Method and apparatus for estimating the fluid content of a part of the body of a subject

• US 9,955,916 B2
• Filed: 06/04/2013
• Issued: 05/01/2018
• Est. Priority Date: 06/05/2012
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Bonomi, Alberto Giovanni, Caffarel, Jennifer, Cuba Gyllensten, Illapha Gustav Lars, Riistama, Jarno Mikael, Reiter, Harald
• Primary Examiner(s): CERIONI, DANIEL LEE
• Application Number:
  US14/405,802
• Publication Number:
  US 20160029953A1
• Time in Patent Office: 1,792 Days
• Field of Search: 600547
• CPC Class Codes: A61B 2562/0214 Capacitive electrodes
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/4875 Hydration status, fluid retention of the body
• CPC Class Codes: A61B 5/4878 Evaluating oedema
• CPC Class Codes: A61B 5/4881 Determining interstitial fluid distribution or content within body tissue measuring analytes in interstitial fluid in-vivo A61B5/1451
• CPC Class Codes: A61B 5/6823 Trunk, e.g., chest, back, abdomen, hip
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

There is provided a method for estimating the volume of fluid in part of the body of a subject, the method comprising obtaining a measurement of the circumference, c, of the part of the body of the subject; obtaining a measurement of the impedance of the part of the body of the subject using electrodes attached across the part of the body of the subject; and estimating the volume of fluid in the part of the body of the subject from the measurement of impedance and the measurement of the circumference c. An apparatus comprising a control unit configured to perform the method is also provided.

Claims

1. A method performed by a processor for estimating a volume of extra-cellular fluid in a part of a body of a subject, the method comprising:

controlling a set of electrodes to apply a first current of a first frequency to the subject;

measuring a first resistance in response to application of the first current;

controlling the set of electrodes to apply a second current of a second frequency to the subject;

measuring a second resistance in response to application of the second current;

interpolating a third resistance as a third frequency approaches 0 Hz, the third resistance being associated with the third frequency, the interpolating being based on the first resistance and the second resistance;

receiving a measurement of a circumference of the part of the body of the subject;

computing a through-body distance through the body of the subject between a first electrode of the set of electrodes and a second electrode of the set of electrodes based on the circumference; and

estimating the volume of extra-cellular fluid in the part of the body of the subject based on the interpolated third resistance and the computed through-body distance.

2. The method of claim 1, wherein the step of receiving a measurement of the circumference of the body part of the subject comprises:

receiving a measured electrical value from a belt placed around the part of the body of the subject; and

computing the circumference based on the measured electrical value.

3. The method of claim 1, further comprising:

receiving a measurement of an over-body distance over the exterior of the body of the subject between the first electrode the second electrode,

wherein the step of computing the through-body distance comprises computing the length of a chord through the circumference for an arc defined by the over-body distance.

4. The method of claim 1, wherein the third frequency is approximately 0 Hz.

5. The method of claim 1, wherein the step of estimating a volume of fluid comprises evaluating

6. The method of claim 1, further comprising:

determining a gender of the subject;

selecting a first value as a resistivity value when the gender is male; and

selecting a second value as the resistivity value when the gender is female,

wherein the step of estimating a volume is further based on the resistivity value.

7. The method of claim 1, wherein:

the step of controlling a set of electrodes to apply a first current of a first frequency to the subject comprises controlling a first electrode of the set of electrodes to apply the first current, and

the step of controlling the set of electrodes to apply a second current of a second frequency to the subject comprises controlling a second electrode of the set of electrodes to apply the second current.

8. An apparatus for estimating a volume of extra-cellular fluid in a part of a body of a subject, the apparatus comprising:

a set of electrodes for attachment to the part of the body of the subject; and

a processor configured to;

control the set of electrodes to apply a first current of a first frequency to the subject,

measure a first resistance in response to application of the first current,

control the set of electrodes to apply a second current of a second frequency to the subject,

measure a second resistance in response to application of the second current,

interpolate a third resistance as a third frequency approaches 0 Hz, the third resistance being associated with the third frequency based on the first resistance and the second resistance, wherein the third frequency is lower than the first frequency and the second frequency,

receive a measurement of a circumference of the part of the body of the subject,

compute a through-body distance through the body of the subject between a first electrode of the set of electrodes and a second electrode of the set of electrodes based on the circumference, and

estimate the volume of extra-cellular fluid in the part of the body of the subject based on the interpolated third resistance and the computed through-body distance.

9. The apparatus of claim 8, further comprising:

a belt sensor configured to be disposed around the part of the body of the subject,

wherein, in receiving a measurement of the circumference of the body part of the subject, the processor is configured to;

receive a measured electrical value from the belt sensor, and

compute the circumference based on the measured electrical value.

10. The apparatus of claim 8, wherein the processor is further configured to:

receive a measurement of an over-body distance over the exterior of the body of the subject between the first electrode and the second electrode,

wherein in computing the through-body distance the processor is configured to compute the length of a chord through the circumference for an arc defined by the over-body distance.

11. The apparatus of claim 8, wherein the third frequency is approximately 0 Hz.

12. The apparatus of claim 8, wherein in estimating a volume of fluid the processor is configured to evaluate

13. The apparatus of claim 8, wherein the processor is further configured to:

determine a gender of the subject;

select a first value as a resistivity value when the gender is male; and

select a second value as the resistivity value when the gender is female,

wherein, in estimating a volume, the processor is configured to estimate the volume further based on the resistivity value.

14. The apparatus of claim 8, wherein:

the set of electrodes includes a first electrode, a second electrode, a third electrode, and a fourth electrode, wherein

in controlling a set of electrodes to apply a first current of a first frequency to the subject the processor is configured to control the first electrode of the set of electrodes to apply the first current, and

in controlling the set of electrodes to apply a second current of a second frequency to the subject the processor is configured to control the second electrode of the set of electrodes to apply the second current.

15. A non-transitory machine-readable storage medium encoded with instructions for execution by a processor for estimating a volume of extra-cellular fluid in a part of a body of a subject, the non-transitory machine-readable storage medium comprising:

instructions for controlling a set of electrodes to apply a first current of a first frequency to the subject;

instructions for measuring a first resistance in response to application of the first current;

instructions for controlling the set of electrodes to apply a second current of a second frequency to the subject;

instructions for measuring a second resistance in response to application of the second current;

instructions for estimating a third resistance associated with a third frequency based on the first resistance and the second resistance, wherein the third frequency is lower than the first frequency and the second frequency;

instructions for receiving a measurement of a circumference of the part of the body of the subject;

instructions for computing a through-body distance through the body of the subject between a first electrode of the set of electrodes and a second electrode of the set of electrodes based on the circumference; and

instructions for estimating the volume of extra-cellular fluid in the part of the body of the subject based on the interpolated third resistance and the computed through-body distance.

16. The non-transitory machine-readable storage medium of claim 15, wherein the step of receiving a measurement of the circumference of the body part of the subject comprises:

instructions for receiving a measured electrical value from a belt placed around the part of the body of the subject; and

instructions for computing the circumference based on the measured electrical value.

17. The non-transitory machine-readable storage medium of claim 15, further comprising:

instructions for receiving a measurement of an over-body distance over the exterior of the body of the subject between the first electrode and the second electrode,

wherein the instructions for computing the through-body distance comprise instructions for computing the length of a chord through the circumference for an arc defined by the over-body distance.

18. The non-transitory machine-readable storage medium of claim 15, wherein the third frequency is approximately 0 Hz.

19. The non-transitory machine-readable storage medium of claim 15, wherein the instructions for estimating a volume of fluid comprise instructions for evaluating

20. The non-transitory machine-readable storage medium of claim 15, further comprising:

instructions for determining a gender of the subject;

instructions for selecting a first value as a resistivity value when the gender is male; and

instructions for selecting a second value as the resistivity value when the gender is female, wherein the instructions for estimating a volume are further based on the resistivity value.