Body composition measurement device, control method, and control program

Abstract

To provide a body composition measuring device capable of preventing or suppressing variation in measurement results of a subject's body composition, control method and control program.SOLUTION: A body composition measuring device 1 measures, according to measurement conditions, electric impedance based on a voltage signal and a current signal when a plurality of probe currents with different frequencies are input into a subject's body and calculates an impedance locus based on the measured electric impedance. Alternatively, the body composition measurement device 1 calculates a value related to magnitude of the voltage signal, a value related to magnitude of the current signal and an abnormality index, and determines a changeable measurement condition based on at least one of these values.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a body composition measuring device, a control method, and a control program. [Background technology]

[0002] Conventionally, devices that measure a subject's body composition, such as body fat weight and body water content, based on bioelectrical impedance analysis have been known (see, for example, Patent Documents 1 to 4 below). In this device, the bioelectrical impedance of the subject's body is measured based on the voltage generated in the subject's body and the current flowing through the subject's body when a weak alternating current consisting of multiple frequencies is passed through the subject's body, and the body composition is calculated from the measured bioelectrical impedance. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2000-316829 [Patent Document 2] Japanese Patent Application Publication No. 9-154829 [Patent Document 3] Japanese Patent Publication No. 2003-116805 [Patent Document 4] Patent No. 3984332 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, bioelectrical impedance (hereinafter also simply referred to as "electrical impedance") can vary depending on factors such as the subject's physique, body movement, whether or not the arms and armpits are in contact, and whether or not the thighs of both legs are in contact. As a result, the measurement results of the subject's body composition may vary.

[0005] The present invention has been made in view of the above circumstances, and its main objective is to provide a body composition measuring device, a control method, and a control program that can prevent or suppress variations in the measurement results of a subject's body composition. [Means for solving the problem]

[0006] The above objectives of the present invention are achieved by the following means.

[0007] To achieve the above objective, the body composition measuring device of the present invention measures the body composition of a subject according to measurement conditions. The body composition measuring device comprises a current input unit, a voltage detection unit, a current detection unit, a voltage signal amplification unit, a current-to-voltage conversion unit, an electrical impedance calculation unit, an impedance trajectory calculation unit, a body composition information calculation unit, an abnormality index calculation unit, an effective value calculation unit, and a measurement condition determination unit. The current input unit applies a plurality of probe currents of different frequencies to the subject's body. The voltage detection unit detects a voltage signal relating to the voltage generated between predetermined parts of the subject's body when the plurality of probe currents are applied to the subject's body by the current input unit. The current detection unit detects a current signal relating to the current flowing through the subject's body when the plurality of probe currents are applied to the subject's body by the current input unit. The voltage signal amplification unit amplifies the voltage signal detected by the voltage detection unit to a magnitude suitable for electrical impedance measurement. The current-to-voltage conversion unit converts the current signal measured by the current detection unit into a voltage of a magnitude suitable for electrical impedance measurement. The electrical impedance calculation unit calculates information on electrical impedance for each frequency based on the voltage signal amplified by the voltage signal amplification unit and the current signal converted by the current-voltage conversion unit. The impedance trajectory calculation unit calculates an impedance trajectory based on the information on electrical impedance for each frequency measured by the electrical impedance measurement unit. The body composition information calculation unit calculates information on the subject's body composition based on the impedance trajectory calculated by the impedance trajectory calculation unit. The abnormality index calculation unit calculates an abnormality index, which is an index of the abnormality of the impedance trajectory calculated by the impedance trajectory calculation unit. The RMS value calculation unit calculates a value relating to the magnitude of the voltage signal amplified by the voltage signal amplification unit and / or a value relating to the magnitude of the current signal converted by the current-voltage conversion unit. The measurement condition determination unit calculates the value relating to the magnitude of the voltage signal calculated by the RMS value calculation unit. andBased on at least one of the values ​​relating to the magnitude of the current signal calculated by the effective value calculation unit and the abnormality index calculated by the abnormality index calculation unit, the changeable measurement conditions of the body composition measuring device are determined. Prior to the main measurement to measure the composition of the subject's body, a preliminary measurement is performed to determine the measurement conditions. The measurement condition determination unit determines the frequency bands of multiple probe currents applied to the subject's body as the measurement conditions for the main measurement. If the abnormality index calculated by the abnormality index calculation unit in the preliminary measurement exceeds a specified value, the measurement condition determination unit changes the measurement conditions by increasing or decreasing the upper limit on the high-frequency side of the frequency bands of the multiple probe currents and performs the preliminary measurement again. If the abnormality index calculated in the repeated preliminary measurement is less than or equal to the specified value, the frequency band from the repeated preliminary measurement is determined as the measurement condition for the main measurement.

[0009] Furthermore, in order to achieve the above objective, the control method for the body composition measuring device of the present invention measures the body composition of a subject according to measurement conditions. The control method for the body composition measuring device includes the steps of: (a) applying a plurality of probe currents of different frequencies to the subject's body and detecting a voltage signal relating to the voltage generated between predetermined parts of the subject's body when the plurality of probe currents are applied to the subject's body, and a current signal relating to the current flowing through the subject's body; (b) amplifying the voltage signal detected in step (a) to a magnitude used for electrical impedance measurement; (c) converting the current signal detected in step (a) into a voltage of a magnitude used for electrical impedance measurement; and based on the voltage signal amplified in step (b) and the current signal converted in step (c), providing information on electrical impedance for each frequency. Step (d) to calculate; Step (e) to calculate an impedance trajectory based on the information on electrical impedance for each frequency calculated in Step (d); Step (f) to calculate information on the subject's body composition based on the impedance trajectory calculated in Step (e); Step (g) to calculate an abnormality index which is an indicator of the abnormality of the impedance trajectory calculated in Step (e); Step (h) to calculate a value relating to the magnitude of the amplified voltage signal in Step (b) and / or a value relating to the magnitude of the current signal flowing through the subject's body detected in Step (a); and the value relating to the magnitude of the voltage signal calculated in Step (h). and The method includes step (i) determining the modifiable measurement conditions of the body composition measuring device based on at least one of the values ​​relating to the magnitude of the current signal and the abnormality index calculated in step (g). Prior to the main measurement of the subject's body composition, a preliminary measurement is performed to determine the measurement conditions. In step (i), the frequency bands of multiple probe currents applied to the subject's body are determined as measurement conditions for the main measurement. In step (i), if the abnormality index calculated in step (g) exceeds a specified value in the preliminary measurement, the measurement conditions are changed by increasing or decreasing the upper limit of the high-frequency side in the frequency bands of the multiple probe currents, and the preliminary measurement is performed again. If the abnormality index calculated in the repeated preliminary measurement is less than or equal to the specified value, the frequency band from the repeated preliminary measurement is determined as the measurement condition for the main measurement. [Effects of the Invention]

[0011] According to the body composition measuring apparatus of the present invention, it is possible to suppress variations in the measurement results of a subject's body composition caused by factors such as the subject's physique, body motion, and the presence or absence of contact between the arm and the armpit. [Brief Description of the Drawings]

[0012] [Figure 1] 1 is a block diagram illustrating a schematic configuration of a body composition measuring apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a conceptual diagram illustrating a usage state of the body composition measuring apparatus shown in FIG. 1. [Figure 3] FIG. 3 is a schematic block diagram illustrating the hardware configuration of the control unit shown in FIG. 1. [Figure 4] FIG. 4 is a graph showing an example of an impedance trajectory. [Figure 5] FIG. 5 is a flowchart illustrating main processing of a control method for the body composition measuring apparatus. [Figure 6] FIG. 6 is a subroutine flowchart illustrating details of processing of preliminary measurement (S102) in the flowchart shown in FIG. 5. [Figure 7A] FIG. 7A is a subroutine flowchart illustrating details of processing of main measurement (S103) in the flowchart shown in FIG. 5. [Figure 7B] FIG. 7B is a subroutine flowchart continuing from FIG. 7A. [Figure 8] FIG. 8 is a subroutine flowchart illustrating processing (S322) for determining presence or absence of an abnormality in electrical impedance measurement shown in FIG. 7B. [Figure 9] FIG. 9 is a schematic diagram illustrating the flow of current (current signal) in cells in a living body according to frequency. [Figure 10] FIG. 10 is a schematic electrical equivalent circuit diagram of the living body shown in FIG. 9. [Figure 11A] FIG. 11 is a subroutine flowchart illustrating details of processing of main measurement (S103) in a second embodiment. [Figure 11B] This is a subroutine flowchart following Figure 11A. [Figure 12] This is a subroutine flowchart illustrating the details of the measurement process (S103) in the third embodiment. [Figure 13] This is a conceptual diagram illustrating the usage of a body composition measurement device in a verification experiment of measurement accuracy using pigs. [Figure 14A] This graph illustrates the results of verifying V-POWER during a measurement time verification experiment. [Figure 14B] This graph illustrates the results of verifying I-POWER during a measurement time verification experiment. [Figure 15A] This graph illustrates the results of verifying the variation error (%) of R0 in a measurement time verification experiment. [Figure 15B] This graph illustrates the results of verifying the variation error (%) of R∞ in a measurement time verification experiment. [Figure 15C] This graph illustrates the results of verifying the average value of an anomaly indicator in a measurement time verification experiment. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. Also, the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios.

[0014] (First embodiment) Figure 1 is a block diagram illustrating the schematic configuration of a body composition measurement device according to the first embodiment, and Figure 2 is a conceptual diagram showing the usage state of the body composition measurement device. Figure 3 is a schematic block diagram illustrating the hardware configuration of the control unit shown in Figure 1.

[0015] <Configuration of Body Composition Measurement Device 1> Body composition analyzer 1 is a device for measuring the body composition of a subject (patient, care recipient, etc.) body E. Body composition analyzer 1 may be a portable body composition analyzer powered by a battery. A portable body composition analyzer allows for the measurement of a subject's body composition in any location, such as at the bedside, in an outpatient clinic, or during a home visit.

[0016] As shown in Figure 1, the body composition measurement device 1 comprises a control unit 10, a current measurement unit 20, a signal output unit 30, a voltage measurement unit 40, a recording unit 62, an input unit 63, a speaker 64, a display unit 65, and a memory 66. The electrical impedance calculation unit 120, the current measurement unit 20, the signal output unit 30, and the voltage measurement unit 40 constitute the electrical impedance measurement unit 50.

[0017] The recording unit 62 may be composed of, for example, RAM (Random Access Memory), SSD (Solid State Drive), or HDD (Hard Disk Drive).

[0018] The input unit 63 includes, for example, a touch panel, various keys, and switches, and accepts instructions from an operator such as a medical professional, various settings, and information about the subject. Instructions from the operator include, for example, instructions to start / end the measurement, and various settings include, for example, settings for the output method and display method of the measurement results. Information about the subject includes the subject's gender, age, height, weight, medical history, etc.

[0019] The display unit 65 has a display located on one side of the housing of the body composition measurement device 1. The display unit 65 may also be equipped with light-emitting diodes (LEDs) or the like to visually notify abnormalities or other issues.

[0020] <Surface electrodes Lc, Hc, Lp, Hp> As shown in Figure 2, surface electrodes Lc and Hc, and surface electrodes Lp and Hp are attached (by adhesive sheets, etc.) to predetermined parts of the subject's body E, and these surface electrodes are connected to the body composition measurement device 1 via connecting cables 2A to 2D. More specifically, surface electrode Lc is attached to the top of the subject's right foot E during measurement, and surface electrode Hc is attached to the back of the subject's right hand E during measurement. Surface electrode Lc is connected to the current measurement unit 20, and surface electrode Hc is connected to the signal output unit 30. Surface electrode Hc is paired with surface electrode Lc. Also, surface electrode Lp is attached to the top of the subject's right foot E during measurement, and surface electrode Hp is attached to the back of the subject's right hand E during measurement. Surface electrode Hp is paired with surface electrode Lp.

[0021] <Configuration of the control unit 10> As shown in Figure 3, the control unit 10 includes a CPU (Central Processing Unit) 11, ROM 12, RAM 13, auxiliary storage unit 14, and input / output interface 15. The auxiliary storage unit 14 may be, for example, an SSD or an HDD. The CPU 11, ROM 12, RAM 13, and auxiliary storage unit 14 constitute a computer.

[0022] The CPU 11 implements various functions by loading control programs, which are pre-stored in the ROM 12 or auxiliary storage unit 14, into the RAM 13 and executing them. The ROM 12 is a non-volatile memory. The ROM 12 stores various parameters necessary for the CPU 11's calculation processing. The RAM 13 is a volatile memory that temporarily stores the results of calculation processing by the CPU 11 and various data. The auxiliary storage unit 14 stores programs such as the OS (Operating System) and control programs, as well as the results of calculation processing by the CPU 11. The input / output interface 15 is an input / output interface for sending and receiving data between the CPU 11 and the system unit (not shown).

[0023] The control unit 10 functions as an impedance trajectory calculation unit 110, an electrical impedance calculation unit 120, a judgment unit 130, a notification unit 140, a body composition measurement unit 150, an abnormality determination unit 160, an effective value calculation unit 170, a measurement condition determination unit 180, and a mode control unit 190, as the CPU 11 executes a control program (see Figure 1 again).

[0024] <Electrical impedance measurement unit 50> The electrical impedance measurement unit 50 generates multiple probe currents of different frequencies and applies each of these probe currents to the subject's body E. When each probe current of each frequency is flowing through the subject's body E, the electrical impedance of the subject's body E is calculated from the relationship between the probe current and the voltage between the electrodes. The following description mainly focuses on the calculation of electrical impedance, but the unit may also be configured to calculate electrical admittance and / or electrical impedance, which are the reciprocals of electrical impedance.

[0025] <Signal output section 30> The signal output unit 30 functions as a current inlet and, in accordance with instructions from the control unit 10, supplies a multi-frequency probe current (hereinafter referred to as "multi-frequency current") Ib to the subject's body E. The multi-frequency current is a plurality of probe currents with different frequencies. The multi-frequency probe current can be, for example, a superposition of alternating currents with frequencies increasing by 2.5 kHz increments from 2.5 kHz to 350 kHz. The signal output unit 30 includes a measurement signal generator 31 and an output buffer 32.

[0026] The measurement signal generator 31 outputs a measurement signal (current) Ia to the output buffer 32 at predetermined intervals according to the instructions of the CPU 11. The period at which the measurement signal generator 31 outputs the measurement signal Ia can be, for example, about 800 nsec. The measurement signal Ia is a signal that changes continuously at predetermined frequency intervals within the above predetermined period. The measurement signal Ia may change at frequency intervals of 15 kHz in the range of 1 kHz to 400 kHz, for example. Alternatively, it may be a measurement signal that includes many frequency components, such as the M-sequence signal shown in Japanese Patent Application Publication No. 10-14898.

[0027] More specifically, the measurement signal generator 31 has an M-sequence signal generator (not shown), a square wave generator, and a time division converter, and according to the instructions of the CPU 11, it generates a period T*(2 n -1) A time-division M-sequence signal (where n is a positive integer) and a signal with period T*N=2*W (where N is an integer greater than or equal to 2) where the first W period is 1 and the remaining W periods are 0 are generated. For example, an M-sequence signal generator operating at 1.25MHz with period 511(=2 n -1) The M-sequence signal is generated, and the square wave generator generates a square wave with a period (32 / 1.25MHz) and a duty cycle of 50%. The time divisioner divides 0.8μsec = 1 / 1.25MHz into four equal parts and provides a control signal to switch the signal so that the M-sequence signal is output for the first three time periods (0.6μsec) and the square wave is output for the last 0.2μsec.

[0028] Furthermore, the measurement signal generator 31 can change the frequency bandwidth of the multi-frequency probe current according to the instructions of the CPU 11. For example, it can be set to 1 to 1,000 kHz, or 2.5 to 350 kHz, 2.5 to 500 kHz, 2.5 to 750 kHz, or 2.5 to 1,000 kHz. These are just examples, and the specification may allow for fine adjustment in increments of 0.5 kHz or 1 kHz.

[0029] The output buffer 32 outputs the input measurement signal Ia as a multi-frequency current Ib to the surface electrode Hc while maintaining a constant current state. As a result, the multi-frequency current Ib flows through the subject's body E. The current value of the multi-frequency current Ib is not particularly limited. For example, the current value of the multi-frequency current Ib can be around 100 to 800 μA. The output buffer 32 applies the measurement signal Ia through a limiting resistor that is sufficiently larger than the electrical resistance of the human body so that the measurement signal Ia remains basically constant even when the subject changes. Alternatively, the output buffer 32 may be configured to have an analog filter, and the measurement signal Ia from which high-frequency noise has been removed by the analog filter may be applied.

[0030] <Current measurement section 20> The current measurement unit 20 outputs a voltage signal Vb obtained by converting a multi-frequency current Ib into a voltage. The current measurement unit 20 includes a current detection unit 24, an I / V converter 23, a BPF (bandpass filter) 22, and an A / D converter 21.

[0031] The I / V converter 23 is a current / voltage converter that functions as a current-voltage conversion unit. The current detection unit 24 detects the multi-frequency current Ib flowing through the subject's body E when the multi-frequency current is applied to the subject's body E by the signal output unit 30, converting it into a current signal. The I / V converter 23 converts the multi-frequency current Ib flowing between the surface electrode Hc and surface electrode Lc detected by the current detection unit 24 into a voltage Vb of a magnitude used for electrical impedance measurement using a gain Gi. The I / V converter 23 is configured to change the gain Gi according to the instructions of the control unit 10. The I / V converter 23 outputs the obtained voltage Vb to the BPF 22.

[0032] The BPF22 is a bandpass filter. The BPF22 cuts out unwanted frequency bands from the voltage signal Vb and outputs it to the A / D converter 21. The passband of the BPF22 can be appropriately selected according to the specifications of the body composition measurement device 1. For example, the passband of the BPF22 can be set to approximately 1kHz to 800kHz.

[0033] The A / D converter 21 converts the analog voltage Vb into a digital voltage signal Vb according to the digital conversion instructions from the control unit 10. The digital voltage signal Vb is stored in memory 66 in a time-series manner as voltage data, by being synchronously added with the synchronously added data up to one cycle prior to the M-sequence signal.

[0034] The memory 66 transmits and receives stored data to and from the control unit 10 upon request from the control unit 10. Specifically, it transmits and receives data to and from the RMS value calculation unit 70 and the electrical impedance calculation unit 120. The memory 66 can be configured using, for example, SRAM.

[0035] The control unit 10 functions as a synchronous adder and performs synchronous addition on the voltage signal Vb data sent from the current measurement unit 20 in order to remove, for example, quantum errors from A / D conversion by the A / D converter 21. More specifically, the synchronous adder synchronously adds the synchronously added data of the M-sequence signal up to one cycle ago with the data after the current A / D conversion and stores it in the memory 66. In other words, the memory 66 stores the M-sequence signal for one cycle after the synchronous addition. Subsequently, the data after the next A / D conversion is similarly synchronously added to the M-sequence signal for one cycle stored in the memory 66 and overwrites the memory 66. This synchronous addition process is repeated a certain number of times (N times).

[0036] Alternatively, the A / D converted data may be stored directly in memory 66 and later subjected to synchronous addition processing. However, in this case, time is required to perform synchronous addition processing on the enormous amount of stored data, and due to limitations in the memory capacity of the memory used to store the data, it may not be possible to obtain a sufficient number of synchronous addition operations.

[0037] If we let d(i) be the i-th data in memory 66, and D(n) be the synchronous sum (n=0 to 1021), then D(n) = Σd(2*511*m+n). Here, the summation symbol Σ represents the summation from m=0 to 31.

[0038] Furthermore, the number of repetitions for synchronous addition is stored in advance in the auxiliary storage unit 14. Alternatively, the system may be configured so that the operator can set the number of repetitions for synchronous addition through the input unit 63.

[0039] In this manner, the signal output unit 30 and the current measurement unit 20 input a digital voltage signal Vb corresponding to the current Ib to the electrical impedance calculation unit 120. On the other hand, the digital voltage signal Vp is input to the electrical impedance calculation unit 120 from the voltage measurement unit 40.

[0040] <Voltage measurement unit 40> The voltage measurement unit 40 measures the voltage generated between predetermined parts of the subject's body E when a multi-frequency current is applied to the subject's body E by the signal output unit 30. The voltage measurement unit 40 includes a voltage detection unit 44, a differential amplifier 43, a band-pass filter 42, and an A / D converter 41.

[0041] The voltage detection unit 44 detects a voltage signal relating to the voltage between the surface electrode Hp and the surface electrode Lp. The differential amplifier 43 functions as a voltage signal amplifier and amplifies the voltage between the surface electrode Hp and the surface electrode Lp detected by the voltage detection unit 44 to a voltage Vp of a magnitude used for electrical impedance measurement by a gain Gd and outputs it. The differential amplifier 43 is configured to change the gain Gd according to the instructions of the control unit 10. The differential amplifier 43 outputs the voltage Vp to the BPF 42.

[0042] The BPF42 cuts a predetermined bandwidth of signal from the input voltage signal Vp and outputs it to the A / D converter 41. The passband of the BPF42 can be appropriately selected according to the specifications of the body composition measurement device 1. For example, the passband of the BPF42 can be set to approximately 1kHz to 800kHz.

[0043] The A / D converter 41 converts the analog voltage Vp into a digital voltage signal Vp according to the digital conversion instruction from the control unit 10. The digital voltage signal Vp is stored in the memory 66 as voltage data, synchronously added with the synchronous sum data up to one cycle prior to the M-sequence signal. Note that the synchronous summing of voltage data is the same as that for the voltage signal Vb obtained by conversion from current, so a detailed explanation is omitted.

[0044] The electrical impedance calculation unit 120 calculates the electrical impedance of the subject's body E based on the input digital voltage signals Vb and Vp, using the electrical impedance method. More specifically, the electrical impedance calculation unit 120 uses data based on the voltage signals Vb and Vp, stored in the memory 66, after repeating the synchronous addition process a specified number of times, to calculate the electrical impedance of the subject's body E. In this case, if the measurement signal contains many frequency components, such as an M-sequence signal, the electrical impedance calculation unit 120 first performs a Fourier transform on the voltages Vb and Vp, which are functions of time. This yields Vp(f) and Vb(f), which are functions of frequency. Note that if the measurement signal is a signal whose frequency changes constantly, this process is unnecessary because Vp(f) and Vb(f) are directly measured as functions of frequency. Subsequently, after averaging is performed on the voltages Vp(f) and Vb(f), the electrical impedance Z(f) = Vp(f) / Vb(f) for each frequency is calculated.

[0045] The electrical impedance calculation unit 120 stores the input digital voltage signals Vb and Vp, and the calculated electrical impedance in the RAM 13, and outputs them to the impedance trajectory calculation unit 110, the judgment unit 130, and the body composition measurement unit 150. Hereinafter, the voltage signals Vb and Vp will also be referred to as measurement data. The principle of the electrical impedance method will be described later.

[0046] The impedance trajectory calculation unit 110 calculates the center coordinates and radius of the impedance trajectory from the electrical impedance at each frequency input from the impedance calculation unit 120. The impedance trajectory calculation unit 110 further calculates the resistance R∞ when the probe current frequency is ∞, the resistance R0 when the probe current frequency is 0, R∞ / R0, and the critical frequency fc. The impedance trajectory calculation unit 110 outputs the impedance trajectory, R∞, R0, R∞ / R0, and critical frequency fc to the judgment unit 130, the body composition measurement unit 150, and the abnormality determination unit 160.

[0047] The impedance locus calculation unit 110 calculates the impedance locus using the least squares method. The resistance R∞ and R0 can be calculated by finding the intersection point of the calculated impedance locus and the reactance X=0. The critical frequency fc can be calculated from the frequencies corresponding to the electrical impedance measurements located on both sides of the point on the impedance locus where the reactance is smallest.

[0048] Figure 4 is a graph showing an example of an impedance trajectory. In the graph shown in Figure 4, the horizontal axis is resistance R, and the vertical axis is reactance X. The black circles ("●") or white circles ("〇") represent measurement points (measured values) of electrical impedance at each frequency. In this figure, the black circles are measurement points at frequencies higher than the critical frequency fc (also called "high frequency"), and the white circles are measurement points at frequencies lower than the critical frequency fc (also called "low frequency"). In the example shown in Figure 4, the 350KHz dot is the measured value when the highest frequency current was applied, and the 2.5KHz dot is the measured value when the lowest frequency current was applied.

[0049] The impedance locus is a curve calculated to fit the electrical impedance measurements at each frequency. Typically, the impedance locus is approximately a Cole-Cole arc.

[0050] At very low and very high frequencies, the reactance X is virtually zero, and the electrical impedance Z is virtually equal to the resistance R. Therefore, of the intersections of the impedance locus and X=0, the one with the greater resistance is the resistance R0 at frequency 0, and the one with the smaller resistance is the resistance R∞ at frequency ∞. R0 is considered to reflect the extracellular fluid volume, and R∞ is considered to reflect the body water volume.

[0051] The determination unit 130 determines whether or not there is an abnormality in the electrical impedance measurement based on at least one of the distribution of the electrical impedance measurement values ​​with respect to the impedance trajectory at each frequency and the magnitude of the radius of the impedance trajectory.

[0052] If the determination unit 130 determines that there is no abnormality in the electrical impedance measurement, it outputs an OK signal indicating "no abnormality" to the body composition measurement unit 150 and the notification unit 140. On the other hand, if the determination unit 130 determines that there is an abnormality in the electrical impedance measurement, it outputs an NG signal indicating "abnormality" to the body composition measurement unit 150 and the notification unit 140.

[0053] The notification unit 140 does not provide notification when an OK signal is input, but when an NG signal is input, it notifies the subject or the operator of the body composition measurement device 1 of the abnormality. The method of notifying of the abnormality is not particularly limited. For example, the abnormality may be notified by outputting an abnormality notification sound from the speaker 64, by displaying on the display unit 65 that there was an abnormality in the electrical impedance measurement, or by a combination of these methods.

[0054] The body composition measurement unit 150 calculates and measures body composition based on the calculated electrical impedance, the impedance trajectory, and the subject information input from the input unit 63. The body composition measurement unit 150 measures body composition at least when an OK signal is input. Alternatively, the body composition measurement unit 150 may measure body composition only when an OK signal is input, or it may measure body composition both when an OK signal is input and when an NG signal is input. In this embodiment, the case in which body composition is measured only when an OK signal is input will be explained as an example.

[0055] The body composition measurement unit 150 functions as a body composition information calculation unit and outputs the measured body composition to the display unit 65. The display unit 65 displays the measured body composition. If the judgment unit 130 outputs an NG signal to the notification unit 140, the display unit 65 displays a message indicating that there was an abnormality in the electrical impedance measurement and that the body composition measurement has been stopped.

[0056] Furthermore, the body composition measurement unit 150 also outputs the measured body composition to the recording unit 62. The recording unit 62 records the measured body composition.

[0057] Furthermore, the specific measurement method for body composition is not particularly limited, and known methods can be used. For example, body water content can be measured by regression analysis. Specifically, the conductive part of the human body, i.e., the body water portion, is assumed to be a cylinder with length L and cross-sectional area S. In this case, the resistance of the conductive part of the human body is proportional to length L and inversely proportional to cross-sectional area S. Therefore, R = ρL / S, which can be rearranged to S = ρL / R. Substituting this into volume V = LS, the volume V of the conductive part of the human body is ρL 2 It is measured as / R. Therefore, total body water (TBW) is TBW = α + βL 2 Body water content can be measured using the formula / R. Here, α and β are statistically determined constants. Furthermore, by adding human characteristic data such as height to the above formula, the accuracy of the measured body water content can be improved. Specifically, body water content (TBW) is given by TBW = α + βL2 By measuring using the formula / R+γW+δAGE, more accurate measurement of body water content becomes possible. Here, W is body weight and AGE is age. Lean body mass (FFM) can also be measured using a similar method.

[0058] The abnormality determination unit 160 functions as an abnormality index calculation unit and calculates an abnormality index, which is an indicator of the abnormality of the impedance trajectory calculated by the impedance trajectory calculation unit 110. The specific method for calculating the abnormality index will be described later. The abnormality determination unit 160 determines that the impedance trajectory is abnormal if the abnormality index exceeds a predetermined specified value (first threshold), while determining that the impedance trajectory is not abnormal if the abnormality index is less than or equal to the specified value. The specified value may be, for example, 0.004.

[0059] The RMS value calculation unit 170 calculates a value relating to the magnitude of the voltage signal Vp (hereinafter referred to as "V-POWER") and / or a value relating to the magnitude of the voltage signal Vb corresponding to the current Ib (i.e., the magnitude of the current signal) (hereinafter referred to as "I-POWER"). V-POWER and I-POWER may be, for example, the RMS value Vpa of the voltage signal Vp and the RMS value Vba of the voltage signal Vb, respectively.

[0060] For example, the RMS calculation unit 170 calculates the V-POWER of the voltage signal Vp by using the data obtained after repeating the synchronous addition process a predetermined number of times on the voltage signal Vp input from the voltage measurement unit, and then performing digital signal processing on this data. Furthermore, the RMS calculation unit 170 calculates the I-POWER of the voltage signal Vb by using the data obtained after repeating the synchronous addition process a predetermined number of times on the voltage signal Vb input from the current measurement unit, and then performing digital signal processing on this data. More specifically, the RMS calculation unit 170 calculates V-POWER and I-POWER by calculating the root mean square (RMS) for all sampled data based on the definition of the RMS value of an AC signal.

[0061] On the other hand, in this embodiment, a current Ib consisting only of the AC component is applied to the subject's body E via the capacitor of the output buffer 32. The RMS value is equal to the standard deviation σ of the AC signal data, which has no DC component and an average value of 0. Therefore, the RMS value calculation unit 170 calculates V-POWER and I-POWER, respectively, by calculating the standard deviation σ of the digital voltage signals Vp and Vb.

[0062] Here, it is desirable that V-POWER be as large as possible within the processing range of the circuit. For example, the upper threshold of V-POWER can be set within a range where almost all data falls within ±3σ. If the resolution of the A / D converter 41 is 8 bits, V-POWER can preferably be set to a value of 20 to 40, and more preferably to 30 to 40.

[0063] The output buffer 32 has a limiting resistor that is sufficiently larger than the electrical resistance of the human body, and is configured to apply the measurement signal Ia through the limiting resistor so that the measurement signal Ia remains essentially constant even when the subject being measured changes to another subject. When the resolution of the A / D converter 21 is 8 bits, I-POWER can preferably be set to a value of 20 to 40, and more preferably to 30 to 40.

[0064] On the other hand, I-POWER can change depending on the contact state of the surface electrodes attached to the subject's body E. Therefore, based on the measured I-POWER, the control unit 10 can detect abnormalities such as any of the surface electrodes being measured detaching from the subject's body E.

[0065] The measurement condition determination unit 180 determines the changeable measurement conditions of the body composition measurement device 1 based on at least one of V-POWER, I-POWER, and an anomaly index. Changeable measurement conditions in the body composition measurement device 1 may include, for example, the gain Gd of the differential amplifier 43, Gi of the I / V converter 23, the frequency band Bw (or upper limit frequency) for electrical impedance measurement, and the number of data points Np for creating the electrical impedance trajectory. However, the number of data points Np is determined according to the frequency band Bw. The upper limit frequency is the upper limit frequency of the frequency band Bw. The method and specific examples for determining the measurement conditions will be described later.

[0066] In this embodiment, the body composition measuring device 1 is configured to operate in one of three measurement modes: a first measurement mode, a second measurement mode, or a third measurement mode. The mode control unit 190 controls whether to perform the measurement using one of the three measurement modes.

[0067] The first measurement mode is a measurement mode in which the electrical impedance measurement unit 50 performs a synchronous addition process on the voltage signal Vb obtained by converting the multi-frequency current Ib input from the current measurement unit 20 into a voltage, and on the voltage signal Vp input from the voltage measurement unit 40, with the number of repetitions of this process being predetermined (for example, the synchronous addition process of the M-sequence signal data from the previous cycle and the M-sequence signal for the next cycle is repeated a total of 128 times × 40 times. The 128 processes are performed to cancel pseudo-noise caused by the square wave, and the 40 repetitions are performed because increasing the number of repetitions increases the rate of asynchronous noise removal). Hereinafter, the first measurement mode may also be referred to as the normal mode. The second measurement mode is a measurement mode with fewer repetitions than the first measurement mode, and the third measurement mode is a measurement mode with more repetitions than the first measurement mode. For example, the number of repetitions for the second measurement mode may be 128 × 30, and the total number of repetitions for the third measurement mode may be 128 × 50. The number of repetitions for the second measurement mode may be set as a multiple of the number of repetitions for the first measurement mode, such as 2 / 3 or 1 / 2. Similarly, the number of repetitions for the third measurement mode may be set as a multiple of the number of repetitions for the first measurement mode, such as 3 / 2 or 2. In the case of 128 × 40 repetitions, the number of repetitions may increase or decrease from 128, or from 40.

[0068] For example, the mode control unit 190 starts measuring the subject's body composition from the second measurement mode. When the mode control unit 190 performs a measurement using the second measurement mode, if the abnormality determination unit 160 determines that the impedance trajectory of the second measurement mode is abnormal, i.e., if the abnormality index exceeds a specified value, it performs the measurement again with an increased number of repetitions of the synchronous addition process compared to the second measurement mode. The increment Δn of the number of repetitions is not particularly limited (for example, 128 times × (40 + 1) times, 128 times × (40 + 5) times, etc.).

[0069] Furthermore, if the abnormality determination unit 160 determines that the impedance trajectory of the first measurement mode is abnormal when the mode control unit 190 performs a measurement using the first measurement mode, it may perform a measurement again using the third measurement mode. More specifically, the mode control unit 190 first performs a measurement using the second measurement mode, and if the abnormality determination unit 160 determines that the impedance trajectory of the second measurement mode is abnormal, it transitions to a measurement using the first measurement mode. If the abnormality determination unit 160 determines that the impedance trajectory of the first measurement mode is abnormal, it transitions to a measurement using the third measurement mode.

[0070] (Control method for body composition measurement device 1) The control method for the body composition measurement device in this embodiment will be described below with reference to Figures 5 to 7B. Figure 5 is a flowchart illustrating the processing procedure of the main process. The processing shown in the flowchart is realized by the CPU 11 executing the control program.

[0071] [Main process] As mentioned above, electrical impedance can vary depending on factors such as the subject's physique, body movement, whether or not the arms are in contact with the armpits, and whether or not the thighs of both legs are in contact. Therefore, if the set measurement conditions are not suitable for measuring the subject's electrical impedance, the accuracy of the body composition measurement may not be sufficient. For example, if the subject moves a lot during measurement, is extremely swollen, or is extremely thin, the measurement of electrical impedance may not be stable, and there is a high possibility of discrepancies in the measurement results in the impedance trajectory. This is because if the subject is extremely swollen, the internal resistance may be significantly low, and if the subject is extremely thin, the surface resistance may be high.

[0072] Therefore, in this embodiment, prior to the main measurement that measures the composition of the subject's body, a preliminary measurement (hereinafter referred to as "preliminary measurement") is performed to determine the measurement conditions for the main measurement. In this specification, preliminary measurement means a measurement performed to determine the measurement conditions for the main measurement that will be performed after the preliminary measurement, and which does not have the direct purpose of calculating information about body composition. The main measurement means a measurement that is performed in accordance with the measurement conditions determined by the preliminary measurement and which calculates information about body composition.

[0073] First, the control unit 10 sets the measurement conditions for preliminary measurement (step S101). The control unit 10 sets each measurement condition to its initial value for preliminary measurement. For example, the initial value of the gain Gd of the differential amplifier 43 may be set so that V-POWER is approximately 40 (approximately the maximum value). Note that the initial value of the gain Gd of the differential amplifier 43 may start from the maximum value. Also, the initial value of Gi of the I / V converter 23 may be set so that I-POWER is approximately 40 (approximately the maximum value). Furthermore, the initial value of the frequency band Bw for electrical impedance measurement may be set to, for example, 2.5kHz to 350kHz. Also, for example, the number of data points Np is set so that the frequency band Bw is measured every 2.5kHz. When the frequency band Bw is, for example, 2.5kHz to 350kHz, the control unit 10 sets the number of data points Np to 350kHz / 2.5kHz = 140 points.

[0074] Next, the control unit 10 performs a preliminary measurement to determine the measurement conditions for the main measurement (step S102). In this embodiment, the control unit 10 performs the preliminary measurement under conditions with fewer synchronous addition repetitions than the main measurement. This shortens the time required for the preliminary measurement. In addition, the preliminary measurement can also shorten the time required for the preliminary measurement by performing the steps up to the calculation of I-POWER and V-POWER, and determining the measurement conditions without performing the calculation of electrical impedance for each frequency, the calculation of impedance trajectories, and the calculation of body composition. Figure 6 shows the case where the preliminary measurement is completed at the steps up to the calculation of I-POWER, V-POWER, and the anomaly index.

[0075] In preliminary measurements, measurement conditions are selected that result in the anomaly index being below a specified value (lower is preferable) and V-POWER being maximized without exceeding a specified value (upper limit). Furthermore, if any of the anomaly index, V-POWER, or I-POWER is deemed inappropriate, the measurement conditions are reviewed. Specific processing procedures will be described later.

[0076] Next, the control unit 10 performs the main measurement (step S103). At this time, the control unit 10 sets the measurement conditions to those determined in the preliminary measurement, fixes the measurement conditions, and then performs the main measurement of body composition.

[0077] [Preliminary measurement process] Figure 6 is a subroutine flowchart illustrating the details of the preliminary measurement (S102) process in the flowchart of Figure 5. The processing of the subroutine flowchart shown in this figure is realized by the CPU 11 executing a control program.

[0078] First, the signal output unit 30, which functions as a current input unit, sets the frequency band of the probe current to be applied to the subject (S201) and applies the probe current using the M series to the subject (S202). Then, the current detection unit and the voltage detection unit detect a voltage signal relating to the voltage between predetermined parts of the subject's body E, and a current signal relating to the current flowing (steps S203 and S204).

[0079] Next, the voltage signal amplification unit (differential amplifier 43) amplifies the detected voltage signal (step S206). The voltage signal amplification unit amplifies the voltage signal detected in step S204 to a voltage Vp of a magnitude suitable for electrical impedance measurement.

[0080] In parallel, the current-voltage conversion unit (I / V converter 23) converts the detected current signal into a voltage signal (step S205). The current-voltage conversion unit converts the current signal detected in step S203 into a voltage signal Vb used for electrical impedance measurement. The obtained voltage signals Vp and Vb are filtered by BPFs 42 and 22, respectively, to remove signals in a predetermined bandwidth, including noise (steps S207 and S208). Furthermore, A / D conversion is performed on these data (steps 209 and S210), and the voltage signal and current signal are averaged by synchronous summation of the M-sequence signal data up to one cycle prior and the A / D converted data (steps S211 and S212) to improve the S / N ratio. Subsequently, the RMS value calculation unit 170 calculates V-POWER using the averaged voltage signal Vp and I-POWER using the averaged voltage signal Vb (steps S213 and S214). Then, a Fourier transform is performed on the voltage signals Vp and Vb, which are functions of time, to convert them into functions of frequency (steps S215, S216).

[0081] In reality, the current input unit, voltage signal amplification unit, current-to-voltage conversion unit, and RMS value calculation unit 170 are implemented by hardware (electronic circuits), so the processes in steps S201 to S216 are performed simultaneously. That is, the signal processing related to current and the signal processing related to voltage are performed in parallel and simultaneously.

[0082] The electrical impedance measurement unit 50 calculates information about the electrical impedance for each frequency based on Vp and Vb, which are functions of frequency (step S217), and calculates the impedance trajectory by performing curve fitting using the least squares method calculation means (step S218).

[0083] Next, the abnormality determination unit 160 calculates an abnormality index (step S219). The abnormality determination unit 160 calculates the abnormality index based on the impedance trajectory calculated in step S218. In the present embodiment, the variation of the impedance measurement value at each frequency with respect to the impedance trajectory is calculated as the abnormality index. That is, a larger abnormality index indicates greater variation and lower fitting accuracy of the measurement data, and a smaller abnormality index indicates less variation and higher fitting accuracy of the measurement data.

[0084] More specifically, the abnormality determination unit 160 calculates a distance e(f) in a predetermined direction between the electrical impedance Z(f) measured at frequency (f) and the impedance trajectory. The distance e(f) may be, for example, a distance in the radial direction of the impedance trajectory between the electrical impedance and the impedance trajectory, or may be a distance in the horizontal axis direction or the vertical axis direction. For example, in the case of the radial direction, the distance e0(f) between the measured electrical impedance Z(f) and the impedance trajectory can be expressed as the following equation (1) using the distance d(f) between the electrical impedance Z(f) and the center of the impedance trajectory, and the radius r.

[0085] e0(f)=d(f)-r …(1) The abnormality determination unit 160 calculates the sum of squares Σe0(f) of the calculated distance e0(f) 2 as the abnormality index.

[0086] Further, as shown in the following equation (2), in consideration of the size of the subject's body E, the sum of squares Σe1(f) of e0(f) / r obtained by dividing e0(f) by r 2 can also be calculated as the abnormality index.

[0087] Σe1(f) 2 =Σ{e0(f) / r} 2 …(2) The radius r of the impedance trajectory varies greatly depending on the subject's body type, i.e., the size (length and cross-sectional area) of body E. Therefore, the magnitude of e0(f) will vary greatly depending on the subject's height, etc. By dividing the distance e0(f) by the radius r, the dependence of the abnormality index on the size of the subject's body E can be suppressed. In other words, by using the above formula (1), the abnormality index can be accurately calculated in both cases where the subject is tall and where they are short.

[0088] Furthermore, as shown in formula (3) below, instead of dividing e0(f) by the radius r, we divide e0(f) by the subject's height h and sum the squares of e0(f) / h Σe2(f) 2 This can also be calculated as an indicator of abnormality.

[0089] Σe2(f) 2 =Σ{e0(f) / h} 2 …(3) Thus, the abnormality determination unit 160 determines, for example, Σe0(f) 2 Σe1(f) 2 , or Σe2(f) 2 This is calculated as an indicator of abnormality.

[0090] Next, the measurement condition determination unit 180 determines whether the calculated V-POWER, I-POWER, and abnormality index are appropriate (step S220). Based on V-POWER, I-POWER, and the abnormality index, the measurement condition determination unit 180 determines whether the measurement conditions are appropriate. If the numerical values ​​of V-POWER and I-POWER based on the measured voltage Vp and current Ib, and the abnormality index based on the impedance trajectory are within an appropriate range (step S220: YES), the measurement condition determination unit 180 determines the measurement conditions for this measurement (step S221) and terminates the process (return). For example, the measurement condition determination unit 180 determines that the measurement conditions are appropriate if V-POWER and I-POWER are each in the range of 20 to 40, and the abnormality index is less than or equal to a specified value (e.g., 0.004). On the other hand, the measurement condition determination unit 180 determines that the measurement conditions are inappropriate if at least one of V-POWER and I-POWER is outside the range of 20 to 40, and / or if the abnormality index exceeds a specified value.

[0091] On the other hand, if the measurement conditions are not appropriate (step S220: NO), the measurement condition determination unit 180 changes the measurement conditions (step S222). The control unit 10 changes at least one of the measurement conditions and returns to the process of step S201. As a change to the measurement conditions, the control unit 10 sets the gain Gd and / or gain Gi to a value lowered by one step. Also, regarding the frequency band, for example, it increases or decreases the maximum frequency (upper limit on the high-frequency side).

[0092] The measurement condition determination unit 180 may set the gain Gd as the measurement condition for this measurement such that the abnormality index is less than or equal to a specified value (e.g., 0.004) and V-POWER is maximized within a range where it does not exceed an upper limit value (e.g., 40).

[0093] Furthermore, the measurement condition determination unit 180 may set the frequency band in which the abnormality index is less than or equal to a specified value (e.g., 0.004) and the abnormality index is smallest as the measurement condition for the main measurement, or it may set the frequency band in which V-POWER is largest while not exceeding the upper limit value (e.g., 40) as the measurement condition for the main measurement.

[0094] [This measurement process] Figure 7A is a subroutine flowchart illustrating the details of the measurement process (S103) in the flowchart of Figure 5, and Figure 7B is a subroutine flowchart that follows Figure 7A. The processing of the subroutine flowcharts shown in Figures 7A and 7B is realized by the CPU 11 executing a control program.

[0095] First, the control unit 10 sets the measurement conditions determined by the preliminary measurement (step S301). The mode control unit 190 then starts the measurement of the subject's body composition from the second measurement mode.

[0096] Next, in steps S302 to S318, the electrical impedance measurement unit 50 performs electrical impedance measurement of the subject's body and calculates the impedance trajectory. These processes are the same as the electrical impedance measurement process of the subject's body and calculation of the impedance trajectory in the preliminary measurement process (steps S202 to S218), so a detailed explanation is omitted. In this measurement, the control unit 10 performs synchronous addition of the synchronous sum data up to one cycle before the M-sequence signal and the A / D conversion data for each of the voltage signals Vp and Vb (steps S312, S311). In this case, the number of repetitions of synchronous addition (averaging count; total 128 times × N times) is performed at the number set in the second measurement mode (for example, if N=40, a total of 128 times × 40 times). Generally, the number of averaging counts in this measurement is set to be higher than the number of averaging counts in the preliminary measurement. Subsequently, the control unit 10 uses the impedance trajectory to calculate the resistance R∞ when the probe current frequency is infinite and the resistance R0 when the probe current frequency is 0 (step S319). The control unit 10 also uses the impedance trajectory to calculate an anomaly index in the same manner as in step S215 of the preliminary measurement (step S320).

[0097] Next, the abnormality determination unit 160 determines whether the calculated abnormality index is below a specified value (step S321). If the abnormality index is below a specified value (step S321: YES), the control unit 10 determines whether there is an abnormality in the electrical impedance measurement (step S322). Details of the determination method for determining whether there is an abnormality in the electrical impedance measurement will be described later. If there is no abnormality in the electrical impedance measurement (step S322: YES), the body composition measurement unit 150 calculates and displays the subject's body composition based on R0, R∞, and information about the subject (especially gender, age, height, and weight) (step S323). At this time, the body composition measurement unit 150 transmits the measurement result to the display unit 65, and the display unit 65 displays the measurement result on the display. Furthermore, the body composition measurement unit 150 displays, along with the body composition results, the electrical impedance information calculated in step S317, the impedance trajectory calculated in step S318, R0 and R∞ calculated in step S319, and the abnormality index calculated in step S320. In addition, the recording unit 62 saves these measurement results.

[0098] On the other hand, if the control unit 10 detects an abnormality in the electrical impedance measurement (step S322: NO), it stops the measurement of body composition, notifies the abnormality (step S324), and terminates the process (return). For example, the control unit 10 sends a warning message to the display unit 65 indicating that there is an abnormality in the electrical impedance measurement, and the display unit 65 displays the warning message on the display. Therefore, it is possible to prevent operators such as medical professionals from misidentifying the body composition of the subject's body E.

[0099] On the other hand, if the abnormality index exceeds a specified value (step S321: NO), the control unit 10 increases the total number of averaging cycles in steps S311 and S312 (number of repetitions in synchronous addition) (step S325). For example, the control unit 10 increases the total number of averaging cycles from 128 × N to 128 × (N + Δn). Alternatively, the mode control unit 190 switches the measurement mode from the second measurement mode to the first measurement mode. As a result, if the increment Δn is 10, the total number of averaging cycles increases from 128 × N to 128 × (N + 10). Furthermore, if the abnormality index exceeds a specified value in the first measurement mode, the mode control unit 190 switches the measurement mode from the first measurement mode to the third measurement mode. As a result, the total number of averaging cycles increases further to 128 × (N + 10 + 10). If the anomaly index exceeds a specified value, instead of increasing the total number of averaging cycles, or in addition to increasing the total number of averaging cycles, the system may notify the user that there is an anomaly in the measurement by displaying it on the display unit or by making an audible or voice notification.

[0100] Next, the control unit 10 determines whether the total number of averaging cycles is equal to or greater than the maximum number (step S326). The maximum total number of averaging cycles may be, for example, 128 × 80 or 128 × 120. If the total number of averaging cycles is equal to or greater than the maximum number (step S326: YES), the control unit 10 stops the body composition measurement, notifies the system of the abnormality (step S327), and terminates the process (return). The control unit 10 determines that the accuracy of the measurement data is insufficient and stops the body composition measurement. The control unit 10 also notifies the operator that measurement data with sufficient accuracy cannot be obtained. Alternatively, the control unit 10 may control the system to display the measurement results as reference values ​​on the display unit 65 without stopping the body composition measurement.

[0101] On the other hand, if the total number of averaging cycles is less than the maximum number (step S326: NO), the control unit 10 proceeds to the electrical impedance measurement process again (steps S302 to S325). In this way, the control unit 10 performs electrical impedance measurements by gradually increasing the total number of averaging cycles within a range where the total number of averaging cycles does not exceed the maximum number, thereby keeping the variation in impedance measurement values ​​within a specified range while minimizing the number of averaging cycles.

[0102] [Process to determine whether there is an abnormality in the electrical impedance measurement (Step S322)] Figure 8 is a subroutine flowchart illustrating the process for determining whether or not there is an abnormality in the electrical impedance measurement. The process shown in the subroutine flowchart is implemented by the CPU 11 executing a control program.

[0103] In step S401, the critical frequency fc is used as an indicator to determine whether or not there was an abnormality in the electrical impedance measurement by evaluating the bias in the distribution of impedance measurements at each frequency relative to the impedance trajectory. In step S402, R∞ / R0 is used as an indicator to determine whether or not there was an abnormality in the electrical impedance measurement based on whether or not the magnitude of the impedance trajectory is within the normal range. Note that steps S401 and S402 may be performed in any order. The following will provide an example of the case where steps S401 and S402 are performed in that order.

[0104] The determination unit 130 determines whether or not there is an abnormality in the critical frequency fc (step S401). In this step, the determination of whether or not there is an abnormality in the critical frequency fc is made by using the critical frequency fc as an indicator and evaluating the bias in the distribution of impedance measurements at each frequency relative to the impedance trajectory.

[0105] The determination unit 130 determines whether the critical frequency fc calculated by the impedance trajectory calculation unit 110 is within a predetermined range. If the critical frequency fc is within the predetermined range, the determination unit 130 determines that there is no abnormality in the critical frequency fc (step S401: YES) and proceeds to step S402. On the other hand, if the critical frequency fc is outside the predetermined range, the determination unit 130 determines that there is an abnormality in the critical frequency fc (step S401: NO). Therefore, the determination unit 130 determines that there is an abnormality in the electrical impedance measurement (step S404) and terminates the process (return).

[0106] Normally, for healthy individuals, the critical frequency fc is around 50 kHz. However, there are individual differences in the critical frequency fc. For this reason, it is preferable that the lower limit of the critical frequency fc be around 5 to 20 kHz and the upper limit be around 90 to 150 kHz. In other words, in step S401, it is preferable that the allowable range of the critical frequency fc be around 5 to 150 kHz, and further, a range of around 10 to 100 kHz be defined.

[0107] If the determination unit 130 determines that there is no abnormality in the critical frequency fc (step S401: YES), it determines whether there is an abnormality in R∞ / R0 (step S402). In this step, R∞ / R0 is used as an indicator, and it is determined whether there is an abnormality in the electrical impedance measurement based on whether the magnitude of the impedance trajectory is within the normal range. The determination unit 130 determines whether R∞ / R0 is within a predetermined range. If R∞ / R0 is within a predetermined range, the determination unit 130 determines that there was no abnormality in the value R∞ / R0 (step S402: YES), proceeds to step S403, and determines that there is no abnormality in the electrical impedance measurement.

[0108] On the other hand, the determination unit 130 determines that there is an abnormality in R∞ / R0 if the value R∞ / R0 is outside a predetermined range (step S402: NO). Therefore, the determination unit 130 determines that there is an abnormality in the electrical impedance measurement (step S404) and terminates the process (return).

[0109] Normally, in healthy individuals, the R∞ / R0 value is around 0.6 to 0.8 (60% to 80%). Therefore, in step S402, the acceptable range for R∞ / R0 can be set to approximately 0.85 to 0.9 or less (0% to 90%).

[0110] In this embodiment, only an example of judging only the value of R∞ / R0 in step S402 has been described. However, the system may be configured to judge whether the values ​​of R∞ and R0, along with R∞ / R0, are within an appropriate range. In other words, the system may be configured to judge that there was an abnormality in the measurement of electrical impedance if R∞ or R0 becomes abnormally large or abnormally small. For example, the judgment indicator may be that R∞ and R0 are both > 0Ω. Alternatively, the judgment indicator may be that R∞ and R0 are both within the range of 100 to 1000Ω.

[0111] In this embodiment, the measurement conditions are optimized throughout the preliminary and main measurements. Specifically, the gain Gd is optimized to be maximized when the anomaly index calculated from the impedance trajectory is below a specified value (e.g., 0.004) and I-POWER and V-POWER are within the specified range. Furthermore, the number of averaging cycles for synchronous summation of voltage signals and current-derived voltage signals is optimized.

[0112] In this embodiment, and in Figures 6 and 7A, the measurement conditions are determined using I-POWER, V-POWER, and an anomaly index in the preliminary measurement, and the measurement results are displayed or anomalies are notified in the main measurement based on the anomaly index and the determination of whether or not there are anomalies in the electrical impedance measurement. However, the system is not limited to this configuration. That is, in the preliminary measurement, in addition to I-POWER, V-POWER, and the anomaly index, the measurement conditions may also be determined by adding the determination of whether or not there are anomalies in the electrical impedance measurement, similar to the main measurement. Furthermore, in the main measurement, I-POWER and V-POWER may be added as judgment indicators, or the determination may be made using one or more combinations of I-POWER, V-POWER, the anomaly index, and the determination of whether or not there are anomalies in the electrical impedance measurement. Moreover, in the determination of whether or not there are anomalies in the electrical impedance measurement, the determination may also be made using one or more combinations of the critical frequency fc, R∞ / R0, and the respective values ​​of R∞ and R0.

[0113] [Measurement principle using electrical impedance method] Figure 9 is a schematic diagram illustrating the flow of electric current (current signal) in cells within a living organism according to frequency, and Figure 10 is a schematic electrical equivalent circuit diagram of the living organism shown in Figure 9.

[0114] Bioelectrical impedance analysis is a method for measuring (estimating) a subject's body composition, such as body water distribution, body fat percentage, and body fat mass, from bioelectrical impedance. Bioelectrical impedance consists of the body's resistance to electric currents transported by ions in the body and reactance associated with various types of polarization processes created by cell membranes, tissue interfaces, or non-ionized tissues.

[0115] Capacitance, the reciprocal of reactance, primarily causes a time delay in current, creating a phase shift. This phase shift can be geometrically quantified as the electrical phase angle, which is the arctangent angle of the ratio of reactance to resistance. The magnitude of bioelectrical impedance Z is given by Z, where R is the resistance and X is the reactance. 2 =R 2 +X 2 Defined by:

[0116] Bioelectrical impedance Z, resistance R, reactance X, and electrical phase angle Φ are frequency-dependent. As shown in Figure 9, when the current frequency is very low, the bioelectrical impedance Z at the cell membrane-tissue interface becomes very high. Therefore, the current does not flow through the cell membrane or tissue interface, but only through the extracellular fluid. Consequently, the measured bioelectrical impedance Z is substantially equal to the resistance R.

[0117] As the frequency of the current increases, the current (low-frequency component) begins to flow through the cell membrane and tissue interface. This increases the reactance X and widens the phase angle Φ. However, when the current frequency exceeds the critical frequency fc, the capacitive properties of the cell membrane and tissue interface are lost. Therefore, as the frequency of the current (high-frequency component) increases further beyond the critical frequency fc, the reactance X decreases. When the current frequency becomes very high, the bioelectrical impedance Z becomes virtually equal to the resistance R again. The "critical frequency" refers to the frequency at which the reactance is maximum.

[0118] As shown in Figure 10, the equivalent circuit of the human body consists of a circuit in which the cell membrane capacitance Cmk and intracellular fluid resistance Rik are connected in series, and a parallel circuit with extracellular fluid resistance Re.

[0119] When the current frequency is low, the current flows primarily through the extracellular space. Therefore, the impedance Z is substantially equal to the extracellular fluid resistance Re. On the other hand, when the current frequency is high, the current flows substantially through the cell membrane. Therefore, the cell membrane capacitance Cm is considered substantially short-circuited. Thus, when the current frequency is high, the impedance Z is substantially equal to the combined resistance Ri·Re / (Ri+Re), where Cm and Ri represent the combined capacitance and combined resistance of Cmk and Rik as a whole tissue.

[0120] Therefore, the extracellular fluid resistance Re can be determined by applying a low-frequency current and measuring the electrical impedance of the subject's body. Furthermore, the intracellular fluid resistance Ri can be determined from the determined extracellular fluid resistance Re and the electrical impedance of the subject's body when a high-frequency current is applied, based on the formula Z = Ri·Re / (Ri+Re). Then, the subject's body composition can be estimated based on the obtained intracellular fluid resistance Ri and extracellular fluid resistance Re. Note that the method for measuring the subject's body composition is not particularly limited, and conventionally known methods can be used.

[0121] In this specification, "body composition" refers to all data related to the composition of body E. For example, "body composition" includes the amount of body composition, the proportion of a particular composition to body E, and the distribution of a particular composition to body E. "Composition" refers to what makes up body E, and specific examples of composition include body water volume, intracellular fluid volume, extracellular fluid volume, protein, fat, and calcium. Specific examples of body composition include body fat percentage, body fat weight contained in the subject's body E, lean body mass (muscle mass), phase angle (muscle mass), body water distribution, bone density, skeletal muscle mass, lean body mass index, skeletal muscle mass index, and edema rate. Specific examples of body water distribution include intracellular fluid volume, extracellular fluid volume, and body water volume. Body water volume is the sum of intracellular fluid volume and extracellular fluid volume.

[0122] <Effects and Effects in the First Embodiment> The body composition measuring device 1 of the first embodiment described above provides the following effects.

[0123] The body composition analyzer 1 determines appropriate measurement conditions for the subject in a preliminary measurement, and then measures the subject's body composition in the main measurement according to the determined measurement conditions. Therefore, it is possible to suppress variations in the measurement results of the subject's body composition due to factors such as the subject's physique, body movement, and whether or not the arms and armpits are in contact. Furthermore, since the body composition analyzer 1 is configured to minimize the measurement time, it is possible to reduce the possibility of the subject moving or the arms and armpits coming into contact during measurement.

[0124] The body composition measurement device 1 performs electrical impedance measurement by gradually increasing the number of averaging cycles (number of synchronous addition repetitions) within a range where the number of averaging cycles does not exceed the maximum number. This allows the variation in impedance measurement values ​​to be kept within a specified range while minimizing the number of synchronous addition repetitions. Therefore, it is possible to prevent or suppress the time required for averaging current (converted to a voltage signal for use during impedance measurement) and voltage signals from taking more time than necessary for measurement accuracy. As a result, the measurement time of the body composition measurement device 1 can be minimized. Consequently, if the body composition measurement device 1 is a portable device powered by a battery, battery power consumption can be reduced.

[0125] (Second embodiment) In the second embodiment, in addition to conducting preliminary measurements prior to the main measurement, we will describe a case where the measurement conditions are changed if the voltage and current measured in the main measurement are not appropriate. To avoid repetition of explanation, detailed explanations of the same configuration as in the first embodiment will be omitted.

[0126] Figure 11A is a subroutine flowchart illustrating the details of the measurement process (S103) in the second embodiment, and Figure 11B is a subroutine flowchart following Figure 11A. The processing of the subroutine flowcharts shown in Figures 11A and 11B is realized by the CPU 11 executing a control program.

[0127] The processes in steps S501 to S524 are the same as the processes in steps S301 to S321 and S325 to S327 in Figures 7A and 7B of the first embodiment, respectively, so a detailed explanation is omitted. Also, the processes in steps S529 to S531 are the same as the processes in steps S322 to S324 in Figure 7B, respectively, so a detailed explanation is omitted.

[0128] In this embodiment, in step S525, the magnitude of the voltage signal Vp and the voltage signal Vb corresponding to the current Ib are calculated. Step S525 is the same as the processing in steps S213 and S214 in Figure 6 of the first embodiment, so a detailed explanation is omitted.

[0129] In step S526, the measurement condition determination unit 180 determines whether the measured voltage and current are appropriate. Based on V-POWER, I-POWER, and the anomaly index, the measurement condition determination unit 180 determines whether the measured voltage Vp and current Ib are appropriate. If the measured voltage Vp and current Ib are appropriate (step S526: YES), the measurement condition determination unit 180 maintains the measurement conditions for this measurement (step S527) and proceeds to the process in step S529. For example, the measurement condition determination unit 180 determines that the measured voltage Vp and current Ib are appropriate if V-POWER and I-POWER are each in the range of 20 to 40 and the anomaly index is below a specified value. The specified value for the anomaly index may be, for example, 0.004.

[0130] On the other hand, if the measured voltage Vp and current Ib are not appropriate (step S526: NO), the measurement condition determination unit 180 changes the measurement conditions (step S528). The control unit 10 changes at least one of the measurement conditions and returns to the process in step S502. As a change to the measurement conditions, the control unit 10 sets, for example, the gain Gd and / or gain Gi to a value lowered by one step.

[0131] In the example above, we described a case where preliminary measurements are performed, but the system is not limited to such cases. It may also be configured to change the measurement conditions if the voltage and current measured in the main measurement are not appropriate, even without performing preliminary measurements.

[0132] <Effects and Effects in the Second Embodiment> The body composition measuring device 1 of the second embodiment described above provides the following effects in addition to the effects of the first embodiment.

[0133] The body composition measurement device 1 changes the measurement conditions depending on whether the voltage Vp and current Ib measured in this measurement are appropriate, thereby suppressing variations in the measurement results of the subject's body composition due to factors such as the subject's physique, body movement, whether or not the arms and armpits are in contact, and whether or not the thighs of both legs are in contact.

[0134] (Third embodiment) In the third embodiment, during the measurement, the control unit 10 performs the measurement operation multiple times, and the control unit 10 also functions as a measurement result exclusion unit. In each of the multiple measurements, the control unit 10 excludes inappropriate resistance R∞ when the probe current frequency is ∞ and resistance R0 when the probe current frequency is 0 (hereinafter also referred to as "outliers"). The reason for excluding inappropriate measurement results is as follows: For example, in a swollen subject, the entire body has low resistance, making it difficult to determine the optimal measurement conditions, and the results are prone to fluctuations due to body movement, etc. Therefore, it is useful to perform body composition measurements multiple times, exclude inappropriate measurement results, and average the remaining appropriate measurement results. Note that, in order to avoid repetition of explanation, detailed explanations of the same configuration as in the first embodiment will be omitted.

[0135] Figure 12 is a subroutine flowchart illustrating the details of the measurement process (S103) in the third embodiment. The processing of the subroutine flowchart shown in Figure 12 is realized by the CPU 11 executing a control program.

[0136] The control unit 10 can remove outliers using, for example, one of the following methods (a) to (c).

[0137] <(a) Methods for removing outliers using V-POWER, I-POWER, and anomaly indicators> First, in step S601, the control unit 10 sets the measurement conditions set by the preliminary measurement. Next, in step S602, the main measurement is performed. The main measurement is repeated a predetermined number of times (L times). There is no limit to the number of times, but it may be set to, for example, 3 to 5 times. Each of the main measurements performed multiple times is the same as the processing in steps S301 to S324 in Figures 7A and 7B of the first embodiment, so a detailed explanation is omitted. Note that steps S603 and S604 in Figure 12 are the same as steps S313 and S314 in Figure 7A. Steps S605 and S608 in Figure 12 are the same as steps S318 and S320 in Figure 7B. Furthermore, in steps S606 and S607 in Figure 12, the resistance R∞ when the probe current frequency is infinite and the resistance R0 when the probe current frequency is 0 are calculated. These can also be obtained from the calculated impedance trajectory in the same way as in step S319 in Figure 7B.

[0138] Next, in step S609, the measurement result exclusion unit excludes R∞ and R0 obtained from measurements that are determined to be inappropriate from among the L measurements taken. Then, in step S610, the average values ​​of R∞ and R0 are calculated using the remaining R∞ and R0. Then, the body composition is calculated using the average values ​​of R∞ and R0. The measurement result exclusion unit excludes inappropriate measurements from among the multiple measurements taken based on at least one of V-POWER, I-POWER, and the abnormality index. For example, the measurement result exclusion unit excludes R∞ and R0 obtained from measurements in which the abnormality index exceeds a specified value (e.g., 0.004) from the L measurement results stored in RAM13 as outliers.

[0139] Next, in step S611, the control unit 10 displays the body composition measurement results obtained in step S610, the presence or absence of outliers, and the variation errors of R0 and R∞. The presence or absence of outliers may be indicated by the number of measurements that did not contain outliers relative to the set number of loops for the measurement. That is, if two measurements determined to be outliers are included in a measurement set to L=5, it may be displayed as 3 / 5. In addition, the variation errors of R0 and R∞ may be calculated using the variation errors of R∞ and R0 used in the body composition measurement. (b) Method for removing outliers using the mean μ and standard deviation σ of the measurement results. The control unit 10 calculates the mean μ and standard deviation σ for each of the measurement results of R0 and R∞ obtained for the number of measurements.

[0140] (b-1) The control unit 10 excludes the Kth measurement result from the multiple measurement results of R0 and R∞, and calculates the mean μ and standard deviation σ from the remaining measurement results.

[0141] (b-2) The control unit 10 compares the Kth measurement result for R0 and R∞ with the average value μ calculated in (b-1) above, and determines that the measurement data is an outlier if it is more than three times the value of the standard deviation σ (i.e., 3σ) away from the average value μ.

[0142] (b-3) The control unit 10 performs the processes described in (b-1) and (b-2) above in order for K=1 to the number of measurements. (c) Remove outliers using the quartiles of the measurement results (c-1) The control unit 10 arranges the measurement results of R0 and R∞ in descending order and determines the measurement results that make up one-quarter of the total (upper quartile) and three-quarters of the total (lower quartile).

[0143] (c-2) Add 1.5 times the difference between these two quartiles to the upper quartile, and any measurement greater than this is considered an outlier.

[0144] (c-3) Similarly, subtract 1.5 times the difference from the lower quartile, and any measurement smaller than that is considered an outlier.

[0145] Thus, in this embodiment, the measurement is performed multiple times consecutively during a single measurement of the subject's body composition. The body composition measurement unit 150 then uses one or more remaining measurement results related to body composition, after the measurement result exclusion unit has excluded any inappropriate calculation results, to calculate the final measurement result of the subject's body composition.

[0146] The above describes a case in which the control unit 10 removes outliers using any of the methods (a) to (c) described above, but it is not limited to this case. The control unit 10 may be configured to remove outliers using a combination of several of the methods (a) to (c) described above. In addition, the control unit 10 may be configured to remove outliers using methods other than those (a) to (c) described above.

[0147] Furthermore, while the above describes the case where calculations are performed to determine whether R0 and R∞ are outliers, it is also possible to calculate multiple body composition results for the number of repeated measurements (L times), remove outlier body composition results using the mean μ and standard deviation σ, and then use the remaining body composition results to calculate the final measurement result of the subject's body composition. Similarly, multiple body composition results may be calculated, outliers may be removed using quartiles, and the final measurement result of the subject's body composition may be used. Moreover, these methods may be combined.

[0148] In this way, the control unit 10 can perform this measurement multiple times in a single measurement of the subject's body composition. In this case, the measurement condition determination unit 180 maintains the measurement conditions so that the measurement conditions during one measurement are the same as the measurement conditions during the next measurement.

[0149] <Verification experiment of measurement accuracy> Figure 13 is a conceptual diagram showing the usage of the body composition measurement device 1 in a verification experiment of measurement accuracy using pigs.

[0150] The inventors conducted verification experiments on measurement accuracy using pigs with low overall resistance values ​​as an evaluation system that simulates subjects with extreme edema.

[0151] In the verification experiment, surface electrodes Hp and Hc, and surface electrodes Lp and Lc were attached to the right foreleg and rump of a pig, respectively. The body composition measurement device 1 was connected to the surface electrodes Hp, Hc, Lp, and Lc by cables, and the electrical impedance of the pig was measured. In the measurement with a conventional body composition measurement device that does not have a function to set measurement conditions by preliminary measurement, the gain Gd was 8 times. However, in the body composition measurement device of this embodiment, which has a function to optimize measurement conditions by preliminary measurement, the gain Gd during measurement was 12 times.

[0152] In this verification experiment, the measurement was repeated five times using both the conventional body composition measurement device and the body composition measurement device 1 of this embodiment, and the results were compared. In the body composition measurement device 1 of this embodiment, the measurement was repeated five times using the repeat function. In the conventional body composition measurement device, which does not have a repeat function for this measurement, this was substituted by fixing the measurement conditions and performing the body composition measurement five times consecutively.

[0153] Table 1 below shows a comparison of the mean values, deviations, and error rates of R0, R∞, and abnormality indices for a conventional body composition measurement device and the body composition measurement device 1 of this embodiment. In Table 1, the mean values ​​of R0, R∞, and abnormality indices are the average results of five measurements taken under the same measurement conditions. In addition, the body composition measurement device 1 of this embodiment was evaluated three times under the same conditions.

[0154] [Table 1]

[0155] In this embodiment, the body composition measurement device 1 yielded good results in terms of the error rate of R0, the error rate of R∞, and the average of the abnormality index.

[0156] On the other hand, while conventional body composition measurement devices have low error rates for R0 and R∞, the average abnormality index exceeds 1.0, indicating that the fitting of measurement data on the impedance trajectory is insufficient.

[0157] Thus, the results of the above verification experiment confirmed that the body composition measurement device 1 of this embodiment has higher measurement accuracy than conventional body composition measurement devices.

[0158] <Verification experiment of measurement time> Figure 14A is a graph illustrating the results of confirming V-POWER in the measurement time verification experiment, and Figure 14B is a graph illustrating the results of confirming I-POWER in the measurement time verification experiment. Furthermore, Figure 15A is a graph illustrating the results of confirming the variation error (%) of R0 in the measurement time verification experiment, and Figure 15B is a graph illustrating the results of confirming the variation error (%) of R∞ in the measurement time verification experiment. Furthermore, Figure 15C is a graph illustrating the results of confirming the average value of the anomaly index in the measurement time verification experiment.

[0159] The inventors conducted verification experiments on measurement time using pigs with low overall resistance values ​​as an evaluation system simulating subjects with extreme edema. The mounting positions of the surface electrodes Hp, Hc, Lp, and Lc were the same as in the verification experiment for measurement accuracy (Figure 13).

[0160] The measurement time in normal mode (total number of averaging cycles, i.e., number of synchronous addition repetitions, 128 times × 40 times) was 59.71 ± 0.08 seconds. On the other hand, the measurement time in 2 / 3 mode (total number of averaging cycles, approximately 2 / 3 of normal mode, totaling 128 times × 27 times (67% when the number of averaging cycles in normal mode is set to 100%)) was 39.00 ± 0.07 seconds (65.3%). Similarly, the measurement time in 1 / 2 mode (total number of averaging cycles, 1 / 2 of normal mode, totaling 128 times × 20 times (50% when the number of averaging cycles in normal mode is set to 100%) was 28.67 ± 0.05 seconds (48.0%).

[0161] Furthermore, verification experiments of the measurement time confirmed that there were no abnormalities in the measured voltage signal Vp. Specifically, as shown in Figure 14A, five measurements were taken for each of the normal mode, 2 / 3 mode (2 / 3 hours), and 1 / 2 mode (1 / 2 hours), and the V-POWER was measured, all of which fell within the range of 30 to 40. In the case of the 1 / 2 mode (1 / 2 hours), where there were concerns about adverse effects on accuracy due to the reduced number of averaging cycles, the same evaluation was performed again (Figure 14A, 1 / 2 hour circle 2), but the same result as the first time (Figure 14A, 1 / 2 hour circle 1) was obtained. From these results, it became clear that there were no problems with V-POWER in both the 2 / 3 mode (2 / 3 hours) and the 1 / 2 mode (1 / 2 hours).

[0162] Furthermore, verification experiments of the measurement time confirmed that there were no abnormalities in the measured current signal Ib. As shown in Figure 14B, five measurements were taken for each of the normal mode, 2 / 3 mode (2 / 3 hours), and 1 / 2 mode (1 / 2 hours), and the I-POWER was measured, all of which fell within the range of 30 to 40. For the 1 / 2 mode (1 / 2 hours), where there were concerns about adverse effects on accuracy, the same evaluation was performed again (Figure 14B, 1 / 2 hour circle 2), and the same result as the first time (Figure 14B, 1 / 2 hour circle 1) was obtained. From these results, it became clear that there were no problems with I-POWER in both the 2 / 3 mode (2 / 3 hours) and the 1 / 2 mode (1 / 2 hours).

[0163] Furthermore, in the verification experiment of the measurement time, the variation error (%) of R0 was checked, and it was confirmed that there was no abnormality in the calculated variation error of R0. Specifically, as shown in Figure 15A, five measurements were taken twice for each of the following modes: normal mode (indicated as "None" in Figure 15A), 2 / 3 mode (indicated as "2 / 3 times" in Figure 15A), and 1 / 2 mode (indicated as "1 / 2 times" in Figure 15A). The variation error (error rate) of R0 was calculated, and in all cases it was below the standard value of 2%. From these results, it became clear that the measurement accuracy of R0 is not a problem in both the 2 / 3 mode (2 / 3 hours) and the 1 / 2 mode (1 / 2 hours).

[0164] Furthermore, in verification experiments of the measurement time, the variation error (%) of R∞ was checked, and it was confirmed that there was no abnormality in the calculated variation error of R∞. Specifically, as shown in Figure 15B, five measurements were taken twice for each of the following modes: normal mode (indicated as "None" in Figure 15B), 2 / 3 mode (indicated as "2 / 3 times" in Figure 15B), and 1 / 2 mode (indicated as "1 / 2 times" in Figure 15B). The variation error (error rate) of R∞ was calculated, and in all cases it was below the 2% set as the standard value. From these results, it became clear that the measurement accuracy of R∞ is not a problem in both the 2 / 3 mode (2 / 3 hours) and the 1 / 2 mode (1 / 2 hours).

[0165] Furthermore, verification experiments of the measurement time confirmed that the average value of the anomaly index was normal. Specifically, as shown in Figure 15C, five measurements were taken twice for each of the following modes: normal mode (indicated as "None" in Figure 15C), 2 / 3 mode (indicated as "2 / 3 times" in Figure 15C), and 1 / 2 mode (indicated as "1 / 2 times" in Figure 15C). The average value of the anomaly index was calculated, and in all cases it was below the baseline value of 0.004. From these results, it became clear that the accuracy of impedance trajectory calculation was not a problem in both the 2 / 3 mode (2 / 3 hours) and the 1 / 2 mode (1 / 2 hours).

[0166] Thus, the results of the above verification experiments confirmed that the body composition measurement device 1 of this embodiment can significantly reduce the measurement time while maintaining the same level of measurement accuracy as conventional body composition measurement devices.

[0167] <Effects and Effects in the Third Embodiment> The body composition measuring device 1 of the third embodiment described above provides the following effects in addition to the effects of the first and second embodiments.

[0168] The body composition measurement device 1 calculates the final measurement result by excluding outliers from the measurement results, thereby improving the accuracy of the measurement of the subject's body composition.

[0169] As described above, the body composition measuring device, control method, and control program of the present invention have been explained in the embodiments. However, it goes without saying that the present invention can be appropriately added to, modified, and omitted by those skilled in the art within the scope of its technical concept.

[0170] For example, the system may be configured to calculate electrical admittance and admittance trajectory instead of, or in addition to, electrical impedance and impedance trajectory. Furthermore, the mounting locations of the surface electrodes are not limited to the hands or feet.

[0171] Furthermore, the control program may be provided on a computer-readable recording medium such as a USB memory stick, flexible disk, or CD-ROM, or it may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in memory or storage. This control program may also be provided, for example, as standalone application software, or it may be incorporated into the software of each device as a function of the server.

[0172] Furthermore, in the embodiment, some or all of the processing performed by the control program may be replaced and executed by hardware such as circuits.

[0173] Furthermore, regarding the number of repetitions of synchronous addition, while it has been explained that in normal mode, the synchronous addition process of the M-sequence signal data from the previous cycle and the M-sequence signal for the next cycle is performed a total of 128 times × 40 times, this is not limited to this. The 128 processes performed to cancel the pseudo-noise caused by the square wave can also be freely set. In addition, the number of processes performed to cancel the pseudo-noise caused by the square wave may be set in accordance with the M-sequence generator or square wave generator of the signal output unit. In this embodiment, it may be set to 32 times × 40 times, or to a number that is a multiple of 32, such as (32 times × A times) × 40 times. Furthermore, the number of repetitions of the synchronous addition process performed to cancel the pseudo-noise caused by the square wave may be increased or decreased between measurement modes. [Explanation of Symbols]

[0174] 1. Body composition measuring device, 10 Control unit, 20 current measurement section, 21 A / D converters, 22 BPF, 23 I / V converter, 24 Current detection unit, 30 Signal output section, 31 Measurement signal generator, 32 output buffers, 40 Voltage measurement section, 41 A / D converter, 42 BPF, 43 Differential amplifier, 44 Voltage detection unit, 50 Electrical impedance measurement section, 62 Records Section, 63 Input section, 64 speakers, 65 Display section, 66 memory, 110 Impedance trajectory calculation unit, 120 Electrical impedance calculation unit, 130 Judgment Department, 140 Hochi Department, 150 Body composition measurement unit, 160 Abnormality determination unit, 170 Voltage and current calculation unit, 180 Measurement condition determination unit, 190 Mode control unit.

Claims

1. A body composition analyzer that measures the body composition of a subject according to measurement conditions, A current input unit that applies multiple probe currents of different frequencies to the subject's body, A voltage detection unit detects a voltage signal relating to the voltage generated between predetermined parts of the subject's body when the plurality of probe currents are applied to the subject's body by the current application unit, A current detection unit detects a current signal relating to the current flowing through the subject when the plurality of probe currents are applied to the subject's body by the current application unit, A voltage signal amplification unit amplifies the voltage signal detected by the voltage detection unit to a magnitude suitable for electrical impedance measurement. A current-voltage conversion unit converts the current signal detected by the current detection unit into a voltage of a magnitude used for measuring electrical impedance, An electrical impedance calculation unit calculates information regarding electrical impedance for each frequency based on the voltage signal amplified by the voltage signal amplification unit and the current signal converted by the current voltage conversion unit. An impedance trajectory calculation unit calculates an impedance trajectory based on the information regarding the electrical impedance for each frequency calculated by the electrical impedance calculation unit, A body composition information calculation unit calculates information about the subject's body composition based on the impedance trajectory calculated by the impedance trajectory calculation unit, An abnormality index calculation unit calculates an abnormality index, which is an indicator of the abnormality of the impedance trajectory calculated by the impedance trajectory calculation unit, An effective value calculation unit that calculates a value relating to the magnitude of the voltage signal amplified by the voltage signal amplification unit and / or a value relating to the magnitude of the current signal converted by the current-voltage conversion unit, The body composition measuring device comprises a measurement condition determination unit that determines the changeable measurement conditions of the body composition measuring device based on at least one of the value relating to the magnitude of the voltage signal calculated by the RMS value calculation unit and the value relating to the magnitude of the current signal calculated by the RMS value calculation unit, and an abnormality index calculated by the abnormality index calculation unit. Prior to the main measurement to measure the body composition of the subject, a preliminary measurement is performed to determine the measurement conditions. The measurement condition determination unit determines the frequency bands of the multiple probe currents applied to the subject's body as measurement conditions for the measurement in the measurement, Body composition measuring device, wherein the measurement condition determination unit, if the abnormality index calculated by the abnormality index calculation unit in the preliminary measurement exceeds a specified value, changes the measurement conditions by increasing or decreasing the upper limit on the high-frequency side in the frequency band of the plurality of probe currents and performs the preliminary measurement again, and if the abnormality index calculated in the preliminary measurement performed again is less than or equal to the specified value, determines the frequency band in the preliminary measurement performed again as the measurement condition for the main measurement.

2. The body composition measuring device according to claim 1, wherein the measurement condition determination unit determines the measurement conditions for the main measurement based on at least one of the value relating to the magnitude of the voltage signal calculated by the RMS value calculation unit and the value relating to the magnitude of the current signal calculated by the RMS value calculation unit, and an abnormality index calculated by the abnormality index calculation unit, in the preliminary measurement.

3. The body composition measuring device according to claim 2, wherein the measurement condition determination unit determines the measurement conditions for subsequent measurements based on at least one of the value relating to the magnitude of the voltage signal calculated by the RMS value calculation unit and the value relating to the magnitude of the current signal calculated by the RMS value calculation unit, and the abnormality index calculated by the abnormality index calculation unit.

4. The body composition measuring apparatus according to claim 2 or 3, wherein the measurement condition determination unit determines the gain of the voltage signal amplification unit as the measurement condition in the measurement.

5. The body composition measuring device according to claim 4, wherein the measurement condition determination unit determines the gain of the voltage signal amplification unit during the measurement such that the abnormality index is less than or equal to a specified value and the value relating to the magnitude of the voltage signal calculated by the effective value calculation unit is maximized within a range that does not exceed an upper limit.

6. The body composition measuring device according to claim 1, wherein the measurement condition determination unit determines the number of points in the impedance trajectory according to the determined frequency band.

7. A body composition measuring device according to any one of claims 1 to 3, wherein the main measurement is performed multiple times in succession during a single measurement of the subject's body composition, the measurement condition determination unit maintains the measurement conditions such that the measurement conditions during the main measurement in one measurement are the same as the measurement conditions during the next main measurement, and the body composition information calculation unit calculates the result of the subject's body composition using the obtained information on multiple body compositions.

8. The body composition measuring device according to any one of claims 1 to 3, wherein the measurement condition determination unit determines the changeable measurement conditions of the body composition measuring device based on at least the abnormality index calculated by the abnormality index calculation unit, and the abnormality index calculation unit calculates the abnormality index based on the distance between the impedance trajectory calculated by the impedance trajectory calculation unit and the electrical impedance for each frequency calculated by the electrical impedance calculation unit.

9. A body composition measuring device according to claim 1, comprising: a measurement result exclusion unit that excludes inappropriate information from the information on the subject's body composition calculated by the body composition information calculation unit, based on at least one of: a value relating to the magnitude of the voltage signal amplified by the voltage signal amplification unit calculated by the RMS value calculation unit; a value relating to the magnitude of the current signal converted by the current-voltage conversion unit calculated by the RMS value calculation unit; and an abnormality index calculated by the abnormality index calculation unit.

10. In a single measurement of the subject's body composition, this measurement, which measures the subject's body composition, is performed multiple times in succession. The measurement result exclusion unit excludes, as an inappropriate calculation result, the information on body composition calculated in response to the measurement in which the abnormality index exceeds a specified value among the multiple measurements. The body composition measurement device according to claim 9, wherein the body composition information calculation unit calculates the subject's body composition result using one or more pieces of information remaining from the multiple measurements, after inappropriate calculation results have been excluded by the measurement result exclusion unit.

11. The impedance trajectory calculation unit calculates, for each of the multiple measurements, the resistance R∞ when the frequency of the multiple probe currents is infinite and the resistance R0 when the frequency of the multiple probe currents is 0, based on the impedance trajectory. The measurement result exclusion unit excludes R∞ and R0 obtained from the measurement in which the abnormality index exceeds a specified value among the multiple measurements as inappropriate calculation results. The body composition measurement device according to claim 10, wherein the body composition information calculation unit excludes inappropriate calculation results by the measurement result exclusion unit, calculates the average value of the remaining R∞ and the average value of R0, and uses the calculated average value of R∞ and the average value of R0 to calculate the body composition result of the subject.

12. A control method for a body composition analyzer that measures the body composition of a subject according to measurement conditions, Step (a) involves applying multiple probe currents of different frequencies to the subject's body and detecting a voltage signal relating to the voltage generated between predetermined parts of the subject's body when the multiple probe currents are applied to the subject's body, and a current signal relating to the current flowing through the subject's body. Step (a) above is amplified to a magnitude suitable for measuring electrical impedance, and Step (b) Step (a) above is to convert the current signal detected by step (a) into a voltage of a magnitude suitable for electrical impedance measurement (c), Step (d) calculates information regarding the electrical impedance for each frequency based on the voltage signal amplified in step (b) and the current signal converted in step (c), Step (e) is to calculate an impedance trajectory based on the information regarding the electrical impedance for each frequency calculated in step (d), Step (f) is to calculate information about the subject's body composition based on the impedance trajectory calculated in step (e), Step (g) is to calculate an anomaly index, which is an indicator of the anomaly of the impedance trajectory calculated in step (e), Step (h) is to calculate a value relating to the magnitude of the amplified voltage signal in step (b) and / or a value relating to the magnitude of the current signal flowing through the subject's body detected in step (a), Step (i) includes determining the changeable measurement conditions of the body composition measuring device based on at least one of the values ​​relating to the magnitude of the voltage signal and the values ​​relating to the magnitude of the current signal calculated in step (h), and the abnormality index calculated in step (g). Prior to the main measurement to measure the body composition of the subject, a preliminary measurement is performed to determine the measurement conditions. In step (i) above, the frequency bands of the multiple probe currents applied to the subject's body are determined as measurement conditions for the measurement in the measurement, A control method comprising the steps: in step (i), if the abnormality index calculated in step (g) in the preliminary measurement exceeds a specified value, the measurement conditions are changed to increase or decrease the upper limit on the high-frequency side in the frequency band of the plurality of probe currents, and the preliminary measurement is performed again; and if the abnormality index calculated in the preliminary measurement performed again is less than or equal to the specified value, the frequency band in the preliminary measurement performed again is determined as the measurement condition for the main measurement.

13. Step (j) is to exclude inappropriate information from the subject's body composition information calculated in step (f) based on at least one of the values ​​relating to the magnitude of the voltage signal, the values ​​relating to the magnitude of the current signal, and the abnormality index calculated in step (g), The control method according to claim 12, including the following:

14. In a single measurement of the subject's body composition, this measurement, which measures the subject's body composition, is performed multiple times in succession. In step (j), among the multiple measurements, the information on the subject's body composition calculated in step (f) corresponding to the measurement in which the abnormality index exceeds a specified value is excluded as an inappropriate calculation result. Step (k) involves, among the multiple measurements, excluding the inappropriate calculation result in step (j), and using one or more pieces of information regarding the body composition of the subject to calculate the result of the subject's body composition; The control method according to claim 13, including the method described in claim 13.

15. For each of the aforementioned multiple measurements, the steps include calculating the resistance R∞ when the frequency of the multiple probe currents is infinite and the resistance R0 when the frequency of the multiple probe currents is 0, based on the impedance trajectory. The steps include: excluding R∞ and R0 obtained from the measurement in which the abnormality index exceeds a specified value among the multiple measurements, as inappropriate calculation results used in calculating the information on body composition; The control method according to claim 14, comprising the steps of: excluding the aforementioned inappropriate calculation results, calculating the average value of the remaining R∞ and the average value of R0, and using the calculated average value of R∞ and the average value of R0 to calculate the result of the subject's body composition.

16. A control program for causing a computer to execute the control method described in any one of claims 12 to 15.

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