JPS63143080A - Air bubble detector - 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 (Field of Industrial Application) The present invention relates to a device for detecting the presence of air bubbles or lack of fluid in an infusion or blood circuit.

(Prior art) Conventionally, blood circuits and infusion circuits monitor the flow rate of blood or infusion fluid delivered to a patient, and also separate air bubbles present in the circuit to prevent air bubbles from entering blood vessels. A drip chamber is provided for this purpose. However, if air bubbles enter the circuit rapidly or in large quantities, it is actually difficult to separate the air bubbles in the drip chamber. If air bubbles that cannot be separated in such a drip chamber enter the patient's veins, it may be fatal to the patient. Therefore, it is imperative to detect air bubbles contained within the infusion or blood circuit. As a device for automatically detecting air bubbles contained within such an infusion or blood circuit,
For example, by installing a light emitter on one side of the circuit and a light receiver on the other side, setting a voltage value corresponding to the amount of transmitted light as a reference value in advance, the amount of transmitted light to the circuit is converted into a voltage signal via a photoelectric conversion element. An apparatus has been proposed that detects the presence or absence of bubbles by converting the voltage signal and comparing the voltage signal with the reference voltage value.

(Problem to be Solved by the Invention) The method for detecting the change in the absolute value of the amount of transmitted light includes an increase or decrease in the amount of transmitted light due to changes in the concentration of the infusion or blood, the shape of bubbles, the transparency of the infusion or blood circuit, etc. Since the difference exists as an optical noise component, the following problem occurs when the difference in the amount of transmitted light is small. That is, as shown schematically in FIG. 9, it is assumed that bubbles a and b having different amounts of transmitted light are mixed in the infusion or blood circuit 1. If the preset reference voltage level is set as Vo+, and a state in which the level of the voltage proportional to the amount of transmitted light is lower than the reference voltage level Vo+ is determined to be the presence of bubbles, bubbles a in the circuit cannot be detected. Even if bubbles are detected, the amount of change in the amount of transmitted light is too small, resulting in the inconvenience that bubbles cannot be detected. If the above reference voltage level is VO2, bubbles a and 2 can be reliably detected, but since the optical noise component in the range W is also lower than the reference voltage VO2, a signal indicating the presence of bubbles is output in this range W. I end up. Further, when the signal component becomes equal to or lower than the optical noise component, the bubbles a and b can no longer be detected. These problems cannot be avoided as long as bubbles are detected by comparing the level of the amount of transmitted light with a reference value level.

(Means for Solving the Problems) The present inventors have arrived at the present invention as a result of intensive studies to solve the above-mentioned problems of conventional devices and provide a device that can reliably detect bubbles. be.

is placed on one side of the blood circuit to irradiate light onto the circuit, and is placed on the opposite side of the circuit to receive the light irradiated onto the circuit and convert it into an electrical signal. A light receiving means for outputting light, a light emitting intensity control means for transmitting a signal to control the light emitting intensity to the light emitting means according to the strength of the output signal from the light receiving means, and a signal that follows the output signal from the light receiving means with a delay. A delay circuit that transmits a signal, a bias circuit that biases the signal from the delay circuit, a comparator that compares the output signal from the light receiving means with the bias signal from the bias circuit, and the output of the comparator is This bubble detection device is characterized by being equipped with a differential circuit that detects reversal.

(Example) Next, one embodiment of the device of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of the apparatus of the present invention, where 1 is an infusion or blood circuit, and 4 is a light projecting means for irradiating the circuit with light, which uses a light bulb or a light emitting element as a light source.

5 is a light receiving means such as a photoelectric conversion element that receives transmitted light and converts a change in the amount of transmitted light into an electric signal; 6 compares the magnitude of the signal from the photoelectric conversion element 5 with a reference setting device 7, and determines whether or not to emit light; A light emission intensity control means for controlling the light emission intensity of the light receiving means 4; 8 is a bubble detection signal conversion circuit that converts the signal from the light receiving means 5 into a bubble detection signal and outputs it, and follows the signal from the light receiving means 5 with a delay. Delay circuit that generates the signal9. A bias circuit 10 that biases the signal from the delay circuit 9, a comparator 11 that detects the magnitude of the signal from the light receiving means 5 and the signal from the bias circuit 10, and a differentiation circuit 12 that detects the moment when the signal from the comparator 11 is inverted. , a storage circuit 15 that stores signals from the differentiating circuit 12.

Further, the optical axis of the light emitting element of the light projecting means 4 and the light receiving and converting element of the light receiving means 5 is at an angle θ of 15 to 45 degrees, usually 30 degrees, as shown in FIG. 1 with respect to the infusion or blood circuit. As shown in FIG. 8, the structure is such that the amount of light received changes greatly due to reflection of light on the liquid surface when the liquid runs out.

Next, regarding the operation of the device of the present invention having the above configuration,
This will be explained with reference to FIGS. 1 to 5 and 7.

The light emitted by the light emitting element LED of the light emitting means 4 is received by the phototransistor PHTr of the light receiving means 5 and converted into a voltage signal, and the converted voltage signal is sent to the light emission intensity control means B and the reference setting device 7. It is compared with a reference signal, and if it is smaller than the reference voltage, a large voltage is emitted and the light emitting means 4
It feeds back to TR+ of the light emitting element, and increases the light emitting current of the light emitting element LED.

The light emission intensity is increased, and when the reference voltage signal is larger than the reference voltage signal, a small voltage is emitted and fed back to the transistor TR+ of the light emitting means 4, the light emission current of the light emitting element LED is decreased, and the light emission intensity is weakened. Furthermore, the emission intensity control means 6 contains Cs.
, Rs, and the above-mentioned feedback voltage has a time limit calculated by C3XR4, and changes slowly, due to concentration changes in the infusion or blood circuit, dirt on the circuit, and the lens part of the light emitting/receiving element. When the amount of transmitted light changes gradually due to dirt, etc., a feedback correction is made to follow it, and a voltage signal with the same value as the reference voltage signal and without any change is output from the light receiving means 5, and when a bubble is detected. When there is a sudden change in the received light intensity, the feedback correction voltage signal of the light emission intensity controller cannot follow the sudden change in the received light intensity, and the light receiving means 5 outputs a sudden change in the received light intensity voltage signal.

On the other hand, the voltage signal (signal C) outputted from the light receiving means 5 simultaneously enters the signal delay circuit 9 and is delayed with a time constant corresponding to the change in the signal C to produce a signal σ' to follow. The bias circuit 10 adds (or subtracts) the bias voltage
X). The signal C from the rectifier circuit 7 and the above signal C'
are compared in magnitude by a comparator 11 at the next stage. As shown in FIG. 2, when the change in signal C is larger than the time constant in the signal delay circuit and the signal C'
follows the signal C almost equally, so a relationship holds true: signal C<signal σ. On the other hand, when there is a sudden movement smaller than the time constant in the signal delay circuit, the signal σ cannot fully follow the signal C, and a large voltage difference appears between the signal σ and the signal C in a short period of time. If the difference voltage is larger than the bias voltage X applied to the bias circuit 10, the signal C-signal c'
The relationship >x is established, and the relationship between the signal C and the signal σ is as follows: signal C>signal, the magnitude relationship between the signal C and the signal σ compared by the comparator 11 is inverted, and the output of the comparator is also inverted. The time when the inverted signal changes is detected by the next differentiating circuit 12.
is detected and stored in the memory circuit 13.

The sudden movement signal of the stored signal is relay driver 1
4 energizes the relay 16, and its contact signal stops the infusion or blood pump or closes the shutoff valve to prevent air bubbles from entering the patient. Alternatively, the contact signal may be sent to the buzzer driver 15 to cause the buzzer 17 to sound. The sudden movement signal of the stored signal is canceled by the reset signal 1.

An example of a specific electric circuit of the signal delay circuit 9 and the bias circuit 10 is shown in FIG. Figure 3 (1-1), (1-2)
is a circuit that can be applied when the signal C suddenly changes in the increasing direction, and Figure 3 (2-1) and (2-2) is a circuit that can be applied when the signal C suddenly changes in the decreasing direction. . Figure 3 (In 1-IJ, the delay time constant is roughly calculated by CXR (seconds), and the bias voltage X is determined by using the forward voltage drop of the diode. Therefore, X = Vo
The υ bias voltage is given by appropriately selecting the number n of diodes using the relational expression n.

In Figure 3 (1-2), the delay time constant is approximately Cx(R
+Rv) seconds, and the bias voltage X is the variable resistor R
The variable resistor Rv is appropriately adjusted in response to the voltage drop occurring across the voltage V, resulting in a divided voltage. Figure 3 (
2-1), <2-2) Regarding K, the way of applying the delay time constant and bias voltage is the same as in FIG. 3 (1-1) and (1-2). The delay time constant and bias voltage are determined to be optimal values depending on the size and speed of the bubble to be detected.

Changes in the amount of transmitted light, such as changes in the concentration of transfusion or blood, dirt on the circuit, dirt on the lens of the light emitting/receiving element, etc., change relatively slowly, so they are corrected by the light emission intensity controller 6 and the fluctuations are corrected. In addition, there is almost no difference between the signal C and the signal C', and the relationship of signal C and signal C' is established, so erroneous operation due to the above disturbance is unlikely to occur. .

When air bubbles are mixed in, diffuse reflection and refraction of light occur at the boundary between the liquid and air bubbles, and the light receiving condition changes significantly in an instant, so signal C' cannot fully follow the movement of signal C.
A difference larger than the bias voltage appears between the signal C and the signal C', so that a bubble can be reliably detected.

Next, an example in which the device of the present invention is attached to a hemodialysis device is shown in the fourth example.
This is shown in figure 70- of the figure. In FIG. 4, blood returns to the vein V via the artery A, the blood circuit 27, the blood pump 24, the hollow fiber dialyzer 25, the drip chamber 26, the detection section 21 of the device of the present invention, and the shutoff valve 23. Detection part 2
1 and the shutoff valve 23 are connected to the control unit 22 by electrical wiring. Further, the drive wire for the blood pump 24 is supplied through the control unit 22 in order to stop the pump drive and stop the flow of blood during operation of the device of the present invention. Normally, air bubbles that enter the blood circuit are removed by the drip chamber 26, but in the unlikely event that the air bubbles cannot be removed by the drip chamber 26, the detector 21
When a bubble passes through, a detection signal from the detector 21 is sent to the control unit 22, which amplifies the signal and closes the shutoff valve 23. At this time, the power supply for driving the blood pump 4 is also cut off at the same time, the blood pump 24 is stopped, and blood feeding is interrupted.

FIG. 5 shows a case in which body fluids and replacement fluids are injected into a vein using head pressure, and FIG. 6 shows a case in which they are injected intravenously from a drip bottle 39 suspended from a hanger ball 31. The liquid exiting the drip bottle is injected into the vein V via the drip chamber 26, the detection unit 21, the flow rate adjustment valve 32, and the shutoff valve 26.

In this case, since a blood transfusion pump is not required, the control section 22 only needs to close the shutoff valve 25 based on the signal from the detection section.

The detection unit 21 has a built-in light emitter and receiver, which is embedded in the holding unit 45, 46 so that its optical axis is at 20° with respect to the structural through-hole 47 that can be easily attached to the blood circuit (or infusion circuit). It is. Preferably, the shutoff valve 25 also has a structure that can be easily attached to the blood circuit, such as a pinch pulp valve.

(Effects of the Invention) As described above, the device of the present invention automatically controls the light emission intensity according to the amount of received light, and is normally controlled at the front stage so that the received light voltage signal is almost constant, and with respect to the received light voltage C. By following an appropriately biased signal σ with a slight delay, there is no need to adjust the sensitivity to changes in the concentration of the infusion or blood circuit or variations in the amount of light transmitted through the circuit, and bubbles or liquid shortages can be reliably detected. It's now possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the control circuit of the device of the present invention, FIG. 2 is a signal waveform in the control circuit, FIG. 6 is a circuit diagram showing an example of a delay circuit and a bias circuit, and FIG. Figure 4 is a flow diagram showing an example in which the device of the present invention is installed in a hemodialysis circuit, Figure 5 is a flow diagram showing an example in which the device is installed in an infusion circuit, and Figure 6 is an example of a light emitter/receiver. A cross-sectional diagram showing
FIG. 7 is an example of an electric circuit diagram showing emission intensity control,
Figure 8 is a principle diagram showing the reflection of light when the liquid runs out, Figure 9
The figure is an explanatory diagram of a conventional device. 1...Blood or infusion circuit 4...Light emitting means 5...Light receiving means 6...-Emission intensity control means 7...Reference setting device 8...Bubble detection signal conversion circuit 9...Delay circuit 10...Bias circuit 11...Comparator 12...Differentiation circuit 13...・・・Memory circuit

Claims (1)

[Scope of Claims] 1. A device for detecting the presence of air bubbles in an infusion or blood circuit, comprising: a light projector disposed on one side of the infusion or blood circuit to irradiate the circuit with light; A light receiving means is disposed on the opposite side of the circuit and receives the light irradiated onto the circuit, converts it into an electric signal, and outputs the same; A light emission intensity control means for transmitting a control signal, a delay circuit for oscillating a signal that follows the output signal from the light receiving means with a delay, a bias circuit for biasing the signal from the delay circuit, and an output signal from the light receiving means. A bubble detection device comprising: a comparator that compares an output signal with a bias signal from a bias circuit; and a differentiation circuit that detects that the output of the comparator is inverted due to the presence of bubbles. 2. Claim 1, wherein the optical axes of the light projecting means and the light receiving means are angled with respect to the axis of the infusion or blood circuit.
Air bubble detection device as described in section.