JPH10328165A - Respiration monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cancel the physical burden of patient when executing respiratory action monitoring. SOLUTION: In this respiration monitoring device, a sensor unit 1 equipped with a flux gate type magnetic detecting element 6 is attached onto the surface of the waiste of the patient, an AC current for excitation is supplied from an exciting current supply circuit 11 to an exciting coil 8, at the same time, ground magnetic signals detected by reception coils 9a and 9b are sent to a signal extracting part 12, and an electric signal corresponding to the change of ground magnetism received by the reception coils 9a and 9b with the passage of time is outputted as a respiratory waveform signal by this signal extracting part 12. Since the magnetic detecting element 6 is weakly attached and mounted just like being placed on the dullest waist part in the body, the mount of magnetic detecting element 6 can be prevented from giving pains to the patient.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a respiratory monitoring device capable of monitoring a respiratory motion of a subject (patient or the like), and more particularly to a physical monitor of a subject to be monitored when the respiratory motion is monitored. Related to technology for reducing the burden.

[0002]

2. Description of the Related Art In a medical site such as a hospital, a patient's respiratory movement is monitored to monitor the patient's condition. Monitoring of a patient's breathing motion is performed by various methods. First, there is a thermistor-type breathing pickup method in which a thermistor element is attached to a patient's nostril. In this method, the temperature changes in the thermistor element in the same cycle as the breathing as the warm and cold external air alternately touch the thermistor element in the nostril each time the patient breathes. Since the temperature change of the thermistor element causes a change in the resistance value of the thermistor element corresponding to the respiratory operation of the patient, the resistance change is converted into an electric signal by a bridge circuit or the like and displayed to monitor the respiratory operation. To do.

There is also a rubber sheet type respiratory pick-up system in which a conductive rubber sheet is wound around a patient's abdomen and mounted. In the case of this method, as the conductive rubber sheet expands and contracts in accordance with the expansion and contraction of the abdomen of the patient in conjunction with the breathing motion, a change in (electrical) resistance occurs in the conductive rubber sheet. After the resistance change is converted into an electric signal by a bridge circuit or the like, it is displayed and the breathing operation is monitored.

[0004] There is also a mouthpiece-type respiratory pick-up system in which a mouthpiece is attached to a patient's mouth. In this method, a change in the amount of air entering and exiting with a patient's breathing is detected by wearing a mouthpiece, and this is converted into an electric signal and displayed, and the breathing operation is monitored.

[0005]

However, each of the above-mentioned respiratory motion monitoring systems has a problem that the patient suffers from pain. A patient who is constantly wearing a thermistor element or a mouthpiece in the nose or mouth, which has more sensitive nerves in the body, must always feel painful without feeling irritated. In addition, since the conductive rubber sheet wrapped around the abdomen keeps pushing strongly on the abdomen of the patient, the patient is always suffering from a feeling of oppression. In addition, in the case of severely ill patients who require respiratory monitoring very much, the suffering is further increased because wearing parts such as a mouthpiece and a rubber sheet are more apt to be worn due to severe body weakness.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a respiratory monitoring device capable of eliminating a physical load applied to a subject when monitoring a respiratory motion.

[0007]

In order to solve the above-mentioned problems, a respiratory monitoring apparatus according to the present invention is provided with an exciting coil and a receiving coil on a ferromagnetic core so as to correspond to a respiratory motion of a subject. A flux-gate type magnetic detection element mounted on the surface of the body of the subject in which a body motion repeatedly occurs, excitation current supply means for supplying a magnetic core excitation current to an excitation coil of the magnetic detection element, and the magnetic detection element Is provided with a signal extracting means for extracting an electric signal corresponding to a change in the intensity of the geomagnetism caused by displacement with the body movement of the subject from the output of the receiving coil of the magnetic detecting element.

[Operation] Next, the operation of monitoring the respiratory operation by the respiration monitor of the present invention will be described. First, a fluxgate type magnetic sensing element in which an exciting coil and a receiving coil are applied to a ferromagnetic core is moved to a position on the surface of the body of the subject where the body movement corresponding to the respiratory motion of the subject repeatedly occurs. Attach it with a weak mounting method that feels just like placing it. The magnetic sensing element is always worn, but the torso is not as sensitive as the nose and mouth, so it is not bothersome for the patient. Wearing just like placing does not give a feeling of pressure on the torso. This flux gate type magnetic detecting element is an ultra-high sensitivity magnetic sensor capable of sufficiently detecting a very weak magnetic field having a terrestrial magnetic fluctuation level, and can be downsized.

Following the mounting of the magnetic detection element on the body of the subject, the excitation current supply means supplies a magnetic core excitation current to the excitation coil of the magnetic detection element. With the start of the excitation by the excitation coil, the detection of the terrestrial magnetism by the reception coil of the magnetic detection element starts. Then, from the signal extracting means, an electrical signal for respiration monitoring corresponding to a temporal change of geomagnetism received by the receiving coil of the magnetic detecting element is extracted.

[0010] The magnitude of the geomagnetism received by the receiving coil also changes according to the change in the position of the magnetic detecting element accompanying the body movement of the torso caused by the respiration of the subject. In other words, since there is a correlation between the breathing motion and the change in the reception geomagnetism of the receiving coil, the signal extracting means converts the change in the reception geomagnetism due to the change in the position of the magnetic detection element into an electric signal indicating the temporal change in the breathing motion ( (Respiratory waveform signal). As a specific use form of the respiratory waveform signal obtained by the signal extracting means, for example, a mode in which the respiratory waveform signal is constantly displayed on the screen of the display monitor and observed to monitor the patient's condition is exemplified.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the respiratory monitor of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a respiration monitor according to an embodiment;
FIG. 2 and FIG. 3 are graphs showing waveforms of current, voltage and the like of each part in the magnetic detection element of the device of the embodiment.

As shown in FIG. 1, the respiratory monitoring apparatus according to the embodiment has a sensor unit 1 and an excitation / reception unit 2 and a cable 3 for electrically connecting the sensor unit 1 and the excitation / reception unit 2. And a display monitor 4 for displaying a respiratory waveform signal (electric signal) transmitted from the excitation / reception unit 2;
A cable 5 for electrically connecting between the receiving unit 2 and the display monitor 4 is provided. The excitation / reception unit 2 and the display monitor 4 may be configured to be installed near the sensor unit 1. However, the telemetry technology is applied, and both the excitation / reception unit 2 and the display monitor 4 or the display monitor 4 is used. May be installed in a separate room away from the sensor unit 1 and may be configured as a remote monitor, like an electrocardiographic monitor. Hereinafter, the configuration of each unit will be described more specifically.

The sensor unit 1 is provided with one flux gate type magnetic detecting element 6. The magnetic sensing element 6 is a permalloy ring core (ferromagnetic core)
7, one excitation coil 8 and two reception coils 9a,
Reference numeral 9b denotes a wound element. Receiving coil 9a,
The winding 9b has a differential connection winding form so that the electromotive force is in the opposite direction and cancels each other. Each of the ring core 7 and each of the coils 8, 9a, 9b is formed of a thin film, and is formed by repeatedly performing thin film deposition and patterning by photolithography on the surface of the insulating substrate 10. The magnetic detection element 6 is a thin film element. The magnetic detecting element 6 can be a micro-sized element having a chip size of, for example, about 2.5 mm square, and the sensor unit 1 in which the magnetic detecting element 6 is packaged is a compact type having a size of 1 cm or less. It is possible enough.

The excitation / reception unit 2 includes an excitation current supply circuit (excitation current supply means) 11 for supplying a current for exciting the magnetic core to the excitation coil 8 of the magnetic detection element 6, a reception coil 9 a of the magnetic detection element 6, A signal extracting unit (signal extracting means) 12 for extracting an electric signal corresponding to a temporal change of the geomagnetism received by 9b is provided. From the excitation current supply circuit 11 to the excitation coil 8 via the cable 3, several kilohertz
An alternating current of about z to several hundred kHz is supplied as a current for excitation. The excitation current supply circuit 11 includes a frequency oscillation circuit (not shown), a current amplifier circuit (not shown), and the like. The induced voltage generated between both ends of the receiving coils 9a and 9b is input to the signal extracting unit 12 via the cable 3 as a geomagnetic detection signal. The induced voltage of the receiving coils 9a and 9b is similar to that of a known flux gate type magnetic sensor.
This is an AC voltage having a frequency twice the excitation frequency.

As shown in FIG. 1, the signal extracting unit 12 includes a signal amplifying circuit 13 and a resonance circuit 1 for performing necessary processing such as amplification and rectification on the induced voltage signals of the receiving coils 9a and 9b.
4. Synchronous rectification circuit 15, integration circuit 16, low-pass filter 1
7 and a feedback circuit 18, and a double frequency generation circuit 19 for operating the synchronous rectification circuit 15 at a cycle twice the excitation frequency. This double frequency generation circuit 1
Reference numeral 9 denotes a configuration in which an excitation frequency signal is input from the frequency oscillation circuit of the excitation current supply circuit 11 to obtain a signal having a double frequency, and sends the signal to the synchronous rectification circuit 15. In addition, the signal extracting unit 12 is configured so that the amplification (span) can be adjusted by, for example, attaching a circuit for adjusting the amplification using a variable resistor or the like to the signal amplification circuit 13. The feedback circuit 1
Reference numeral 8 denotes a function for improving the linearity between input and output by feeding back a part of the output of the integrating circuit 16 to the input of the signal amplifying circuit 13.

Next, a specific description will be given of the operation of the apparatus when the respiratory monitor is executed by the apparatus having the above-described configuration.

First, as shown in FIG. 4, the sensor unit 1 is mounted in a manner such that the sensor unit 1 is merely placed on the surface of the abdomen of the subject M and has a weak feeling. For example, it is attached by lightly stopping with a medical adhesive tape. The abdomen of the subject M repeats the operation of expanding as shown by the solid line with the breathing and then contracting to the position shown by the dashed line, and the sensor unit 1 also synchronizes with the breathing between the position shown by the solid line and the dashed line. Move up and down. The abdomen of the subject M is not as sharp as the nose or mouth, and the small sensor unit 1 using the thin-film element type magnetic detecting element 6 has almost no feeling of wearing, and is completely unattractive to the patient even if it is always worn. do not become.

After the sensor unit 1 is mounted on the abdomen of the subject M, the excitation current supply circuit 11 supplies the excitation high-frequency current Ia shown in FIG. When the high-frequency current Ia flows through the excitation coil 8,
When the magnetic field to be detected is zero (absent), a trapezoidal magnetic flux φo is generated in the ring core 7 as shown in FIG. 2B, and the induced voltage is generated in the receiving coil 9a as shown in FIG. 2C. Va is generated, and as shown in FIG. 2D, exactly the same induced voltage Vb is generated in the receiving coil 9b except that the polarity is opposite to the induced voltage Va. However, the receiving coil 9a,
2e, the total induced voltage Vc of the receiving coils 9a and 9b of the magnetic sensing element 6 becomes 0, and the signal extracting unit 12 is in a state of zero signal input, as shown in FIG. Will remain.

However, as shown in FIG. 3A, when a high-frequency current Ia is supplied to the excitation coil 8 and a magnetic field to be detected exists, the position of the reception coil 9a in the ring core 7 is changed. At the same time as the magnetic flux φa is generated as shown by the dotted line in FIG. 3 (b), the magnetic flux φb is generated at the receiving coil 9b in the ring core 7 as shown by the dashed line in FIG. 3 (b). Therefore, the receiving coil 9a
3C, an induced voltage VA is generated as shown in FIG. 3C, and the induced voltage Va is generated in the receiving coil 9b as shown in FIG.
The induced voltage VB has a polarity opposite to that of the induced voltage and the phase is shifted according to the degree of the magnetic field to be detected. And the receiving coil 9
a and 9b are differentially connected, so that the total induced voltage VC of the receiving coils 9a and 9b of the magnetic sensing element 6 is as shown in FIG.
As shown in (e), the detection signal is transmitted to the signal extracting unit 12 as a detection signal of T / 2 (double frequency) of a half cycle of the high frequency current Ia for excitation.

In the case of the respiratory monitoring apparatus of the present invention, the geomagnetic field to be detected is always present where the magnetic detecting element 6 is located, but what is ultimately required is not the value of the geomagnetic field itself, but This is a change in geomagnetism due to a change in the position of the magnetic detection element 6 caused by body movement. Therefore, when the magnetic detection element 6 comes to the reference position (for example, the lowest position indicated by the dashed line in FIG. 4), the geomagnetism is just canceled out,
As shown in FIG. 2D, zero point adjustment (offset adjustment) is performed so that the total induced voltage Vc of the receiving coils 9a and 9b of the magnetic detection element 6 becomes zero. More specifically, a DC component corresponding to the terrestrial magnetism cancellation component is superimposed on the AC current supplied to the excitation coil 8. In this case, the total induced voltage itself of the receiving coils 9a and 9b becomes the magnetic sensing element 6
Corresponds to the amount of change in terrestrial magnetism that occurs as the distance from the reference position increases, eliminating the need for a circuit configuration for removing only the amount of change from the total induced voltage of the receiving coils 9a and 9b by removing the amount of bias. Therefore, in the case of the embodiment device, the excitation current supply circuit 11 has a configuration in which a zero-point adjustment circuit (not shown) using a variable resistor or the like is additionally provided.

The total induced voltage of the receiving coils 9a and 9b of the magnetic detecting element 6 shown in FIG. 3 (e) is adjusted to an appropriate level by the signal amplifying circuit 13 and the resonant circuit 14, and rectified by the synchronous rectifying circuit 15. Then, after the integration processing is performed by the integration circuit 16, the excess high-frequency component is removed by the low-pass filter 17.
Finally, an electrical signal as the respiratory waveform signal BS is extracted from the signal extracting unit 12, as shown in FIG. This respiratory waveform signal BS is transmitted to the display monitor 4 via the cable 5. In the graph of FIG. 5, the vertical axis indicates the amount of change in geomagnetism, and the horizontal axis indicates the elapsed time.

The respiratory waveform signal BS is always displayed on the screen of the display monitor 4 to monitor the respiratory motion of the subject (patient) M and monitor the condition of the patient. If the amplitude of the displayed respiratory waveform signal BS is not appropriate, for example, the amplification degree (span) is adjusted by an amplification degree adjusting circuit attached to the signal amplification circuit 13, and the respiratory waveform signal BS is adjusted to an appropriate amplitude. May be displayed.

The present invention is not limited to the above embodiment, but may be modified as follows. (1) In the above embodiment, the respiratory waveform signal BS from the signal extracting unit 12 is displayed on the screen of the display monitor 4 to monitor the patient's condition. Can be used for respiratory synchronization imaging in a nuclear magnetic resonance tomography apparatus. That is, the respiratory waveform signal BS is used as a body motion signal due to the respiration of the subject M, and a reference level is set for the body motion signal. When the body motion signal matches the reference level, the imaging trigger signal is output. It is used so that shooting is performed. With this configuration, respiratory synchronization imaging is realized by the nuclear magnetic resonance tomography apparatus, and it is possible to prevent a tomographic image from being blurred due to respiratory movement.

(2) In the above embodiment, the two receiving coils 9a and 9b of the flux gate type magnetic detecting element 6 are used.
Is operatively connected, but the magnetic sensing element 6
A configuration in which the number of receiving coils is one can also be cited as a modification.

(3) In the above embodiment, the flux gate type magnetic sensing element 6 is a thin film element. However, in the present invention, the flux gate type magnetic sensing element 6 is not necessarily required.
Need not be a thin film element.

(4) In the above embodiment, the sensor unit 1 and the excitation / reception unit 2 are configured separately, but a modified example in which the sensor unit 1 and the excitation / reception unit 2 are integrated is described. Can be

[0027]

As is apparent from the above description, according to the respiratory monitoring apparatus of the present invention, the magnetic sensing element for detecting the respiratory action is attached with a weak feeling such as being placed on the insensitive torso in the body. In addition, since the fluxgate type magnetic sensing element can be downsized, mounting the magnetic sensing element on the subject does not cause pain to the subject, and monitors the respiratory motion. In this case, the physical burden applied to the subject can be eliminated.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a respiration monitoring device according to an embodiment.

FIG. 2 is a graph showing waveforms of current, voltage, and the like of each unit in a magnetic detection element when there is no detection magnetic field.

FIG. 3 is a graph showing waveforms of current, voltage, and the like of each unit in a magnetic detection element when a detection magnetic field is present.

FIG. 4 is a schematic diagram showing a monitoring state of a breathing operation performed by the apparatus according to the embodiment.

FIG. 5 is a graph showing a respiratory waveform signal obtained by the embodiment device.

[Explanation of symbols]

 Reference Signs List 6: flux gate type magnetic detection element 7: ring core 8: excitation coil 9a, 9b: reception coil 11: excitation current supply circuit 12: signal extraction circuit M: subject BS: respiratory waveform signal

Claims (1)

[Claims] An exciter coil and a receiver coil are provided on a ferromagnetic core, and a fluxgate type magnetic detection mounted on a surface of a body of a subject in which body movement corresponding to respiration of the subject repeatedly occurs. An element, excitation current supply means for supplying a current for exciting the magnetic core to an excitation coil of the magnetic detection element, and an element corresponding to a change in the intensity of terrestrial magnetism caused by displacement of the magnetic detection element due to body movement of the subject. Signal retrieving means for retrieving the obtained electric signal from the output of the receiving coil of the magnetic detection element.