JPS63216539A - Apparatus for continuously measuring relative change of heart rate output quantity - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a device for continuously measuring relative changes in cardiac output used in performing cardiac function tests.

[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 Fig. 16, a catheter 4 is introduced from the jugular vein, femoral vein, contralateral vein, etc., passes through the superior vena cava or vena cava, the right atrium, and the right ventricle, and its tip reaches the pulmonary artery. It is placed so that it is located inside. The catheter 25 is arranged such that the discharge port 26 is located in the right atrium, and the sumister 1 is located in the pulmonary artery. 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 liquid is diffused and diluted in the right atrium and right ventricle. The temperature of this diluted liquid is determined by a thermistor 27 located in the pulmonary artery.
From the area of the temperature dilution curve (diagram of temperature change over time) (Figure 17), Stewart
Cardiac output is calculated using the following equation (1) using the Hamilton method.

S, -C,・(Tb-T+)・VICO=□...
(1) b-c b+ 5 C: △Tbdt where, C〇2biphasic stroke volume Sl: Specific gravity of the injected liquid C1: Specific heat of the injected liquid, vI: Injected liquid amount T1: Temperature of the injected liquid, Tb: Blood temperature Sb: specific gravity of blood, Cb: specific heat of blood (o△rbdt: 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 injected liquid and its temperature greatly affect the accuracy of the calculated value. Affect. Incidentally, normally, the liquid temperature TI is accurately measured with a thermistor or the like, and then the catheter 26 is brimmed to inject the indicator liquid into the blood vessel. This may cause the product to be cooled or heated, causing an error in the measured value. Therefore, in the past, the amount of liquid remaining inside the catheter was calculated based on the inner diameter of the catheter (French size).
Based on the amount of injected fluid, etc., a correction constant is determined based on Edwards' formula, and this correction constant is applied to the calculation of cardiac output.
The effect of the residual liquid mentioned above was reduced.

However, the correction constant obtained from Edwards' formula is just a list of numerical values and has no meaning to the measurer, so calculation errors may occur when determining the correction constant.
Furthermore, input errors occur when inputting the determined correction constants into the measuring device. This error is not limited to thermodilution methods, but is a problem that occurs in indicator dilution in general, since indicator dilution methods use catheters.

■: Now, as you can see from Figure 17, if the operation of injecting the indicator liquid and the start of the integral calculation are not performed at the specified timing, the integral calculation will be performed after the blood temperature has decreased, etc. This may cause calculation errors. However, in the past, the measurer relied on intuition to instruct the measuring device to start measurement, that is, to start integration, after injecting the liquid, so there was always the possibility of a measurement error occurring. This error factor is not limited to the thermodilution method, but is also a general problem of indicator dilution.

■: In measuring cardiac output based on the thermodilution method described above,
The temperature of the injected indicator liquid is measured, usually by immersing it in an ice or wetting solution that is maintained at a predetermined temperature.

Therefore, if a person is an experienced measurer or if absolutely accurate measurement of cardiac output is not required, the above solution temperature may be regarded as the indicated liquid temperature T.

d) 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, so it is not possible to measure the cardiac output continuously. It cannot be used to measure cardiac output. Further, if measurements are to be made 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 due to the liquid injection operation, which is not preferable.

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 Japanese Patent Application No. 24
In No. 4586 (Japanese Unexamined Patent Publication No. 125329/1983), we proposed a completely new cardiac output measurement device that enables continuous measurement of cardiac output. This continuously measurable cardiac output measuring device allows continuous recording.

■: Furthermore, the above-mentioned Japanese Patent Application No. 59-244586 discloses that from the measurement of cardiac output and blood flow velocity by a single thermodilution method,
The gist of this study is to find the relationship between cardiac output and blood flow velocity, and then calculate cardiac output from this relationship and blood flow velocity. That is,
There is a fixed relationship between cardiac output and blood flow velocity, so unless you are looking for an absolute cardiac output value, you can simply find the blood flow velocity value and calculate the relative change in cardiac output. It becomes possible to know.

Therefore, the object of the present invention is to
It is necessary to further develop the principle of the device that can continuously measure cardiac output shown in No. 86, and to make it easier for the operator to measure the relationship between cardiac output and blood flow velocity. The object of the present invention is to propose a device for continuously measuring relative changes in cardiac output that is capable of continuously measuring relative changes in cardiac output.

[Means and effects for solving the problems] The configuration of the present invention for achieving the above-mentioned problems includes: a blood flow velocity measuring means for measuring a blood velocity value; an input means for inputting an arbitrary numerical value; A cardiac output that continuously calculates relative changes in the cardiac output value as each time elapses based on the blood flow velocity value at each time measured by the blood flow velocity measurement means and the above-mentioned numerical value. Quantity calculating means.

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

<External Appearance of Example Device> FIGS. 1A to 1C are plan views of a continuous measurement and recording device for cardiac output to which the present invention is applied.

A front view and a back view are shown. FIG. 2A shows the appearance of the catheter connected to this measuring device, FIG. 2B shows a cross-sectional view of the distal end of the catheter along the longitudinal direction, and FIG. 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 the thermodilution method, electrolyte dilution method, dye dilution method, etc., and the blood flow velocity V when this cardiac output is measured. is measured, and then a parameter S is determined that connects this blood flow velocity (2) to the cardiac output CO. After determining this parameter, the cardiac output CO1 at any time can be determined from this blood flow velocity V1 and the parameter S by simply measuring the blood flow velocity vI at any time.

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 plotter. This plotter 50 outputs measurement results and the like. 52 and 53 are switches for specifying the output mode on the plotter 50 when measuring the initial cardiac output value CO by the thermodilution method. The switch 52 is
Specifies that co is to be output as a numerical value (Figure 5). The switch 53 specifies that changes in blood temperature Tb, etc. are output as a curve (FIG. 4). switch 57.5
8 is the paper feed speed of the plotter 50 (20 mm/hour and 10 m/hour)
m/min).

54 is a switch for instructing to output the 12 hours' worth of C05 etc. data on the plotter 50 (Fig. 8), and 55 is a switch for outputting the past 30 minutes' worth of CO5 etc. data stored in the memory on the plotter 50. This is a switch that instructs output to the output (FIGS. 6 and 7). 80 is a memo switch, and when this switch is pressed, recording paper is fed to 6CI11. 56 is a switch for instructing to output changes in CO+, Tb, Vt, etc. on recording paper in real time (FIGS. 6 and 7).

Switches 59, 60 (Fig. 1A), at, 62 (first
Figure B) etc. are switches for manually setting desired data when inputting the data into the device 100, and the setting values are sequentially determined by the catheter diameter (unit:
French), the injection volume of the indicated liquid (unit: ml), body surface area (unit: m2), and initial CAL value (unit: 57 minutes).

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.

65 is a single (intermittent) mode switch/indicator, which is mainly used to switch to 0 intermittent mode (SI NGLE mode), which is used when returning from continuous mode to single mode when you want to set parameter S again. Lights up when Display 68 is a four-digit LED that digitally displays cardiac output. Switches 66 and 67 change the temperature displayed on the three-digit LED display 69 to the blood temperature Tb.
or the temperature T of the indicator liquid.

The ENTRY switch/indicator 70 indicates that the initial cardiac output value CO has been measured by the thermodilution method, and the CO
Displays that it is now possible to register (ENTRY) as data. This ENTRY indicator 7
If this switch 70 is pressed while 0 is lit, that Co will be registered as data. This registration is performed using the initial cardiac output value C using the thermodilution method in order to obtain the parameter S.
This is because the measurer measures O several times and determines and registers the most reliable data among them, thereby making the average value of the registered data the CO.

The 5TART switch/indicator 72 indicates that preparation for measuring the initial cardiac output value CO by thermodilution is complete, and when this switch is pressed at that point, integration based on the Stuart-Hamilton equation is started.

The display 71 is a bar graph, and mainly displays the value of blood temperature Tb 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 connector 16 of the temperature probe 12 (FIG. 2A) for measuring the temperature of the injected fluid, respectively.
It is a connector for connecting.

Switch 75 in FIG. 1C is a rotary switch that manually sets the temperature of the injectate. 76 is a connector of an R3232C interface for communicating with other external measuring devices, and 7B is a connector for communicating blood temperature T5. to (or from) other external measuring devices. A terminal 77 for outputting analog signals such as blood flow velocity vI cardiac output Co, etc. is a connector to which a power cable is connected.

<Functions of the measuring device> The features of the embodiment device shown in FIGS. 1A to 1C and 2A to 2C are as follows: ■: To correct the influence of the indicator liquid remaining in the catheter. Instead of having to calculate the correction constants based on the conventional Edwards formula, the measurer creates a table of correction constants in advance and uses the table as data to access when injecting the indicated liquid. A switch 59 for setting and inputting the inner diameter size of the catheter (LL: French) used for
is provided in this measuring device.

■: After injecting the indicator liquid into the blood vessel, the change in blood temperature T is automatically recognized without the need for the operator's intervention.
Integration based on the above Stewart-Hamilton equation (1) is started.

■: Temperature probe 1 to measure the temperature of the indicator liquid.
2 is used, but when the connector 16 of this probe 12 is not connected to the measuring device 100, this disconnection is detected and the value set on the switch 75 (Fig. 1C) on the back of the device is used to indicate the liquid temperature. Manpower as a Tr.

■Second, measure CO by thermodilution method and set parameter S.
Once obtained, Cot, blood temperature Tb, blood flow velocity vl, etc. are continuously stored in the memory and output on recording paper as necessary. The output mode is (i): Not measured
Cot, etc. are output on the recording paper of the plotter 50 in substantially real time (FIGS. 6 and 7). This is done by pressing the "Continuous Record" switch 56.

(if): C for the past 30 minutes stored in memory
Data such as OI is reproduced and output (Fig. 6).

Figure 7). This is done by pressing switch 55.

(fit): Compress data such as CO1 for the past 12 hours and reproduce and output it on the plotter 50 (FIG. 8). this is,
This is convenient when measuring data on a patient who requires rest and noiselessness because the plotter does not make any print noise.

(2): The parameter S is manually set via the switch 62, and the COI can be continuously determined from this S and the blood flow velocity vI. This is useful when you want to know the relative change in C01.

(2): With the bar graph display 71, changes in blood temperature Tb can be visually confirmed when determining the initial cardiac output value CO using the thermodilution method. In particular, this bar graph can not only display the temperature change by changing it every moment, but also can display the blood temperature baseline (reference temperature value T, .) and the maximum temperature T bmax fixed.

■: This device has a built-in battery (148 in FIG. 9) to protect stored data from failures such as power outages. When the output voltage of this battery 148 drops, LE078 is blinked to call attention to it.

■For external measuring devices other than the two-piece measuring device 100,
Analog output circuits (142, 151) are provided for outputting the signals from the terminal 78 as analog signals.

[Phase] For an external measuring device other than the two measuring device 100, R
It is equipped with a circuit (144) that outputs COL etc. as a digital signal through a 3232 interface.

Structure of Catheter> FIG. 2A shows a catheter incorporating a thermistor for measuring blood temperature Tb for the thermodilution method, a thermistor for measuring blood flow velocity V, and the like. In the same figure,
Catheter 4 is configured to have 4 lumens.

This catheter 4 has a pressure detection port 18 provided at its tip.
, a balloon 17 made of a flexible elastic body attached a few mm back from the tip so as to cover the entire tip of the catheter tube, and a balloon for injecting or releasing air to expand and deflate the balloon 17. Balloon side hole 25 provided on the side of the inner tube and 10 to 2 holes from the tip
A thermistor 1 provided at a position of 0 mm, a thermistor 2 provided further 10 to 15 mm from there to the base side,
Furthermore, it has a discharge port 3 provided at a position spaced apart from the thermistor 1.2 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 part for measuring the blood flow velocity V (V+). Thermistor 2 measures the diluted blood temperature T necessary to measure the initial cardiac output CO by the thermodilution method.

used to measure The discharge port 3 is for discharging an indicator liquid.

The catheter 4 shown in Fig. 2A is connected to a vein, femoral vein, or contravening vein, and is used in the pulmonary artery via the femoral vein or vena cava, the right atrium, and the right ventricle; therefore, the direction of blood flow is Considering that it is from the catheter proximal end side to the distal end side, the thermistor 2 is connected to the discharge port 3.
It is provided on the distal side (that is, on the downstream side of blood flow) when viewed from above. 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, the thermistor 1.2, 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 expands and deflates the balloon 17,
These are a thermistor lumen 21 that accommodates the thermistor 1.degree. 2 and their lead wires, and an injection lumen 23 that passes an indicator liquid for dilution. Furthermore, these four lumens are independent, and a second lumen is provided at the rear end of the catheter.
As shown in the figure, it is connected to a pulmonary artery pressure measuring tube 8, a balloon tube 6, a thermistor tube 12, and an indicator fluid injection tube 10. Each tube 8,6.
10 is equipped with a connector 7.9.11 at its rear end.

The thermistor tube 12 is connected to a connector 15, through which lead wires 22, 24 connected to the thermistors 1 and 2, respectively, are passed.

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.
FIG. As shown in FIG. 2C, the four-lumen structure of this catheter described above includes a balloon lumen 20, a pulmonary artery pressure lumen 19, and an injection lumen 23 (second C).
) and 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 18 and communicates with the pulmonary artery pressure measurement tube 8 . The injection lumen 23 is located 12 to 4 mm from the tip of the catheter.
It has a discharge port 3 at a position of 0 cm and communicates with an indicator liquid injection tube 10 on the base side. Further, the thermistor lumen 21 has side holes 26 and 27 in which the thermistors 1 and 2 are attached, respectively, at a position 1 to 2 cm away from the tip and at a position 1 to 1.5 cm away from there toward the base side. It also incorporates thermistor lead wires 22, 24 from the thermistor 1.2, and communicates with the thermistor tube 13 on the base side.

In addition, if the thermistor 1 is a self-heating type thermistor,
It is more preferable to locate it on the downstream side of the thermistor 2 with respect to 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
zs-as = 3500, %R(37) = 1000Ω, and its magnitude is 1.18'xo.

4"xo, 15t 1. position is IIIm).The characteristics of thermistor 2 are B 211-411-3980 K%
Ω in R(37)-40, its magnitude is 0.50' Xo
.

16”XO, 15t.
.

It is preferable to generate a calorific value of 0.01 to 50 Joules,
A calorific value higher than this is undesirable because it increases the level of blood salts or may damage the blood vessel wall if it comes into contact with it, and a lower calorific value reduces detection sensitivity.

(Operating procedure for the measuring device) To better understand this measuring device, please refer to Figure 3A and 3.
The operating procedure from the operator's perspective will be explained using Figure B.

First, in step S1, the injectate temperature probe 12 is connected to the measuring device main body 100. In step S2, the temperature probe 12 is placed in a water-cooled container (in this embodiment, the measurement device 100 is
Immerse in the injection instruction liquid (provided inside). This liquid may be physiological saline or the like. After brimming the catheter 4 in step S3, it is inserted up to the pulmonary artery in step S4. The catheter 4 is inserted from 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, the tube 8. This is confirmed based on the blood pressure value and pressure waveform detected from the arterial pressure that has 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 COI (described later), and is not necessary when measuring the initial cardiac output value CO by the thermodilution method described now. do not have.

In step S7, the measuring device is powered on. Step S
While confirming that there is no abnormal display (indicating a device failure) in step S8, the process waits for the SI NGLE indicator 65 to light up in step S9. When the indicator 65 lights up, the BLOOD indicator 66 lights up and the display 6
9 displays the blood temperature Tb in the pulmonary artery. If you want to know the temperature of the injection liquid at this point, press INJECTATE.
When the switch 67 is pressed, the display on the display 69 becomes a display of the injectate temperature TI. The T+ display automatically returns to the BLOOD display after 30 seconds have elapsed, and the display 69 displays T again.

The reason for automatically returning to the Tb display in this way is
This is because Tb is more meaningful as information to the operator. On the other hand, the bar graph display 71 at this point should be displaying the base line of the blood temperature Tt.

Furthermore, in step S10, the 5TART indicator 72
Wait until it lights 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 Sll, the mode of information to be output to the plotter 50 is selected by the switch 52 or 53, if necessary. In step 312, the cock 11 is opened to inject the liquid into the blood vessel.

After liquid injection, the measuring device automatically reads the change in Tb and determines the optimal time to start integration. If the operator presses the 5TART switch 72 before detecting this optimal point,
Integration of Tb starts from the moment the button is pressed. switch 7
If 2 is not pressed, T from the point determined by the device itself
b Integrate the data. The CO measurement calculation using this thermodilution method usually completes in a few seconds, but changes during that time are stored in a predetermined memory (RAM 132 in FIG. 9) and displayed on the display 69 and bar graph display 71. be done. Furthermore,
If the switch 53 has been pressed, changes in blood temperature Tt as shown in FIG. 4 are output to the plotter 50. These displays allow the operator to confirm that the device is operating normally. In FIG. 4, the blood temperature Tb is becoming negative upward. Note that the date, time, and other information are also output on this graph for the convenience of the measurer.

The output example shown in FIG. 4 is an output speed of 300 mm7.

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 measurement result is outputted by the plotter 50 as shown in FIG. . In this FIG. 5, in addition to date and time, cardiac output CO, body surface area BSA input from switch 61, blood temperature BT (=Tb), catheter inner diameter CAT (=F r), and indicated liquid injection amount are shown. I
V (=V+), cardiac index CI (=CO/BSA), infusion temperature IT (-T+), and the display of **ENTRY**, which does not indicate that it has been registered, are also recorded.

Completion of CO measurement can be confirmed by lighting the ENTRY indicator 70 (step 515).

If the measurer determines that the obtained data such as CO is reliable, he/she will register the data using E.
NTRY switch 70 is pressed (step 517). After a while, the 5TART indicator 72 lights up again. This completes the measurement of the initial cardiac output CO using the thermodilution method.

If you want to obtain more accurate CO, repeat the operations from step Sll described above to obtain a plurality of 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 registered plural CO values. Note that the first 1.2 measurement data are unreliable, so it would be better not to register them.

Once sufficiently reliable CO data has been obtained in the manner described above, it is time to start continuous CO1 measurements. This is done by simply pressing the C0NTINUOUS switch 64 at the end. When this switch 64 is pressed, C0N
The TINUOUS indicator 64 lights up and the entire measuring device enters continuous measurement mode. Furthermore, S I N0LE
When switch 65 is pressed, the measuring device is placed in intermittent mode again.

When the device is in the continuous measurement mode and the continuous recording switch 56 is pressed, the blood temperature B
T (-Tb), Co (=CO+).

The blood flow velocity v(v,) is output on the plotter 50.

Figure 6 shows a paper feed speed of 10 mm/min, Figure 7 shows a paper feed speed of 20 m/min.
It is output at a paper feed speed of m/hour.

Although not shown in FIGS. 6 and 7, it goes without saying that various data such as the date shown in FIG. 5 are output together with the graph. In addition, in the example shown in Figure 7, the thermodilution method was used to measure the initial cardiac output and CO value again at around 4:30 pm, so changes in the graph appear around that time. .

<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. The circuit 120 mainly converts electrical signals (voltage) from the thermistors 1 and 2 in the catheter 4 and the thermistor 12a in the probe 12 into temperature data, and sends the data to the measurement recording circuit 130 via the optical communication circuit 108. send. The measurement recording circuit 130 determines the initial cardiac output value CO from the temperature data from the measurement circuit 120.
1 Blood flow velocity V, parameter S, continuous cardiac output COI, etc. are calculated and displayed on the plotter 50 or various displays. The local CPU 105 controls the measurement circuit 120, and 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. Thermistor 2 detects the blood temperature inside
is built-in. This catheter type sensor 15Q is introduced to the pulmonary artery by right heart catheterization in the same manner as described above. Connector 15 of sensor 150
is coupled to the connector 73 of the main body 100. Thermistor 2
A constant voltage circuit 112 that drives the thermistor 2 and a blood temperature detection circuit 1 that measures the temperature of blood are connected via lead wires 24.
13.

The pulmonary artery blood temperature signal detected by the thermistor 2 is detected by the blood temperature detection circuit 113 as a voltage signal Eb. On the other hand, the thermistor 1 is connected to the thermistor temperature detection circuit 115 and the constant current circuit 11 via the lead wire 22.
Connected to 1. Then, a predetermined current is applied to the thermistor 1 from the constant current circuit 111. is supplied and heated.

Further, the temperature signal detected by the thermistor 1 is sent to the thermistor temperature detection circuit 115, and this detection circuit 11
5, it is detected as 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.
This current is detected as a current change, and this current is further detected as a voltage value E1. In this way, local CPU10
5 is the output voltage E l, E t, E b from the three thermistors 12a, 1.2, the temperature T of the injected liquid, and the resistance Rt of the thermistor 1.

The temperature Tt of the thermistor 1 is converted into the blood temperature Tb.

This operation will be explained in more detail. Local CPU105
is an analog switch 10 with multiplexer function
3 and A/D El+Et, Eb by time division.
The converter 104 is manually input to input the above voltage values into the RAM 107 as digital values. These voltage values are ROM
It is converted into temperature data from a voltage-temperature conversion table stored in 106. In addition, the resistance value Rt of thermistor 1
is calculated by Rt=Et/Ic. Here, IC is the current flowing through the thermistor. The local CPU 105 uses these T
Data such as I, Rt, Tt, and Tb are sent to the measurement recording circuit 130 via an optical communication line. The communication control (for example, boring/selecting method) is
This is performed by the PU 105 and the main CPU 133.

Measurement Recording Circuit 130> The measurement recording circuit 130 uses this simple communication control procedure to determine the temperature T+ of the injection liquid, the resistance Rt of the thermistor 1,
The temperature of thermistor 1 is T. The blood temperature is T.

etc., and stores them in the RAM 132 in chronological order. C.P.
U133 is the initial cardiac output value C based on the above data.
O, blood flow velocity V (V+), and continuous cardiac output Co are calculated.

The RTC (real-time clock circuit) 147 counts real time, and also controls the T I- of the LED display unit 69, for example.
It is used for time monitoring such as changing T b 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
), and an area (1
32b) and an area (132c) for storing 3-minute average values of data such as col etc. obtained by continuous calculation for 12 hours.

FIG. 10B shows the correspondence between three address counters 160, 161, 162 for storing data in RAM 132 and the three areas (132a, 132b, 132c). A data storage address counter (SC pointer) 160 stores data from the measurement circuit 120 in RAM1.
Points to the address to be stored in 32.

A data read address counter (RC pointer) 161 is stored in the RAM for calculating the initial cardiac output value CO.
132 and points to the address at which the calculated value is to be stored. A data print address counter (PC pointer) 162 points to data to be accessed when outputting data on the plotter 5o. The reason why three pointers are used in this way is that data storage, data reading, data output, etc. are performed independently and in parallel as subroutines.

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

Figures 13A and 13B are cP for measuring the initial cardiac output value CO value.
This is the control routine of U133.

First, in step S40, the READY state of the measuring device is confirmed. This state assumes that no hardware failure has occurred in at least the entire device, and that the blood temperature T,
A stable state is defined as the detected state. Note that when this state is detected, the 5INOLE indicator 65 lights up as described above. In step S41, it is determined whether the 5TART switch 72 has been pressed. If it has been pressed, the time t is set to the real-time clock RTC.
147 and sets the RC pointer 161 based on that time t in step S51. In step S52, the injection liquid temperature TI is learned from the RAM 132. In step S53, according to the RC pointer 161, the RAM 132
Read one T from. In step 354, the time is determined from the previous data to determine the baseline temperature, T,. Detect. In step S55, ΔT (figure $17) is calculated. In step 356, ΣΔTb (integral) is calculated.

Steps S57 and S58 show control for dealing with the case where ΔTb is calculated due to noise in T. If it is noise, △T of this noise is the previous △
Although it increases compared to T, it will decrease someday, so the maximum value at the time of increase is detected, and if the maximum value is smaller than the threshold a, it is determined to be noise and the integral ΣΔTb is cleared in step S59. do. Δd in step S57.

If it has further increased, it cannot be determined that it is noise, and the process advances to step S61. If it is determined to be noise,
In step S60, pointer RC is incremented by a predetermined amount. This b is the approximate time width of the noise component, which is known from experience.

Step S61 determines whether the thermodilution curve has converged to Tbo. That is, the above steps are repeated and the integration continues until convergence.

Next, a case will be described in which the 5TART switch 72 is not pressed in step S41. This control starts integration when it is determined that the change in Tb is a predetermined change. Note that the 5TART switch 72 in step S41
Since the pressing of is detected by an interrupt, step 34
If the above-mentioned interrupt occurs between step S2 and step S47, control is forcibly shifted to step S50. Now, in step S42, Tb is stored in RAM1 according to the RC pointer 161.
Read from 32. In the loop of step S42 → step 343 → step S44 → step S42, since the change in Tb is captured from the moving average (16 samples) in this embodiment, the required number of samples is stored in the memory 13.
It is meant to be obtained from 2. 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 Tb(n) is determined. In step 346, the previous moving average value Tb(n-1)
Find the difference between When this difference is greater than a predetermined threshold, it is determined that the change in blood temperature is due to the injection of the indicator fluid, and
In step S49, time t at the time of this change is calculated.

The subsequent control is the same as that using the 5TART switch 72 described above. If it is determined in step 347 that the change is less than the threshold value, the current average value Tb(n) is moved to the previous average value Tb(n-1) storage area in step S48.

Returning to the explanation of step S63. Now, as mentioned above,
According to the Stewart-Hamilton equation, S t-cl. (Tb-Tt). ■1 where, CO: cardiac output, SI: specific gravity of injected liquid CI: specific heat of injected liquid, ■l: injected liquid Amount Tl: Temperature of injected liquid, Tb: Temperature of blood Sb: Specific gravity of blood, Cb
: Specific heat of blood. The above formula becomes (Tb-Tt)CO=A. Here, SI-CI-VIA=b-Cb. In this correction constant A, S +, S b, CIl
+c 1 etc. are fixed, but V is affected by the fact that even if the indicator liquid is injected, it remains in the catheter and does not flow out into the blood. That is, the above V is only a nominal value. Conventionally, A was determined from the Edwards equation as described above, but in this embodiment, with the aim of improving the reliability of operation by the operator, this correction constant A is tabulated (see Fig. 12). ) and stored in the ROM 131. When subtracting one correction constant A from this table, as shown in FIG.
The inner diameter Fr of the catheter 4 and the nominal liquid injection volume ml manually entered from 0 are used as address data. The correction constant data stored in the above table is obtained in advance from actual measurement results obtained when various amounts of injected fluid are changed for catheters of various sizes. 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. In step 361 and above,
When the calculation of the integral of ΣΔTb is completed, the inner diameter Fr of the catheter is set and inputted from the switches 59 and 60 as described above in step S63.

The correction constant A is read out from the table (FIG. 12) stored in the ROM 131 based on the indicated liquid amount m1 and the like.

In step S64, an initial cardiac output value Co is calculated based on the Stewart-Hamilton equation described above. In step S65, these values are outputted onto the plotter 50 as shown in FIGS. 4 and 5, for example.

<Measurement of continuous Co> First, the principle by which COI can be calculated continuously will be explained. If the resistance value of the thermistor 1 is Rt, and the current value given to the thermistor 1 by the constant current circuit 111 is IC, then
When the thermistor 1 is heated, the amount of heat generated per unit time is 1c2·Rt. If the heated thermistor 1 is placed in blood at a blood flow velocity V, the heated thermistor 1 will be cooled down depending on the blood flow velocity V. The amount of heat cooled by blood flow is Tb, which is the blood temperature, and Tb, which is the heated thermistor temperature.
If the t1 proportionality constant is K, then K-v ・ (Tt ``rb).Now, the temperature of the thermistor 1 must be maintained at a temperature such that the amount of heat generated by heating and the amount of heat cooled are equal. This temperature is the thermal equilibrium temperature.

If the above is expressed in a formula, it becomes the following formula (2).

I c”・Rt = K−V・(Tt −Tb
)... (2) From equation (2), equation (3) for determining the blood flow velocity V is derived.

■ = (1/K) (Ic"Rt)/("rt -T
b)...(3) That is, data Rt obtained from thermistor 1.

From Tt and the blood temperature Tb obtained from the thermistor 2, the blood flow velocity V is determined. Note that since the heating thermistor 1 is driven by the constant current circuit 111, the potential difference Vo between both ends of the lead wire of the heating thermistor 1 may be detected instead of detecting the resistance value. Details of this case are described in the above-mentioned Japanese Patent Laid-Open No. 125329/1983. Further, although the constant current value IC can be applied even if the current of the constant current circuit 111 is detected, it is also possible to provide it in the ROM 131 as a constant term in the same way as the proportional constant.

Now, when the blood vessel 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 value V as shown in equation (4).

CO engineering s-v - (4) Therefore, from the initial cardiac output value Co and the initial blood flow velocity value V,
The blood vessel cross-sectional area S is determined according to equation (4), and this value S is held in the measurement recording circuit 130 as a calibration value (parameter). In this way, once the parameter S is determined,
The CPU 133 can obtain a continuous cardiac output value COI by multiplying the continuously measured blood flow velocity Ml by the parameter S. That is, Co,=
S −Vi = (S/K)・(I c”・Rt)/(Tt −T
h)...(5).

FIG. 14 shows a control procedure for the CPU 133 to calculate this Co and store it in the RAM 132. Before starting this control, the initial cardiac output Co has already been measured.

Steps 381 to 385 are the above-mentioned parameter S.
This is a control that seeks .

In step S80, it is determined whether the measuring device 100 is in continuous mode. A transition to this mode is made by pressing the C0NT I NUOUS switch 64.

If it is continuous mode, in step S81, the local CP
Instruct U105 to heat the thermistor 1 via the optical communication path. In step S82, the thermistor 1 waits for the thermal equilibrium between heating and cooling to be reached. Eventually, local C
Tt, R-Tb, etc. are sent from PU, and the 11th
The information is stored in the RAM 132 in chronological order according to the flowchart shown in the figure. 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 determined from the relationship between the initial cardiac output value CO and the blood flow velocity V according to equation (4). In this way, preparations for continuous CO1 measurements were completed. The following controls are the first CO and the CO at any time.

Since this is common in the calculation of , COI calculation control for Vl at an arbitrary time will be explained.

In step S86, it is checked whether the continuous mode has been canceled. This is because the parameter S representing the blood vessel cross-sectional area usually changes over time. Therefore, - cross-sectional area of the dish tube S
Even if S is 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, the ico for initial heartbeat is appropriately measured by the thermodilution method in preparation for the next continuous COI measurement.

Unless the continuous mode is canceled, the process proceeds to step S87 and calculates CO jujube=V plate·S. In step 388, Vl and COr are
Calculates the average value for the minute. These values are stored in RAM132
It is stored in the area 132C within.

Then, in step S90, the RC pointer is incremented by 1 in order to calculate the next COI.

In this way, each time Tt, Rt, Tb, etc. are sent, c
ol etc. can be calculated continuously.

In this way, the cardiac output C01 could be measured by measuring only the blood flow velocity v1.

<Data Recording> In addition to recording thermodilution curves and thermodilution values as shown in Figs. a continuous recording function to output (by switch 56), a playback function to output measured values for the past 30 minutes to the plotter 50 (by switch 55),
Progress chart output function (by switch 54) that outputs the past 12 hours' measured values (average values every 3 minutes) to the plotter 5o
There are output functions such as

The output format by continuous recording and recording/reproduction is as shown in FIG. 6 (paper feeding speed 10 m5/min) and FIG. 7 (20 mS/hour).

Figure 8 shows the output format of the progress chart. In this progress chart, 3
Co (=COt) and blood temperature BT (=Tb) every hour
Record the value of along with the graph.

Now, this kind of recording is done in continuous mode (CONTINUOUS mode).
(when the OUS indicator 64 is lit), therefore, in parallel with the output to the plotter 5°, it is necessary to take in data from the local CPU 105 and perform calculations/storage of Co, etc. For this control, access to the RAM 132 uses a PC pointer 162 for plotter output, an Sc pointer 160 for data acquisition, and an RC pointer 160 for calculation/storage, as shown in FIG. 10B. .

<Substitute for injection liquid temperature> Since the indicator liquid to be injected is placed in a water-cooled container, it can be said that its temperature is almost determined by the ice-cooling temperature. Therefore, when this water 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 regarded as the liquid temperature TI, and used for calculating 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. E corresponding to this zero current.

When the local CPU 105 receives
The PU sends a signal to that effect to the main CPU 133. Alternatively, the CPU 105 converts El corresponding to this zero current into an impossible value when converting it to the temperature T1, 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. Main C in Figure 13
Instead of step S52 in which the PU 133 reads T from the RAM 132, in step 5100 of FIG. 15, it is determined whether the TI sent from the local CPU 105 is data indicating that the probe 12 is not connected. do. If the data indicates the connection state, step 510
1, the TI in this RAM 132 is used for measurement. If it is not connected, the data set in the switch 75 is taken in as TI in step 5102.

Measurement of Relative Change in Cardiac Output> The embodiment of the measuring device described above actually determines the initial cardiac output value CO by the thermodilution method, and calculates the value from the relationship between this CO and the initial blood flow velocity V. After determining the parameter S, the cardiac output CO can be continuously calculated by simply measuring the blood flow velocity v1 at any time.
It is distinctive in that it requires I. That is, C08ccvl, and changes in Vl reflect relative changes in CO,.

Therefore, if you record the change in Vl, it will be directly reflected in the CO
This means that the relative change in I has been recorded. On the other hand, the approximate value of the parameter S is known if the subjects are the same and the measurer is aware of the parameter S during 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, thereby making it possible to omit measurement of the initial cardiac output value CO by thermodilution.

<Application to other dilution methods> As is clear from the explanation so far, the continuous cardiac output measurement of 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 CO1 can be continuously determined by simply measuring the blood flow velocity v1. 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; It is also possible to obtain the quantity Co. In this case, in the dye dilution method, the amount of dye in the blood is measured by measuring changes in illuminance, such as at the earlobe, and in the electrolytic dilution method, changes in blood resistance are measured using two electrodes installed in a catheter. By this, the cardiac output CO is obtained.

In other words, the amount of data (for example,
The input function (Fr, ml) can also be applied to general indicator dilution methods using catheters. Further, the automatic measurement start function (2) is directly applied to detecting the points of change in the above-mentioned changes in illuminance and changes in resistance value. In addition, the continuous cardiac output measurement function (■) calculates the parameter S based on the initial cardiac output MCO obtained by the general indicator dilution method, and then calculates the parameter S from the blood flow velocity v at any time. It is also applicable to calculating co.

Furthermore, as another modification and modification, we propose the following mechanism for detecting the connection of the temperature probe 12. 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 back. When the protrusion is pressed, the end of the protrusion is arranged to provide a ground signal to the measurement circuit 120, for example. The measuring circuit 120 can determine whether the prop 12 is connected or not connected based on the presence or absence of this ground signal. In addition, the above protrusion is
It 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, there is a method of controlling the thermistor salt at an upper limit of 42° C., which does not affect living organisms, and measuring the current. Further, the blood flow rate sensor is not limited to a thermistor, and other means may be used.

[Effects of the Invention] As explained above, according to the device for continuously measuring relative changes in cardiac output of the present invention, there is no need to even measure the relationship between cardiac output and blood flow velocity. This allows continuous measurement of changes in relative cardiac output values.

[Brief explanation of the drawing]

1A, 1B, and 1C are a plan view, a front view, and a rear view of a measuring device according to an embodiment, and FIG. The overall perspective view, main part sectional view, and opening sectional view of the catheter used; Figure 3 is a procedure diagram explaining the operating procedure of the measuring device of the example; Figures 4 and 5 show the thermodilution method using the example device. Figures 6 to 8 are diagrams showing examples of output results when cardiac output is measured based on the results of continuous measurement, and Figure 9 is a measurement The circuit diagrams of the main parts of the device, Figures 10A and 10B are diagrams explaining the RAM management within the measuring device, Figures 11, 13A, 13B, 14, and 15.
The figures are a flowchart showing the control procedure according to the embodiment, Figure 12 is a diagram showing a table storing the correction constant A, and Figures 16 and 17 are the principles of cardiac output measurement using the conventional thermodilution method. FIG. In the figure, 1.2, 12a... Thermistor, 4... Catheter, 6, 8, 10, 13. 14... Tube, 7°9.
11, 15. 16... Connector, 12... Infusion liquid?
FA degree probe, 50... Plotter, 52, 53, 5
4.55, 56, 57.58...Switch, 59°6
0.61, 62.75...setting input switch, 64.
65, 66. 67. 70. 72... Switch/indicator, 68... 4-digit LEI) display, 69...
3-digit LED display, 71...LED bar graph, 73
... Catheter connection connector, 74 ... Temperature probe connection connector, 1oo ... Measuring device, 101°11
2... Constant voltage circuit, 111... Constant current circuit, 1゜2
... Injection liquid temperature detection circuit, 103 ... Analog switch, 104 A/D converter, 105, 133-...C
PU, 106,131・ROM, 107.132...
It is RAM.

Claims (2)

[Claims] (1) A blood flow velocity measurement means for measuring a blood flow velocity value, an input means for inputting an arbitrary numerical value, and based on the blood flow velocity value at each time measured by the blood flow velocity measurement means and the numerical value. 1. A device for continuously measuring relative changes in cardiac output, comprising cardiac output calculation means for continuously calculating relative changes in cardiac output values as time passes. (2) The device for continuously measuring relative changes in cardiac output according to claim 1, wherein the numerical value is a cross-sectional area value of a blood vessel.