JPH06237998A - Detection of air bubble - Google Patents

Abstract

PURPOSE:To provide an exact detection method which does not erroneously recognize the air bubble existing in a circuit as a transparent liquid such as physiological salt soln. by detecting the discontinuous point of the continuous signals of the light transmitted quantity or light reflected quantity taken out of an air bubble detector. CONSTITUTION:The light transmitted quantity or light reflected quantity possessed in the intra-circuit liquid is continuously taken out as signals from the air bubble detector based on a photodetection system installed in an external- circuit device and the air bubble in the circuit is detected by detecting the discontinuous points of the continuous signals. The measurement is executed by the following procedure: First, a blood pump 5 is rotated and a clamp 4 is opened to circulate the physiological salt soln. This clamp 4 is closed and a clamp 3 is opened to circulate the blood after the circuit is internally filled with the physiological salt soln. The clamp 3 is closed and the clamp 4 is opened to fill the inside of the circuit again with the physiological salt soln. after the operation for a specified period of time since the circuit is internally filled with the blood alone. The prescribed quantity of the air is injected into the circuit and is detected by the air bubble detector 7 in the respective processes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reliably detecting bubbles in a circuit such as an extracorporeal blood circulation device or a device circuit for introducing a liquid such as Ringer's solution into the body.

[0002]

2. Description of the Related Art Blood such as cardiopulmonary bypass, dialysis, and plasmapheresis is derived from the outside of the body and subjected to some treatment and then returned to the body. In a circuit or the like that introduces into or recirculates into, it is essential to detect air bubbles in the circuit and take some measures such as stopping the device to prevent blood containing these air bubbles from returning to the body as it is. As a method for detecting bubbles, an optical detection detection method, an ultrasonic detection method, etc. are commonly used.

[0003]

[Problems of the prior art] However, although the optical detection method is excellent in terms of simplicity in assembling into a device and low cost, it has a problem in detection accuracy. On the other hand, the ultrasonic detection method is excellent in detection accuracy. , It is difficult to align the circuit and the detector,
There is a problem that the price is also high. Furthermore, in the conventional detection method, the amount of light transmission is 0 V when the voltage signal is extracted while only blood is being detected, and the voltage is high when bubbles in blood are detected, which is a so-called range. Bubbles are detected by the way of thinking as a value.Normally, the threshold voltage is set according to the electrical characteristics of each photodetector, and when the detector outputs a voltage higher than the threshold voltage, it is recognized as a bubble. Measures such as alarms, equipment stoppage, etc. will be taken.

However, in an extracorporeal blood circulation device or the like,
For example, at the start of treatment, when drawing blood out of the body, in order to avoid contact between blood and air at the interface, the circuit must be filled with a liquid such as saline, and the blood should not contact the interface with saline. While being maintained or partly mixed, it is transported in the circuit and returned to the patient's body. Further, at the end of the treatment, the blood remaining in the circuit is pushed out and returned by physiological saline.

In the above case, the fluid in the circuit includes physiological saline, blood, and air depending on the case, and the output voltage of these fluids is higher from the clear liquid (physiological saline), air, and blood. Therefore, in the case of detection using the threshold value, there is a high possibility that a change in voltage at the interface between the transparent liquid and blood is caught as the presence of bubbles. As described above, in the light detection method, there is always a phase that causes a malfunction, and an operator monitors the phase to prevent it.

[0006]

SUMMARY OF THE INVENTION According to the present invention, when operating an extracorporeal blood circulation device or the like, an air bubble (air) existing in the circuit is not erroneously recognized as a transparent liquid such as physiological saline, and is accurately measured. An object is to provide a detection method.

[0007]

A fluid in a circuit of a blood extracorporeal circulation device is a transparent liquid such as physiological saline, a mixture of blood and a transparent liquid, blood, blood and a transparent liquid at the start or end of operation. It goes through the process of liquid mixture, transparent liquid. Therefore, the output signal obtained from the detector always changes continuously. Therefore, the sudden change (discontinuity) in the output signal is
It means mixing of fluid other than the above process, that is, bubbles.

According to the present invention, the amount of light transmission or the amount of light reflection of the liquid in the circuit is continuously taken out as a signal from a bubble detector based on the light detection system installed in the extracorporeal circuit device, and the continuous signal is not detected. The present invention relates to a method for detecting bubbles in a circuit by detecting bubbles in a circuit by detecting continuous points. In the present invention, the extracorporeal circuit device means any circuit in case of introducing cardiopulmonary bypass, dialysis, blood purification, etc. to circulate and circulate blood outside the body, and drip, etc., and to introduce Ringer's solution into the body from the outside, medicine, etc. means.

[0009]

According to the bubble detecting method of the present invention, a transparent liquid such as physiological saline is not erroneously detected as a bubble, and a small voltage (in other words, a voltage lower than the threshold of the detector). For example, the presence of bubbles in the circuit can be reliably detected even with an extremely small amount of bubbles).

The present invention will be described in detail below with reference to examples. FIG. 1 shows a circuit used in the embodiment. The blood pump 5 is rotated at a predetermined rotation speed, and first, the clamp 4 is opened to allow the physiological saline to flow. When the circuit is filled with physiological saline, the clamp 4 is closed and the clamp 3
To open the blood for circulation. After the circuit is filled with blood only and the operation is continued for a certain time, the clamp 3 is closed, the clamp 4 is opened, and the circuit is filled with physiological saline again. Meanwhile, in each process, a predetermined amount of air is injected into the circuit by the syringe 6. The output voltage from the bubble detector 7 is converted into a digital signal by the A / D converter, processed by the processing circuit 9, and then recorded by the recorder 10.

[0011]

【Example】

Example 1 Bubbles were detected by the circuit shown in FIG. First, the circuit on the physiological saline side was opened, the circuit was filled with physiological saline, and after 2 seconds, the circuit on the blood side was opened and blood was introduced into the circuit. After about 15 seconds, after confirming that the inside of the circuit was completely replaced with blood, the operation was continued for about 14 seconds.
Then, physiological saline was again introduced into the circuit. After about 15 seconds, the inside of the circuit was completely replaced with physiological saline again.
Then, in each process, a 0.
5 ml of air was injected and the output voltage from the bubble detector (output voltage was 0V for blood, 9V for air, 12V for clear liquid) was continuously recorded. The pump flow rate was 100 ml / min throughout the experiment. A vinyl chloride tube having an inner diameter of 3.2 mm was used as a material for forming the circuit.

When the circuit was filled with physiological saline, the output voltage was 12V. Then, the voltage was successively and linearly decreased by the introduction of blood, and became 0 V when the inside of the circuit was completely replaced with blood. After operating for a certain period of time, by introducing physiological saline again, the voltage sequentially and linearly rises, and when the inside of the circuit is completely replaced with physiological saline, 1
It became 2V. Although 0.5 ml of air was injected in each process, the output voltage instantaneously rises to 9.2 V, and the continuous voltage line is disturbed (discontinuity point) to reliably trap the inclusion of bubbles. I was able to.

In the present embodiment, since the voltage in the case of air is 9 V, this numerical value becomes the threshold value, and if the operation is started in the view of the threshold value, the circuit is initially filled with physiological saline. At the stage of, it is recognized as a bubble and the driving cannot proceed any further.

Example 2 The same circuit as in Example 1 was used, and the operation was carried out by the same procedure with only an air injection amount of 0.05 ml. The basic voltage change was the same as in Example 1. However, since the amount of air injected was small, a voltage change of about 1 V was observed in the process of mixing blood and physiological saline, and a voltage of 0 V was generated in the process of filling blood with bubbles. When it was captured, the voltage was about 3.2V. Still, the goal of bubble detection was fully achieved. Also in this case, if it is regarded as a threshold value, as in the case of the first embodiment, it is recognized as bubbles at the initial stage when the inside of the circuit is filled with the physiological saline, and the operation cannot proceed any further. When the amount of air is very small as in the second embodiment, in addition to that, the detector is temporarily stopped in the initial stage, and the detector is activated after the blood increases and the voltage exceeds the threshold value 9V. Even if such a troublesome operation is performed, the voltage due to the bubbles in the process of being filled with blood is 3.2 V, so the detector with the threshold value of 9 V used cannot detect this, and the bubbles are mixed. Will be overlooked.

[0015]

[Brief description of drawings]

FIG. 1 shows a blood flow circuit for detecting air bubbles. The broken line shows the flow of signals.

[Explanation of symbols]

 1 Blood Bag 2 Saline Solution Bag 3, 4 Clamp 5 Blood Pump 6 Syringe (Bubble Injector) 7 Bubble Detector 8 Analog / Digital Converter 9 Arithmetic Processing Circuit 10 Recorder

Claims (1)

[Claims] 1. A light-transmission amount or light-reflection amount of a liquid in a circuit is continuously taken out as a signal from a bubble detector based on a light detection system installed in an extracorporeal circuit device, and a discontinuous point of the continuous signal. A method for detecting air bubbles in an extracorporeal circuit device, characterized by detecting air bubbles in a circuit by detecting.