Bioelectric apparatus for monitoring body fluid compartments

• US 5,086,781 A
• Filed: 11/14/1989
• Issued: 02/11/1992
• Est. Priority Date: 11/14/1989
• Status: Expired due to Fees

• Current Assignee: Mark A. Bookspan
• Original Assignee: Mark A. Bookspan
• Inventors: Bookspan, Mark A.
• Primary Examiner(s): SHAY, DAVID M
• Application Number:
  US07/436,476
• Time in Patent Office: 819 Days
• Field of Search: 128/734, 128/774, 128/783, 128/795, 128/796, 128/804
• 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 5/4869 Determining body composition

Abstract

Apparatus for monitoring body water compartmentalization, specifically intracellular and extracellular body water. The apparatus includes a signal generator for generating a sequence of constant current electrical signals at a predetermined number of frequencies ranging between 1 kHz and 2 MHz. Bioelectric contacts are applied to the subject at two sets of points. The resistance drop across the subject is measured by a resistance measuring circuit using one set of contacts. The phase shift between the signals sensed by the sets of contacts is measured by a phase detecting circuit. The current produced by the signal generator is monitored and regulated to maintain the signals at a constant current. The measured data are combined with anthropometric data entered by means of a keyboard, a scale, or other input device, and processed by means of a microprocessor. The micropressor computes a subject'"'"'s extracellular, intracellular and total body water as a function of the bioelectric and anthropometric data.

Claims

1. Apparatus for measuring the body water compartmentalization of a human subject, having potassium ion and sodium ion concentrations which can be used to form a sum, comprising:

means for generating alternating constant current signals at a plurality of predetermined frequencies, and for coupling the alternating constant current signals to a human subject between two selected physical locations thereon;

measuring means coupled to two selected different locations on the subject for determining resistance, phase angle and impedance data associated with the subject at each of the plurality of predetermined frequencies;

data generation means for generating a plurality of signals comprising electrolytic concentration and anthropometric data associated with the subject; and

processor means connected to the data generation means and measuring means for processing the resistance, phase angle, electrolytic concentration and anthropometric data, and for computing intracellular, extracellular and total water volumes of the subject as a function thereof in accordance with predefined equations having a form V_e = b₀ +b₁ [H² /(R_e M)], V_i =b₀ +b₁ (C_i H²)/M+b₂ H² /(R_i M), and V_t =b₀ +b₁ [H² /(R_e M)]+b₂ (C_i H²)/M+b₃ H² /(R_i M) for intracellular, extracellular and total body water volumes, respectively, and where H is the subject'"'"'s height, M is the sum of the concentration of the subject'"'"'s sodium and potassium ions, and b₀, b₁, b₂, and b₃ are predetermined multivariate linear regression coefficients.

2. The apparatus of claim 1 wherein the means for generating alternating constant current signals includes a means for generating sequence of alternating current signals generates which signals at different predetermined frequencies in a range from 1 kHz to 1 MHz.

3. The apparatus of claim 2 wherein the means for generating a sequence of alternating constant current signals includes a first pair of electrodes for applying the alternating constant current signals to the subject, and wherein the measuring means includes a second pair of electrodes for measuring a voltage drop and phase shift of the constant current signals, the measuring means including circuit means for generating direct current signals in response to the voltage drop of the alternating constant current signals, and phase shift measuring means for generating direct current signals in response to the voltage drop and phase shift, and wherein the measuring means is located physically proximate to the pairs of electrodes.

4. The apparatus of claim 3 wherein the measuring means further comprises active electrode pairs that incorporate at least one amplifier coupled to selected electrodes of each electrode pair, which amplifier is substantially colocated at the electrode pair.

17. The apparatus of claim 4 wherein the measuring means comprises active electrodes which imcorporate at least one amplifier coupled to each electrode pair.

5. Apparatus for measuring body water compartmentalization of a human subject, having potassium ion and sodium ion concentrations which can be used to form a sum, comprising:

signal generating means for generating a sequence of alternating current electrical signals having a predetermined constant current, each signal of the sequence having a different predetermined frequency;

means for applying the sequence of signals across a first predetermined pair of locations on the subject;

measuring means coupled to the subject for determining body resistance between a second pair of locations disposed between the first pair of locations on the subject, and for generating a resistance signal and measuring means for determining a phase angle between the applied alternating current signals and voltage signals measured at the second pair of locations and generating a phase shift signal;

data generation means for generating and storing anthropometric and electrolyte concentration data related to the subject;

processor means coupled to the measuring means for processing the body resistance and phase angle data, and coupled to the data generation means for processing the anthropometric and electrolyte concentration data to compute extracellular, intracellular and total water volumes of the subject in accordance with predetermined relationships having a form V_e =b₀ +b₁ [H² /(R_e M)], V_i =b₀ +b₁ (C_i H²)/M+b₂ H² /(R_i M), and V_t =b₀ +b₁ [H² /(R_e M)]+b₂ (C_i H²)/M+b₃ H² /(R_i M) for intracellular, extracellular and total body water volumes, respectively, and where H is the subject'"'"'s height. M is the sum of the concentration of the subject'"'"'s sodium and potassium ions, and b₀, b₁, b₂, and b₃ are predetermined multrivariate linear regression coefficients; and

display means coupled to the processor means for displaying the computed intracellular, extracellular and total water volumes of the subject.

6. The apparatus of claim 5 further comprising current monitoring means for monitoring a magnitude of the current applied to the subject and regulator means connected to the current monitoring means for regulating an output of a power amplifier in response thereto.

7. The apparatus of claim 6 wherein the current monitoring means includes an amplitude detector for measuring an amplitude of the monitored current and for comparing the monitored current to a reference signal, and integrating means connected to the amplitude detector for integrating an output thereof to produce a feedback signal.

8. The apparatus of claim 5 wherein said means for applying the sequence of signals includes a first pair of electrodes coupled to a first predetermined pair of points on the subject.

9. The apparatus of claim 7 wherein the measuring means comprises a phase detector circuit, and wherein a computing circuit includes means for computing an impedance between the second predetermined pair of points at each frequency as a function of resistance and phase shift.

10. The apparatus of claim 9 wherein the processor means comprises a microprocessor having a multiplexer coupled to the current monitoring means, the resistance measuring means and phase shift measuring means, said multiplexer comprising means for coupling current, resistance and phase shift signals to the microprocessor for computation.

11. The apparatus of claim 10 further including an isolation amplifier connected between the current monitoring means and one of the first pair of locations, and between the resistance measuring means and second one of the pair of locations.

12. The apparatus of claim 11 further including an analog-to-digital converter coupled between an output of the multiplexer and the microprocessor for converting measured resistance, current, and phase shift signals into digital signals.

13. The apparatus of claim 12 wherein the anthropometric parameters include total body weight of the subject and distances between the first and second pairs of points, and wherein the means for generating and storing the anthropometric data includes a keyboard and scale.

14. The apparatus of claim 13 further including means for inputting a plurality of scaling factors into the microprocessor, and wherein the microprocessor includes means for outputting scaled values of intracellular and extracellular and total body water volume as a function thereof.

15. The apparatus of claim 14 further including display means for displaying the scaled value of the extracellular and intracellular body water volumes.

16. The apparatus of claim 15 further including isolation amplifiers connected between selected ones of each of the locations of the first and second pairs of locations and the resistance, current, and phase shift measuring means.

18. Apparatus for measuring the body water compartmentalization of a human subject, comprising:

signal generating means for generating a sequence of alternating current, constant current electrical signals at a predetermined number of different frequencies;

means for applying the sequence of constant current electrical signals across a first predetermined pair of points on the subject;

means for sensing the sequence of alternating current, constant current electrical signals applied to the subject;

means for sensing an electrical current at a second predetermined pair of points on the subject, which sensed current is proportional to resistance between the second pair of points;

means for measuring and electronically storing anthropometric and electrolyte concentration data of the subject; and

processor means for processing sensed constant current and sensed electrical signals derived from the first and second pairs of electrodes and the anthropometric and electrolyte concentration data in accordance with predetermined relationships having a form V_e =b₀ +b₁ [H² /(R_e M)], V_i =b₀ +b₁ (C_i H²)/M+b₂ H² /(R_i M), and V_t =b₀ +b₁ [H² /R_e M)]+b₂ (C_i H²)/M+b₃ H² /(R_i M) for entracellular, extracellular and total body water volumes, respectively, and where H is the subject'"'"'s height. M is the sum of the concentration of the subject'"'"'s sodium and potassium ions, and b₀, b₁, b₂ and b₃ are predetermined multivariate linear regression coefficients to compute intracellular, extracellular and total water volumes of the subject as a function thereof.

19. Apparatus for determining body water compartmentalization of a human subject utilizing anthropometric data of the subject, said apparatus comprising:

signal generating means for selectively generating a plurality of alternating constant current signals that each have a different predetermined frequency;

first and second electrodes disposed on the subject and adapted to couple the alternating constant current signals to the subject;

third and fourth electrodes disposed on the subject at selected locations between the first and second electrodes and comprising means for coupling the alternating constant current signals applied to the subject;

processing means coupled to the second, third, and fourth electrodes and electrical ground, for processing the signals coupled thereby including means for generating a first amplitude signal indicative of the amplitude of the signal sensed between the second and third electrodes, and means for generating a second amplitude signal indicative of the amplitude of the signal sensed between the fourth electrode and electrical ground, and means for generation a phase signal indicative of a phase difference between the first and second amplitude signals; and

microprocessor means for containing stored anthropometric data relating to the subject coupled to the processing means, for processing the first and second amplitude signals, the phase signals, and the anthropometric data to compute body water compartmentalization of the subject in accordance with predetermined relationships having a form V_e =b₀ +b₁ [H² /(R_e M)], V_i =b₀ +b₁ (C_i H²)/M-H² /(R_i M), and V_t =b₀ +b₁ [(H² /R_e M)]+b₃ (C_i H²)/M+b₃ H² /(R_i M) for intracellular, extracellular and total body water volumes, respectively, and where H is the subject'"'"'s height, M is the sum of the concentration of the subject'"'"'s sodium and potassium ions and b₀, b₁, b₂, and b₃ are predetermined multivariate linear regression coefficients.

20. A method of determining the body water compartmentalization of a human subject utilizing anthropometric data of the subject, said method comprising the steps of:

generating alternating constant current signals at a plurality of different predetermined frequencies;

coupling the alternating constant current signals to a first plurality of locations on the subject;

sensing the alternating constant current signals applied to the subject;

sensing the phase angle between constant current signals and signals derived at a second plurality of locations on the subject located between the first plurality of locations;

processing the sensed signals to generate a first amplitude signal indicative of an amplitude of a signal sensed between a first plurality of locations, and to generate a second amplitude signal indicative of an amplitude of a signal sensed between the second pluarlity of locations, and to generate a phase signal indicative of a phase difference between the first and second amplitude signals; and

processing the first and second amplitude signals, the phase signals, and the anthropometric data of the subject to compute body water compartmentalization of the subject in accordance with predetermined relationships having a form V_e =b₀ +b₁ [H² /(R_e M)], V_i =b₀ +b₁ (C_i H²)/M+b₂ H² /(R_i M), and V_t =b₀ +b₁ [H² /(R_e M)]+b₂ (C_i H²)/M+b₃ H² /(R_i M) for intracellular, extracellular and total body water volumes, respectively, and where H is the subject'"'"'s height, M is the sum of the concentration of the subject'"'"'s sodium and potassium ions, and b₀, b₁, b₂, and b₃ are predetermined multivariate linear regression coefficients, and b₀, b₁, b₂, and b₃ are predetermined multivariate linear regression coefficients to compute intracellular, extracellular and total water volumes of the subject as a function thereof.

21. A method of determining body water compartmentalization of a subject, said method comprising the steps of:

generating alternating constant current signals at a plurality of different predetermined frequencies;

coupling the alternating constant current signals to a plurality of locations on the subject;

sensing the alternating constant current signals applied to the subject at a second plurality of selected locations;

processing selected ones of the sensed signals to generate a first amplitude signal indicative of an amplitude of a signal sensed between a first set of locations, and to generate a second amplitude signal indicative of an amplitude of a signal sensed between a second set of locations, and to generate a phase signal indicative of a phase difference between the first and second amplitude signals;

processing the first and second amplitude signals, the phase signals, and anthropometric data of the subject to compute a body impedance of the subject as a function of frequency; and

processing the first and second amplitude signals, the phase signals, and the anthropometric data related the subject to compute the body water compartmentalization of the subject in accordance with predetermined relationships having a form V_e =b₀ +b₁ [H² /(R_e M)], V_i =b₀ +b₁ (C_i H²)/M+b₂ H² /(R_i M), and V_t =b₀ +b₁ [H² /(R_e M)]+b₂ (C_i H²)/M+b₃ H² /(R_i M) for intracellular, extracellular and total body water volumes, respectively, and where H is the subject'"'"'s height, M is the sum of the concentration of the subject'"'"'s sodium and potassium ions, and b₀, b₁, b₂, and b₃ are predetermined multivariate linear regression coefficients to compute intracellular, extracellular and total water volumes of the subject as a function thereof.