueTooth communication.
• the alarm generating unit 160 which is a module generating alarm when the calculated blood-glucose is out of a set threshold value, may generate an alert signal such as an alarm sound or a flashing light.
• the threshold value may be a first threshold value (50 mg /dL) which is a reference value of low blood-glucose and a second threshold value (350 mg /dL) which is a reference value of high blood-glucose.
• the data storage unit 165 which is a module storing the calculated blood-glucose data together with a measurement time, may be a nonvolatile memory.
• the skin resistance measuring unit 170 measures a skin resistance and outputs the measured skin resistance to the microprocessor 140.
• the skin resistance measuring unit 170 may be in contact with the first extraction electrode 170 and the second extraction electrode 175.
• the microprocessor 140 calculates a new blood-glucose value by compensating the previous blood-glucose. In particular, the relationship between the skin resistance and the amount of glucose extracted is considered.
• the skin temperature measuring unit 175 measures a skin temperature and outputs the measured skin temperature to the microprocessor 140.
• the skin temperature measuring unit 175 may be in contact with skin for accurately measuring the skin temperature.
• the microprocessor 140 calculates a new blood-glucose value by compensating for the previous blood-glucose. In particular, the relationship between the skin temperature and reactivity of oxidase is considered.
• FIG. 2 is a diagram illustrating a constant current generating unit 210 and an ex- traction electrode alternating unit 220 according to an embodiment of the present invention.
• the constant current generating unit 210 includes four resistances Rl through R4 and a transistor Tr, and the extraction electrode alternating unit 220 according to the present invention includes four switches SWl through SW4, and these elements will now be described in detail.
• the constant current generating unit 210 may be comprised of a voltage division circuit using a resistor and may use N-BJT or P-BJT as an active element for generating constant current.
• the constant current generating unit 210 generates current having a uniform size regardless of the size of a skin resistance.
• the constant current may be 0.25 mA .
• Current flowing through a collector terminal C is the same as current flowing through an emitter terminal E.
• the extraction electrode alternating unit 220 is comprised of switches which is operated according to a corresponding control signal, and outputs constant current to a first extraction electrode or a second extraction electrode.
• Each switch may be a non- contacting switch comprised of an active element such as a transistor.
• First and third control signals and second and fourth control signals may have the same logic level in order to prevent a short circuit.
• FIG. 3A is a diagram illustrating an example of an extraction electrode alternating unit according to an embodiment of the present invention.
• FIG. 3B is a diagram illustrating an example of an extraction electrode alternating unit according to another embodiment of the present invention.
• second and fourth switches SW2 and SW4 close, and thus an extraction current Ic is transmitted from a first extraction electrode to a second extraction electrode through a current path in a subcutaneous tissue. Accordingly, a neutral glucose molecule is accumulated together with positive ions in the second extraction electrode to which (-) voltage is applied. Therefore, a reducing reaction occurs in the second extraction electrode (for example, AgCl ⁇ Ag)
• first and third switches SWl and SW3 close, and thus the extraction current Ic is transmitted from the second extraction electrode to the first extraction electrode through a current path in a subcutaneous tissue. Accordingly, a neutral glucose molecule is accumulated together with positive ions in the first extraction electrode to which (-) voltage is applied. Therefore, an oxidizing reaction occurs in the second extraction electrode (for example, Ag ⁇ AgCl)
• the extraction current Ic may flow from the first extraction electrode to the second extraction electrode or from the second extraction electrode to the first extraction electrode. Accordingly, an oxidizing reaction occurs at one extraction electrode and a reducing reaction occurs at the other extraction electrode for a predetermined period of time, and thereafter the flow of current is switched so that the oxidizing reaction and the reducing reaction occur at opposite electrodes to previous. This alternation of extraction electrodes repeatedly occurs in light of the predetermined period, thereby preventing the life span of the extraction electrode from being shortened.
• FIG. 4 is a flowchart of a non-invasive blood-glucose measuring method according to an embodiment of the present invention.
• Extraction current for extracting glucose is applied to a first extraction electrode or a negative power source (Operation 410).
• the extraction current is a constant current having a uniform size regardless of the size of a skin resistance existing in a current path.
• a working electrode may be formed in an inner surface of the first extraction electrode or the second extraction electrode, and a counter electrode and a reference electrode may be formed in an outer surface of the first extraction electrode or/and the second extraction electrode.
• Glucose accumulated in an ion transmitter is extracted (Operation 420).
• the extracted glucose reacts with glucose oxidase existing in the ion transmitter and generates hydrogen peroxide of an amount corresponding to the amount of extracted glucose.
• the generated hydrogen peroxide reacts with voltage applied between the working electrode and the reference electrode, and generates current having a size corresponding to the amount of generated hydrogen peroxide.
• An initial blood-glucose value of a patient is calculated on the basis of the size of the generated current (Operation 430).
• a skin resistance existing in a current path s measured (Operation 440).
• the skin resistance may be in the range of several tens of k ⁇ to several hundreds of M ⁇ .
• the current skin temperature is measured (Operation 450).
• a final blood-glucose value is calculated by reflecting variation according to the skin resistance or/and the skin temperature on the calculated initial blood-glucose (Operation 460).
• the calculated final blood-glucose is displayed through a display unit (Operation
• a current flow direction is changed periodically.
• the life span of the extraction electrode can be prevented from being shortened over an oxidizing or reducing reaction.
• blood-glucose data is calculated in consideration of differences of extracted amount and reactivity according to skin resistance and skin temperature, more accurate blood-glucose data can be obtained as compared to a conventional blood-glucose measuring apparatus.
• the present invention can also be embodied as computer readable code on a computer readable recording medium.
• the computer readable recording medium is any data storage device that can store data which can be thereafter read by a computer system. Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and flash memory.
• ROM read-only memory
• RAM random-access memory
• CD-ROMs compact discs
• magnetic tapes magnetic tapes
• floppy disks magnetic tapes
• optical data storage devices and flash memory.
• flash memory optical data storage devices

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Citations (2)

• 2008
  • 2008-05-13 KR KR1020080044027A patent/KR20090118314A/ko active IP Right Grant
  • 2008-08-22 WO PCT/KR2008/004920 patent/WO2009139522A1/en active Application Filing

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