ESTIMATION OF PROPENSITY TO SYMPTOMATIC HYPOTENSION

• US 20100094158A1
• Filed: 09/06/2007
• Published: 04/15/2010
• Est. Priority Date: 09/19/2006
• Status: Active Grant

• Current Assignee: Gambro Lundia AB (Baxter International Inc.)
• Original Assignee: Gambro Lundia AB (Baxter International Inc.)
• Inventors: Solem, Kristian, Olde, Bo
• Granted Patent: US 8,831,717 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61M 1/14 Dialysis systems; Artificial kidneys; Blood oxygenators semi-permeable membranes characterised by the material, manufacturing processes therefor B01D71/00 ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis
• CPC Class Codes: A61M 1/16 with membranes
• CPC Class Codes: A61M 1/34 Filtering material out of the blood by passing it through a membrane, i.e. hemofiltration or diafiltration
• CPC Class Codes: A61M 1/341 by measuring the filtrate rate or volume
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: A61M 2230/65 Impedance, e.g. conductivity, capacity

Abstract

The invention relates to estimation of a patient'"'"'s propensity to suffer from symptomatic hypotension during extracorporeal blood treatment. An electromagnetic test signal, which is applied over a thoracic region of the patient via at least one transmitter electrode. A result signal produced in response to the test signal is received via at least one receiver electrode on the patient. A test parameter is derived based on the result signal. The test parameter expresses a fluid status of the thoracic region of the patient, and it is determined whether the test parameter fulfills an alarm criterion. If the test parameter fulfills an alarm criteria, an alarm signal is generated. This signal indicates that the patient is hypotension prone, and that appropriate measures should be taken.

Claims

1. An alarm apparatus for estimating a patient'"'"'s propensity to suffer from symptomatic hypotension during extracorporeal blood treatment, the apparatus comprising:

an output interface configured to generate an electromagnetic test signal, said electromagnetic test signal being configured to be fed to at least one transmitter electrode, said at least one transmitter electrode being configured to apply the test signal over a thoracic region of the patient;

an input interface configured to receive a result signal via at least one receiver electrode on the patient'"'"'s body, the result signal being produced in response to the electromagnetic test signal; and

an analysis unit configured to determine a bio-impedance parameter based on the result signal, wherein the analysis unit comprises;

a processing module configured to derive a test parameter based on the result signal, the test parameter expressing a fluid status of the thoracic region of the patient,

a comparison module configured to test whether the test parameter fulfills an alarm criterion, and

an alarm triggering module configured to cause an alarm signal to be generated if the alarm criterion is fulfilled.

2. The alarm apparatus according to claim 1, wherein the electromagnetic test signal comprises at least first and second signal components having mutually different spectral properties, the input interface being configured to receive a set of result signal components via the at least one receiver electrode, the set of result signal components being produced in response to the electromagnetic test signal, and the processing module being configured to derive the test parameter based on the set of result signal components.

3. The alarm apparatus according to claim 1, wherein the test parameter describes bio-impedance properties of the patient'"'"'s thoracic region.

4. The alarm apparatus according to claim 1, wherein the test parameter expresses an extracellular-to-intracellular fluid ratio in the thoracic region of the patient.

5. The alarm apparatus according to claim 3, wherein the test parameter reflects an admittance ratio calculated as a first admittance value divided by a second admittance value, the first admittance value expressing an estimate of a low-frequency response to a first signal component in the electromagnetic test signal, and the second admittance value representing a difference between a high-frequency response to a second signal component in the electromagnetic test signal and the low-frequency response.

6. The alarm apparatus according to claim 4, wherein the comparison module is configured to deem the alarm criterion as fulfilled if the test parameter exceeds a first threshold value (Y_t).

7. The alarm apparatus according to claim 3, wherein the test parameter expresses an extracellular fluid volume, and the comparison module configured to deem the alarm criterion as fulfilled if the test parameter exceeds a second threshold value.

8. The alarm apparatus according to claim 3, wherein the test parameter expresses an intracellular fluid volume, and the comparison module is configured to deem the alarm criterion as fulfilled if the test parameter is below a third threshold value.

9. The alarm apparatus according to claim 5, wherein the first signal component has spectral properties, including that its the electromagnetic energy of the first signal component is distributed in a first frequency band extending from a lower first frequency limit to an upper first frequency limit.

the second signal component has spectral properties, including that its the electromagnetic energy of the second signal component is distributed in a second frequency band extending from a lower second frequency limit to an upper second frequency limit, and

the lower second frequency limit represents a higher frequency than the upper first frequency limit.

10. The alarm apparatus according to claim 9, wherein the lower first frequency limit is approximately 1 kHz, the upper first frequency limit is approximately 10 kHz, the lower second frequency limit is approximately 10 kHz, and the upper second frequency limit is approximately 100 MHz.

11. The alarm apparatus according to claim 1, wherein the electromagnetic test signal comprises a source signal component of a well-defined frequency, and the processing module is adapted configured to derive the test parameter based on a phase shift of the result signal relative to the source signal component and an attenuation of the result signal relative to the source signal component.

12. The alarm apparatus according to claim 1, wherein the processing module is configured to:

receive at least one physiology parameter expressing body specific features of the patient, and

derive the test parameter on the further basis of the at least one physiology parameter.

13. The alarm apparatus according to claim 12, wherein the at least one physiology parameter comprises at least one of body weight data, height data, or data specifying a body fat content.

14. The alarm apparatus according to claim 1, wherein the processing module is configured to:

receive at least one of a treatment specific parameter specifying at least one characteristics of the extracorporeal blood treatment, and a patient specific parameter specifying at least one vital sign of the patient; and

derive the test parameter on the further basis of said at least one received parameter.

15. (canceled)

16. A method for estimating a patient'"'"'s propensity to suffer from symptomatic hypotension during extracorporeal blood treatment, the method comprising:

generating an electromagnetic test signal;

applying the electromagnetic test signal over a thoracic region of the patient via at least one transmitter electrode;

receiving a result signal via at least one receiver electrode on the patient'"'"'s body; and

determining a bio-impedance parameter based on the result signal, wherein said determining a bio-impedance parameter further comprises;

deriving a test parameter based on the result signal, the test parameter expressing a fluid status of the thoracic region of the patient

testing whether or not the test parameter fulfills an alarm criterion, and if the alarm criterion is fulfilled,

causing an alarm signal to be generated.

17. The method according to claim 16, wherein the electromagnetic test signal comprises at least first and second signal components having mutually different spectral properties, the method further comprising:

receiving a set of result signal components via the at least one receiver electrode, the set of result signal components being produced in response to the electromagnetic test signal, and

deriving the test parameter based on the set of result signal components.

18. The method according to claim 16, wherein the test parameter describes bio-impedance properties of the patient'"'"'s thoracic region.

19. The method according to claim 16, wherein the test parameter expresses an extracellular-to-intracellular fluid ratio in the thoracic region of the patient.

20. The method according to claim 17, wherein the test parameter reflects an admittance ratio calculated as a first admittance value divided by a second admittance value, the first admittance value expressing an estimate of a low-frequency response to the first signal component in the electromagnetic test signal, and the second admittance value representing a difference between a high-frequency response to the second signal component in the electromagnetic test signal and the low-frequency response.

21. The method according to claim 19, wherein the alarm criterion is regarded as fulfilled if the test parameter exceeds a first threshold value.

22. The method according to claim 18, wherein the test parameter expresses an extracellular fluid volume, and the alarm criterion being is regarded as fulfilled if the test parameter exceeds a second threshold value.

23. The method according to claim 18, wherein the test parameter expresses an intracellular fluid volume, and the alarm criterion is regarded as fulfilled if the test parameter is below a third threshold value.

24. The method according to claims 20, wherein

the first signal component has spectral properties, including that the electromagnetic energy of the first signal component is distributed in a first frequency band extending from a lower first frequency limit to an upper first frequency limit,

the second signal component has spectral properties, including that the electromagnetic energy of the second signal component is distributed in a second frequency band extending from a lower second frequency limit to an upper second frequency limit, and

the lower second frequency limit represents a higher frequency than the upper first frequency limit.

25. The method according to claim 24, wherein the lower first frequency limit is approximately 1 kHz, the upper first frequency limit is approximately 10 kHz, the lower second frequency limit is approximately 10 kHz and the upper second frequency limit is approximately 100 MHz.

26. The method according to claim 16, wherein the test signal comprises a source signal component of a well-defined frequency, and the method further comprises deriving the test parameter based on a phase shift of the result signal relative to the source signal component and an attenuation of the result signal relative to the source signal component.

27. The method according to claim 16, further comprising:

receiving at least one physiology parameter expressing body specific features of the patient, and

deriving the test parameter on the further basis of the at least one physiology parameter.

28. The method according to claim 27, wherein the at least one physiology parameter comprises at least one of body weight data, height data and or data specifying a body fat content.

29. The method according to claim 16, further comprising:

receiving at least one of a treatment specific parameter specifying at least one characteristics of the extracorporeal blood treatment, and a patient specific parameter specifying at least one vital sign of the patient; and

deriving the test parameter on the further basis of said at least one received parameter.

30. A computer program directly loadable into the internal memory of a computer, said computer program comprising software for controlling the steps of claim 16 when said program is run on the computer.

31. A computer readable medium, having a program recorded thereon, where the program is configured to make a computer control the steps of any of claim 16.