GB2263642A

GB2263642A - Catheter/sheath assembly for embryo transfer

Info

Publication number: GB2263642A
Application number: GB9301359A
Authority: GB
Inventors: Jonathan Bartlett; Nicholas James Tyrrell
Original assignee: Rocket of London Ltd
Current assignee: Rocket of London Ltd
Priority date: 1992-01-25
Filing date: 1993-01-25
Publication date: 1993-08-04
Anticipated expiration: 2013-01-25
Also published as: GB2263642B; GB9301359D0; GB9201624D0

Abstract

The assembly, which is suitable for use in in-vitro fertilisation, comprises a sheath 10 having graduations 12 at a distal end and graduations in the form of ribs 6 at a proximal end, and a catheter 20 slidable within the sheath, the catheter having a marker bead 24 thereon which is detectable externally of the sheath and which corresponds in position with the graduations 6 at the proximal and of the sheath. The handle 5 of the sheath may be transparent so that the marker bead can be observed therethrough. When the bead is aligned with the proximal edge of the handle, the end of the catheter is flush with the distal tip 13 of the sheath, and when aligned with the first moulded rib 6, the end 20b protrudes 1 cm, from the said tip, and so on. The distal and graduations 12 indicate the depth of insertion of the sheath. <IMAGE>

Description

"Embryo Transfer Catheter" This invention relates to an embryo transfer catheter particularly suited for use in the implantation of preembryos in close proximity to the fundus of the uterus during In Vitro Fertilisation as a treatment for infertility.

The delivery of embryos into the uterus and their subsequent implantation is a conventional technique to counteract infertility. Catheters for the delivery of embryos into the uterus are known and generally comprise a soft inner catheter of synthetic polymer for carrying the pre-embryo through the vagina and cervical canal into the uterus. The catheter is required to be soft and non-toxic in order to prevent damage to the embryo or the cervical canal.

Since the catheter is of pliable material it cannot easily be manoevered within the vagina or through the cervical canal. Accordingly, such catheters are generally used in conjunction with a semi-rigid outer sheath which envelops the catheter and within which the catheter is slidable. The sheath thereby provides support to the catheter facilitating its manipulation within the vagina, and protects the catheter tip during such manipulation.

In use, the sheath is slid over the catheter to cover its tip and the assembly is manipulated through the vagina to the cervical os, where the sheath can then be held stationary while the catheter is advanced through the cervical canal and into the uterus.

An important feature of such a system is the ability to easily determine the position of the tip of the catheter when the sheath is in a defined position.

Specifically, it is important to be able to deliver the pre-embryo into the fundus of the uterus since this is the optimum site for implantation. To achieve this, a system has been developed having graduations on both the inner catheter and the outer sheath.

This system is described in UK Patent No. GB2,209,673 and comprises a catheter and sheath combination, the catheter being slidable within the sheath; the sheath having graduations adjacent its distal tip and the catheter having graduations on its surface adjacent to a small hub on the catheter. The graduations may take the form of indentations into the surface of the sheath or catheter.

This type of system has the disadvantage that the respective hubs of the sheath and catheter are small and they provide the only portion of the assembly which can be gripped for manipulation of the assembly in use.

Thus, in use, the graduations on the catheter are frequently covered by the operator's fingers. An associated disadvantage is that the view of the cervix is reduced and the risk of endocervical trauma with associated bleeding is increased. The presence of blood greatly reduces the success rate for implantation of embryos into the endometrium.

According to the present invention there is provided a catheter and sheath assembly in which the catheter is slidable within the sheath between a first position in which the distal end of the catheter is generally coincident with the distal end of the sheath and a second position in which the distal end of the catheter projects from the distal end of the sheath, the sheath having first graduations adjacent its distal end for use in indicating to a user of the assembly the depth of insertion of the sheath into a body cavity, and the catheter having a marker thereon which is detectable externally of the sheath and which corresponds in position with a portion of the sheath having second graduations.

Preferably the second graduations on the sheath are provided at a position of the sheath which is translucent or transparent so that the marker on the catheter is visible therethrough.

Preferably also, the second graduations on the sheath are provided adjacent the proximal end of the sheath, most preferably on a handle portion of the sheath.

Preferably also a stop member is provided on the catheter to engage with the sheath to limit sliding movement of the catheter in at least one direction.

Preferably also, the second graduations are in the form of a plurality of spaced-apart moulded ribs protruding from the handle portion.

Preferably the handle portion is at least 5 cm long and is provided with said moulded ribs at 1 cm intervals thereon. The moulded ribs provide graduations for use in the indication of the depth of insertion of the catheter within the sheath and also provide a grip aid to facilitate the manipulation of the assembly.

An embodiment of the present invention will now be described by way of example, with reference to the accompanying drawings in which: Fig. 1 is a side view of a sheath of a sheath and catheter assembly of the invention.

Fig. 2 is a side view of the sheath of Fig. 1 turned axially through 900.

Fig. 3 is a side view of a catheter of the sheath and catheter assembly of the invention.

A sheath and catheter assembly according to one embodiment of the invention comprises a sheath component having at one end a transparent handle 5 with moulded ribs 6 at 1 cm intervals. A sheath 10 of polythene extends from the handle 5. The sheath 10 is formed from a plastics material having excellent memory characteristics such that it can be formed with the fingers and will retain its formed shape to facilitate entry into the external os. The sheath also has graduations 12 at 1 cm intervals at its distal tip 13 and has an axial bore 15 extending throughout the length of the sheath 10.

A catheter 20 of the assembly comprises a flexible tube 21 of outer diameter 1.5 mm, inner diameter 1.0 mm, length 420 mm and internal volume of 0.165 ml. At one end 20a, there is a standard female luer lock fitting 22 and a marker bead 24 fixed approximately 45 mm from end 20a. Between the luer lock fitting 22 and the marker bead 24 there is a sliding luer fitting 23 which may be slid along the tube 21.

The catheter 20 is constructed from a polyurethane derivative such as Estane, (RTM) which is extremely soft and pliable and of low embryo toxicity thereby minimizing damage to the embryo during manipulation.

Furthermore the catheter 20 has a hot formed tip at 20b to minimize endo cervical trauma when the catheter is inserted through the external os.

The catheter 20 is inserted into the bore 15 of the sheath component 1 by inserting the end 20b of the catheter into the sheath 10 at the handle 5. The catheter 20 is then fed into the sheath until the marker bead 24 is visible through the wall of the transparent handle 5. When the bead 24 is aligned with the proximal edge of the handle, the end 20b of the catheter is flush with the distal tip 13 of the sheath, when the bead is aligned with the first moulded rib 6, the end 20b of the catheter 20 protrudes 1 cm from the distal tip 13 of the sheath 10, and when the catheter is fully inserted and the bead is flush with the fifth moulded rib, the end 20b of the catheter protrudes 5 cm from the tip 13 of the sheath 10. Thus the extent of protrusion of the catheter end 20b from the sheath 10 can be readily ascertained. The extent of protrusion of the end 20b can in addition be controlled in this embodiment by setting the sliding luer fitting 23 at a defined position on the tube 21 to prevent insertion of the catheter beyond a limited extent.

A further embodiment of the invention is shown in Figs.

4, 5 and 6 wherein: Fig. 4 is a side view of a sheath and catheter assembly according to the invention; Fig. 5 is a side view of the catheter of the assembly shown in Fig. 4; and Fig. 6 is a side view of the sheath of the assembly shown in Fig. 4.

The second embodiment shares common features with the first and the same reference numbers have been used to identify these features. The second embodiment is a shorter assembly comprising a catheter 20 of length 218 mm and a sheath of length 175 mm. The second embodiment does not include the sliding luer fitting 23.

The degree of control afforded by the present invention allows the surgeon to expel the embryo from the catheter at a more precisely defined location than was previously feasible.

Current designs of embryo transfer catheter are known to be difficult to grip and orientate, particularly when negotiating a difficult cervix. Current designs also utilise resilient materials which do not allow easier access to the retroverted uterus or difficult or stenotic cervix. The present invention mitigates these problems providing an easily manipulated integral handle and tip indicator system and a pliable sheath with memory characteristics.

Modifications and improvements may be incorporated without departing from the scope of the invention.

Claims

1 A catheter and sheath assembly in which the catheter is slidable within the sheath between a first position in which the distal end of the catheter is generally coincident with the distal end of the sheath and a second position in which the distal end of the catheter projects from the distal end of the sheath, the sheath having first graduations adjacent its distal end for use in indicating to a user of the assembly the depth of insertion of the sheath into a body cavity, and the catheter having a marker thereon which is detectable externally of the sheath and which corresponds in position with a portion of the sheath having second graduations.

2 An assembly as claimed in Claim 1, wherein the second graduations on the sheath are provided at a position of the sheath which is translucent or transparent so that the marker on the catheter is visible therethrough.

3 An assembly as claimed in Claim 1 or 2, wherein the second graduations on the sheath are provided adjacent the proximal end of the sheath.

4 An assembly as claimed in Claim 1, 2 or 3 wherein the second graduation on the sheath are provided on a handle portion of the sheath.

5 An assembly as claimed in any one of the preceding claims wherein the second graduations are in the form of a plurality of moulded ribs protruding from the handle portion.

6 An assembly as claimed in any one of the preceding claims wherein the handle portion is at least 5 cm in length and on which the second graduations are disposed being spaced at intervals on the handle portion.

7 An assembly as claimed in any one of the preceding claims wherein a stop member is provided on the catheter to engage with the sheath to limit sliding movement of the catheter in at least one direction.

8 An assembly as claimed in any one of the preceding claims wherein the sheath is further characterised in that it is adapted to retain preformed configuration.

9 An assembly as herein and before described with reference to Figs. 1, 2 and 3 of the accompanying drawings.

10 An assembly as hereinbefore described with reference to Figs. 4, 5 and 6 of the accompanying drawings.