WO2021066004A1

WO2021066004A1 - Cardiac output measurement device

Info

Publication number: WO2021066004A1
Application number: PCT/JP2020/037133
Authority: WO
Inventors: 圭本田; 信一郎須田; 筱薇呂
Original assignee: テルモ株式会社
Priority date: 2019-09-30
Filing date: 2020-09-30
Publication date: 2021-04-08
Also published as: JPWO2021066004A1

Abstract

[Problem] To enable accurate measurement of both the cardiac output and the breathing state of a subject. [Solution] The present invention has a cardiac waveform measurement unit 112 that measures the waveform of microwaves passing through an organism, a breathing number calculation unit 114 that measures the waveform when the organism is breathing or the waveform when the organism is not breathing, and a cardiac output calculation unit 116 that uses the waveform during breathing or the waveform during not breathing to calculate a waveform for obtaining the cardiac output of the organism and the waveform when the organism is breathing from the waveform of the microwaves.

Description

Cardiac output measuring device

The present invention relates to a cardiac output measuring device capable of accurately measuring both the cardiac output and the respiratory state of a subject.

In order to know whether the subject's heart is functioning normally, it is important to measure the cardiac output, which indicates how much blood is being pumped from the heart.

Examination of heart failure, follow-up after heart surgery, verification of medication effect of heart disease, etc. can be performed by measuring cardiac output. As a device for measuring cardiac output, for example, as shown in Patent Document 1 and Patent Document 2, there are various devices.

Japanese Unexamined Patent Publication No. 2016-20516 International Publication 2018/194093

However, since the measurement of cardiac output is usually performed while the subject is breathing, the effect of respiration cannot be ignored for accurate measurement of cardiac output. Also, when measuring cardiac output, if the relative positions of the antenna that irradiates the microwave, the antenna that receives the microwave that has passed through the subject, and the subject's heart are not appropriate, the heartbeat will be accurate. The output cannot be measured. In addition, in order to grasp the condition of the subject more accurately, it is important to evaluate both the cardiac output and the respiratory state, but as described above, the cardiac output and the respiratory signal are mixed. Because it is easy to do, it is difficult to accurately measure the respiratory status, much less both cardiac output and respiratory status.

An object of the present invention is to provide a cardiac output measuring device capable of accurately measuring both the cardiac output and the respiratory state of a subject.

The cardiac output measuring device of the present invention for achieving the above object has a first measuring means, a second measuring means, and a calculating means.

The first measuring means measures the waveform of microwaves that have passed through the living body. The second measuring means measures the waveform of the living body during respiration or the waveform during apnea. The calculation means calculates the waveform of the living body during respiration and the waveform for obtaining the heart rate output of the living body from the waveform of the microwave using the waveform during respiration or the waveform during apnea.

According to the present invention, since both the cardiac output and the respiratory state of the subject can be accurately measured, a more appropriate medical index can be obtained.

It is a block diagram of the cardiac output measuring device of this embodiment. It is a figure which shows the waveform of the microwave measured by the heart rate waveform measuring part. It is a figure which shows the waveform after applying the filter which matches the frequency of the waveform at the time of respiration. It is a figure which shows the heartbeat waveform after applying the filter which matches the frequency of the apnea component waveform. It is a figure which shows the waveform at the time of breathing or apnea measured by the respiratory rate calculation part. It is a perspective view of the positioning apparatus of this embodiment. It is a side view of the positioning device of FIG. It is a front view of the positioning device of FIG. It is an operation flowchart of the positioning device of FIG. It is a figure which provides the operation description of the positioning apparatus of FIG. It is an operation flowchart for calculating the cardiac output by the cardiac output measuring device of this embodiment. It is a figure which shows the waveform (respiratory component waveform + apnea component waveform) of the microwave measured by the heart rate waveform measuring unit. It is a figure which provides the explanation of the method which the frequency calculation part calculates the frequency of the respiratory component waveform. It is a figure which provides the explanation of the method which the frequency calculation part calculates the frequency of the apnea component waveform. It is a figure which shows an example of the heartbeat waveform after molding (the waveform which obtains the cardiac output) used by the cardiac output calculation part for calculating the cardiac output.

An embodiment of the cardiac output measuring device of the present invention will be described below.

(Configuration of cardiac output measuring device)
FIG. 1 is a block diagram of the cardiac output measuring device of the present embodiment. FIG. 2A is a diagram showing a microwave waveform measured by the heartbeat waveform measuring unit. The cardiac output measuring device 100 includes a control unit 110, a transmitting unit 122, a receiving unit 128, a measurement start switch 140, a notification unit 152, a display unit 154, and an input unit 160. Further, a transmitting antenna 124, a receiving antenna 126, and a positioning device 200 are connected to the cardiac output measuring device 100.

The control unit 110 uses the waveform of the microwave transmitted through the chest of the subject (living body) received by the receiving unit 128 to obtain the cardiac output of the subject, in other words, the heart of the subject. Calculate the amount of blood (liters / minute) pumped from the left ventricle per unit time.

When microwaves pass through the subject's heart, the blood absorbs the microwaves, so the diastole, when blood flows into the heart, is more pronounced than the systole, when blood is drained from the heart. The waveform is attenuated. Cardiac output can be calculated from the amplitude of the microwave waveform that is attenuated by changes in blood. This microwave cardiac output measurement has the advantage that the cardiac output can be measured non-invasively and non-invasively, and that the device can be miniaturized. The measuring device is non-invasive and small in size for heart failure medical treatment, follow-up after heart surgery, verification of medication effect for heart disease, etc., and it is possible to measure cardiac output anytime, anywhere, any number of times. It is important to be. Therefore, it is very important to accurately calculate the attenuation of the microwave waveform so that the cardiac output can be calculated accurately.

When measuring the cardiac output of a subject, microwaves are emitted toward the subject's heart, so the waveform of the microwave that has passed through the human body is the respiratory change and cardiac output of the subject. Since each volume change is included, the cardiac output calculation cannot ignore the effects of respiration. The subject takes various breaths such as shallow breathing, deep breathing, slow breathing, fast breathing, regular breathing, and irregular breathing depending on the measurement environment and condition. Since the relative position of the transmitting antenna and the receiving antenna installed on the body surface of the chest changes with each respiration, respiration hinders the accurate calculation of the attenuation of the microwave waveform. In addition, since microwaves are also absorbed by the lungs, changes in lung capacity due to respiration also hinder the accurate calculation of the attenuation of the microwave waveform. The control unit 110 removes the influence of the subject's respiration and accurately calculates the amount of attenuation of the microwave waveform. The control unit 110 includes various components for accurately calculating the attenuation amount of the microwave waveform, which will be described later.

The control unit 110 uses the waveform of the microwave transmitted through the chest of the subject (living body) received by the receiving unit 128 to determine the respiratory state of the subject, in other words, per unit time of the subject. Calculate the number of breaths performed (times / minute).

When microwaves pass through the lungs of a subject, the microwaves are absorbed by the tissues and blood of the lungs, the air taken into the lungs, and the liquid components that have exuded into the alveoli. Since the amount of air taken into the lungs and the amount of circulating blood in the lungs change with breathing, the amount of microwaves absorbed changes depending on the respiratory state (inhaling and exhaling). Therefore, for example, the respiratory rate can be calculated from the frequency of the microwave waveform as an index showing the respiratory state of the subject.

When trying to measure the respiratory rate using microwaves, the positional relationship between the transmission path of microwaves inside the living body and lung tissue, and the transmitting antenna and receiving antenna installed on the outer surface of the body surface are caused by breathing. The waveform pattern and amplitude intensity of microwaves also change as the positional relationship changes. In addition, since the lungs and the heart are located close to each other, the waveform changes derived from respiration are mixed with the waveform changes derived from heartbeat. Therefore, it is difficult to accurately calculate the respiratory state from the change in the waveform of the microwave. The control unit 110 removes the influence of the apnea component such as the heartbeat of the subject, and accurately calculates the amount of change and the frequency derived from the respiration of the microwave waveform. The control unit 110 includes various components for accurately calculating the amount of change and the frequency derived from the respiration of the microwave waveform, which will be described later.

Since the heart and lungs are located close to each other, when trying to accurately measure both the heart rate output and the respiratory state by changing the waveform of the microwave, the waveform change derived from the heartbeat and the waveform change derived from the respiration Will be observed for the combined waveform change. At this time, in order to acquire both the heartbeat component and the respiratory component with a good signal-to-noise ratio, it is necessary to align the transmitting antenna 124 and the receiving antenna 126 at appropriate positions. The positioning device 200 and the drive unit 119 include various components for accurately positioning the transmitting antenna 124 and the receiving antenna 126 at appropriate positions, which will be described later.

Especially in heart failure medical care, it is important to understand both cardiac output and respiratory rate. Cardiac output is one of the best indicators of the ejection status of the heart, and the severity of heart failure itself, the degree of recovery after exacerbation, the estimation of the maximum dose of drugs such as diuretics, and discharge from the hospital. It can be used to judge the pros and cons of. Respiratory rate is one of the best indicators of the signs and symptoms of exacerbation of heart failure, and is characterized by difficulty in breathing during exacerbation and normal breathing during recovery. It is also a vital that changes compensatory when cardiac function and general condition deteriorate. Therefore, it is very important in heart failure medical care to be able to accurately measure both cardiac output and respiratory rate.

The transmission unit 122 receives an instruction from the control unit 110 and transmits a signal for irradiating a microwave of a predetermined frequency from the transmission antenna 124. As the frequency of the microwave, it is preferable to set the frequency at which the waveform for obtaining the cardiac output and the respiratory rate can be obtained most clearly. In this embodiment, microwaves having a frequency of 0.4 GHz to 1.00 GHz are used.

The receiving unit 128 amplifies the microwave signal received by the receiving antenna 126. The subject's chest is located between the transmitting antenna 124 and the receiving antenna 126. The transmitting antenna 124 is arranged on either the back side or the chest side of the subject, and the receiving antenna 126 is arranged on the chest side or the back side of the subject, facing the transmitting antenna 124. The transmitting antenna 124 and the receiving antenna 126 may be arranged in close contact with the body surface of the subject, or may be arranged at a certain distance from the body surface of the subject. In the present embodiment, the transmitting antenna 124 and the receiving antenna 126 are arranged at a certain distance from the body surface of the subject, and the phase positions of the transmitting antenna 124 and the receiving antenna 126 with respect to the subject are adjusted by the positioning device 200. Will be done. The receiving antenna 126 receives a microwave having a received waveform as shown in FIG. 2A, for example, which is irradiated from the transmitting antenna 124 and transmitted through the chest of the subject. The subject is exposed to microwaves while breathing. Therefore, in the received waveform of the microwave in FIG. 2A, the respiratory component waveform including the respiratory information obtained when the subject is breathing (when the chest is up and down) and the pure heartbeat It contains both waveforms and the waveform of the apneic component that contains only the information of.

The measurement start switch 140 is configured so that a user such as a medical worker such as a doctor or a nurse can instruct the start of measurement of cardiac output and respiratory rate. The specific mode of the measurement start switch 140 is not particularly limited as long as it is a switch that can be switched on and off. For example, a toggle type or button type mechanical switch or an electronic switch displayed on the display screen can be mentioned.

The notification unit 152 notifies a message indicating the start of measurement or the end of measurement. The notification unit 152 may notify a message indicating the start of measurement or the end of measurement by sound or light, or may display characters on the screen to notify the notification.

The display unit 154 displays various waveforms calculated by the control unit 110, and the calculated cardiac output and respiratory rate. The display unit 154 is a display using a liquid crystal or an organic EL.

The input unit 160 allows a user such as a medical worker to input information about the subject (sex, age, name, height, weight, etc. of the subject) to the control unit 110 and input measurement contents. It is configured as follows. The input unit 160 can be configured by any one of pointing devices such as a push button, a keyboard, and a mouse, or a combination thereof in whole or in part. In the present embodiment, the input unit 160 is provided in the cardiac output measuring device 100, but the cardiac output measuring device 100 may be externally attached.

The external terminal 170 is configured to be able to communicate with the cardiac output measuring device 100 via the communication unit 118. The external terminal 170 is composed of a known tablet, personal computer, or the like.

The control unit 110 includes a heart rate waveform measurement unit 112, a respiratory rate calculation unit 114, a frequency calculation unit 115, a cardiac output calculation unit 116, a storage unit 117, a communication unit 118, and a drive unit 119. The heart rate waveform measurement unit 112, the respiratory rate calculation unit 114, the frequency calculation unit 115, the cardiac output calculation unit 116, and the drive unit 119 are configured in the processor 111.

FIG. 2A is a diagram showing a microwave waveform measured by the heart rate waveform measuring unit 112. The heart rate waveform measuring unit 112 functions as a measuring means for measuring the waveform of the microwave transmitted through the subject.

The heartbeat waveform measuring unit 112 is composed of a composite waveform of a respiratory component waveform including respiratory information and an apnea component waveform including heartbeat information, as shown in FIG. 2A, from microwaves transmitted through the subject. Measure the waveform of the microwave. In the example of FIG. 2A, the frequency of the respiratory component waveform is lower than that of the apnea component waveform, the overall shape of the synthetic waveform is obtained from the respiratory component waveform, and the apnea component waveform appears as fine irregularities. In the example of FIG. 2A, the main component of the apnea component waveform includes a change in the microwave waveform due to the inflow and outflow of blood into the heart due to the beating of the heart. The heart rate waveform measuring unit 112 measures the received waveform of the microwave as shown in FIG. 2A amplified by the receiving unit 128. This microwave waveform includes the respiratory component waveform when the subject is breathing and the apnea component waveform when not breathing, but strictly speaking, the respiratory component waveform also includes the apnea component waveform. It has been.

FIG. 2B is a diagram showing a waveform after filtering to match the frequency of the respiratory component waveform. FIG. 2C is a diagram showing a heartbeat waveform after filtering to match the frequency of the apnea component waveform. The frequency calculation unit 115 and the cardiac output calculation unit 116 function as calculation means for calculating the waveform for obtaining the cardiac output by numerically analyzing the waveform of the microwave.

The frequency calculation unit 115 calculates the frequencies of the respiration component waveform and the apnea component waveform of the microwave reception waveform as shown in FIG. 2A, which are measured by the heart rate waveform measurement unit 112. The respiratory rate calculation unit 114 and the frequency calculation unit 115 calculate the frequency of the respiratory component waveform, that is, the respiratory rate from the number of inflection points of the respiratory component waveform appearing within a unit time in the received microwave waveform. Further, the frequency calculation unit 115 is caused by the frequency of the apnea component waveform, that is, the change in the waveform of the microwave due to the inflow and discharge of blood into the heart, depending on the number of bending points of the apnea component waveform appearing within a unit time. Calculate the frequency of the heartbeat. The method of calculating the frequency of the respiratory component waveform and the apnea component waveform performed by the frequency calculation unit 115 will be described in detail later.

The cardiac output calculation unit 116 forms a heartbeat waveform using the frequencies of the respiratory component waveform and the aspiratory component waveform in the microwave waveform calculated by the frequency calculation unit 115, and the cardiac output as shown in FIG. 2C. Calculate the cardiac output from the waveform for which the amount is calculated. A general known method is used to calculate the cardiac output. The cardiac output calculation unit 116 generates a filter that matches the frequency of the respiratory component waveform included in the heartbeat waveform when forming the heartbeat waveform as shown in FIGS. 2B and 2C. The specific method of generating the filter will be described later. When the heartbeat waveform is formed by applying a filter matching the frequency of the respiratory component waveform generated by the heart rate output calculation unit 116 to the microwave waveform as shown in FIG. 2A, the respiratory waveform component as shown in FIG. 2B is formed. A heartbeat waveform is obtained in which is removed to some extent. In addition, the cardiac output calculation unit 116 generates a filter that matches the frequency of the apnea component waveform, that is, the frequency of the waveform component caused by the beating of the heart, when forming the heartbeat waveform. The specific method of generating the filter will be described later. A filter suitable for the microwave reception waveform as shown in FIG. 2A, the heartbeat waveform as shown in FIG. 2B, and the frequency of the waveform component caused by the heartbeat generated by the cardiac output calculation unit 116 is applied. Call. As a result, a waveform for obtaining the cardiac output as shown in FIG. 2C, specifically, a waveform in which the amplitude for obtaining the cardiac output is accurately reproduced can be obtained. The cardiac output calculation unit 116 calculates the amount of blood delivered by the subject's heart per unit time, that is, the cardiac output from the waveform for obtaining the cardiac output in FIG. 2C. The cardiac output can be calculated from any of the amplitude changes in FIGS. 2B and 2C. Further, it is better to use the heartbeat waveform as shown in FIG. 2C, which is filtered by both the filter that matches the frequency of the respiratory component waveform and the filter that matches the frequency of the apnea component waveform (heartbeat). It can be calculated accurately. In this embodiment, after applying a filter that matches the frequency of the respiratory component waveform, a filter that matches the frequency of the apnea component waveform (heartbeat) is applied, but a filter that matches the frequency of the heartbeat is used. After applying, a filter suitable for the frequency of respiration may be applied. In addition, when calculating the respiratory rate and heart rate output, after applying a general high frequency filter to remove noise originating from the living body, filtering that matches the frequency of the respiratory component waveform and the apnea component waveform Filtering may be performed to match the frequency of (heartbeat).

The storage unit 117 calculates a filter coefficient for generating a filter that matches the frequency of the respiratory component waveform included in the microwave reception waveform and a filter that matches the frequency of the aspiratory component waveform included in the microwave reception waveform. Memorize expressions and filters. Each of the respiratory rate calculation unit 114 and the cardiac output calculation unit 116 stores in the storage unit 117 a filter that matches the frequency of the respiration waveform and the frequency of the apnea component waveform as shown in FIG. 2A. Generated from the filter coefficient calculation formula and the filter. Examples of the filter include a digital filter such as a low-pass filter or a band-pass filter.

Therefore, the heart rate output calculation unit 116 uses the frequencies of the apnea component waveform and the waveform during respiration calculated by the frequency calculation unit 115 to use the filter coefficient calculation formula and filter stored in the storage unit 117. It is used to generate a filter that matches the frequency of the waveform during respiration and a filter that matches the frequency of the apneic component waveform contained in the heartbeat waveform.

Therefore, the respiratory rate calculation unit 114 uses the frequency of the respiratory waveform calculated by the frequency calculation unit 115, and uses the filter coefficient calculation formula or filter stored in the storage unit 117 to generate the respiratory waveform. Generate a filter that matches the frequency of.

An acceleration sensor 130 attached to the body surface of the subject is connected to the heart rate waveform measuring unit 112. The accelerometer 130 is used to acquire the frequency of the waveform during respiration, that is, the respiration rate, independently of the respiration rate calculation unit 114. The acceleration sensor 130 is attached to the chest of the subject and detects the vertical movement of the chest of the subject when the subject is breathing as a positional displacement. In FIG. 2D, when the waveform is rising, the subject is inhaling, when it is falling, the subject is exhaling, and near the top and valley of the waveform are being examined. It is when the person is holding his breath. The waveforms when the subject is inhaling and exhaling are the waveforms during breathing, and the waveforms when the subject is holding his breath are the waveforms during apnea. In the present embodiment, the acceleration sensor 130 is illustrated as a means for detecting the vertical movement of the chest of the subject as a position displacement, but if the position displacement can be detected, the position is determined from the pressure of, for example, a pressure sensor. A ranging sensor such as a sensor that detects displacement or a laser sensor that detects displacement from a distance may be used. In addition, when using an accelerometer, the configuration is such that when the waveform is descending, the subject is inhaling, and when the waveform is rising, the subject is exhaling. Good.

The respiratory rate calculation unit 114 and the accelerometer 130 are used independently to acquire the frequency (respiratory rate) of the waveform during respiration, and the acquisition results are used cooperatively. That is, of the respective acquisition results, the result that can be measured stably may be preferentially used, or the respiration finally obtained by using the other acquisition result in the analysis process of one acquisition result. You may want to improve the accuracy of the numbers. Further, the average value of each acquisition result may be used as the final acquisition result.

In this way, as a method of calculating the respiratory rate, not only the respiratory rate calculation unit 114 but also the acceleration sensor 130 is provided because of the following circumstances. The subject takes various breaths such as shallow breathing, deep breathing, slow breathing, fast breathing, regular breathing, and irregular breathing depending on the measurement environment and condition. In addition, the waveform component derived from the heartbeat mixed in the respiratory waveform may also differ greatly depending on the condition. The generally used waveform forming method is based on the premise that the waveform to be formed is almost the same waveform without being affected by the environment or the like. However, the frequency of the subject's respiration and heartbeat usually changes greatly depending on the environment and condition. As described above, in order to accurately obtain the respiratory rate from the waveform in which the frequency and the pattern may change significantly, it is necessary to provide not only the respiratory rate calculation unit 114 but also the acceleration sensor 130.

As a method of calculating the respiratory rate, not only the respiratory rate calculation unit 114 but also the acceleration sensor 130 is provided because of the following circumstances. Accurately calculating cardiac output is more difficult than accurately calculating respiratory rate. For example, when the received microwave waveform as shown in FIG. 2A is obtained, the amplitude intensity of the respiratory component waveform and the apnea component waveform including the heartbeat information is compared, and the respiratory component waveform is larger and detected. Cheap. In addition, when calculating the respiratory rate, it is sufficient to know the frequency of the respiratory component waveform, so if the amplitude is clearly obtained, the respiratory rate should be calculated even if the waveform shape has a slight increase or decrease in amplitude intensity. Is possible. On the other hand, in the calculation of cardiac output, the amplitude intensity itself directly affects the calculation result, so that the amplitude intensity needs to be stable in the waveform shape derived from the heartbeat. In view of the difference in the difficulty of calculating the respiratory rate and the cardiac output, when positioning the transmitting antenna 124 and the receiving antenna 126, a place where both the respiratory component waveform and the cardiac output waveform can be clearly observed. The primary goal is to install an antenna, but if the optimal installation positions for the respiratory component waveform and heartbeat component waveform are different, priority is given to cardiac output measurement, which makes it difficult to calculate accurate values. The antenna will be installed in a place where the heartbeat component waveform can be accurately observed. In order to accurately calculate the respiratory rate even in such a situation, the acceleration sensor 130 is provided for the purpose of supplementing the respiratory rate measurement by the respiratory rate calculation unit 114.

As shown in FIG. 2A, the drive unit 119 has both a respiration component waveform including respiration information and an apnea component waveform including respiration information in the microwave reception waveform measured by the heart rate waveform measurement unit 112. Install the antenna in a place where you can clearly observe. As a typical procedure of the installation method, the positioning device 200 is driven so that the amplitude of the waveform for obtaining the cardiac output as shown in FIG. 2C calculated by the cardiac output calculation unit 116 is maximized, and the transmitting antenna is transmitted. The relative positions of 124 and the receiving antenna 126 are changed. Then, the relative positions of the transmitting antenna 124 and the receiving antenna 126 are finely adjusted so that the respiratory component waveform can be observed more clearly at that position. The drive unit 119 drives the positioning device 200 so that the amplitude of the apnea component waveform as shown in FIG. 2A is maximized instead of the amplitude of the waveform for obtaining the cardiac output as shown in FIG. 2C. You may.

The above is the configuration of the cardiac output measuring device 100. Next, before explaining the operation of the cardiac output measuring device 100, the configuration and operation of the positioning device 200 will be described.

(Configuration and operation of positioning device)
FIG. 3 is a perspective view of the positioning device of the present embodiment. FIG. 4 is a side view of the positioning device of FIG. FIG. 5 is a front view of the positioning device of FIG.

The positioning device 200 has a moving portion 121 that can move between the head and abdomen of the subject P along the body of the subject P in the Y direction shown in the drawing, and a moving portion 121 that moves the body of the subject P to the moving portion 121. It has a sleeper 127 that can move in the X and Z directions that are orthogonal to the moving direction. The moving portion 121 includes a housing 123 having a C-shape so as to surround a part of the body of the subject P, and a driving mechanism 125 for moving the housing 123. A receiving antenna 126 for receiving microwaves is attached to the upper side of the housing 123, and a transmitting antenna 124 for irradiating microwaves is attached to the lower side thereof. The housing 123 is positioned so that the transmitting antenna 124 and the receiving antenna 126 sandwich the chest of the subject P.

The sleeper 127 is movably installed on the pedestal 129 installed on the floor. The sleeper 127 positions the subject P so that the transmitting antenna 124 and the receiving antenna 126 sandwich the chest of the subject P. The sleeper 127 is moved by the drive mechanism 125 in the same manner as the housing 123. Inside the drive mechanism 125, a motor, a rack mechanism, and the like for moving each of the housing 123 and the sleeper 127 are provided. The motor of the drive mechanism 125 operates according to a command from the drive unit 119 of the control unit 110 of the cardiac output measuring device 100.

In the present embodiment, the housing 123 and the sleeper 127 are moved respectively, but in addition to this, for example, the housing 123 is fixed and only the sleeper 127 is moved in the X, Y, and Z directions. The sleeper 127 may be fixed and only the housing 123 may be moved in the X, Y, and Z directions. Further, the sleeper 127 may be configured not to be parallel to the ground. Instead, it may be equipped with an angle adjusting mechanism that can be fixed in a state of having an angle. In this case, the drive unit 119 may be equipped with a mechanism for adjusting the angle of the housing 123 so that the sleeper 127 and the transmitting antenna 124 are parallel to each other. With such a configuration, when the sleeper 127 is parallel to the ground, even if the subject P experiences symptoms or discomfort during the measurement, there is no problem in the heart such as cardiac output. The relevant index can be measured. For example, in the case of acute exacerbation of heart failure, it becomes possible to measure the subject P without causing respiratory distress. In addition, accurate measurement is possible even for the subject P whose position is restricted due to contracture or spasticity of the surgical site or body.

Next, the operation of the positioning device 200 will be briefly described. FIG. 6 is an operation flowchart of the positioning device of FIG. The description of this operation flowchart will be described with reference to FIG. 7. Note that FIG. 7 is a diagram provided for explaining the operation of the positioning device of FIG.

First, the subject P is laid down on the sleeper 127, the subject P is prevented from moving, and the sleeper 127 is moved in the X and Z directions by the drive mechanism 125 to adjust the rough position of the subject P. Next, the housing 123 is moved in the Y direction by the drive mechanism 125 to move the transmitting antenna 124 and the receiving antenna 126 so that the positions of the transmitting antenna 124 and the receiving antenna 126 sandwich the heart of the subject P. (S10).

In this state, the transmitting antenna 124 irradiates the subject P with microwaves (S11). The receiving antenna 126 receives the microwave transmitted through the subject P (S12). The heartbeat waveform measuring unit 112 shown in FIG. 1 measures the received waveform of the microwave as shown in FIG. 2A received by the receiving antenna 126 via the receiving unit 128. Since the heartbeat waveform includes a respiratory component waveform when the subject P is breathing and an aspirating component waveform when the subject P is not breathing, the heartbeat waveform measuring unit 112 determines the amplitude of the aspirating component waveform. Measure (S13).

The heart rate waveform measuring unit 112 determines whether or not the amplitude of the apnea component waveform is the maximum (S14). Whether or not the amplitude of the apnea component waveform is maximum is determined by whether or not the amplitude exceeds a preset threshold value, or the position where the amplitude of the apnea component waveform is maximum is determined while moving the housing 123. Do it by looking for it.

If the amplitude is the maximum (S14: YES), the work shifts to the confirmation work of whether the frequency measurement of the respiratory component (that is, the measurement of the respiratory rate) is possible at the antenna installation position (S15). If the amplitude is not the maximum (S14: NO), it is determined that the transmitting antenna 124 and the receiving antenna 126 are not positioned so as to sandwich the heart (particularly the left ventricle) of the subject P. As shown in FIG. 7, the positions of the transmitting antenna 124 and the receiving antenna 126 are changed from, for example, the position of the dotted line to the position of the solid line, and the transmitting antenna 124 and the receiving antenna 126 are the hearts of the subject P. (Especially the left ventricle) should be sandwiched.

In the work of confirming whether the frequency measurement of the respiratory component (that is, the measurement of the respiratory rate) is possible, the respiratory rate calculation unit 114 and the acceleration sensor 130 determine whether the respiratory rate can be calculated (S15). As an example of the criterion, it is conceivable to set a threshold value for the reproducibility of the respiratory rate within a certain period of time. If the respiratory rate is measurable (S15: YES), the processing of positioning the housing 123 is completed, and if the amplitude is not the maximum (S15: NO), the value of the count N is incremented by 1 (S16). If the number of times NO is obtained in S15 (value of count N) is less than the predetermined number of times (S17: YES), the positions of the transmitting antenna 124 and the receiving antenna 126 are moved (S18), and the processing of S15 is performed again. .. At this time, the moving distance between the transmitting antenna 124 and the receiving antenna 126 performed in the process of S18 is smaller than the moving distance in S10.

When the number of times NO is obtained in S15 is equal to or greater than the predetermined number of times (S17: NO), it is determined that the respiratory rate cannot be obtained even if the processes of S15 and S18 are repeated, and the respiratory rate is most measured. Acceleration is performed while the processing of positioning the housing 123 is completed at the position where the accuracy is high, and when the calculation result is displayed (S110 in FIG. 8), the respiratory rate is also displayed as a reference value. The respiratory rate measurement result by the sensor 130 is displayed on the display unit 154.

Further, when the amplitude of the apnea component waveform becomes less than the preset threshold as a result of the processing of S15 to S18, the positions of the transmitting antenna 124 and the receiving antenna 126 are set to the installation positions obtained in S14. When the calculation result is displayed (S110 in FIG. 8), the accelerometer 130 indicates that the respiratory rate is a reference value. The respiratory rate measurement result is displayed on the display unit 154.

As described above, the housing 123, in other words, the transmitting antenna 124 and the receiving antenna 126 are positioned.

The above is the configuration and operation of the positioning device 200. Next, the operation of the cardiac output measuring device 100 will be described.

(Operation of cardiac output measuring device)
FIG. 9 is an operation flowchart for the cardiac output measuring device 100 of the present embodiment to calculate the cardiac output and the respiratory rate. The operation flowchart will be described with reference to FIGS. 9A to 9D. Note that FIG. 9A is a diagram showing a microwave waveform (respiratory component waveform + apnea component waveform) measured by the heart rate waveform measuring unit. FIG. 9B is a diagram provided by the frequency calculation unit for explaining a method of calculating the frequency of the respiratory component waveform. FIG. 9C is a diagram provided by the frequency calculation unit for explaining a method of calculating the frequency of the apnea component waveform. FIG. 9D is a diagram showing an example of a cardiac output waveform after molding (a waveform for obtaining a cardiac output) used by the cardiac output calculation unit to calculate the cardiac output.

When the measurement start switch 140 is pressed, the control unit 110 instructs the transmission unit 122 to output microwaves, the transmission unit 122 outputs microwaves from the transmission antenna 124, and the microwaves are output to the chest of the subject. (S100). The microwave transmitted through the chest of the subject is received by the receiving antenna 126 (S101), and the received microwave is amplified by the receiving unit 128 and input to the heart rate waveform measuring unit 112.

The heart rate waveform measuring unit 112 measures the microwave waveform in which the respiratory component waveform and the apnea component waveform are mixed as shown in FIG. 9A from the input microwave (S102). This is because the subject measures the heartbeat waveform while breathing.

The frequency calculation unit 115 calculates the frequency of the respiratory component waveform among the microwave waveforms as shown in FIG. 9A measured by the heart rate waveform measurement unit 112 (S103). The frequency of this respiratory component waveform is used as the measurement result of the respiratory rate. The frequency of the respiratory component waveform is calculated from the number of inflection points of the respiratory component waveform that appear within a unit time. Specifically, the frequency is calculated as follows.

The frequency calculation unit 115 measures the amplitude intensity of the microwave waveform shown in FIG. 9A at regular time intervals. For example, as shown in FIG. 9B, the amplitudes x1, x2, x3, x4, x5, x6, x7, x8 ... Of the heartbeat waveform are measured for each time ta. In this measurement, the total elapsed time required until x1 = Xn, that is, n such that x1 = Xn is obtained, and the frequency f is calculated by converting it into a value per unit time. For example, in the case of FIG. 9B, the amplitude intensity of the respiratory waveform component is the same for x1 and x8, and the measurement time required from the start of measurement (x1) to the acquisition of the same amplitude intensity again (x8) is ta8-ta1 = 7 × ta. Therefore, the value obtained by converting 7 × ta per unit time is the frequency.

The measurement time interval ta for calculating the frequency of the respiratory waveform component is about 10 times one cycle of the respiratory waveform component because it adversely affects the measurement accuracy if it is too small or too large with respect to the frequency of the respiratory waveform component. It is preferable to set the time so that the cycle becomes. Further, the criterion for setting x1 = Xn, that is, the criterion for determining how close the amplitude intensities are to be regarded as the same amplitude intensity can be freely set.

As a method of obtaining the frequency of the respiratory component waveform, a general method of finding the unevenness and the inflection point of the graph may be used. For example, the amplitude intensity x1, x2, x3, x4, x5, x6, x7, x8 ... Of the heartbeat waveform is measured at every ta for a certain period of time, a curve passing through these measurement points is drawn, and the slope of the tangent line changes. , The time point at which the inflection point is reached (the time point at ta8 where x8 is measured in FIG. 4B) may be obtained from the positive, zero, and negative changes of the double differentiation of the approximate expression of the curve. The frequency can be obtained by converting the time required for observing this inflection point into a value per unit time.

The frequency calculation unit 115 stores the frequency of the respiratory component waveform calculated as described above in the storage unit 117 (S104).

Next, the frequency calculation unit 115 calculates the frequency of the apnea component waveform among the microwave waveforms as shown in FIG. 9A measured by the heart rate waveform measurement unit 112 (S105). The frequency of the apnea component waveform is obtained from the number of bending points of the apnea component waveform that appear within a unit time by the same method as when calculating the frequency of the respiratory waveform component. Specifically, it is performed as follows.

The frequency calculation unit 115 measures the amplitude of the microwave waveform shown in FIG. 9A at regular time intervals. For example, as shown in FIG. 9C, the amplitude intensities y1, y2, y3, ... ym, ..., Yn of the heartbeat waveform are measured every time tb. In this measurement, the sum of the elapsed times required until ym = yn is obtained, and the frequency f is calculated by converting it into a value per unit time. In the case of FIG. 9C, since the amplitude intensity of the respiratory waveform component is the same for y2 and y10, the value obtained by converting tb10-tb2 = 8 × tb per unit time is the frequency. It should be noted that the calculation may be performed by using a general method for obtaining the unevenness and the inflection point of the graph, as in the explanation when calculating the frequency of the respiratory waveform component.

The frequency calculation unit 115 stores the frequency of the apnea component waveform calculated as described above in the storage unit 117 (S106).

The cardiac output calculation unit 116 generated a filter matching the frequency of the respiratory component waveform using the frequency of the respiratory component waveform stored in the step of S104, and applied the generated filter to remove the respiratory component. Shape the waveform (S107). Next, the cardiac output calculation unit 116 generated a filter matching the frequency of the apnea component waveform (heartbeat) using the frequency of the apnea component waveform stored in the step of S106, and generated the filter. A waveform is formed by applying a filter to extract the heartbeat more (S108).

From the process of the step S102 to the process of the step S108, the microwave waveform of FIG. 9A is formed into a heartbeat waveform as shown in FIG. 9D. The cardiac output calculation unit 116 calculates the cardiac output of the subject's heart from the molded cardiac output (waveform for obtaining the cardiac output) shown in FIG. 9D (S109). The control unit 110 causes the display unit 154 to display the calculated cardiac output and respiratory rate (S110).

Further, the frequency of the respiratory component waveform is calculated from the microwave waveform as shown in FIG. 9A (S103), the frequency of the apnea component waveform is calculated (S105), and the waveform for obtaining the heart rate output is formed (S105). The series of steps (S103 to S108) up to S108) can also be performed as follows.

First, a wide bandpass filter or lowpass filter is applied to the microwave waveform as shown in FIG. 9A. By doing so, fine irregularities derived from the apnea component waveform are removed from the microwave waveform as shown in FIG. 9A, and a waveform as if it is composed of only the respiratory component waveform can be obtained. With respect to this waveform, the frequency of the respiratory component waveform is calculated by using a method of calculating the frequency of the waveform based on the number of times the voltage crosses a certain threshold value per unit time (S103).

The frequency calculation unit 115 stores the frequency of the respiratory component waveform calculated as described above in the storage unit 117 (S104). The cardiac output calculation unit 116 generated a filter matching the frequency of the respiratory component waveform using the frequency of the respiratory component waveform stored in the step of S104, and applied the generated filter to remove the respiratory component. Shape the waveform (S107).

Next, the frequency of the apnea component waveform is calculated by using the waveform obtained in step S107 excluding the respiratory component and using a method of calculating the frequency of the waveform by the number of times the voltage crosses a certain threshold per unit time. (S105). Then, the frequency calculation unit 115 stores the frequency of the apnea component waveform calculated in this way in the storage unit 117 (S106). The cardiac output calculation unit 116 uses the frequency of the apnea component waveform stored in the step of S106 to generate a filter that matches the frequency of the apnea component waveform, and the generated filter is obtained in S107. By applying to the waveform excluding the respiratory component, a waveform for obtaining the cardiac output, which is a more extracted heartbeat, is formed (S108).

As described above, the cardiac output measuring device 100 measures the cardiac output and the respiratory rate. In the above example, the cardiac output and the respiratory rate are displayed on the display unit 154, but the cardiac output and the respiratory rate are stored in the storage unit 117 or on the external terminal 170 via the communication unit 118. You may send it.

In addition to the cardiac output, the stroke amount calculated from one waveform amplitude intensity may be displayed. Furthermore, the frequency of the heartbeat may be displayed as the heart rate. Further, the body surface area may be calculated from the input information such as the height and weight of the subject, and the cardiac output may be divided by the body surface area to be displayed as a cardiac index.

In the calculation of the stroke volume, it may be calculated from one waveform amplitude intensity, but by calculating the cardiac output from the heart rate waveform having a plurality of amplitudes and dividing the value by the heart rate. It may be calculated.

Although the present invention is described as a device for measuring cardiac output in the specification, regarding the amount of blood pumped from the heart, not only the cardiac output but also the stroke amount once and the cardiac index are used. Etc., and since these indexes can be converted to each other, these are not particularly limited in the present invention.

As described above, according to the cardiac output measuring device of the present embodiment, both the cardiac output of the subject and the respiratory state can be accurately measured.

The embodiment of the cardiac output measuring device of the present invention has been described above. However, the technical idea of the cardiac output measuring device of the present invention is not limited to the embodiments exemplified above. The technical idea of the present invention may be embodied in an embodiment other than the embodiments illustrated above. Further, in the present embodiment, an electromagnetic wave having a frequency of 0.4 GHz to 1.00 GHz is used. Although it is explained that microwaves are used, the definition of microwaves is not due to the difference in definitions such as the definition of an electromagnetic wave having a frequency of 300 MHz to 300 GHz and the definition of an electromagnetic wave having a frequency of 3 GHz to 30 GHz. Further, it is preferable to set the frequency at which the waveform for which the cardiac output is obtained is obtained most clearly, and electromagnetic waves such as short wave, ultra high frequency wave, and ultra high frequency wave may be used.

This application is based on a Japanese patent application filed on September 30, 2019 (Japanese Patent Application No. 2019-179129), the disclosure of which is referenced and incorporated as a whole.

100 cardiac output measuring device,
110 control unit,
111 processor,
112 Heart rate waveform measuring unit,
114 Respiratory rate calculation unit,
115 Frequency calculation unit,
116 Cardiac output calculation unit,
117 Memory,
118 Communication Department,
119 drive unit,
121 Moving part,
122 transmitter,
123 housing,
124 transmitting antenna,
125 drive mechanism,
126 receiving antenna,
127 sleeper,
128 receiver,
129 pedestal,
130 accelerometer,
140 Measurement start switch,
152 Notification unit,
154 display section,
160 input section,
170 external terminal,
200 positioning device,
h heart,
P subject.

Claims

It has a heartbeat waveform measuring unit that measures the waveform of microwaves that have passed through the living body.
The heartbeat waveform measuring unit includes a respiratory component waveform and an apnea component waveform in the microwave waveform that has passed through the living body.
A first calculation means for calculating a waveform for obtaining the cardiac output of the living body from the waveform of the microwave using the waveform at the time of apnea.
A second calculation means for calculating a waveform for obtaining the respiratory rate of the living body from the waveform of the microwave using the waveform at the time of respiration, and
A cardiac output measuring device.
The first calculation means is
The cardiac output measuring device according to claim 1, wherein a waveform for obtaining the cardiac output of the living body is calculated from the waveform of the microwave using the waveform during respiration and the waveform during apnea.
The second calculation means is
The heart rate output measuring device according to claim 1 or 2, wherein a waveform for obtaining the respiratory rate of the living body is calculated from the waveform of the microwave using the waveform at the time of breathing and the waveform at the time of apnea.
The calculation means is
A frequency calculation unit that calculates the frequencies of the respiratory component waveform and the apnea component waveform included in the microwave waveform measured by the heart rate waveform measuring unit, and
A respiratory rate calculation unit that calculates the respiratory rate using the frequency of the respiratory component waveform, and
A cardiac output calculation unit that calculates a waveform for obtaining the cardiac output using the frequencies of the respiratory component waveform and the apnea component waveform, and
The cardiac output measuring device according to any one of claims 1 to 3.
The frequency calculation unit
The frequency of the respiratory component waveform is calculated from the number of inflection points of the respiratory component waveform appearing within a unit time, and the apnea component waveform is calculated from the number of inflection points of the apnea component waveform appearing within the unit time. The heart rate measuring device according to claim 4, which calculates a frequency.
The frequency calculation unit
The frequency of the respiratory component waveform is calculated by the number of times the voltage value of the microwave waveform crosses a certain threshold per unit time, and the frequency of the microwave waveform crosses a certain threshold per unit time. The heart rate output measuring device according to claim 4, which calculates the frequency of the aspirating component waveform.
The cardiac output calculation unit
The fourth aspect of claim 4, wherein a filter matching the frequency of the respiratory component waveform and a filter matching the frequency of the apnea component waveform are generated, and the waveform for obtaining the cardiac output is calculated using the generated filter. Cardiac output measuring device.
The frequency calculation unit
The frequency of the respiratory component waveform is calculated using a waveform obtained by applying a predetermined low-pass filter or band-pass filter to the microwave waveform, and the heart rate output calculation unit matches the respiratory component waveform. The present invention according to any one of claims 4 to 6, wherein a filter is generated, and the frequency of the aspiratory component waveform is calculated using a waveform obtained by applying a filter that matches the respiratory component waveform to the microwave waveform. Heart rate measuring device.
further,
It has a filter coefficient calculation formula for generating a filter and a storage unit for storing the filter.
The cardiac output calculation unit
A filter matching the frequency of the respiratory component waveform and a filter matching the frequency of the apnea component waveform are generated from the respective filter coefficient calculation formulas and filters stored in the storage unit.
The cardiac output measuring device according to claim 7 or 8, wherein the filter data is a digital filter such as a low-pass filter or a band-pass filter.
The cardiac output measuring device according to any one of claims 1 to 9, further, as a means for measuring the respiratory rate, an acceleration sensor attached to the body surface of the living body is connected.
Further, a transmitting antenna that irradiates the living body with the microwave and
A receiving antenna that receives the microwave that has passed through the living body, and
A positioning device that moves at least one of the transmitting antenna and the receiving antenna in order to change the relative positions of the transmitting antenna and the receiving antenna.
The cardiac output measuring device according to any one of claims 1 to 10.
The positioning device is
The cardiac output according to claim 11, further comprising a driving unit that drives the positioning device so that the amplitude of the waveform for which the cardiac output is obtained is maximized to change the relative positions of the transmitting antenna and the receiving antenna. Output measuring device.
The positioning device is
Relative between the transmitting antenna and the receiving antenna so that both the results of the respiratory rate calculation by the respiratory rate calculation unit and the calculation result of the cardiac output by the cardiac output calculation unit are optimal. The cardiac output measuring device according to claim 11, further comprising a driving unit that changes the position.