JPH0613023B2 - Biological information measuring device - Google Patents

Description

The present invention relates to a biological information measuring device, and more particularly to a biological information measuring device for measuring biological information by bringing a probe unit into contact with the surface of a living body or directly inserting it into a living body. Regarding

[Prior Art] Generally, in this type of biological information measuring device, particularly in a medical measuring device, safety measures are more important than in other industrial measuring devices. Since this type of biological information measuring device uses a commercial AC power source, the commercial AC power source is most likely to receive an electric shock. The most dangerous thing in this electric shock is ventricular fibrillation that occurs when an alternating current flows through the human body, and if the ventricular fibrillation is left for 2 to 3 minutes, death occurs. In particular, in the case of cardiac output measurement, for example, in which the catheter is directly inserted into the heart, all the current flowing through the catheter will flow through the heart due to some accident, so safety is not fully considered. must not. In this case, there is a report that the safe value of the current directly flowing to the heart is 10 μA to 20 μA. . In addition, there is a report that it is 500 μA or less even through the skin with relatively high resistance.

Conventional safety measures include, for example, using a double-insulated power transformer to sufficiently cut off the power supply circuit of the apparatus main body from the commercial AC power supply circuit and ground the apparatus main body. However, in this way, relying on the insulation in one place of the power transformer is not a sufficient safety measure in view of the layout problem of the device in contact with the power supply unit, the deterioration of the device, and the operating environment. Absent.

The conventional safety measure is to ground one of the measurement electrode circuits. However, the human body is not always at the ground potential, and forcibly placing the human body at the ground potential may be dangerous.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide a biological information measuring device with higher safety under all measurement conditions and measurement environments. To provide.

[Means for Solving Problems] A biological information measuring device according to the present invention includes a detection unit that contacts a living body to detect its state, and outputs an analog signal corresponding to the state, and an electric signal to the detection unit. A current-carrying means for supplying a predetermined current to the detection means, an A / D conversion means connected to the detection means for converting the analog signal into a corresponding digital signal, and the A / D conversion means outputs Information processing means for processing analog information about the living body based on a digital signal, and coupling means respectively provided for non-electrically coupling the A / D conversion means and the information processing means, The first power supply means for supplying power to the information processing means and the power supplied from the first power supply means, and the input from the first power supply means and the output thereof are magnetically connected. Second power supply means for supplying power to the A / D conversion means and the energizing means, a current value energized to the detecting means by the energizing means, and the energizing means through the detecting means. Difference current detecting means for detecting a difference from the current value fed back to the current value, and when the current difference detected by the difference current detecting means is out of a predetermined range, power supply from the energizing means to the detecting means is cut off. Power cutoff means.

[Operation] In such a configuration, the detecting means is supplied with a predetermined current from the energizing means to detect the state of the living body and outputs an analog signal corresponding to the state. This analog signal is A /
The D conversion means converts the digital signal, and based on the digital signal, the analog signal relating to the living body is processed by the information processing means. The A / D conversion means and the information processing means are electrically coupled by the coupling means, and the information processing means is supplied with power from the first power supply means. On the other hand, the A / D conversion means and the energization means are supplied with power from the first power supply means, and the input from the first power supply means and the output thereof are magnetically coupled to each other. Power is supplied from the power supply means. Here, the difference between the current value applied to the detecting means by the energizing means and the current value returned to the energizing means via the detecting means is detected, and when the detected current difference is out of the predetermined range, the energizing means is detected. Further, the power supply to the detecting means is cut off.

[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 apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 is a main body of a continuous cardiac output measuring device, to which externally connectable catheters 2 and 7 for measuring cardiac output are connected. Among them, the catheter 2 is a catheter for injecting an indicator and detecting the temperature of the indicator based on the thermodilution method. Inside, a temperature sensitive element (thermistor or the like) 3 for detecting the temperature of the indicator and a variation in characteristics of the temperature sensitive element are provided. It is provided with a drug solution temperature probe circuit composed of a correction resistor 4 for correction. This drug solution temperature measuring probe circuit is electrically connected to the measuring unit 20 of the main body 1 via the connectors 5 and 6, and is located in the right atrium of the heart during cardiac output measurement. Reference numeral 7 is a catheter for blood temperature detection and blood flow velocity detection. Inside it, a thermistor 8 for detecting the temperature of a drug solution (blood) thermodiluted in the right atrium and the right ventricle, and a variation in the characteristics of the thermistor 8 are provided. A blood temperature measuring probe circuit composed of a correction resistor 9 for correction and a thermistor 10 (preferably self-heating) which is located 5 to 20 mm downstream of the thermistor 8 in the blood flow direction and detects a blood flow velocity by a so-called heat balance method. Type thermistor). These blood temperature measurement probe circuit and blood flow rate temperature measurement probe circuit are electrically connected to the measurement unit 20 of the main body 1 through the connectors 11 and 12, and are located in the pulmonary artery when measuring the cardiac output.

The catheter 2 and the catheter 7 are manufactured as a single unit in appearance. Alternatively, only the indicator injection mechanism of the catheter 2 is integrally provided on the catheter 7 side, and the remaining drug solution temperature probe circuit (catheter 2) has a separate and independent structure and is inserted into the indicator injection tank. Japanese Patent Application No. 61-48681 can be referred to for the configuration and use of a part of such a catheter.

The main body 1 is roughly classified as follows. That is, the measurement unit 2 that performs various temperature measurements via the catheters 2 and 7.
0, and an opto-isolation communication circuit 40 for transmitting measurement data measured by the measuring unit 20 by optical means.
Based on the measurement data input through 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 divided into a main CPU 30 for outputting the output, a display unit 50 for displaying the cardiac output value calculated by the main CPU 30, and a power supply unit 70 for supplying DC power to the respective units of the main body 1.

In the measuring unit 20, reference numeral 21 denotes an infusate temperature detection circuit, which detects an indicator temperature T _I discharged from the opening of the catheter 2 to the right atrium and outputs a corresponding voltage signal V _I.
Alternatively, the indicator temperature T can be obtained by inserting it into the indicator injection tank.
_I is detected and the corresponding voltage signal V ₁ is output. Reference numeral 22 denotes a blood temperature detection circuit, which is a temperature (T _P ) of the drug solution (blood) that is thermodiluted by the time the indicator discharged into the right atrium reaches the pulmonary artery.
Is detected and the corresponding voltage signal V _P is output. Reference numeral 23 denotes an equilibrium temperature detection circuit which detects the equilibrium temperature between the amount of heat applied by the self-heating type thermistor 10 and the amount of heat taken by the surrounding blood, and outputs a corresponding voltage signal V _C (V _CL ,
V _CM , V _CH ) is output. Reference numeral 26 denotes a local CPU, which outputs various control signals CNT for executing the instructions to the respective detection circuits in accordance with the instructions from the main CPU 30 to inject the infusion solution temperature detection circuit 21, the blood temperature detection circuit 22 and the balance. In addition to controlling the above-described measurement operation in the temperature detection circuit 23, each input signal of the analog switch 24 is selected by the selection signal SELV, and the selected signal is converted into digital data VD by the A / D converter 25. It is taken into the CPU 26. The local CPU26 is provided with a serial communication function therein, the receive various command signals R _T from the main CPU30 through the serial communication function, taken from the detection circuit of the digital data VD serial transmission data T _X To the main CPU 30.

The purpose of the opto-isolation communication circuit 40 is to exchange the above signals between the measuring unit 20 and the main CPU 30.
It is done in a completely electrically insulated state. For example, as shown in FIG. 4, the opto-isolation communication circuit 4
0 is a photodiode circuit 41 provided on the measurement unit 20 side.
And an optical transmission / reception circuit 40A including a phototransistor circuit 46 and an optical transmission / reception circuit 40B including 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 and the like are interposed as a transmission medium. Therefore, the electrical connection between the voltage signal of the measuring unit 20 and the voltage signal of the main CPU 30 is completely cut off, and thus the human body and the main CP 30 are disconnected.
There is no fear of forming any closed loop with the U30 side, and safe measurement can be performed.

In the main CPU 30, each block to be described later shows various functional blocks realized by the main CPU 30 executing the programs of FIGS. 6 to 8. Here, reference numeral 31 is a thermodilution cardiac output calculation means, which inputs the infusion temperature T _I of the indicator and the thermodiluted blood temperature T _P to calculate the thermodilution cardiac output C _O, and obtains the result. Output. A blood flow velocity calculation means 32 continuously inputs the thermal equilibrium temperature T _C and the blood temperature T _P of the thermistor 10 during heating, calculates the blood flow velocity v, and outputs the result. 33 is a continuous cardiac output calculating means, thermodilution cardiac output C _O which thermodilution cardiac output calculating means 31 of the is determined on the basis of the thermal dilution method
And the blood flow velocity v calculated by the blood flow velocity calculation means 32, the blood vessel cross-sectional area parameter S of the pulmonary artery is calculated and held in a register, and the blood flow velocity calculation means 3 is continuously operated.
2 calculates the continuous cardiac output C _O ′ based on the blood flow velocity v obtained by measurement and the blood vessel cross-sectional area parameter S held in the register, and outputs the result.

In the power supply unit 70, 71 is an alternating current (AC) power supply transformer, which receives an AC input voltage (100 V, 50/6) from the outside.
0 Hz, etc.) is stepped down and converted into a predetermined AC output voltage. The primary winding and the secondary winding of the power transformer 71 are magnetically coupled to each other, thereby cutting off the electrical connection between the main body 1 and the external AC input circuit. Reference numeral 72 denotes a DC power supply circuit, which smoothes and stabilizes a predetermined AC output voltage of the power supply transformer 71 and converts it into a DC voltage.
The DC voltage DCA is supplied to the / DC converter circuit 80, and the DC voltage DCB is supplied to the main CPU 30. DC
The purpose of the / DC converter circuit 80 is to perform the power supply from the power supply unit 70 to the measurement unit 20 in a completely electrically insulated state. For example, as shown in FIG. 5, DC / D
The C converter circuit 80 supplies an inverter circuit 81 that once converts the DCA input supplied from the power supply unit 70 (80B) side into AC power and outputs the AC power, and a stabilized DC DC output on the measurement unit 20 (80A) side. The DC constant voltage circuit 83 and the DC constant voltage circuit 83 are electrically insulated from each other, and as a power transmission means from the inverter circuit 81 to the DC constant voltage circuit 83, a primary winding and a secondary winding are magnetic. A transformer 82 that is only bound to Therefore,
The electrical connection between the DC power supply circuit of the measurement unit 20 and the power supply circuit of the power supply unit 70 is completely cut off, so that there is a concern that any closed loop may be formed between the human body and the main body 1 side or the external AC input circuit. There is no need for safe measurement.

FIG. 2 is a circuit diagram showing details of the blood temperature detecting circuit 22 of the embodiment. The infusion solution temperature detection circuit 21 is substantially the same as the blood temperature detection circuit 22, and therefore its explanation is omitted.

In FIG. 2, the local CPU 26 turns on the relay circuit 228 in advance by the control signal STR1. 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. In addition, the local CPU 26 previously controls the control signal SELS.
To give a selection signal to the relay circuit 228. As a result, the relay circuit 228 outputs the selection signal RLC1 and connects the contacts d and e of the current cutoff circuit 222 to the lower side as shown in the figure.

In this state, the constant voltage circuit 221A applies the constant potential V _H to the thermistor 8. That is, the driver (DR) 221a of the constant voltage circuit 221A drives so that the voltage at the point p becomes approximately V _O by referring to the input reference voltage V _O. Therefore, the potential at the p point is always kept at the constant voltage V _H (approximately V _O ). Further, the constant voltage circuit 221B applies a constant potential V _L to the correction resistor 9. That is, the driver (DR) 221b of the constant voltage circuit 221B refers to the input reference voltage GND, so that the potential at the point q is substantially GND.
Drive to become D. Therefore, the potential at the q point is always kept at the constant potential V _L (approximately GND). In this way, a constant voltage (V _H −V _L ) is always applied to the series circuit of the thermistor 8 and the correction resistor 9 of the catheter 7. When measuring the cardiac output, the thermistor 8 changes its resistance value R _PAT according to the temperature of the thermodiluted blood, and the constant voltage (V _H
-V _L ) is divided by the correction resistance value R _PAS to output the divided voltage (blood temperature signal) V _PAT to the analog switch 225. The blood temperature signal V _PAT is selected by the control signal SELA from the local CPU 26, passes through the analog switch 225, and is input to the (−) terminal of the differential amplifier 226 a of the blood temperature amplification circuit 226. On the other hand, the reference voltage generating circuit 227 is a local CPU.
The constant voltage V _H is selected according to the control signal SELR from the signal 26 and is input to the (+) terminal of the differential amplifier 226a as the reference voltage V _REF . As a result, the differential amplifier 226
The content of the division voltage V _PAT applied between the (+) terminal and the (−) terminal of a is Determined by As is clear from the above formula (1),
If such a divided voltage V _PAT is adopted, the thermistor 8
Since the non-linear resistance value R _{PAT of} is in the denominator and the numerator and the correction resistance value R _PAS corresponding to the resistance value R _PAT specific to the thermistor 8 is in the denominator, the linearity as a probe circuit and the resistance value with respect to a predetermined temperature are Will be corrected. Differential amplifier 226a
Outputs the blood temperature signal V _P by amplifying the divided voltage V _PAT .

Incidentally, when the probe circuit is driven by the constant current I _C , the thermistor 8 and the correction resistor 9 may be connected in parallel for correction. As a result, the content of the counter electromotive voltage V _PAT ′ applied between the (+) terminal and the (−) terminal of the differential amplifier 226a is Determined by Similarly, as is clear from the above equation (1 '), the non-linear resistance value R _PAT of the thermistor 8 is in the denominator and the numerator, and the correction resistance value R _PAS corresponding to the resistance value R _PAT peculiar to the thermistor 8 is present. Since it is in the denominator, the linearity of the probe circuit and the resistance value with respect to a predetermined temperature are corrected.

The characteristics of the thermistors 3 and 8 of the embodiment are, for example, B _25-45.
= 3970K, R (37) = a 40 k.OMEGA, its size is ^{0.50 1 × 0.16 w × 0.15 t} ( unit mm)
Is. The characteristics of the thermistor 10 are, for example, B _25-45.
= 3500K, R (37) = 1000Ω, and the size thereof is 1.18 ¹ × 0.4 ^w × 0.15 ^t .

However, it is not limited to these thermistor characteristics. That is, different types of catheters can be used. Even if there are variations in the non-linear characteristics of the thermistors 3 and 8 and resistance values with respect to a predetermined temperature, or if the standards of the thermistors themselves are different, the correction resistors 4 and 9 provided in advance in the catheters 2 and 7 will Since the resistance temperature characteristic is corrected, the temperature-resistance characteristic seen from the main body 1 side can be treated the same.

Further, the amount of heat generated by the thermistor 10 in the case of the self-heating type is preferably in the range of 0.01 to 50 Joules. If the calorific value is higher than this, the blood temperature may be increased or the blood vessel wall may be damaged, and if the calorific value is lower than this, the detection sensitivity becomes low, and so on.

On the other hand, the leakage current detection circuit 223 detects whether or not the current _ID flowing through the constant voltage loop is leaking. The constant voltage loop includes two current detection resistors R _PS 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 appear at both ends of each resistor R _PS. Electromotive voltage (I _D · R _PS ) and (I _D ′ · R)
_PS ) is differentially amplified. In this case, if no leakage occurs in the constant voltage loop, the source side current I _D and the sink side current I _D
D' is equal. Therefore, the differential amplifiers 223a and 223
The output voltages of b are also equal, and the output signal V _FL of the differential amplifier 233c is approximately 0V. However, if the constant voltage loop leaks through the catheter 7, the state of I _D > I _D ′ (outflow) or I _D <I _D ′ (inflow) occurs, and the differential amplifier 22
The outputs of 3a and 223b are (I _D · R _PS )> (I _D ′)
• _RPS ) or ( _ID * _RPS ) <( _ID '* _RPS ). As a result, the output signal of the differential amplifier 223c is ±
_Vary to V _FL . Therefore, the local CPU 26 can periodically check the degree and state of the leakage current by causing the reference voltage generation circuit 227 to generate an appropriate reference voltage V _FRE . When the local CPU 26 determines the leakage current, it sends the control signal RSR1 to the relay circuit 228. As a result, the relay circuit 228 outputs the control signal RLC2 and immediately opens the contacts a to c of the current cutoff circuit 222. Therefore, the current supply to the probe circuit is immediately cut off. In this way, the adverse effects on the human body are eliminated.

It is also possible to detect the current with a Hall element or the like. Also, when biasing the probe circuit with AC,
The current is detected by the coil wound around the 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 sends the control signal SELP to cause the reference resistance circuit 224 to output the reference temperature signal V _PAT ′ corresponding to the predetermined temperature T ₁ or T ₂ . Each of the divided resistors R _{1 to} R _{4 and the} like in the reference resistance circuit 224 has a predetermined resistance value in advance, and the resistance value hardly changes depending on the temperature. In addition, each series resistor network (R ₁ and R ₂ or R ₃ and R
₄ )) to which the above-mentioned constant potentials V _H and V _L are added, and therefore the temperature drift of the analog circuit network (analog switch 25, blood temperature detection circuit 226, etc.) under the same conditions as the probe circuit of the catheter 7. Etc. can be detected and the actual blood temperature can be corrected. That is, when the temperature T ₁ ′ is detected when the predetermined temperature T ₁ is generated, the error ΔT = (T
For information of ₁ '-T ₁₎ in the main CPU 30, thereby shifting the temperature reference table or the like or corrected and used.

In addition, the local CPU 26 sets the relay circuit 2 before starting the measurement.
A control signal SELS is sent to 28 to connect the contacts d and e of the current interruption circuit 222 to the upper side in FIG. As a result, the power supply path to the thermistor 8 is opened, and instead, the constant potential (V _H −V _L ) is applied to the correction resistor 9 via the reference resistor R _O. In this case, the reference resistance value R _O is the main CPU
Although it is known within 30 and is constant, the correction resistance value R _PAS differs depending on the content of correction to the thermistor 8. Therefore, the local CPU 26 (main CPU 3
0) can examine the characteristics of the thermistor 8 by taking in the divided voltage V _PAT at this time. For example, when the division voltage V _PAT varies within a predetermined range,
It can be determined that the type of the thermistor 8 (type of the catheter 7) is the same. However, when the division voltage V _PAT is extremely different, it can be determined that the thermist 8 belongs to a different category. When the use of such different types of catheters is planned for the main body 1 in advance,
The main CPU 30 shifts or selects the temperature reference table according to the determination result and uses it.

When the divided voltage V _PAT is equal to the reference voltage V _REF (= V _H ), it can be determined that the probe circuit in the catheter 7 is broken or the catheter 7 itself is not connected. Thus, the local CPU 26 (main CPU 3
In 0), the state of each detection circuit is sequentially checked before, during, and after the measurement, and it can be automatically handled.

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 by the control signal STR. As a result, the relay circuit 23
5 outputs the control signal RLC3 to close the contacts f and g of the current cutoff circuit 232. Also, the local CPU
Reference numeral 26 sets the magnitude of the constant current I _C of the constant current circuit 231 by the control signal SELIC. As a result, the constant current circuit 231 supplies the constant current I _C set in the constant current loop including the thermistor 10. This also allows the thermistor 1
0 is heated by a constant current I _C , and its resistance value R _CFT is changed according to the equilibrium temperature between the amount of heat applied to the surrounding blood and the amount of heat deprived by the surrounding blood, and the detected voltage at that balanced temperature _(I C · R _CFT) the equilibrium temperature amplifier circuit 2
34 to the input of a differential amplifier (DAMP) 234a. The differential amplifier 234a differentially amplifies the detection voltage (I _C · R _CFT ) to form the output voltage V _CL at the equilibrium temperature. Resistors R _L , R _M , R provided in the output circuit of the differential amplifier 234a
_H is a dividing resistor that divides the output voltage V _{CL. The} measuring range is made different depending on the size of the thermal equilibrium temperature, such as medium range V _CM or high range V _CH , and the A / D converter is used for each measuring range. It corresponds to a maximum resolution of 25.

Further, the magnitude of the set constant current I _C is determined by the main CPU 30.
Since it is already known, the main CPU 30 can obtain the thermal equilibrium resistance value R _CFT of the thermistor 10 by R _CFT = V _C / I _C.

On the other hand, the leakage current detection circuit 233 uses the constant current I of the constant current loop.
It is detected whether or not _C is leaking. Constant current loop contains two equivalent of the current detection resistor R _CS inserted in series, differential amplifiers 233a and 233b of the leakage current detection circuit 233 counter electromotive voltage appearing across each resistor R _CS (I
_C · R _CS ) and (I _C ′ · R _CS ) are differentially amplified. In this case, if there is no leakage in the constant current loop, the source side current I _C and the sink side current I _C ′ 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 thereof is approximately OV. Therefore, the relay circuit 23
5 remains ON. However, if leakage occurs in the constant current loop through the catheter 7, I _C > I _C ′ (outflow).
Or, the state of I _C <I _C ′ (inflow) occurs, and the differential amplifier 2
The outputs of 33a and 233b are (I _C · R _CS )>
(I _C ′ · R _CS ) or (I _C ′ R _CS ) <(I _C ′ ·
R _CS ). Thus, the output signal ROFF of the comparator 233c is changed to ± _{V R,} immediately OFF the relay circuit 235 when exceeding a predetermined range in both cases. In addition, the relay circuit 235 thereby controls the control signal RLC.
3 is output, the contacts f and g of the current cutoff circuit 232 are immediately opened, and the current supply to the catheter 7 is cut off. In this way, the adverse effects on the human body are eliminated.

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

The thermistor 10 is not limited to the self-heating type thermistor as described above, but a general thermistor may be used.
It may be provided in the vicinity of the heater so that it is heated at a constant current I _C by a separate heater or the like. However, the self-heating type thermistor is advantageous in that it is structurally easier to take in and the structurally stable amount of heat generation and detection can be performed.

Returning to FIG. 1, in the main CPU 30, the thermodilution cardiac output calculating means 31 inputs the infused liquid temperature T _I of the infused liquid temperature detection circuit 21 and the blood temperature T _P of the blood temperature detection circuit 22, and the Stewart is well known. The cardiac output C _O by the thermodilution method is calculated based on the equation (2) by the Hamilton method, and the calculation result is output to the continuous cardiac output calculation means 33.

Here, C _O : cardiac output S _i : specific gravity of infused liquid C _i : specific heat of infused liquid V _i : infused liquid amount T _I : infused liquid temperature T _P : blood temperature S _P : specific gravity of blood C _P : Specific heat of blood Is.

The blood flow velocity calculation means 32 inputs the blood temperature T _P of the blood temperature detection circuit 22 and the equilibrium temperature T _C of the equilibrium temperature detection circuit 23, calculates the blood flow velocity v based on the equation (3), and calculates the calculation result. It outputs to the continuous cardiac output calculation means 33.

Here, K is a proportional constant.

The continuous cardiac output calculation means 32 first calculates the blood vessel cross-sectional area S of the pulmonary artery based on the equation (4) from the cardiac output C _O obtained by the thermodilution method and the blood flow velocity v, and the parameter register Hold at S.

S = C _O / v (4) Since the blood vessel cross-sectional area S of the pulmonary artery is considered to be substantially constant for a reasonable time, once the parameter S is obtained,
Subsequently, continuous cardiac output C _O ′ can be measured.

Therefore, the continuous cardiac output calculating means 32 calculates the continuous cardiac output C _O ′ from the parameter S and the subsequently measured blood flow velocity v based on the equation (5), and the calculation result is displayed on the display 50. Output.

C _O ′ = S · v (5) FIG. 6 is a flowchart of the main routine showing the continuous cardiac output measurement procedure of the embodiment. The processing described below is performed by the cooperation of the local CPU 26 in response to a command from the main CPU 30.

Input to step S1 by turning on the power of 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 or not the catheter is connected. If the catheter is not connected, the process proceeds to step S11 to turn off the relay circuit. Further, in step S12, an error is displayed to that effect, and in step S13, the buzzer 60 is sounded to call the user's attention. Subsequently, in step S14, the idle routine is executed to wait for the abnormality to be removed and the measurement start button to be pressed again. Also, step S3
If the catheter is connected according to the above determination, whether or not the catheter is the standard type is checked by the reference resistance in step S4. If not standard type, step S5
Then, select the corresponding temperature table or the like.

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

If correction is necessary, the process proceeds to step S8 and the temperature table and the like are corrected. If no correction is necessary, the process proceeds to step S9, and it is determined whether or not the initial setting flag of the parameter S is ON.

When it is not ON, this corresponds to the case where the cardiac output of the subject is measured for the first time, the power is turned on to this apparatus, etc., and the routine proceeds to step S20, where the parameter S setting routine is executed. In this parameter setting routine, the cardiac output C _O is calculated and calculated based on the thermodilution method, the blood flow velocity v is subsequently detected, the parameter S is calculated on that, and the result is held in the parameter register S. To do. Further, the initial value setting flag is turned on, and the process returns to step S6. When the process returns to step S9 again, the initial setting flag has been set this time, so the process proceeds to step S10. Step S1
0 is a step of determining the necessity of updating the held parameter S, and this necessity is made by checking an update request flag (not shown). For example, the update request flag is set as follows. Main CP
A timer (not shown) of U30 or the like is set in advance with a time at which it becomes necessary to clinically update the parameter S, 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 proceeds to step S20,
Parameter setting routine (in this case, update routine)
To execute. When the parameter is updated as a result, the update request flag is reset and the timer is restarted in this setting routine. Step S10
If NO is determined in step S4, the parameter S is valid and reliable, so the process proceeds to step S40, and the continuous cardiac output measurement routine is executed.

FIG. 7 is a flow chart 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 the parameter S needs to be updated during the continuous cardiac output measurement. In step S22, the thermistor 10 is cooled sufficiently, and a predetermined time elapses until the thermistor 8 is no longer affected. When this predetermined time has elapsed and the influence of heating disappears, the process proceeds to step S23, and a certain amount of the indicator liquid is injected from the discharge port of the catheter 2. Step S2
At 4, the temperature of the injected liquid T _I is measured. Step S25
Then, the blood temperature T _P thermodiluted up to the pulmonary artery is measured. In step S26, thermodilution cardiac output calculation means 3
The cardiac output C _O is calculated by the equation (2) according to 1, and the calculated cardiac output C _O is output to the continuous cardiac output calculating means 33 in step S27. Although not shown, the continuous cardiac output calculating means 33 displays the cardiac output value C _O if necessary. Thus, the cardiac output C _O is measured for the first time or by the thermodilution method for updating the parameters.

Subsequently, in step S28, the thermistor 10 is heated with a constant current I _C. In step S29, the blood temperature T _P before being heated is measured. At step S30 detects the equilibrium temperature _{T C} of the thermistor 10 itself during heating. Further, at this time, the potential difference V _C across the thermistor 10 used in the equation (3) is simultaneously obtained. In step S31, the blood flow velocity calculation means 32 calculates the blood flow velocity v by the equation (3) and outputs it to the continuous cardiac output calculation means 33. In step S32, the continuous cardiac output calculation means 33 obtains the blood vessel cross-sectional area parameter S according to the equation (4) and holds it in the register S.

FIG. 8 is a flow chart showing details of the continuous cardiac output measurement routine of the embodiment. In step S41, the thermistor 10 is heated with a constant current I _C. In step S42, the blood temperature T _P is measured. In step S43, the equilibrium temperature T _C of the thermistor 10 itself being heated is measured. At that time, the potential difference V _C across the thermistor 10 is obtained at the same time.
In step S44, the blood flow velocity calculation means 32 calculates the blood flow velocity v by the equation (3), and the continuous cardiac output calculation means 3 is calculated.
Output to 3. 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 C _O ′. In step S46, the obtained continuous cardiac output C _O ′ is displayed.

In addition, although the above-mentioned embodiment described the cardiac output measuring device, the present invention is not limited to this. The present invention also provides an electronic thermometer,
It can be applied to various measuring devices such as a blood pressure monitor, an electrocardiograph, a heart rate monitor, and an electroencephalograph.

Further, although the above-mentioned embodiment describes the temperature sensor probe circuit using the temperature sensitive element (thermistor), the present invention is not limited to this. In addition, the present invention can be applied to a probe circuit 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 has been described, but the present invention is not limited to this. Alternatively, an AC bias or a pulse signal may be added. The leakage current of the AC bias may be compared with the actual value. The leakage current of the pulse signal may be compared in a predetermined section.

EFFECTS OF THE INVENTION According to the present invention, a detection unit that detects a state of a living body and an information processing unit that performs signal processing based on a signal from the detection unit are non-electrically connected including each power supply. This prevents electrical closed loops from being formed, and cuts off the power supply to the detection unit when leak current is detected in the detection unit, improving the insulation of the detection unit and preventing leakage from the detection unit to the living body. There is an effect that it is possible to prevent and improve safety.

[Brief description of drawings]

FIG. 1 is a block diagram of a continuous cardiac output measuring apparatus according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing details of a blood temperature detecting circuit 22 of the embodiment, and FIG. 3 is an equilibrium temperature of the embodiment. FIG. 4 is a circuit diagram showing details of the detection circuit 23, FIG. 4 is a circuit diagram showing an opto-iculation communication circuit of the embodiment, FIG. 5 is a circuit diagram showing a DC / DC converter circuit of the embodiment, and FIG. FIG. 7 is a flowchart of a main routine showing a continuous cardiac output measurement procedure of FIG. 7, FIG. 7 is a flowchart showing details of a parameter S setting processing routine of the embodiment, and FIG. 8 is a detail of a continuous cardiac output measurement routine of the embodiment. It is a flowchart showing. In the figure, 1 ... Main body, 2, 7 ... Catheter, 3, 8, 10 ...
Thermistors, 4, 9 ... Correction resistors, 5, 6, 11, 12 ...
Connector, 20 ... Measuring unit, 21 ... Injection liquid temperature detection circuit,
22 ... Blood temperature detection circuit, 23 ... Equilibrium temperature detection circuit, 2
4 ... Analog switch, 25 ... A / D converter, 26 ... Local CPU, 30 ... Main CPU, 31 ... Thermodilution cardiac output calculation means, 32 ... Blood flow velocity calculation means, 33 ... Continuous cardiac output calculation Means, 40 ... Opto-isolation communication circuit, 50 ... Indicator, 60 ... Buzzer, 70 ... Power supply section, 71
… Power transformer, 72… DC power circuit, 80… DC / D
It is a C converter circuit.

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Claims (1)

[Claims] 1. A detection means for contacting a living body to detect its state and outputting an analog signal corresponding to the state, and an energization electrically connected to the detection means for supplying a predetermined current to the detection means. Means, A / D conversion means connected to the detection means and converting the analog signal into a corresponding digital signal, and analog information about the living body based on the digital signal output by the A / D conversion means Information processing means, coupling means provided for respectively non-electrically coupling the A / D conversion means and the information processing means, and first power supply means for supplying electric power to the information processing means. Is supplied with electric power from the first power supply means,
Input from the power supply means and its output are magnetically coupled, and second power supply means for supplying electric power to the A / D conversion means and the energizing means, and the energizing means A difference current detecting means for detecting a difference between a current value supplied to the detecting means and a current value fed back to the supplying means through the detecting means; and a current difference detected by the difference current detecting means is out of a predetermined range. In the case of, the power supply cutoff means for cutting off the power supply from the energization means to the detection means, and the biological information processing apparatus.