JPH0467853B2 - - 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 vein. 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・∫ ^∞ / ₀ △T
_b dt……(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 ∫ ^∞ ₀ △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 injection amount of the indicator liquid and its temperature greatly affect the accuracy of the calculated value. Incidentally, normally, the liquid temperature Ti is accurately measured using a marmister or the like, and then the catheter 26 is primed and the indicator liquid is injected into the blood vessel. This indicator liquid is cooled or heated by body temperature until it is injected, causing an error in the measured value.
Therefore, in the past, the amount of fluid remaining in the catheter was estimated from the external shape of the catheter (French size), the amount of fluid injected, etc., and the amount was corrected by comparing it with the experimentally obtained cardiac output value. A constant was determined and this correction constant was applied to the calculation of cardiac output to reduce the influence of the residual fluid.

However, the correction constant obtained from the amount of fluid remaining in the catheter is just a list of numbers;
Because these numbers have no meaning to the measurer, calculation errors occurred when determining the above correction constants, and input errors occurred when inputting the determined correction constants into the measuring device. .

In a measuring device that measures biological information using an instrument, separate manual input of variable data used for the measurement is practiced in Japanese Patent Publication No. 34430/1983. However, especially when measuring cardiac output by thermodilution, the amount of fluid remaining in the catheter is, of course, related to the total calorific value of the injected fluid, but it also depends on the external shape of the catheter (French size). , is not determined by a simple (linear) calculation based on the amount of injected liquid, etc., but the Edward's equation that has been used conventionally is a result based on a nonlinear calculation.

Therefore, the present invention has been proposed in order to eliminate the drawbacks of the above-mentioned conventional examples. We propose a cardiac output measuring device that can prevent the aforementioned mistakes and efficiently calculate cardiac output with high accuracy by allowing the measuring person to input the parameters as realistic values. It's about doing.

[Means and effects for solving the problems] The structure of the present invention for achieving the above-mentioned problems includes an injection means for injecting an indicator liquid into a blood vessel, and a blood diluted by the indicator liquid injected into a blood vessel. blood data detection means for detecting and outputting data related to blood data; integrating means for integrating the difference value between the blood data at each time and predetermined reference blood data; and the amount of heat of the indicator liquid injected from the injection means. an input means for independently setting and inputting a plurality of parameters defining the injection means; and a memory for storing correction values for correcting the amount and temperature of the indicator liquid injected via the injection means, a memory that takes a plurality of parameters that define the injection means as address inputs, and obtains and stores the correction values corresponding to the plurality of parameters in advance; It is characterized by comprising a cardiac output calculation means for calculating cardiac output based on the correction value read from the memory using the parameter as an address.

An operator can input a parameter value for defining the amount of heat of the indicator liquid injected from an injection means such as a catheter through an input means. In addition, since the memory stores the correction value calculated in advance based on this parameter, even if the correction value can only be calculated by nonlinear calculation, which takes a long time to calculate, it can be calculated quickly. The correction value can be read from memory.

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

<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 recording paper is fed by 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 the desired data when inputting the desired data to the device 100, and the setting value is as follows.
These are, in order, the catheter diameter (unit: French), the injection volume of the indicated liquid (unit: ml), the body surface area (unit: m ² ), and the 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 to specify whether the temperature displayed is 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 CO has been completed using the thermodilution method;
Displays that it is now possible to register (ENTRY) the CO as data. This ENTRY
When the switch 70 is pressed while the indicator 70 is lit, the CO is registered as data. This registration is performed by measuring the initial cardiac output value CO several times using the thermodilution method in order to obtain the parameter S, and the measurer judges and registers the data that seems reliable. This is because the average value of the collected data is taken as CO.

The START switch/indicator 72 indicates that preparation for initial cardiac output CO measurement by thermodilution is complete, at which point pressing the switch initiates 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, and is 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 output mode 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. Sometimes, this bar graph displays the blood temperature baseline (reference temperature value) in addition to displaying temperature changes moment by moment.
T _b0 ) 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 left 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. .

FIG. 2B shows a sectional view of the main part of the catheter 4.
In the same 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 sectional view of the thermistor 1, thermistor 2, and the balloon 17, and FIG. 2C is a 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 ×
It is 0.15 ^t . 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 determined by the pressure detection port 18, tube 8,
This is confirmed based on the blood pressure value and pressure waveform detected from the arteriovenous pressure, right atrial pressure, and right ventricular pressure that have passed through the connector 9. 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 69 will display 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 START indicator 72 is turned on. 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 of press. 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 will be displayed digitally on the display 68, and if the switch 52 has been pressed, the plotter 50 will be 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.

If we have obtained sufficiently reliable CO data in the manner described above, then we can finally obtain continuous CO _{i data} .
Start measurement. This is done by simply pressing the CONTINUOUS switch 64 at the end. When this switch 64 is pressed, the CNTINUOUS 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.
( _i ) is output on the plotter 50. Figure 6 is 10
Figure 7 shows the output at a paper feed speed of 20 mm/hour. Furthermore, Figures 6 and 7
Although not shown in the figure, 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 Apparatus> The entire measuring apparatus 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 returns electrical signals (voltages) from the thermistors 1 and 2 in the catheter 4 and the thermistor 12a in the probe 12 to temperature data, and sends them 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. Do what you see. The local CPU controls the measurement circuit 120.
105, the main CPU 133 controls the measurement recording circuit 130.

<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
A thermistor temperature detection circuit 115 and a constant current circuit 111 are connected via lead wires 22 . Then, from the constant current circuit 111, the thermistor 1
A predetermined electric current I _c is supplied to the tube and the tube is heated. Also,
The temperature signal detected by the thermistor 1 is sent to the thermistor temperature detection circuit 115, and detected by this detection circuit 115 as a voltage _Et . The thermistor 12a in the injection liquid temperature probe 12 is driven by a constant voltage circuit 101, and the temperature change is detected by the circuit 102 as a voltage value E _i . In this way, the local CUP 105 converts the output voltages E _i , E _t , and E _b from the three thermistors 12a, 1, and 2 into the infusion liquid temperature T _i , the resistance R _t of thermistor 1, the temperature T _t of thermistor 1, and the blood Convert to temperature T _b .

This operation will be explained in more detail. ocal
The CPU 105 drives an analog switch 103 having a multiplexer function to perform time division processing.
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. The communication control (e.g. polling/seleting method) is
The local CPU 105 and main CPU 133 perform this.

<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
Compute 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 the 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.
6,162 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.

Figure 11 shows that the main CPU 133 is
Receives measurement data from CPU105, RAM1
This routine is stored in 32. As mentioned above, the pointer at this time is SC pointer 16.
Use 0.

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 measuring device is brought to the READY state. This state is a state in which a stable blood temperature T _b is detected on the premise that at least no hardware failure has occurred in the entire device. 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 has been pressed, the time t is set to real-time clock RTC1.
47 and sets the RC pointer 161 based on that time t in step S51. step
In S52, the injection liquid temperature T _i is learned from the RAM 132.
In step S53, one T _b is read from the RAM 132 according to the RC pointer 161. step
In S54, a baseline temperature T _b0 is detected from data before time t. Step S55,
Calculate ΔT _b (Figure 17). In step S56, 〓△T _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 ∆T _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, the step
At S60, 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 T _0b . That is,
Continue integrating by repeating the above steps 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 for getting 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 change in blood temperature is 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・∫ ^∞ / ₀
△T _b dt where, CO: Cardiac output, S _i : Specific gravity of injected liquid C _i : Specific heat of injected liquid, V _i : Volume 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. The above formula becomes CO=A・(T _b −T _i )/∫ ^∞ / ₀ △T _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 only a nominal value. 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. 12, the outer diameter Fr of the catheter 4 and the nominal liquid injection volume ml input from the switches 59 and 60 are used as address data. The correction constant data stored in the above table is previously determined from actual measurement results obtained by varying the amount of injected liquid 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, the switches 59 and 60 are turned on in step S63 as described above.
The correction constant A is read out from the table (FIG. 12) stored in the ROM 131 based on the catheter outer diameter Fr, indicated liquid volume ml, etc. inputted from the table (FIG. 12). In step S64, the above-mentioned Stewart
Calculate the initial cardiac output value CO based on Hamilton's 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 continuously calculated. 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・^R It becomes _t . 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.

Expressing the above using the following equation, the following equation (2) is obtained.

I _c ² ·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 T _b obtained from thermistor 2
From this, the blood flow velocity v can be determined. Incidentally, since the heating thermistor 1 is driven by the constant current circuit 111, the potential difference V ₀ between both ends of the lead wire of the heating thermistor 1 may be detected instead of detecting the resistance value. For details on this case, please refer to the above-mentioned Japanese Patent Application Publication No. 61
-Described in No. 125329. In addition, the constant current value
Although I _c can be applied even if the current of the constant current circuit 111 is detected, as a constant term like the proportionality constant K,
It is also possible to provide it in the ROM 131.

Now, when the cross-sectional area of the pulmonary artery is S, there is a relationship between the initial cardiac output value 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· _v = (S/K) (I _c ² ·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, the thermistor 1 waits for the thermal equilibrium between heating and cooling to be reached. 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. Then, when a certain period of time has elapsed, the RC pointer 1 is set according to time t.
61, data in the RAM 132 is accessed. In step S84, the initial blood flow velocity v is calculated based on equation (3), and in step S85, according to equation (4),
Parameter S is determined from the relationship between initial cardiac output value CO and blood flow velocity v. In this way, preparations for continuous CO _i measurements were completed. The following control is common in the calculation of CO _i at the initial CO _i and at an arbitrary time, so it will be explained as the control for calculating CO _i for v _i at an arbitrary time.

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 in 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 , R _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), recording and playback function to output measured values for the past 30 minutes to plotter 50 (by switch 55), measured values for the past 12 hours (average value every 3 minutes) to plotter 50 There are output functions such as a progress chart output function (by the switch 54).

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/memories such as CO _i . 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, use the SC pointer 160,
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 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 to T _i
Import as.

<Measurement of relative changes 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-mentioned 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 dye dilution, electrolyte dilution, or the like.
In this case, in the dye dilution method, the amount of dye in the bloodstream can be determined by measuring changes in illuminance at, for example, 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 function to detect 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 the thermistor 1 not only detects thermal equilibrium under constant current, that is, changes in thermistor resistance using voltage, but also detects the temperature difference necessary to keep the temperature difference from the blood temperature constant. A current may be applied and the current may be measured. In other words, the temperature of the thermistor is controlled to an upper limit of 42°C that does not affect living organisms, and the current is controlled. Further, the blood flow rate sensor is not limited to a thermistor, and other means may be used.

The device for measuring cardiac output described above with reference to FIGS. 1A to 15 includes a catheter as a means for injecting an indicator liquid into a blood vessel, and blood diluted by the injected indicator liquid. Thermistors 1 and 2 as blood data detection means for detecting and outputting data (e.g. blood temperature), temperature detection circuit 1
13, 115, etc., and as an integrating means for integrating the difference value between blood data and predetermined reference blood data.
A CPU 133 and switches 59 and 60 as input means for individually and independently setting and inputting a plurality of parameters defining the catheter as an injection means.
, a memory 131 (FIG. 12) that stores correction values for correcting the amount and temperature of the indicator liquid injected through a catheter as an injection means, and the integrated value and the correction value read from the memory. A CPU 133 is provided as a cardiac output calculation means for calculating cardiac output based on the following.

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.

The correction value table stored in the memory 131 in FIG. 12 is a correction value A that has been calculated and stored in advance using the inner diameter of the catheter and the injection amount of the indicated liquid input through the switches 59 and 60 as addresses. Output. The inner diameter of the catheter and the amount of indicator fluid injected affect the dead volume of the catheter. If the specific heat Ci and temperature Ti of the indicator liquid are abstracted, the amount of heat of the indicator liquid is defined by the dead volume of the catheter and the injection amount of the indicator liquid.
That is, the memory 131 is a memory that stores correction values for correcting the amount and temperature of the indicator liquid injected via the injection means.

[Effects of the Invention] As explained above, the cardiac output measuring device of the present invention includes an injection means for injecting an indicator liquid into a blood vessel;
blood data detection means for detecting and outputting data related to blood diluted by the indicator liquid injected into the blood vessel; and integration means for integrating the difference value between the blood data and predetermined reference blood data at each time. , an input means for individually and independently setting and inputting a plurality of parameters defining the injection means, and a memory for storing correction values for correcting the amount and temperature of the indicator liquid injected via the injection means. A plurality of parameters defining the injection means are used as address inputs, and a memory for determining and storing the correction values corresponding to the plurality of parameters in advance, and the integrated value and the input means are provided. The apparatus is characterized by comprising a cardiac output calculation means for calculating the cardiac output based on the input parameter as an address and the correction value read from the memory.

An operator can input parameter values for parameters defining an injection means such as a catheter through an input means. In other words, by making it possible for the measurer to input parameters that affect the amount of heat of the residual indicator liquid in the injection means such as a catheter, which causes measurement errors, as realistic values for the measurer, it is possible to It is possible to prevent errors in inputting correction constants. In addition, since the memory stores the correction value calculated in advance based on this parameter, even if the correction value can be calculated only by nonlinear calculation, which takes a long time to calculate, it can be calculated quickly. The correction value can be read out from memory.

[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 perspective views of the entire catheter used in the measuring device according to the embodiment, respectively;
Main part sectional view, opening sectional view, Figure 3 is a procedure diagram explaining the operating procedure of the measuring device of the embodiment, Figures 4 and 5 are
The figure shows an example of the result output when cardiac output is measured based on the thermodilution method using the embodiment device. Figures 6 to 8 are output examples when the results of continuous measurement are output. FIG. 9 is a circuit diagram of the main parts of the measuring device, FIG. 10A and FIG. 10B are diagrams explaining the RAM management within the measuring device, FIG. 11,
13A, 13B, 14 and 15 are flowcharts showing the control procedure according to the embodiment, FIG. 12 is a diagram showing a table storing the correction constant A, and FIGS. 16 and 17. The figure is a diagram explaining 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)

[Scope of Claims] 1. Injection means for injecting an indicator liquid into a blood vessel; Blood data detection means for detecting and outputting data related to blood diluted by the indicator liquid injected into a blood vessel; an integrating means for integrating the difference value between the blood data and predetermined reference blood data; and an input means for independently setting and inputting a plurality of parameters defining the amount of heat of the indicator liquid injected from the injection means. and a memory for storing correction values for correcting the amount and temperature of the indicator liquid injected via the injection means, wherein a plurality of parameters defining the injection means are used as address inputs, and the plurality of parameters a memory that previously obtains and stores the correction value corresponding to the parameter; and a heartbeat based on the integral value and the correction value read from the memory using the parameter input via the input means as an address. A cardiac output measuring device comprising a cardiac output calculating means for calculating the cardiac output. 2. The cardiac output measuring device according to claim 1, wherein the blood data detection means includes a temperature sensor, and the blood data is data related to blood temperature. 3. The injection means is a catheter, and the plurality of parameters are an injection amount of the indicator liquid injected into the catheter and/or an outer diameter of the catheter or a temperature of the indicator liquid. The device for measuring cardiac output according to scope 1. 4. The cardiac output measuring device according to claim 1, wherein the input means includes a numerical input key.