Apparatus for measurement and control of the content of glucose, lactate or other metabolites in biological fluids

• US 6,618,603 B2
• Filed: 05/07/2001
• Issued: 09/09/2003
• Est. Priority Date: 05/08/2000
• Status: Expired due to Term

• Current Assignee: A Menarini Industrie Farmaceutiche Riunite SRL
• Original Assignee: A Menarini Industrie Farmaceutiche Riunite SRL
• Inventors: Poscia, Alessandro, Varalli, Maurizio Claudio
• Primary Examiner(s): Jeffery, John A.
• Application Number:
  US09/851,447
• Publication Number:
  US 20010041830A1
• Time in Patent Office: 855 Days
• Field of Search: 600/345, 600/347, 600/365, 600/372, 128/920, 128/903-904, 204/403.01, 435/14, 422/82.03
• US Class Current: 600/345
• CPC Class Codes: A61B 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors

Abstract

An apparatus for the continuous measurement of glucose and lactate in interstitial fluids including a glucose measurement cell, an A/D conversion block, a memory block and a bi-directional communication between the interface block and an external calculation unit.

Claims

1. An apparatus for the near-continual measurement of the quantity of analytes found in an interstitial biological fluid, comprising a hydraulic circulation system (1) capable of taking a solution from a tank (2) and sending the solution through a capillary tube (14) into a subcutaneous area of a patient, from where an appropriately filtered sample of interstitial fluid is taken through a capillary tube (15) and sent to a block (4) provided with a measurement cell for measuring the glucose level and, after measurement, the sample is sent to a discharge (3);

in which an analog voltage signal corresponding to the measurement performed is sent from the block (4) to an analog-digital conversion block (5) from where the signal is again sent in digital for to a data memory (12) of a microprocessor control unit provided with an alarm management system (6) and an output interface block (13), which includes a block (17) for bidirectional transmission between the interface block (13) and an external calculation unit of the digital signal, such that there is not electrical contact between the interface block (13) and the external calculation unit.

2. The apparatus according to claim 1, wherein the bidirectional transmission block (17) transmits the digital signal to the external calculation unit by means of a beam of light.

3. The apparatus according to claim 2, wherein the transmission block (17) is equipped with transceiver optical circuits.

4. The apparatus according to claim 3, wherein the transceiver optical circuits are optical transceivers formed of an integrated circuit in which information to be transmitted is received by and sent from the microprocessor as digital electrical signals by means of a serial connection.

5. The apparatus according to claim 3, wherein the transmission block (17) is equipped with appropriate modulation circuits of the transceiver optical circuits so that luminous signals transmitted and received comply with at least one infrared optical communication protocol.

6. The apparatus according to claim 1, in which the bi-directional transmission block (17) transmits the digital signal to the external calculation unit by means of radio frequencies according to CCITT rec. X 25 protocol.

7. The apparatus according to claim 1, further comprising a system (18) for continuous measurement of the pressure in the hydraulic circulation system (1) for the transfer fluid of the sample to be measured.

8. The apparatus according to claim 1, wherein the alarm management system is equipped with a vibrational alarm device (19).

9. The apparatus according to claim 1, wherein the hydraulic system (1) includes a driving pump selected from the group consisting of:

a mechanical pump;

a syringe;

a peristaltic pump;

a membrane pump;

and a piezoelectric pump.

10. The apparatus according to claim 1, wherein after the solution is sent to a subcutaneous area of the patient through a capillary tube (14) said sample of interstitial fluid is taken by diffusion through a filter membrane.

11. The apparatus according to claim 1, wherein the sample is sent to the discharge tank (3) at a flow rate ranging from 5 to 200 μ

L per minute.

12. The apparatus according to claim 1, wherein the tank (2) and the discharge (3) are formed of two compartments of a single tank, which is divided in two by an impermeable and deformable dividing wall, such that the compartments perform the functions of the tank (2) and of the discharge (3).

13. The apparatus according to claim 12, wherein a volume of the compartment of the single tank performing the function of the discharge (3) is greater than the volume of the compartment of the single tank performing the function of the tank (2).

14. The apparatus according to claim 1, wherein the analyte is selected from the group consisting of glucose and lactate.

15. The apparatus according to claim 14, wherein measurement of the level of analyte in the sample is taken by means of an immobilized enzyme which releases a quantity of oxygen proportional to the quantity of analyte in the solution.

16. The apparatus according to claim 15, wherein the enzyme is selected from the group consisting of:

glucose oxidase (GOD), produced from microorganisms or recombinant DNA;

and lactate oxidase (LOD), produced from microorganisms or recombinant DNA;

and further wherein the enzyme is immobilized with simple covalent bonds.

17. The apparatus according to claim 16, wherein the analyte is glucose and the enzyme is GOD, produced from the microorganism Aspergillus Niger.

18. The apparatus according to claim 1, wherein the measurement cell of block (4) is a cell for performing potentiometric measurements, utilizing platinum and silver electrodes, which generate a current of an intensity proportional to the quantity of oxygen present;

and further wherein the electronic circuit for amplification and current—

voltage conversion has an output voltage signal with an amplitude of from 0 to 3 V, with the amplitude of the output voltage signal being proportional to the level of analyte in the sample being analysed.

19. The apparatus according to claim 1, wherein the measurement cell of block (4) includes a coupling system with pressure contacts against which the measurement cell is blocked elastically, so that a value of an isolation resistance of the measurement circuit is at least twice as great as a value of an internal resistance of the cell.

20. The apparatus according to claim 1, wherein the measurement block (4) includes a transconductance electronic amplifier, having interchangeable transducers and a calibration circuit.

21. The apparatus according to claim 1, wherein block (5) has a resolution of at least 8 bits.

22. The apparatus according to claim 1, wherein interface block (13) is provided with a patient-protective electrical feature to prevent electrical shock or injury to the patient, the feature being selected from the group consisting of:

use of a serial output together with appropriate circuits with single opto-isolators; and

use of isolating integrated circuits.

23. The apparatus according to claim 22, wherein the patient-protective electrical feature is a serial output with appropriate circuits with single opto-isolators.

24. The apparatus according to claim 22, wherein the patient-protective electrical feature employs solating integrated circuits.

25. The apparatus according to claim 1, wherein interface block (13) is provided with a single interface circuit.

26. The apparatus according to claim 1, wherein interface block (13) is provided with a plurality of interface modules.

27. The apparatus according to claim 1, wherein capillary tube (15) is equipped with a three-way cock with an open position and a closed position, which when in the closed position permits transit of the flow of discharge fluid from the measurement cell to the discharge tank (3), and when in the open position permits the flow to be externally diverted.