Apparatus for the in-vivo non-invasive measurement of a biological parameter concerning a bodily fluid of a person or animal

• US 6,339,722 B1
• Filed: 07/13/1998
• Issued: 01/15/2002
• Est. Priority Date: 09/26/1995
• Status: Expired due to Fees

• Current Assignee: A.J. Van Liebergen Holding B.V.
• Original Assignee: A. J. Van Liebergen Holding B.V.
• Inventors: Goovaerts, Hendrik Gebhard, Heethaar, Robert Martin
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): MANTIS MERCADER, ELENI M
• Application Number:
  US09/043,864
• Time in Patent Office: 1,282 Days
• Field of Search: 600/547, 600/481, 600/486, 600/500, 600/504, 600/506, 600/528, 600/546
• US Class Current: 600/547
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• 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: A61B 5/4869 Determining body composition
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

The invention relates to an apparatus for the in vivo non-invasive measurement of a biological parameter concerning a bodily fluid of a person or animal in accordance with a calculation model, wherein the apparatus is provided with connections for at least two pairs of electrodes (2-5, 8-11) to be placed on the skin of a part of the body, a pair of input electrodes (2, 3, 8, 9) for feeding a measuring alternating current to the part of the body and a measuring pair of electrodes (4, 5, 10, 11) for measuring the voltage at the measuring pair of electrodes, comprising a current source (7, 12) providing the measuring alternating current, a transformer (31) for the transformation of the measuring voltage into a bio-impedance signal, being a measure of the bio-impedance of the part of the body, and means for the generation of signals which form a measure for further parameters to be determined with the aid of the calculating model, said signals encompassing a signal forming a measure for the time derivative of the bio-impedance signal. The current source (7, 12) has a minimal radiation configuration and is suitable for generating a measuring current having a constant amplitude on at least two frequencies, a low frequency and a high frequency, in a frequency range of up to about 2000 kHz.

Claims

1. An apparatus for the in-vivo non-invasive measurement of a biological parameter concerning a bodily fluid of a person or animal according to a calculating model, wherein the apparatus is provided with at least two pairs of electrodes adapted to be placed on the skin of a part of the body comprising a pair of input electrodes adapted for feeding a measuring alternating current to the part of the body and a measuring pair of electrodes for measuring the voltage at the electrodes of the measuring pair of electrodes, comprising at least one current source providing the measuring alternating current, a converter for the transformation of the measuring voltage into a bio-impedance signal, being a measure of the bio-impedance of the part of the body, and means for the generation of signals which form a measure for further variables, with the aid of which said parameter can be determined using the calculating model, said signals of said generation of signals encompassing a signal forming a measure for the time derivative of the bio-impedance signal, wherein the at least one current source is electrically symmetrically configured and galvanically separated in relation to ground and is suitable for generating a measuring current having a constant amplitude on at least a low frequency f_l, f_l being in the region of about 1-64 kHz, and a high frequency f_h, f_h being in the region of about 32-2000 kHz wherein fl is smaller than f_h, in a frequency range of up to about 2000 kHz.

2. An apparatus according to claim 1, wherein the parameter is a circulatory parameter of the heart.

3. An apparatus according to claim 1, wherein the parameter is the stroke volume of the heart.

4. An apparatus according to claim 1, wherein the current source is suitable for simultaneous generation of the two frequencies.

5. An apparatus according to claim 1, wherein said apparatus is provided with four pairs of electrodes, two pairs of which serve as an input electrode pair and a measuring electrode pair for taking a transversal bio-impedance measurement at a low and a high frequency and two more pairs which serve as an input electrode pair and a measuring electrode pair for taking a local bio-impedance measurement at a low and a high frequency.

6. An apparatus according to claim 5, wherein said apparatus is provided with connecting means for connecting in series the current source and the transformer, in order to carry out the local bio-impedance measurement and the transversal bio-impedance measurement in sequence.

7. An apparatus according to claim 5, wherein said apparatus comprises a current source or current sources suitable for the simultaneous generation of signals at two low frequencies and two high frequencies.

8. An apparatus according to claim 1, wherein means are provided for the determination of maximum phase shift between the measuring current and the measuring voltage as a function of the frequency.

9. An apparatus according to claim 1, wherein the measurement amplifier for the amplification of the measuring voltage is configured electrically symmetrical and is provided with a galvanic separation in relation to the instrument earth.

10. An apparatus according to claim 9, wherein the measuring amplifier is provided with a galvanic separation which is adapted to be attached to a person.