Couplings for medical cannulae

A medical coupling has male and female members (1, 2) which push fit together, and a screw cap (7) which secures the members against separation. To prevent unintentional release of the cap, locking means, such as a ratchet and pawl mechanism, are provided between the cap and female member. Au outer shell (25) can enclose the cap for providing an enclosure around the fluid connection to deter bacterial contamination. Alternatively a separate capsule can enclose the coupling for this purpose. The two members and cap are connectable by holding gripping portions which are located remotely from the parts forming the fluid connection to reduce risk of contamination. A valve system is associated with the female member for closing a flexible tube connected to this member and to displace liquid to fill the space left in this member when the male member is disconnected from it.

This invention is concerned with medical equipment, and in particular 
relates 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 can 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'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 or 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, charactered 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 female members 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.

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 can is formed with an 
extension 20 directed rearwardly from the wall 9. This extension 
constitutes a finger grip section so that both the can 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 studs 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 of 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 wailed tube 31, the forward end of which is sealed 
to the catheter tube 22, 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 48a have free forward ends and the 
slider is a collar 50a which by sliding forwardly first seals the tube 49a 
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, 48a 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 36a is trapped between the slider 33a and the 
flexible tube 31a, 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 is 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.