Bioimpedance circumference measurement

• US 10,362,968 B2
• Filed: 04/17/2013
• Issued: 07/30/2019
• Est. Priority Date: 10/15/2010
• Status: Active Grant

• Current Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius SE & Co. KGaA)
• Original Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius SE & Co. KGaA)
• Inventors: Zhu, Fansan, Levin, Nathan W.
• Primary Examiner(s): Eiseman, Adam J
• Application Number:
  US14/772,884
• Publication Number:
  US 20160007884A1
• Time in Patent Office: 2,295 Days
• Field of Search: 600587
• CPC Class Codes: A61B 2560/0425 Ergonomically shaped housings A61B2560/0418 takes precedence
• CPC Class Codes: A61B 2562/0209 Special features of electrodes classified in A61B5/24, A61B5/25, A61B5/283, A61B5/291, A61B5/296, A61B5/053
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/1072 measuring distances on the body, e.g. measuring length, height or thickness A61B5/1076 takes precedence
• CPC Class Codes: A61B 5/4875 Hydration status, fluid retention of the body
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/6828 Leg
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses
• CPC Class Codes: A61B 5/6838 Clamps or clips

Abstract

Apparatus is disclosed for measuring the circumference of a limb of an individual, e.g., the individual'"'"'s arm and/or calf. The apparatus uses one or more magnetic strips which surround the limb and contain magnetic coding of length information. Tension is applied to the magnetic strip by a tensioning assembly, which can be a pressure cuff or a stepping motor, and a magnetic read head reads the magnetic coding of length information from the strip. When used in a bioimpedance analysis procedure, the length information can be used to convert measured voltage differences into normalized bioimpedance values, e.g., resistivity values.

Claims

1. An apparatus for measuring the circumference of a limb of an individual comprising:

two or more magnetic strips, each of which, during use of the apparatus, surrounds the limb and each of which, along its length, comprises magnetic coding of length information;

a magnetic read head for each magnetic strip for reading the magnetic coding of length information from the strip;

at least two current-injecting electrodes for injecting current at a plurality of frequencies, and at least two voltage-measuring electrodes for measuring resulting voltage between the at least two current-injecting electrodes;

at least one of a pre-amplifier and a low pass filter for processing a signal received from the at least two voltage-measuring electrodes;

an A/D converter for converting the signal from the at least one of the pre-amplifier and the low-pass filter;

a digital signal processing unit for calculating at least one of impedance, resistance, and reactance at the plurality of the frequencies of injected current based on the converted signal received from the A/D converter, wherein the digital signal processing unit is configured to receive a single circumference measurement determined from a plurality of circumference measurements received from the magnetic strips;

a tensioning assembly for setting the tension of the two or more magnetic strips; and

a tension sensor for each magnetic strip;

wherein the apparatus is configured to measure the circumference of the limb in a plurality of cross-sectional areas simultaneously for determining the plurality of circumference measurements.

2. The apparatus of claim 1 wherein the apparatus includes two current-injecting electrodes and two voltage-measuring electrodes.

3. The apparatus of claim 1 wherein the tensioning assembly includes a pressure cuff.

4. The apparatus of claim 3 wherein the pressure cuff includes a plurality of inflatable air stripes.

5. The apparatus of claim 4 wherein the inflatable air stripes are separately inflatable.

6. The apparatus of claim 3 wherein the pressure cuff includes two current-injecting electrodes and two voltage-measuring electrodes.

7. The apparatus of claim 1 wherein the apparatus includes a handle-shaped housing which has a middle portion and two side portions which extend away from the middle portion, each side portion having a bottom which contacts the limb during use of the apparatus.

8. The apparatus of claim 7 wherein a magnetic strip is housed in the middle portion of the handle-shaped housing.

9. The apparatus of claim 7 wherein a magnetic strip is housed in each of the side portions of the handle-shaped housing.

10. The apparatus of claim 7 wherein a magnetic strip is housed in the middle portion and each of the side portions of the handle-shaped housing.

11. The apparatus of claim 7 wherein the bottom of each side portion includes a current-injecting electrode and a voltage-measuring electrode.

12. The apparatus of claim 7 wherein the tensioning assembly includes a stepper motor.

13. A method of measuring the circumference of a limb comprising:

applying an apparatus for measuring the circumference of the limb to the limb, the apparatus comprising;

two or more magnetic strips, each of which, during use of the apparatus, surrounds the limb and each of which, along its length, comprises magnetic coding of length information;

a magnetic read head for each magnetic strip for reading the magnetic coding of length information from the strip;

at least two current-injecting electrodes for injecting current at a plurality of frequencies, and at least two voltage-measuring electrodes for measuring resulting voltage between the at least two current-injecting electrodes;

at least one of a pre-amplifier and a low pass filter for processing a signal received from the at least two voltage-measuring electrodes;

an A/D converter for converting the signal from the at least one of the pre-amplifier and the low-pass filter;

a digital signal processing unit for calculating at least one of impedance, resistance, and reactance at the plurality of the frequencies of injected current based on the converted signal received from the A/D converter, wherein the digital signal processing unit is configured to receive a single circumference measurement determined from a plurality of circumference measurements received from the two or more magnetic strips; and

a tensioning assembly for setting the tension of the two or more magnetic strips;

wherein the apparatus is configured to measure the circumference of the limb in a plurality of cross-sectional areas simultaneously for determining the plurality of circumference measurements;

activating the tensioning assembly; and

reading length information from the magnetic strips.

14. The method of claim 13 wherein the limb is an arm.

15. The method of claim 13 wherein the limb is a calf.

16. A method of performing a bioimpedance analysis comprising:

applying an apparatus for measuring a circumference of a limb to the limb, the apparatus comprising;

two or more magnetic strips, each of which, during use of the apparatus, surrounds the limb and each of which, along its length, comprises magnetic coding of length information;

a magnetic read head for each magnetic strip for reading the magnetic coding of length information from the strip;

at least two current-injecting electrodes for injecting current at a plurality of frequencies, and at least two voltage-measuring electrodes for measuring resulting voltage between the at least two current-injecting electrodes;

at least one of a pre-amplifier and a low pass filter for processing a signal received from the at least two voltage-measuring electrodes;

an A/D converter for converting the signal from the at least one of the pre-amplifier and the low-pass filter;

a digital signal processing unit for calculating at least one of impedance, resistance, and reactance at the plurality of the frequencies of injected current based on the converted signal received from the A/D converter, wherein the digital signal processing unit is configured to receive a single circumference measurement determined from a plurality of circumference measurements received from the two or more magnetic strips; and

a tensioning assembly for setting the tension of the two or more magnetic strips,

wherein the apparatus is configured to measure the circumference of the limb in a plurality of cross-sectional areas simultaneously for determining the plurality of circumference measurements;

activating the tensioning assembly;

reading length information from the magnetic strips;

applying current to the limb using the current-injecting electrodes; and

measuring a voltage difference between the voltage-measuring electrodes.

17. The method of claim 16 further comprising:

using the length information from the magnetic strips to convert a measured voltage difference into a normalized bioimpedance value.

18. The method of claim 17 wherein the normalized bioimpedance value is a resistivity value.

19. The method of claim 16 wherein the limb is a calf.