JPS6226415B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blood leakage detection device suitable for detecting trace amounts of blood or hemoglobins, particularly for detecting blood leakage from a blood processing device such as an artificial kidney.

In the case of artificial kidneys, the number of users of which has increased rapidly in recent years, blood may leak into the dialysate due to failure of the dialysis membrane or other factors, and if this were to go unaddressed, it could lead to a serious accident involving human life. Therefore, it is necessary to accurately distinguish between blood leakage and noise such as air bubbles to prevent blood leakage, and to take appropriate measures immediately upon learning of the blood leakage.
In response to this, various types of blood leak detection devices have conventionally existed. Conventional devices of this kind combine an incandescent light bulb that projects light onto a detection cell that guides the sample liquid, and a phototube that receives the white light that has passed through the detection cell through a filter and converts it into an electrical signal. , most of them are configured to measure using the zero position method.

Incidentally, in an artificial kidney, it is necessary to detect low concentration blood diluted with a large amount of dialysate, and the detection operation must be performed stably over a long period of time.

However, the conventional method described above detects blood leakage using the zero-level method, that is, by comparing it with a reference light amount.
It is easily affected by foreign substances that are components other than blood, such as waste products and air bubbles in the blood that have moved to the dialysate side, and especially when used for a long time, waste products may adhere to the surface of the detection cell, causing measurement errors. will occur. To prevent this, it is necessary to detect blood leakage while cleaning the container at regular intervals.

Furthermore, the light projected from an incandescent light bulb has a continuous wavelength distribution and contains many unnecessary wavelength components, so not only is the energy efficiency poor, but also the wavelength of the light bulb's wavelength distribution, which is close to 565 nm, which is the absorption spectrum of blood. A special filter must be used in order to select the filter, which results in a complicated configuration and high cost. In addition, the above incandescent bulb has a service life of approximately
It has a relatively short lifespan of 1000 hours, and in order to deal with bulb burnouts, it is necessary to install a separate bulb burnout detection circuit.

This invention was made in view of the above circumstances,
A light emitting element with a peak wavelength characteristic within a range that includes the absorption spectrum of blood is used as a light source, and blood leakage is detected based on the deviation method while adjusting the output from this light emitting element to zero at regular intervals. It is an object of the present invention to provide a blood leakage detection device that has a simple configuration that improves detection sensitivity and can stably maintain detection operation over a long period of time.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 11 is a detection cell that guides a test liquid such as dialysate, 12 is a light emitting element that projects light onto the detection cell 11, and 13 is a light emitting element that projects light from the light emitting element 12 through the detection cell 11. This is a light receiving element that receives light, and both elements 12 and 13 are used in close contact with the glass surface of the detection cell 11. As the light-emitting element 11, for example, a green light-emitting diode is used, and the peak value of the spectrum is within a range including the blood absorption spectrum of 565 nm, for example, 520 nm to 520 nm.
In this example, it is within 600 nm.
Those existing at 570nm are selected and set. As the light receiving element 13, a photoconductive element such as CDS is used. 14 is the light emitting and light receiving element 1
A temperature correction circuit for 2 and 13 has a heat-sensitive element (not shown) such as a thermistor, and detects the temperature of both elements 12 and 13 that is equal to the temperature of the dialysis and drainage liquid with this heat-sensitive element, This temperature is compared with the temperature characteristics of both elements 12 and 13, and a signal for temperature correction is output. Reference numeral 15 denotes a light emitting drive circuit, which adjusts the power supplied to the light emitting element 12 based on a signal from the temperature correction circuit 14.

Reference numeral 16 denotes an automatic zero adjustment circuit for receiving the output signal a from the light receiving element 13 and correcting an error in the output signal a caused by a change in the amount of light. A differential amplifier 17 amplifies the difference between an output signal a and a reference signal b (described later), and an output signal c from the differential amplifier circuit 17 is converted into a concentration signal d corresponding to the scale of an indicator 18.
The reference signal generating circuit 42 includes a concentration signal generating circuit 41 consisting of a span adjustment circuit 19 that converts the converted signal into a span adjusting circuit 19, and a reference signal generating circuit 42 consisting of a timer circuit 20, a gate circuit 21, and a memory circuit 22. The gate circuit 21 performs the above-mentioned span adjustment when the signal T from the timer circuit 20 sent at regular intervals and the start signal S or reset signal R synchronized with the start of the blood pump sent from the blood pump synchronization circuit 23 are applied. The output signal d from the circuit 19 is amplified and sent to the memory circuit 22. The memory circuit 22 also holds the signal e from the gate circuit 21, and as shown in FIG. 26
The voltage of the capacitor 25 is amplified by the operational amplifier 26, and the output signal b is sent to the differential amplifier 17 as the reference signal b.

27 is a blood leakage detection circuit, and this detection circuit 27 is
For example, first and second density determination circuits 28 and 29 to which the density signal d is input, and a display circuit 3 provided corresponding to these density determination circuits 28 and 29.
0, 31 and an alarm circuit 32. Both concentration determination circuits 28 and 29 are comprised of, for example, voltage comparison circuits. First concentration determination circuit 28
The voltage corresponding to the concentration of 100 ppm is set to 1V, and when the concentration signal d is 1V or more, a positive voltage is generated to activate the display circuit 30 and the alarm circuit 32. The second concentration determination circuit 29
The voltage corresponding to the concentration of 200 ppm is set to 2V, and when the concentration signal d reaches 2V, the display circuit 31
At the same time, a drive stop circuit 33 for the dialysis machine (not shown) is operated. By the way, according to the proposed standards for artificial kidney devices for dialysis, blood with a hematocrit value of 20% has a concentration of 500 ppm.
It goes without saying that the set voltages of the first and second concentration determination circuits 28 and 29 can be changed to arbitrary values within a range that satisfies this requirement. Each of the above display circuits 30, 3
The alarm circuit 1 is composed of a CR integrating circuit, a switching circuit, a light emitting element, etc. (not shown), and the alarm circuit 32 is composed of a flip-flop circuit (not shown), a drive circuit for a sounding device such as a buzzer, etc.

Next, the operation of the above configuration will be explained.

The light from the light emitting element 12 is projected onto the detection cell 11 and passes through the detection cell 11, so the change in the amount of light as it passes through is received by the light receiving element 13, and its output signal a is applied to the automatic zero adjustment circuit 16. be done. In the automatic zero adjustment circuit 16, a differential amplifier 17 compares the above output signal a with a reference signal b, which will be described later, and the output signal c is converted into a density signal d by a span adjustment circuit 19. d is indicated by the indicator 18.

Assume now that the density signal d is deviated to the positive side. At this time, the start signal S from the pump synchronization circuit 23 causes the gate circuit 21 to operate at a timing synchronized with the start of the blood pump, and the concentration signal d is amplified to become the signal e, and the memory circuit 2
2 is input. As a result, the capacitor 25 of the memory circuit 22 is charged and its terminal voltage rises, so that the reference signal b sent from the memory circuit 22 also rises. Since the differential amplifier 17 operates to lower its output signal c when the reference signal b rises, the concentration signal d also falls below its original voltage value. On the other hand, when the concentration signal d is shifted to the negative side, the concentration signal d rises above the original voltage value by an operation opposite to that described above. If the degree of signal amplification in the closed loop is sufficiently high, the concentration signal d will be converged to 0V. Here, the degree of amplification of the span adjustment circuit 19 is generally set to be smaller than that of the amplifier built in the gate circuit 21, but such a setting does not apply to each of the circuits 17, 19, This increases the overall gain of the closed loop formed by 21 and 22, and helps to more precisely converge the concentration signal d to 0V. Furthermore, even if the degree of increase in span adjustment circuit 19 is changed during span adjustment, it goes without saying that this will not cause any problem during automatic zero adjustment.

Next, after the concentration signal d has converged to 0V, when the operation of the gate circuit 21 is finished and the input to the memory circuit 22 is stopped, the terminal voltage of the capacitor 25 of the memory circuit 22 is This voltage satisfies the necessary and sufficient conditions for setting the concentration signal d to 0V. Here, if the internal resistance of the capacitor 25 is very high and the input impedance of the operational amplifier 26 is sufficiently high, then the capacitor 25
5 is not discharged, and the terminal voltage is maintained as it is. Therefore, even if the gate circuit 21 stops operating, the reference signal b to the differential amplifier 17 remains constant until the gate circuit 21 opens next time. That is, when the gate circuit 21 operates, the concentration signal d becomes 0V, and when the operation of the gate circuit 21 ends, the reference signal b maintains its current value. During that time, if a slight change occurs in the output signal a from the light receiving element 13, the concentration signal d also deviates from 0V. For example, if the deviation is about 1V, the first concentration discrimination circuit 2
8 determines this as a trace amount of blood leakage of about 100 ppm, and only the display circuit 30 and alarm circuit 32 are activated. When the deviation of the above concentration signal d exceeds 2V,
The second concentration determination circuit 29 determines this as a blood leak with a concentration exceeding 200 ppm, and as a result, a stop signal Q is sent from the drive stop circuit 33, and the operation of the dialysis device (blood processing device) is stopped. By the way, if the gate circuit 21 is activated again in the timer circuit 20, the concentration signal d is readjusted to 0V. That is, the gate circuit 21 is the timer circuit 20
The above zero adjustment is repeated every time the operation signal T is sent from the controller. Therefore, errors caused by dirt on the light transmitting surface of the detection cell 11 that occur within a predetermined time period corresponding to the operating time of the timer circuit 20 are nullified. Of course, this also means that the zero adjustment at the start of the blood leak detection operation is automatically performed.

The operation of the gate circuit 21 by the timer circuit 20 does not perform zero adjustment for the concentration signal d due to substantial blood leakage, but is caused by dirt such as waste matter adhering to the transmitted light surface of the detection cell 11. Preferably, only the error is nullified. Through in vitro tests, the inventors found that it is preferable to set the timer circuit 20 to 7 minutes or more in order to satisfy the above conditions, and that if the set time is too long, the configuration of the timer circuit 20 and the memory circuit 22, the discharge of the capacitor 25, etc. will affect the mounting process.
The results showed that approximately 10 minutes was appropriate.

Furthermore, if the concentration signal d is automatically zero-adjusted after the first concentration determination circuit 28 is activated, it will no longer be possible to continuously indicate the state of blood leakage. Timer circuit 2
Since the operation of the automatic zero adjustment circuit 16 is thereby interrupted, the blood leakage state can be continuously detected. Once the automatic zero adjustment circuit 16 has been interrupted, when the operator presses a reset button (not shown), a reset signal R is generated, and this reset signal R is applied to the gate circuit 21 to stop its operation. It will be restarted.

As detailed above, the present invention uses a light emitting element as a light source to ensure a longer lifespan than a conventional incandescent light bulb, and the peak value of the spectral wavelength characteristic of the light emitting element is determined by the absorption of blood. Since it exists within a range that includes the spectrum, there is no need to use a special filter as in the past, and
It becomes less susceptible to changes in the concentration of waste components contained in the test liquid. In particular, the output signal from the light emitting element is converted into a concentration signal by an automatic zero adjustment circuit, and while this concentration signal is periodically converged to zero, a notification circuit is used to notify of blood leakage. It is possible to provide a blood leakage detection device that automatically eliminates concentration detection errors caused by objects, etc., and can therefore reliably detect blood leakage and can stably continue its operation. In addition, since zero adjustment is performed in synchronization with the start of the blood pump using the start signal from the pump synchronization circuit, zero adjustment is reliably performed before the start of blood processing, resulting in improved blood leakage detection accuracy. Improve further. Furthermore, when the amount of blood leakage exceeds a predetermined level, the first concentration determination circuit stops the operation of the timer circuit, thereby preventing automatic zero adjustment, so that the state of blood leakage can be continuously detected. In addition, if the amount of blood leakage further increases, the second concentration determination circuit stops the operation of the blood processing apparatus, which is excellent in safety.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a blood leak detection device according to the present invention, and FIG. 2 is an electric circuit diagram showing an example of a memory circuit of the same device. 11...Detection cell, 12...Light emitting element, 13...
...Light receiving element, 16...Automatic zero adjustment circuit, 27...
Detection circuit, 41... Concentration signal generation circuit, 42...
Reference signal generation circuit, a...output signal, b...reference signal, d...density signal.

Claims (1)

[Scope of Claims] 1. A detection cell 11 that guides a sample liquid used in a blood processing device; and a detection cell 1 in which the peak value of the spectral wavelength characteristic is within a range that includes the absorption spectrum of blood;
1, and the light emitting element 12 that has passed through the detection cell 11.
a light receiving element 13 that receives light from the light receiving element 13 and outputs an electric signal corresponding to the amount of light; and a density signal generator that generates a density signal d corresponding to the difference between the output signal a from the light receiving element 13 and a reference signal b. A circuit 41, a timer circuit 20 that starts timing in response to a start signal S output from the pump synchronization circuit 23 in synchronization with the start of the blood pump, and a timer circuit 20 that starts timing when the start signal S is received and by the timer circuit 20. an automatic zero adjustment circuit 16 including a reference signal generation circuit 42 that captures the concentration signal d at a predetermined timing, outputs it as the reference signal b, and holds the reference signal b until the next timing; Drive stop circuit 3 to stop
3, an alarm circuit 32, a first concentration determination circuit 28 that activates the alarm circuit 32 and stops the operation of the timer circuit 20 when the concentration signal d exceeds a first level; Blood leakage detection comprising a detection circuit 27 having a second concentration determination circuit 29 that activates the drive stop circuit 33 when the concentration signal d exceeds a second level higher than the first level. Device. 2 The blood processing device is a hemodialysis device, the test liquid is a dialysate, and the predetermined timing of the timer circuit is set to once every 7 to 10 minutes. Blood detection device.