Body composition measurement device and control method

Abstract

The present invention provides: a body composition measurement device capable of preventing an excessive change in measurement results when re-measurement is performed on the same subject in a short period of time; and a control method. A body composition measurement device 1 measures electrical impedance on the basis of a voltage signal and a current signal when a plurality of probe currents having different frequencies are applied to the body of a subject according to measurement conditions. The body composition measurement device 1, when re-executing the electrical impedance measurement by calling individual identification information, executes the electrical impedance measurement using the measurement conditions used in the previous measurement and stored in a storage unit if a predetermined time has not elapsed between the re-executed measurement date / time and the previous measurement date / time stored in the storage unit; and executes the electrical impedance measurement using measurement conditions re-determined by a measurement condition determination unit if the predetermined time has elapsed between the re-executed measurement date / time and the previous measurement date / time stored in the storage unit.

Description

Body composition measuring device and control method

[0001] The present invention relates to a body composition measuring device and a control method.

[0002] Conventionally, devices that measure a subject's body composition, such as body fat weight and body water content, based on the bioelectrical impedance method have been known (see, for example, Patent Documents 1 to 4 listed below). These devices measure the bioelectrical impedance of the subject's body based on the voltage generated in the subject's body and the current flowing through the body when weak alternating currents of multiple frequencies are passed through the body, and calculate the body composition from the measured bioelectrical impedance.

[0003] Japanese Patent Application Laid-Open No. 2000-316829 Japanese Patent Application Laid-Open No. 9-154829 Japanese Patent Application Laid-Open No. 2003-116805 Japanese Patent No. 3984332

[0004] However, stable measurement of bioelectrical impedance (hereinafter simply referred to as "electrical impedance") may be difficult or the measured value of bioelectrical impedance may change depending on factors such as the subject's physique (e.g., if the subject is significantly overweight or extremely small), body movement, whether or not there is contact between the arms and armpits, whether or not there is contact between the thighs of both legs, and the administration of fluid replacement, etc. As a result, the measurement results of the subject's body composition may vary.

[0005] To address this issue, it is conceivable to reduce the variability in measurement results by measuring body composition multiple times and using the average value, but no technology has been proposed to optimize measurement conditions for each measurement. The inventors have been developing a technology for automatically adjusting measurement conditions based on a measurement accuracy index, a voltage amplitude index, and a current amplitude index, as a technology for optimizing measurement conditions for each measurement. However, during the development of this technology, it was discovered that when comparative measurements or remeasurements are performed on the same subject within a short period of time in each measurement of body composition, if the measurement conditions are automatically optimized each time and the measurement conditions differ between the measurements to be compared, the measurement results may change excessively, making it impossible to properly compare the measurement values.

[0006] The present invention has been made in consideration of the above circumstances, and its main purpose is to provide a body composition measuring device and control method that can prevent measurement results from changing excessively when comparative measurements or remeasurements are performed on the same subject within a short period of time.

[0007] The above object of the present invention can be achieved by the following means.

[0008] The body composition measurement device measures the body composition of a subject according to measurement conditions. The body composition measurement device includes a current input unit, a voltage detection unit, a current detection unit, a voltage signal amplification unit, a current-voltage conversion unit, an electrical impedance calculation unit, an impedance locus calculation unit, a body composition information calculation unit, an effective value calculation unit, a measurement condition determination unit, a control unit, and a memory unit. The current input unit inputs multiple probe currents of different frequencies into the subject's body. The voltage detection unit detects a voltage signal related to the voltage generated between predetermined parts of the subject's body when the multiple probe currents are input into the subject's body by the current input unit. The current detection unit detects a current signal related to the current flowing through the subject when the multiple probe currents are input into 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 used for electrical impedance measurement. The current-voltage conversion unit converts the current signal detected by the current detection unit into a voltage of a magnitude used for electrical impedance measurement. The electrical impedance calculation unit calculates information about the electrical impedance for each frequency based on the voltage signal amplified by the voltage signal amplifier and the current signal converted by the current-voltage conversion unit. The impedance locus calculation unit calculates an impedance locus based on the information about the electrical impedance for each frequency calculated by the electrical impedance calculation unit. The body composition information calculation unit calculates information about the body composition of the subject based on the impedance locus calculated by the impedance locus calculation unit. The effective value calculation unit calculates a value related to the magnitude of the voltage signal amplified by the voltage signal amplifier and / or a value related to the magnitude of the current signal converted by the current-voltage conversion unit. The measurement condition determination unit determines the changeable measurement conditions of the body composition measurement device based on the value related to the magnitude of the voltage signal calculated by the effective value calculation unit and / or the value related to the magnitude of the current signal calculated by the effective value calculation unit. The control unit controls the execution of electrical impedance measurement using the determined measurement conditions.The storage unit stores the measurement conditions determined when the electrical impedance measurement is performed, in association with the individual identification information and measurement date and time of the subject. When the control unit calls up the individual identification information and re-performs the electrical impedance measurement, if the date and time of the re-performed measurement has not yet elapsed a predetermined time since the date and time of the previous measurement stored in the storage unit, the control unit performs the electrical impedance measurement using the measurement conditions used in the previous measurement stored in the storage unit, and if the date and time of the re-performed measurement has elapsed a predetermined time or more since the date and time of the previous measurement stored in the storage unit, the control unit performs the electrical impedance measurement using the measurement conditions re-determined by the measurement condition determination unit.

[0009] A method for controlling a body composition measurement device includes measuring the body composition of a subject according to measurement conditions, the body composition measurement device including a control unit that controls execution of an electrical impedance measurement using the determined measurement conditions, and a storage unit that, when the electrical impedance measurement is performed, stores the determined measurement conditions in association with the subject's individual identification information and the measurement date and time.The control method includes the steps of: (a) injecting a plurality of probe currents having different frequencies into the body of the subject; detecting a voltage signal related to a voltage generated between predetermined parts of the body of the subject when the plurality of probe currents are injected into the body of the subject; and detecting a current signal related to a current flowing through the body of the subject; (b) amplifying the voltage signal detected in the step (a) to a magnitude used for electrical impedance measurement; (c) converting the current signal detected in the step (a) into a voltage having a magnitude used for electrical impedance measurement; (d) calculating information related to electrical impedance for each frequency based on the voltage signal amplified in the step (b) and the current signal converted in the step (c); (e) calculating an impedance locus based on the information related to the electrical impedance for each frequency calculated in the step (d); and (e) calculating information related to the body composition of the subject based on the impedance locus calculated in the step (e). and (h) determining the changeable measurement conditions of the body composition measuring device based on the value related to the magnitude of the voltage signal amplified in step (b) and / or the value related to the magnitude of the current signal flowing through the body of the subject detected in step (a). The control unit is equipped with a first measurement mode in which, when calling up the individual identification information and re-executing the electrical impedance measurement, if a predetermined time has not elapsed since the date and time of the previous measurement stored in the storage unit, the control unit performs the electrical impedance measurement using the measurement conditions used in the previous measurement stored in the storage unit, and if a predetermined time has elapsed since the date and time of the previous measurement stored in the storage unit, the control unit performs the electrical impedance measurement using the measurement conditions re-determined in step (h).

[0010] According to the body composition measuring device of the present invention, when re-measurement is performed on the same subject within a short period of time, it is possible to prevent the measurement results from changing excessively.

[0011] 1 is a block diagram illustrating the general configuration of a body composition measurement device according to an embodiment of the present invention. FIG. 1 is a conceptual diagram illustrating the usage state of the body composition measurement device shown in FIG. 1. FIG. 2 is a schematic block diagram illustrating the hardware configuration of the control unit shown in FIG. 1. FIG. 3 is a graph showing an example of an impedance locus. FIG. 4 is a flowchart illustrating an outline of the processing procedure of a body composition measurement method. FIG. 5 is a subroutine flowchart illustrating details of the process (S104) for measuring body composition under the measurement conditions of the previous measurement in FIG. 5. FIG. 6 is a subroutine flowchart subsequent to FIG. 6A. FIG. 6B is a subroutine flowchart illustrating the process of determining the presence or absence of an abnormality in electrical impedance measurement (S222). FIG. 7 is a subroutine flowchart illustrating details of the process of measuring body composition by optimizing measurement conditions. FIG. 8 is a subroutine flowchart illustrating details of the process of preliminary measurement (S302) in the flowchart of FIG. 7. FIG. 9 is a schematic diagram illustrating the flow of current (current signal) in cells in a living organism according to the frequency. FIG. 9 is a schematic electrical equivalent circuit diagram of the living organism shown in FIG.

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0013] Fig. 1 is a block diagram illustrating the schematic configuration of a body composition measurement device according to one embodiment, Fig. 2 is a conceptual diagram illustrating the use of the body composition measurement device, and Fig. 3 is a schematic block diagram illustrating the hardware configuration of the control unit shown in Fig. 1.

[0014] <Configuration of Body Composition Measurement Device 1> The body composition measurement device 1 is a device for measuring the body composition of the body E of a subject (patient, care recipient, etc.). The body composition measurement device 1 can be a portable body composition measurement device powered by a battery. A portable body composition measurement device can measure the body composition of a subject in any location, such as at the bedside, in an outpatient clinic, or during a visit.

[0015] 1 , the body composition measuring device 1 includes a control unit 10, a current measuring unit 20, a signal output unit 30, a voltage measuring unit 40, a recording unit 62, an input unit 63, a speaker 64, a display unit 65, and a memory 66. The electrical impedance calculating unit 120, the current measuring unit 20, the signal output unit 30, and the voltage measuring unit 40 constitute an electrical impedance measuring unit 50.

[0016] The recording unit 62 can be configured by, for example, a RAM (Random Access Memory), an SSD (Solid State Drive), or an HDD (Hard Disk Drive).

[0017] The input unit 63 has, for example, a touch panel, various keys, switches, etc., and accepts instructions from an operator such as a medical professional, various settings, information about the subject (hereinafter also referred to as "subject information"), etc. Instructions from the operator include, for example, instructions to start / end measurement, and various settings include, for example, settings about how to output and display measurement results. In addition, the information about the subject may include the subject's ID (subject ID), the subject's name, furigana, height, weight, age, sex, medical history, etc.

[0018] The display unit 65 has a display arranged on one surface of the housing of the body composition measurement device 1. The display unit 65 may also include a light-emitting element (LED: Light-Emitting Diode) for visually notifying of abnormalities and the like.

[0019] <Surface Electrodes Lc, Hc, Lp, Hp> As shown in FIG. 2 , surface electrodes Lc and Hc and surface electrodes Lp and Hp are attached (attached with adhesive sheets or the like) to predetermined locations on the subject's body E, and these surface electrodes are connected to body composition measurement device 1 via connection cables 2A to 2D, respectively. More specifically, surface electrode Lc is attached to the instep of the right foot of the subject's body E during measurement, and surface electrode Hc is attached to the back of the right hand of the subject's body E during measurement. Surface electrode Lc is connected to current measurement unit 20, and surface electrode Hc is connected to signal output unit 30. Surface electrode Hc is paired with surface electrode Lc. Furthermore, surface electrode Lp is attached to the instep of the right foot of the subject's body E during measurement, and surface electrode Hp is attached to the back of the right hand of the subject's body E during measurement. Surface electrode Hp is paired with surface electrode Lp.

[0020] 3, the control unit 10 includes a CPU (Central Processing Unit) 11, a ROM 12, a RAM 13, an auxiliary storage unit 14, and an input / output I / F 15. The auxiliary storage unit 14 includes, for example, an SSD or an HDD. The CPU 11, the ROM 12, the RAM 13, and the auxiliary storage unit 14 constitute a computer.

[0021] The CPU 11 realizes various functions by loading a control program stored in advance in the ROM 12 or the auxiliary storage unit 14 into the RAM 13 and executing it. The ROM 12 is a non-volatile memory. The ROM 12 stores various parameters and the like necessary for the calculation processing of the CPU 11. The RAM 13 is a volatile memory and temporarily stores the results of the calculation processing by the CPU 11 and various data. The auxiliary storage unit 14 stores an operating system (OS), programs such as a control program, and the results of the calculation processing by the CPU 11. In this embodiment, the auxiliary storage unit 14 also stores subject information. The subject information may include at least one piece of information about the subject, such as the subject's name, reading, height, weight, age, and gender, in addition to a subject ID (individual identification information). The subject information is stored, for example, by linking at least one piece of information about the subject to the subject ID. Furthermore, the auxiliary memory unit 14 also stores measurement data. In addition to the subject ID, the measurement data may include, for example, a timestamp including the date and time when each measurement was performed, measurement conditions, and measurement results. The measurement results may include impedance and body composition calculation results. Measurement conditions are various conditions used to measure body composition in the body composition measurement device 1, such as amplifier gain. The amplifier gain may be the gain Gi of the I / V converter 23 (described later) and the gain Gd of the differential amplifier 43. Details of the measurement conditions will be described later. The measurement data is stored with, for example, a timestamp, measurement conditions, and measurement results linked to the subject ID. In this way, in this embodiment, subject information and measurement data are associated via the subject ID, and the timestamp is linked to the subject ID. Therefore, it is easy to refer to the timestamp corresponding to the subject ID during measurement.

[0022] In this embodiment, the body composition measurement device 1 has functions such as registering a new subject ID, measuring body composition, displaying measurement history, updating subject information, changing the measurement mode, and various settings. The control unit 10 displays a menu screen on the display unit 65 for selecting from the above-mentioned multiple functions, and prompts the user (a medical professional such as a doctor or nurse) to select a function to execute. The user selects a desired function from the list of functions displayed on the menu screen. The function is selected by operating a switch, key input, touch operation, or the like, depending on the input device such as a switch, key, or touch panel provided in the input unit 63, or the GUI (Graphical User Interface).

[0023] The new subject ID registration is a function for registering the ID of a new subject in the body composition measurement device 1. The control unit 10 displays a subject information registration screen and prompts the user to register the subject information. The user inputs, for example, the subject ID, the subject's name, furigana, height, weight, age, and gender using the input unit 63 in accordance with the display on the registration screen. The control unit 10 stores the input subject information in the auxiliary memory unit 14.

[0024] The body composition measurement function measures the body composition of a subject based on bioelectrical impedance analysis. When the user selects the body composition measurement function from the menu screen, an input screen for identifying the subject to be measured is displayed. The user inputs subject identification information, such as the subject ID, subject name, and furigana, according to the input screen. The control unit 10 identifies the subject ID of the subject to be measured based on the input subject identification information. Then, the user operates the "OK button" to start body composition measurement. Note that the subject identification information may be the subject's last name or the first character of the last name. The control unit 10 can also display candidates for the subject ID (subject name) to be measured based on the subject identification information input by the user and registered subject information. The user selects the subject ID (subject name) to be measured from the displayed candidates.

[0025] The display of the measurement history is a function that displays the measurement results of the biological composition of each registered subject. The display unit 65 can display, as the measurement history, for example, the subject's height, weight, BMI (Body Mass Index), lean body mass, fat mass, body fat percentage, phase angle, total body water volume, extracellular fluid volume, intracellular fluid volume, hydration rate, extracellular water ratio, etc. The phase angle is a value that represents the reactance when an alternating current passes through a cell membrane of a living body, expressed as an angle. The user can check the measurement history displayed on the display unit 65.

[0026] The subject information update function is a function for updating the subject information registered in the body composition measurement device 1. This function allows the user to update the subject information appropriately, even if information such as the subject's weight changes. The user inputs subject identification information, such as the subject ID, subject name, and furigana. The control unit 10 identifies the subject ID to be updated based on the input subject identification information. The subject identification information may also be the subject's last name or the first character of the last name. The control unit 10 can also display candidate subject IDs (subject names) to be updated based on the subject identification information input by the user and the registered subject information. The user selects the subject ID (subject name) to be updated from the displayed candidates. The control unit 10 may be configured to display candidate subject IDs (subject names) in chronological order using a timestamp in the measurement data. When displaying in chronological order, the subject IDs of the measurement data arranged in chronological order may be used to call up the subject information linked by the subject IDs, thereby displaying not only the subject IDs but also the subject names in chronological order. Furthermore, the measurement data may be configured to include the subject names, and the subject names may be extracted from the measurement data arranged in chronological order to display them in chronological order. In this case, the user can select candidate subject IDs or candidate subject names to be updated from the candidate subject IDs and candidate subject names arranged in chronological order.

[0027] The measurement mode change is a function for changing the measurement mode. In this embodiment, the body composition measurement device 1 has multiple measurement modes, including a normal measurement mode, a continuous measurement mode, and a moisture change mode. The user can select and execute one of these measurement modes. The normal measurement mode is a measurement mode in which body composition measurement (electrical impedance measurement) is performed once, and the continuous measurement mode is a measurement mode in which body composition measurement (electrical impedance measurement) is performed continuously multiple times.

[0028] In the normal measurement mode and the continuous measurement mode, if a predetermined time or more has passed since the previous body composition measurement for the same subject, the measurement conditions are optimized (updated each time). On the other hand, if a predetermined time or more has not passed since the previous body composition measurement for the same subject, the body composition measurement may be performed using the same measurement conditions as the previous one. The predetermined time is not particularly limited, but may be set to, for example, about six hours. The reason for this will be explained later.

[0029] In normal measurement mode, the measurement conditions are optimized before measuring body composition. Optimizing the measurement conditions during measurement reduces 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 there is contact between the arm and armpit, and the administration of fluid replacement to the subject.

[0030] However, if the measurement conditions are optimized for each measurement, and remeasurement is performed in a short time (for example, after two hours), the measurement results may change significantly due to differences in the measurement conditions (for example, amplifier gain) between the two consecutive measurements. In such a case, when a user checks the changes in the measurement results over time, the measurement results will differ significantly, but the user will not be able to distinguish between changes due to the measurement conditions and changes due to the subject's condition, which may make it difficult to interpret the measurement results.

[0031] Therefore, in this embodiment, if a predetermined time has not passed since the previous body composition measurement for the same subject, the body composition can be measured using the same measurement conditions as the previous measurement, thereby preventing significant changes in measurement results due to different settings of measurement conditions (e.g., amplifier gain) between two consecutive measurements.

[0032] In continuous measurement mode, measurements are repeatedly performed at regular intervals specified by the user (e.g., every 10 minutes for two hours). Therefore, the measurement conditions are optimized for the first measurement, but the measurement conditions are fixed for the second and subsequent measurements, and body composition measurements can be performed using the same measurement conditions as the first measurement. This prevents significant changes in measurement results due to differences in measurement conditions (e.g., amplifier gain) throughout the continuous measurements.

[0033] Furthermore, the function of measuring body composition using the same measurement conditions as the previous measurement when a predetermined time has not elapsed since the previous body composition measurement may be configured to be applied between different measurement modes. For example, if a predetermined time has not elapsed since the previous normal measurement mode measurement, the first measurement in the continuous measurement mode may be performed using the same measurement conditions as the previous normal measurement mode measurement. Furthermore, when the normal measurement mode is being performed, if a predetermined time has not elapsed since the last measurement in the continuous measurement mode, the measurement in the normal measurement mode may be performed using the same measurement conditions as the previous continuous measurement mode measurement.

[0034] On the other hand, the inventors experimentally confirmed that even if a predetermined time has not passed since the previous body composition measurement, optimizing the measurement conditions each time a measurement is performed rather than using the previous measurement conditions can result in more accurate measurements if the subject's body composition changes significantly. A case in which the subject's body composition changes significantly would occur, for example, when a dehydrated subject is given fluid replacement. Therefore, in this embodiment, the body composition measurement device 1 further includes a water change mode that optimizes the measurement conditions each time a measurement is performed, even if a predetermined time has not passed since the previous body composition measurement. As described above, the predetermined time can be set to, for example, approximately six hours. This is to confirm changes in the subject's body composition before and after drug administration. Drugs administered to subjects include, for example, anticancer drugs and intravenous drugs. Although this varies depending on the type of cancer and drug, anticancer drugs are generally administered via intravenous infusion over one to four hours. Furthermore, some intravenous drugs have a medicinal effect lasting approximately three hours. In other words, body composition can change significantly within a short period of time, approximately one to four hours after the start of drug administration. Furthermore, the subject's body composition may be affected by their physical condition. Furthermore, depending on the schedule of the user who operates the body composition measurement device 1, it may not be possible to measure the subject's body composition immediately after drug administration. Therefore, it is preferable to set the predetermined time to approximately six hours, allowing for a certain amount of time so that the user can confirm the difference between the subject's body composition before drug administration and the changes in the subject's body composition after administration.

[0035] Thus, in this embodiment, the body composition measurement device 1 includes a normal measurement mode and a continuous measurement mode, which measure body composition using the same measurement conditions as the previous measurement if a predetermined time has not passed since the previous body composition measurement for the same subject. Furthermore, the body composition measurement device 1 also includes a moisture change mode, which optimizes the measurement conditions for each measurement if the subject's body composition has changed significantly, even if a predetermined time has not passed since the previous body composition measurement for the same subject. When re-measuring body composition, the control unit 10 controls the device to measure body composition using the previous measurement conditions if a predetermined time has not passed since the previous measurement. If a predetermined time has passed since the previous measurement, the control unit 10 measures body composition using the measurement conditions determined again by the measurement condition determination unit 180 (described later). Specific processing steps for the body composition measurement method will be described later.

[0036] The control unit 10 and the input unit 63 function as a time change unit and can accept changes to the predetermined time. The time change unit accepts input from the user regarding the predetermined time. The time change unit can also allow the user to select the predetermined time from multiple time settings prepared in advance.

[0037] The input / output I / F 15 is an input / output interface for sending and receiving data to and from a system unit (not shown).

[0038] By the CPU 11 executing the control program, the control unit 10 functions as an impedance trajectory calculation unit 110, an electrical impedance calculation unit 120, a judgment unit 130, an alarm 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 an averaging mode control unit 190 (see Figure 1 again).

[0039] <Electrical Impedance Measuring Unit 50> The electrical impedance measuring unit 50 generates a plurality of probe currents with different frequencies, applies the probe currents of each frequency to the subject's body E, and calculates the electrical impedance of the subject's body E from the relationship between the probe current and the voltage between the electrodes when the probe currents of each frequency are flowing through the subject's body E. Note that, although the following mainly describes the case where the electrical impedance is calculated, the electrical impedance measuring unit 50 may also be configured to calculate the electrical admittance, which is the reciprocal of the electrical impedance, and / or the electrical impedance.

[0040] <Signal Output Unit 30> The signal output unit 30 functions as a current input unit and applies a multi-frequency probe current (hereinafter referred to as "multi-frequency current") Ib to the subject's body E in accordance with instructions from the control unit 10. 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 AC currents with frequencies increasing in increments of 2.5 kHz from 2.5 kHz to 350 kHz. The signal output unit 30 includes a measurement signal generator 31 and an output buffer 32.

[0041] The measurement signal generator 31 outputs a measurement signal (current) Ia to the output buffer 32 at predetermined intervals in accordance with instructions from the CPU 11. The interval at which the measurement signal generator 31 outputs the measurement signal Ia can be, for example, approximately 800 nsec. The measurement signal Ia is a signal that changes at predetermined frequency intervals within the predetermined interval. The measurement signal Ia may, for example, change at 15 kHz frequency intervals in the range of 1 kHz to 400 kHz. Alternatively, the measurement signal may be a measurement signal containing many frequency components, such as the M-sequence signal disclosed in Japanese Patent Laid-Open No. 10-14898.

[0042] More specifically, the measurement signal generator 31 has an M-sequence signal generator, a square wave generator, and a time divider (not shown), and generates a signal with a period T*(2 ｎThe M-sequence signal generator generates, in a time-division manner, an M-sequence signal with a period of 511 (=2) bits (n is a positive integer) and a signal with a period of T*N=2*W (N is an integer of 2 or more) in which the first W periods are 1 and the remaining W periods are 0. For example, the M-sequence signal generator generates an M-sequence signal with a period of 511 (=2) bits (n is a positive integer) operating at 1.25 MHz. ｎ The square wave generator generates a square wave with a period of (32 / 1.25MHz) and a duty of 50%. The time divider divides 0.8μsec = 1 / 1.25MHz into four equal parts, and provides a control signal that switches the signal so that the M-sequence signal is output for the first three periods (0.6μsec) and the square wave is output for the last 0.2μsec.

[0043] Furthermore, the measurement signal generator 31 can change the frequency band of the multi-frequency probe current in accordance with instructions from the CPU 11. For example, it can be set to 1 to 1,000 kHz, 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 it is also possible to make specifications that allow fine adjustment in increments of 0.5 kHz or 1 kHz.

[0044] The output buffer 32 maintains the input measurement signal Ia at a constant current state and outputs it to the surface electrode Hc as a multi-frequency current Ib. This causes the multi-frequency current Ib to flow 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 approximately 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 essentially constant even when the subject changes. The output buffer 32 may also be configured with an analog filter, which removes high-frequency noise before applying the measurement signal Ia.

[0045] <Current Measuring Unit 20> The current measuring unit 20 converts the multi-frequency current Ib into a voltage and outputs the resulting voltage signal Vb. The current measuring unit 20 has a current detecting unit 24, an I / V converter 23, a BPF (band pass filter) 22, and an A / D converter 21.

[0046] The I / V converter 23 is a current / voltage converter that functions as a current-voltage converter. The current detection unit 24 converts the multi-frequency current Ib flowing through the subject's body E when the signal output unit 30 applies a multi-frequency current to the subject's body E into a current signal and detects it. The I / V converter 23 converts the multi-frequency current Ib flowing between the surface electrode Hc and the 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 be able to change the gain Gi in response to instructions from the control unit 10. The I / V converter 23 outputs the obtained voltage Vb to the BPF 22.

[0047] The BPF 22 is a band-pass filter that cuts out signals in unnecessary bands from the voltage signal Vb and outputs the result to the A / D converter 21. The pass band of the BPF 22 can be selected appropriately depending on the specifications of the body composition measurement device 1. The pass band of the BPF 22 can be set to, for example, approximately 1 kHz to 800 kHz.

[0048] The A / D converter 21 converts the analog voltage Vb into a digital voltage signal Vb in accordance with a digital conversion instruction from the control unit 10. The digital voltage signal Vb is stored in time series in the memory 66 as voltage data in a form that is synchronously added with the synchronously added data up to one cycle before of the M-sequence signal.

[0049] The memory 66 transmits and receives the stored data to and from the control unit 10 in response to a request from the control unit 10. Specifically, the data is transmitted and received to and from the effective value calculation unit 70 and the electrical impedance calculation unit 120. The memory 66 can be configured, for example, by an SRAM.

[0050] The control unit 10 functions as a synchronous addition unit, and performs synchronous addition on the data of the voltage signal Vb sent from the current measurement unit 20 in order to remove, for example, quantum errors in A / D conversion by the A / D converter 21. More specifically, the synchronous addition unit synchronously adds the synchronously added data of the M-sequence signal up to one cycle before with the current A / D converted data, and stores the result in the memory 66. That is, the memory 66 stores one cycle's worth of M-sequence signal after the synchronous addition. Thereafter, the next A / D converted data is similarly synchronously added to the one cycle's worth of M-sequence signal stored in the memory 66, and the data is overwritten in the memory 66. This type of synchronous addition process is repeated a fixed number of times (N times).

[0051] Alternatively, the A / D converted data may be stored as is in the memory 66 and then subjected to synchronous addition processing later. In this case, however, it may take time to perform synchronous addition processing on the huge amount of stored data, and a sufficient number of synchronous additions may not be possible due to limitations on the memory capacity of the memory that stores the data.

[0052] If the i-th data in memory 66 is d(i) and the synchronous addition value is D(n) (n = 0 to 1021), then D(n) = Σd(2 * 511 * m + n), where the sum symbol Σ is used to sum up m = 0 to 31.

[0053] The number of repetitions of the synchronous addition is stored in advance in the auxiliary storage unit 14. Alternatively, the number of repetitions of the synchronous addition may be set by the operator via the input unit 63.

[0054] In this way, the digital voltage signal Vb corresponding to the current Ib is input to the electrical impedance calculation unit 120 by the signal output unit 30 and the current measurement unit 20. On the other hand, the digital voltage signal Vp is input to the electrical impedance calculation unit 120 from the voltage measurement unit 40.

[0055] <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 has a voltage detection unit 44, a differential amplifier 43, a BPF 42, and an A / D converter 41.

[0056] The voltage detection unit 44 detects a voltage signal related to the voltage between the surface electrodes Hp and Lp. The differential amplifier 43 functions as a voltage signal amplifier, amplifying the voltage between the surface electrodes Hp and Lp detected by the voltage detection unit 44 using a gain Gd to a voltage Vp of a magnitude used for measuring electrical impedance, and outputs the amplified voltage. The differential amplifier 43 is configured to be able to change the gain Gd in response to instructions from the control unit 10. The differential amplifier 43 outputs the voltage Vp to the BPF 42.

[0057] The BPF 42 cuts off signals in a predetermined band from the input voltage signal Vp and outputs the result to the A / D converter 41. The pass band of the BPF 42 can be selected appropriately according to the specifications of the body composition measurement device 1. The pass band of the BPF 42 can be set to, for example, approximately 1 kHz to 800 kHz.

[0058] The A / D converter 41 converts the analog voltage Vp into a digital voltage signal Vp in accordance with a digital conversion instruction from the control unit 10. The digital voltage signal Vp is stored in the memory 66 as voltage data in a form that is synchronously added with synchronously added data up to one period before the M-sequence signal. Note that the synchronous addition of the voltage data is the same as that of the voltage signal Vb obtained by conversion from the current, and therefore a detailed description thereof will be omitted.

[0059] 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 bioelectrical impedance method. More specifically, the electrical impedance calculation unit 120 calculates the electrical impedance of the subject's body E using data based on the voltage signals Vb and Vp after a specified number of repetitions of the synchronous addition process stored in the memory 66. 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 results in Vp(f) and Vb(f), which are functions of frequency. Note that if the measurement signal is a signal whose frequency changes continuously, this process is unnecessary because Vp(f) and Vb(f) are directly measured as functions of frequency. Next, the voltages Vp(f) and Vb(f) are averaged, and the electrical impedance Z(f) for each frequency is calculated as Z(f) = Vp(f) / Vb(f).

[0060] The electrical impedance calculation unit 120 stores the input digital voltage signals Vb, Vp and the calculated electrical impedance in RAM 13, and outputs them to the impedance locus calculation unit 110, the determination unit 130, and the body composition measurement unit 150. Hereinafter, the voltage signals Vb, Vp will also be referred to as measurement data. The principles of the bioelectrical impedance method will be described later.

[0061] The impedance locus calculation unit 110 calculates the center coordinates and radius of the impedance locus from the electrical impedance at each frequency input from the electrical impedance calculation unit 120. The impedance locus calculation unit 110 also calculates the resistance R∞ when the frequency of the probe current is ∞, the resistance R0 when the frequency of the probe current is 0, R∞ / R0, and the critical frequency fc. The impedance locus calculation unit 110 outputs the impedance locus, R∞, R0, R∞ / R0, and the critical frequency fc to the determination unit 130, the body composition measurement unit 150, and the abnormality determination unit 160.

[0062] The impedance locus calculation unit 110 calculates the impedance locus using the least squares method. The resistances R∞ and R0 can be calculated by finding the intersection of the calculated impedance locus with the reactance X=0. The critical frequency fc can be calculated from the frequencies corresponding to the electrical impedance measurements located on both the left and right sides of the point on the impedance locus where the reactance is smallest.

[0063] FIG. 4 is a graph showing an example of an impedance locus. The horizontal axis of the graph shown in FIG. 4 is resistance R, and the vertical axis is reactance X. Furthermore, black circles ("●") or open circles ("◯") represent measurement points (measured values) of electrical impedance measurement at each frequency. In the figure, black circles represent measurement points at frequencies higher than the critical frequency fc (also called "high frequencies"), and open circles represent measurement points at frequencies lower than the critical frequency fc (also called "low frequencies"). In the example shown in FIG. 4, the dots at 350 kHz represent measurement values ​​measured when the highest frequency current was applied, and the dots at 2.5 kHz represent measurement values ​​measured when the lowest frequency current was applied.

[0064] The impedance locus is a curve calculated to fit the measured electrical impedance at each frequency. Typically, the impedance locus is approximately a Cole-Cole arc.

[0065] When the frequency is very low or very high, the reactance X is substantially 0, and the electrical impedance Z is substantially equal to the resistance R. Therefore, among the intersections of the impedance locus and X=0, the one with the larger resistance is the resistance R0 when the frequency is 0, and the one with the smaller resistance is the resistance R∞ when the frequency is ∞. R0 is said to reflect the extracellular fluid volume, and R∞ is said to reflect the total body water volume.

[0066] The determining 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 measurements at each frequency on the impedance locus and the size of the radius of the impedance locus.

[0067] When determining that there was no abnormality in the electrical impedance measurement, determination unit 130 outputs an OK signal indicating "no abnormality" to body composition measurement unit 150 and notification unit 140. On the other hand, when determining that there was an abnormality in the electrical impedance measurement, determination unit 130 outputs an NG signal indicating "abnormality" to body composition measurement unit 150 and notification unit 140.

[0068] When an OK signal is input, the notification unit 140 does not issue a notification, and when an NG signal is input, the notification unit 140 notifies the subject or the operator of the body composition measurement device 1 of an abnormality. The method of notifying 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 an abnormality has occurred in the electrical impedance measurement, or by a combination of these methods.

[0069] The body composition measurement unit 150 calculates and measures body composition based on the calculated electrical impedance value, the impedance trajectory, and information about the subject 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 may measure body composition both when an OK signal is input and when an NG signal is input. In this embodiment, an example will be described in which body composition is measured only when an OK signal is input.

[0070] Body composition measurement unit 150 functions as a body composition information calculation unit and outputs the measured body composition to display unit 65. Display unit 65 displays the measured body composition. If determination unit 130 outputs an NG signal to notification unit 140, it is determined that there was an abnormality in the electrical impedance measurement, and a message is displayed on the display of display unit 65 indicating that the body composition measurement has been stopped.

[0071] The body composition measurement section 150 also outputs the measured body composition to the recording section 62. The recording section 62 records the measured body composition.

[0072] The specific method for measuring body composition is not particularly limited, and any known method can be used. For example, the amount of body water can be measured by regression analysis. Specifically, the conductor part of the human body, i.e., the body water part, is assumed to be a cylinder with a length L and a cross-sectional area S. In this case, the resistance of the conductor part of the human body is proportional to the length L and inversely proportional to the cross-sectional area S. Therefore, R = ρL / S, and when transformed, S = ρL / R. Substituting this into the volume V = LS, the volume V of the conductor part of the human body is ρL ２ Therefore, total body water (TBW) is calculated as follows: TBW = α + βL ２ / R, where α and β are statistically determined constants. The accuracy of the measured total body water can be improved by adding body characteristic data such as height to the above formula. Specifically, total body water (TBW) can be calculated by the following formula: TBW = α + βL ２ A more accurate measurement of body water can be achieved by measuring body water using the formula: / R + γW + δAGE, where W is body weight and AGE is age. Note that fat-free mass (FFM) can also be measured using a similar method.

[0073] The abnormality determination unit 160 functions as an abnormality index calculation unit and calculates an abnormality index that is an index of abnormality of the impedance locus calculated by the impedance locus calculation unit 110. A specific method for calculating the abnormality index will be described later. If the abnormality index exceeds a predetermined specified value (first threshold), the abnormality determination unit 160 determines that the impedance locus is abnormal, and if the abnormality index is equal to or less than the specified value, the abnormality determination unit 160 determines that the impedance locus is not abnormal. The specified value may be, for example, 0.004.

[0074] The effective value calculation unit 170 calculates a value related to the magnitude of the voltage signal Vp (hereinafter referred to as "V-POWER") and / or a value related 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 effective value Vpa of the voltage signal Vp and the effective value Vba of the voltage signal Vb, respectively.

[0075] For example, the effective value calculation unit 170 uses data of the voltage signal Vp input from the voltage measurement unit after a synchronous addition process has been repeated a specified number of times, and calculates V-POWER of the voltage signal Vp by performing digital signal processing on the data. The effective value calculation unit 170 also uses data of the voltage signal Vb input from the current measurement unit after a synchronous addition process has been repeated a specified number of times, and performs digital signal processing on the data to calculate I-POWER of the voltage signal Vb. More specifically, the effective value calculation unit 170 calculates V-POWER and I-POWER by determining the root mean square (RMS) of all sampled data based on the definition of the effective value of an AC signal.

[0076] On the other hand, in this embodiment, a current Ib consisting of only an AC component is applied to the subject's body E via the capacitor of the output buffer 32. The effective value is equal to the standard deviation σ for data of an AC signal with no DC component and an average value of 0. Therefore, the effective value calculation unit 170 calculates V-POWER and I-POWER, respectively, by calculating the standard deviation σ of the data of the digital voltage signals Vp and Vb.

[0077] Here, it is desirable that V-POWER be as large as possible within the range that can be processed by the circuit. For example, an upper threshold value for V-POWER can be set within a range in which almost all data falls within ±3σ. If the resolution of the A / D converter 41 is 8 bits, V-POWER can be set to a value preferably between 20 and 40, and more preferably between 30 and 40.

[0078] 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 via the limiting resistor so that the measurement signal Ia remains essentially constant even when the subject being measured is changed to another subject. When the resolution of the A / D converter 21 is 8 bits, I-POWER can be set to a value preferably between 20 and 40, and more preferably between 30 and 40.

[0079] 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 one of the surface electrodes being measured becoming detached from the subject's body E.

[0080] 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 the abnormality index. The changeable measurement conditions of the body composition measurement device 1 may be, for example, the gain Gd of the differential amplifier 43, the Gi of the I / V converter 23, the frequency band Bw (or upper limit frequency) of the electrical impedance measurement, and the number of data points Np for creating the electrical impedance locus. 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. Furthermore, when the measurement condition determination unit 180 determines only the amplifier gain as a measurement condition, it can determine the changeable measurement conditions of the body composition measurement device 1 based on at least one of V-POWER and I-POWER. A method and specific examples of determining the measurement conditions will be described later.

[0081] In this embodiment, the body composition measurement device 1 is configured to be operable in any one of a first averaging mode, a second averaging mode, and a third averaging mode. The averaging mode control unit 190 controls which of the first averaging mode, the second averaging mode, and the third averaging mode is used to perform the measurement.

[0082] The first averaging mode is an averaging mode in which the synchronous addition process is repeated a predetermined number of times on the voltage signal Vb obtained by converting the multi-frequency current Ib input from the current measuring unit 20 into a voltage by the electrical impedance measuring unit 50, and the data of the voltage signal Vp input from the voltage measuring unit 40. (For example, the synchronous addition process of the synchronous addition data of the M-sequence signal from one cycle before and the M-sequence signal from the next cycle is repeated 128 times x 40 times in total. The 128 times of the process are performed to cancel pseudo-noise due to a rectangular wave, and the 40 times of the process are performed because the greater the number of times, the higher the rate of removal of asynchronous noise.) Hereinafter, the first averaging mode may also be referred to as the normal mode. The second averaging mode is an averaging mode in which the number of repetitions is smaller than that of the first averaging mode, and the third averaging mode is an averaging mode in which the number of repetitions is greater than that of the first averaging mode. For example, the predetermined number of repetitions of the second averaging mode may be 128 times x 30 times, and the total number of repetitions of the third averaging mode may be 128 times x 50 times. The number of repetitions of the second averaging mode may be set as a multiple of the number of repetitions of the first averaging mode, such as 2 / 3 times or 1 / 2 times. Similarly, the number of repetitions of the third averaging mode may be set as a multiple of the number of repetitions of the first averaging mode, such as 3 / 2 times or 2 times. When the number of repetitions is 128 times x 40, the number of 128 times may be increased or decreased, or the number of 40 times may be increased or decreased.

[0083] For example, the averaging mode control unit 190 starts measurement of the subject's body composition in the second averaging mode. When the abnormality determination unit 160 determines that the impedance locus in the second averaging mode is abnormal during measurement in the second averaging mode, i.e., when the abnormality index exceeds a specified value, the averaging mode control unit 190 increases the number of repetitions of the synchronous addition process compared to the second averaging mode and performs measurement again. The increment Δn in the number of repetitions is not particularly limited (e.g., 128 times × (40 + 1) times, 128 times × (40 + 5) times, etc.).

[0084] The timer 185 has a real-time clock and outputs the current time.

[0085] Furthermore, when measurement is performed in the first averaging mode, if the abnormality determination unit 160 determines that the impedance locus in the first averaging mode is abnormal, the averaging mode control unit 190 can perform measurement again in the third averaging mode. More specifically, the averaging mode control unit 190 first performs measurement in the second averaging mode, and if the abnormality determination unit 160 determines that the impedance locus in the second averaging mode is abnormal, the averaging mode control unit 190 transitions to measurement in the first averaging mode, and if the abnormality determination unit 160 determines that the impedance locus in the first averaging mode is abnormal, the averaging mode control unit 190 transitions to measurement in the third averaging mode.

[0086] (Method of measuring body composition using body composition measurement device 1) Hereinafter, a method of measuring body composition using the body composition measurement device of this embodiment will be described with reference to Figures 5 to 8. Figure 5 is a flowchart illustrating an example of an outline of the processing procedure of the method of measuring body composition. The processing of the flowchart shown in the figure is realized by the CPU 11 executing a control program.

[0087] First, the user inputs subject information necessary for measurement (step S101). For example, during the first measurement, the user registers the subject information necessary for measurement. The user uses the input unit 63 to input, for example, the subject's ID, height, weight, gender, and age into the body composition measurement device 1. Height, weight, gender, and age information are necessary for body composition measurement. Furthermore, in order to distinguish between subject information items, the user can input the subject's name and furigana in addition to the subject ID. For example, it is preferable that the user input the subject's name and furigana when initially registering the subject information. Note that, for subsequent measurements, the user can omit inputting subject information that has not changed since the initial registration and input / update only subject information that has changed since the initial registration. An example of subject information that is prone to change is weight. After completing the input (update) of the subject information, the user instructs the body composition measurement device 1 to begin body composition measurement.

[0088] Next, the control unit 10 determines whether there are measurement results for the same subject ID within a predetermined time period (step S102). More specifically, the control unit 10 checks whether measurement results for the same subject ID as the subject to be measured within a predetermined time period prior to the current time (the start time of body composition measurement) are stored in the auxiliary storage unit 14. For example, the control unit 10 obtains the current time from the timer 85 and compares the time recorded in the latest timestamp of the measurement data for the subject ID to be measured with the current time. If the time recorded in the latest timestamp is prior to the current time and within a predetermined time period from the current time, the control unit 10 determines that there are measurement results within the predetermined time period.

[0089] If there is a measurement result for the same subject ID within a predetermined time (S102: YES), the control unit 10 reads out the measurement conditions for the previous measurement (step S103). In this embodiment, the measurement conditions include amplifier gain. The previous measurement is the time of the latest timestamp. The control unit 10 reads out the measurement conditions for the time of the latest timestamp from the auxiliary storage unit 14.

[0090] Next, the control unit 10 measures the body composition under the measurement conditions of the previous measurement (step S104). The method of measuring the body composition under the measurement conditions of the previous measurement will be described in detail later.

[0091] Next, the control unit 10 stores the measurement results (step S105). The control unit 10 associates the subject ID with the time stamp, measurement conditions, and measurement results, and stores them in the auxiliary storage unit 14 (step S105), and ends the process (END).

[0092] On the other hand, if there are no measurement results for the same subject ID within the predetermined time (S102: NO), the control unit 10 optimizes the measurement conditions and measures the body composition (step S106). The method for optimizing the measurement conditions and measuring the body composition will be described in detail later. The control unit 10 saves the measurement results (step S105) and ends the process (END).

[0093] <Measurement Mode> As described above, the body composition measuring device 1 of this embodiment can perform electrical impedance measurement once (normal measurement mode) or multiple times continuously at predetermined time intervals (continuous measurement mode) in response to a user instruction.

[0094] Depending on whether or not a predetermined time has passed since the previous measurement date and time, the body composition measurement device 1 either performs electrical impedance measurement using the previous measurement conditions, or performs electrical impedance measurement by optimizing the measurement conditions each time. In this way, the mode in which the measurement conditions to be used are selected depending on whether or not a predetermined time has passed since the previous measurement date and time, and a single measurement is performed, is called the first measurement mode (corresponding to the normal measurement mode described above).

[0095] Specifically, in the first measurement mode, the control unit 10 determines whether a predetermined time or more has passed since the previous measurement date and time at the time of the re-executed measurement, and if the predetermined time or more has not passed, performs the electrical impedance measurement using the measurement conditions used in the previous measurement. On the other hand, if the predetermined time or more has passed since the previous measurement date and time at the time of the re-executed measurement, the control unit 10 performs the electrical impedance measurement using the measurement conditions re-determined by the measurement condition determination unit 180.

[0096] The control unit 10 can also perform continuous electrical impedance measurement at a predetermined time interval using the previous measurement conditions linked to the retrieved subject information, i.e., the most recent measurement conditions, which is called the second measurement mode (corresponding to the continuous measurement mode described above).

[0097] On the other hand, the control unit 10 can also set the measurement conditions using the measurement condition determination unit 180 each time before performing an electrical impedance measurement (this is called the third measurement mode). Furthermore, in the third measurement mode, the control unit 10 can set the measurement conditions using the measurement condition determination unit 180 each time a measurement is performed, even if the measurement date and time at the time of remeasurement has not yet been completed within a predetermined time period since the previous measurement (this corresponds to the moisture change mode described above).

[0098] In this way, the control unit 10 has the first, second, and third measurement modes and has the function of switching between these measurement modes. When measuring in the second measurement mode, the control unit 10 controls switching between the first and second measurement modes. When measuring in the third measurement mode, the control unit 10 controls switching between the first and third measurement modes.

[0099] <Process for measuring body composition under measurement conditions at the time of the previous measurement (S104)> Figure 6A is a subroutine flowchart illustrating the details of the process for measuring body composition under measurement conditions at the time of the previous measurement (S104) in Figure 5. That is, it is a subroutine flowchart illustrating the details of the main measurement process in the first measurement mode when a predetermined time or more has not passed since the previous measurement date and time, or in the second measurement mode. Figure 6B is a subroutine flowchart following Figure 6A. The processes of the subroutine flowcharts shown in Figures 6A and 6B are realized by the CPU 11 executing a control program.

[0100] First, the control unit 10 sets the measurement conditions (step S201). The control unit 10 sets the measurement conditions for the previous measurement as the measurement conditions for the current measurement. The averaging mode control unit 190 also starts the measurement of the subject's body composition in the second averaging mode.

[0101] Next, a probe current using the M sequence is applied (step S202). More specifically, the signal output unit 30, which functions as a current applying unit, sets the frequency band of the probe current to be applied to the subject, and applies the probe current using the M sequence to the subject. Then, the current detecting unit 24 and the voltage detecting unit 44 detect a voltage signal related to the voltage between predetermined parts of the subject's body E, and a current signal related to the flowing current (steps S203 and S204).

[0102] Next, the voltage signal amplifier (differential amplifier 43) amplifies the detected voltage signal (step S206). The voltage signal amplifier amplifies the voltage signal detected in step S204 to a voltage Vp suitable for measuring electrical impedance.

[0103] In parallel, the current-voltage converter (I / V converter 23) converts the detected current signal into a voltage signal (step S205). The current-voltage converter 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 band, including noise (steps S207 and S208). Furthermore, these data undergo A / D conversion (steps S209 and S210), and the voltage and current signals are averaged by synchronously adding the synchronously added data up to one previous cycle of the M-sequence signal with the A / D-converted data (steps S211 and S212), thereby improving the S / N ratio. The effective value calculator 170 then calculates V-POWER using the averaged voltage signal Vp and I-POWER using the averaged voltage signal Vb (steps S213 and S214). Then, the voltage signals Vp and Vb, which are functions of time, are subjected to Fourier transform processing to be converted into functions of frequency (steps S215 and S216).

[0104] In reality, the current input unit, voltage signal amplifier, current-to-voltage converter, and effective value calculator 170 are implemented by hardware (electronic circuits), so the processes in steps S201 to S216 are performed simultaneously. That is, signal processing related to current and signal processing related to voltage are performed in parallel.

[0105] The electrical impedance measuring 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 an impedance locus by performing curve fitting using a least-squares method (step S218). In this measurement, the control unit 10 performs synchronous addition of the synchronously added data and A / D converted data from the previous M-sequence signal period for each of the voltage signals Vp and Vb (steps S212 and S211). The number of repetitions of the synchronous addition (averaging times; a total of 128 times × N) is set to the number set in the second averaging mode (e.g., N = 40, for a total of 128 times × 40). The control unit 10 then uses the impedance locus to calculate the resistance R∞ when the frequency of the probe current is ∞ and the resistance R0 when the frequency of the probe current is 0 (step S319). The control unit 10 also uses the impedance locus to calculate an abnormality index (step S220).

[0106] Next, the abnormality determination unit 160 determines whether the calculated abnormality index is equal to or less than a specified value (step S221). If the abnormality index is equal to or less than the specified value (step S221: YES), the control unit 10 determines whether or not there is an abnormality in the electrical impedance measurement (step S222). Details of the determination method for determining whether or not there is an abnormality in the electrical impedance measurement will be described later. If there is no abnormality in the electrical impedance measurement (step S222: YES), the body composition measurement unit 150 calculates and displays the subject's body composition based on R0, R∞, and information about the subject (particularly gender, age, height, and weight) (step S223). At this time, the body composition measurement unit 150 transmits the measurement results to the display unit 65, and the display unit 65 displays the measurement results on the display. Additionally, the body composition measurement unit 150 similarly displays, together with the body composition results, information about the electrical impedance calculated in step S217, the impedance locus calculated in step S218, R0 and R∞ calculated in step S219, and the abnormality index calculated in step S220. Furthermore, the recording unit 62 stores these measurement results.

[0107] On the other hand, if there is an abnormality in the electrical impedance measurement (step S222: NO), the control unit 10 stops the body composition measurement, notifies the abnormality (step S224), and terminates the process (return). For example, the control unit 10 sends a warning message indicating that there is an abnormality in the electrical impedance measurement to the display unit 65, and the display unit 65 displays the warning message on the display. This prevents an operator such as a medical professional from misinterpreting the body composition of the subject's body E.

[0108] On the other hand, if the abnormality index exceeds the specified value (step S221: NO), the control unit 10 increases the total number of averaging operations (the number of repetitions in synchronous addition) performed in steps S211 and S212 (step S225). For example, the control unit 10 increases the total number of averaging operations from a total of 128 times N to a total of 128 times (N + Δn). Alternatively, the averaging mode control unit 190 switches the averaging mode from the second averaging mode to the first averaging mode. As a result, when the increment Δn is 10, the total number of averaging operations increases from a total of 128 times N to a total of 128 times (N + 10). Furthermore, if the abnormality index exceeds the specified value in the first averaging mode, the averaging mode control unit 190 switches the averaging mode from the first averaging mode to the third averaging mode. As a result, the total number of averaging operations further increases to a total of 128 times (N + 10 + 10). If the abnormality index exceeds a specified value, instead of or in addition to increasing the total number of averaging times, the user may be notified that there is an abnormality in the measurement by displaying a message on the display unit or by sound or voice.

[0109] Next, the control unit 10 determines whether the total number of averaging operations is equal to or greater than the maximum number (step S226). The maximum total number of averaging operations may be, for example, 128 times x 80 times, or may be 128 times x 120 times. If the total number of averaging operations is equal to or greater than the maximum number (step S226: YES), the control unit 10 stops the body composition measurement, notifies the user of an abnormality (step S227), and terminates the process (return). The control unit 10 determines that the measurement data is not accurate enough and stops the body composition measurement. The control unit 10 also notifies the operator that measurement data of sufficient accuracy cannot be obtained. Alternatively, the control unit 10 may control the display unit 65 to display the measurement results as reference values ​​without stopping the body composition measurement.

[0110] On the other hand, if the total number of averaging operations is smaller than the maximum number (step S226: NO), the control unit 10 proceeds again to the electrical impedance measurement process (steps S202 to S225). In this way, the control unit 10 performs electrical impedance measurements by gradually increasing the total number of averaging operations within a range in which the total number of averaging operations does not exceed the maximum number, thereby minimizing the number of averaging operations while keeping the variation in impedance measurements within a specified range.

[0111] [Process for Determining Whether or Not an Anomaly Has Occurred in Electrical Impedance Measurement (Step S222)] Fig. 6C is a subroutine flowchart illustrating the process for determining whether or not an anomaly has occurred in the electrical impedance measurement (S222) in Fig. 6B. The process of the subroutine flowchart shown in Fig. 6C is realized by the CPU 11 executing a control program.

[0112] In the following step S231, the critical frequency fc is used as an index to evaluate the bias in the distribution of impedance measurement values ​​at each frequency relative to the impedance locus, thereby determining whether or not there is an abnormality in the electrical impedance measurement. In step S232, R∞ / R0 is used as an index to determine whether or not there is an abnormality in the electrical impedance measurement based on whether or not the magnitude of the impedance locus is within a normal range. Note that steps S231 and S232 may be performed in any order. The following describes, as an example, a case where steps S231 and S232 are performed in this order.

[0113] The determination unit 130 determines whether or not there is an abnormality in the critical frequency fc (step S231). In this step, the critical frequency fc is used as an index to evaluate the bias in the distribution of the impedance measurement values ​​at each frequency relative to the impedance locus, thereby determining whether or not there is an abnormality in the electrical impedance measurement.

[0114] The determination unit 130 determines whether the critical frequency fc calculated by the impedance locus 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 S231: YES) and proceeds to step S232. 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 S231: NO). Therefore, the determination unit 130 determines that there is an abnormality in the electrical impedance measurement (step S234) and ends the process (return).

[0115] Typically, for a healthy person, the critical frequency fc is around 50 kHz. However, the critical frequency fc varies from person to person. For this reason, it is preferable that the lower limit of the critical frequency fc is about 5 to 20 kHz, and the upper limit is about 90 to 150 kHz. That is, in step S231, the allowable range of the critical frequency fc is set to about 5 to 150 kHz, and preferably, a range of about 10 to 100 kHz is further set.

[0116] If the determination unit 130 determines that there is no abnormality in the critical frequency fc (step S231: YES), it determines whether there is an abnormality in R∞ / R0 (step S232). In this step, using R∞ / R0 as an index, it determines whether there is an abnormality in the electrical impedance measurement based on whether the magnitude of the impedance locus is within a normal range. The determination unit 130 determines whether R∞ / R0 is within a predetermined range. If R∞ / R0 is within the predetermined range, the determination unit 130 determines that there is no abnormality in the value R∞ / R0 (step S232: YES), and proceeds to step S403, where it determines that there is no abnormality in the electrical impedance measurement.

[0117] On the other hand, if the value R∞ / R0 is outside the predetermined range, the determination unit 130 determines that there is an abnormality in R∞ / R0 (step S232: NO), and therefore determines that there is an abnormality in the electrical impedance measurement (step S234), and ends the process (return).

[0118] Normally, for a healthy person, the value of R∞ / R0 is about 0.6 to 0.8 (60% to 80%). Therefore, in step S232, the allowable range of R∞ / R0 can be set to about 0.85 to 0.9 or less (about 0% to 90%).

[0119] In this embodiment, only the value of R∞ / R0 is determined in step S232. However, the system may be configured to determine whether the values ​​of R∞ and R0 are within appropriate ranges in addition to the value of R∞ / R0. That is, the system may be configured to determine that an abnormality has occurred in the electrical impedance measurement when R∞ or R0 becomes abnormally large or abnormally small. For example, the determination index may be that R∞ and R0 are both greater than 0 Ω. Alternatively, the determination index may be that R∞ and R0 are each within the range of 100 to 1000 Ω.

[0120] In this embodiment, the display of measurement results or notification of abnormalities during measurement is based on the abnormality index and the determination of the presence or absence of an abnormality in the electrical impedance measurement, but this is not limited to this. That is, I-POWER and V-POWER may be added to the determination index, or the determination may be made using any one or more combinations of I-POWER, V-POWER, the abnormality index, and the determination of the presence or absence of an abnormality in the electrical impedance measurement. Furthermore, the determination of the presence or absence of an abnormality in the electrical impedance measurement may also be made using any one or more combinations of the critical frequency fc, R∞ / R0, and the respective values ​​of R∞ and R0.

[0121] <Process for optimizing measurement conditions and measuring body composition (step S106)> Figure 7 is a subroutine flowchart illustrating the main process for optimizing measurement conditions and measuring body composition. That is, this is a subroutine flowchart illustrating the main process when a predetermined time or more has passed since the previous measurement date and time in the first measurement mode, or in the second measurement mode. The process of the subroutine flowchart shown in the figure is realized by the CPU 11 executing a control program.

[0122] [Main Processing] As described 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 their armpits, whether or not the thighs are in contact with each other, and whether or not the subject is receiving fluid replacement. Therefore, if the measurement conditions are not suitable for measuring the subject's electrical impedance, the accuracy of the body composition measurement may be insufficient. For example, if the subject moves a lot during measurement, if the subject is extremely swollen, or if the subject is extremely thin, the electrical impedance measurement may be unstable, and there is a high possibility that discontinuous values ​​will occur 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.

[0123] Therefore, in this embodiment, a preliminary measurement (hereinafter referred to as "preliminary measurement") is performed to determine the measurement conditions for the main measurement prior to the main measurement of the subject's body composition. In this specification, the term "preliminary measurement" refers to a measurement performed to determine the measurement conditions for the main measurement performed after the preliminary measurement, and does not directly aim to calculate information about body composition. The term "main measurement" refers to a measurement performed according to the measurement conditions determined by the preliminary measurement, and to calculate information about body composition.

[0124] First, the control unit 10 sets the measurement conditions for the preliminary measurement (step S301). The control unit 10 sets each measurement condition to an initial value for the preliminary measurement. For example, the initial value of the gain Gd of the differential amplifier 43 can 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. The initial value of Gi of the I / V converter 23 can be set so that I-POWER is approximately 40 (approximately the maximum value). The initial value of the frequency band Bw for electrical impedance measurement can be set, for example, to 2.5 kHz to 350 kHz. The number of data points Np is set so that the frequency band Bw is measured every 2.5 kHz. If the frequency band Bw is, for example, 2.5 kHz to 350 kHz, the control unit 10 sets the number of data points Np to 350 kHz / 2.5 kHz = 140 points.

[0125] Next, the control unit 10 performs a preliminary measurement to determine the measurement conditions for the main measurement (step S302). In this embodiment, the control unit 10 performs the preliminary measurement under conditions in which the number of repeated synchronous additions is fewer than in the main measurement. This reduces the time required for the preliminary measurement. In addition, the preliminary measurement can be performed by performing steps up to the calculation of I-POWER and V-POWER, and determining the measurement conditions without calculating the electrical impedance for each frequency, the impedance locus, or the body composition, thereby further reducing the time required for the preliminary measurement. Note that FIG. 6 illustrates a case in which the preliminary measurement is completed with steps up to the calculation of I-POWER, V-POWER, and the abnormality index.

[0126] In the preliminary measurement, the measurement conditions are selected so that the abnormality index is equal to or lower than a specified value (lower is preferable) and V-POWER is maximized within a range that does not exceed a specified value (upper limit). If any of the abnormality index, V-POWER, or I-POWER is inappropriate, the measurement conditions are revised. The specific processing procedure will be described later.

[0127] Next, the control unit 10 performs the main measurement (step S303). At this time, the control unit 10 sets the measurement conditions to the measurement conditions determined in the preliminary measurement, fixes the measurement conditions, and then performs the main body composition measurement.

[0128] [Preliminary Measurement Processing] Fig. 8 is a subroutine flowchart illustrating the details of the preliminary measurement processing (S302) in the flowchart of Fig. 7. The processing of the subroutine flowchart shown in Fig. 8 is realized by the CPU 11 executing a control program.

[0129] First, the signal output unit 30, which functions as a current input unit, sets the frequency band of the probe current to be input to the subject (S401), and applies the probe current using an M sequence to the subject (S402).Then, the current detection unit 24 and the voltage detection unit 44 detect a voltage signal related to the voltage between predetermined parts of the subject's body E and a current signal related to the flowing current (steps S403 and S404).

[0130] Next, the voltage signal amplifier (differential amplifier 43) amplifies the detected voltage signal (step S406). The voltage signal amplifier amplifies the voltage signal detected in step S404 to a voltage Vp suitable for measuring electrical impedance.

[0131] In parallel, the current-voltage converter (I / V converter 23) converts the detected current signal into a voltage signal (step S405). The current-voltage converter converts the current signal detected in step S403 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 band, including noise (steps S407 and S408). Furthermore, these data undergo A / D conversion (steps S409 and S410), and the voltage and current signals are averaged by synchronously adding the synchronously added data up to one previous cycle of the M-sequence signal with the A / D-converted data (steps S411 and S412), thereby improving the S / N ratio. The effective value calculator 170 then calculates V-POWER using the averaged voltage signal Vp and I-POWER using the averaged voltage signal Vb (steps S413 and S414). Then, the voltage signals Vp and Vb, which are functions of time, are subjected to Fourier transform processing to be converted into functions of frequency (steps S415 and S416).

[0132] In reality, the current input unit, voltage signal amplifier, current-to-voltage converter, and effective value calculator 170 are implemented by hardware (electronic circuits), so the processes in steps S401 to S416 are performed simultaneously. That is, signal processing related to current and signal processing related to voltage are performed in parallel.

[0133] The electrical impedance measuring unit 50 calculates information about the electrical impedance for each frequency based on Vp and Vb, which are functions of frequency (step S417), and calculates the impedance locus by performing curve fitting using a least squares calculation means (step S418).

[0134] Next, the abnormality determination unit 160 calculates an abnormality index (step S419). The abnormality determination unit 160 calculates the abnormality index based on the impedance locus calculated in step S418. In this embodiment, the abnormality index is calculated as the variation in the impedance measurement value at each frequency relative to the impedance locus. That is, a larger abnormality index indicates a larger variation and lower fitting accuracy of the measurement data, and a smaller abnormality index indicates a smaller variation and higher fitting accuracy of the measurement data.

[0135] More specifically, the abnormality determination unit 160 calculates the distance e(f) in a predetermined direction between the electrical impedance Z(f) measured at frequency (f) and the impedance locus. The distance e(f) may be, for example, the distance between the electrical impedance and the impedance locus in the radial direction of the impedance locus, or the distance in the horizontal or vertical direction. For example, in the radial direction, the distance e0(f) between the measured electrical impedance Z(f) and the impedance locus can be expressed as shown in Equation (1) below using the distance d(f) between the electrical impedance Z(f) and the center of the impedance locus and the radius r.

[0136] e0(f)=d(f)−r (1) The abnormality determination unit 160 calculates the sum of squares of the calculated distances e0(f), Σe0(f) ２ is calculated as the abnormality index.

[0137] Furthermore, as shown in the following formula (2), taking into consideration the size of the subject's body E, the sum of squares of e0(f) / r, which is obtained by dividing e0(f) by r, is given as Σe1(f) ２ can also be calculated as an abnormality index.

[0138] Σe1(f) ２ =Σ{e0(f) / r} ２...(2) The radius r of the impedance locus varies greatly depending on the body type of the subject, i.e., the size (length and cross-sectional area) of the body E. Therefore, the magnitude of e0(f) varies greatly depending on the height of the subject, etc. By dividing the distance e0(f) by the radius r, it is possible to suppress the dependency of the abnormality index on the size of the subject's body E. In other words, by using the above formula (1), it is possible to accurately calculate the abnormality index regardless of whether the subject is tall or short.

[0139] Furthermore, as shown in the following formula (3), instead of dividing e0(f) by the radius r, e0(f) is divided by the subject's height h, and the sum of squares of e0(f) / h is obtained: Σe2(f) ２ can also be calculated as an abnormality index.

[0140] Σe2(f) ２ =Σ{e0(f) / h} ２ ...(3) In this way, the abnormality determination unit 160, for example, ２ , Σe1(f) ２ , or Σe2(f) ２ is calculated as the abnormality index.

[0141] Next, the measurement condition determination unit 180 determines whether the calculated V-POWER, I-POWER, and abnormality index are appropriate (step S420). The measurement condition determination unit 180 determines whether the measurement conditions are appropriate based on V-POWER, I-POWER, and the abnormality index. If the V-POWER and I-POWER based on the measured voltage Vp and current Ib and the abnormality index based on the impedance locus are within the appropriate range (step S420: YES), the measurement condition determination unit 180 determines the measurement conditions for this measurement (step S421) and ends 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 within the range of 20 to 40 and the abnormality index is equal to or less than a specified value (e.g., 0.004). On the other hand, the measurement condition determining 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 the abnormality index exceeds a specified value.

[0142] On the other hand, if the measurement conditions are not appropriate (step S420: NO), the measurement condition determination unit 180 changes the measurement conditions (step S422). The control unit 10 changes at least one of the measurement conditions and returns to the processing of step S401. To change the measurement conditions, the control unit 10 sets the gain Gd and / or the gain Gi to a value that is one step lower. Furthermore, with regard to the frequency band, for example, the control unit 10 increases or decreases the maximum frequency (the upper limit on the high-frequency side).

[0143] The measurement condition determination unit 180 may set the gain Gd as the measurement condition for this measurement such that the abnormality index is below a specified value (e.g., 0.004) and V-POWER is maximized within a range not exceeding an upper limit value (e.g., 40).

[0144] Furthermore, the measurement condition determination unit 180 may set the frequency band in which the abnormality index is below a specified value (e.g., 0.004) and is the smallest, as the measurement condition for the actual measurement, or may set the frequency band in which V-POWER is the largest within a range that does not exceed an upper limit value (e.g., 40) as the measurement condition for the actual measurement.

[0145] [Main Measurement Process] The main measurement process is basically the same as the process of measuring body composition under the measurement conditions of the previous measurement shown in Figures 6A to 6C, except that in step S201 of Figure 6A, the measurement conditions determined in the preliminary measurement process are set instead of the measurement conditions of the previous measurement. Therefore, a detailed description of the main measurement process will be omitted.

[0146] [Measurement principle by bioelectrical impedance method] FIG. 9 is a schematic diagram illustrating the flow of current (current signal) in cells in a living body according to frequency, and FIG. 10 is a schematic electrical equivalent circuit diagram of the living body shown in FIG. 9.

[0147] Bioelectrical impedance analysis is a method for measuring (or estimating) a subject's body composition, such as body water distribution, body fat percentage, and body fat mass, from bioelectrical impedance. Bioelectrical impedance is composed of the resistance of the body to the current carried by ions in the body and the reactance associated with various types of polarization processes produced by cell membranes, tissue interfaces, and non-ionized tissues.

[0148] Capacitance, which is the reciprocal of reactance, mainly causes a time delay in the current, creating a phase shift. This phase shift can be geometrically quantified as the electrical phase angle, which is the arc tangent of the ratio of reactance to resistance. The magnitude of bioelectrical impedance Z is expressed as Z = R (resistance) + X (reactance). ２ =R ２ +X ２ is defined by

[0149] Bioelectrical impedance Z, resistance R, reactance X, and electrical phase angle Φ are frequency dependent. As shown in Figure 9, when the frequency of the current is very low, the bioelectrical impedance Z at the cell membrane and tissue interface becomes very high. Therefore, the current does not flow through the cell membrane or tissue interface, but only through the extracellular fluid. Therefore, the measured bioelectrical impedance Z is substantially equal to the resistance R.

[0150] As the frequency of the current increases, the current (low-frequency component) flows through cell membranes and tissue interfaces. This increases the reactance X and widens the phase angle Φ. However, when the current frequency exceeds a critical frequency fc, the capacitive properties of the cell membranes and tissue interfaces are lost. Therefore, when 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 substantially equal to the resistance R again. Note that the "critical frequency" refers to the frequency at which the reactance is maximized.

[0151] As shown in FIG. 10, the equivalent circuit of the human body is composed of a circuit in which the cell membrane capacitance Cmk and the intracellular fluid resistance Rik are connected in series, and a parallel circuit in which the extracellular fluid resistance Re is connected.

[0152] When the current frequency is low, the current flows mainly in 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 substantially passes through the cell membrane. Therefore, the cell membrane capacitance Cm is considered to be substantially short-circuited. Therefore, when the current frequency is high, the impedance Z is substantially equal to the combined resistance Ri·Re / (Ri+Re). Here, Cm and Ri refer to the combined capacitance and combined resistance of Cmk and Rik for the entire tissue.

[0153] Therefore, extracellular fluid resistance Re can be determined by applying a low-frequency current and measuring the electrical impedance of the subject's body. Furthermore, intracellular fluid resistance Ri can be determined based on the determined extracellular fluid resistance Re and the electrical impedance of the subject's body when a high-frequency current is applied, using Z = Ri · Re / (Ri + Re). The subject's body composition can then be estimated based on the obtained intracellular fluid resistance Ri and extracellular fluid resistance Re. The method for measuring the subject's body composition is not particularly limited, and conventionally known methods can be used.

[0154] In this specification, "body composition" refers to all data related to the composition of body E. For example, "body composition" includes the amount of a body composition, the ratio of a specific composition to body E, and the distribution of a specific composition to body E. "Composition" refers to what makes up body E, and specific examples of composition include total body water, intracellular fluid volume, extracellular fluid volume, protein, fat, and calcium content. Specific examples of body composition include body fat percentage, body fat mass, lean mass (muscle mass), phase angle (muscularity), total body water distribution, bone density, skeletal muscle mass, fat-free index, skeletal muscle mass index, and edema rate. Specific examples of total body water distribution include intracellular fluid volume, extracellular fluid volume, and total body water volume. In the above, total body water volume is the sum of intracellular fluid volume and extracellular fluid volume.

[0155] <Operational Effects> The body composition measuring device 1 of the present embodiment described above provides the following operational effects.

[0156] If the measurement date and time when the electrical impedance measurement is re-executed has not yet elapsed a predetermined time since the previous measurement date and time stored in the auxiliary storage unit 14, the control unit 10 performs the electrical impedance measurement using the measurement conditions used in the previous measurement stored in the auxiliary storage unit 14. On the other hand, if the measurement date and time when the electrical impedance measurement is re-executed has elapsed a predetermined time or more since the previous measurement date and time stored in the auxiliary storage unit 14, the control unit 10 performs the electrical impedance measurement using the measurement conditions re-determined by the measurement condition determination unit 180. This allows the body composition measuring device 1 to prevent excessive changes in the measurement results when re-measuring the same subject within a short period of time.

[0157] Although the body composition measuring device, control method, and control program of the present invention have been described in the above embodiments, it goes without saying that those skilled in the art can make additions, modifications, and omissions as appropriate within the scope of the technical concept of the present invention.

[0158] For example, instead of or in addition to the electrical impedance and impedance locus, the electrical admittance and admittance locus may be calculated. Furthermore, the attachment locations of the surface electrodes are not limited to the hands and feet.

[0159] The control program may be provided by a computer-readable recording medium such as a USB memory, a flexible disk, or a CD-ROM, or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is typically transferred to and stored in a memory or storage device. The control program may be provided as standalone application software, or may be incorporated into the software of each device as a function of the server.

[0160] In addition, in the embodiments, part or all of the processing executed by the control program may be replaced with hardware such as a circuit.

[0161] Furthermore, with regard to the number of repetitions of synchronous addition, in the normal mode, the synchronous addition process of the synchronously added data of the M-sequence signal one cycle before and the M-sequence signal for the next cycle is performed a total of 128 times x 40 times, but this is not limited to this. The number of 128 processes performed to cancel the pseudo-noise due to the square wave can also be freely set. Furthermore, the number of processes performed to cancel the pseudo-noise due to 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 x 40 times or a number that is a multiple of 32, such as (32 times x A times) x 40 times. Furthermore, the number of repetitions of the synchronous addition process performed to cancel the pseudo-noise due to the square wave may be increased or decreased between averaging modes.

[0162] Furthermore, in the body composition measurement device 1 of this embodiment, the averaging mode control unit 190 is configured to automatically control which of the first, second, and third averaging modes is used for measurement, but the selection may be made by user input. That is, the input unit 63 may be configured to allow selection of one of the first, second, and third averaging modes, or to allow the number of repetitions to be input. This configuration allows for improved measurement accuracy for users who have ample time for measurement.

[0163] This application is based on a Japanese patent application (Patent Application No. 2024-052988) filed on March 28, 2024, the disclosure of which is incorporated herein by reference in its entirety.

[0164] 1 Body composition measurement device, 10 Control unit, 20 Current measurement unit, 21 A / D converter, 22 BPF, 23 I / V converter, 24 Current detection unit, 30 Signal output unit, 31 Measurement signal generator, 32 Output buffer, 40 Voltage measurement unit, 41 A / D converter, 42 BPF, 43 Differential amplifier, 44 Voltage detection unit, 50 Electrical impedance measurement unit, 62 Recording unit, 63 Input unit, 64 Speaker, 65 Display unit, 66 Memory, 110 Impedance locus calculation unit, 120 Electrical impedance calculation unit, 130 Determination unit, 140 Notification unit, 150 Body composition measurement unit, 160 Abnormality determination unit, 170 Effective value calculation unit, 180 Measurement condition determination unit, 190 Averaging mode control section.

Claims

1. A body composition measurement device that measures the body composition of a subject in accordance with measurement conditions, comprising: a current input unit that inputs multiple probe currents of different frequencies into the body of the subject; a voltage detection unit that detects a voltage signal related to a voltage generated between predetermined parts of the body of the subject when the multiple probe currents are input into the body of the subject by the current input unit; a current detection unit that detects a current signal related to a current flowing through the subject when the multiple probe currents are input into the body of the subject by the current input unit; a voltage signal amplification unit that amplifies the voltage signal detected by the voltage detection unit to a magnitude used for electrical impedance measurement; a current-voltage conversion unit that converts the current signal detected by the current detection unit into a voltage of a magnitude used for electrical impedance measurement; an electrical impedance calculation unit that calculates information related to 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; and an impedance locus calculation unit that calculates an impedance locus based on the information related to the electrical impedance for each frequency calculated by the electrical impedance calculation unit. a body composition information calculation unit that calculates information about the body composition of the subject based on the impedance locus calculated by the impedance locus calculation unit; an effective value calculation unit that calculates a value related to the magnitude of the voltage signal amplified by the voltage signal amplification unit and / or a value related to the magnitude of the current signal converted by the current-voltage conversion unit; a measurement condition determination unit that determines the changeable measurement conditions of the body composition measuring device based on the value related to the magnitude of the voltage signal calculated by the effective value calculation unit and / or the value related to the magnitude of the current signal calculated by the effective value calculation unit; a control unit that controls execution of electrical impedance measurement using the determined measurement conditions; and a storage unit that, when executing the electrical impedance measurement, stores the determined measurement conditions in association with the individual identification information and measurement date and time of the subject,A body composition measuring device having a first measurement mode in which, when the control unit calls up the individual identification information and re-executes the electrical impedance measurement, if the date and time of the re-executed measurement has not elapsed a predetermined time since the date and time of the previous measurement stored in the memory unit, the control unit performs the electrical impedance measurement using the measurement conditions used in the previous measurement stored in the memory unit, and if the date and time of the re-executed measurement has elapsed more than the predetermined time since the date and time of the previous measurement stored in the memory unit, the control unit performs the electrical impedance measurement using the measurement conditions re-determined by the measurement condition determination unit.

2. The body composition measuring device of claim 1, wherein the control unit further has a second measurement mode that continuously performs electrical impedance measurements at predetermined time intervals using the most recent measurement conditions linked to the recalled individual identification information, and controls switching between the first measurement mode and the second measurement mode.

3. A body composition measuring device as described in claim 1 or 2, wherein the control unit further has a third measurement mode in which the measurement condition determination unit sets the measurement conditions each time before performing an electrical impedance measurement, and controls switching between the first measurement mode and the third measurement mode.

4. The body composition measuring device according to claim 1 or 2, wherein the memory unit stores the individual identification information, subject information including information about the subject, the individual identification information, a timestamp recording the date and time of the electrical impedance measurement, and measurement data including the measurement conditions determined when the electrical impedance measurement was performed.

5. A body composition measuring device as described in claim 4, wherein the subject information includes, in addition to the individual identification information, one or more of the subject's name, furigana of the name, height, weight, age, and gender.

6. The body composition measuring device according to claim 4, wherein the measurement data includes the individual identification information, as well as the measurement date and time, measurement conditions, and measurement results of the electrical impedance measurement.

7. The body composition measuring device according to claim 1 or 2, further comprising a time change unit that accepts a change to the predetermined time in the first measurement mode.

8. The body composition measuring device according to claim 7, wherein the time change unit accepts an input from a user regarding the predetermined time.

9. The body composition measuring device according to claim 7, wherein the time change unit allows the user to select the predetermined time from a plurality of time settings prepared in advance.

10. A control method for a body composition measurement device that measures the body composition of a subject in accordance with measurement conditions, the body composition measurement device comprising: a control unit that controls execution of electrical impedance measurement using the determined measurement conditions; and a memory unit that, when executing the electrical impedance measurement, stores the determined measurement conditions in association with the subject's individual identification information and measurement date and time; the control method comprises the steps of: (a) applying a plurality of probe currents of different frequencies to the subject's body, and detecting a voltage signal related to a 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 related to a current flowing through the subject's body; (b) amplifying the voltage signal detected in (a) to a magnitude used for electrical impedance measurement; (c) converting the current signal detected in (a) into a voltage of a magnitude used for electrical impedance measurement; and (d) calculating information related to electrical impedance for each frequency based on the voltage signal amplified in (b) and the current signal converted in (c). The method includes the steps of: (e) calculating an impedance locus based on information about the electrical impedance for each frequency calculated in (d); (f) calculating information about the body composition of the subject based on the impedance locus calculated in (e); (g) calculating a value related to the magnitude of the voltage signal amplified in (b) and / or a value related to the magnitude of the current signal flowing through the body of the subject detected in (a); and (h) determining the changeable measurement conditions of the body composition measuring device based on the value related to the magnitude of the voltage signal and / or the value related to the magnitude of the current signal calculated in (g),The control unit, when calling up the individual identification information and re-executing the electrical impedance measurement, performs the electrical impedance measurement using the measurement conditions used in the previous measurement stored in the memory unit if the date and time of the re-executed measurement has not elapsed a predetermined time since the date and time of the previous measurement stored in the memory unit, and performs the electrical impedance measurement using the measurement conditions determined again in step (h) if the date and time of the re-executed measurement has elapsed a predetermined time since the date and time of the previous measurement stored in the memory unit.

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