JPH0467855B2 - - 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 illumination 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, or cubital vein, passes through the superior or inferior vena cava, the right atrium, and the right ventricle. The tip 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 liquid remaining in the catheter was estimated from the outer diameter of the catheter (French size), the amount of liquid injected, etc.
A correction constant was determined by comparing it with the cardiac output value obtained experimentally, and this correction constant was applied to the calculation of the cardiac output to reduce the influence of the residual fluid mentioned above.

On the other hand, in the method of 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.
In No. 244586 (Japanese Unexamined Patent Publication No. 125329/1986), 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 usually this indicator liquid is kept at a predetermined temperature by ice or warm water. 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. The object of the present invention is to propose a cardiac output measuring device with good operability, which can select both data and calculate cardiac output using the selected data.

[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 as follows: a liquid data detection means; a blood data detection means for detecting and outputting blood data diluted by an indicator liquid injected into a blood vessel; and a blood data detection means for detecting and outputting blood data diluted by an indicator liquid injected into a blood vessel; an integrating means for integrating, an input means for setting arbitrary data and inputting it as a pseudo value of data related to the indicator liquid, and an indicator liquid data detected by the indicator liquid data detection and pseudo data input from the input means. a selection means for selecting either one of the above through an operation by an operator; and a cardiac output calculation means for calculating a cardiac output based on one of the data selected by the selection means and the integral value. It is characterized by being prepared.

When accurate cardiac output is required, the operator uses the indicated fluid data detected by the indicated fluid data detection means, and when absolute precision is not required, the operator uses pseudo data input by the input means to determine the cardiac output. Calculate quantities.

[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. , and then a parameter S that connects this blood flow velocity v to the heart rate CO
seek. 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 blotter. This blotter 50 outputs measurement results and the like. 52,
53, a switch for specifying the output mode on the blotter 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). The switches 57 and 58 are set at the paper feed speed of the blotter 50 (20
mm/hour and 10mm/minute).

54 is a blotter of 12 hours of CO ₁ , etc.
The switch 55 instructs the output (Fig. 8) above to output the past 30 data such as CO ₁ stored in the memory.
Output on the blotter 50 for minutes (Figs. 6 and 7)
This is a switch that instructs you to do the following: 80 is a memory switch, and when you press this switch,
The recording paper is fed about 6 cm. 56 is CO _i ,
Output changes in T _b , v _i, etc. on recording paper in real time (6th
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 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 end 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, which is a terminal for outputting analog signals such as blood flow velocity v ₁ 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: (): Measured CO _i , etc. are output on the recording paper of the blotter 50 in approximately real time (Figs. 6 and 7).
figure). This is done by pressing the "Continuous Record" switch 56.

(): CO _i for the past 30 minutes stored in memory
etc. are 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 blotter 50 (FIG. 8). This is convenient when measuring data on a patient who requires rest and noiselessness, since the printer does not make any blotter printing noises.

: 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 the blood temperature T _b can be visually confirmed when determining 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 recorded 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 ₁ etc. as a digital signal through an RS232 interface.

<Structure of the catheter> A second catheter has a built-in thermistor for measuring blood temperature T _b for the thermodilution method, a thermistor for measuring blood flow velocity v, etc.
Shown in Figure A. In the same figure, catheter 4 is 4
lumen. This catheter 4 has a pressure detection port 18 provided at its tip.
A balloon 17 made of a flexible elastic body is attached several millimeters behind the tip so as to cover the entire tip of the catheter tube, and air, preferably carbon dioxide gas, is injected or injected to inflate and compress the balloon 17. Balloon side hole 2 provided on the side of the balloon inner tube for removal
5, a thermistor 1 located 10 to 20 mm from the tip, a thermistor 2 located 10 to 15 mm further toward the base, and a thermistor 2 located 8.5 to 38 cm apart from the thermistors 1 and 2, and ,
It has a discharge port 3 provided at a position 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.

Note that the catheter 4 shown in FIG. 2A is used in the pulmonary artery via the jugular vein, femoral vein, or cubital vein, through the femoral vein or inferior vena cava, and then through the right atrium and right ventricle.
Considering that the flow direction of blood is from the proximal end of the catheter to the distal end, the thermistor 2 is placed closer to the distal end (i.e., downstream of the blood flow) when viewed from the discharge port 3.
It is set in. 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 figure, the pressure detection port 18, the balloon side hole 25, 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, and a balloon lumen 2 that is an air passage that inflates and deflates the balloon 17.
0, a thermistor lumen 21 that accommodates thermistors 1 and 2 and their lead wires, and an injection lumen 23 that passes an indicator liquid for dilution. or,
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. . 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. Figure 2B shows thermistor 1, thermistor 2 and balloon 1.
7, and FIG. 2C is a sectional view taken along the line -' of the catheter tube 4. FIG.
As shown in FIG. 2C, the four-lumen structure of this catheter described above includes a balloon lumen 20,
Pulmonary artery pressure lumen 19 and injection lumen 23
(FIG. 2C) is the thermistor lumen 21. The balloon lumen 20 has a balloon side hole 25 and communicates with the balloon tube 6. The pulmonary artery pressure lumen 19 has a pressure detection port 1
8 and communicates with the pulmonary artery pressure measuring tube 8 . The injection lumen 23 is located from the tip of the catheter.
It has a discharge port 3 at a position of 12 to 40 cm and communicates with an indicator liquid injection tube 10 on the base side. or,
The thermistor lumen 21 is 1 to 2 points from the tip.
cm away, and further proximally from there by 1 cm.
At positions ~1.5 cm apart, the side holes 26 and 26 have thermistors 1 and 2 installed, respectively.
27, and also incorporates thermistor lead wires 22 and 24 from thermistors 1 and 2, and furthermore, on the base side, the thermistor tube 13
communicate with.

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 catheter 4,
This is because it is necessary to accurately measure the temperature of the blood flow diluted by the thermistor 2, and to make the thermistor 2 less susceptible to the influence of the thermistor 1, which is a self-heating type.

The characteristics of the thermistor 1 used in the catheter of the example are B _25-45 = 3500K, R (37) = 1000Ω, and 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 ^l ×
0.16 ^w × 0.15 ^t . Thermistor 1 is 0.01~50
It is preferable to generate a calorific value of about 100 ml, as a higher calorific value may raise the blood temperature or damage the blood vessel wall if it comes into contact with the blood vessel, and a lower calorific value will result in lower detection sensitivity. Both are unfavorable for the following reasons.

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

First, in step S1, set the injectate temperature probe 1.
2 to the measuring device main body 100. step
In S2, the temperature probe 12 is placed in an ice-cooled container (in this embodiment, provided within the measuring device 100) near the injection instruction liquid. This liquid may be physiological saline or the like. After priming the catheter 4 in step S3, step S4
Insert it until it reaches the pulmonary artery. 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 position of the catheter 4 in the blood vessel is determined.
Confirmation is performed 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 pressure detection port 18, tube 8, and 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
This is set when measuring the relative CO _i (described later), and is not necessary when measuring the initial cardiac output value CO using the thermodilution method described now.

In step S7, the measuring device is powered on.
Abnormal display at step S8 (indicating device failure)
While making sure that there is no
Wait for SINGLE indicator 65 to light up. When indicator 65 lights up, BLOOD
The 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 injected liquid at this point,
When the INJECTATE switch 67 is pressed, the display on the display 69 changes to indicate the injection liquid temperature T _i . still,
This T _i display will automatically display after 30 seconds.
The display returns to the BLOOD display, and the display 69 displays T _b again. The reason why the display automatically returns to T _b in this way is also useful for the operator.
This is because T _b is more meaningful as information. 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, it means that preparations are ready to start measuring the initial cardiac output value CO using the thermodilution method. In step S11, the mode of information to be output to the blotter 50 is selected by the switch 52 or 53, if necessary. In step S12, Kotoku 1
Listen to 1 and inject the liquid into the blood vessel.

After liquid injection, this measuring device automatically reads the change in T _b and determines the point at which integration should begin. If the operator presses the START switch 72 before detecting this optimum point, T _b
Begin the integration of . If the switch 72 is not pressed, the T _b data from the time determined by the device itself is integrated. CO measurement calculation using this thermodilution method usually completes in a few dozen seconds, but changes during that time are stored in a predetermined memory (RAM 132 in Figure 9).
is displayed on the display 69 and bar graph display 71. Furthermore, if the switch 53 was pressed, the blood temperature would be as shown in Figure 4.
The change in T _b is output to the blotter 50 . These displays allow the operator to confirm that the device is operating normally. In Figure 4, blood temperature
T _b is taking a negative upward trend. Note that the date, time, etc. will also be output on this graph for the convenience of the measurer. The output example shown 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 is pressed, the blotter 50 outputs the measurement results as shown in FIG. In this Figure 5, in addition to the date and time, cardiac output CO, body surface area BSA input from switch 61, blood temperature BT (=T _b ), catheter inner diameter CAT (=Fr), and indicated liquid injection amount are shown. IV (=
V _i ), cardiac index CI (=CO/BSA), injectate temperature IT
(=T _i ), and indicates that it has been registered **
The display of ENTRY** etc. is also recorded. Completion of CO measurement can be confirmed by lighting the ENTRY indicator 70 (step S15).

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. This completes the measurement of the initial cardiac output CO using the thermodilution method.

If you want to get more accurate CO,
Repeat the operations from step S11 mentioned above,
Obtain multiple measurement data. For each measurement, the ENTRY switch 70 is pressed and registered, and the initial cardiac output value CO value is determined from the plurality of registered CO values.

Once you have obtained sufficiently reliable CO data as described above, it is time to obtain continuous CO data.
Start CO _i measurement. this is on the edge
This is done by simply pressing the CONTINUOUS switch 64. When you press this switch 64,
The CONTINUOUS indicator 64 lights up and the entire measuring device enters continuous measurement mode.
It should be noted that when the SINGLE switch 65 is pressed, the measuring device goes into intermittent mode again.

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 blotter 50.
Figure 6 shows paper feed speed of 10mm/min, Figure 7 shows paper feed speed of 20mm/min.
It is output at a paper feed speed of 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 is 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 the measuring device> The entire measuring device 100 with the catheter 4 and the injectate temperature probe 12 connected is the ninth
As shown in the figure. This measuring device consists of two electrically isolated measuring circuits 120.
and 130. The circuit 120 mainly converts electrical signals (voltages) from the thermistors 1 and 2 in the catheter 4 and the thermistor 12a in the probe 12 into temperature data, and sends them to the measurement recording circuit 130 via the optical communication circuit 108. send.
The 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 blotter 50. Executes display on various display devices. The local CPU 105 controls the measurement circuit 120, and the main CPU 133 controls the measurement recording circuit 130.
It is.

<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 into the pulmonary artery by right heart catheterization in a manner similar to that described above. sensor 1
Connector 15 of 50 is connector 7 of main body 100
Combine with 3. The thermistor 2 is connected via a lead wire 24 to a constant voltage circuit 1 that drives the thermistor 2.
12 and a temperature detection circuit 113 that measures the temperature of blood.
It is connected to the.

The pulmonary artery blood temperature signal detected by the thermistor 2 is detected by the blood temperature circuit 113 as a voltage signal E _b . On the other hand, thermistor 1
is connected to the thermistor temperature detection circuit 115 and the constant current circuit 111 via the 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 detected by this detection circuit 115 as a voltage _Et . The thermistor 12a in the injection temperature probe 12 is driven by a constant voltage circuit 101,
The temperature change is detected by the circuit 102 as a voltage value E _i . In this way, local CPU10
5 is the output voltage E _i , E _t , E _b from the three thermistors 12a, 1, 2, the temperature T _i of the injection liquid, the resistance R _t of thermistor 1, the temperature T _t of thermistor 1,
Convert to 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, inputs E _i , E _t , and E _b to the A/D converter 104 in a time-division manner, and sequentially inputs the above voltage values as digital values into the RAM 1.
Take it into 07. These voltage values are ROM10
6 is converted into temperature data from a voltage-temperature conversion table stored in 6. 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 is
These data such as T _i , R _t , T _t , and T _b are sent to the measurement recording circuit 130 via an optical communication line. The communication control (for example, boring/selecting method) is performed between the local CPU 105 and the main CPU.
133 is carried out.

<Measurement recording circuit 130> The measurement recording circuit 130 receives the temperature T _i of the injected liquid, the resistance R _t of thermistor 1, the temperature T _t of thermistor 1, the blood temperature T _b, etc. through this simple communication control procedure. and stored in the RAM 132 in chronological order. The CPU 133 calculates the initial cardiac output value CO, blood flow velocity v(v _i ), and continuous cardiac output CO _i based on the above data.

An RTC (real-time clock circuit) 147 counts real time and is further used to monitor time, such as changing T _i →T _b of the LED display unit 69 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 of data such as T _b obtained by A/D conversion every 4 ms, and an area (132a) that stores data such as continuous cardiac output CO _i at any time from these data. An area (132b) for storing measurement values for 30 minutes,
There is only an area (132c) that stores 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 for storing data in RAM 132;
161, 162 and the three areas (132a,
132b, 132c). data storage address counter (SC pointer) 160,
Points to the address at which data from the measurement circuit 120 is stored in the RAM 132. A data read address counter (RC pointer) 161 reads data stored in the RAMI 132 for calculating the initial cardiac output value CO, and points to an address for storing the calculated value. . A data print address counter (PC pointer) 162 points to data to be accessed when outputting data onto the blotter 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 local
Receives measurement data from CPU105 RAM1
This routine is stored in 32. As mentioned above, the pointer at this time is SC pointer 1.
60 is used.

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 set to READY.
Check the status. This state is based on the premise that at least no hardware failure has occurred in the entire device, and is a state in which a stable blood temperature T _b is detected. Furthermore, when this condition is detected,
As mentioned above, START indicator 72
lights up. In step S41, it is determined whether the START switch 72 has been pressed. If it has been pressed, the time t is read from the real time clock RTC 147, and the RC pointer 161 is set based on the time t in step S51. In step S52, the injection liquid temperature T _i is
I know from RAM132. In step S53, RC
One T _b is read from the RAM 132 according to the pointer 161 . In step S54, a baseline temperature _Tbp is detected from data before time t. At step S55, △T _b (Fig. 17)
Calculate. In step S56, Σ△T _b (integral)
Calculate.

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, △T _b of this noise increases compared to the previous △T _b but will decrease someday, so detect the maximum value when it increases, and when the maximum value is smaller than the threshold a. is determined to be noise, and the integral ΣΔT _b is cleared in step S59. If ΔT _b has further increased in step S57, it cannot be determined that it is noise, and the process proceeds to step S61. If it is determined to be noise, the pointer RC is incremented by a predetermined amount b in step S60. 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, until convergence,
Continue the integration by repeating the steps above.

Next, in step S41, the START switch 72 is turned on.
Explain the case where is not pressed. This control is T _b
Integration is started when it is determined that the change in is a predetermined change. In addition, step
Since the depression of the START switch 72 in S41 is detected by an interrupt, if the above-mentioned interrupt occurs between steps S42 and S47, control is forcibly shifted to step S50. Now, step
At S42, T _b is set to RAM according to RC pointer 161.
132. Step S42 → Step
The loop of S43 → step S44 → step S42 is
In this embodiment, since the change in T _b is captured from the moving average (16 samples), this is to obtain the required number of samples from the memory 132. 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 equal to or greater than a predetermined threshold value, it is determined that the change in blood temperature is due to the injection of the indicator liquid, and in step S49, the time t at the time of this change is calculated. The subsequent control is by the START switch 72 mentioned above.
It is the same as when If step S47
If it is determined that the change is less than the threshold value, the current average value T _b (n) is moved to the previous average value T _b (n-1) storage area in step S48.

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. 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 calculated using a table with the aim of improving the reliability of operations by the operator. (Figure 12)
and stored in the ROM 131. When subtracting one correction constant A from this table, the first
As shown in FIG. 2, the outer diameter F of the catheter 4 and the amount of liquid injected into each eye (ml) input from the switches 59 and 60 are used as address data. The correction constant data stored in the above table is as follows.
Determine this from actual measurement results when varying the volume of injected liquid for various sizes and catheters. If the catheter size and injection fluid volume used in the actual measurement of CO by the thermodilution method do not correspond to the above table, the corresponding correction constant A is determined by linear interpolation.

Return to the explanation of the flowchart. Step S61
After completing the calculation of the integral of Σ△T _b ,
As described above in step S63, switch 5
Catheter outer diameter set from 9,60
ROM131 based on Fr, indicated liquid amount ml, etc.
The correction constant A is read out from the table (FIG. 12) stored in the table (FIG. 12). 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 outputted onto the blotter 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 blood flow increases blood temperature.
When T _b is the temperature of the heated thermistor, T _t is the constant of proportionality, and K is the constant of proportionality, K·v·(T _t −T _b ). 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 _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,
From T _t and the blood temperature T _b obtained from the thermistor 2, the blood flow velocity v is determined. Incidentally, since the heating thermistor 1 is driven by the constant current circuit 111, instead of detecting the resistance value, the potential difference V _p between both ends of the lead wire of the heating thermistor 1 is detected.
may be detected. Details of this case are described in the above-mentioned Japanese Patent Laid-Open No. 125329/1983. Furthermore, the constant current value I _c is the constant current circuit 111
Although it can be handled by detecting a current of , the proportionality constant K
Similarly, it is also possible to provide it in the ROM 131 as a constant term.

Now, if the cross-sectional area of the pulmonary artery is S,
There is a relationship as shown by equation (4) between the initial cardiac output value CO and the initial blood flow velocity value v.

CO=S・v...(4) Therefore, from the initial cardiac output value CO and the initial blood flow velocity value v, calculate the blood vessel cross-sectional area S according to equation (4), and use this value S as the calibration value (parameter ) is held in the measurement recording circuit 130. In this way, once the parameter S is determined, the CPU 133
By multiplying the continuously measured blood flow velocity v _i by the parameter S, it is possible to obtain a continuous cardiac output value CO _i . That is, CO _i =S・v _i =(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. Steps S81 to 85 are controls for determining 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 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 , 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 (switch 55) that outputs the measured values per minute to the blotter 50, a progress chart output function (switch 54) that outputs the measured values of the past 12 hours (average value every 3 minutes) to the blotter 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/hour)
As shown.

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), 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.
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.

Therefore, in this measuring device, when the temperature probe 12 is not connected, it is detected and the temperature set by the switch 75 is changed to the liquid temperature T _i
It is 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 by switch 75 is
Import as T _i .

<Measurement of relative changes in cardiac output> In the embodiment of the measuring device described above, the initial cardiac output value CO is actually determined by the thermodilution method, and this
The feature is that the parameter S is determined from the relationship between CO and the initial blood flow velocity v, and from then on, the cardiac output CO _i can be determined continuously by simply measuring the blood flow velocity v _i at any 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 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 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 is directly applied to the above-mentioned change points of illuminance change and resistance value change. In addition, the continuous measurement function of cardiac output is based on the initial cardiac output CO obtained by the general indicator dilution method.
It is also possible to obtain the parameter S based on the parameter S, and then calculate CO _i from the blood flow velocity v _i at an arbitrary time.

Furthermore, as other variations and modifications, the temperature probe 12
We propose the following mechanism to detect connection. 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, an installation signal is given to 20. The setting 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 12a as an indicator liquid data detection means for detecting data related to an indicator liquid, and a thermistor 12a that detects blood data. Thermistors 1, 2, temperature detection circuits 113, 115, etc. serve as blood data detection means to output blood data, the CPU 133 serves as an integration means to integrate the difference value of blood data, and pseudo values of data related to the indicator liquid are input. Switch 7 as an input means to
5, a CPU 133 and a connector 74 as selection means for selecting either the instruction liquid data detected by the instruction liquid data detection means or the pseudo data input from the input means through an operation by an operator; A CPU 133 is provided as a cardiac output calculating means for calculating the cardiac output.

The CPU 133 executes integration in steps S53 to S64, particularly in step S56. The CPU 133 calculates the cardiac output in steps S53 to 64, particularly in step S64. In step S100 of FIG. 15, the CPU 133 determines whether to use manually input indicator temperature data or automatically measured indicator temperature data by detecting whether the operator has pulled out the Ti probe. . That is, the connector 74 that informs the CPU 133 whether or not the prog 12 is connected constitutes selection means for determining the data input destination by the operator.

[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.

[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. Figure 9 is a circuit diagram of the main parts of the measuring device, and Figures 10A and 10B are diagrams showing an example of the output of measurement results.
Diagrams explaining the state of RAM management, Figure 11, Figure 1
FIG. 3A, FIG. 13B, FIG. 14, and FIG. 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. 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)

[Scope of Claims] 1. Indicator liquid data detection means for detecting data related to an indicator liquid before being injected into a blood vessel; and detecting and outputting blood data diluted by the indicator liquid injected into a blood vessel. blood data detection means; integration means for integrating the difference value between the blood data at each time and predetermined reference blood data; and means for setting arbitrary data and inputting it as a pseudo value of data related to the indicator liquid. and a selection means for selecting either one of the indicator liquid data detected by the indicator liquid data detection means and the pseudo data input from the input means through an operation by an operator, and one of the data selected by the selection means. and cardiac output calculation means for calculating cardiac output based on the integral value. 2. The cardiac output measuring device according to claim 1, wherein the indicator liquid data is the temperature of the indicator liquid. 3. The cardiac output according to claim 1, wherein the selection means includes a switch means for specifying and operating only one of the indicated liquid data detection means and the input means. measuring device.