JPH0467854B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a cardiac output measuring device used when performing a cardiac function test.

[Prior Art] Conventionally, an indicator dilution method has been used to measure cardiac output by right heart catheterization for cardiac function testing. This indicator dilution method includes a thermodilution method that calculates cardiac output from heat diffusion, a dye dilution method that calculates cardiac output from changes in illuminance due to dye diffusion, and a method that calculates cardiac output from changes in resistance due to electrolyte diffusion. There are electrolyte dilution methods to determine the amount. This thermodilution method will be explained.

In right heart catheterization, as shown in Figure 16, a catheter 4 is introduced from the jugular vein, femoral vein, cubital vein, etc., passes through the superior vena cava or inferior vena cava, the right atrium, and the right ventricle. is placed in the pulmonary artery. Catheter 25
In this case, the discharge port 26 is located in the right atrium, and the thermistor 1 is located in the pulmonary artery. Now, when a liquid with a temperature higher or lower than the blood temperature is injected into the right atrium from the discharge port 26,
The fluid is diffused and diluted in the right atrium and right ventricle. The temperature of this diluted liquid is detected by the thermistor 27 located in the pulmonary artery, and the dilution curve (diagram of temperature change with respect to time) of the temperature (first
Calculate the cardiac output using the following formula (1) using the Stewart-Hamilton method from the area shown in Figure 7).

CO＝S _i・C _i・(T _b −T _i )・V _i ／S _b・C _b・∫ ^∞ / _p △T _b d
t……(1) where, CO: cardiac output, S _i : specific gravity of injected liquid, C _i : specific heat of injected liquid, V _i : amount of injected liquid, T _i : temperature of injected liquid, T _b : blood Temperature S _b : specific gravity of blood, C _b : specific heat of blood ∫ ^∞ _p △T _b dt: area of thermodilution curve.

[Problems to be Solved by the Invention] In the thermodilution method described above, as can be seen from the formula for calculating cardiac output, the amount of indicator fluid injected and its temperature greatly affect the accuracy of the calculated value. . By the way, normally, the liquid temperature Ti is accurately measured with a thermistor, etc., and then the catheter 26 is primed and the indicator liquid is injected into the blood vessel. Otherwise, it may be heated, causing an error in the measured value. Therefore, in the past, the amount of fluid remaining in the catheter was estimated from the outer diameter of the catheter (French size), the amount of fluid injected, etc., and compared with the experimentally obtained cardiac output value. A correction constant was determined, and this correction constant was applied to the calculation of cardiac output to reduce the influence of the residual fluid.

On the other hand, in the method for measuring cardiac output using the thermodilution method or indicator dilution method described above, cardiac output is measured intermittently every time the indicator liquid is injected. It cannot be used to measure output. Furthermore, if measurements are to be performed frequently, the total amount of liquid to be injected increases, which increases the burden on the subject, and at the same time increases the risk of infection associated with the liquid injection operation, which is undesirable.

In order to eliminate the disadvantages associated with cardiac output measurement according to the conventional indicator dilution method, in particular the thermodilution method, which allows only one-shot measurement, the applicant of the present invention filed a patent application filed in Japanese Patent Application No. No. 244586 (Unexamined Japanese Patent Publication No. 61-125329)
We proposed a completely new cardiac output measuring device that enables continuous cardiac output measurement.

Now, in the measurement of cardiac output based on the thermodilution method described above, the temperature of the injected indicator liquid is measured, but this indicator liquid is usually an ice cream or a heated liquid that is kept at a predetermined temperature. can be immersed in a drug solution. Therefore, if an experienced measurement person or absolutely accurate measurement of cardiac output is not required, the above solution temperature may be considered as the indicated liquid temperature Ti. If it is possible to do so, there will be no need to measure the indicated liquid temperature, and the work to measure cardiac output will become more efficient.

Therefore, the present invention has been proposed in order to eliminate the drawbacks of the conventional examples described above, and its purpose is to enable the actual measurement of indicator liquid data as well as the input of pseudo data of the indicator liquid, and to enable the actual measurement data and pseudo data to be input. An object of the present invention is to propose an easy-to-operate cardiac output measurement device that is capable of selecting one of the data and calculating the cardiac output using the selected data.
The measuring device of the present invention automatically detects whether or not a probe that detects data regarding the indicator liquid is connected to the measuring device main body, and automatically uses actual measurement data and pseudo data depending on this detection. This further improves operability.

[Means and effects for solving the problems] The configuration of the cardiac output measuring device of the present invention for achieving the above-mentioned problems is that it is removable from the main body of the measuring device, and that an indicator liquid data detection probe that detects data related to the indicator liquid; a blood data detection means that detects and outputs blood data diluted by the indicator liquid injected into a blood vessel; an integrating means for integrating the difference value between the reference blood data and the reference blood data;
an input means for setting arbitrary data and inputting it as a pseudo value of data related to the indicator liquid; and determining whether or not the probe is connected to the main body of the measuring device, and if it is not connected, a selection means for selecting data inputted as pseudo data from the input means, and selecting the indicator liquid data outputted by the indicator liquid data detecting means when connected; The present invention is characterized by comprising a cardiac output calculation means for calculating cardiac output based on the integral value.

The operator disconnects the probe when accurate cardiac output is not required and connects it when necessary. The selection means recognizes the operator's intention from the connection state of the probe and automatically selects one of the data. The cardiac output calculating means calculates cardiac output using the selected data.

[Examples] Examples according to the present invention will be described in detail below with reference to the accompanying drawings.

[External Appearance of Example Device] FIGS. 1A to 1C are plan views of a continuous measurement and recording device for cardiac output to which the present invention is applied, respectively.
A front view and a back view are shown. Figure 2A shows the external appearance of the catheter connected to this measuring device.
Figure B shows a cross-sectional view along the longitudinal direction of the distal end portion of this catheter, and Figure 2C shows a cross-sectional view of the opening of the catheter.

The principle of this measuring device is to measure the initial cardiac output CO based on an indicator dilution method such as thermodilution method, electrolyte dilution method, dye dilution method, etc., and to measure the blood flow velocity v when this cardiac output is measured. is measured, and then a parameter S that connects this blood flow velocity v to the cardiac output CO is determined. After determining this parameter, by simply measuring the blood flow velocity v _i at any time, the cardiac output CO _i at any time can be determined from this blood flow velocity v _i and the parameter S. . The measuring method for determining the initial cardiac output CO may be any of the indicator dilution methods described above, but the embodiments shown in FIG. 1A and subsequent figures are particularly based on the thermodilution method.

The external appearance of the measuring device 100 shown in FIGS. 1A to 1C will be explained. FIG. 1A is a top view of apparatus 100. 50 is a well-known printer. This plotter 50 outputs measurement results and the like. 52,
Reference numeral 53 designates a switch for specifying the output mode on the plotter 50 when measuring the initial cardiac output value CO by the thermodilution method. The switch 52 specifies that CO is to be output as a numerical value (FIG. 5). The switch 53 specifies that the change in blood temperature _Tb , etc. be output as a curve (FIG. 4). Switches 57 and 58 control the paper feed speed of plotter 50 (20
mm/hour and 10mm/minute).

54 plots the progress of CO _i etc. for 12 hours.
The switch 55 instructs the output (Fig. 8) to the top, and the switch 55 outputs data such as CO _i stored in the memory for the past 30
Output on plotter 50 for minutes (Figs. 6 and 7)
This is a switch that instructs you to do the following: 80 is a memo switch, and when this switch is pressed, the memory paper is fed about 6 cm. 56 is CO _i ,
This is a switch that instructs to output changes in T _b , V _{i ,} etc. on recording paper in real time (Figs. 6 and 7).

Switches 59, 60 (Fig. 1A), 61, 62
(FIG. 1B) etc. are switches for manually setting desired data when inputting it into the device 100, and the setting value is as follows.
Catheter diameter (unit: French), injection volume of indicated liquid (unit: ml), body surface area (unit: m ² ), initial
CAL value (unit: L/min).

64 is a switch that sets the mode of the measuring device to continuous mode, and at the same time, when the mode is set to continuous mode,
This switch/indicator 64 lights up.
Reference numeral 65 denotes a single (intermittent) mode switch/indicator, which is mainly used when returning from continuous mode to single mode when it is desired to set parameter S again. Lights up when the mode is in intermittent mode (SINGLE mode). Display 68 is a four-digit LED that digitally displays cardiac output.
Switches 66 and 67 are 3-digit LED display 69
This is for specifying whether the temperature displayed is to be the blood temperature T _b or the temperature T _i of the indicator liquid.

The ENTRY switch/indicator 70 indicates that the measurement of the initial cardiac output value CO has been completed by the thermodilution method, and that it is now possible to register (ENTRY) the CO as data. this
When the switch 70 is pressed while the ENTRY indicator 70 is lit, the CO is registered as data. This registration is performed using the initial cardiac output value CO by the thermodilution method in order to obtain the parameter S.
This is because the measurement is performed several times, and the measurer determines and registers the data that seems reliable, and the average value of the registered data is used as CO.

The START switch/indicator 72 indicates that preparation for thermodilution initial cardiac output value CO measurement is complete, and pressing the switch at that point starts integration based on the Stuart-Hamilton equation.

The display 71 is a bar graph, and mainly displays the value of blood temperature T _b in real time.

73 and 74 are the connector 15 of the catheter 4 (FIG. 2A) which has a built-in blood temperature sensor, and the temperature probe 12 (second
This is a connector for connecting the connector 16 shown in Figure A).

Switch 75 in FIG. 1C is a rotary switch that manually sets the temperature of the injectate. 76 is an RS232C interface connector for communicating with other external measuring devices, 78 is a blood temperature T _b to (or from) other external measuring devices;
Terminal 77 is a connector for connecting a power cable to a terminal for outputting analog signals such as blood flow velocity v _{i and} cardiac output CO _i .

[Functions of the measuring device] The features of the embodiment device shown in FIGS. 1A to 1C and 2A to 2C are as follows: In order to correct the influence of the indicator liquid remaining in the catheter, Instead of the measurer using a table to find values determined in advance based on experimental results, the measurer creates a table of correction constants in advance and uses the table as data to access. A switch 59 for setting and inputting the inner diameter size (unit: French) of the catheter used for injecting the indicator liquid and a switch 60 for setting and inputting the amount of liquid to be injected (unit: ml).
It is provided in this measuring device.

: After injecting the indicator liquid into the blood vessel, the change in blood temperature T _b is automatically recognized without any intervention from the measuring person, and the integration based on the above Stewart-Hamilton equation (1) is started. .

: In order to measure the temperature of the indicator liquid, the temperature probe 12 is used, but if the connector 16 of this probe 12 is not connected to the measuring device 100, this disconnection is detected and the switch 75 ( Input the value set in Fig. 1C) as the indicated liquid temperature T _i .

: Once CO is measured by thermodilution method and parameter S is determined, CO _i , blood temperature T _b , blood flow velocity v _i, etc. are continuously stored in memory and recorded on recording paper as necessary. Output. The mode of output is as follows: (): The measured CO _i , etc. are output on the recording paper of the plotter 50 in approximately real time (Fig. 6,
Figure 7). This is the "continuous record" switch 56
This is done by pressing .

(): The past 30 minutes stored in memory.
Data such as CO _i is reproduced and output (Figures 6 and 7). This is done by pressing switch 55.

(): Data such as CO _i for the past 12 hours is compressed and reproduced and output on the plotter 50 (Fig. 8).
This is convenient when measuring data on a patient who requires rest and noiselessness because the printer does not make any printing noise.

: By manually setting the parameter S via the switch 62, CO _i can be continuously determined from this S and the blood flow velocity v _i . This is useful when you want to know the relative changes in CO _i .

: With the bar graph display 71, changes in blood temperature T _b can be visually confirmed when calculating the initial cardiac output value CO using the thermodilution method. In particular, this bar graph displays the blood temperature baseline (reference temperature value) in addition to displaying temperature changes moment by moment.
T _bp ) and maximum temperature T _bnax can be fixed and displayed.

:This device is equipped with a battery (14 in Figure 9) to protect the stored data from failures such as power outages.
8) is built-in. When the output voltage of the battery 148 drops, the LED 78 is blinked to alert the user.

: To an external measuring device other than this measuring device 100,
Analog output circuits 142 and 151 are provided for outputting CO _i and the like as analog signals from a terminal 78.

: To an external measuring device other than this measuring device 100,
It is equipped with a circuit 144 that outputs CO _i etc. as a digital signal through an RS232 interface.

[Structure of Catheter] FIG. 2A shows a catheter incorporating a thermistor for measuring blood temperature T _b for the thermodilution method, a thermistor for measuring blood flow velocity v, and the like. In the figure, catheter 4 is configured to have four lumens. This catheter 4
is a pressure detection port 18 provided at the tip, a balloon 17 made of a flexible elastic body attached several mm back from the tip so as to cover the entire tip of the catheter tube, and the balloon 17 is inflated and deflated. There is a balloon side hole 25 provided on the side of the tube inside the balloon for injecting or extracting air, preferably carbon dioxide gas, and a hole 10 to 20 mm from the tip.
Thermistor 1 is located at the position of
Furthermore, it has a discharge port 3 provided at a position spaced apart from the thermistors 1 and 2 in a range of 8.5 to 38 cm, and spaced apart from the tip in a range of 12 to 40 cm. The thermistor 1 is used to measure the thermal equilibrium temperature for measuring the blood flow velocity v (v _i ). Thermistor 2 is used to measure the diluted blood temperature T _b which is necessary to measure the initial cardiac output CO by thermodilution. The discharge port 3 is for discharging an indicator liquid.

The catheter 4 shown in Fig. 2A is inserted into the jugular vein, femoral vein, or cubital vein, and is used in the pulmonary artery via the femoral vein or inferior vena cava, the right atrium, and the right ventricle. Considering that the flow direction is from the proximal end of the catheter to the distal end, the thermistor 2 is provided closer to the distal end (ie, downstream of the blood flow) when viewed from the discharge port 3. On the other hand, in the case of a catheter that is conduited from a peripheral artery and used in the aorta, the thermistor 2 is placed on the proximal end side of the catheter when viewed from the discharge port 3 because the blood flow direction is opposite. Become.

FIG. 2B shows a sectional view of the main part of the catheter 4.
In the figure, pressure detection port 18, balloon side hole 2
5. The thermistors 1 and 2 and the discharge port 3 communicate with the four lumens, respectively. These four lumens are a pulmonary artery pressure lumen 19 that transmits the pressure of the pulmonary artery, a balloon lumen 20 that is an air passage that inflates and deflates the balloon 17, a thermistor 1,
2 and their lead wires, and an injection lumen 23 through which an indicator liquid for dilution is passed. Furthermore, these four lumens are independent, and are further connected to a pulmonary artery pressure measuring tube 8, a balloon tube 6, a thermistor tube 12, and an indicator fluid injection tube 10 at the rear end of the catheter, as shown in FIG. 2A. ing. Each tube 8, 6, 10 is provided with a connector 7, 9, 11 at its rear end. The thermistor tube 12 is connected to a connector 15, and lead wires 22 and 24 connected to the thermistors 1 and 2, respectively, are passed through the tube.

Furthermore, the catheter of the embodiment shown in FIGS. 2A to 2C will be described in detail. FIG. 2B is an enlarged cross-sectional view of the thermistor 1, thermistor 2, and the balloon 17, and FIG. 2C is a cross-sectional view of the catheter tube 4 taken along the - line. As mentioned above,
As shown in FIG. 2C, the four-lumen structure of this catheter includes a balloon lumen 20, a pulmonary artery pressure lumen 19, an injection lumen 23 (FIG. 2C), and a thermistor lumen 21. The balloon lumen 20 has a balloon side hole 25 and communicates with the balloon tube 6. Pulmonary artery pressure lumen 1
9 has a pressure detection port 18 and communicates with the pulmonary artery pressure measurement tube 8 . The injection lumen 23 has a discharge port 3 located 12 to 40 cm from the tip of the catheter and communicates with the indicator liquid injection tube 10 on the proximal side. Furthermore, the thermistor lumen 21 has side holes 26, 1 to 2 cm away from the tip, and 1 to 1.5 cm away from the tip toward the base, respectively, with thermistors 1 and 2 installed therein.
27, and also incorporates thermistor lead wires 22, 24 from thermistors 1, 2, and communicates with the thermistor tube 13 on the base side.

It is more preferable that the thermistor 1 be a self-heating type thermistor and be located downstream of the thermistor 2 in the blood flow direction. That is, when measuring cardiac output with the catheter 4, it is necessary to accurately measure the temperature of the blood flow diluted by the thermistor 2, and the thermistor 2 is made less susceptible to the influence of the thermistor 1, which is a self-heating type. It's for a reason.

The characteristics of the thermistor 1 used in the catheter of the example are B _25-45 = 3500K, R(37) = 1000Ω,
Its size is 1.18 ¹ × 0.4 ^w × 0.15 ^t (unit: mm). The characteristics of thermistor 2 are B _25-45 = 3980K,
R (37) = 40KΩ, its size is 0.50 ¹ × 0.16 ^w × 0.15 ^t
It is. The thermistor 1 preferably generates a heat value of 0.01 to 50 joules; a higher heat value may raise the blood temperature or even damage the blood vessel wall if it comes into contact with it, and a lower heat value is preferred. Either amount is not preferable because the detection sensitivity becomes low.

[Operating Procedures for the Measuring Device] In order to better understand this measuring device, please refer to Section 1A.
The operating procedure from the operator's side will be explained using FIG. 1B, FIG. 3, and FIG.

First, in step S1, the injected liquid temperature probe 12 is
is connected to the measuring device main body 100. Step S2
Then, the temperature probe 12 is immersed in the vicinity of the injection instruction liquid in an ice-cooled container (provided in the measuring device 100 in this embodiment). This liquid may be physiological saline or the like. After priming the catheter 4 in step S3, it is inserted up to the pulmonary artery in step S4. The catheter 4 is inserted through a vein in the upper or lower limb, and placed in the pulmonary artery. Next, in step S5, the connectors of the catheter shown in FIG. 2A are connected to the main body of the device. When these connectors are connected to the device, first, the indwelling position of the catheter 4 in the blood vessel is detected from the arteriovenous pressure, right atrial pressure, and right ventricular pressure via the pressure detection port 18, tube 8, and connector 9. Confirm based on blood pressure value and pressure waveform. After the catheter is indwelled, the pulmonary artery pressure is measured, and the balloon 17 is inflated to occlude the pulmonary artery to determine the pulmonary artery wedge pressure. In this way, the catheter 4 is left in place.

Next, in step S6, predetermined values are set using the switches 59-61. The switch 62 is set when measuring the relative CO _i (described later), and its setting is necessary when measuring the initial cardiac output value CO by the thermodilution method, which will be explained now. There is no.

In step S7, the measuring device is powered on. While confirming that there is no abnormal display (indicating a device failure) in step S8, the process waits for the SINGLE indicator 65 to light up in step S9. When the indicator 65 lights up, the BLOOD indicator 66 lights up and the display 69 displays the blood temperature T _b in the pulmonary artery. If you want to know the temperature of the injectate at this point, press the INJECTATE switch 67, and the display on the display 69 will change to the display of the injectate temperature T _i . In addition, this T _i display will change after 30 seconds have passed.
The display automatically returns to the BLOOD display, and the display 69 displays T _b again. This way automatically T _b
The reason for returning to the display is that T _b is more meaningful information for the operator. On the other hand, the bar graph display 7 at this point
1 should display the baseline of the blood temperature T _b .

Furthermore, in step S10, the program waits for the START indicator 72 to light up. When this indicator lights up, the thermodilution initial cardiac output CO
This means that you are ready to start measuring. In step S11, the mode of information to be output to the plotter 50 is selected by the switch 52 or 53, if necessary. In step S12, the pot 11 is opened and liquid is injected into the blood vessel.

After liquid injection, the measuring device automatically reads the change in T _b and determines the optimal time to start integration. If the operator presses the START switch 72 before detecting this optimum point, the integration of T _b starts from the point at which the operator presses the START switch 72. If switch 72 is not pressed,
Integrate T _b data from the time determined by the device itself. The measurement calculation of CO by this thermodilution method is usually
The process ends in about ten seconds, but the changes during that time are stored in a predetermined memory (RAM 132 in FIG. 9).
It is displayed on the display 69 and bar graph display 71. Furthermore, if switch 53 was pressed,
Changes in blood temperature T _b as shown in Figure 4 are plotter 5.
Output to 0. These displays allow the operator to confirm that the device is operating normally. In FIG. 4, the blood temperature T _b is moving upward toward the negative side. In addition, for the convenience of the measurer, the following information is shown on this graph.
The date, time, etc. will be output together. still,
The output example in FIG. 4 has an output speed of 300 mm/min.

When the measurement of CO by thermodilution is completed, the value is displayed digitally on the display 68, and if the switch 52 has been pressed, the plotter 50 is displayed.
The measurement results are output as shown in FIG. In this Fig. 5, in addition to the date and time, the cardiac output CO and the body surface area input from the switch 61 are shown.
BSA, blood temperature BT (=T _b ), catheter inner diameter
CAT (=Fr), indicated fluid injection volume IV (=V _i ), cardiac index
CI (=CO/BSA), injected solution temperature IT (=T _i ), and the display of **ENTRY** indicating that it has been registered are also recorded. When CO measurement is completed,
ENTRY indicator 70 lights up (step
S15) can be confirmed.

If the measurer determines that the obtained data such as CO is reliable, he or she presses the ENTRY switch 70 to register this data (step S17). After a while, the START indicator 72 lights up again. Now, by thermodilution method,
The measurement of the initial cardiac output CO ends.

If you want to obtain more accurate CO, repeat the operations from step S11 onwards to obtain a plurality of measurement data. Press the ENTRY switch 70 for each measurement, register the
From the CO value, determine the initial cardiac output CO value.

Once sufficiently reliable CO data has been obtained in the manner described above, it is time to begin continuous CO _i measurements. This is done by simply pressing the CONTINUOUS switch 64 at the end. This switch 6
Press 4 to display CONTINUOUS indicator 6.
4 lights up and the entire measuring device enters continuous measurement mode. Furthermore, when the SINGLE switch 65 is pressed,
The measuring device is again in intermittent mode.

When the device is in continuous measurement mode and the continuous recording switch 56 is pressed, blood temperature BT (=T _b ), CO (=CO _i ), and blood flow velocity v are measured as shown in FIGS. 6 and 7.
(v _i ) is output on the plotter 50. Figure 6 is
At a paper feed speed of 10 mm/min, Figure 7 shows the output at a paper feed speed of 20 mm/hour. Although not shown in FIGS. 6 and 7, it goes without saying that various data such as the date shown in FIG. 5 are output together with the graph. In addition, in the example shown in Figure 7, the thermodilution method was used to measure the initial cardiac output and CO value again at around 4:30 pm, so changes in the graph appear around that time. There is.

[Configuration of Measuring Device] The entire measuring device 100 with the catheter 4 and the injectate temperature probe 12 connected is as shown in FIG. This measuring device consists of two electrically isolated measuring circuits 120 and 130.
It consists of The circuit 120 mainly converts electrical signals (voltage) from the thermistors 1 and 2 in the catheter 4 and the thermistor 12a in the probe 12 into temperature data, and sends the data to the measurement recording circuit 130 via the optical communication circuit 108. send. Measurement recording circuit 130
calculates the initial cardiac output value CO, blood flow velocity v, parameter S, continuous cardiac output CO _i, etc. from the temperature data from the measurement circuit 120, and displays them on the plotter 50 or on various displays. Execute what you want to display. The local CPU 1 controls the measurement circuit 120.
05. The main controller controls the measurement recording circuit 130.
It is CPU133.

[Measurement circuit 120] Now, the catheter type sensor 150 shown in FIG. 9 uses the catheter 4 shown in FIG. It has a built-in thermistor 2 that detects the blood temperature inside the body. This catheter-type sensor 150 is introduced to the pulmonary artery by right heart catheterization in the same manner as described above. Connector 1 of sensor 150
5 is coupled to the connector 73 of the main body 100. The thermistor 2 is connected to the thermistor 2 via the lead wire 24.
It is connected to a constant voltage circuit 112 that drives the blood and a blood temperature detection circuit 113 that measures the temperature of the blood.

The pulmonary artery blood temperature signal detected by the thermistor 2 is detected by the blood temperature detection circuit 113 as a voltage signal E _b . On the other hand, thermistor 1 is
It is connected to a thermistor temperature detection circuit 115 and a constant current circuit 111 via a lead wire 22 .
Then, a predetermined current I _c is supplied to the thermistor 1 from the constant current circuit 111, and the thermistor 1 is heated. Further, the temperature signal detected by the thermistor 1 is sent to the thermistor temperature detection circuit 115, and this detection circuit 1
15, it is detected as a voltage _Et . The thermistor 12a in the injected liquid temperature probe 12 is driven by a constant voltage circuit 101, and its temperature change is detected by the circuit 10.
2, it is detected as a voltage value E _i . thus,
The local CPU 105 has three thermistors 12
The output voltages E _i , E _t , and E _b from a, 1, and 2 are converted into the temperature T _i of the infusion liquid, the resistance R _t of thermistor 1, the temperature T _t of thermistor 1, and the blood temperature T _b .

This operation will be explained in more detail. local
The CPU 105 drives an analog switch 103 having a multiplexer function, and uses time division to
E _i , E _t , and E _b are input to the A/D converter 104, and the above voltage values are sequentially taken into the RAM 107 as digital values. These voltage values are converted into temperature data from a voltage-temperature conversion table stored in the ROM 106. Further, the resistance value R _t of the thermistor 1 is calculated by R _t =E _t /I _c . Here, I _c is the current flowing through the thermistor. The local CPU 105 sends data such as T _i , R _t , T _t , and T _b to the measurement recording circuit 130 via an optical communication line. Its communication control (e.g. polling/selecting method)
is performed by the local CPU 105 and the main CPU 133.

[Measurement Recording Circuit 130] In the measurement recording circuit 130, the temperature T _i of the injection liquid and the thermistor 1 are determined by this simple communication control procedure.
resistance R _t , temperature of thermistor 1 T _t , blood temperature T _b
etc., and store them in the RAM 132 in chronological order. Based on the above data, the CPU 133 calculates the initial cardiac output value CO, blood flow velocity v (v _i ), continuous cardiac output value
Calculate CO _i .

The RTC (real-time clock circuit) 147 counts the real time and also, for example, the LED display unit 6.
It is used for time monitoring such as the change of T _i → T _b in 9 after 30 seconds.

[Calculation of initial cardiac output value CO] FIG. 10A shows the structure of data stored in RAM 132. The capacity of this RAM is an area 132a that stores 30 minutes worth of data such as T _b obtained by A/D conversion every 4 ms, and a measurement value such as continuous cardiac output CO _i at any time from these data. There is only a region 132b for storing 30 minutes' worth of data, and a region 132c for storing 12 hours' worth of 3-minute average values of data such as CO _i obtained by continuous calculation.

FIG. 10B shows three address counters 160, 16 for storing data in RAM 132.
1,162 and the three areas 132a, 132
b, shows the correspondence with 132c. A data storage address counter (SC pointer) 160 points to an address at which data from the measurement circuit 120 is stored in the RAM 132. The data read address counter (RC pointer) 161 is used for calculating the initial cardiac output value CO, etc.
It reads the data stored in the RAM 132 and points to the address for storing the calculated value. A data print address counter (PC pointer) 162 points to data to be accessed when outputting data on the plotter 50. The reason why three pointers are used in this way is that data storage, data reading, data output, etc. are performed independently and in parallel as subroutines.

In Figure 11, the main CPU 133 is the local CPU.
Receives measurement data from 105 and stores it in RAM 132.
This is a routine that stores in . As described above, the SC pointer 160 is used as a pointer at this time.

13A and 13B show a control routine of the CPU 133 for measuring the initial cardiac output value CO value.

First, in step S40, the READY state of the measuring device is confirmed. This state assumes that no hardware failure has occurred in at least the entire device, and is a state in which a stable blood temperature T _b is detected. Note that when this state is detected, the START indicator 72 lights up as described above.
In step S41, it is determined whether the START switch 72 has been pressed. If it had been pushed,
The time t is real-time clock RTC147
, and the RC pointer 161 is set based on that time t in step S51. Step S52
Now, the injection liquid temperature T _i is known from the RAM 132. In step S53, according to the RC pointer 161,
Read one T _b from RAM132. Step S54
Now, the baseline temperature T _bp is detected from data before time t. At step S55, △
Calculate T _b (Figure 17). In step S56, ΔT _b (integral) is calculated.

Steps S57 and S58 show control for dealing with the case where ΔT _b is calculated due to noise in T _b . If it is noise, △ of this noise
Since T _b increases compared to the previous △T _b , it will decrease someday, so detect the maximum value when it increases,
If the maximum value is smaller than the threshold a, it is determined to be noise and the integral [ΔT _b is cleared in step S59. If △T _b has further increased in step S57, it cannot be determined that it is noise, so step S61
Proceed to. If it is determined to be noise, step S60
The pointer RC is incremented by a predetermined amount b. This b is the approximate time width of the noise component, which is known from experience. In step S61, it is determined whether the thermodilution curve has converged to _Tbp . That is, the above steps are repeated and the integration continues until convergence.

Next, a case will be explained in which the START switch 72 is not pressed in step S41. This control starts integration when it is determined that the change in T _b is a predetermined change. In addition, step S41
Since the depression of the START switch 72 is detected by an interrupt, if the above-mentioned interrupt occurs between steps S42 and S47, control is forcibly shifted to step S50. Now, in step S42, T _b is read from the RAM 132 according to the RC pointer 161. Step S42→Step S43→Step S44→
In the loop of step S42, since the change in T _b is captured from the moving average (16 samples) in this embodiment, the required number of samples is stored in the memory 132.
It's there to get from. The moving amount of the moving average is one sample data. Once the required number of samples is collected, the total number of samples for averaging will be collected every time one piece of sample data is read from the memory 132. In step S45, this moving average value T _b (n) is determined. In step S46, the difference from the previous moving average value T _b (n-1) is determined. If this difference is greater than or equal to a predetermined threshold, it is determined that the blood temperature has changed due to injection of the indicator liquid, and in step S49, time t at the time of this change is calculated. The subsequent control is the same as the case using the START switch 72 described above. If it is determined in step S47 that the change is less than the threshold value, in step S48 the current average value T _b (n) is changed to the previous average value T _b (n-1).
Move to storage area.

Returning to the explanation of step S63. Now, as mentioned above, according to the Stewart-Hamilton equation, CO=S _i・C _i・(T _b −T _i )・V _i /S _b・C _b・∫ ^∞ / _p △T _b d
t where, CO: cardiac output, S _i : specific gravity of injected liquid C _i : specific heat of injected liquid, V _i : amount of injected liquid T _i : temperature of injected liquid, T _b : temperature of blood S _b : blood Specific gravity, C _b : Specific heat of blood. The above formula becomes CO=A・(T _b −T _i )/∫ ^∞ / _p ΔT _b dt. Here, A=S _i ·C _i ·V _i /S _b ·C _b . In this correction constant A, S _i , S _b , C _b , C _i etc. are fixed, but V _i is affected by the fact that even if the indicator liquid is injected, it remains inside the catheter and does not flow out into the blood. receive. That is, the above V _i is merely a value for each purpose. Conventionally, as mentioned above, A was determined using a table determined experimentally in advance, but in this embodiment, this correction constant A is used to improve the reliability of operations by the operator.
is converted into a table (FIG. 12) and stored in the ROM 131. When subtracting one correction constant A from this table, as shown in FIG.
Fr, nominal liquid injection volume ml is used as address data. The correction constant data stored in the above table is previously determined from actual measurement results obtained when various amounts of injected liquid are changed for catheters of various sizes. If the catheter size and injection volume used in the actual measurement of CO by thermodilution method are
If it does not correspond to the above table, the corresponding correction constant A is determined by linear interpolation.

Return to the explanation of the flowchart. When the calculation of the integral of [△T _b is completed in steps S61 and above, as described above in step S63, the ROM 131 is The correction constant A is read from the table (FIG. 12) stored in the table. In step S64, the initial cardiac output value CO is calculated based on the above-mentioned Stewart-Hamilton equation. In step S65, these values are output on the plotter 50 as shown in FIGS. 4 and 5, for example.

[Continuous CO _i measurement] First, we will explain the principle by which CO _i can be calculated continuously. If the resistance value of thermistor 1 is _Rt , and the current value given to thermistor 1 by the constant current circuit 111 is _Ic , the amount of heat generated per unit time when thermistor 1 is heated is: _Ic2・_Rt become. If the heated thermistor 1 is placed in blood with a blood flow velocity v, the heated thermistor 1 will be cooled depending on the blood flow velocity v. The amount of heat cooled by the blood flow is K·v·(T _t −T _b ), where T _b is the temperature of the blood, T _t is the temperature of the heated thermistor, and K is the proportionality constant. Now, the temperature of the thermistor 1 is maintained at such a temperature that the amount of heat generated by heating and the amount of heat cooled are equal. This temperature is the thermal equilibrium temperature.

The above can be expressed as the following equation (2).

I _c2 ·R _t =K·v·(T _t −T _b )...(2) From equation (2), equation (3) for determining the blood flow velocity v is derived.

v=(1/K)( _Ic2・_Rt )/( _Tt − _Tb )...(3) That is, the data _Rt obtained from thermistor 1,
T _t and the blood temperature obtained from thermistor 2
The blood flow velocity v can be determined from T _b . Note that since the heating thermistor 1 is driven by the constant current circuit 111, the potential difference V _p between both ends of the lead wire of the heating thermistor 1 may be detected instead of detecting the resistance value. Details of this case are described in the above-mentioned Japanese Patent Laid-Open No. 125329/1983. Furthermore, although the constant current value I _c can be handled by detecting the current of the constant current circuit 111, it is also possible to provide it in the ROM 131 as a class term like the proportionality constant K.

Now, when the blood vessel cross-sectional area of the pulmonary artery is S, there is a relationship between the initial cardiac output CO and the initial blood flow velocity v as shown in equation (4).

CO=S・v...(4) Therefore, the initial cardiac output value CO and the initial blood flow velocity value v
From this, calculate the blood vessel cross-sectional area S according to equation (4), and use this value S as a calibration value (parameter) in the measurement recording circuit 1.
Hold within 30. In this way, once the parameter S is determined, the CPU 133 calculates the parameter S for the continuously measured blood flow velocity v _i.
By multiplying by , it is possible to obtain a continuous cardiac output value CO _i . That is, CO _i =S· _vi = (S/K)·(I _c2 ·R _t )/(T _t −T _b ) (5).

Figure 14 shows how this CO _i is calculated and the RAM 132
This is a control procedure of the CPU 133 stored in the CPU 133. Before starting this control, the initial cardiac output CO has already been measured. Step S81 ~ Step S85
is a control to obtain the above-mentioned parameter S.

In step S80, it is checked whether the measuring device 100 is in continuous mode. CONTINUOUS to this mode
The transition is made by pressing the switch 64. If it is continuous mode, in step S81, local CPU1
05 to heat the thermistor 1 via an optical communication path. In step S82, thermistor 1
Wait for the heating and cooling to reach thermal equilibrium. Eventually, T _t , R _t , t _{b ,} etc. are sent from the local CPU, and according to the flowchart in Figure 11,
Stored in RAM 132 in chronological order. Therefore, data in the RAM 132 is accessed using the RC pointer 161 according to time t when a certain period of time has elapsed. In step S84, the initial blood flow velocity v is calculated based on equation (3), and in step S85, the parameter S is calculated from the relationship between the initial cardiac output value CO and blood flow velocity v according to equation (4). . Thus, continuous CO _i
The preparations for measurement are now complete. The following control is the first CO _i
Since the calculation of CO _i at an arbitrary time is common, the calculation control of CO _i for V _i at an arbitrary time will be explained.

In step S86, it is confirmed whether continuous mode has been canceled. This is because the parameter S representing the blood vessel cross-sectional area usually changes over time. Therefore, even if the blood vessel cross-sectional area S is once held as a parameter, an accurate cardiac output may not be obtained due to a change in the blood vessel cross-sectional area S. Therefore, we measured the initial cardiac output CO using the thermodilution method as appropriate.
This is in preparation for the next continuous measurement of CO _i .

Step S87 unless continuous mode is canceled.
Proceed to and calculate CO _i =v _i ·S. In step S88, the average values of v _i and CO _i for 3 minutes are calculated in order to reproduce the lapse of 12 hours (FIG. 8). These values are
It is stored in the area 132c within the RAM 132. Then, in step S90, the RC pointer is incremented by 1 in order to calculate the next CO _i .

In this way, each time T _t , R _t , T _b , etc. are sent,
CO _i etc. can be calculated continuously. In this way, the cardiac output CO _i could be measured by measuring only the blood flow velocity v _i .

[Data Recording] In addition to recording thermodilution curves and thermodilution values as shown in _Figs . Continuous recording function to output (by switch 56), past 30
A recording/reproducing function (by switch 55) that outputs the measured values for each minute to the plotter 50, a progress chart output function (by the switch 54) that outputs the measured values for the past 12 hours (average value every 3 minutes) to the plotter 50, etc. It has an output function.

Output formats for continuous recording and recording playback are specified in Section 6.
Figure (Paper feed speed 10ms/min), Figure 7 (20ms/min)
As shown in (time).

Figure 8 shows the output format of the progress chart. In this progress chart, CO (=CO _i ) and blood temperature BT (=
Record the value of T _b ) along with the graph.

Now, since such recording is performed in continuous mode (when the CONTINUOUS indicator 64 is lit), in parallel with output to the plotter 50, the local CPU 105
It is necessary to import data from the computer and perform calculations/recording of CO _i , etc. For this control,
To access the RAM 132, as shown in FIG. 10B, the PC pointer 162 is sent to the plotter output.
For data acquisition, SC pointer 160 is used for calculation/
An RC pointer 160 is used for storage.

[Substitute for injection liquid temperature] Since the indicator liquid to be injected is placed in an ice-cooled container, its temperature can be said to be determined mostly by the ice-cooling temperature. Therefore, when this ice-cooling temperature is known (for example, zero degrees), it can be regarded as the indicated liquid temperature.

For this purpose, in this measuring device, the temperature probe 12
is not connected, it detects this and changes the temperature set by switch 75 to the liquid temperature.
It is regarded as T _i and used to calculate the initial cardiac output CO. Therefore, since the thermistor 12a of the temperature probe 12 is connected to the constant voltage circuit 101, the injection liquid temperature detection circuit 102 detects the current flowing through the thermistor 12a as zero. When the local CPU 105 receives E _i corresponding to this zero current, this local
The CPU sends a signal to that effect to the main CPU 133. Alternatively, the CPU 105 converts E _i corresponding to this zero current into a temperature T _i into an impossible value and sends it to the main CPU 133 . These allow the CPU 133 to detect that the temperature probe 12 is not connected.

FIG. 15 shows this control procedure. In Figure 13,
Instead of step S52 in which the main CPU 133 reads T _i from the RAM 132, in step S100 of FIG. 15, it is determined whether the T _i sent from the local CPU 105 is data indicating that the probe 12 is not connected. to judge. If the data indicates the connection status, in step S101, this RAM 132
T _i within is used for measurement. If not connected, in step S102 the data set in switch 75 is transferred.
Import as T _i .

[Measurement of relative change in cardiac output] The embodiment of the measuring device described above actually determines the initial cardiac output value CO using the thermodilution method, and measures this CO
The parameter S is determined from the relationship between the initial blood flow velocity v, and the cardiac output CO _i can be continuously determined by simply measuring the blood flow velocity v _i at an arbitrary time. That is, CO _i ∝v _i , and changes in v _i reflect relative changes in CO _i .
Therefore, if you record the change in v _i , it will remain as it is.
This means that we have recorded the relative change in CO _i . on the other hand,
The approximate value of the parameter S is known if the subjects are the same and the measurer is familiar with the measurement. Therefore, in the measuring device of this embodiment, this approximate parameter S is input as the "initial CAL value" from the switch 62, so that it is possible to omit the measurement of the initial cardiac output value CO by thermodilution. I have to.

[Application to other dilution methods] As is clear from the above explanation, the continuous cardiac output measurement in the above embodiment is performed once the initial cardiac output CO is measured by some method. If so, then the parameter S is measured and held, and thereafter the cardiac output CO _i can be continuously determined by simply measuring the blood flow velocity v _i . Therefore, the present invention is not limited to obtaining the initial cardiac output CO by measurement using the thermodilution method as in the above embodiment;
For example, the initial cardiac output CO may be obtained by a dye dilution method, an electrolyte dilution method, or the like.
In this case, in the dye dilution method, the amount of dye in the blood can be determined by measuring changes in illuminance, such as at the earlobe.
In the electrolyte dilution method, cardiac output CO is obtained by measuring changes in blood resistance using two electrodes installed on a catheter.

That is, the function of inputting the amount of data (for example, Fr, ml) that is the basis of the correction constant A can also be applied to general indicator dilution methods using a catheter. Also,
The automatic measurement start function can be directly applied to detecting the change points of the above-mentioned changes in illuminance and changes in resistance value. In addition, the continuous cardiac output measurement function is based on the initial cardiac output obtained by the general indicator dilution method.
It is also possible to obtain the parameter S based on CO and then calculate CO _i from the blood flow velocity v _i at any time.

Furthermore, as other variations and modifications, the temperature probe 12
We propose the following mechanism for detecting connections.
That is, a biased protrusion is provided at a portion of the main body of the measuring device to which the connector 16 of the probe is connected. When the connector 16 is connected, this protrusion is pushed and retracted. When the protrusion is pressed, the end of the protrusion connects to the measuring circuit 1.
For example, a ground signal is applied to 20. The measurement circuit 120 determines whether or not this ground signal is present.
It is possible to determine whether the probe 12 is connected or not. Note that the protrusion is electrically insulated from the circuit 120 except for its ends. This is to keep the entire circuit 120 electrically floating.

As another modification, blood flow rate measurement using thermistor 1 not only detects thermal equilibrium under constant current, that is, changes in thermistor resistance using voltage, etc., but also detects the temperature difference necessary to keep the temperature difference from blood temperature constant. A current may be applied and the current may be measured. In other words, the temperature of the thermistor is controlled at the upper limit of 42°C, which does not affect living organisms, and the current is measured. Further, the blood flow rate sensor is not limited to a thermistor, and other means may be used.

The cardiac output measuring device described above with reference to FIGS. 1A to 15 includes a catheter 12 and a thermistor as an indicator liquid data detection probe that is removably attached to the main body of the device and detects data related to the indicator liquid. 12a, thermistors 1 and 2 as blood data detection means for detecting and outputting blood data;
Temperature detection circuits 113, 115, etc., and a CPU 133 as an integrating means for integrating the difference value of blood data.
and a switch 75 as an input means for inputting a pseudo value of data related to the indicator liquid, and a switch 75 that automatically selects either the indicator liquid data detected by the indicator liquid data detection probe or the pseudo data input from the input means. as a means of selecting
CPU 133, connector 74, and CPU 13 as a cardiac output calculation means for calculating cardiac output
3.

The CPU 133 executes integration in steps S53 to S64, particularly in step S56. The CPU 133 steps from step S53 to step S64.
In particular, in step S64, cardiac output is calculated. In step S100 of FIG. 15, the CPU 133 detects whether the operator has pulled out the Ti probe or not, and determines whether to use manually input pseudo data or automatically measured indicator liquid data for the indicator temperature data. to judge. That is, the control procedure shown in FIG. 15 for determining whether or not the probe 12 is connected to the CPU 133 without the operator's intervention constitutes a selection means.

[Effects of the Invention] As explained above, according to the cardiac output measuring device of the present invention, when there is no need to accurately measure data related to an indicator liquid, such as temperature data,
By inputting a data value close to the actual data of the indicator liquid from a switch or the like instead, cardiac output based on the thermodilution method can be measured, improving operability. Furthermore, since the device automatically determines which data to use, measurement efficiency is improved.

[Brief explanation of the drawing]

1A, 1B, and 1C are a plan view, a front view, a back view, and a second view of the measuring device according to the embodiment, respectively.
Figure A, Figure 2B, and Figure 2C are respectively an overall perspective view, a sectional view of a main part, and a sectional view of an opening of a catheter used in the measuring device of the embodiment, and Figure 3 explains the operating procedure of the measuring device of the embodiment. Figures 4 and 5 are diagrams showing examples of result output when cardiac output is measured based on the thermodilution method using the embodiment device, and Figures 6 to 8 are continuous diagrams. A diagram showing an example of outputting measurement results. Figure 9 is a circuit diagram of the main parts of the measuring device. Figures 10A and 10B are diagrams of the main parts of the measuring device.
Diagrams explaining the state of RAM management, Figure 11, Figure 1
3A, 13B, 14, and 15 are flowcharts showing the control procedure according to the embodiment, FIG. 12 is a table that stores the correction constant A, and FIGS. 16 and 17. FIG. 2 is a diagram illustrating the principle of cardiac output measurement using the conventional thermodilution method. In the figure, 1, 2, 12a... thermistor, 4...
Catheter, 6, 8, 10, 13, 14... tube, 7, 9, 11, 15, 16... connector,
12...Injection liquid temperature probe, 50...Protuter, 52, 53, 54, 55, 56, 57, 58
...Switch, 59, 60, 61, 62, 75...
...Setting input switch, 64, 65, 66, 67,
70, 72...Switch/indicator, 68
...4-digit LED display, 69...3-digit LED display,
71... LED bar graph, 73... Catheter connection connector, 74... Temperature probe connection connector, 100... Measuring device, 101, 112... Constant voltage circuit, 111... Constant current circuit, 102... Infusate temperature Detection circuit, 103...Analog switch, 104...A/D converter, 105, 133...
...CPU, 106,131...ROM, 107,1
32...RAM.

Claims (1)

[Claims] 1. An indicator liquid data detection probe that is detachable from the main body of the measuring device and detects data related to the indicator liquid before being injected into the blood vessel; blood data detection means for detecting and outputting the blood data obtained at each time; an integrating means for integrating the difference value between the blood data at each time and predetermined reference blood data; an input means for inputting related data as a pseudo value; and determining whether or not the probe is connected to the main body of the measuring device, and if not connected, inputting the pseudo value from the input means. a selection means for selecting data and, if connected, selecting the instruction liquid data outputted by the instruction liquid data detection means; and a cardiac output based on the selected one of the data and the integral value. A cardiac output measuring device comprising a cardiac output calculation means for calculating the cardiac output. 2. The cardiac output measuring device according to claim 1, wherein the indicator liquid data is the temperature of the indicator liquid.