Method and a device for determining the hydration and/or nutrition status of a patient

• US 7,917,202 B2
• Filed: 06/29/2004
• Issued: 03/29/2011
• Est. Priority Date: 06/29/2004
• Status: Expired due to Fees

• Current Assignee: Fresenius Medical Care Deutschland GmbH (Fresenius Medical Care AG)
• Original Assignee: Fresenius Medical Care Deutschland GmbH (Fresenius Medical Care AG)
• Inventors: Chamney, Paul, Wabel, Peter
• Primary Examiner(s): Hindenburg; Max
• Assistant Examiner(s): EISEMAN, ADAM JARED
• Application Number:
  US11/630,967
• Publication Number:
  US 20080086058A1
• Time in Patent Office: 2,464 Days
• Field of Search: 600/547, 600/506, 600/507, 600/587
• US Class Current: 600/547
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/1073 Measuring volume, e.g. of limbs
• CPC Class Codes: A61B 5/4869 Determining body composition
• CPC Class Codes: A61B 5/4872 Body fat
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

Monitoring the hydration and/or nutrition status of a patient by bioimpedance. A bioimpedance method and device that makes use of a refined model by which the conductivity contributions from intracellular tissues can be taken better into account to enable an improved assessment of the body composition of a patient with increased accuracy. The intracellular volume (ICV) of a patient is determined by determining an intracellular electrical resistance R_mix of the patient and deriving the intracellular volume ICV using R_mix by taking into account that a cell of a kind of tissue contributes differently to the electrical resistance R_mix of the intracellular volume ICV compared with a cell of a second kind of tissue. The application also relates to a device for carrying out the method according to the invention and to a computer program product to be used on such a device.

Claims

1. A method for determining an intracellular volume ICV of a patient having lean tissue compartments and adipose tissue compartments comprising the steps of:

(a) determining an intracellular electrical resistance R_mix of the patient by;

(1) measuring the external cellular electrical resistance R_E of the patient using a first frequency;

(2) measuring the total electrical resistance R of the patient using a second frequency higher than the first frequency; and

(3) deriving the intracellular electrical resistance R_mix from the results in steps (a)(1) and (a)(2);

(b) deriving the intracellular volume ICV of the patent by the iterative steps of;

(1) inputting a typical start value for the intracellular volume as a start value;

(2) deriving a value for a mass M_LT of the lean tissue compartment of the patient;

(3) deriving a value for a mass M_AT of the adipose tissue compartment of the patient;

(4) deriving a value for the mixed resistivity ρ

_mix of the adipose and lean tissue compartments of the patient using reference values for healthy subjects depending on the ratio M_AT/M_LT of the masses M_AT of the adipose tissue compartment and M_LT of the lean tissue compartment;

(5) deriving a new value for the intracellular volume ICV using the value of ρ

_mix derives in step (b)(4) and the value of R_mix from step (a); and

(6) repeating steps (b)(1)-(b)(5) until sufficient convergence is achieved, using the value from step (b)(5) as a new start value for the step of (b)(1);

(c) outputting the intracellular volume ICV of the patient determined in step (b).

2. The method according to claim 1, further comprising the steps of:

(i) determining at least one anthropomorphic measure X of the patient; and

(ii) incorporating the anthropomorphic measure X in steps (b)(1)-(b)(5) of claim 1.

3. The method according to claim 2, wherein the at least anthropomorphic measure X is the height of the patient.

4. The method according to claim 3, further comprising the step of deriving an extracellular water volume of the patient using the determined R_E value.

5. The method according to claim 4, further comprising the step of deriving a mal-hydration water volume of the patient by using the determined extracellular water volume.

6. The method according to claim 4, further comprising the steps of:

(i) determining the total mass of the patient; and

(ii) deriving the malhydration water volume using the extracellular water volume and the total mass of the patient.

7. A device for practicing the method according to claim 1 comprising:

(1) a measurement unit, wherein the measurement unit includes a bioimpedance device for determining an intracellular electrical resistance R_mix of the patient and

(2) an evaluation unit configured to derive the intracellular volume ICV using R_mix by taking into account that a cell of a first kind of tissue contributes differently to the electrical resistance R_mix of the intracellular volume ICV compared with a cell of a second kind of tissue.

8. The device according to claim 7, wherein the evaluation unit is a microprocessor unit comprising a microprocessor program storage unit.

9. The device according to claim 8, wherein the microprocessor program storage unit comprises a program for deriving the intracellular volume ICV using R_mix.

10. The device according to claim 8 wherein the program further controls the measurement unit for determining the resistance R_mix.

11. The device according to claim 7 wherein the device further comprises input means for entering an anthropometric measure X of the patient into the evaluation unit.

12. The device according to claim 7, wherein the measurement unit is further configured to determine an extracellular electrical resistance R_E of the patient and the evaluation unit is further configured to derive the extracellular water volume ECW using R_E.

13. The device according to claim 12, wherein the evaluation unit is further configured to derive a malhydration water volume ECW_EX using the extracellular water volume ECW.

14. The device according to claim 13, wherein the device further comprises input means for entering the total mass M of the patient into the evaluation unit and the evaluation unit is configured to derive the malhydration water volume ECW_EX using M.

15. The device according to claim 7, wherein the evaluation unit is configured to derive the masses M_AT of the first type of tissue and M_LT of the second type of tissue of the patient.

16. The device according to claim 15, wherein the first type of tissue is adipose tissue and the second type of tissue is lean tissue.

17. The device according to claim 16, wherein lean tissue is defined as the tissue of the patient which is not adipose tissue.

18. The device according to claim 7, wherein the device further comprises an output unit linked to the evaluation unit for outputting data derived from the evaluation unit.

19. The device according to claim 18, wherein the output unit displays the data derived from the evaluation unit.

20. A computer program product comprising a storage medium on which a microprocessor program according to claim 9 is stored.