Measuring apparatus and a measuring method for the determination of parameters of medical fluids

• US 20030042181A1
• Filed: 08/29/2002
• Published: 03/06/2003
• Est. Priority Date: 09/03/2001
• Status: Active Grant

• Current Assignee: Fresenius Medical Care Deutschland GmbH (Fresenius Medical Care AG)
• Original Assignee: Fresenius Medical Care Deutschland GmbH (Fresenius Medical Care AG)
• Inventors: Metzner, Klaus
• Granted Patent: US 6,821,432 B2
• Time in Patent Office: Days
• US Class Current: 210/85
• CPC Class Codes: A61M 1/3609 Physical characteristics of the blood, e.g. haematocrit, urea
• CPC Class Codes: A61M 1/3622 with a cassette forming partially or totally the blood circuit
• CPC Class Codes: A61M 1/3639 Blood pressure control, pressure transducers specially adapted therefor
• CPC Class Codes: A61M 2205/123 with incorporated reservoirs
• CPC Class Codes: A61M 2205/3368 Temperature
• CPC Class Codes: A61M 2230/207 hematocrit

Abstract

The invention relates to a measuring apparatus for the determination of parameters of medical fluids with a measured region which comprises a measuring chamber device for receiving a disposable cassette with at least one measuring chamber through which the fluid to be measured is guided and at least one measuring element for measuring a measured value whose value depends on the extent of the measuring chamber in a measuring direction and allows the determination of the parameter to be determined, or of a value being in a fixed relationship thereto, with a known extent of the measuring chamber. In accordance with the invention, a distance sensor unit is provided which is arranged relative to the to the measuring chamber such that the measured distance changes relative to the extent of the measuring chamber. The invention furthermore relates to a method for the determination of parameters of medical fluids which can be carried out with the measuring apparatus in accordance with the invention and to a method for the calibration of the measuring apparatus in accordance with the invention.

Claims

1. A measuring apparatus for the determination of parameters of medical fluids with a measured region which comprises the following:

a measuring chamber device for receiving a disposable cassette with at least one measuring chamber through which the fluid to be measured is guided;

at least one measuring element for measuring a measured value whose value depends on the extent of the measuring chamber in a measuring device and allows the determination of the parameter, or of a value being in a fixed relationship thereto, with a known extent of the measuring chamber,

characterised by at least one distance sensor unit (24) which is arranged relative to the to the measuring chamber device such that the measured distance (23) changes relative to the extent (25) of the measuring chamber (15).

2. A measuring apparatus in accordance with claim 1, wherein the at least one distance sensor unit (24) comprises at least two parts (17, 18) which do not contact one another and which are arranged relative to the measuring chamber device such that their relative distance (23) changes with the extent (25) of the measuring chamber (15).

3. A measuring apparatus in accordance with any of claims 1 or 2, wherein the distance sensor unit (24) comprises at least one device (18, 19) for the generation of an electrical and/or magnetic field and at least one sensor (20) for the measurement of the generated magnetic and/or electrical field or its change.

4. A measuring apparatus in accordance with claim 3, wherein the field generation device comprises a device, preferably at least one permanent magnet (18), for the generation of a magnetic field and the field sensor comprises a magneto-resistive sensor (20).

5. A measuring apparatus in accordance with any of claims 1 to 4, wherein the measuring element comprises an ultrasonic transmitter (13) and an ultrasonic receiver (7) which are arranged with respect to a measuring chamber (15) received in the measuring chamber device such that they allow an ultrasonic run time measurement through the measuring chamber.

6. A measuring apparatus in accordance with any of claims 1 to 5, wherein the apparatus is suitable for use in haemo-dialysis and for the determination of parameters of blood.

7. A measuring apparatus in accordance with any of claims 1 to 6, wherein the apparatus is suitable for the determination of the density and/or the concentration and/or the haemocrit value of the medical fluid.

8. A measuring apparatus in accordance with any of claims 1 to 7, wherein the distance sensor unit (24) is arranged laterally offset with respect to a measuring chamber (15) received in the measuring chamber device.

9. A measuring apparatus in accordance with any of claims 1 to 8, characterised by at least two distance sensor units (24) which are arranged offset with respect to one another.

17. A method for the calibration of a measuring apparatus in accordance with any of claims 1 to 9, with which

a) a fluid with a known value of a parameter is sent through the measuring chamber (15), with the measuring apparatus being suitable for its determination;

b) a measured value is determined by the measuring element (7, 13) whose value depends on the extent (2) of the measuring chamber (15) in the measuring direction;

c) the extent (25) of the measuring chamber (15) in the measuring direction is determined from the known parameter and the measured value measured or from a value being in a fixed relationship thereto;

d) a signal of the distance sensor unit (17, 18) is measured;

e) the measured signal is associated with the determined value of the extent (25) of the measuring chamber (15) or with the value being in a fixed relationship thereto;

f) the extent (25) of the measuring chamber (15) is changed; and

g) the steps b) to f) are repeated at least once for the determination of a characteristic curve between the signal of the distance sensor unit (17, 18) and the extent (25) of the measuring chamber (15), or the value being in a fixed relationship thereto.

18. A method for the calibration in accordance with claim 17, with which the parameter is the ultrasound velocity, the measuring elements comprises an ultrasonic transmitter (13) and an ultrasonic receiver (7) and the measured value is the ultrasonic run time.

19. A method for the calibration in accordance with claim 18, in which saline solution is used as the fluid.

10. A method for the determination of parameters of medical fluids, with which

the fluid is led through a measuring chamber;

a measured value is measured whose value depends on the extent of the measuring chamber in a measuring direction and allows the determination of the parameter or of a value being in a fixed relationship thereto with a known extent of the measuring chamber,

characterised in that

with the measurement of the measured value, a value being in a fixed relationship with the extent (25) of the measuring chamber (15) in the measuring direction, or the change in the extent, is additionally determined.

11. A method in accordance with claim 10, wherein the extent (25) is determined with the help of an electrical and/or magnetic field which is generated by a field generation device (18) at the location of a field sensor (20) which are arranged such that their distance (23) is in a fixed relationship with the extent (25).

12. A method in accordance with claim 11, with which a magnetic field is generated by a magnetic field generation device, preferably at least a permanent magnet (18), and its strength and/or direction is measured by a magneto-resistive sensor (20).

13. A method in accordance with claim 10, wherein the change in the extent (25) is determined from the change of an electrical and/or magnetic field which results from the change in a distance (23) between a field generation device (18) and a field sensor (20).

14. A method in accordance With any of claims 10 to 13, with which the measured value comprises the run time of an ultrasonic wave.

15. A method in accordance with any of claims 10 to 14, with which the medical fluid comprises blood and the method is used in haemo-dialysis.

16. A method in accordance with any of claims 10 to 15, with which the parameter to be determined is the density and/or the concentration and/or the haemocrit value.