JPS63109841A - Multielectrode type living body impedance measuring method and apparatus - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multi-electrode bioelectrical impedance measurement method, in particular a method using a plurality of current application sections including current application electrodes and voltage detection sections including voltage detection electrodes. This invention relates to a bioelectrical impedance measurement method that identifies and separates respiratory information (changes in ventilation volume) and body movement information of a living body by configuring a multi-channel bioelectrical impedance measurement channel consisting of a current applying section and a voltage detecting section.

[Conventional technology]

In addition to impedance pneumographs, pulmonary ventilation function testing devices include spirometers, thermistor-type current meters,
Various devices are used, such as an RI scintigraph.

However, when monitoring the breathing of critically ill patients in ICUs (intensive care units), RCUs (respiratory care units), etc., it is necessary to consider the burden on the patient and the simplicity of the attached device. impedance pneumographs are generally used, which have advantages in these respects.

Changes in the amount of air in the lungs associated with breathing change the electrical conductivity within the lungs, resulting in changes in the electrical impedance of the lungs.

An impedance pneumograph applies a weak, constant high-frequency current between a pair of current-applying electrodes placed on the chest wall, and measures this respiratory impedance change as a voltage change between the voltage-detecting electrodes, capturing changes in ventilation volume. The burden on the examinee is also small.

Impedance measurement is performed by the two-electrode impedance measurement method and the four-electrode impedance measurement method shown in FIGS. 4 and 5. In the conventional impedance pneumograph, a pair of electrodes 3. Several tens of KHz from constant current source 5 between 4 and 10
A current of about 0 μA is applied, and in the case of the two-electrode impedance method, the voltage generated between the same electrodes is measured, and in the case of the four-electrode impedance measurement method, the voltage detection electrode 6 is separately provided to suppress the influence of electrode impedance. The impedance Z of the living body is calculated from the voltage generated between .

[Problem that the invention seeks to solve]

However, in impedance pneumographs using conventional two- or four-electrode impedance measurement methods with one current application section and one voltage detection section, body movements such as the subject moving his arm or changing his posture are being measured. When this occurs, in addition to respiratory impedance changes, there are somatic impedance changes due to large changes in the geometric structure of the lungs and the positional relationship of the electrodes, and therefore, somatic impedance changes are superimposed on respiratory impedance changes. The impedance is measured.

Therefore, it was not possible to identify at what point on the measured impedance change waveform the impedance change due to body movement occurred, and therefore it was difficult to accurately capture only the respiratory information provided by the respiratory impedance change.

An object of the present invention is to solve the problem that it is difficult to accurately capture only necessary respiratory information in such a conventional impedance 221 mograph.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides the following multi-electrode bioelectrical impedance measuring method.

That is, the present invention includes a current applying unit that applies a weak high-frequency current into the living body through the skin surface of the living body, and a voltage that is generated by the applied current and the change in electrical impedance accompanying the breathing action and body movement of the living body. Two sets of channels for bioelectrical impedance measurement are configured, each consisting of a voltage detection unit that detects a change from the skin surface of the living body, and each current application unit of each channel is provided with a current application electrode and a current source,
The voltage detection section of each channel is equipped with a voltage detection electrode and a detection amplifier that amplifies the detected voltage, and among the two sets of channels, the first channel separates the current application electrode from the living body. A constant weak high-frequency current is applied to the living body from a constant current source while the voltage detection electrode of the first channel is placed in close contact with the skin surface and is spaced apart between the electrodes for applying current. The current applying electrode and the voltage detecting electrode of the second channel are arranged in the same manner as the first channel, are separated from the first channel in the upper and lower lung direction, and are generally referred to as the first channel. When viewed from the first channel, the current applying electrode of the second channel is placed in close contact with the skin surface, and a weak current having the same frequency and opposite polarity to the first channel is simultaneously applied to the current applying electrode of the second channel. By forming a negative impedance sensitivity region near the current application electrode of the channel and adjusting the magnitude of the applied current of the second channel, detection during resting breathing can be obtained between the voltage detection electrode pair of the first channel. The applied current of the second channel is set so that the voltage is almost zero, only body movement information is output from this first channel, and the i! A multi-electrode bioelectrical impedance measuring method and apparatus, characterized in that information including respiratory information is output from two channels, and this re-output information is processed by an electrical processing circuit to obtain only pure respiratory information. It is.

[For production]

In the above configuration, impedance changes measured in each channel are classified into those due to respiratory action and those due to other body movements.

These impedance changes are caused by the change in the voltage detection section in response to the applied current of each channel when a constant weak high-frequency current is simultaneously applied from the constant current source of the current application section of each channel through a pair of current electrodes in close contact with the skin surface. It is detected as a change in voltage between the voltage detection electrodes, amplified through the detection amplifier of each channel, and measured.

Here, the reason why the electrical impedance of the living body changes due to the action of breathing is that the electrical conductivity of air is sufficiently low compared to the electrical conductivity of living tissue, and the electrical conductivity in the lungs equivalently changes due to the change in the amount of air in the lungs associated with breathing. The reason why the detection impedance changes due to body movement is that the geometric structure of the lungs and the positional relationship of the electrodes change due to body movement.
This is because the body has changed compared to before the movement.

Impedance sensitivity at a certain point is an index that shows how much weight is given to changes in conductivity at that point due to breathing, etc., and appears as an impedance change between voltage detection electrodes.
A case in which a decrease, or in other words, a decrease or increase in resistivity causes the detected impedance to change in the same direction, is considered positive impedance sensitivity, and a case in which it changes in the opposite direction is considered negative impedance sensitivity.

Therefore, in a state without body movement, the sum of the conductivity at each point associated with breathing, weighted by impedance sensitivity, is measured as a change in bioelectrical impedance, and lung ventilation information can be captured. It is.

As in this configuration, the second channel's current supply is a high-frequency current with the same frequency as the first channel, but it is a weak current with the opposite polarity, in other words, a phase difference of 180 degrees, and the current is supplied to the second channel at the same time as the first channel's current. When viewed from the first channel side, a positive impedance sensitivity area is provided in the area near the current application electrode of the first channel, and a negative impedance sensitivity area is provided in the area near the current application electrode of the second channel. The reason why the second channel's current magnitude is made variable is to change the spread and strength of impedance sensitivity.

Furthermore, when viewed from the second channel, under this configuration, there is a negative impedance sensitivity area in the area near the current applying electrode of the first channel, and a positive impedance sensitive area in the area near the current applying electrode of the second channel. An impedance sensitive region is formed.

When the subject is breathing quietly and the current applied to the second channel is increased in the direction of making it larger than the current applied to the first channel, when viewed from the first channel, The influence of the negative impedance sensitivity distributed near the current application electrode of the second channel becomes relatively strong, and as a result, the conductivity changes in the lungs due to breathing, which are weighted by the positive and negative impedance sensitivities, cancel each other out. , a state in which no respiratory impedance change appears on the first channel, or in other words, a state can be set in which no respiratory information is apparently output to the first channel.

In this setting state, the current value of the second channel is larger than the current value of the first channel, so when viewed from the second channel, the positive voltage distributed near the current applying electrode of the second channel The influence of the impedance sensitivity becomes relatively strong, and the conductivity changes in the lungs weighted by the impedance sensitivity are not canceled out, and respiratory information is output to the second channel.

If you adjust the current of the second channel in advance when the subject is at rest in this way, the output will appear on the first channel only when body movement other than breathing occurs, so the impedance output to the second channel will change. It is possible to know at what point in the change the body movement occurs and the impedance change due to body movement occurs, and from the output of the second channel, only pure respiratory information without body movement impedance change is obtained. be able to.

From this, the body motion information output of the first channel and the second channel
By processing the information output including the breathing information of the channel with the electrical processing circuit, the body movement information is erased, and the desired breathing information can be extracted from the output side of the electrical processing circuit.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Regarding embodiments of the present invention, how the structure of the present invention is actually embodied will be described below with reference to the drawings, together with its operation.

FIG. 1 is a configuration diagram of the present invention, in which 1 is a living body, 1a is an arm,
2 indicates the lungs.

In addition, 3 and 4 form a pair of current applying electrodes, which are in close contact with the skin surface on both sides of the chest wall of the upper lung 2 of the living body 1, and apply a weak high frequency current supplied from a constant current source 5 through this pair of electrodes. and apply it inside the living body 1.

A current applying section A is configured by the current applying electrode 3.4 and the current source 5.

Reference numeral 6.7 denotes a pair of voltage detection electrodes, which are spaced inwardly on the line connecting the current application electrodes 3 and 4 and are in close contact with the skin surface on the chest wall, and the impedance change to be measured is the current application electrode 3.4. Voltage detection electrode 6 for the current applied between
．． The configuration is such that the voltage change between 7 and 7 is output after being amplified via a detection amplifier.

Voltage detection section B is constituted by voltage detection electrodes 6 and 7 and detection amplifier 8.

The current applying section A and the voltage detecting section B constitute a first channel C for impedance measurement.

This channel configuration is clearly illustrated in FIG. 2.

That is, FIG. 2 is a diagram showing the channel configuration of the present invention, and for convenience, the first channel C portion of FIG. 1 is extracted and shown.

The first channel C in the figure is composed of a current applying section A that supplies current and a voltage detecting section B that extracts a voltage.

Of these, the current applying section A consists of a pair of current applying electrodes 3 and 4 and a constant current source 5, and the voltage detecting section B consists of a pair of voltage detecting electrodes 6 and 7 and a detection amplifier 8. Furthermore, the pair of electric recognition applying electrodes 3.4 are provided apart from each other, and the electric current applying electrodes 3.4 which are separated from each other are separated from each other.
This shows that the voltage detection electrodes 6 and 7 are provided spaced apart on the inner side of the line connecting the lines.

In this way, one channel is constituted by the current application section that supplies current and the voltage detection section that extracts voltage.

Next, the current applying electrodes 9 and 10 shown in FIG. 1 are brought into close contact with the upper skin surface of the chest wall on both sides of the lower lung 2, and a weak high frequency current supplied by the constant current 11 is applied into the living body 1 through these electrode pairs.

The current applying electrodes 9 and 10 and the constant current source 11 constitute a current applying section.

A voltage detection electrode 12.13 is closely attached to the skin surface on the inner chest wall on the line connecting these current application electrodes 9 and 10, and the impedance change to be measured is measured by the current application electrode 9.13.
The configuration is such that the voltage change between the voltage detection electrodes 12 and 13 with respect to the current applied to the current is amplified and outputted via the detection amplifier 14.

These voltage detection electrodes 12, 13 and detection amplifier 14 constitute a voltage detection section E.

The current applying section and the voltage detecting section E constitute a first channel F for impedance measurement.

In the above configuration, the first channel C and the second channel F
The arrangement of the electrodes is the same and they are arranged substantially parallel to each other.

The frequency of the current application part A of the first channel C is 50KHz.
, a high frequency constant current of about 100μ8 is applied to the living body 1, and the current application part of the second channel F is connected to the first channel C.
A high-frequency constant current having the same frequency as the high-frequency current with a phase shift of 180 degrees and a variable current value is applied to the living body 1.

Here, the frequency of these applied currents is set to 50 KHz because in the frequency band from several tens of KHz to several hundred KHz, the living body can be considered as a resistor R, and the air change in the lungs due to breathing is equivalent to This is because it can be thought of as a change in electrical conductivity within the lungs.

Further, the applied current value of about 100 μA guarantees safety for living organisms.

When a current is applied to the living body 1 in this way and the channel configuration described above is performed, when viewed from the first channel,
Near the current applying electrode 3.4 of the first channel, there is a so-called positive impedance in which the impedance detected in the first channel changes in an increasing direction as the resistivity increases (decreases in conductivity) at that part. In addition to the sensitivity area, the second
Conversely, near the current applying electrodes 9 and 10 of the channel, there is a first
A so-called negative impedance sensitivity region is formed in which the impedance detected in the channel changes in a decreasing direction.

When viewed from the second channel, on the contrary, there is a negative impedance sensitivity region near the current applying electrode 3.4 of the first channel, and there is a negative impedance sensitive region near the current applying electrode 9 of the second channel.
, 10, a positive impedance sensitivity region is formed.

Under such a configuration, when the current in the current application section of the second channel F is made larger than the applied current in the first channel, the weight is unbalanced due to the positive impedance sensitivity when viewed from the first channel. The component of conductivity change associated with forced breathing decreases, and the component of conductivity change weighted by negative impedance sensitivity increases.

As a result, by setting the applied current to the second channel to an appropriate value, it is possible to set a state in which the influence of changes in the conductivity in the lungs due to breathing is apparently not detected in the first channel.

If the applied current of the second channel is set to such a current value during rest, the output of the first channel will appear only when the body moves.

On the other hand, under this condition, when viewed from the second channel, the current value of the second channel is adjusted to a greater extent than the current value of the first channel, so the conductivity change is weighted by the positive impedance sensitivity. The component of conductivity changes weighted by negative impedance sensitivity increases, and the conductivity changes in the lungs associated with breathing are not lost and are detected by the second channel.

Reference numeral 15 denotes an electrical processing circuit which receives the output of the first channel C and the output of the second channel F as input, and uses the body movement information input from the first channel C to process information input from the second channel F. Of these, the body movement information is deleted and the breathing information is extracted.

FIG. 3 is a schematic diagram of the output signal of the present invention, Δ2. is the first
The output waveform of channel C, ΔZ2, indicates the output waveform of the second channel F.

The interval,T,,T,indicates the case of normal breathing, and Tz,T
A shows the case where breathing is stopped, and T shows the case where the body is moved while breathing is stopped.

In the sections T, , T, respiratory information does not appear in ΔZI on the first channel side, but appears in ΔZ2 on the second channel side and ΔZ3 of the electrical processing circuit, but this is due to the appropriate impedance sensitivity distribution due to the current adjustment. is set, on the first channel side, the conductivity changes in the lungs weighted by the positive and negative impedance sensitivities cancel each other out,
This is because impedance changes due to respiratory effects do not appear, and this shows that the second channel side detects impedance changes due to respiratory effects without losing them under the same current adjustment.

Further, in the sections Tz and Ta, no output appears for either ΔZI+ΔZ2, which indicates that no output appears in a state where there is no body movement and no change in conductivity due to breathing.

Furthermore, in section T, ΔZ1. Outputs also appear for ΔZ2, but this is when body movement occurs under respiratory arrest, indicating that body movement information is clearly highlighted in ΔZl.

Further, the reason why no output appears in ΔZ3 is because the body movement information in ΔZ2 has been erased by the processing circuit 15 using ΔZ.

Based on these facts, we compare and refer to the output ΔZ2 containing respiratory information from the second channel F side and the output ΔZ1 from which body movement information is obtained from the first channel C side, find out at what point the body movement occurred, and perform electrical processing. It can be seen that by using the circuit 15, only highly reliable respiratory information such as ΔZ that does not include body movements can be obtained.

When measuring with this multi-electrode bioelectrode impedance measurement method, each electrode is placed on the skin surface on the chest wall of the living body as shown in Figure 1 above, and the output signal of the first channel in the breathing state at rest is approximately zero. The key point is to adjust the applied current to the second channel so that the respiration information does not appear as an output from the first channel side.

In this way, by adjusting the applied current between the first channel and the second channel one after another at rest and setting the settings, even when measuring over a long period of time, if there is a signal waveform while recording the output on the first channel side, , it turns out that this is a body movement other than breathing information, and it is possible to know which part of the signal waveform output from the second channel side is highly reliable as breathing information. By using this method, only respiratory information can be extracted, providing valuable respiratory information for clinical diagnosis.

Furthermore, the impedance sensitivity distribution that is the basis of the present invention is
Since it can be controlled by the ratio of the applied current on the first channel side and the applied current on the second channel side, it is also possible to perform current adjustment on the first channel side separately from this embodiment.

Furthermore, it is also possible to increase the number of current applying sections and voltage detecting sections and weight the impedance sensitivity distribution.

〔Effect of the invention〕

As described above, according to the present invention, two sets of bioelectrical impedance measurement channels are configured, each consisting of a current applying section and a voltage detecting section, the applied current of the first channel is constant, and the applied current of the second channel is By supplying a current with the same frequency and a different polarity as the applied current of the second channel, and further adjusting the magnitude of the applied current of the second channel appropriately, the output of the first channel can be made into body motion information only, and the output of the second channel can be Information including respiration 1'# yl can be obtained through an electrical processing circuit that electrically compares and processes these two information outputs, making it possible to obtain highly reliable respiration information and accurately and quickly diagnose lung function. can be lowered.

In addition, the burden on the subject in this measurement method is only the wearing of the current application electrode and the voltage detection electrode, and it is easy to use.
It also allows measurements to be performed without causing pain to the patient, is suitable for long-term use, and is suitable for use in ICUs (intensive care units) and RCs.
By using it in the U (respiratory patient treatment room), etc., it has the effect of constantly monitoring the condition of critically ill patients and ensuring thorough treatment.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram of a channel configuration, FIG. 3 is a schematic diagram of an output signal of the present invention, and FIGS. 4 and 5 are diagrams showing a conventional example. It is. 1... Living body, 3.4... Electrode for current application, 5... Constant current source, 6.7... Electrode for voltage detection, 8. ...Detection amplifier, 9.10...Electrode for current application, 11...
・Constant current source, 12, 13...Voltage detection electrode, 14...
...Detection amplifier, 15...Electrical processing circuit, A...Current application section, B...Voltage detection section, C...First channel, D...Current application section, E...Voltage detection section, F...Second channel. Representative Patent Attorney Junya Benmatsu Figure 1 Figure 3

Claims (3)

[Claims] (1) A current applying unit that applies a weak high-frequency current into the living body through the skin surface of the living body, and a voltage change caused by the applied current and changes in electrical impedance due to the breathing action of the living body and body movement. There are two sets of electrical impedance measurement channels each consisting of a voltage detection section that detects from the skin surface of a living body, and the current application section of each channel has a current application electrode and a constant current source. Each of the voltage detection sections is equipped with a voltage detection electrode and a detection amplifier that amplifies the detected voltage, and of the two sets of channels, the first channel is in close contact with the skin surface of the living body with the current application electrode separated. A constant weak high frequency current is applied to the living body from a constant current source, and the voltage detection electrode of the first channel is spaced apart between the electrodes for applying the current and brought into close contact with the skin surface, and the impedance is The current applying electrodes and voltage detecting electrodes of the second channel are arranged in the same manner as the first channel, are separated from the first channel in the upper and lower lung direction, and are placed on the skin approximately parallel to the first channel. When viewed from the first channel, the current application electrode of the second channel is applied with a weak current of the same frequency and opposite in positive and negative polarity to the current application electrode of the second channel. A negative impedance sensitive region is formed near the second electrode.
By adjusting the magnitude of the applied current of the channel, the applied current of the second channel is set so that the detected voltage obtained between the pair of voltage detection electrodes of the first channel during resting breathing is almost zero. The first channel outputs only body movement information, the second channel outputs information including respiratory information, and the information from both outputs is processed by an electrical processing circuit to obtain only pure respiratory information. A multi-electrode bioelectrical impedance measurement method. (2) Two sets of bioimpedance measurement channels consisting of a current application section that applies a weak high-frequency current to the living body and a voltage detection section that detects changes in bioimpedance due to breathing and body movements of the living body as voltage changes; A multi-electrode bioelectrical impedance measurement device equipped with an electrical processing circuit that electrically processes the output of the bioelectrical impedance measurement channel and extracts only the impedance changes due to breathing. (3) Each of the current applying sections includes a pair of current applying electrodes and a constant current source, and each of the voltage detecting sections includes a pair of voltage detecting electrodes and a detection amplifier. The multi-electrode bioelectrical impedance measuring device according to item 2.