Couplings for medical cannulae

Details Couplings for medical cannulae Couplings for medical cannulae

1998-08-07

2001-04-17

Yasko, John D. (Department: 3734)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S111000, C604S905000

Reexamination Certificate

active

06217564

ABSTRACT:

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'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.


REFERENCES:
patent: 4432759 (1984-02-01), Gross et al.
patent: 4473369 (1984-09-01), Lueders et al.
patent: 4631056 (1986-12-01), Dye
patent: 5531695 (1996-07-01), Swisher

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