JP3840811B2 - Cardiac output monitoring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cardiac output monitoring apparatus that continuously monitors a cardiac output of a living body based on fluctuations in a pulse wave at a peripheral portion of the living body.
[0002]
[Prior art]
Monitoring the blood output from the heart is extremely important in monitoring the patient's condition, and urgent treatment is required when the blood output from the heart decreases. The minute volume, ie, the cardiac output, which indicates the blood output from the heart per minute, is calculated by using the Fick principle.₂Is divided by the difference (A−V) between the oxygen content A of arterial blood and the oxygen content V of mixed venous blood. In addition, a dye or a radioisotope is injected from a part of a living body, a change in transmitted light is detected using a densitometer, and it is obtained indirectly by a dilution method for obtaining a concentration curve of the dye. Can do.
[0003]
[Problems to be Solved by the Invention]
However, when the cardiac output is calculated using the Fick principle, the amount of oxygen collected per minute O₂The oxygen content A of arterial blood is easily measured, but the oxygen content V of mixed venous blood is difficult to measure. For example, in order to directly measure the oxygen content V of mixed venous blood, the catheter is connected to the pulmonary artery or Pulmonary arterial blood must be collected, such as by placing it in the right ventricle. Even in the indirect method, mixed venous blood is obtained by collecting continuous arterial blood during re-breathing after rebreathing a gas of appropriate composition and measuring changes in gas content during rebreathing. The oxygen content V of the arterial blood and the oxygen content V of the mixed venous blood from the composition of the gas in the sac by further rebreathing a gas such as acetylene from the sac for a short time The method of calculating the difference (A−V) must be used. Therefore, it has been difficult to continuously monitor a patient's cardiac output. In addition, the method of measuring cardiac output by the dilution method also requires the injection of a dye or a radioisotope from a part of the living body, so that the apparatus becomes complicated and large, and the cardiac output of the patient is continuously increased. Monitoring was difficult.
[0004]
For this reason, blood pressure values are generally used as surrogate values for cardiac output in monitoring patient conditions. When monitoring the blood pressure value over a relatively long period of time, the blood pressure value of the living body is generally measured by having a cuff wound around a part of the living body and changing the pressure applied by the cuff. A blood pressure monitoring device is used in which the blood pressure measuring means is automatically activated at a predetermined cycle. This is because the blood pressure measurement value measured using the cuff by this blood pressure measurement means is relatively reliable.
[0005]
However, when the patient's condition is monitored by measuring the blood pressure with the blood pressure monitoring device, reducing the automatic start cycle in order to eliminate the delay in blood pressure monitoring increases the frequency of cuff compression against the living body, which is a heavy burden. There is a drawback that the living body is forced, and when the frequency of cuff compression is extremely high, there is a case where congestion occurs and an accurate blood pressure value cannot be obtained.
[0006]
The present invention has been made against the background of the above circumstances, and the object of the present invention is to provide a cardiac output monitoring device capable of easily and continuously monitoring changes in the cardiac output of a living body. Is to provide.
[0007]
The present inventor has found that the blood flow in the peripheral part per unit time changes in close relation to the change in the cardiac output of the living body, while conducting various studies on the background of the above situation. The present invention has been made based on such knowledge.
[0008]
[Means for Solving the Problems]
  In other words, to achieve the above purposeFirstThe gist of the invention is a cardiac output monitoring device for monitoring the cardiac output of a living body, and (a) a volume pulse wave detecting device for detecting a volume pulse wave of a peripheral portion of the living body; (B) a pulse wave area calculating means for calculating the area of the volume pulse wave detected by the volume pulse wave detecting device; and (c) heart rate information calculation for calculating heart rate information related to the heart rate of the living body. And (d) a pseudo heart that sequentially calculates a pseudo cardiac output that is a product of the volume pulse wave area calculated by the pulse wave area calculating means and the heart rate information calculated by the heart rate information calculating means. By means of the stroke volume calculating means and (e) the pseudo cardiac output calculating meansSequentialA change value calculating means for calculating the calculated change value of the pseudo cardiac output, and (f) a change value displaying means for displaying the change value calculated by the change value calculating means on the display. is there.
[0009]
【The invention's effect】
  In this way, when the volume pulse wave of the peripheral part of the living body is detected by the volume pulse wave detection device, the pulse wave area calculation means detects the volume pulse wave detected by the volume pulse wave detection device from the volume pulse wave of the peripheral part. The pulse wave area indicating the blood flow rate is calculated, and in the pseudo cardiac output calculation means, the product of the pulse wave area and the heart rate information calculated by the heart rate information calculation means relates to the change in cardiac output. As pseudo cardiac output that changesSequentialAnd the change value calculation meansCalculated sequentiallyA change value of the pseudo cardiac output is calculated, and the change value is displayed on the display by the change value display means. Accordingly, since the change value of the pseudo cardiac output that changes in relation to the change of the cardiac output is displayed on the display, the change in the cardiac output of the living body can be easily and continuously monitored. it can.
[0010]
  Further, the gist of the second invention for achieving the above object is a cardiac output monitoring device for monitoring the cardiac output of a living body, (a) A volume pulse wave detecting device for detecting a volume pulse wave at a peripheral portion of the living body; (b) A pulse wave area calculating means for calculating the area of the volume pulse wave detected by the volume pulse wave detecting device; (c) Heart rate information calculating means for calculating heart rate information related to the heart rate of the living body; (d) Pseudo cardiac output calculating means for sequentially calculating a pseudo cardiac output that is a product of the volume pulse wave area calculated by the pulse wave area calculating means and the heart rate information calculated by the heart rate information calculating means; , (e) A change value calculating means for calculating a change value of the pseudo cardiac output sequentially calculated by the pseudo cardiac output calculating means; (f) Change value display means for displaying the change value calculated by the change value calculation means on the display, (g)The change value display means displays the change value calculated by the change value calculation means in a graph on a display. In this way,When the volume pulse wave detection device detects the volume pulse wave in the peripheral part of the living body, the pulse wave area calculation means calculates the pulse wave indicating the blood flow rate in the peripheral part from the volume pulse wave detected by the volume pulse wave detection device. In the pseudo cardiac output calculating means, the product of the pulse wave area and the heart rate information calculated by the heart rate information calculating means changes in relation to the change in cardiac output. The change value is calculated sequentially, and the change value calculation means calculates the change value of the pseudo cardiac output that is sequentially calculated, and the change value display means displays the change value on the display. Accordingly, since the change value of the pseudo cardiac output that changes in relation to the change of the cardiac output is displayed on the display, the change in the cardiac output of the living body can be easily and continuously monitored. it can. Further, the change value display means displays the change value calculated by the change value calculation means in a graph on a display.There is an advantage that the magnitude of the change value, that is, the change in cardiac output can be easily recognized.
[0011]
  herePreferably, the cardiac output monitoring device is calculated by a blood pressure measuring unit that measures a blood pressure value of the living body using a cuff that changes a compression pressure to a part of the living body, and the change value calculating unit. Blood pressure measurement starting means for starting blood pressure measurement by the blood pressure measuring means based on the fact that the changed value exceeds a predetermined criterion range. In this way, when the change value of the pseudo cardiac output calculated by the change value calculation means exceeds the predetermined criterion range, the blood pressure measurement using the cuff is immediately started by the blood pressure measurement means. Therefore, there is an advantage that a blood pressure measurement value with a highly reliable cuff is automatically obtained when a change in cardiac output of the living body is determined.
[0012]
Preferably, the cardiac output monitoring device detects the pseudo cardiac output when it is determined that the change value of the pseudo cardiac output calculated by the change value calculating means exceeds a predetermined determination reference range. An abnormality display means for displaying an abnormality in the change in the stroke volume is included. In this way, abnormal values of pseudo cardiac output that change in relation to changes in cardiac output are displayed, so it is easy to recognize that the cardiac output of the living body has changed abnormally. There are advantages you can do.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram illustrating the configuration of a cardiac output monitoring device 8 to which the present invention is applied.
[0014]
In FIG. 1, the cardiac output monitoring device 8 includes a cuff 10 that has a rubber bag in a cloth band bag and is wound around, for example, a patient's upper arm 12, and a pipe 20 around the cuff 10. A pressure sensor 14, a switching valve 16, and an air pump 18 are provided. The switching valve 16 has a pressure supply state that allows supply of pressure into the cuff 10, a slow discharge state that gradually discharges the inside of the cuff 10, and a quick discharge state that rapidly discharges the inside of the cuff 10. It is configured to be switched to one state.
[0015]
The pressure sensor 14 detects the pressure in the cuff 10 and supplies a pressure signal SP representing the pressure to the static pressure discrimination circuit 22 and the pulse wave discrimination circuit 24, respectively. The static pressure discriminating circuit 22 includes a low-pass filter, and a steady pressure, that is, a cuff pressure P included in the pressure signal SP._CAnd the cuff pressure signal SK is supplied to the electronic control unit 28 via the A / D converter 26.
[0016]
The pulse wave discrimination circuit 24 includes a band pass filter, and a pulse wave signal SM that is a vibration component of the pressure signal SP.₁ And the pulse wave signal SM₁ Is supplied to the electronic control unit 28 via the A / D converter 29. This pulse wave signal SM₁ The cuff pulse wave represented by is a pressure oscillation wave that is generated from a brachial artery (not shown) in synchronism with the heartbeat of the patient and transmitted to the cuff 10, that is, the cuff pulse wave, and the cuff 10, the pressure sensor 14, and the pulse wave discrimination The circuit 24 functions as a cuff pulse wave sensor.
[0017]
The electronic control unit 28 includes a CPU 30, a ROM 32, a RAM 34, and a so-called microcomputer provided with an I / O port (not shown). The CPU 30 has a storage function of the RAM 34 according to a program stored in the ROM 32 in advance. By executing the signal processing while using it, the drive signal is output from the I / O port to control the switching valve 16 and the air pump 18 and the display content of the display 36 is controlled.
[0018]
The photoelectric pulse wave sensor 40 functioning as a volume pulse wave detection device is configured in the same manner as that used for, for example, pulse detection in order to detect a volume pulse wave (plethysmograph) of a peripheral blood vessel of a living body. In the housing 42 that can accommodate a part of a living body such as a cusp, the living body has red light or infrared light in a wavelength band that can be reflected by hemoglobin, preferably a wavelength of about 800 nm that is not affected by oxygen saturation. A light-emitting element 44 that is a light source that irradiates the skin of the skin, and a light-receiving element 46 that is provided on the side of the housing 42 that faces the light-emitting element 44 and that detects light transmitted through a part of the living body. Photoelectric pulse wave signal SM corresponding to blood volume in blood vessel₂ Is supplied to the electronic control unit 28 via the A / D converter 48. This photoelectric pulse wave signal SM₂ Is a signal that pulsates at every beat corresponding to the amount of hemoglobin in the peripheral capillaries, that is, the blood volume, so that the photoelectric pulse wave sensor 40 also functions as a heartbeat signal detection device that detects a heartbeat signal of a living body. is doing.
[0019]
FIG. 2 is a functional block diagram for explaining a main part of the control function of the electronic control device 28 in the cardiac output monitoring device 8. In FIG. 2, the blood pressure measurement means 60 starts blood pressure measurement at a preset blood pressure measurement cycle, and the cuff pressure control means 62 applies the compression pressure of the cuff 10 wound around the upper arm of the living body to a predetermined target. Pressure value P_cmThe pulse wave signal SM that is sequentially collected during the gradual step-down period in which the pressure is stepped up at a speed of about 3 mmHg / sec after the pressure is rapidly increased to (for example, a pressure value of about 180 mmHg).₁Based on the change in the amplitude of the pulse wave represented by the maximal blood pressure value BP using a well-known oscillometric method_SYS, Mean blood pressure BP_MEAN, And diastolic blood pressure BP_DIAAnd the determined systolic blood pressure BP_SYS, Mean blood pressure BP_MEAN, And diastolic blood pressure BP_DIAAre displayed on the display 36.
[0020]
The pulse wave area calculating means 64 calculates the area S of the volume pulse wave of the peripheral blood vessel detected by the photoelectric pulse wave sensor 40. Pulse wave signal SM output from the photoelectric pulse wave sensor 40₂3 pulsates for each beat as shown in FIG. 3, the pulse wave area calculating means 64, for example, the pulse wave signal SM₂The intensity of the signal is integrated at every beat or every two or more beats (pulse wave signal SM₂The pulse wave area S representing the peripheral blood flow is calculated. Alternatively, it is surrounded by a pulse wave and a line connecting from the rising point of the peak indicated by the alternate long and short dash line C to the rising point of the next peak, as shown by the preset broken line B and beyond the predetermined reference value. The area of the fluctuation component of the pulse wave may be mainly calculated by calculating the area of the range for every beat or every predetermined number of beats of two or more.
[0021]
The heart rate information calculation means 66 calculates heart rate information related to the heart beat of the living body, that is, heart rate cycle TH, heart rate HR, pulse cycle TP, pulse rate PR, and the like from the heart rate signal detected by the heart rate signal detection device. For example, the photoelectric pulse wave signal SM detected by the pulse wave sensor 40₂The heartbeat cycle TH (sec) is measured from the interval between predetermined parts of the pulse wave obtained from the above, for example, the peak interval, and the heart rate HR (times / min) is calculated from the relationship of HR = 60 / TH.
[0022]
The pseudo cardiac output calculating means 68 is a pseudo heart rate that is the product of the peripheral pulse wave area S calculated by the pulse wave area calculating means 64 and the heart rate information calculated by the heart rate information calculating means 66. The output amount SS is calculated. This pseudo cardiac output SS represents the blood flow rate per unit time that changes in proportion to the cardiac output of the living body. For example, the pulse wave area is calculated so as to represent the blood flow rate per minute. The product (= S × HR) of the pulse wave area S for one beat calculated by the means 64 and the heart rate HR (times / min) calculated by the heart rate information calculation means 66 is set as the pseudo cardiac output SS. calculate.
[0023]
The change value calculation means 70 calculates the change value ΔSS of the pseudo cardiac output calculated by the pseudo cardiac output calculation means 68. This change value ΔSS is, for example, the moving average value SS of the pseudo cardiac output._AVAlternatively, the rate of change or the amount of change with respect to the pseudo cardiac output SS determined based on the pulse wave before a predetermined number of beats. Since the pseudo cardiac output SS is proportional to the cardiac output of the living body, the change value ΔSS indicates a change in the cardiac output of the living body.
[0024]
The blood pressure measurement starting means 72 also functions as a change value abnormality determining means for determining an abnormality in the pseudo cardiac output change value ΔSS calculated by the change value calculating means 70, and the change value ΔSS is set in advance. It is determined whether or not the determined determination reference range has been exceeded, and blood pressure measurement by the blood pressure measurement means 60 is activated based on the change value ΔSS exceeding the determination reference range. For example, moving average value SS of pseudo cardiac output SS_AV[= (SS_in+ ... + SS_i-1+ SS_i) / (N + 1)] or the pseudo-cardiac output SS calculated at the time of blood pressure measurement by the previous cuff is used as a reference to determine whether the change value ΔSS is abnormal based on whether or not a predetermined value or a predetermined rate has changed. When it is determined that the value ΔSS is abnormal, blood pressure measurement by the blood pressure measurement means 60 is activated.
[0025]
The change value display unit 74 displays the pseudo cardiac output change value ΔSS calculated by the change value calculation unit 70 on the display 36. For example, a numerical value indicating the change value ΔSS is displayed, or the change value ΔSS is displayed in a graph.
[0026]
The abnormality display means 76 determines that the change value of the pseudo cardiac output calculated by the change value calculation means 70 has exceeded a preset judgment reference range, that is, a blood pressure measurement activation means (change value abnormality determination means). ) When the abnormality of the change value ΔSS is determined at 72 and the blood pressure measurement by the blood pressure measurement unit 60 is started, the abnormality of the change value ΔSS of the pseudo cardiac output is displayed. For example, a character or symbol indicating an abnormality of the pseudo cardiac output change value ΔSS is displayed on the display 36, or a sound indicating an abnormality of the change value ΔSS from a speaker (not shown) of the cardiac output monitoring device 8 or A warning sound is output.
[0027]
FIG. 4 is a flowchart for explaining a main part of the control operation of the electronic control device 28. After initial processing for clearing a counter or a register (not shown) is performed in step SA1 (hereinafter, step is omitted) in the figure, whether or not one pulse of photoelectric pulse wave, that is, one pulse wave is input in SA2. Is judged. If the determination of SA2 is negative, SA2 is repeatedly executed, but if the determination is positive, in SA3 corresponding to the subsequent pulse wave area calculation means 64, one pulse input from the photoelectric pulse wave sensor 40 in SA2 Wave signal photoelectric pulse signal SM₂Is integrated to calculate the pulse wave area S for each beat.
[0028]
In SA4 corresponding to the subsequent heart rate information calculation means 66, the peak interval of the pulse wave detected by the pulse wave sensor 40 is measured, and the heart rate HR (times / min) is calculated from the peak interval, that is, the heart rate period TH (sec). In SA5 corresponding to the calculated pseudo cardiac output calculating means 68, the product (S × HR) of the pulse wave area S calculated in SA3 and the heart rate HR calculated in SA4 is calculated. The pseudo cardiac output SS representing the blood volume per minute is calculated.
[0029]
In SA6 corresponding to the subsequent change value calculation means 70, the average value SS of the pseudo cardiac output calculated in the past one minute until the previous time of the pseudo cardiac output SS calculated in SA5._AVA change rate ΔSS (%) with respect to is calculated. That is, the average value SS of the pseudo cardiac output for the past one minute calculated in SA7 described later in the previous routine of the pseudo cardiac output SS calculated in SA5._AVThe rate of change ΔSS (%) with respect to is calculated based on Equation 1.
[0030]
[Expression 1]
ΔSS = | SS-SS_AV| / SS_AV
[0031]
In the subsequent SA7, the average value SS of the pseudo cardiac output calculated in the past one minute including the pseudo cardiac output SS calculated in the current SA5._AVThe average value SS is calculated by calculating_AVIs updated and used for calculation of the change value ΔSS in SA6 of the next routine.
[0032]
In SA8 corresponding to the subsequent change value display means 74, the change rate ΔSS (%) calculated in SA6 is displayed in a graph on the display 36. For example, as shown in FIG. 5, the rate of change ΔSS calculated sequentially is displayed on the display 36 as a trend graph, and the magnitude of the rate of change ΔSS is indicated by the slope of the arrow 78 as shown in FIG. It is. In the example shown in FIG. 6, a state in which the tip of an arrow 78 (not shown) is vertically upward is a state in which the change rate ΔSS is 0%, and FIG. 6A shows a case in which the change rate ΔSS is 20% or more. (B) is an example of a graph displayed when the rate of change ΔSS is 30% or more.
[0033]
In SA9 corresponding to the subsequent blood pressure measurement starting means, that is, the change value abnormality determining means 72, it is determined whether or not the rate of change ΔSS (%) calculated in SA6 has exceeded a preset judgment reference range, for example, 30%. . If this determination is affirmative, the cardiac output may have changed abruptly. Therefore, in SA10 corresponding to the subsequent abnormality display means 76, the display 36 displays an indication of abnormal cardiac output. For example, after the background color portion 80 of the graph of FIG. 6B is red and the characters or symbols indicating abnormal cardiac output are displayed, the cuff is performed in SA11 corresponding to the blood pressure measurement means 60 that follows. The blood pressure measurement using 10 is started, and the measured blood pressure value is displayed on the display 36. Then, after SA11 is executed, the processes after SA2 are repeatedly executed.
[0034]
However, if the determination in SA9 is negative, in SA12, whether the elapsed time from the previous blood pressure measurement by the cuff 10 has passed the preset setting period of about 20 minutes, that is, the calibration period has passed. It is determined whether or not. When the determination of SA12 is negative, SA2 and subsequent steps are repeatedly executed, and when the determination is positive, blood pressure measurement by the cuff 10 in SA11 is executed.
[0035]
As described above, according to the present embodiment, when the photoelectric pulse wave at the peripheral part of the living body is detected by the photoelectric pulse wave sensor 40, the pulse wave area calculating means 64 (SA3) causes the photoelectric pulse wave sensor 40 to A pulse wave area S indicating the blood flow rate in the peripheral portion is calculated from the detected photoelectric pulse wave, and the pseudo cardiac output calculating means 68 (SA5) calculates the pulse wave area S and heart rate information calculating means 66 (SA4). The product of the heart rate HR calculated in step 5 is calculated as a pseudo cardiac output SS that changes in relation to the change in cardiac output, and the change value calculation means 70 (SA6) changes the pseudo cardiac output. The value ΔSS is calculated, and the change value ΔSS is displayed on the display 36 by the change value display means 74 (SA8). Therefore, since the pseudo cardiac output change value ΔSS that changes in relation to the change in cardiac output is displayed on the display 36, the change in the cardiac output of the living body can be monitored easily and continuously. be able to.
[0036]
Further, according to the present embodiment, the change value display means 74 (SA8) displays the change value ΔSS calculated by the change value calculation means 70 (SA6) in a graph on the display 36. There is an advantage that the magnitude of ΔSS, that is, the change in cardiac output can be easily recognized.
[0037]
In addition, according to the present embodiment, the cardiac output monitoring device 8 includes the blood pressure measuring means 60 (SA11) that measures the blood pressure value of the living body using the cuff 10 that changes the pressure applied to a part of the living body. The blood pressure measurement starting means 72 for starting the blood pressure measurement by the blood pressure measuring means 60 (SA11) based on the fact that the change value ΔSS calculated by the change value calculating means 70 (SA6) exceeds a preset criterion range. When the change value ΔSS calculated by the change value calculating means 70 (SA6) exceeds a preset judgment reference range, the cuff 10 by the blood pressure measuring means 60 (SA11) is removed. Since the used blood pressure measurement is started immediately, there is an advantage that a highly reliable blood pressure measurement value by a cuff is automatically obtained when a change in cardiac output of the living body is determined.
[0038]
Further, according to the present embodiment, the abnormality display means 76 (SA10) determines that the change value ΔSS of the pseudo cardiac output calculated by the change value calculation means 70 (SA6) exceeds 30%. The abnormal change in the pseudo cardiac output SS is displayed on the display 36. Therefore, since the abnormality of the change value ΔSS of the pseudo cardiac output that changes in relation to the change of the cardiac output is displayed, it is possible to easily recognize that the cardiac output of the living body has changed abnormally. is there.
[0039]
FIG. 7 shows an example of a cardiac output monitoring device in which a photoelectric pulse wave detection probe 90 of a pulse oximeter 88 for measuring blood oxygen saturation is used as a volume pulse wave detection device. The pulse oximeter 88 includes a photoelectric pulse wave detection probe 90 (hereinafter simply referred to as a probe) in order to measure blood oxygen saturation. The probe 90 is mounted in a state of being in close contact with a body surface 38 such as a patient's forehead by a mounting band (not shown) or the like. The probe 90 is provided in a container-shaped housing 92 that opens in one direction, and a portion located on the outer peripheral side of the bottom inner surface of the housing 92, and includes a plurality of first light-emitting elements 94a and second light-emitting elements 94b made of LEDs or the like. (Hereinafter simply referred to as a light emitting element 94 unless otherwise specified), a light receiving element 96 provided at the center of the inner surface of the bottom of the housing 92, and a light receiving element 96 made of a photodiode, a phototransistor, etc. A transparent resin 98 that covers the light emitting element 94 and the light receiving element 96, and a light emitting element 94 that is provided between the light emitting element 94 and the light receiving element 96 in the housing 92. An annular shielding member 100 that shields reflected light from the body surface 38 toward the light receiving element 96 is provided.
[0040]
The first light emitting element 94a emits red light having a wavelength of about 660 nm, for example, and the second light emitting element 94b emits infrared light having a wavelength of about 800 nm, for example. The first light emitting element 94a and the second light emitting element 94b are caused to emit light alternately at a predetermined frequency according to the driving current from the driving circuit 101, and the light emitted from the light emitting elements 94 toward the body surface 38 is emitted. The reflected light from the part where the capillaries in the body are densely received is received by the common light receiving element 96.
[0041]
The light receiving element 96 has a photoelectric pulse wave signal SM having a magnitude corresponding to the amount of light received._Three Is output via the low-pass filter 102. An amplifier or the like is appropriately provided between the light receiving element 96 and the low-pass filter 102. The low-pass filter 102 receives the input photoelectric pulse wave signal SM._Three From which the noise having a frequency higher than the frequency of the pulse wave is removed, and the signal SM from which the noise is removed_Three Is output to the demultiplexer 104. The demultiplexer 104 is switched in synchronization with the light emission of the first light emitting element 94a and the second light emitting element 94b in accordance with the signal from the electronic control unit 28, whereby the electric signal SM based on red light_RThrough the sample and hold circuit 106 and the A / D converter 109, the electric signal SM by infrared light_IRAre sequentially supplied to an I / O port (not shown) of the oxygen saturation measurement electronic control unit 112 via the sample hold circuit 108 and the A / D converter 110, respectively. The sample and hold circuits 106 and 108 are connected to the input electric signal SM._R, SM_IRIs output to the A / D converters 109 and 110 sequentially, the electrical signal SM output last time_R, SM_IRNext, the electric signal SM to be output until the conversion operation in the A / D converters 109 and 110 ends._R, SM_IRIs for holding each. The electronic control unit 112 is connected to a display (not shown) for displaying the blood oxygen saturation.
[0042]
The electronic control unit 112 is a microcomputer that includes a CPU 114, a RAM 116, a ROM 118, and the like and can communicate with the electronic control unit 28. The CPU 114 uses a storage function of the RAM 116 and follows a program stored in the ROM 118 in advance. The measurement operation is performed, and the electric signal SM_R, SM_IRThe oxygen saturation is calculated and displayed in accordance with the electric signal SM representing the waveform as shown in FIG._ROr SM_IRAre sequentially output to the electronic control unit 28 as a volume pulse wave.
[0043]
The method for calculating the oxygen saturation is the same as the determination method described in Japanese Patent Laid-Open No. 3-15440, which was filed and published by the present applicant earlier, for example, {(V_dR-V_SR) / (V_dR+ V_SR)} / {(V_dIR-V_SIR) / (V_dIR+ V_SIR)} And the oxygen saturation is determined based on the actual ratio from the relationship obtained in advance between the ratio and the oxygen saturation. In the above formula, V_dR, V_SRAre respectively the upper peak value and the lower peak value of the photoelectric pulse waveform by red light, and V_dIR, V_SIRAre the upper peak value and lower peak value of the photoelectric pulse waveform by infrared light, respectively. Also, V_dR-V_SRAnd V_dIR-V_SIRRepresents the amplitude of the AC component of each photoelectric pulse waveform, and V_dR+ V_SRAnd V_dIR+ V_SIRRepresents the doubled DC component of each photoelectric pulse waveform.
[0044]
As mentioned above, although one Example of this invention was described based on drawing, this invention is applied also in another aspect.
[0045]
For example, in the above-described embodiment, the photoelectric pulse wave sensor 40 or the photoelectric pulse wave detection probe 90 for measuring oxygen saturation is used as the volume pulse wave detection device. However, even if an impedance pulse wave sensor is used. Good. This impedance pulse wave sensor includes at least two electrodes that are brought into contact with the epidermis of a living body at a predetermined interval, and outputs an impedance pulse wave corresponding to the blood volume of a living tissue located between the two electrodes. Configured as follows.
[0046]
In the above-described embodiment, the photoelectric pulse wave sensor 40 and the photoelectric pulse wave detection probe 90 that function as a volume pulse wave detection device also function as a heartbeat signal detection device, but are wound around the upper arm 12 of the living body. The cuff pulse wave may be detected continuously by supplying pressure to the upper cuff 10 so as to slightly press the upper arm 12, and the cuff pulse wave may be used as a heartbeat signal. A guidance device, a heart sound microphone, or the like may be provided as the heartbeat signal detection device.
[0047]
In the blood pressure measurement means 60 (SA11) of the above-described embodiment, blood pressure measurement is executed every predetermined blood pressure measurement cycle and when the blood pressure measurement activation means 72 (SA9) determines that the blood pressure measurement is activated. However, the blood pressure measurement may be performed only when the blood pressure measurement is not performed for each blood pressure measurement cycle and the blood pressure measurement activation unit 72 (SA9) determines that the blood pressure measurement is activated.
[0048]
Further, the blood pressure measuring means 60 (SA11) of the above-described embodiment determines the blood pressure value based on the change state of the magnitude of the pressure pulse wave that changes with the compression pressure of the cuff 10 according to the so-called oscillometric method. However, according to the so-called Korotkoff sound method, the blood pressure value may be determined based on the Korotkoff sound that is generated and disappears with the compression pressure of the cuff 10.
[0049]
Further, the pseudo cardiac output calculating means 68 (SA5) described above calculates the product (S × HR) of the heart rate HR and the pulse wave area S as the pseudo cardiac output SS, but the cardiac cycle TH The product (S / TH) of the reciprocal (1 / TH) of (sec) and the pulse wave area S may be calculated as the pseudo cardiac output.
[0050]
In the above-described embodiment, the abnormality of the change value ΔSS is determined for each pulse wave. However, the abnormality may be determined for each predetermined number of beats of two or more.
[0051]
In the above-described embodiment, the change value display means 74 (SA8) changes the slope of the arrow 78 indicating the change rate ΔSS stepwise for each change rate ΔSS in the predetermined range. It may be changed continuously corresponding to.
[0052]
Further, the change value ΔSS calculated by the above-described change value calculation means 70 (SA6) is the average value SS of the direction of change, that is, the pseudo cardiac output SS sequentially calculated._AVThe pseudo cardiac output SS and the average value SS calculated sequentially are not distinguished._AVIt is also possible to calculate a change value ΔSS that is also distinguished from each other.
[0053]
In addition, the present invention can be variously modified without departing from the gist of the present invention.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a cardiac output monitoring apparatus according to an embodiment of the present invention.
2 is a functional block diagram for explaining a main part of a control function of the electronic control device of the embodiment of FIG. 1; FIG.
FIG. 3 is a diagram for explaining a photoelectric pulse wave detected by the photoelectric pulse wave sensor of the embodiment of FIG. 1;
FIG. 4 is a flowchart illustrating a main part of a control operation of the electronic control device of the embodiment of FIG. 1;
FIG. 5 is a diagram showing a trend graph of change values displayed on the display of the cardiac output monitoring apparatus of FIG. 1;
6 is a diagram showing an example of a graph of change values displayed on the display of the cardiac output monitoring apparatus of FIG. 1; FIG.
FIG. 7 is a diagram showing a main part of a cardiac output monitoring device which is another embodiment of the present invention and includes a photoelectric pulse wave detection probe of an oximeter as a volume pulse wave detection device.
[Explanation of symbols]
8: Cardiac output monitoring device
36: Display
40: photoelectric pulse wave sensor (volume pulse wave detection device, heart rate signal detection device)
64: Pulse wave area calculation means
66: Heart rate information calculation means
68: Pulse wave area normalization means
70: Change value calculation means
72: Blood pressure measurement starting means (change value abnormality determining means)
74: Change value display means
76: Abnormal display means

Claims (2)

A cardiac output monitoring device for monitoring cardiac output of a living body,
A volume pulse wave detecting device for detecting a volume pulse wave at a peripheral portion of the living body;
Pulse wave area calculating means for calculating the area of the volume pulse wave detected by the volume pulse wave detecting device;
Heart rate information calculating means for calculating heart rate information related to the heart rate of the living body;
Pseudo cardiac output calculating means for sequentially calculating a pseudo cardiac output that is a product of the volume pulse wave area calculated by the pulse wave area calculating means and the heart rate information calculated by the heart rate information calculating means; ,
Change value calculation means for calculating a change value of the pseudo cardiac output sequentially calculated by the pseudo cardiac output calculation means;
A cardiac output monitoring apparatus comprising: a change value display means for displaying a change value calculated by the change value calculation means on a display. A cardiac output monitoring device for monitoring cardiac output of a living body,
A volume pulse wave detecting device for detecting a volume pulse wave at a peripheral portion of the living body;
Pulse wave area calculating means for calculating the area of the volume pulse wave detected by the volume pulse wave detecting device;
Heart rate information calculating means for calculating heart rate information related to the heart rate of the living body;
Pseudo cardiac output calculating means for sequentially calculating a pseudo cardiac output that is a product of the volume pulse wave area calculated by the pulse wave area calculating means and the heart rate information calculated by the heart rate information calculating means; ,
Change value calculation means for calculating a change value of the pseudo cardiac output sequentially calculated by the pseudo cardiac output calculation means;
Change value display means for displaying the change value calculated by the change value calculation means on a display,
The change value display means, cardiac output monitoring apparatus, characterized in that is for displaying graphs display the change value change value calculated by the calculating means.

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