JPS63216532A - Living body data measuring apparatus - 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 Application Field] The present invention relates to a biological information measuring device, and particularly to a biological information measuring device that measures biological information by bringing a probe portion into contact with a biological surface or directly inserting it into a biological body. Regarding.

[Prior Art] Generally, safety measures are more important in this type of biological information measuring device, especially in a medical measuring device, than in other industrial measuring devices. Since this type of biological information measuring device uses a commercial AC power source, there is a high possibility of receiving an electric shock from this commercial AC power source. The most dangerous thing about this electric shock is ventricular fibrillation caused by the alternating current flowing through the human body, and ventricular fibrillation can lead to death if left untreated for 2 to 3 minutes. In particular, in the case of measuring cardiac output, which involves inserting a catheter directly into the heart, safety must not be taken into consideration because, in the event of an accident, all of the current that flows through the catheter will flow through the heart. must not. In this case, it is reported that the safe value of the current flowing directly to the heart is 10 μA to 20 μA. Furthermore, there is a report that the resistance is 500 μA or less even when passing through the skin, which has a relatively high resistance.

Conventional safety measures include, for example, using a double-insulated power transformer to sufficiently isolate the power supply circuit of the device body from the commercial AC power circuit, and grounding the device body. However, relying on insulation at one location in the power transformer is not an adequate safety measure, considering the layout of the equipment in contact with the power supply, the aging of the equipment, and the environment in which it will be used. do not have.

Furthermore, the conventional safety measure was to ground one side of the measurement electrode circuit. However, the human body is not always at ground potential, and forcibly placing the human body at ground potential may even be dangerous.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned drawbacks of the prior art, and its purpose is to provide a biological information measuring device that is safer under all measurement conditions and environments. Our goal is to provide the following.

[Means for Solving the Problems] In order to achieve the above object, the biological information measuring device of the present invention includes an analog detection means for detecting analog information regarding a living body, electrically connected to the analog detection means, and an A/D conversion means for converting the analog detection signal into a corresponding digital signal; an information processing means for processing analog information regarding the living body based on a digital signal outputted by the A/D conversion means; The outline of the present invention is to include a signal transmission means interposed between the D conversion means and the information processing means and for exchanging signals between the two means in an electrically insulated state.

Preferably, one aspect of the signal transmission means is light as a signal transmission medium.

[Function] - In such a configuration, the analog detection means detects analog information regarding the living body. The A/D conversion means is electrically connected to the analog detection means and converts the analog detection signal into a corresponding digital signal. The information processing means processes analog information regarding the living body based on the digital signal output from the A/D conversion means. The signal transmission means is interposed between the A/D conversion means and the information processing means, and exchanges signals between the two means in an electrically insulated state. Preferably, the signal transmission means uses light as a signal transmission medium.

[Description of Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a continuous cardiac output measuring device according to an embodiment of the present invention. In the figure, reference numeral 1 denotes the main body of a continuous cardiac output measuring device, to which exchangeable cardiac output measuring catheters 2 and 7 are connected from the outside. Among these, the catheter 2 is a catheter for injecting an indicator and detecting the temperature of the indicator based on the thermodilution method, and includes a temperature-sensitive element (thermistor, etc.) 3 for detecting the temperature of the indicator and a temperature-sensitive element 3 to detect variations in the characteristics of the temperature-sensitive element. A chemical liquid temperature measurement probe circuit including a correction resistor 4 for correction is provided. This chemical solution temperature measurement probe circuit is electrically connected to the measurement section 20 of the main body 1 via connectors 5 and 6, and is located in the right atrium of the heart when measuring cardiac output. Reference numeral 7 denotes a catheter for detecting blood temperature and blood flow velocity, and inside thereof there is a thermistor 8 for detecting the temperature of a medicinal solution (blood) thermodiluted in the right atrium and right ventricle, and a thermistor 8 for detecting variations in the characteristics of the thermistor 8. A blood temperature probe circuit consisting of a correction resistor 9 for correction, and a thermistor 10 (preferably a self-heating thermostat) located about 5 to 20 mm downstream in the blood flow direction with respect to the thermistor 8 and detecting the blood flow velocity by a so-called thermal equilibrium method. Equipped with a blood flow rate temperature measurement probe circuit consisting of a type thermistor. These blood temperature measurement probe circuit and blood flow rate temperature measurement probe circuit are electrically connected to the measurement section 20 of the main body 1 via connectors 11 and 12, and are located in the pulmonary artery when measuring cardiac output.

Incidentally, the catheter 2 and the catheter 7 are manufactured so as to be integrated in appearance. Alternatively, only the indicator injection mechanism of the catheter 2 is provided integrally on the catheter 7 side, and the remaining medical solution temperature measurement probe circuit (catheter 2) is constructed independently and inserted into the indicator injection tank. Regarding the construction and usage of a portion of such a catheter, reference may be made to Japanese Patent Application No. 61-48681.

The main body 1 can be broadly divided as follows. That is, the measurement unit 2 performs various temperature measurements via the catheters 2 and 7.
0, and an opto-isolation communication circuit 40 that transmits measurement data etc. measured by the measurement section 20 by optical means.
Based on the measurement data input via the opto-isolation communication circuit 40, the cardiac output value is calculated intermittently by the thermodilution method or continuously by the blood flow velocity measurement method, and the calculation result is calculated. , a display 50 that displays the cardiac output value calculated by the main CPU 30 , and a power supply section 70 that supplies DC power to each section of the main body 1 .

In the measurement unit 20, 21 is an injectate temperature detection circuit, which detects the temperature T+ of the indicator discharged from the opening of the catheter 2 into the right atrium, and outputs a corresponding voltage signal 1. Alternatively, insert it into the indicator injection tank and check the indicator temperature T1.
Detects and outputs the corresponding voltage signal ■. 22 is a blood temperature detection circuit which detects the temperature TP of the medicinal solution (blood) at which the indicator ejected into the right atrium is thermally diluted before reaching the pulmonary artery, and outputs a corresponding voltage signal VP. 23 is an equilibrium temperature detection circuit, for example, a self-heating type thermistor 1
The equilibrium temperature between the amount of heat added by 0 and the amount of heat taken away by surrounding blood is detected, and the corresponding voltage signal V c (V C
L+V eM+V co) is output. 26 is a local CPU, which outputs various control signals CNT for executing the instructions to each detection circuit according to instructions from the main CPL 130, and controls the infusion temperature detection circuit 21, blood temperature detection circuit 22 and equilibrium In addition to controlling the above-mentioned measurement operation in the temperature detection circuit 23, each input signal of the analog switch 24 is selected by the selection signal 5ELV, and the selected signal is converted into digital data VD by the A/D converter 25. It is taken into the CPU 26. Further, the local CPU 26 has an internal serial communication function, and receives various command signals RT from the main CPU 30 via the serial communication function, and also transmits the digital data VD taken in from each of the detection circuits to the serial transmission data T8. and sends it to the main CPU 30.

The purpose of the opto-isolation communication circuit 40 is to exchange the above-mentioned signals between the measurement section 20 and the main CPU 30.
This must be done in a completely electrically insulated state. For example, as shown in FIG.
0 is a photodiode circuit 41 provided on the measurement unit 20 side
and an optical transmitting/receiving circuit 40A consisting of a phototransistor circuit 46 and an optical transmitting/receiving circuit 40B consisting of a photodiode circuit 44 and a phototransistor circuit 43 provided on the main CPU 30 side, which are electrically insulated from each other, and a signal between them is provided. Optical fiber glasses 42 and 45 are interposed as transmission media. Therefore, the electrical connection between the DC power circuit of the measurement unit 20 and the DC power circuit of the main CPt 130 is completely cut off, so there is no fear that any closed loop will be formed between the human body and the main CPU 30 side, and it is safe. Measurements can be made.

In the main CPU 30, each block described later indicates various functional blocks realized by the main CPU 30 executing the programs shown in FIGS. 6 to 8. Here, 31 is a thermodilution cardiac output calculation means, which indicates the temperature of the indicator injection solution T! The thermodilution cardiac output C0 is calculated by inputting the thermodilution blood temperature TP and the thermodilution cardiac output C0, and the result is output.

32 is a blood flow velocity calculating means, which is a thermistor 1 during heating.
The blood flow velocity V is calculated by continuously inputting the thermal equilibrium temperature Tc of 0 and the blood temperature TP, and the result is output. 33 is a continuous cardiac output calculation means, which calculates the thermodilution cardiac output C0 calculated by the thermodilution cardiac output calculation unit 31 based on the thermodilution method and the blood flow rate calculation unit 32 calculated. The blood vessel cross-sectional area parameter S of the pulmonary artery is calculated based on the flow velocity V and is held in a register, and the blood flow velocity V measured and obtained by the blood flow velocity calculating means 32 is subsequently calculated and the blood vessel cross section held in the register. Continuous cardiac output C based on area parameter S
o” and outputs the result.

In the power supply section 70, 71 is an alternating current (AC) power transformer, which receives an external AC input voltage (, toov, 50/
60H2, etc.) and converts it into a predetermined AC output voltage. The primary winding and the secondary winding of the power transformer 71 are only magnetically coupled, which allows the main body 1 and the external A
Cut off the electrical connection with the C input circuit. A DC power supply circuit 72 smoothes and stabilizes a predetermined AC output voltage of the power transformer 71 and converts it into a DC voltage.
Also, the main CPU 30 is supplied with a direct current voltage DCB. The purpose of the DC70C converter circuit 80 is to supply power from the power supply section 70 to the measurement section 20 in a completely electrically insulated state. For example, as shown in FIG. 5, the DC70C near :,/verter circuit 80 includes an inverter circuit 81 that once converts the DCA input supplied from the power supply section 70 (80B) side into AC power and outputs it, and a measurement section 20.
A DC constant voltage circuit 83 that supplies a stabilized DC DCC output is provided on the (80A) side and is electrically insulated from each other, and serves as a power transmission means from the inverter circuit 81 to the DC constant voltage circuit 83. , - a transformer 82 in which the primary winding and the secondary winding are only magnetically coupled;
intervene. Therefore, the electrical connection between the DC power supply circuit of the measuring section 20 and the power supply circuit of the power supply section 70 is completely cut off.
Therefore, there is no fear that any closed loop will be formed between the human body and the main body 1 side or the external AC input circuit, and safe measurements can be performed.

FIG. 2 is a circuit diagram showing details of the blood temperature detection circuit 22 of the embodiment. Note that the infusion liquid temperature detection circuit 21 is substantially the same as the blood temperature detection circuit 22, so a description thereof will be omitted.

In FIG. 2, the local CPU 26 turns on the relay circuit 228 in advance using a control signal 5TRI. As a result, the control signal RLC2 of the relay circuit 228 is output, and the contacts a, b, and C of the current cutoff circuit 222 are closed. Further, the local CPU 26 gives a selection signal to the relay circuit 228 in advance using a control signal 5ELS. As a result, the relay circuit 228 outputs the selection signal RLC1,
Contacts d and e of the current cutoff circuit 222 are connected to the lower side as shown in the figure.

In this state, the constant voltage circuit 221A applies a constant potential vH to the thermistor 8.

That is, the driver (DR) 221a of the constant voltage circuit 221A
By referring to the input reference voltage Vo, the potential at point p is approximately ■. Drive as you like. Therefore, the potential at point p is always kept at a constant potential VH (approximately V). Further, the constant voltage circuit 221B applies a constant potential (2) to the correction resistor 9.

That is, the driver (DR) 221b of the constant voltage circuit 221B
is driven so that the potential at point q becomes approximately GND by referring to the human-powered reference voltage GND. Therefore, q
The potential at the point is always kept at a constant potential VL (approximately GND). In this way, a constant voltage (VH-VL) is always applied to the series circuit of the thermistor 8 and correction resistor 9 of the catheter 7.

When measuring cardiac output, the thermistor 8 changes its resistance value RPAT according to the thermodiluted blood temperature, and changes the constant voltage (VH-Vt, ) to the corrected resistance value RPAT.
By dividing S and its divided voltage (blood temperature signal)
Output VPAT to analog switch 22S. This blood temperature signal V PAT is selected by the control signal 5ELA from the local CPU 26, and is selected by the analog switch 22.
5 and the differential amplifier 22 of the blood temperature amplification circuit 226.
Input to the (-) terminal of 6a. On the other hand, the reference voltage generation circuit 227 receives a control signal 5ELR from the local CPU 26.
The constant potential VH is selected according to the reference voltage V RE
A signal P is input to the (+) terminal of the differential amplifier 226a.

As a result, the (+) terminal and (−) terminal of the differential amplifier 226a
) The content of the divided voltage V PAT applied between the terminals is determined by (VH-V+,) RPAT RPAT + RPAS. As is clear from equation (1) above,
When such a divided voltage VPAT is adopted, since the nonlinear resistance value RPAT of the thermistor 8 is in the denominator and numerator,
The linearity of the probe circuit and the resistance value for a predetermined temperature are corrected. The differential amplifier 226a has a divided voltage V P
Amplify AT and output blood temperature signal vP.

Incidentally, when the probe circuit is driven by a constant current IC, the thermistor 8 and the correction resistor 9 may be connected in parallel for correction. As a result, the contents of the back electromotive force V PAT' applied between the (+) and (-) terminals of the differential amplifier 226a are: RPAT + RPA! Determined by J. Similarly, as is clear from the above equation (1'), since the nonlinear resistance value RPAT of the thermistor 8 is in the denominator and numerator, the linearity as a probe circuit and the resistance value for a predetermined temperature are corrected.

The characteristics of the thermistors 3 and 8 in the example are, for example, B25-
45 = 3970, R(37) = 40, and the solenoid size is 0.50'xo, 16wxO, 15t (
The unit is mm). Further, the characteristics of the thermistor 10 are, for example, B25-4s = 3500K.

R(37)=1000Ω, and its magnitude is 1.1
8'Xo, 4wX0.15t.

However, the present invention is not limited to these thermistor characteristics. That is, it is possible to use different types of catheters. However, even if there are variations in the non-linear characteristics and resistance values for a given temperature of the thermistors 3 and 8, or even if the standards of the thermistors themselves are different, the correction resistors 4 and 9 provided in each catheter 2 and 7 in advance Since the resistance-temperature characteristics are corrected, the temperature-resistance characteristics viewed from the main body 1 side can be treated as the same.

Moreover, it is preferable that the calorific value of the thermistor 10 in the case of a self-heating type is in the range of 0.01 to 50 Joules. A calorific value higher than this may raise the blood temperature or damage the blood vessel wall, and a lower calorific value lowers the detection sensitivity, which are both undesirable.

On the other hand, the leakage current detection circuit 223 detects whether or not there is a leakage in the current flowing through the constant voltage loop. The constant voltage loop includes two current detection resistors Rps of the same value inserted in series in the loop, and the differential amplifiers (DAMP) 223a and 223b of the leakage current detection circuit 223 are connected to each resistor RPS.
The back electromotive force (IO・Rps) and (ro
'・Rps) is differentially amplified. In this case, if there is no leakage in the constant voltage loop, the source current ID and the sink current I0' are equal. Therefore, the differential amplifier 22
The respective output voltages of 3a and 223b are also equal, and the differential amplifier 2
The output signal VPL of 33c is approximately OV. However, if a leak occurs in the constant voltage loop through catheter 7, ID>
In' (outflow) or 1, <1. ” (inflow), and each output of the differential amplifiers 223a and 223b becomes (
II)・RPs)>(Io'・Rps) or (I
The relationship is as follows: o-Rps)<(ro''・RPII).As a result, the output signal of the differential amplifier 233c is
It fluctuates.

Therefore, the local CPU 26 uses the reference voltage generation circuit 227.
By generating an appropriate reference voltage VFRε,
It is possible to periodically check the extent and condition of leakage current. When local CPU 26 determines the leakage current, it sends control signal R3RI to relay circuit 228. As a result, the relay circuit 228 outputs the control signal RLC2, and the contacts a'-c of the current cutoff circuit 222 are immediately opened. Therefore, the current supply to the probe circuit is immediately cut off.

In this way, negative effects on the human body are removed.

Note that it is also possible to detect the current using a Hall element or the like. Also, when biasing the probe circuit with alternating current,
Current is detected by a coil wrapped around a current loop.

On the other hand, the reference resistance circuit 224 outputs a reference temperature signal V PAT' for calibrating the blood temperature detection circuit 22. The local CPU 26 sets the reference resistance circuit 224 to a predetermined temperature T or T2 by sending control signals SF and LP.
A reference temperature signal V PAT' corresponding to , etc. is output. Each of the divided resistors R8 to R4 in the reference resistance circuit 224 has a predetermined resistance value, and the resistance value hardly changes depending on the temperature. Furthermore, the constant potentials vH and ■ are added to each series resistance network (R1 and R2 or R3 and R4, etc.), and therefore, under the same conditions as the probe circuit of the catheter 7, the analog circuit network (analog switch 25 , blood temperature detection circuit 226, etc.) and correct the actual detected temperature. That is, when the temperature T1' is detected when the predetermined temperature T is generated, the information of the error ΔT=(T+'-T'+) is sent to the main CPU.
3o, and use this to shift or correct the temperature reference table, etc.

In addition, the local CPU 26 also controls the relay circuit 2 before starting measurement.
A control signal 5ELS is sent to 28 to connect contacts d and e of the current cutoff circuit 222 to the upper side of FIG. As a result, the power supply path to the thermistor 8 is opened, and instead a constant voltage (VH-VL) is applied to the correction resistor 9 via the reference resistor R0. In this case, the reference resistance value R8 is the main CP
Although it is known and constant within U30, the corrected resistance value RPAS varies depending on the content of correction to the thermistor 8. Therefore, the local CPU 26 (main CPU
U30) can examine the characteristics of the thermistor 8 by taking in the divided voltage V PAT at this time.

For example, if the divided voltage V PAT varies within a predetermined range, it can be determined that the types of thermistors 8 (types of catheters 7) are the same. However, the divided voltage V P
When AT is extremely different, it can be determined that thermis 8 belongs to a different category. For main body 1, in advance,
When such a different type of catheter is scheduled to be used, the main CPU 30 shifts or selects the temperature reference table according to the determination result.

Furthermore, the divided voltage V PAT is the reference voltage V REF (=V
H), it can be determined that the probe circuit inside the catheter 7 is broken or that the catheter 7 itself is not connected. In this way, local CPO26 (May:
/CPU 30) sequentially checks the status of each detection circuit before, during, and after measurement and can automatically take action.

FIG. 3 is a circuit diagram showing details of the equilibrium temperature detection circuit 23 of the embodiment.

The local CPU 26 turns on the relay circuit 235 in advance using the control signal STR. As a result, the relay circuit 23
5 outputs a control signal RLC3 to close contacts f and g of the current cutoff circuit 232. Also, local CPU
26 sets the magnitude of constant current Ic of constant current circuit 231 using control signal 5ELIC. As a result, the constant current circuit 231 supplies a constant current IC set to a constant current loop including the thermistor 10. Also, this allows the thermistor 1
0 is constant current I. At the same time, the resistance value RCFT is changed according to the equilibrium temperature of the amount of heat added to the surrounding blood and the amount of heat taken away by the surrounding blood, and the detection voltage (engineering/RCF) at the equilibrium temperature is changed. is applied to the input of the differential amplifier (DAMP) 234a of the balanced temperature amplification circuit 234.

The differential amplifier 234a differentially amplifies the detection voltage (Ic-RCP?) to produce an output voltage (■) at the equilibrium temperature. form. Resistors RL, RM, R) provided in the output circuit of the differential amplifier 234a
l is a dividing resistor that divides the output voltage VCL, and the measurement range can be changed to the medium range VC depending on the thermal equilibrium temperature.
M or high range VCH, and the maximum resolution of the A/D converter 25 is made to correspond to each measurement range.

Also, set constant current ■. The size of the main CPU is 30
The main CPU 30 calculates the thermal equilibrium resistance value RCFT of the thermistor 10 as RCF = V c
/ I c.

On the other hand, the leakage current detection circuit 233 detects the constant current I of the constant current loop.
Detect whether there is a leak in c. The constant current loop includes two current detection resistors RCS of the same value inserted in series, and a differential amplifier 233a of the hot water current detection circuit 233.
and 233b differentially amplify the back electromotive force (I c −Rcs) and (Ic′·Rcs) appearing across each resistor RC3. In this case, if there is no leakage in the constant current loop, the source-side current I and the sink-side current Ic' are equal, and therefore the outputs of the differential amplifiers 233a and 233b are also equal. Therefore, the inputs of the comparator (CMP) 233c are equal and the output signal ROFF is approximately OV. Therefore,
Relay circuit 235 remains ON. However, if leakage occurs in the constant current loop through catheter 7, Ic>
The state becomes Ic' (outflow) or Ic<Ic' (inflow), and each output of the differential amplifiers 233a and 233b becomes (I
c - Rcs)>(IC'・RCI+) or (Jc
-Rcs)<(Ic'・Rcs). As a result, the output signal ROFF of the comparator 233c is ±VR
In either case, if the predetermined range is exceeded, the relay circuit 235 is immediately turned off. In addition, the relay circuit 235 outputs the control signal RLC3 to immediately open the contacts f and g of the current cutoff circuit 232, and the catheter 7
Cut off the current supply to. In this way, negative effects on the human body are removed.

Note that the output signal ROFF of the leakage current detection circuit 233 may be inputted to the analog switch 24 in FIG. 1 so that the local CPtJ (main CPU 30) can remotely monitor it.

In addition, the thermistor 10 is not limited to the self-heating type thermistor as described above, and may be a general thermistor.
It may be provided near the heater so that it is heated in the constant current IC by a separate heater or the like. However, a self-heating type thermistor is advantageous because it is structurally easier to incorporate and allows for structurally stable heat generation and detection.

Returning to FIG. 1, in the main CPU 30, the thermodilution cardiac output calculation means 31 inputs the injected liquid temperature T of the injected liquid temperature detection circuit 21 and the blood temperature T of the blood temperature detection circuit 22, and - Calculates the cardiac output C8 by the thermodilution method based on equation (2) using the Hamilton method, and outputs the calculation result to the continuous cardiac output calculation means 33.

here, CO: cardiac output SL = specific gravity of injected liquid CI = specific heat of the injected liquid Vl: Injected liquid volume T: Injected liquid temperature TP: Blood temperature SP: Specific gravity of blood CP: specific heat of blood 1': △TPdt・area of thermodilution curve It is.

The blood flow velocity calculation means 32 inputs the blood temperature TP of the blood temperature detection circuit 22 and the equilibrium temperature "rc of the equilibrium temperature detection circuit 23, calculates the blood flow velocity V based on equation (3), and continuously calculates the calculation result. It is output to the cardiac output calculation means 33.

here, K: proportionality constant It is.

The continuous cardiac output calculation means 32 first calculates the blood vessel cross-sectional area S of the pulmonary artery based on equation (4) from the cardiac output C8 and blood flow velocity V obtained by the thermodilution method, and stores the blood vessel cross-sectional area S in the parameter register S. to hold.

S=°Co/v (4) Since the blood vessel cross-sectional area S of the pulmonary artery mentioned above is considered to be approximately constant for a reasonable period of time, once the parameter S is determined, continuous heartbeat The output amount Co' can be measured.

Therefore, the continuous cardiac output calculation means 32 calculates the continuous cardiac output Co' from the parameter S and the subsequently measured blood flow velocity V based on equation (5), and outputs the calculation result to the display 50. do.

Co'=S-v (5) FIG. 6 is a flowchart of the main routine showing the continuous cardiac output measurement procedure of the embodiment. Note that the processing described below is performed by the local CPU 26 in cooperation with instructions from the main CPU 30.

Step S1 is entered manually by turning on the power to the apparatus or pressing the measurement start button. In step S2, the relay circuit of the detection circuit is turned on. In step S3, the probe circuit of the catheter is connected to the reference resistance side to check whether the catheter is connected. If the catheter is not connected, proceed to step Stt and turn off the relay circuit. Further, in step S12, an error message is displayed to that effect, and in step S13, the buzzer 60 is sounded to call the user's attention. Subsequently, in step S14, an idle routine is executed to wait until the abnormality is removed and the measurement start button is pressed again.

Further, if it is determined in step S3 that the catheter is connected, it is checked in step S4 whether the catheter is a standard type or not based on the reference resistance. If it is not a standard type, the process advances to step S5 and a corresponding temperature table etc. is selected.

If it is a standard type, proceed directly to step S6,
Inspect the probe circuit for leakage current. Once it is determined that there is a leakage current, the process proceeds to step S11, where the relay circuit is turned off and error handling is performed. If it is determined that there is no leakage current, the process proceeds to step S7, and it is determined whether or not the measured value needs to be corrected using the temperature standard voltage of the measuring circuit.

If correction is necessary, the process proceeds to step S8 and the temperature table etc. are corrected. If there is no need for correction, the process proceeds to step S9, and it is determined whether the initial setting flag for the parameter S is ON.

If it is not ON, this corresponds to when measuring the cardiac output of the subject for the first time or when power is turned on to the water device, etc., and the process advances to step S20, where a parameter S setting routine is executed. In this parameter setting routine, the cardiac output C0 is measured and calculated based on the thermodilution method, the blood flow velocity V is subsequently detected, the parameter S is calculated, and the result is stored in the parameter register S. . Further, the initial value setting flag is turned ON and the process returns to step S6. When the process returns to step S9, the initial setting flag is set, so the process proceeds to step S10. Step S1
Step 0 is a step for determining whether it is necessary to update the held parameter S, and this necessity is determined by checking an update request flag (not shown). For example, the update request flag is set as follows. Main CP
A time at which the parameter S needs to be updated clinically is set in advance in a timer (not shown) of U30, and when this time has elapsed, an update request flag is set by a timer interrupt routine or the like. If this update request flag is set, the process advances to step S20;
Parameter setting routine (in this case, update routine)
Execute. When the parameters are thereby updated, the update request flag is reset and the timer is restarted within this setting routine. If No is determined in step S10, the parameter S is valid and reliable, so the process advances to step S40 and a continuous cardiac output measurement routine is executed.

FIG. 7 is a flowchart showing details of the parameter setting processing routine of the embodiment. In step S21, heating of the thermistor 10 is stopped. This step is meaningful when it is necessary to update the parameter S during continuous cardiac output measurement. In step S22, the process waits for a predetermined period of time until the thermistor 10 has sufficiently cooled and no longer has any influence on the thermistor 8. When this predetermined period of time has passed and the influence of heating has disappeared, the process proceeds to step 323, in which a predetermined amount of indicator liquid is injected from the discharge port of the catheter 2.

In step S24, this injection liquid temperature TI is measured. In step S25, the temperature TP of blood that has been thermodiluted before reaching the pulmonary artery is measured. In step 326, the thermodilution cardiac output calculation means 31 calculates the cardiac output C0 using equation (2), and in step S27, the calculated cardiac output value Co is output to the continuous cardiac output calculation means 33. . Although not shown, if necessary, the continuous cardiac output calculation means 33 displays this cardiac output value Co. In this way, the cardiac output C8 is measured by the thermodilution method for the first time or for parameter updating.

Subsequently, in step 528, the thermistor 10 is heated with a constant current IC. In step S29, the blood temperature TP before being heated is measured. In step S30, the equilibrium temperature Tc of the thermistor 10 itself during heating is detected. Also, at this time, the potential difference VC across the thermistor 10 used in equation (3) can be obtained at the same time. In step S31, the blood flow velocity V is calculated by the blood flow velocity calculation means 32 using equation (3), and is output to the continuous cardiac output calculation means 33. In step S32, the continuous cardiac output calculation means 33 calculates the parameter S of the blood vessel cross-sectional area according to equation (4), and stores it in the register S.

FIG. 8 is a flowchart showing details of the continuous cardiac output measurement routine of the embodiment. In step S41, the thermistor 10 is heated with a constant current IC.

In step S42, blood temperature TP is measured.

In step S43, the equilibrium temperature Tc of the thermistor 10 itself during heating is measured. At that time, the potential difference between both ends of the thermistor 10 is ■. can be obtained at the same time. In step S44, the blood flow velocity V is calculated by the blood flow velocity calculation means 32 using equation (3), and outputted to the continuous cardiac output calculation means 33. In step S45, the continuous cardiac output calculating means 33 multiplies the parameter S by the blood flow velocity V to obtain the continuous cardiac output C8'.

In step S46, the determined continuous cardiac output 00' is displayed.

Incidentally, although the above embodiment describes a cardiac output measuring device, the present invention is not limited to this. The present invention can also be applied to various other measurement devices such as electronic thermometers, blood pressure monitors, electrocardiographs, heart rate monitors, and electroencephalographs.

Further, although the above embodiments have described a temperature sensor probe circuit using a temperature sensing element (thermistor), the present invention is not limited to this. The present invention can also be applied to probe circuits using various sensors such as various electrodes, ion sensors, pressure sensors, and optical sensors.

Further, in the above embodiment, the case where a DC bias (constant current, constant voltage) is applied to the probe circuit is described, but the present invention is not limited to this. Alternatively, an alternating current bias or a pulse signal may be applied. The AC bias leakage current can be compared using actual values.

The leakage current of the pulse signal may be compared in a predetermined interval.

[Effects of the Invention] As described above, according to the present invention, a signal transmission system is provided between the A/D conversion means and the information processing means, and the signal transmission between the two means is performed in an electrically insulated state. Since this means is provided, the insulation of the measuring section including the probe circuit is further improved, leakage from the outside can be further prevented, and the structure can be made cheaper.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a continuous cardiac output measuring device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing details of a blood temperature detection circuit 22 of an embodiment, and FIG. 3 is an equilibrium temperature diagram of an embodiment. A circuit diagram showing details of the detection circuit 23, FIG. 4 is a circuit diagram showing an opto-isolation communication circuit according to an embodiment, FIG. 5 is a circuit diagram showing a DC70C converter circuit according to an embodiment, and FIG. 6 is a circuit diagram showing an embodiment. FIG. 7 is a flowchart showing details of the parameter S setting processing routine of the embodiment; FIG. 8 is a detailed flowchart of the continuous cardiac output measurement routine of the embodiment. It is a flowchart which shows. In the figure, 1...Main body, 2, 7...Catheter, 3゜8
．． 10...Thermistor, 4.9...Correction resistor, 5゜6.11.12...Connector, 20...Measuring section, 2
DESCRIPTION OF SYMBOLS 1... Infusion temperature detection circuit, 22... Blood temperature detection circuit, 23... Equilibrium temperature detection circuit, 24... Analog switch, 25... A/D converter, 26... Local CPU, 30... Main CPU, 31... Thermodilution cardiac output calculation means, 32... Blood flow velocity calculation means, 3
3... continuous cardiac output calculation means, 40... opto-isolation communication circuit, 50... indicator, 60...
buzzer, 70...power supply section, 71...power transformer,
72...DC power supply circuit, 80...DC70C converter circuit.

Claims (2)

[Claims] (1) Analog detection means for detecting analog information regarding a living body; A/D conversion means electrically connected to the analog detection means and converting the analog detection signal into a corresponding digital signal; and the A/D conversion means for converting the analog detection signal into a corresponding digital signal. information processing means for processing analog information regarding the living body based on the digital signal outputted by the conversion means; and information processing means interposed between the A/D conversion means and the information processing means, for exchanging signals between the two means. A biological information measuring device characterized by comprising a signal transmission means that performs signal transmission in an electrically insulated state. (2) The biological information measuring device according to claim 1, wherein the signal transmission means uses light as a signal transmission medium.