JPH04357961A - Blood leakage detector - Google Patents

Abstract

PURPOSE:To attain correct blood leakage detection with a high sensitivity by computing and comparing the magnitude of the DC voltage levels obtd. by converting transmission quantities of light of two wavelengths synchronized with light emission pulse voltage signals via an A/D converter and a microcomputer. CONSTITUTION:A light emission side circuit connects direct DC driving circuits 16, 18 via resistors R1, R2 to a light emitting element 10 and drives these driving circuits with an oscillation circuit 12 which outputs prescribed pulse voltage signals. A light receiving side circuit obtains the output of a light receiving element 20 respectively as the DC voltages obtd. by converting the transmission quantities of the light of the above-mentioned two wavelengths synchronized with the light emission pulse voltage signals via a direct DC voltage conversion circuit 22 and detects a blood leakage state by computing and comparing the magnitude of these DC voltage levels via the A/D conversion circuit 36 and the microcomputer 38. The correction computing to decrease the difference between the voltage levels obtd. by converting the transmission quantities of the light of the two wavelengths on the light receiving side to zero in the state of having no stains is allowed, by which the erroneous detection by bubbles, etc., is prevented.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention detects blood leakage in an artificial dialysis machine without causing erroneous detection due to air bubbles, dirt, offset voltage of the electric circuit, etc., and performs initial inspection of the artificial dialysis machine. The present invention relates to a blood leak detector that can be automatically implemented.

0002

[Prior Art] Generally, an artificial dialysis machine takes blood from the venous side of the human body, introduces it into a dialyzer using a semipermeable membrane, and contacts it with a dialysate through the semipermeable membrane in the dialyzer. It is known as a dialysis treatment device that is configured to remove waste products from blood and then return them to the human body.

However, when performing extracorporeal circulation of blood using this type of artificial dialysis device, for example, if there is a pinhole or the like in the semipermeable membrane, blood leakage may occur on the dialysate side, which may result in long-term dialysis treatment. This results in considerable blood loss and is extremely dangerous to the human body.

[0004] From this point of view, various blood leakage detection devices have been proposed for this type of artificial dialysis apparatus, which detect the contamination of blood into the dialysate and generate an alarm. Therefore, as a conventional blood leakage detection device, it is preferable to use photoelectric photometry to detect the mixed state of blood dispersed in the dialysate, and the following two types of methods are known: It is being

That is, in the first method, a light-emitting element having one peak wavelength range is provided on the light-emitting side, and a decrease in the amount of light transmitted through the sample (dialysate) is detected by a light-receiving element on the light-receiving side. This is a method of detecting blood leakage. However, in this first method, the amount of light transmitted decreases not only when blood gets mixed into the dialysate, but also when air bubbles get mixed in and stains such as proteins, etc.
There is a high possibility of erroneously detecting something other than blood leakage, and there is a drawback that it lacks reliability.

On the other hand, in the second method, a light-emitting element having two peak wavelengths with different absorption rates for blood is provided on the light-emitting side, and the light passes through the subject (dialysis fluid) and reaches the light-receiving element on the light-receiving side. If the decrease in the amount of light transmitted at the two wavelengths is caused by air bubbles or dirt as described above, the decrease is the same in both cases, but in the case of blood leakage, the wavelengths that are easily affected by blood decrease markedly. This is a method that can reliably detect blood leakage.

[0007]

[Problems to be Solved by the Invention] However, according to the second method described above, blood leakage is detected based on the difference in the amount of light transmitted at two wavelengths, so in order to improve the detection accuracy, It is necessary to adjust the operating circuits on the light emitting side and the light receiving side so that the differential output of the voltage level obtained by converting the amount of light transmission in a state where there is no blood leakage, bubbles, or dirt is zero. For this reason, there is a drawback that the design and manufacture of a circuit for performing photoelectric photometry is complicated.

Furthermore, both the first method and the second method in the conventional blood leakage detection device have the disadvantage that they are affected by the offset voltage of the electric circuit which varies depending on the temperature, resulting in erroneous detection or malfunction.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to prevent false detections that are affected by the occurrence of bubbles and dirt in the dialysate, the offset voltage of the electrical circuit, etc., and to simplify and adjust the circuit for photoelectric photometry. This makes it possible to always achieve high-sensitivity and appropriate blood leakage detection without unnecessary configurations, and to safely and automatically carry out initial inspections before starting dialysis treatment using an artificial dialysis machine.It is also possible to manufacture at a low cost. An object of the present invention is to provide a blood leakage detector that can be used to detect blood leakage.

0010

[Means for Solving the Problems] A blood leak detector according to the present invention causes a light emitting element to separately emit light with two peak wavelengths having different absorption rates for blood, and transmits dialysate to a light receiving element. In a blood leakage detector that detects the state of blood leakage in a dialysate by receiving light and converting the voltage level obtained by converting the amount of light transmitted at two wavelengths to the dialysate, a light emitting element is connected to a light emitting element through a resistor. A light-emitting side circuit is configured to connect a drive circuit directly to the drive circuit and drive this drive circuit with an oscillation circuit that outputs a predetermined pulse voltage signal, and the output of the light receiving element is directly connected to the light-emission pulse voltage through a current-voltage conversion circuit. The transmitted amount of light of the two wavelengths synchronized with the signal is obtained as a converted DC voltage, and the magnitude of these DC voltage levels is calculated and compared via an A/D converter and a microcomputer to detect blood leakage. A light receiving side circuit configured to detect a state is provided.

[0011] In the blood leakage detector, an AND circuit is provided in the light-emitting side circuit between a drive circuit that causes the light-emitting element to emit light having two wavelengths and an oscillation circuit that outputs a predetermined pulse voltage signal. , can be configured to simultaneously stop emitting light having two wavelengths. In this case, the dialysate should be 2
Stop the emission of light with two wavelengths at the same time, calculate the offset voltage of the light-receiving circuit at this time, then emit light with two wavelengths separately, and calculate the output voltage of the light-receiving circuit at this time. After calculating a correction value from these offset voltages and output voltages, the emission of light having two wavelengths is periodically stopped at the same time, and the offset voltage is adjusted based on the offset voltage at that time and the correction value. Preferably, the microcomputer is configured to calculate a corrected output voltage value that is not affected. Furthermore, in a light-emitting side circuit in which a drive circuit is directly connected to a light-emitting element via a resistor, an auxiliary resistor is further connected and arranged between the connection point of the resistor and the drive circuit, and this auxiliary resistor and The contacts of the automatic switch are connected in parallel, and the resistance value of the auxiliary resistor is determined by the ratio of the voltage levels on the receiving side of the two wavelengths of light when the contact of the automatic switch is open when there is a predetermined blood leakage. It is also possible to have a configuration in which the ratio is set to a value equivalent to the time.

0012

[Operation] According to the blood leakage detector according to the present invention, the light-emitting side circuit is an oscillation circuit that connects a drive circuit directly to the light-emitting element via a resistor, and outputs a predetermined pulse voltage signal from this drive circuit. The light-receiving side circuit directly converts the output of the light-receiving element into a DC voltage obtained by converting the transmitted amount of light of the two wavelengths in synchronization with the light emission pulse voltage signal via a current-voltage conversion circuit. By calculating and comparing the magnitudes of these DC voltage levels through an A/D converter and a microcomputer to detect a blood leakage state, the light emission intensity of the light emitting element can be corrected. There is no need to adjust the amplification factor of the light-receiving signal of the light-receiving element, and therefore, it is possible to omit the use of electrical components for these adjustments, thereby obtaining a blood leakage detector with a simple configuration and high sensitivity.

In particular, according to the blood leakage detector of the present invention, the difference between the voltage levels obtained by converting the amount of transmitted light of two wavelengths on the receiving side is corrected to zero in a state where there is no blood leakage, bubbles, or dirt. By making calculation possible, false detection due to air bubbles or dirt other than blood leakage can be reliably prevented, and appropriate blood leakage monitoring can be achieved.

Furthermore, in the blood leakage detector of the present invention, in the light emitting side circuit, the light emitting element is configured to stop emitting light having two wavelengths at the same time. By determining the voltage value, it is possible to prevent erroneous detection operations that are affected by offset voltages of electric circuits that vary depending on temperature, and to constantly and accurately monitor blood leakage.

Furthermore, in the blood leakage detector of the present invention, an auxiliary resistor connected in parallel with the contacts of the automatic switch is connected to the light emitting side circuit, and the resistance value of the auxiliary resistor is set to the contact of the automatic switch. By setting the ratio of the voltage levels on the receiving side of the two wavelengths of light when it is open to a value that is equivalent to the ratio when a predetermined blood leak occurs, it is possible to This makes it possible to automatically carry out a start-up inspection.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of a blood leakage detector according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block circuit diagram showing an embodiment of a blood leakage detector according to the present invention, and FIG. 2 is a waveform diagram showing the operating state of the block circuit of FIG. 1 and 2, reference numeral 10 is a light emitting element, 12 is a constant pulse voltage V
14 is an inversion circuit that generates an inverted output pulse voltage V2 of the output pulse voltage V1 of the oscillation circuit, and 16 and 18 are inverter circuits that generate two peak wavelengths with different blood absorption rates for the light emitting element 10, respectively. Each of the drive circuits for outputting light is shown. However, on the light emitting side, the pulse voltage V1 of the oscillation circuit 12 is
On the one hand, it is supplied to the light emitting element 10 via an inversion circuit 14, a drive circuit 18 and a resistor R1, and on the other hand, it is directly supplied to the light emitting element 10 via a drive circuit 16 and a resistor R2.
Configure the circuit to supply

Further, reference numeral 20 is a light receiving element, 22 is a current-voltage conversion circuit, 24 and 26 are amplifier circuits, and 28 and 30 are drive circuits for driving the light emitting element 10 based on the pulse voltages V1 and V2 that drive the light emitting element 10. A synchronization circuit that synchronizes the pulse with the output pulse of the light receiving element 20 (see V4, V5), 32 and 34 are rectifier circuits, 36 is an A/D conversion circuit, 38
indicate microcomputers, respectively. However, on the light-receiving side, the output of the light-receiving element 20 is directly converted to voltage V3 by the current-voltage conversion circuit 22 without being amplified, and then the voltage levels obtained by converting the amounts of transmission of the two wavelengths are compared. On the one hand, it is transferred to the A/D conversion circuit 36 via the amplifier circuit 24, synchronization circuit 28, and rectification circuit 32, and on the other hand, it is transferred to the A/D conversion circuit 36 via the amplifier circuit 26, synchronization circuit 30, and rectification circuit 34, This A/
The circuit is configured to monitor blood leakage by inputting the signal A/D converted by the D conversion circuit 36 to the microcomputer 38, calculating and comparing the voltages of the two wavelengths.

The blood leakage detector of this embodiment configured as described above uses, on the light emitting side, two peak wavelengths of light having different absorption rates for blood, for example, 550nm and 650nm.
A light emitting device 10 having a peak wavelength of m is used. Therefore, the light receiving element 20 on the receiving side transmits through the subject (dialysate).
When the rate of decrease in the amount of light transmitted at the two wavelengths reached is the same due to air bubbles or dirt, the rate of decrease in the amount of light transmitted at the two wavelengths reached is the same in both cases, but in the case of blood leakage, the wavelength that is easily affected by blood (550 nm) decreases markedly. . Therefore, in this case, it is necessary to set the difference between the voltage levels obtained by converting the amount of transmitted light of the two wavelengths on the light receiving side to 0 in a state where there is no blood leakage, bubbles, or dirt. Therefore, in this embodiment, the DC output V6 on the light receiving side is obtained without adjusting the light emission intensity of the light emitting element 10 or adjusting the amplification factor of the light receiving element 20. , V7 are input to the microcomputer 38 via the A/D conversion circuit 36, and a correction value a is calculated to reduce the difference to 0 by calculating and comparing the voltages of the two wavelengths.
is obtained using the following equation (1). V6 - aV7 = 0 (1)
By constantly correcting the voltage of one wavelength using the correction value a and comparing this with the voltage of the other wavelength, appropriate blood leakage monitoring can be achieved.

FIG. 3 is a block circuit diagram showing another embodiment of the blood leakage detector according to the present invention, and FIG. 4 is a waveform diagram showing the operating state of the block circuit of FIG. In the circuit of this embodiment, the same reference numerals are given to the same components as those of the circuit shown in FIG. 1, and detailed explanation thereof will be omitted.

In this embodiment, in the embodiment circuit shown in FIG. and place these AND
An oscillation circuit 12 is connected to one input terminal of each of the circuits 40 and 42.
The circuit is configured such that the microcomputer 38 supplies a signal V8 that causes the light emitting element 10 to stop emitting light regardless of the oscillation operation of the light emitting element 10. The other circuit configurations are the same as the embodiment shown in FIG. 1 above.

The blood leakage detector of this embodiment configured as described above reduces the offset voltage generated in the circuit on the light receiving side by simultaneously stopping light emission of two wavelengths using the light emission stop signal V8 on the light emitting side. can be obtained automatically. That is, in this case, the microcomputer 38 calculates the offset voltage as follows.

First, in a state where there is no blood leakage, bubbles, or dirt in the subject (dialysate), the light emitting element 10 stops emitting light at two wavelengths at the same time, and the offset voltages V6' and V7' at this time are It is calculated using the following equations (2) and (3). V6'=V6 (
2) V7'=V7
(3) Next, in the same state as above, the light emitting element 10 is caused to emit light at two wavelengths separately, and the output voltages V6 and V at this time are
7 and the offset voltages V6' and V7', a correction value a' is determined by the following equation (4). V6 −V6′=a′(V7 −V7′)
(4) Thereafter, the light emission of the two wavelengths in the light emitting element 10 is periodically stopped at the same time, and the offset voltages V6'' and V7'' at that time are calculated using the following equations (5) and (6) in the same manner as above.
This is calculated using the following equations (7) and (8) along with the correction value a'.
), it is possible to obtain corrected voltage values Vx, Vy that are not affected by the offset voltage. V6″=V6
(5) V7″=V7
(6) Vx = V6 −V
6″ (7)Vy=a
′(V7 −V7″) (8) Therefore, by comparing the corrected voltage values Vx and Vy, it is possible to prevent false detection operations that are affected by the offset voltage of the electric circuit that varies depending on the temperature, and to always Blood leakage can be accurately monitored.Therefore, according to the electric circuit of this embodiment, there is no need to provide a thermistor or the like for temperature correction.

FIG. 5 is a block circuit diagram showing still another embodiment of the blood leak detector according to the present invention. In the circuit of this embodiment, the same reference numerals are given to the same components as those of the circuit shown in FIG. 1, and detailed explanation thereof will be omitted.

In this embodiment, in the embodiment circuit shown in FIGS. 1 and 3, a resistor R3 is further connected between the connection point between the light emitting side drive circuit 18 and the resistor R1, and this resistor R3 For example, a contact 52 of an automatic switch 50 such as a relay is connected in parallel with this. In this case, the resistance value of the resistor R3 is equal to the resistance value of the contact 52 of the automatic switch 50.
The ratio of the voltage levels on the light receiving side of the two wavelengths of light when the light is open is set to a value that is equivalent to the difference when a predetermined blood leak occurs. The automatic switch 50 is configured to open and close in response to a signal from the microcomputer 38.

In the blood leakage detector of this embodiment configured as described above, the contact 52 of the automatic switch 50 is closed when blood leakage is being monitored on the light receiving side, and closed when checking the sensitivity of the detector. By setting the microcomputer 38 in advance to issue a command to open the blood leakage detector, a start-up inspection of the artificial dialysis machine before the start of dialysis treatment or an operation check of the blood leakage detector during dialysis can be automatically performed. be able to.

FIG. 6 is a block circuit diagram showing yet another embodiment of the blood leakage detector according to the present invention. The circuit of this embodiment has a decimal Johnson counter 60 in place of the inversion circuit 14 in the circuits shown in FIGS. Inverting circuits 70 and 72 are connected to the signal line to be supplied, and further rectifying circuits 32 and
Amplifier circuits 80 and 82 are connected to the output sides of 34, respectively. Other configurations are shown in FIGS. 5 and 3 above.
The circuit shown in FIG. 1 is the same as that shown in FIG.

According to the blood leakage detector of this embodiment configured as described above, as is clear from FIG. Since there is a pause in the emission of wavelengths, it is possible to prevent mutual interference that occurs when a light emitting element and a light receiving element with slow response speeds are used. Therefore, FIG. 5 and FIG.
The blood leakage detection operation by the embodiment circuit shown in FIG. 1 can be made even more accurate and reliable. In the circuit of this embodiment, if sufficient outputs from the rectifier circuits 32 and 34 can be obtained, the amplifier circuits 80 and 82 can be omitted.

Although preferred embodiments of the detector of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the spirit of the present invention. Of course.

[0030]

As is clear from the embodiments described above, according to the present invention, the light-emitting side circuit connects a drive circuit directly to the light-emitting element through a resistor, and applies a predetermined pulse voltage to the drive circuit. The circuit is configured to be driven by an oscillation circuit that outputs a signal, and the light-receiving side circuit converts the output of the light-receiving element directly through a current-voltage conversion circuit to convert the transmitted amount of light of the two wavelengths in synchronization with the light emission pulse voltage signal. By configuring the system to detect blood leakage by obtaining converted DC voltages and calculating and comparing the magnitudes of these DC voltage levels through an A/D converter and a microcomputer, the light emitting element can be detected. There is no need to correct the emission intensity or adjust the amplification factor of the light-receiving signal of the light-receiving element, and therefore omit the use of electrical parts for these adjustments to obtain a blood leakage detector with a simple configuration and high sensitivity. be able to.

In particular, according to the blood leakage detector of the present invention, the voltage level obtained by converting the amount of transmitted light of two wavelengths on the receiving side is detected using a microcomputer without blood leakage, bubbles, or dirt. By performing a correction calculation to reduce the difference to 0, it is possible to reliably prevent false detection due to air bubbles or dirt other than blood leakage, and to achieve appropriate blood leakage monitoring.

In addition, in the blood leakage detector of the present invention, the light emitting element in the light emitting side circuit is configured to simultaneously stop emitting light having two wavelengths. By determining the voltage value, it is possible to prevent erroneous detection operations that are affected by offset voltages of electric circuits that vary depending on temperature, and to constantly and accurately monitor blood leakage. Therefore, in this case,
There is no need to provide a thermistor or the like for temperature correction in the electric circuit.

Furthermore, in the blood leakage detector of the present invention, an auxiliary resistor connected in parallel with the contacts of the automatic switch is connected to the light emitting side circuit, and the resistance value of the auxiliary resistor is set to the contact of the automatic switch. By setting the ratio of the voltage levels on the receiving side of the two wavelengths of light when it is open to a value that is equivalent to the ratio when a predetermined blood leak occurs, it is possible to The start-of-work inspection can be carried out automatically.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of a blood leakage detector according to the present invention.

FIG. 2 is a waveform diagram showing the operating state of the blood leakage detector shown in FIG. 1;

FIG. 3 is a block circuit diagram showing another embodiment of a blood leakage detector according to the present invention.

FIG. 4 is a waveform diagram showing the operating state of the blood leakage detector shown in FIG. 3;

FIG. 5 is a main circuit diagram showing still another embodiment of the blood leakage detector according to the present invention.

FIG. 6 is a block circuit diagram showing still another embodiment of the blood leakage detector according to the present invention.

7 is a waveform diagram showing the operating state of the blood leak detector shown in FIG. 6. FIG.

[Explanation of symbols]

10 Light emitting element
12 Oscillation circuit 14 Inversion circuit
16, 18 Drive circuit 20 Light receiving circuit
22 Current-voltage conversion circuit 24, 26 Amplification circuit
28, 30 Synchronous circuit 32, 34 Rectifier circuit
36 A/D conversion circuit 38 microcomputer 40,
42 AND circuit 50 Automatic switch
52 Contact 60 Decimal Johnson counter
70, 72 Inverting circuit 80, 82 Amplifying circuit

Claims (4)

[Claims] 1. Light having two peak wavelengths having different absorption rates for blood is caused to emit light from a light emitting element separately, and the light is transmitted through a dialysate and received by a light receiving element, whereby the light of the two wavelengths is transmitted through the dialysate. In a blood leakage detector that detects the state of blood leakage in dialysate by comparing the voltage levels obtained by converting the amounts, a drive circuit is connected directly to the light emitting element via a resistor, and this drive circuit is set to a predetermined value. A light emitting side circuit configured to be driven by an oscillation circuit that outputs a pulse voltage signal, and an output of a light receiving element are directly passed through a current-voltage conversion circuit to calculate the amount of light transmitted at the two wavelengths in synchronization with the light emitting pulse voltage signal. A light-receiving side circuit configured to detect a blood leakage state by obtaining each converted DC voltage and calculating and comparing the magnitude of these DC voltage levels via an A/D converter and a microcomputer is provided. A blood leakage detector characterized by: 2. In the light emitting side circuit, an AND circuit is provided between a drive circuit that causes the light emitting element to emit light having two wavelengths and an oscillation circuit that outputs a predetermined pulse voltage signal, so that the light emitting element has two wavelengths. The blood leakage detector according to claim 1, wherein the blood leakage detector is configured so that emission of light can be stopped at the same time. 3. Stop the emission of light having two wavelengths simultaneously in a state where there is no blood leakage, bubbles, or dirt in the dialysate, calculate the offset voltage of the light receiving side circuit at this time, and then calculate the offset voltage of the light receiving circuit at this time. After separately emitting light having two wavelengths, calculating the output voltage of the light-receiving circuit at this time, and calculating a correction value from these offset voltages and output voltage, periodically emitting light having two wavelengths. 3. The blood leakage detector according to claim 2, wherein the microcomputer is configured to stop at the same time and calculate a corrected output voltage value unaffected by the offset voltage based on the offset voltage at that time and the correction value. 4. In a light-emitting side circuit in which a drive circuit is directly connected to a light-emitting element via a resistor, an auxiliary resistor is further connected and arranged between the connection point of the resistor and the drive circuit, and the auxiliary resistor is connected directly to the light-emitting element through a resistor. A contact of an automatic switch is connected in parallel with the resistor, and the resistance value of the auxiliary resistor is determined so that the ratio of the voltage levels on the receiving side of light of two wavelengths when the contact of the automatic switch is open is a predetermined blood leakage. 3. The blood leakage detector according to claim 1 or 2, wherein the blood leakage detector is set to a value such that the ratio is the same as that when there was.