Abstract:
The invention relates to a device for injecting liquid, comprising a piece of tubing on which there is situated at least a first liquid occlusion system. According to the invention, a regulation system ( 4 ) is situated upstream from the first occlusion system, the two systems defining an intermediate segment in which the pressure, in the absence of injection, is greater than the pressure that exists downstream from the first occlusion system so as to direct any leak of liquid from the first occlusion system downstream. The invention is applicable to a pump used for injecting contrast liquid for medical imaging.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims the benefit of and is a divisional of co-pending U.S. patent application Ser. No. 09/331,350, filed on Jun. 17, 1999, which is a national phase application of PCT/FR97/02341, filed Dec. 18, 1997, which claims priority from FR 96/15551, filed Dec. 18, 1996. 
     
    
     
       BACKGROUND OF INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a medical device for injecting liquid.  
           [0004]    An application for such a device can lie, for example, with a pump used for injecting contrast liquid for medical imaging.  
           [0005]    2. Discussion of Related Art  
           [0006]    A major problem that results from injecting liquid into patients lies in the risk of the injection device being contaminated by the patient. When a liquid is administered to a patient, there is a risk of the injected liquid flowing back after it has already come into contact with the patient. Also, in the absence of injection, there still exists a risk of contamination by contaminating agents, such as germs, migrating from the patient to the injection device. As a general rule, this situation makes it essential, when treating a new patient, to change all of the portions of the device that have already been used.  
           [0007]    There exist several devices in the prior art for reducing the risk of such backflow: EP-A-64853 in the name of MEDEX S. A. describes an injection unit that includes a non-return valve, for example. EP-A-279028 in the names of KABI PHARMACIA GmbH and PFRIMMER-VIGGO GmbH claims a liquid injection device having a non-return valve characterized by the fact that the opening pressure can be set to either of two positions.  
           [0008]    Although prior art devices do indeed reduce the risk of backflow, there still remains the risk of the non-return valve leaking. This risk is particularly high in the absence of injection.  
         SUMMARY OF INVENTION  
         [0009]    The present invention thus seeks totally to eliminate any risk of backflow. In addition, the present invention also seeks to make it possible to detect any leak through the safety means that are installed to avoid such backflow, assuming such backflow might indeed take place.  
           [0010]    To this end, use is made of a device for injecting liquid, the device comprising a piece of tubing on which there is situated at least a first liquid occlusion system such as a non-return valve. In addition, a regulation system is situated upstream from the first occlusion system, the two systems defining an intermediate segment in which the pressure, in the absence of injection, is greater than the pressure that exists downstream from the first occlusion system. In this way, any leak of liquid at the first occlusion system is directed downstream and any leak from the intermediate segment can be detected by measuring the associated pressure drop.  
           [0011]    The terms “downstream” and “upstream” mean respectively towards the patient and in the opposite direction.  
           [0012]    By way of example, the regulation system can be a second non-return valve or a system for flattening the tubing, such as the wheels of the peristaltic cassette corresponding to patent FR 89/03234 in the name of MALBEC S. A.  
           [0013]    It should be observed that the regulation system cannot be considered merely as constituting a safety system in addition to and independent of the first occlusion system.  
           [0014]    On the contrary, the two systems together constitute an interactive assembly since the presence of the regulation system makes it possible to set up, and optionally to maintain, a positive pressure difference between the two systems to prevent any leakage of liquid located downstream from the first occlusion system from flowing upstream towards the intermediate segment.  
           [0015]    It should also be observed that the pressure difference between the two systems is constant in the absence of a leak since the space between the two systems is filled with liquid which, like any other liquid, is incompressible.  
           [0016]    In order to increase the safety of the device, it is also desirable to have systems of different kinds. As a result, if one system should fail, the other can nevertheless continue to act, in a manner similar to that described in the prior art.  
           [0017]    Furthermore, when using systems of different kinds, and more precisely systems characterized by the fact that each of them has a different opening pressure, it is possible to direct the flow direction of the liquid in the event of a leak or high pressure in the intermediate segment.  
           [0018]    In particular, if the opening pressure of the first occlusion system is less than the opening pressure of the regulation system, any liquid movement during an interruption of injection will take place downstream, the regulation system closing before the first occlusion system, thereby avoiding any contamination of the portions of the device situated upstream from the first occlusion system.  
           [0019]    Similarly, in the event of high pressure in the intermediate segment, the first occlusion system will be the first to open in the event of a leak, thereby causing the liquid to go downstream from the first occlusion system and thus preventing any backflow towards the intermediate segment.  
           [0020]    It is also possible to envisage that the two opening pressures of the regulation systems are identical, however that can only be envisaged if the opening pressure is greater than the pressure that exists downstream from the first occlusion system when there is no injection.  
           [0021]    In addition, it is desirable to have an opening pressure for the first occlusion system which is greater than the maximum pressure that can be set up downstream therefore because of the patient in the absence of injection. Also, in the absence of injection, it is necessary for the opening pressure of the first occlusion system to be greater than the pressure of the intermediate segment.  
           [0022]    In most cases, in the absence of injection, the pressure that exists downstream from the first occlusion system corresponds to the venous pressure of the patient.  
           [0023]    In another preferred embodiment, it is desirable to provide the tubing with a disconnection system situated between the two regulation systems. The disconnection system marks the boundary between a downstream tubing for single use only and an upstream tubing for multiple use.  
           [0024]    Thus, when the tubing is contaminated only downstream from the disconnection system, it is possible to change only that portion of the device while reusing the remainder thereof (pumping system, peristaltic cassette, reservoir, etc.) with other patients.  
           [0025]    The disconnection system is preferably situated as close as possible to the second regulation device or, which comes to the same thing, as far as possible from the non-return valve. Thus, in the highly improbable event of contamination propagating upstream, the risk of contaminating the zone situated upstream from the disconnection system is minimized since the path to be followed to reach the disconnection system is as long as possible.  
           [0026]    In another preferred embodiment, the disconnection system is provided with occlusion means for the tubing which are activated prior to disconnection, thereby avoiding any risk of liquid being ejected from the tubing which is under pressure. Such an automatic closure system is described, for example, in U.S. patents U.S. Pat. No. 5,549,566 and U.S. Pat. No. 5,533,996 in the names of ABBOTT LAB and BAXTER INT. INC., respectively.  
           [0027]    The above-mentioned occlusion means can also be designed so as to open during connection.  
           [0028]    By way of example, such disconnection systems can be of the “luer-lock” type coupled to a rotary cock system on each of the two connected segments. In addition, the connection system between the two pieces can be of the key and lock type, thus allowing interconnection to take place only between two elements that are properly encoded relative to each other. Such a rotary system makes it possible to open and close the two cocks placed on either side of the connection when the key is turned in the lock, while preventing the two pieces from being disconnected when the key is engaged in the position corresponding to the open position of the occlusion systems.  
           [0029]    The occlusion system situated in the downstream segment can also be a non-return valve, and the system in the upstream segment can be a check valve that is open when the two pieces are engaged or, alternatively, the two occlusion systems can be check valves that are open only when the two pieces are engaged.  
           [0030]    In another preferred embodiment, a pressure sensor is situated on the intermediate segment. As a result, it is possible to detect any pressure variation in this zone.  
           [0031]    When the pressure sensor comes back into contact with the tubing, it is advantageous to place it between the disconnection system and the regulation system; this configuration has the merit of making it possible to reuse the same pressure sensor configuration for a plurality of patients.  
           [0032]    In the absence of injection, any pressure drop between the two systems implies that a leak is present which, very likely, might have taken place in the first occlusion system or in the regulation system.  
           [0033]    If the leak has taken place in the first occlusion system, then contamination can propagate into the tubing for multiple use.  
           [0034]    If the leak has taken place in the regulation system, then contamination has not necessarily propagated into the tubing for multiple use, but the risk of that happening has nevertheless been increased since any leak at the first occlusion system gives rise to a drop in pressure in the intermediate segment, thus eliminating the effect of the means installed in the context of the present invention.  
           [0035]    In order to mitigate the two above-described situations, it is advantageous to associate an alarm  102  with the pressure sensor placed on the intermediate segment. Furthermore, in even more advantageous manner, liquid injection can be triggered as to reestablish the initial pressure when the alarm is activated.  
           [0036]    It should also be observed that maintaining a high pressure in the intermediate segment, close to the pressure for opening the first occlusion system, can serve to favor leakage at said first occlusion system.  
           [0037]    To this end, means are provided to reduce the pressure in the intermediate segment. These means can be constituted by an intermediate chamber of adjustable volume. By way of example, the volume of the intermediate chamber can be adjusted by a piston. Thus, the pressure which exists in the intermediate segment can be selected so as to be greater than the pressure downstream from the first occlusion system and far enough away from the opening pressure of said first occlusion system to make full use of the sealing characteristics of said first occlusion system. Another means enabling said pressure to be lowered below the opening threshold of the first occlusion system consists in selecting a regulation system whose opening can be adjusted in such a manner as to lower the pressure of the intermediate segment to a predetermined value.  
           [0038]    Although adjusting the pressure in the intermediate segment considerably reduces any risk of contamination, it is still possible after an alarm is triggered to change the portions that might have been contaminated, for example portions such as the peristaltic cassette. Under such circumstances, it is advantageous for this purpose to provide a second disconnection system upstream from the regulation system.  
           [0039]    Optionally, a second pressure sensor can be placed on the segment of tubing which is to be found downstream from the first occlusion system, thus making it possible, for example, to detect any excess pressure compared with the pressure in the intermediate segment.  
           [0040]    It is also possible to provide the device with a system for measuring the pressure difference as measured by the two sensors, thus having the advantage of determining the risk of backflow more directly. An alarm can be triggered when the pressures situated upstream and downstream of the non-return valve are tending to become equal.  
           [0041]    The medical device of the invention can also be designed in such a manner as to deactivate the alarm when the single-use tubing is disconnected.  
           [0042]    The medical device of the invention may advantageously include a syringe driver  100 . A pressure sensor  108  can be placed on the distal end of the piston  106  of the syringe driver.  
           [0043]    Assuming that a syringe driver  100  is used, it is possible to consider the syringe  104  itself as being an integral portion of the intermediate segment, and the syringe itself can form the regulation system. In addition, under these circumstances, the syringe  104  can also act as a system for regulating the intermediate chamber so as to enable the pressure in the intermediate chamber to be adjusted.  
           [0044]    The medical device of the invention can be used with any type of liquid, and in particular it can be used for injecting contrast liquids. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0045]    The invention is described below by way of an example and with reference to the accompanying drawings, in which:  
         [0046]    [0046]FIG. 1A is a diagram showing a preferred embodiment of the invention;  
         [0047]    [0047]FIG. 1B is a diagram showing an alternative embodiment of the invention;  
         [0048]    [0048]FIGS. 2A to  2 I show various steps in the operation of a preferred disconnection system in its first use;  
         [0049]    FIGS.  2 ′A and  2 ′B correspond to the steps of FIGS. 2A and 2B when the disconnection system is used on subsequent occasions;  
         [0050]    [0050]FIG. 3 is a longitudinal section of a preferred embodiment of a non-return valve; and  
         [0051]    [0051]FIGS. 4 and 5 are perspective views of the disconnection system of FIGS. 2A to  2 I,  2 ′A, and  2 ′B, respectively before and after connection to a liquid injection device, downstream from a peristaltic cassette. 
     
    
     DETAILED DESCRIPTION  
       [0052]    The liquid injection device in one embodiment (FIG. 1A) is constituted essentially by a piece of tubing, a reservoir  1 , a pump system  2 , an intermediate chamber  3  of variable volume, a regulation system  4  which may include the wheels of a peristaltic pump, and a non-return valve  7 . A disconnection system  6  is situated upstream from the non-return valve  7 , between said valve and the regulation system. Pressure sensors  5  and  8  are situated downstream and upstream from the non-return valve.  
         [0053]    In the absence of injection, i.e. when the pump is deactivated, constant pressure exists between the non-return valve and the second regulation system. The constant pressure is lower than the opening pressure of the non-return valve.  
         [0054]    If the non-return valve is defective, backflow of liquid towards the pump is prevented by the flow of liquid associated with the pressure that exists in the intermediate segment, with this pressure in the intermediate segment being due to the presence of the peristaltic cassette which, in the absence of injection, is very effective at occluding the tubing. The opening pressure of the occlusion system constituted by the wheels of the peristaltic cassette is greater than 8 bars, whereas the opening pressure of the first occlusion system is equal to 0.5 bars.  
         [0055]    The present invention is naturally not limited solely to the example described above, with all configurations of the description also being included.  
         [0056]    Thus, and preferably, the first occlusion system, or the regulation system, or both of them, are of the automatic clamp type. It is also possible to use a fourth occlusion device, preferably located downstream from the disconnection system, which device is activated in the event of an alarm being triggered.  
         [0057]    The device of the present invention can also include a pressure sensor measuring the pressure of the liquid in a length of tubing situated upstream from the intermediate segment.  
         [0058]    With reference to FIG. 2A, a preferred disconnection system  6  comprises an upstream piece  10  having an intermediate chamber  12  of adjustable volume, and a downstream piece  14  provided with the non-return valve  7  and capable of co-operating in reversible manner with the upstream piece  10  so as to form a sealed link.  
         [0059]    The upstream piece  10  is constituted by a hollow tubular body  15  that is open at both ends, defining an inside volume that is split into two by an open internal radial wall  16  placed between an injection chamber  18  and the intermediate chamber  12  of adjustable volume, constituting a decompression chamber as explained below.  
         [0060]    The intermediate chamber  12  contains a pre-split resilient septum  20  whose diameter is substantially equal to the inside diameter of the intermediate chamber  12  so as to form a piston that is movable in translation.  
         [0061]    The downstream piece  14  comprises a hollow circularly-symmetrical body  22  that is extended at its two open ends by respective hollow rods. The body  22  surrounds an inside volume which is split in two by an open radial wall  24  placed between a first chamber  26  in which the non-return valve  7  is formed, and a second chamber  28  facing towards the patient.  
         [0062]    The hollow rod  30  adjacent to the first chamber  26  has a free end whose shape includes a frustoconical portion, and it is designed to be placed inside the intermediate chamber  12  by passing through the septum  20  and the opening of the wall  16 . The hollow rod  30  has an outer annular collar  32  that comes into abutment against the septum  20  so as to drive it in translation inside the intermediate chamber  12  (FIG. 2B), the septum  20  coming into abutment against the wall  16  when the rod  30  is pushed home fully into the piece  10 , the tubular body  15  then coming into abutment against the body  22  (FIG. 2C).  
         [0063]    Locking means are also provided between the pieces  10  and  14 , e.g. in the form of a resilient locking tab situated outside the body  15  and having a free end that snap-fastens against a shoulder or a groove in the outside surface of the body  22 . Such a tab  34  is shown in FIG. 2B in association with a shoulder that faces in the opposite direction to the hollow rod  30  when the bodies  15  and  22  are in abutment.  
         [0064]    A non-return valve  7  shown is formed by a plug  38  that is capable of being compressed (collapsing) radially enabling it to be bypassed by the liquid when the pressure of the liquid upstream from the plug  38  is greater than or equal to the opening pressure of the non-return valve  7 .  
         [0065]    This type of plug is preferably as described in U.S. Pat. No. 4,929,230, i.e. a plug made of resilient material of longitudinal section that can be seen in FIGS. 2A to  21  and  2 ′A,  2 ′B, and even more clearly in FIG. 3. The plug  38  has a first end directed towards the second chamber  28  with sealing means  46  that co-operate with the inside surface of the second chamber  28 , a second end directed towards the hollow rod  30 , at least one frustoconical surface portion  40  between the sealing means and the second end, and a cavity  42  extending inside said plug said first end and over a depth that is greater than the distance between the sealing means and the free edge of the first end. This plug  38  also has a retractable wall  44  between at least a portion of said frustoconical surface  40  and said cavity  42 , said retractable wall  44  extending at least from the end of said cavity  42  as far as first end and retracting into said cavity  42  when the radial resultant of the pressure exerted on said frustoconical surface  40  by said liquid is greater than the sum of the radial compression strength of the retractable wall  44  plus the internal pressure of the cavity  42 .  
         [0066]    This type of plug  38  can also be placed in the tubing as a second occlusion system  4 .  
         [0067]    In a preferred embodiment, the opening pressure of the non-return valve  7  is greater than its closing pressure. By way of example, the plug  38  can be shaped so that it is compressed, thereby opening the valve  7 , starting from a pressure of 1.2 bars for the liquid in the hollow rod  30 , the retractable wall  44  returning to its initial shape and thus closing the valve  7  when the pressure of the liquid in the hollow rod is equal to or less than 0.8 bars.  
         [0068]    Prior to any injection (FIGS. 2A and 2B) the pieces  10  and  14  of the connection system  6  are empty of liquid, i.e. they have atmospheric pressure (Pa) within them.  
         [0069]    In general, throughout the description below, when said atmospheric pressure Pa is not mentioned, it should be assumed that it is to be added to the liquid pressure mentioned.  
         [0070]    After the pieces  10  and  14  have been connected together, the injection device is primed (FIG. 2C) by sending liquid at a pressure greater than 1.2 bars (P&gt;1.2) into the injection chamber  18 . This liquid passes along the hollow rod  30 , the septum  20  closing the intermediate chamber  12  in sealed manner, which chamber presents substantially zero volume in communication with the injection chamber  18 . Because of this pressure of 1.2 bars which is greater than the opening pressure of the valve  7 , the valve is opened and the liquid can pass through the first chamber  26  and leave the second chamber  28  in communication with the outside (Pa).  
         [0071]    The following step (FIG. 2D) consists in stopping the delivery of liquid under pressure, the injection chamber  18  then being filled with a liquid at a pressure of about 0.8 bars (P0.8) causing the valve  7  to close by virtue of the retractable wall  44  returning to its initial position.  
         [0072]    Once the valve  7  has closed, the injection device is connected to the patient so that the patient&#39;s venous pressure which is close to 0.2 bars (P0.2) corresponds substantially to the pressure of the liquid in the second chamber  28 .  
         [0073]    During injection (FIG. 2E), the pressure of the liquid in the disconnection system  6  is greater than 1.2 bars (P8), thereby holding the valve  7  open.  
         [0074]    Once injection is over (FIG. 2F) the situation of the disconnection system  6  is identical to its situation (FIG. 2D) preceding the injection step (FIG. 2E).  
         [0075]    When the patient is disconnected (FIG. 2G) from the injection device, the valve  7  remains closed, since the pressure of the liquid in the second chamber  28  is substantially zero (ignoring atmospheric pressure) and the pressure of the liquid in the injection chamber  18  is substantially of the order of 0.8 bars.  
         [0076]    Thus, when the pieces  10  and  14  of the disconnection system  6  are moved apart (FIG. 2H), as the hollow rod  30  is withdrawn and the collar  32  moves away from the wall  16 , the septum  20  also moves away from the wall  16  since the liquid pressure in the injection chamber  18  is greater than the pressure inside the second chamber  28 .  
         [0077]    The volume of the chambers  12  and  18  is designed to enable the septum  20  to move far enough away from the wall  16  to enable the pressure in the chambers  12  and  18  to drop to the level of atmospheric pressure so that the two pieces  10  and  14  can be separated (FIG. 21) without any risk of liquid flowing out from the second chamber  28  or from the hollow rod  30 . It will be understood that the internal volume of said upstream piece  18  is shaped so as to make it possible to obtain liquid pressure in the disconnection system  6  which is less than or equal to atmospheric pressure prior to said upstream and downstream pieces  10  and  14  being separated fully.  
         [0078]    Because of this disconnection system, the plug  38  prevents the liquid that has filled the second chamber  28  and that has been in communication with the tubing connected to the patient from flowing back upstream. In addition, any outflow of liquid is avoided when the pieces  10  and  14  are disconnected.  
         [0079]    When the injection device is used on a new patient, a new downstream piece  14 ′ is used which is connected to the upstream piece  10  that has already been used on a preceding patient (FIGS.  2 ′A and  2 ′B). The subsequent steps in performing injection are identical to the steps illustrated by FIGS. 2C to  21  as already described.