WO2008050218A2

WO2008050218A2 - Apparatus and method to detect the presence of bubbles and to eliminate them.

Info

Publication number: WO2008050218A2
Application number: PCT/IB2007/003187
Authority: WO
Inventors: Gino Grassi; Luciano Alcidi; Marzia Nardiello; Franco Papa
Original assignee: Gino Grassi; Luciano Alcidi; Marzia Nardiello; Franco Papa
Priority date: 2006-10-27
Filing date: 2007-10-24
Publication date: 2008-05-02
Also published as: ITFI20060265A1; WO2008050218A3

Abstract

An apparatus (1) for the detection and removal of bubbles of gas (11) from a flow of medical fluid emitted by an injector (2) and directed towards catheter (3), comprising a section of tube (4) connected to the injector (2) and to the catheter (3), a bubble-detection sensor (7), a suction pump (12) and an electronic unit (9) to command the pump (12) to suction off a defined quantity of fluid from the tube (4) when the bubble is (11) is detected.

Description

Apparatus and method to detect the presence of bubbles and to eliminate them.

Technical field

This invention refers to an apparatus and a method to detect the presence of bubbles of gas in a hydraulic circuit for injection and/or infusion of medical fluids via a catheter, and to eliminate them.

Background art

It is known that in diagnostic procedures which involve the injection and/or infusion of substances into the arterial or venous circulation, it is indispensable to avoid even any accidental injection of bubbles of gas while this procedure is being carried out. The accidental infusion of these bubbles can in fact cause serious damage to the patient such as embolisms or cerebral ischemia.

Injection and/or infusion devices are currently known that are equipped with bubble detection systems based on the ultrasound Doppler principle or on optic systems. The minimum size of the bubbles that can be detected by means of the known devices is in the region of ¹A inch in length.

This size limitation gives rise to a first drawback.

In fact, if the devices detect a bubble which is larger than the limit indicated above, they function correctly and discontinue the injection. Vice versa, when the dimensions of the bubble (or cluster of bubbles) are smaller than the indicated limit, the known devices are unable to detect it/them and thus to warn the operator of the malfunctioning.

A second drawback of the known bubble-detection devices consists of the fact that, once the presence of one or more gas bubble has been detected in the hydraulic circuit connected to the catheter, it is necessary to discontinue the injection and to remove the bubble from the circuit by means of washing techniques.

Disclosure of the invention A first aim of this invention is to overcome the size limits imposed by the known bubble-detection devices. A further aim is to provide a device which in addition to detecting bubbles in the circuit, also automatically removes them.

These aims are achieved by means of an apparatus, a device and a method for detecting and removing bubbles inside a hydraulic circuit according to the accompanying claims.

Brief Description of the Drawings

The characteristics and advantages of this invention will become clearer on reading the non-binding description of a preferred but not exclusive embodiment of the invention, as illustrated in the accompanying drawings in which:

- figure 1 shows a bubble detection device in conditions of normal use according to this invention;

- figure 2 shows the device of figure 1 with a gas bubble in the hydraulic circuit; - figure 3 shows the device of the previous figures in conditions of normal use, connected to a pump for removal of the bubble;

- figure 4 shows the device of the previous figure with a bubble to be removed;

- figure 5 is a schematic view of the various functioning steps of the automatic detection and removal of the bubbles;

- figure 6 shows an apparatus according to this invention which satisfies the functioning logic shown in figure 5;

- figure 7 is a schematic view of the electronic part of an apparatus according to this invention; - figure 8 shows a second preferred embodiment of a bubble detection device in conditions of normal use according to the invention, without bubbles;

- figure 9 shows the device of figure 8 with a gas bubble in the hydraulic circuit;

- figure 10 is a schematic view of the various functioning steps of the automatic detection and removal of the bubbles in the device in figure 8.

Description of the Preferred Embodiments of the Invention

With reference to the accompanying figures, a description is given of an apparatus 1 for the detection and removal of bubbles of gas from a flow of medical fluid, emitted by an injector 2 and directed towards an infeed tube of a catheter 3. 7

-3-

The described apparatus 1 comprises a section of tube 4 with a first input end 5 connected to the injector 2 and a second output end 6 connected to the catheter 3 and a sensor 7 for detecting bubbles carried by the fluid through the tube 4 fitted in a predetermined position in the section of tube 4 between the first 5 and the second end 6.

The apparatus 1 also comprises a branch 8 located in an intermediate position between the first end 5 and the sensor 7 connected hydraulically to a suction pump 12, preferably peristaltic, and an electronic unit 9 equipped with electrical connections 10 to, respectively: - the sensor 7, to receive a signal "X" indicating detection of a bubble 11,

- the injector 2, to send a signal for discontinuation of the injection if the sensor 7 detects a bubble and

- the suction pump 12 to activate it to suction off a defined quantity of fluid contained inside the tube 4 when the bubble 11 is detected by the sensor 7 in order to remove the bubble.

The first 5 and the second end 6 of the tube 4 can be equipped with connectors 13 for easy disconnection of the apparatus 1 from, respectively, the injector 2 and the catheter 3.

The apparatus advantageously comprises means 14 to close the access to the branch 8 in the presence of an input flow from the injector 2, that is to say in normal injections conditions without the presence of gas bubbles 11 in the medical fluid.

In a preferred embodiment of the apparatus 1 according to this invention, the sensor 7 checks for the presence of one or more bubbles 11 by measuring the electrical conductivity of the fluid which is present, in that moment, between two electrodes 15, 16.

Advantageously, the two electrodes 15, 16 are positioned inside the tube 4, passing right through its internal diameter.

In this way it is possible to detect whether bubbles 11 are present or not throughout the tube 4.

The electrodes 15, 16 are preferably fitted in a section of the tube 4 in the injection circuit which has a diameter similar to the diameter of the catheter 3 inserted in the patient's vein or artery.

The specific electrical conductivity of the portion of fluid transiting between the two electrodes 15, 16 is defined by the position of the electrodes 15, 16 and is significantly modified when there is at least one, even very small, gas bubble 11 present in the flow of fluid. A change in the value of electrical conductivity measured between the two electrodes 15, 16 activates the sensor 7 to generate a signal "X".

The signal "X" is amplified and compared with a predefined threshold value "S", causing discontinuation of the flow from the injector 2 and the simultaneous start-up of the pump 12 in order to remove the quantity of fluid containing the gas bubbles 11.

Advantageously, the electrical connections 10 between the unit 9 and the injector 2, the sensor 7 and the pump 12 are the removable type, thus allowing a disposable sensor 7 to be used. A further aspect of this invention is a method for the detection and removal of gas bubbles in a flow of medical fluid emitted by an injector 2 and directed towards an infeed tube of a catheter 3, characterised in that it comprises the following steps:

- preparation of a section of tube 4 with a first input end 5 connected to the injector 2 and a second output end 6 of the fluid directed towards the catheter 3;

- detection of the passage of a bubble 11 through the tube 4;

- suction from the tube 4 of a defined quantity of fluid in response to the detection of the bubble 11 in order to remove the bubble 11 trapped in the quantity of fluid suctioned off. The flow of fluid injected in the tube 4 is therefore discontinued in response to the detection of the bubble 11 by the sensor 7.

The quantity of fluid to be suctioned off by the pump 12 or to be injected in the catheter 3 is determined by maintaining the fluid flow suction step and the injection discontinuation step respectively operative for a predetermined period of time.

Advantageously, the inner diameter of the tube 4 is similar in size to the diameter of the catheter 3, so as not to create potential obstacles to the flow of the fluid, which could generate turbulence and thus microbubbles of gas.

With reference to figure 7, a functional diagram shows how the apparatus 1 according to this invention is controlled.

In particular, the sensor 7 is powered by a preferably alternate current generator 20, so that when a bubble 11 is detected, the signal "X" is generated.

The signal "X" is amplified by a first amplifier 21 and is then compared with a threshold value "S" by a second amplifier 22. From this comparison, the signal "X" passes to the logics unit 23 which reads it and programs a delay "r". The delay "r" determines the period of time in which the blocking and startup of the injector 2 and the pump 12 will simultaneously take place.

Figure 5 shows the conditions of use (A) of the sensor 7, (B) of the unit which programs the delay, (C) of the injector 2 and (D) of the suction pump 12; all on a time basis.

In particular:

(A): the detection of a bubble 11 inside the tube 4 causes the sensor 7 to emit a signal "X" for a certain period of time "t";

(B): the end of the signal "X" determines a programmable delay "r", lasting "tl" (C) - (D): the delay "r" added to the duration "t" of the signal "X" simultaneously activates the discontinuation and the start-up of, respectively, the injector 2 and the suction pump 12, both for the period of time "tl+t".

By means of this functioning logic it is possible to calculate the quantity of fluid containing the bubble, appropriately rounded up, to be suctioned off through the pump 12.

With reference to figures 8-10, a preferred embodiment of the device is described, in which the same reference numbers already used with reference to figures 1-7 are also used for the already described corresponding parts. In this embodiment, the injection system is a manual system 25, in which the possibility of an operator injecting fluid is conditioned by the open/closed status of the control 26 of a solenoid valve 24 positioned downstream of the manual injector.

During functioning, if no bubbles are present the flow proceeds as indicated by the arrows in figure 8, while if a bubble of gas 11 is detected, the sensor 7 produces an electrical signal X and transmits it to the electronic unit 9 which sends a command C to close the solenoid valve 24 and a command D to start the suction pump 12. The signal X also determines the activation of a time delay "r" the amplitude of which can be predetermined in order to define the period of activity of the pump 12 and thus the quantity of liquid that must be suctioned off by the pump 12 (figure 9) to remove the bubble 11 from the hydraulic circuit. This invention presents a series of advantages.

A first advantage consists of the fact that the sensor 7 can be dimensioned in order to obtain maximum response sensitivity according to the minimum dimensions of the bubbles 11 to be detected.

In fact, the minimum dimensions of the bubbles 11 that can be detected are directly proportional to the inner diameter of the section of the tube 4 in which the electrodes 15, 16 are positioned. This means that an apparatus 1 according to this invention can be equipped with different types of sensors 7 with specific sensitivities for each type of application and requirement.

A second advantage consists of the fact that the use of the apparatus 1 according to this invention makes it possible not only to detect the presence of a bubble 11 but also to remove it efficiently and automatically without the intervention of the operator.

This advantage is determining both in terms of time saving and of hygiene and safety, these aspects being of fundamental importance in the health sector. An additional advantage consists of the fact that it is possible to detect gas bubbles 11 using new or pre-existing injectors 2, possibly without having to carry out procedures for washing the entire apparatus.

In fact, thanks to the presence of practical and easy to use connectors 13 it is possible to use a single removable sensor 7, positioning it between the injector 2 and the catheter 3.

Yet another advantage consists of the fact that by using an apparatus 1 and a sensor 7 according to this invention it is possible to detect bubbles 11 much smaller in volume and size than those that could formerly be detected with traditional devices. The invention as described above is susceptible to obvious industrial application; it can also be the subject of numerous modifications and variations all within the scope of the disclosure of the invention; all the parts can also be replaced by technically equivalent elements.

By way of example, although the use of conductivity measurement detection sensors has proved to be particularly advantageous in a system for the detection and removal of bubbles, it is also possible to use different types of bubble sensors, for example ultrasound or optic sensors, without departing from the scope of the invention.

Claims

1. An apparatus (1) for the detection and removal of bubbles of gas (11) from a flow of medical fluid emitted by an injector (2) and directed towards an output device (3), characterised in that it comprises: a section of tube (4) with a first input end (5) for the fluid coming from the injector (2) and a second output end (6) for the fluid directed towards the output device (3); a sensor (7) for detecting bubbles carried by the fluid passing through the tube (4), the sensor (7) being fitted in a predetermined position of the tube (4); a branch (8) of the tube (4) located in an intermediate position between the first end (5) and the sensor (7) fitted in the tube (4); an electronic unit (9) equipped with electrical connections (10): to the sensor (7) to receive a signal indicating detection of a bubble (11), to the injector (2) to send a signal to discontinue the injection flow in the tube (4) when a bubble (11) is detected by the sensor (7), and to a suction pump (12) connected hydraulically to the branch (8), so that the unit (9) can activate the pump (12) to suction off a determined quantity of fluid from the tube (4) when a bubble (11) is detected by the sensor (7) and remove the bubble (11) trapped in the suctioned fluid.

2. An apparatus according to claim 1, in which the first (5) and second end (6) of the tube (4) are equipped with connectors for the removable connection of the apparatus (1) to an injector (2) and to a connection tube to a catheter (3).

3. An apparatus according to claim 1 or 2, comprising means to close (14) the branch (8) in the presence of a flow coming from the injector (2).

4. An apparatus according to any of the foregoing claims, in which the signal emitted by the electronic unit (9) is a signal enabling the injector (2) to recommence the injection.

5. An apparatus according to any of the foregoing claims, in which the signal emitted by the electronic unit (9) is an automatic signal for recommencement of the injection.

6. An apparatus according to any of the foregoing claims, in which the sensor (7) measures the electrical conductivity between two electrodes (15, 16) which are in communication with the inside of the tube (4).

7. An apparatus according to claim 6, in which the electrodes (15, 16) are positioned passing through the tube (4).

8. An apparatus according to any of the foregoing claims, in which the injector is a manual injector (25), and the apparatus comprises a valve (24) positioned downstream of the manual injector and controlled by the unit (9) to enable/disable the flow from the injector in response to signals from the sensor (7).

9. A method for the detection and removal of bubbles of gas (11) in a flow of medical fluid emitted by an injector (2) and directed towards an infeed tube of an output device (3), characterised in that it comprises the following steps: preparation of a section of tube (4) with a first input end (5) for the fluid emitted by the injector (2) and a second output end (6) for the fluid directed towards the output device (3); detection of the passage of a bubble (11) through the tube (4); suction from the tube (4) of a defined quantity of fluid in response to the detection of the bubble (11) in order to remove the bubble (11) trapped in the quantity of fluid suctioned off.

10. A method according to claim 9, in which the fluid injected in the tube (4) is discontinued in response to the detection of a bubble (11).

11. A method according to claim 9, in which the suction is maintained for a predetermined period of time.

12. A method according to claim 10 or 11, in which the discontinuation is maintained for a predetermined period of time.

13. A method according to any of the claims from 9 to 12, in which the output device is a catheter (3).

14. A method according to claims 9 to 13, in which the inner diameter of the tube (4) is similar to the diameter of fluid output device (3).

15. A device for the detection of bubbles (11) in a flow of fluid between an injector (2) and a connection tube of a catheter (3), comprising: a section of tube (4) with hydraulic connections to the injector (2) and to the connection tube of a catheter (3), a bubble-detection sensor (7), an electronic unit (9) connected to the sensor (7) to receive a signal indicating detection of the bubble (11), electrical connections (10) from the electronic unit (9) to the injector (2) to command the injector (2) to discontinue the injection on detection of a bubble

(H), characterised in that the sensor (7) is firmly integrated with the tube (4).

16. A device according to claim 15, in which the electrical connections (10) are removable and the device is the disposable type.

17. A device according to claim 15 o 16, in which the sensor (7) is an electrical conductivity measurement sensor.

18. A device according to claim 17, in which the sensor is equipped with electrodes (15, 16) which pass through the tube (4).

19. A method for the detection of bubbles (11) in fluid flowing through connection tubes of an injector (2) to a catheter (3) by means of an electrical conductivity measurement sensor (7).