JPH0347095B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multi-electrode bioelectrical impedance measuring device, and particularly to a multi-electrode bioelectrical impedance measuring device that uses 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 device that distinguishes and separates breathing 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 neumographs, various devices have been used as conventional lung ventilation function testing devices, including spirometers, thermistor-type flowmeters, and RI scintigraphs.

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 equipment. Possible devices are limited, and impedance neumographs 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 neumograph 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. This also reduces the burden on the subjects.

Impedance measurement is shown in Figures 4 and 5.
This is done using an electrode impedance measuring device and a four-electrode impedance measuring device. Applying a current of about 10KHz and 100μA, and using a two-electrode impedance measurement device,
From the voltage generated between the same electrodes, in the case of a four-electrode impedance measuring device, the impedance Z of the living body is generated from the voltage generated between the voltage detection electrodes 6 and 7, which are separately provided to suppress the influence of electrode impedance. Information on changes in ventilation volume is obtained from the time change ΔZ.

[Problem that the invention seeks to solve]

However, in impedance neumographs using conventional 2- or 4-electrode impedance measurement devices with one current application section and one voltage detection section, body movements such as the subject moving his arm or changing his posture are detected during measurement. When this occurs, in addition to respiratory impedance changes, somatic impedance changes occur due to large changes in the geometric structure of the lungs and the positional relationship of the electrodes, and as a result, somatic impedance changes are superimposed on respiratory impedance changes. Impedance measurements are taken.

Therefore, it is not possible to identify at what point on the measured impedance change waveform an impedance change due to body movement occurs, and it is therefore 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 conventional impedance neumographs.

[Means for solving problems]

In order to achieve the above object, the present invention provides the following multi-electrode bioelectrical impedance measuring device.

In other words, the present invention provides "a current application unit that applies a weak high-frequency current into the living body through the skin surface of the living body, and a current application unit that applies a weak high-frequency current into the living body through the skin surface of the living body, and a current applying unit that applies a weak high-frequency current into the living body through the skin surface of the living body, and The two channels for electrical impedance measurement are composed of a voltage detecting section that detects voltage changes from the skin surface of the living body, and a current applying section of each channel is configured as a current applying electrode. a current source, and each of the voltage detection sections of each channel includes a voltage detection electrode, a detection electrode that amplifies this detection voltage, and a detection amplifier that amplifies this detection voltage, and The applied current of the second channel is kept constant, the applied current of the second channel is supplied with a current having the same frequency and a different polarity as the applied current of the first channel, and further the magnitude of the applied current of the second channel is appropriately adjusted. A multi-electrode device characterized in that the output of the first channel is only body movement information, and the output of the second channel including respiratory information is compared with the output of the first channel to obtain only pure respiratory information. "Bioelectrical Impedance Measurement Device".

"Effect" The impedance changes measured in each channel in the above configuration are classified into those due to respiratory effects and those due to other body movements.

These impedance changes are caused by the change in the voltage detection unit 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 unit 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, and is amplified and measured via the detection amplifier of each channel.

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 change in the amount of air in the lungs associated with breathing equivalently causes the electrical conductivity in the lungs to change. The reason why the detected impedance changes due to body movement is that the geometric structure of the lungs and the positional relationship of the electrodes have changed due to body movement compared to before the body movement. be.

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

Therefore, under conditions without body movement,
The sum of electrical conductivity at each point associated with breathing, weighted by impedance sensitivity, is measured as a change in bioelectrical impedance, and information on ventilation of the lungs is captured.

As in this configuration, the second channel's current supply is a high-frequency current with the same frequency as the first channel, but the positive and negative polarities are opposite, in other words, the phase is different.
When viewed from the first channel side, weak currents different by 180 degrees were applied to the living body at the same time as the current of the first channel. The purpose of this is to provide an impedance sensitivity region near the current applying electrode of the channel, and the reason why the magnitude of the current of the second channel is made variable is to change the spread and intensity of such impedance sensitivity. Intended.

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.

With the subject breathing calmly,
As the applied current of the second channel increases in the direction of making it larger than the applied current of the first channel, when viewed from the first channel, the negative impedance sensitivity distributed near the current applying electrode of the second channel increases. As a result, the conductivity changes in the lungs due to breathing, which are weighted by positive and negative impedance sensitivities, cancel each other out, and a state in which no respiratory impedance changes appear in the first channel is created. In other words, it is possible to set a state in which respiratory information is not output to the first channel in appearance.

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 current value of the second channel is larger than that of the first channel.
The influence of the positive impedance sensitivity distributed near the current application electrode of the channel becomes relatively strong, and the conductivity changes in the lungs weighted by the impedance sensitivity are not canceled out, and respiratory information is not output to the second channel. Ru.

In this way, in advance, while the subject is at rest, the second
If the currents of the channels are matched, an output will appear in the first channel only when a body movement other than breathing occurs, so at what point in the impedance change output to the second channel does the body movement occur and the body movement It is possible to know whether a change in impedance due to the body movement has occurred, and from the output of the second channel, only pure respiratory information without a change in impedance due to a moving body can be obtained.

〔Example〕

Embodiments of the present invention will now be described with reference to the drawings, how the configuration of the present invention is actually embodied, together with its operation.

Figure 1 is a configuration diagram of the present invention, in which 1 is a living body;
A indicates an arm, and 2 indicates a lung.

Further, 3 and 4 form a pair of current applying electrodes,
The upper lungs 2 of the living body 1 are closely attached to the skin on the chest walls on both sides,
A weak high frequency current supplied from a constant current source 5 is applied into the living body 1 via these electrode pairs.

A current applying section A is configured by the current applying electrodes 3 and 4 and the current source 5.

Reference numerals 6 and 7 denote voltage detection electrodes, which are isolated on the inner side on the line connecting the current application electrodes 3 and 4 and are closely attached to the skin surface on the chest wall, and the impedance change to be measured is applied between the current application electrodes 3 and 4. The configuration is such that the voltage change between the voltage detection electrodes 6 and 7 with respect to the current is amplified and output 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.

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 a 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. Further, the pair of current applying electrodes 3 and 4 are provided apart from each other,
It is shown that the voltage detection electrodes 6 and 7 are provided at a distance on the inner side of a line connecting the current application electrodes 3 and 4 which are separated from each other.

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

Next, the current applying electrodes 9 and 10 in FIG.
A weak high-frequency current supplied by a constant current 11 is applied to the inside of the living body 1 through the pair of electrodes, which are placed in close contact with the skin surfaces on the chest walls on both sides.

These current applying electrodes 9, 10 and constant current source 11
The current applying section D is configured by the above.

Voltage detection electrodes 12 and 13 are spaced apart on the skin surface on the inner chest wall on the line connecting these current application electrodes 9 and 10.
are in close contact with each other, and the impedance change to be measured is output after being amplified via the detection amplifier 14 as a voltage change between the voltage detection electrodes 12 and 13 with respect to the current applied to the current application electrodes 9 and 10. It's summery.

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

A second channel F for impedance measurement is established by the current applying section D and the voltage detecting section E.
Configure.

In the above configuration, the electrodes of the first channel C and the second channel F are arranged in the same manner and are arranged substantially parallel to each other.

The current applying part A of the first channel C has the same wave number.
A high frequency constant current of about 50 KHz and 10 μA is applied to the living body 1, and the current applying part D of the second channel F has the same wave number and phase as the high frequency current of the first channel C.
A high-frequency constant current with a 180 degree shift and a variable current value is applied to the living body 1.

Here, the high frequency of these applied currents is set to 50KHz 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.

Furthermore, the applied current value of approximately 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, there is a resistivity in the vicinity of the current application electrodes 3 and 4 of the first channel. In addition to the so-called positive impedance sensitivity region where the impedance detected in the first channel changes in the increasing direction with respect to an increase (inclination of conductivity), there is a region near the current applying electrodes 9 and 10 of the second channel. Conversely, a so-called negative impedance sensitivity region is formed in which the impedance detected by the first channel changes in a decreasing direction in response to an increase in resistivity (decrease in conductivity) at that location.

Conversely, when viewed from the second channel, the first channel
A negative impedance sensitivity region is formed near the current application electrodes 3 and 4 of the channel, and a positive impedance sensitivity region is formed near the current application electrodes 9 and 10 of the second channel.

Under such a configuration, when the current in the current applying part D of the second channel F is made larger than the applied current of the first channel, the current is increased due to the positive impedance sensitivity when viewed from the first channel. The component of conductivity change weighted by 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 up a state in which the influence of changes in electrical 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 conduction is weighted by the positive impedance sensitivity. The component of rate change increases, the component of conductivity change weighted by negative impedance sensitivity decreases, and conductivity changes in the lungs associated with breathing are not lost and can be detected in the second channel. be done.

FIG. 3 is a schematic diagram of the output signal of the present invention, where ΔZ ₁ is the output waveform of the first channel C, and ΔZ ₂ is the output waveform of the second channel C.
The output waveform of channel F is shown.

The intervals, T ₁ and T ₅ indicate the case of normal breathing, and T ₂ ,
T ₄ indicates a case where breathing is stopped, and T _s indicates a case where body movement is carried out while breathing is stopped.

In the sections T ₁ and T ₅ , respiratory information does not appear in ΔZ ₁ on the first channel side, but appears only on ΔZ ₂ on the second channel side, but this is because an appropriate impedance sensitivity distribution is created by the current adjustment. This is because, on the first channel side, the conductivity changes in the lungs weighted by the positive and negative impedance sensitivities cancel each other out, and impedance changes due to respiratory action do not appear. This shows that the same current adjustment allows detection of impedance changes due to breathing without loss.

Further, in the sections T ₂ and T ₄ , no output appears in either ΔZ ₁ or ΔZ ₂ , 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 _s , outputs appear for both ΔZ ₁ and ΔZ ₂ , but this is when body movement occurs under respiratory arrest, and body movement information is clearly highlighted in ΔZ ₁ . It shows.

From these facts, by comparing and referencing the output ΔZ ₂ containing respiratory information from the second channel F side and the output ΔZ ₁ from which body movement information is obtained from the first channel C side, it is possible to determine at what point body movement occurred. It can be seen that only highly reliable breathing information that does not include body movements can be obtained.

When measuring with this multi-electrode bioelectrode impedance measuring device, each electrode is placed on the skin surface of 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 following occurs, and to prevent respiratory information from apparently appearing as an output from the first channel.

By adjusting the applied current between the first channel and the second channel in a resting state and setting it in advance, it is possible to prevent signal waveforms from occurring during output recording on the first channel side even during long-term measurements. For example, it can be determined that this is body movement other than respiratory information, and it can be used to know which part of the signal waveform output from the second channel is highly reliable as respiratory information, which is valuable for clinical diagnosis. It can provide accurate breathing information.

In addition, the impedance sensitivity distribution, which is the basis of the present invention, can be controlled by the ratio of the applied current on the first channel side to the applied current on the second channel side. It is also possible to make adjustments.

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 different polarity as the applied current in the second channel and appropriately adjusting the magnitude of the applied current in the second channel, the first channel outputs only body movement information, and the second channel outputs respiratory information. By comparing the included output with the output of this first channel, highly reliable respiratory information can be obtained, and an accurate diagnosis of lung function can be made.

In addition, the burden placed on the subject with this measuring device is only the current applying electrode and voltage detecting electrode, making it possible to perform measurements easily and without causing pain to the subject, and it can be used for long periods of time. is also suitable,
ICU (intensive care unit) and RCU (respiratory patient care unit)
By using this system, it is possible to constantly monitor the condition of critically ill patients and ensure thorough treatment.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of one embodiment of the present invention, and FIG.
3 is a schematic diagram of the output power signal of the present invention, and FIGS. 4 and 5 are diagrams showing a conventional example. 1... Living body, 3, 4... Electrode for current application, 5...
...Constant current source, 6,7... Voltage detection electrode, 8...
Detection amplifier, 9, 10...Electrode for current application, 1
1... Constant current source, 12, 13... Voltage detection electrode, 14... Detection amplifier, A... Current application section,
B... Voltage detection section, C... First channel, D...
...Current application section, E...Voltage detection section, F...Second channel.

Claims (1)

[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 that occurs due to the applied current and the change in electrical impedance accompanying the breathing action of the living body and body movement. There are two first channels and a second channel for measuring electrical impedance, each consisting of a voltage detecting section for detecting from the skin surface of a living body, and a current applying section of each channel, each including a current applying electrode and a constant current source. The voltage detecting section of each channel includes a voltage detecting electrode, a detecting electrode for amplifying the detected voltage, and a detecting amplifier for amplifying the detected voltage, and the voltage detecting section for each channel is configured to control the applied current of the first channel. constant, and the applied current of the second channel has the first
By supplying a current with the same frequency and different polarity as the current applied to the channel, and by appropriately adjusting the magnitude of the applied current to the second channel, the output of the first channel is limited to body movement information, and the output of the second channel is controlled by breathing information. A multi-electrode bioelectrical impedance measuring device characterized in that only pure respiratory information is obtained by comparing and referencing an output containing information with the output of the first channel.