Patent Publication Number: US-6217564-B1

Title: Couplings for medical cannulae

Description:
This application is a division of application Ser. No. 08/687,384, filed Aug. 19, 1996 is now U.S. Pat. No. 5,830,195, which derived from PCT/GB95/00337, filed Feb. 17, 1995. 
    
    
     This invention is concerned with medical equipment, and in particular relate to couplings for connecting cannulae or catheters to a connection tube through which liquid to be administered to a patient is delivered, or fluid to be taken from a patient is collected. 
     It is generally accepted practice for a catheter tube to be equipped, at the end thereof opposite the end which is introduced into the patient, with a moulded plastic connection hub defining a tapered socket of frustoconical configuration. This hub constitutes a female coupling member for cooperation with a complementary male member fitted to the end of the connection tube, e.g. of an administration set. The male member comprises a tapered frustoconical spigot which is dimensioned to engage with a friction fit in the tapered socket of the catheter hub. Thus, the coupling is made by pushing the male and female members together, and is disconnected simply by pulling the members apart. If a coupling should become separated unintentionally, there may be very serious consequences for the patient e.g. as a result of air being drawn in through the catheter and entering the blood stream. Various proposals have been put forward for applying safety devices to hold the members of the coupling against accidental separation, but none have gained practical acceptance, except that a small rotatable cap is sometimes provided, either held captive with the male member or loosely received on the connection tube attached to it, and this cap has an internal thread which allows it to be screwed over the catheter hub by cooperation with a pair of small radial lips formed at its free end. However, this cap can become unscrewed and it is not always completely reliable, e.g. in a situation where a patient has a tendency to fiddle with equipment. Therefore, it is common practice for medical staff to wrap tape around the coupling. While tape helps to secure the coupling, it is inconvenient and has the disadvantage that the coupling is concealed from sight. 
     Another disadvantage of the conventional coupling is that the male and female members are quite small and need to be held in the fingers at or very closely to those surface portions which are contacted by fluid, when engaging and releasing the coupling. This carries with it a risk of infection as bacteria deposited on the plastic members have a tendency to colonise and the bacteria can be carried by the liquid flowing through the coupling into the patient&#39;s blood stream. Also, the patient may finger the coupling and cause bacterial contamination. 
     When the known coupling is released, for example for replacement of the administration set, there is a danger that air may enter the catheter through the open socket of the connection hub. While a device to pinch closed the catheter tube has been proposed, this does not provide a complete solution. When the male coupling member is withdrawn from the socket, there is left a space which naturally fills with air, and upon another male member being inserted into the socket it is possible for a bubble of air to become trapped within the coupling and subsequently pass through the catheter into the patient. 
     The present invention addresses the foregoing problems. 
     In accordance with one aspect the present invention resides broadly in a coupling for a medical cannula comprising two members secured against separation by a rotatably tightened part, characterized in that a locking arrangement is provided for locking said part against rotation in the loosening direction. 
     Stated more specifically the invention provides a coupling for a medical catheter, comprising separate male and female members which are connectable with a push fit, a cap for surrounding the members and rotatable for releasable engagement with one of the members to secure the members against being pulled apart, and means on said cap and said one member for locking the cap against reverse rotation. 
     In a particular embodiment, the said one member is the catheter hub and includes a peripheral surface portion provided with ratchet teeth therearound. The cap, held captive but rotatable on the male member, has an internally threaded section and projecting forwardly therefrom means carrying one or more pawls for engaging the ratchet teeth to retain the cap against rotation in a direction to release the cap. The means carrying the pawls is preferably resilient to allow for their disengagement from the ratchet teeth when authorised separation of the coupling is required. By these locking means the male and female members are positively held against unintentional disconnection and the chances of them becoming separated inadvertently are extremely remote. 
     According to a second aspect of the present invention there is provided a coupling for a medical catheter comprising separate male and female members which are connectable with a push fit, a cap for surrounding the members and rotatable for releasable engagement with one of the members to secure the members against being pulled apart, and means extending rearwardly of the cap part engageable with the one member and defining at a position remote therefrom a holding section for holding the cap during connection of the male and females and rotation of the cap for engaging said cap part with said one member. 
     The rearwardly extending means may be fastened to, e.g. be integral with the cap, or it may be a separate component, in which case it can be adjustable and define a shell or housing for enclosing the assembled male and female members, and the cap, to form a barrier against bacterial contaminations. In either case, because the coupling can be completed and secured without need to handle any parts in close proximity to the cooperating portions of the male and female members, the risk of these portions being contacted by bacteria is substantially eliminated. 
     In accordance with a third aspect of the invention there is provided a coupling for a medical catheter comprising a female member for cooperation with a male coupling member, a flexible walled tube connected to the female member, and valve means for pinching closed the tube and displacing liquid therein towards the female member for filling the volume occupied by the male member on disconnection of the male member from the female member. 
     By virtue of the valve means the liquid remaining in the catheter can be brought to fill the socket of the catheter hub and thereby risk of air passing through the catheter during and immediately after an administration set replacement operation is excluded. The valve means can take a variety of different forms and will be operated by initially closing the tube at one position followed by reducing the volume within the tube on the upstream side of this position. 
     Provided in accordance with a fourth aspect of the invention there is a coupling for a medical catheter comprising two separate members releasably engageable with each other, and a capsule for defining a substantially sealed enclosure around the engaged coupling members for excluding bacteria from contact therewith. 
     The capsule conveniently comprises two parts, e.g. connected by an integral hinge, adapted to engage with a snap fit when applied over the coupled members, and can be capable of being opened only by destruction to thwart any attempt to re-use a capsule which may have become contaminated. 
    
    
     A better understanding of the invention and its several aspects will b gained from the detailed description which follows, reference being made to the accompanying drawings in which: 
     FIG. 1 is a partly sectioned side elevation of a coupling embodying the invention; 
     FIG. 2 is a transverse cross section taken along the line II—II in FIG. 1; 
     FIG. 3 is a view similar to FIG. 1 showing a modified coupling; 
     FIG. 4 is a partly sectioned side elevation of another coupling in accordance with the invention; 
     FIG. 5 is a transverse cross section taken along the line V—V in FIG. 4; 
     FIG. 6 shows the coupling of FIG. 4 in fully connected condition; 
     FIG. 7 is a view similar to FIG. 4 illustrating a modified coupling; 
     FIG. 8 is a perspective sketch showing the principles of the modified construction; 
     FIG. 9 shows an embodiment of a valve mechanism for the female member of a coupling; 
     FIG. 10 is a transverse section taken along the line X—X of FIG. 9; 
     FIG. 11 is a partially cut away scrap view of the member shown in FIG. 9; 
     FIG. 12 is a schematic side view of another valve device; 
     FIG. 13 is a section taken along the line XIII—XIII of FIG. 12; 
     FIG. 14 is a plan view of the device of FIG. 12; 
     FIG. 15 shows another form of valve device; 
     FIG. 16 is a longitudinal section through a further female member with a valve device; 
     FIG. 17 is a perspective view of the member of FIG. 16; 
     FIG. 18 is a schematic perspective view of an assembly of couplings and associated valves within a common case; 
     FIG. 19 is a transverse section through another valve device; 
     FIG. 20 is a sketch illustrating the mode of operation of the FIG. 19 device; 
     FIG. 21 is a perspective view of a capsule enclosing a coupling according to the invention; 
     FIG. 22 is a perspective view of another capsule; 
     FIG. 23 illustrates a form of seal which may be incorporated in the capsules; 
     FIG. 24 is a partial perspective illustration of another capsule; 
     FIG. 25 shows in open condition another capsule according to the invention; 
     FIG. 26 shows in perspective another embodiment of a capsule; and 
     FIG. 27 shows the capsule of FIG. 26 in end elevation. 
    
    
     The coupling assembly illustrated in FIG. 1 comprises a female member  1  in the form of a rigid plastics moulding fixed to the trailing end of a catheter tube (not shown), and a male member  2  attached to a connection tube  3 , e.g. leading from a fluid container. The female member includes a part  4  defining a tapered socket into which a complementary spigot  5  of the male member is engaged and sealed with a friction push-fit. At the socket mouth the part  4  is provided with a pair of opposed radially directed lips  6  for engagement by a cap  7  which has a cylindrical part provided with an internal screw thread  8  to enable the cap to be screwed onto the part  4  by cooperation of the lips  6  with the thread. The cap has an end wall  9  with a central hole through which the male member  2  passes with a clearance allowing rotation of the cap relative to the male member  2 . The end wall  9  abuts a flange  10  formed on member  2  and can be held captive by a further projection  11  on the member  2 , although this is not essential. As so far described the coupling is of a construction in practical use and generally known as a “Luer Lock”. 
     In accordance with the present invention the female member includes a locking section  12  located between the part  4  and a holding part  13  for gripping the member when connecting and disconnecting the coupling. The section  12  has longitudinal ratchet teeth  14  around its periphery as clearly shown in FIG.  2 . Carried by the cap and attached to the cylindrical part by integral strips  15  or a flexible skirt is an elliptical collar  16  having inwardly directed pawls  17  positioned opposite one another on the smallest diameter of the ellipse. The collar is resilient and the pawls  17  engage the ratchet teeth  14  to allow rotation of the cap about the member  1  in the direction (counterclockwise as seen in FIG. 2) corresponding to forward screwing movement of the cap onto the part  4 , and to prevent reverse rotation, i.e. in a direction to disengage the cap from part  4 . However, by squeezing the collar in the direction of the greatest diameter of the ellipse, the pawls can be disengaged to permit such reverse rotation and hence release of the cap to allow disconnection of the male and female members. From the foregoing description it will be understood the coupling is made by pushing the spigot  5  into the socket of part  4 , advancing the cap  7  to bring the thread  8  into cooperation with the lips  6 , and the pawls  17  into cooperation with the ratchet teeth  14 , and screwing the cap onto the part  4  of the female member. During this action the pawls, due to their shape, ride over the ratchet teeth, but when the cap is fully screwed on the engagement of the pawls  17  with the ratchet teeth prevents the cap unscrewing inadvertently. To disconnect the coupling the collar  16  is squeezed as described above and turned to unscrew the cap before the members  1 ,  2  are pulled apart. 
     FIG. 3 shows a modified embodiment wherein the cap is formed with an extension  20  directed rearwardly from the wall  9 . This extension constitutes a finger grip section so that both the cap and the female member can be held at locations remote from the spigot  5  and socket part  4 , which form the fluid conducting joint between the members, during their connection, and hence risk of contamination by bacteria is reduced. The coupling is otherwise as described above in relation to FIGS. 1 and 2. 
     An alternative coupling assembly also embodying the invention is shown in FIGS. 4 to  6 . The male and female members in this embodiment are essentially the same as in the embodiment of FIG. 1, as is the cap  7  except that the pawls  17  are carried at the free ends of resilient arms  22  extending forwardly from the cylindrical cap part. The arms are arranged normally to bias the pawls out of engagement with the ratchet teeth  14  as depicted in FIG.  4 . An outer housing member or shell  25  is slidably mounted over the male member  2  and includes a forwardly directed cylindrical skirt  26  which surrounds the cap  7  and spigot  5 . On the inside of the skirt are longitudinal grooves  27  defining keyways for key elements in the form of radial projections or stud  28  on the cylindrical part of the cap. Thus, the shell  25  is fast for rotation with the cap  7 , but is longitudinally displaceable relative thereto. The trailing end of the shell includes a finger grip portion for holding the male member during connection of the assembly. The spigot  5  is inserted into the socket and the cap  7  is screwed onto the part  4  by rotating the shell and hence the cap relative to the female part  1 . During this engagement the pawls  17  are held free of the ratchet teeth. The shell is then displaced forwardly to press the arms  22  inwardly and thereby engage the pawls with the ratchet teeth to lock the shell and cap against rotation in the direction to release the cap, and to bring the leading end of the shell into cooperation with the part  13  of the female member. As shown the part  13  has an annular groove for receiving the end of the shell. In this closed position, as shown in FIG. 6, the shell and part  13  define an enclosure surrounding completely the parts forming the fluid connection to deter bacterial contamination these parts. By the end of the shell engaging in the groove in the female member there is formed a labyrinth type seal between these parts. If required a detent means could be provided to retain the shell in its closed position. The inner surface of the shell preferably includes an annular groove  29  at the inner end of the keyway grooves  27 , the studs  28  being located in this groove when the shell is closed so that the shell can rotate freely in this axial position. It will be understood the shell must be retracted to the position shown in FIG. 4, to release the pawls from the ratchet teeth, before the cap can be unscrewed to release the coupling. 
     In this embodiment it is not essential for the teeth and pawls to form a ratchet mechanism as they are not engaged until the cap has been screwed home. Thus, the locking section  12  could have longitudinal splines with which the pawls engage to prevent rotation of the cap in either direction. 
     Other arrangements for interengaging the shell and cap are possible while retaining essentially the same principles of operation. Thus, in FIGS. 7 and 8 there is shown a construction in which a longitudinal rib  30  is formed on the inside of the shell and the cap has a dog  31  on its rear wall as well as a longitudinal groove  32 . The rib  30  engages the dog  31  for rotating the cap to screw it onto the female member, after which the shell  25  is turned back to align the rib  30  with the groove  32  to allow the shell to be advanced to its closed position. 
     The forward end of the female member  1  has not been illustrated in FIGS. 1 to  8 , but it is preferably provided with a valve device as described below. 
     The female member  1  shown in FIG. 9 extends forwardly to define a channel section  30  of generally rectangular configuration. In the channel is accommodated a flexible walled tube  31 , the forward end of which is sealed to the catheter tube  32 , and the rear end of which is sealed in a counterbore leading into the socket of part  4 . Mounted on the channel section  30  is a slider  33  the down-turned sides of which have inturned lips which are received in longitudinal grooves provided in the external surfaces of the channel side walls. A pair of laterally spaced lugs  34  on the slider project downwardly into the channel on either side of the tube  31 , and are provided with slots through which an axle pin  35  carrying a roller  36  passes. The ends of the pin engage in parallel grooves formed on the inside surfaces of the channel side walls and having upper forward sections  37 , medial ramp section  38 , and lower rear sections  39 . In a forward position of the slider, the roller  36  is supported above the tube  31  which permits unrestricted flow through the tube. When the slider is displaced rearwardly, the pin  35  is driven down into the channel by the ramp sections  38  and causes the roller  36  to pinch the tube closed. At this time the male member will be released from the female member there being no danger of air passing through the catheter or fluid escaping. Further displacement of the slider will cause the pin to move along the lower sections  39  of the grooves, and the roller to move along the tube  31  to displace rearwardly the liquid therein behind the sealing point so that the vacated socket becomes completely filled with the liquid and hence there is no danger of air being trapped in the socket when another male member is connected to the female member. When such connection has been made the slider is moved back to its forward position to re-open the tube and allow liquid to flow once more. 
     Other forms of valve which will first seal to interrupt flow and then force liquid back so that the liquid meniscus in the socket is displaced to the socket mouth are possible. In the alternative of FIGS. 12-14, a slider  40  is arranged to act on an elongate member  41  and during rearward displacement it firstly presses a projection  42  down to seal the underlying tube  43 , after which it presses down another projection  44  on the member  41  to compress the tube behind the initial sealing position and hence displace the liquid meniscus  45  from the position shown in FIG. 12 to that shown in FIG.  14 . 
     FIG. 15 illustrates an embodiment in which a pair of opposed resilient arms  48  are positioned on opposite sides of the flexible tube  49 . The outer surfaces of these arms define cam faces for cooperation with the slider  50  and the inner surfaces of the arms are shaped to pinch the tube closed and then displace the liquid towards the socket, as described above, when the slider is moved rearwardly from the forward position. 
     The embodiment of FIGS. 16 and 17 is generally similar to that of FIG. 15, but in this case the resilient arms  48   a  have free forward ends and the slider is a collar  50   a  which by sliding forwardly first seals the tube  49   a  and then causes liquid to be displaced rearwardly behind the sealing point. The slider is guided by longitudinal grooves  51  with inclined bottom surfaces, and lateral notches  52  may be provided at the end of the grooves to enable the collar to be locked in the end position by rotating it. 
     It is not essential to have a slider or other device for operating the valve and the spring arms  48 ,  48   a  could instead be arranged to be pinched together such as between the thumb and forefinger. 
     A group of three couplings arranged in parallel for delivery of liquid from three separate sources to a common catheter tube is shown in FIG.  18 . The couplings and their associated valves are housed in a casing  60  provided with a sliding cover  61 . The valves may be operated by their respective sliders  63  to control the supply of respective liquids to the catheter as well as during disconnection of the male coupling members, e.g. during connection of fresh liquid supplies. 
     FIGS. 19 and 20 show a valve system similar in fundamental respects to that of FIGS. 9-11. A ball  36   a  is trapped between the slider  33   a  and the flexible tube  31   a , and the slider has a ramp surface so that when the slider is displaced rearwardly, the ball rolls along the ramp surface and presses down on the tube to pinch it closed. As the slider continues to move, the ball is carried along with it and displaced the liquid in the tube behind the initial sealing position to move back the meniscus. 
     To further assist in maintaining sterility and/or preventing unintentional disconnection, the fluid coupling of the invention and as described above is provided with a capsule within which it is cocooned. The capsule shown in FIG. 21 is made in two halves  80  connected by an integral hinge  81 , e.g. by vacuum forming. The capsule halves have peripheral surfaces which are fixed together and sealed by impact adhesive. Relatively displaced tongues  82  are provided for breaking the capsule open when access to the enclosed coupling is required. 
     The capsule of FIG. 22 if of rigid construction and has two parts  84 , either separate or hinged, which are fixed together with a snap connection. For breaking the capsule open a key  85  is inserted into the slot  86  and twisted. The interior of the capsule is shaped around the key slot and at tube openings to define serpentine paths or labyrinth type seals to deter entry of bacterial and other contaminants. Such a seal arrangement is illustrated in FIG. 23, the capsule or a member inserted therein being provided with elements to define a series of spaced discs  85  around a tube to form the serpentine pathway. 
     FIG. 24 illustrates a modification wherein the capsule halves have partition walls  90  which combine to form a disc around a tube entry opening, one partition wall being slotted and the other having location lugs  92  for ensuring correct alignment of these walls. The partition walls  90  confine with end wall elements  94  a space which may accommodate a sealing material, or sealing inserts such as a member shaped to form spaced discs as in FIG.  23 . One half of the capsule has a snap latch  96  along its free longitudinal edge for engaging the corresponding edges of the other capsule half to secure the two halves in the closed condition. 
     In FIG. 25 there is illustrated a capsule for use with a coupling which does not have a valve device enabling fluid flow to be closed off. The capsule is adapted to accommodate two couplings  100 . As in the previous embodiments it has two parts  102  connected by a hinge  103 . By means of a Y connector  104 , the two couplings lead to a common tube  105  for delivering liquid thereto supplied from respective sources. Formed within one capsule part is a barrier  106  which defines two narrow slots  107  and two larger openings  108 . When a tube is pressed into a narrow slot it is pinched closed to interrupt flow of liquid from the associated supply, but when it is located in a large opening  108  it allows free flow of liquid therethrough. Thus, merely by appropriate positioning of the tubes it can be determined that either, both or neither fluid supplies will be in fluid communication with the tube  105 . The second capsule half has a transverse rail  109  for holding the tubes in their enquired positions in the slots  107 ,  108 . In this embodiment it is preferred that the capsule be capable of being repeatedly opened and closed. Although not shown, the capsule is preferably provided with means for sealing around the tubes passing into and out of the capsule, e.g. as described above. 
     The capsule shown in FIGS. 26 and 27 is adapted for one time use, the two halves  110  being attached by an integral hinge  112  and having a snap lock mechanism  114  to fasten them securely in the closed condition. 
     So that the capsule may be opened to gain access to the coupling cocooned within it, a tear strip  116  with a tab  117  is provided. When this strip is torn away, the hinge is destroyed allowing the two halves to be separated. Once the tear strip  116  has been removed, the capsule is incapable of being reclosed and resealed without its intended method of use being abused.