Impedance respiration measurement device and impedance respiration measurement method

Abstract

To provide an impedance respiration measuring apparatus capable of preventing failure to detect respiration resulting from a phase shift in detecting a respiration detection signal.SOLUTION: An impedance respiration measuring apparatus includes: an inspection signal forming unit for forming an inspection signal to be applied to an electrode from a reference signal having a predetermined cycle; a detection unit for detecting a potential difference that appears in the electrode when the detection signal is applied to a living body through the electrode, as a respiration detection signal; a mask signal generation unit for generating an inhibit signal as a mask signal; a detection unit composed of a multiplexer for extracting a respiration waveform included in the respiration detection signal by detecting the respiration detection signal using the reference signal and the inhibit signal; and a phase control unit for controlling the phase of the reference signal and / or the inhibit signal input to the detection unit.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an impedance respiration measurement device and an impedance respiration measurement method that detect a change in impedance between electrodes due to respiration using a synchronous detection method and measure respiration based on the change.

Background Art

[0002] An impedance respiration measurement device is widely used as a device for measuring the respiration of a subject for whom it is difficult to measure respiration based on exhaled gas, such as a newborn. [[ID=十四]]

[0003] Techniques related to conventional impedance respiration measurement devices are disclosed, for example, in Patent Document 1. An impedance respiration measurement device applies a test signal of, for example, 33 kHz to a pair of electrodes attached to the chest of a subject. Based on the detection signal obtained at the electrodes at that time (hereinafter sometimes referred to as a "respiration detection signal"), a change in electrical impedance due to the respiration of the subject is detected. At this time, the impedance respiration measurement device extracts a fluctuation component (respiration waveform) due to respiration by synchronously detecting the respiration detection signal with a reference signal (detection signal) of, for example, 33 kHz. The impedance respiration measurement device measures the respiration rate of the subject, etc., based on this fluctuation component.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, due to individual differences in the living organism (subject) and the condition of equipment such as electrodes, a phase shift may occur between the respiratory detection signal, the reference signal (detection signal), and the mask signal (inhibit signal) during the detection of the respiratory detection signal. When this phase shift occurs, sufficient gain is not obtained from detection, and the change in impedance due to breathing cannot be adequately captured. As a result, there is a risk of obtaining erroneous measurement results, such as the presence of apnea even though breathing is actually occurring.

[0006] The present invention has been made in consideration of the above points, and provides an impedance respiration measuring device and an impedance respiration measuring method that can prevent the failure to detect respiration due to phase shift during detection of the respiration detection signal. [Means for solving the problem]

[0007] One aspect of the impedance breathing measuring device of the present invention is An impedance respiration measuring device that detects changes in impedance between electrodes associated with respiration based on a detection signal obtained when a test signal is applied to electrodes attached to the body surface near the respiratory organs of a living organism, and measures respiration based on said impedance changes, A test signal forming unit that forms a test signal to be applied to the electrode from a reference signal having a predetermined period, A detection unit that detects the potential difference that appears at the electrodes when the test signal is applied to the living body via the electrodes as a respiratory detection signal, A mask signal generation unit that generates an inhibit signal as a mask signal, It consists of a multiplexer, and a detection unit that extracts the respiratory waveform contained in the respiratory detection signal by detecting the respiratory detection signal using the reference signal and the inhibitor signal, A phase control unit that controls the phase of the reference signal and / or the inhibit signal input to the detection unit, It is equipped with.

[0008] One embodiment of the impedance respiration measurement method of the present invention is: An impedance respiration measurement method that detects changes in impedance between electrodes associated with respiration based on a detection signal obtained when a test signal is applied to electrodes attached to the body surface near the respiratory organs of a living organism, and measures respiration based on said impedance changes, A step of forming an inspection signal to be applied to the electrode from a reference signal having a predetermined period, The steps include detecting the potential difference that appears at the electrodes when the test signal is applied to the living body via the electrodes as a respiratory detection signal, The steps include generating an inhibit signal as a mask signal, A detection step of extracting the respiratory waveform included in the respiratory detection signal by detecting the respiratory detection signal using the reference signal and the inhibitor signal, A phase control step for controlling the phase of the reference signal and / or the inhibit signal used in the detection step, Includes. [Effects of the Invention]

[0009] According to the present invention, an impedance respiration measuring device and impedance respiration measuring method can be realized that can prevent the failure to detect respiration caused by phase shift during detection of the respiration detection signal. [Brief explanation of the drawing]

[0010] [Figure 1] A perspective view showing the external configuration of a vital signs monitor (bedside monitor) equipped with an impedance respiratory measurement device according to the embodiment. [Figure 2] Block diagram showing the configuration of the vital signs monitor. [Figure 3] Block diagram showing the circuit configuration of the impedance breathing measurement unit. [Figure 4] This diagram shows examples of electrode placement locations used in impedance respiration measurements. [Figure 5] This diagram shows the electrical equivalent circuit of the subject (i.e., the living organism) and how the test signal changes into a respiratory detection signal as it passes through this equivalent circuit. [Figure 6]This is a diagram for explaining the basic operation of the impedance respiration measurement unit (a diagram showing an operation example when the impedance respiration measurement unit does not have a phase control unit). FIG. 6A is a diagram showing each signal waveform input to the detection circuit, FIG. 6B is a diagram showing the output waveform from the detection circuit, FIG. 6C is a diagram showing the envelope obtained by passing through the low-pass filter, and FIG. 6D is a diagram showing the finally obtained respiration waveform [Figure 7] A diagram showing the masked area masked by the inhibition signal [Figure 8] A diagram showing an example where the masking process by the inhibition signal was not performed well [Figure 9] A diagram showing an example where the masking process by the inhibition signal was not performed well [Figure 10] A diagram showing an example where the phase of the inhibition signal was shifted by 90° by the phase control unit and input to the detection circuit [Figure 11] A diagram showing an example where the phase of the inhibition signal was advanced by 90° without changing the phase of the reference signal (detection signal) [Figure 12] A diagram showing an example where the phase of the reference signal (detection signal) was delayed by 90° without changing the phase of the inhibition signal [Figure 13] A diagram showing an example where the phases of both the reference signal (detection signal) and the inhibition signal were delayed by 90° [Figure 14] FIG. 14A is a diagram showing the respiration waveform before performing phase control according to the embodiment, and FIG. 14B is a diagram showing the respiration waveform after performing phase control according to the embodiment [Figure 15] A block diagram showing another circuit configuration example of the impedance respiration measurement unit [Figure 16] A diagram showing an example where the duty ratio of the inhibition signal was changed [Figure 17] A block diagram showing another circuit configuration example of the impedance respiration measurement unit [Figure 18] A diagram for explaining the vector synthesis of the respiration waveform

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012] <1> Overall configuration of the vital signs monitor Figure 1 is a perspective view showing the external configuration of a vital signs monitor (bedside monitor) 10 equipped with the impedance respiratory measurement device according to this embodiment.

[0013] The vital signs monitor 10 has a display unit 101 on its front. Additionally, a standby switch 11 and an alarm indicator 12 are provided on the front of the vital signs monitor 10.

[0014] One side of the vital signs monitor 10 is provided with a group of connectors related to the measurement of vital signs. Specifically, it includes an ECG (Electrocardiogram) connector 13a, an NIBP (Non-Invasive Blood Pressure) connector 13b, and an SpO2 connector 13c. Below the group of connectors is a module connection section 14 to which a module for implementing optional vital signs measurement processing can be attached. Incidentally, the other side of the vital signs monitor 10 (not shown) is provided with a USB connector, a LAN connection connector, and a recorder.

[0015] Figure 2 is a block diagram showing the configuration of the vital signs monitor 10. The vital signs monitor 10 is connected via a connector section 110 to vital signs detection units, including electrocardiogram electrodes 111 for detecting electrocardiogram and impedance respiration, a blood pressure measurement cuff 112 for detecting blood pressure, a body temperature sensor 113 for detecting body temperature, an SpO2 sensor 114 for detecting SpO2, and a cardiac output sensor 115 for detecting cardiac output. The connector section 110 functions as an interface between the vital signs detection units and the measurement processing unit 104. The connector section 110 includes the ECG connector 13a, NIBP connector 13b, and SpO2 connector 13c shown in Figure 1.

[0016] The measurement processing unit 104 executes a predetermined measurement process by running a program stored in the memory unit 105. Through this measurement process, the measurement processing unit 104 measures the subject's biological information using the biological information detection unit (electrocardiogram electrodes 111, blood pressure measurement cuff 112, body temperature sensor 113, SpO2 sensor 114, and cardiac output sensor 115) connected to the connector unit 110. Since conventionally known methods for measuring various biological information using the above-mentioned biological information detection unit can be applied, a detailed explanation thereof is omitted here.

[0017] Furthermore, the measurement processing unit 104 is capable of storing previously measured biological information in the storage unit 105, and reading biological information stored in the storage unit 105. In addition, the biological information obtained by the measurement processing unit 104 is displayed on the display unit 101 in the form of measured values ​​or waveforms via the display control unit 102.

[0018] The display unit 101 is, for example, a liquid crystal display with a touch panel, and not only has a display function to display biometric information, but also functions as an input unit to accept user input operations. Specifically, the display control unit 102 changes the display on the display unit 101 and the processing of the measurement processing unit 104 based on the user's touch operation of the display unit 101. In this embodiment, user operations such as various settings are accepted by touch operation of the display unit 101, but user operations may also be accepted using, for example, a keyboard, mouse, or dedicated buttons.

[0019] Furthermore, the measurement processing unit 104 includes an impedance respiration measurement unit 200. The impedance respiration measurement unit 200 measures the subject's respiration based on impedance changes detected by the electrocardiogram electrodes 111.

[0020] <2> Configuration of the impedance breathing measurement unit 200 Figure 3 is a block diagram showing the circuit configuration of the impedance breathing measurement unit 200.

[0021] The impedance respiration measurement unit 200 has a reference signal generation circuit 201, which generates a square wave of, for example, 33.3 kHz as a reference signal (hereinafter sometimes referred to as the "respiration drive signal"). In this embodiment, the reference signal generation circuit 201 generates and outputs positive-phase and negative-phase reference signals S11 and S12 as reference signals.

[0022] The frequencies of the reference signals S11 and S12 generated by the reference signal generation circuit 201 are not limited to these frequencies; for example, they may be in the range of several tens of kHz to several hundred kHz, or even higher.

[0023] Reference signals S11 and S12 are converted into test signals S1 and S2 via a low-pass filter (LPF) 202 and an amplifier (AMP) 203, respectively, and these are applied to electrodes (in this embodiment, electrocardiogram electrodes 111) attached to the subject (living body) B0.

[0024] Furthermore, the impedance respiration measurement unit 200 has a detection circuit 205. The detection circuit 205 is connected to electrodes (electrocardiogram electrodes 111) attached to the subject (living body) B0 via an amplifier (AMP) 204. As a result, the detection circuit 205 receives respiration detection signals S1' and S2', in which the test signals S1 and S2 are superimposed with low-frequency fluctuation components (which can also be called impedance change components) caused by the subject's respiration.

[0025] Furthermore, the reference signal S12 output from the reference signal generation circuit 201 is input to the phase control unit 230. The phase-controlled reference signal S30 is then input to the detection circuit 205. Hereafter, the reference signal input to the detection circuit 205 may be referred to as the "detection signal". Alternatively, the phase control unit 230 may be configured to receive a reference signal S11 instead of a reference signal S12, and then phase-controlled the reference signal S11 to form the phase-controlled reference signal S30.

[0026] Furthermore, the inhibit signal S20, which is output as a mask signal from the mask signal generation circuit 220, is input to the phase control unit 230, where it is phase-controlled, and the inhibit signal S40 after phase control is input to the detection circuit 205.

[0027] Here, the inhibit signal S20 is a signal with half the period of the reference signals S11 and S12.

[0028] In the example shown in Figure 3, the phase control unit 230 controls the phase of the reference signal S12 (or S11) and the inhibit signal S20 based on the operation setting information set by the user. This phase control will be explained in detail later.

[0029] The detection circuit 205 extracts the fluctuation components due to breathing by detecting the breathing detection signals S1' and S2' with the phase-controlled reference signal S30, and masks the unnecessary parts with the phase-controlled inhibit signal S40.

[0030] The output signals S1'' and S2'' from the detection circuit 205 are input to the differential amplifier 207 via a low-pass filter (LPF) 206. The output of the differential amplifier 207 passes through a high-pass filter (HPF) 208, an amplifier (AMP) 209, a low-pass filter (LPF) 210, and an analog-to-digital conversion circuit 211, allowing only the frequency components corresponding to the breathing frequency (e.g., 0.1~1.5Hz) to pass through, be amplified, and digitized to obtain the breathing waveform data S3.

[0031] The respiratory waveform shown by the respiratory waveform data S3 can be displayed on the display unit 101 via the display control unit 102. The measurement processing unit 104 also measures the respiratory rate based on the respiratory waveform data S3. The measurement processing unit 104 controls the alarm indicator 103 to output an alarm if the respiratory rate falls below a lower threshold or exceeds an upper threshold.

[0032] <3> Operation of the impedance breathing measurement unit 200 Next, the operation of the impedance breathing measurement unit 200 will be explained.

[0033] Figure 4 shows an example of electrode placement for impedance respiration measurement. In this embodiment, a positive-phase test signal S1 is applied to electrode E1 attached to the lower right clavicle of the subject, while a negative-phase test signal S2 is applied to electrode E2 attached to the lower left abdomen.

[0034] Furthermore, the inverse phase test signal S2 may be applied to electrode E3 attached to the left subclavian region. Moreover, the application locations of the test signals S1 and S2 are not limited to these; essentially, any location that can detect changes in the impedance of the biological body B0 caused by respiration is acceptable.

[0035] Furthermore, in this embodiment, a respiratory detection signal S1' for the examination signal S1 is obtained via electrode E1 attached to the lower right clavicle of the subject, and a respiratory detection signal S2' for the examination signal S2 is obtained via electrode E2 attached to the lower left abdomen.

[0036] Figure 5 shows the electrical equivalent circuit of the subject (i.e., biological body B0) and how the test signals S1 and S2 change into respiratory detection signals S1' and S2' as they pass through this equivalent circuit. In the figure, the symbol Zb represents the resistance including the contact resistance of biological body B0 and electrodes E1 and E2, and the symbol ΔZ represents the impedance change due to respiration. In response to this impedance change ΔZ, the test signals S1 and S2 change into respiratory detection signals S1' and S2', respectively. Note that in Figure 5, for the sake of clarity, the frequencies are shown lower than the actual frequencies.

[0037] Figure 6 is a diagram illustrating the basic operation of the impedance respiration measurement unit 200. Figure 6 shows an example of operation when the impedance respiration measurement unit 200 does not have a phase control unit 230. Figure 6A shows the waveforms of each signal input to the detection circuit 205, Figure 6B shows the output waveform from the detection circuit 205, Figure 6C shows the envelope obtained by passing the signal through the low-pass filter 206, and Figure 6D shows the final respiration waveform.

[0038] The detection circuit 205 is composed of analog switches, such as a multiplexer. The detection circuit 205 outputs the input respiration detection signals S1' and S2' while switching them based on the reference signal S12. As can be seen from Figure 6B, the detection circuit 205 outputs only the vicinity of the peaks of the respiration detection signals S1' and S2'.

[0039] Furthermore, the detection circuit 205 masks a predetermined region of the detected output by stopping its output with the inhibit signal S20. Figure 7 shows the masked region that is masked by the inhibit signal S20. As can be seen from Figure 7, the detection circuit 205 masks the switching portion of the multiplex output signal based on the inhibit signal S20.

[0040] Specifically, the detection circuit 205 stops outputting when the inhibit signal S20 is High. In other words, the detection circuit 205 outputs the input breath detection signals S1' and S2' when the reference signal S12 is High, and stops outputting when the inhibit signal S20 is High, even if the reference signal S12 is High.

[0041] This allows us to retain only the vicinity of the peaks of the respiration detection signals S1' and S2', thereby refining the shape of the envelope (Figure 6C) obtained by subsequent low-pass filtering. In other words, the shape of the envelope can be made to better reflect the fluctuations caused by respiration.

[0042] Here, the example shown in Figure 6 is an example where the masking process using the inhibit signal S20 was performed successfully. On the other hand, Figures 8 and 9 are examples where the masking process using the inhibit signal S20 was not performed successfully.

[0043] In the example in Figure 8, the high portion of the inhibit signal S20 is out of sync with the rising and falling edges of the reference signal (detection signal) S12 that controls the multiplex switching, resulting in approximately half of the maximum amplitude of the breath detection signals S1' and S2' output from the detection circuit 205 being masked.

[0044] In the example in Figure 9, although the high portion of the inhibit signal S20 coincides with the rising and falling edges of the reference signal (detection signal) S12 that controls the multiplex switching, it overlaps with the peak portions of the breath detection signals S1' and S2', so the maximum amplitude portions of the breath detection signals S1' and S2' output from the detection circuit 205 are masked.

[0045] Thus, if the phase relationship between the inhibit signal S20 and the reference signal (detection signal) S12 is inappropriate (Figure 8), or if the phase relationship between the inhibit signal S20 and the respiration detection signals S1' and S2' is inappropriate (Figure 9), the output signal from the detection circuit 205 will not be properly masked, and the area near the maximum amplitude of the respiration detection signals S1' and S2' will be cut off. As a result, insufficient gain cannot be obtained, and consequently, the amplitude of the respiration waveform (Figure 6D) will be reduced. Consequently, as explained in the section on the problems that the invention aims to solve, there is a risk of obtaining an incorrect measurement result, such as the subject being reported as apnea even though they are actually respiring.

[0046] The present invention has been made in view of this point, and by providing a phase control unit 230 in the impedance respiration measurement unit 200, and by appropriately controlling the phase of the reference signal S12 and / or inhibitor signal S20 input to the detection circuit 205 with the phase control unit 230, it is possible to obtain a respiration waveform (Figure 6D) with sufficient amplitude without masking the vicinity of the maximum amplitude of the respiration detection signals S1' and S2' with the inhibitor signal S40.

[0047] Figure 10 shows an example in which the phase of the inhibitor signal S20 is shifted by 90° by the phase control unit 230 due to the inappropriate phase relationship shown in Figure 8, and input as the inhibitor signal S40 to the detection circuit 205. In this way, the inhibitor signal S40 no longer masks the vicinity of the maximum amplitude of the breath detection signals S1' and S2', and the switching portion of the multiplex can be masked effectively.

[0048] In the example shown in Figure 10, the phase control unit 230 shifts the phase of the inhibit signal S20 by 90° and inputs it to the detection circuit 205 as the inhibit signal S40. However, the phase control performed by the phase control unit 230 is not limited to this. The phase control patterns that the phase control unit 230 should perform are as follows.

[0049] Pattern 1: As shown in Figure 11, the phase of the inhibitor signal S40 is advanced by 90° without changing the phase of the reference signal (detection signal) S30. This Pattern 1 is the same as Figure 10 described above.

[0050] Pattern 2: As shown in Figure 12, the phase of the inhibitor signal S40 is not changed, and the phase of the reference signal (detection signal) S30 is delayed by 90°.

[0051] Pattern 3: As shown in Figure 13, the phases of both the reference signal (detection signal) S30 and the inhibit signal S40 are delayed by 90°.

[0052] By performing phase control according to Pattern 1, it becomes possible to avoid situations where the relative phase relationship between the inhibit signal S20 and the respiratory detection signals S1' and S2' is such that the inhibit signal S20 masks the vicinity of the maximum amplitude of the respiratory detection signals S1' and S2'.

[0053] Furthermore, by performing phase control in Pattern 2, it becomes possible to avoid situations where the relative phase relationship between the reference signal (detection signal) S12 and the breath detection signals S1' and S2' causes the detection to become out of sync.

[0054] Furthermore, by performing phase control according to pattern 3, it becomes possible to avoid situations where the relative phase relationship between the inhibit signal S20 and the respiration detection signals S1' and S2' is such that the inhibit signal S20 masks the vicinity of the maximum amplitude of the respiration detection signals S1' and S2', and where the relative phase relationship between the reference signal (detection signal) S12 and the respiration detection signals S1' and S2' is such that the detection synchronization is lost.

[0055] It is preferable to determine which of the above patterns 1 to 3 of phase control to perform by considering the relative phase relationship between the inhibit signal S20 and the respiration detection signals S1' and S2', and the relative phase relationship between the reference signal (detection signal) S12 and the respiration detection signals S1' and S2'.

[0056] Figure 14 shows the respiratory waveforms before (Figure 14A) and after (Figure 14B) the phase control described in patterns 1 to 3 above. Specifically, Figure 14A shows a state where the amplitude of the respiratory waveform has decreased due to a phase shift in the inhibit signal S20 and / or the reference signal (detection signal) S12. As shown in Figure 14A, when the amplitude of the respiratory waveform decreases, there is a risk of obtaining an erroneous measurement result, such as the subject being shown as apnea even though they are actually breathing.

[0057] In contrast, according to this embodiment, by performing phase control of patterns 1 to 3, the phase shift of the inhibit signal S20 and / or the reference signal (detection signal) S12 can be eliminated, and the original breathing waveform as shown in Figure 14B can be obtained. This prevents the failure to detect breathing caused by the phase shift during demodulation of the breathing detection signals S1' and S2'.

[0058] Here, the following methods can be used to implement the phase control of patterns 1 to 3 by the phase control unit 230.

[0059] Method 1: The user manually performs phase switching in patterns 1 to 3. In this case, as shown in Figure 3, operation setting information corresponding to the user operation is input to the phase control unit 230, and the phase control unit 230 performs one of the above-mentioned phase controls in patterns 1 to 3 in response to the user operation. Specifically, the user observes the respiratory waveform displayed on the display unit 101, and if they determine that the amplitude of the respiratory waveform is small, they perform an operation to instruct the phase control unit 230 to perform one of the above-mentioned controls in patterns 1 to 3. For example, when a predetermined operation screen is displayed on the display unit 101, which has a touch panel configuration, the user performs an operation to instruct the above control to be performed by touching a predetermined position. In response to this operation, the phase control unit 230 performs one of the above-mentioned phase controls in patterns 1 to 3. This makes it possible to suppress the decrease in the amplitude of the respiratory waveform caused by the phase shift of the inhibit signal S20 and / or the reference signal (detection signal) S12.

[0060] Method 2: As shown in Figure 15, where the corresponding parts in Figure 3 are denoted by the same reference numerals, the phase control unit 230 controls the phase of the reference signal S30 and / or the inhibit signal S40 based on the amplitude of the respiratory waveform output from the detection circuit 205. Specifically, the impedance respiratory measurement unit 300 in Figure 15 inputs respiratory waveform data S3 to the phase control unit 230. The phase control unit 230 appropriately performs the phase control patterns 1 to 3 described above so as to increase the amplitude of the respiratory waveform. In this way, the phases of the inhibit signal S40 and the reference signal (detection signal) S30 are optimized. Although Figure 15 describes the case where the respiratory waveform data S3 is input to the phase control unit 230, the respiratory waveform data S3 may also be input to another arithmetic control unit such as a CPU (not shown), and the CPU may control the phase control unit 230 so as to increase the amplitude of the respiratory waveform.

[0061] <4> summary As described above, according to this embodiment, the impedance respiration measuring device (impedance respiration measuring unit 200, 300, 400) detects impedance changes between electrodes associated with respiration based on detection signals (respiration detection signals S1', S2') obtained when test signals S1, S2 are applied to electrodes E1~E3 attached to the body surface near the respiratory organs of a living organism B0, and measures respiration based on said impedance changes. The device comprises a test signal forming unit (low-pass filter 202, amplifier 203) that forms test signals S1, S2 to be applied to electrodes E1~E3 from reference signals S11, S12 having a predetermined period, and electrodes E1~ The system comprises a detection unit (resistor R, amplifier 204) that detects the potential difference appearing across electrodes E1 to E3 when test signals S1 and S2 are applied via E3 as a respiration detection signal, a mask signal generation unit (mask signal generation circuit 220) that generates an inhibitor signal S20 as a mask signal, and a multiplexer, a detection unit (detection circuit 205) that extracts the respiration waveform (respiration waveform data S3) contained in the respiration detection signals S1' and S2' by detecting the respiration detection signals S1' and S2' using a reference signal S12 (S11) and an inhibitor signal S20, and phase control units 230 and 240 that control the phase of the reference signal S30 and / or inhibitor signal S40 input to the detection unit (detection circuit 205).

[0062] As a result, the phase of the reference signal S30 and / or inhibitor signal S40 input to the detection unit (detection circuit 205) is controlled by the phase control units 230 and 240. This eliminates the phase shift between the breath detection signals S1' and S2', the reference signal (detection signal) S30, and the mask signal (inhibit signal) S40 that would cause the amplitude of the breath waveform (breath waveform data S3) to become smaller during detection of the breath detection signals S1' and S2'. As a result, an impedance breath measurement device (impedance breath measurement unit 200, 300, 400) and impedance breath measurement method can be realized that can prevent undetected breaths caused by phase shifts during detection of the breath detection signals S1' and S2'.

[0063] Incidentally, when using conventional impedance respiration measurement devices, if the user determined that the amplitude of the respiration waveform was small despite the subject breathing, they would reposition electrodes E1 to E3 to a position where breathing could be detected (i.e., a position where the amplitude of the respiration waveform would be larger). According to this embodiment, it is possible to prevent undetection of respiration caused by phase shift during detection without having to change the position of electrodes E1 to E3 based on the user's judgment.

[0064] The embodiments described above are merely examples of how the present invention can be implemented, and the technical scope of the present invention should not be limited by them. In other words, the present invention can be implemented in various ways without departing from its gist or its main features.

[0065] In the above-described embodiment, the case was described in which the reference signal generation circuit 201 generates positive-phase and negative-phase reference signals S11 and S12, and positive-phase and negative-phase inspection signals S1 and S2 are applied to the living organism B0. However, the present invention is not limited to this, and can be implemented in the same manner as the above-described embodiment even when the reference signal generation circuit 201 generates either a positive-phase or negative-phase reference signal S11 or S12, and either a positive-phase or negative-phase inspection signal S1 or S2 is applied to the living organism B0. However, when positive-phase and negative-phase inspection signals S1 and S2 are applied as in the above-described embodiment, a large gain can be obtained in the differential amplifier 207, thereby improving the accuracy of respiration detection.

[0066] In the above embodiment, we described a case where the phase of the inhibit signal is controlled so that the inhibit signal is in a High state at the rising and falling edges of the reference signal by shifting the phase of the inhibit signal overall, but the embodiment is not limited to this. For example, as shown in Figure 16, the duty cycle of the inhibit signal may be changed so that the center position of the inhibit signal coincides with the rising and falling edges of the reference signal (detection signal). In this way, for example, even if the phase relationship could not be optimized by mask processing by phase control alone, the mask processing can be optimized by supplementing the phase control.

[0067] In the embodiments described above, as examples of configurations to prevent failure to detect respiration due to phase shift during detection of the respiration detection signal, an example in which the phase control unit 230 performs phase control based on user operation (Figure 3) and an example in which the phase control unit 230 performs phase control based on respiration waveform data S13 (Figure 15) were explained. The present invention is not limited to the configuration examples in Figures 3 and 15, but can also adopt a configuration like that shown in Figure 17.

[0068] The impedance respiration measurement unit 400 in Figure 17, which has the same reference numerals as the corresponding part in Figure 3, has a vector synthesis unit 410. The phase control unit 240 of the impedance respiration measurement unit 400 shifts the phase of the reference signal S12 and the inhibit signal S20 by 90° to form a reference signal S30' and an inhibit signal S40' with a 90° phase shift.

[0069] The impedance breathing measurement unit 400 has first and second detection circuits 205-1 and 205-2. The first detection circuit 205-1 performs detection using a phase-unshifted reference signal S12 and an inhibitor signal S20, while the second detection circuit 205-2 performs detection using a 90° phase-shifted reference signal S30' and an inhibitor signal S40'.

[0070] The respiratory waveform data S3-1 and S3-2 obtained by detection circuits 205-1 and 205-2 are vector-synthesized by the vector synthesis unit 410. The resulting respiratory waveform data S4 is then output as the measurement result by the impedance respiratory measurement unit 400.

[0071] Figure 18 illustrates the vector synthesis of the respiratory waveform by the vector synthesis unit 410. As can be seen from Figure 18, by vector synthesis of respiratory waveform data S3-1 obtained using a reference signal S12 and an inhibitor signal S20 that are not phase-shifted, and respiratory waveform data S3-2 obtained using a reference signal S30' and an inhibitor signal S40' that are phase-shifted by 90°, it becomes possible to obtain respiratory waveform data S4 with sufficient amplitude regardless of any phase shift that occurs between the respiratory detection signal, the reference signal (detection signal), and the mask signal (inhibit signal) due to individual differences in the living organism (subject) B0 or ​​the condition of equipment such as electrodes.

[0072] In the embodiments described above, the impedance respiratory measurement device of the present invention (impedance respiratory measurement units 200, 300, 400) was described in relation to a vital signs monitor. However, the impedance respiratory measurement device of the present invention is not limited to a vital signs monitor and may be used independently or incorporated into other medical devices.

[0073] In the above-described embodiment, we described the case where the output and mask of the detection circuit 205 become active when a reference signal (detection signal) and an inhibitor signal are input in a High state; in other words, the case where the signal is active when it is in a High state. However, of course, the present invention can also be applied to the case where the output and mask of the detection circuit 205 become active when a reference signal (detection signal) and an inhibitor signal are input in a Low state. In this case, the case where the signal is active is when it is in a Low state. [Industrial applicability]

[0074] The present invention is widely applicable to impedance respiration measuring devices and impedance respiration measuring methods that measure the respiration of living organisms by detecting impedance changes caused by respiration using a synchronous detection method. [Explanation of Symbols]

[0075] 10. Biometric Information Monitor 200, 300, 400 Impedance Respiratory Measurement Unit 201 Reference signal generation circuit 205 Detection circuit (multiplexer) B0 Living organism S1, S2 test signals S1', S2' Respiration detection signals S3, S3-1, S3-2, S4 Respiratory waveform data S11, S12, S30 Reference signal (detection signal) S20, S40 Inhibit signals

Claims

1. An impedance respiration measuring device that detects changes in impedance between electrodes associated with respiration based on a detection signal obtained when a test signal is applied to electrodes attached to the body surface near the respiratory organs of a living organism, and measures respiration based on said impedance changes, A test signal forming unit that forms a test signal to be applied to the electrode from a reference signal having a predetermined period, A detection unit that detects the potential difference that appears at the electrodes when the test signal is applied to the living body via the electrodes as a respiratory detection signal, A mask signal generation unit generates an inhibitor signal as a mask signal, with a period of 1 / 2 that of the reference signal, A detection unit that extracts the respiratory waveform contained in the respiratory detection signal by detecting the respiratory detection signal using the reference signal and the inhibitor signal, A phase control unit that controls the phase of the reference signal and / or the inhibit signal input to the detection unit, Equipped with, The phase control unit has a mode for shifting the phase of the reference signal and / or the inhibitor signal by 90°. Impedance breathing measurement device.

2. The phase control unit shifts the phase of the reference signal and / or the inhibit signal by 90° based on an operation signal from the user. The impedance respiration measuring device according to claim 1.

3. The detection unit outputs the input respiration detection signal when the reference signal is active, and stops outputting the signal when the inhibit signal is active, even if the reference signal is active. The impedance respiration measuring device according to claim 1 or 2.

4. The phase control unit controls the phase of the reference signal and / or the inhibitor signal based on the amplitude of the breathing waveform output from the detection unit. An impedance respiration measuring device according to any one of claims 1 to 3.

5. The phase control unit controls the phase of the inhibitor signal so that the inhibitor signal is active at the rising and falling edges of the reference signal. An impedance respiratory measuring device according to any one of claims 1 to 4.

6. The mask signal generation unit further changes the duty cycle of the inhibit signal. The impedance respiration measuring device according to claim 5.

7. An impedance respiration measuring device that detects changes in impedance between electrodes associated with respiration based on a detection signal obtained when a test signal is applied to electrodes attached to the body surface near the respiratory organs of a living organism, and measures respiration based on said impedance changes, A test signal forming unit that forms a test signal to be applied to the electrode from a reference signal having a predetermined period, A detection unit that detects the potential difference that appears at the electrodes when the test signal is applied to the living body via the electrodes as a respiratory detection signal, A mask signal generation unit generates an inhibitor signal as a mask signal, with a period of 1 / 2 that of the reference signal, A detection unit that extracts the respiratory waveform contained in the respiratory detection signal by detecting the respiratory detection signal using the reference signal and the inhibitor signal, A phase control unit that controls the phase of the reference signal and / or the inhibit signal input to the detection unit, Equipped with, The phase control unit shifts the phase of the reference signal and the inhibit signal by 90° to form the reference signal and the inhibit signal with a 90° phase shift. The detection unit comprises first and second detection units that obtain first and second respiratory waveforms by detecting the respiratory detection signal using the reference signal and the inhibit signal, respectively, which have a phase difference of 90°. The impedance respiration measuring device further includes a vector synthesis unit that vectorizes the first and second respiration waveforms. Impedance breathing measurement device.

8. The impedance respiratory measuring device according to any one of claims 1 to 7, Biological information monitor.

9. An impedance respiration measurement method that detects changes in impedance between electrodes associated with respiration based on a detection signal obtained when a test signal is applied to electrodes attached to the body surface near the respiratory organs of a living organism, and measures respiration based on said impedance changes, A step of forming an inspection signal to be applied to the electrode from a reference signal having a predetermined period, The steps include detecting the potential difference that appears at the electrodes when the test signal is applied to the living body via the electrodes as a respiratory detection signal, The steps include generating an inhibitor signal as a mask signal, with a period of half that of the reference signal, A detection step of extracting the respiratory waveform included in the respiratory detection signal by detecting the respiratory detection signal using the reference signal and the inhibitor signal, A phase control step for controlling the phase of the reference signal and / or the inhibit signal used in the detection step, Includes, The phase control step includes a mode of shifting the phase of the reference signal and / or the inhibit signal by 90°. Impedance respiration measurement method.

10. An impedance respiration measurement method that detects changes in impedance between electrodes associated with respiration based on a detection signal obtained when a test signal is applied to electrodes attached to the body surface near the respiratory organs of a living organism, and measures respiration based on said impedance changes, A step of forming an inspection signal to be applied to the electrode from a reference signal having a predetermined period, The steps include detecting the potential difference that appears at the electrodes when the test signal is applied to the living body via the electrodes as a respiratory detection signal, The steps include generating an inhibitor signal as a mask signal, with a period of half that of the reference signal, A detection step of extracting the respiratory waveform included in the respiratory detection signal by detecting the respiratory detection signal using the reference signal and the inhibitor signal, A phase control step for controlling the phase of the reference signal and / or the inhibit signal used in the detection step, Includes, In the phase control step, the phases of the reference signal and the inhibit signal are shifted by 90° to form the reference signal and the inhibit signal with a 90° phase shift. In the detection step, the first and second respiratory waveforms are obtained by detecting the respiratory detection signal using the reference signal and the inhibit signal, respectively, which have a phase difference of 90°. The impedance respiration measurement method further includes the step of vectorizing the first and second respiration waveforms. Impedance respiration measurement method.

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