GB2331339A

GB2331339A - Epidural connector

Info

Publication number: GB2331339A
Application number: GB9822585A
Authority: GB
Inventors: David Anthony Pinto
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 1997-11-14
Filing date: 1998-10-19
Publication date: 1999-05-19
Anticipated expiration: 2018-10-19
Also published as: GB2331339B; GB9724127D0; GB9822585D0

Abstract

The connector 1 has a compressible slug 30 of e.g. hexagonal outer shape located within a housing 10 of circular section and adjacent a shoulder 15 at the forward end of the housing which has an opening 16 through which an epidural cannula 2 extends into a bore 31 through the slug 30. A rear part 12 of the connector has a female bore 23 to receive the nose 4 of a syringe by which fluid is dispensed to the cannula 2 the rear part 12 being screwed into the housing to compress the slug 30 about the cannula. A first steel washer 36 is located between one end of the slug 30 and the shoulder 15 in the housing, and a second washer 35 is located between the other end of the slug and the end 18 of the rear part 12 and enable free rotation of the rear part 12 and the housing 10 relative to the slug 30, thereby reducing twisting of the slug.

Description

2331339 CONNECTORS This invention relates to connectors.

The invention is more particularly concerned with connectors for connection to the outside of tubes, such as epidural cannulae, and to assemblies including such connectors.

Known epidural cannula connectors have a resilient slug with a bore through which the epidural cannula extends. The slug is located between two halves of a housing that are screw threaded with one another. When the two halves of the housing are tightened, they compress the slug axially, thereby causing it to expand radially inwards and outwards. A washer may be located between one end of the slug and one half of the housing. The outer surface of the slug engages the inside of the housing and the bore through the slug is squeezed into sealing engagement with the cannula. One half of the housing has a female luer coupling, or other coupling, to which a cooperating connector can be mated. Examples of such connectors are described in US 4,187,848, GB2285294, Brit J. Anaesth (1964) 36, pp 740, 741 and Brit J. Anaesth (1961), 33, pp 664, 665. Epidural connectors are available, such as from SIMS Portex Limited of Hythe, Kent, England under reference number 100/382.

One problem with these connectors is that, if they are over-tightened, there is a risk of crushing the cannula because of its small diameter, typically about I mm. The problem is aggravated if the connector is to be used with cannulae of different diameters since the slug of the connector must be capable of sealing with the smallest of the cannulae and retaining it against tensile loads, thereby increasing the risk of crushing the larger cannulae. The connector described in GB2285294 reduces these problems by using a slug with a hexagonal section. The hexagonal shape of the slug, however, reduces its torsional rigidity slightly and can make it more prone to twisting if overtightened. The use of a washer at one end of the slug does not entirely prevent such twisting.

It is an object of the present invention to provide an improved connector.

According to one aspect of the present invention there is provided a connector for connection to an epidural cannula, the connector having a compressible member with a bore therethrough sized to receive the cannula, a housing having a first tubular part in which the compressible member is located, the first part having a contact region at one end for engagement with one end of the compressible member, a second part screw threaded relative to the first part, the second part having a contact region for engagement with the other end of the compressible member such that, when the first and second parts are rotated relative to one another the compressible member is compressed axially between the contact regions causing it to expand radially into contact with the internal surface of the first part and to seal about the cannula, the connector having two washers, and one washer being located between the compressible member and each respective contact region such that both the contact regions can rotate relative to the compressible member to reduce twisting of the compressible member.

The external surface of the compressible member may be of non-circular section and the interior of the first part be of circular section. The compressible member preferably has a plurality of external flats around it separated from one another by corners, the compressible member contacting the internal surface of the first part at its corners. The compressible member may be of hexagonal shape and the corners may be rounded. The washers are preferably of metal. The second part preferably has a female tapered bore adapted to engage a cooperating male tapered coupling.

- 3 According to another aspect of the present invention there is provided an epidural connector assembly including an epidural cannula and a connector according to the above one aspect of the invention.

An epidural connector assembly in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a sectional side elevation of the connector before mounting on a cannula; Figure 2 is an end view of the connector in the direction of the arrow II in Figure 1; Figure is a transverse section along the line 111 - III of Figure 1, after assembly on the cannula; and Figure 4 is a perspective view of the compressible member in the connector.

The connector 1 is secured to the rear, machine, or proximal end of an epidural cannula 2 and provides a coupling to which a male luer coupling 4 (such as provided by the nose of a syringe) can be mated to enable the supply of analgesia liquid to the cannula.

The connector 1 has a tubular housing 10 of a rigid polyester material formed as a first, forward part 11 and a separate second, rear part 12. The forward part 11 is ribbed externally and has an hollow internal recess 13 of circular section tapered slightly along its axis, with the diameter at its rear end being 4.97mrn and the diameter at its forward end being slightly smaller. At the forward end of the recess 13 an annular shoulder or contact region 15 surrounds an axial opening 16 of diameter 1.2 mm. The opening 16 is flared outwardly at its forward end to provide a rounded mouth to the opening. The rear end of the recess 13 has an internal screw thread 17 receiving the forward end of the rear part 12 of the housing 10.

The forward end of the rear part 12 has a flat end surface or contact region 18 and an external screw thread 19, which engages the thread 17 in the forward part 11. An external flange 20 projects radially from the rear part 12 at a location just forwardly of midway along its length. The flange 20 has several ribs or flats 21 around its edge to enable it to be gripped securely between finger and thumb. At its rear end, the rear part 12 has two radiallyprojecting partial thread forms 22, for engagement by the connector 4, and opens into a female luer taper bore 23 with a diameter of 4.3= at its forward end. The bore 23 extends to the reeion of the flange 20 where it communicates with a short intermediate bore 24 of 0 diameter 0.6 mm. The intermediate bore 24 opens into a larger bore 25 of diameter 1.2 mm, which has a tapered opening 26.

The connector 1 also includes a compressible, resilient member or slug 30, such as of synthetic rubber with a hardness around 50 IRHD. The slug 30 is of generally cylindrical shape being 1 -3). 7 nim long and with an axial bore 3 1 of diameter 1.4 mm. Externally, the slug 30 is of hexagonal shape having six longitudinal flats 332 separated by rounded corners 33 and with a maximum diameter of 4.85 mm. The slug 30 is slightly smaller in diameter than the recess 13 in which the slug is received. The rear end of the slug 30 contacts one face of a steel washer 35 the other face of which is contacted by the contact region 18 on the rear part 12 of the housing. The forward end of the slug 30 contacts one face of a second steel washer 36, the other face of which is contacted by the shoulder 15 on the first part 11 of the housing. The opposite ends of the slug 30 are thereby engaged indirectly, via the two washers 35 and J36, by the shoulder 15 and the contact region 18 on the two parts of the housing 10.

In use, the epidural cannula 2 is pushed through the opening 16 and into the bore 31 of the slug 30, in which it is a sliding fit. The rear end of the cannula 2 passes through the washer 35 and into the forward bore 25 of the rear part 12 of the housing. Insertion of the cannula 2 is limited by a step between the forward bore 25 and the intermediate bore 24, the diameter of which is smaller than the cannula. The two parts 11 and 12 of the housing 10 are screwed together to compress the slug 30 axially. This causes the slug 3 W to expand radially so that its corners 3 3 contact the inside of the recess 13, and so that the bore 3) 1 is compressed into sealing engagement with the outside of the cannula 2, gripping it sufficiently to prevent it being pulled out of the connector. The washers 35 and 36 enable both contact surfaces 18 and 15 to rotate relative to the slug 30 so that the amount of twisting of the slug is considerably reduced compared with similar connectors having only one washer. When tightened to its correct extent, there will be six gaps 40 between the slu. 30 and the forward part 11 of the housing in the region of each flat 32. These gaps 40 provide space to accommodate excess material from the slug 30 when it is compressed further. In this way, the material of the slug 30 can be deformed outwardly instead of being deformed inwardly against the cannula 2, which could cause crushing. The male luer connector 4 can then be inserted in the bore 23 to administer fluid to the cannula 2.

The resilient slug need not be of hexagonal section but could, for example, be circular although it has been found that the two washers are particularly advantageous with slugs of a non-circular section because these have a reduced torsional rigidity compared with circular slugs, and hence are more prone to twisting.

6

Claims

A connector for connection to an epidural cannula, the connector having a compressible member with a bore therethrough sized to receive the cannula, a housing having a first tubular part in which the compressible member is located, the first part having a contact region at one end for engagement with one end of the compressible member, a second part screw threaded relative to the first part, the second part having a contact region for engagement with the other end of the compressible member such that, when the first and second parts are rotated relative to one another the compressible member is compressed axially between the contact regions causing it to expand radially into contact with the internal surface of the first part and to seal about the cannula, wherein the connector has two washers, and wherein one washer is located between the compressible member and each respective contact region such that both the contact regions can rotate relative to the compressible member to reduce twisting of the compressible member.

2.

1 3.

A connector according to Claim 1, wherein the external surface of the compressible member is of non-circular section and the interior of the first part is of circular section.

A connector according to Claim 2, wherein the compressible member has a plurality of external flats around it separated from one another by corners, and wherein the compressible member contacts the internal surface of the first part at its corners.

A connector according to Claim 3, wherein the compressible member is of hexagonal section and the comers are rounded.

7 A connector according to any one of the preceding claims, wherein the washers are of metal.

6. An epidural connector according to any one of the preceding claims, wherein the second part has a female tapered bore adapted to engage a cooperating male tapered coupling.

An epidural connector substantially as hereinbefore described.

8. An epidural connector assembly including an epidural cannula and a connector according to any one of the preceding claims.

9. An epidural connector assembly substantially as hereinbefore described with reference to the accompanying drawings.

10. Any novel and inventive feature as hereinbefore described.