WO2006051353A1

WO2006051353A1 - Plastic cannula

Info

Publication number: WO2006051353A1
Application number: PCT/IB2005/000887
Authority: WO
Inventors: Helmut Frey; Francesco Ribolzi
Original assignee: Gambro Lundia Ab
Priority date: 2004-11-10
Filing date: 2005-04-05
Publication date: 2006-05-18
Also published as: CN101056664A; FR2877580A1; DE212005000058U1; CN100512896C; FR2877580B1

Abstract

The invention concerns a plastic cannula 1 comprising a body with a passage for fluid extending through it, the body comprising a penetrating end part (2) intended to penetrate a septum, a connecting end part 4 remote from the penetrating end part, and an intermediate grip part (3) situated between the two end parts (2, 4), the penetrating end part (2) defining, at its free end (2a), an edge (2c) about the longitudinal axis of the cannula; the edge (2c) of the penetrating end part, seen in a longitudinal view, has a curved profile with a concavity facing toward the outside of the cannula.

Description

DESCRIPTION

Plastic Cannula

Technical field of the invention

The present invention concerns a plastic cannula for connecting a fluid line at an access site to another line.

The access site is provided with a septum, that is to say a partition, which can be penetrated by the end of a cannula.

Prior art

For access to septums made of elastomer, needles made of metal were developed in the first instance. These are hollow tapered rods for injections and they are generally made of steel.

These strong and pointed needles soon led to problems of needle-stick injuries to patients and medical personnel, either before use, or, worse still, after use, when they are capable of transferring viruses to the person pricked.

To overcome this problem, needle protectors attached to the needle itself were developed. These generally have the form of a cylinder, are attached to the needle, extend all around the penetrating end part and define an edge which protrudes beyond the penetrating end of the needle. Such a protector, however, requires an injection site adapted to the shape of the protector.

Cannulas made of plastic were then developed, the plastic being able to impart to an injection device a greater or lesser degree of pliability. These cannulas are less sharp than a metal needle. If they are accidentally brought up against the skin, they do not penetrate it, and instead they bend upon contact with the skin. They can be used for insertion into two types of access sites: access sites with a pre-cut septum, and access sites with a septum which is not cut. Access sites with a pre-cut septum are known: a slit has been formed prior to insertion of the cannula, without thereby forming an opening in the septum. The cannula therefore does not itself need to slice the septum in order to penetrate it. The elongate shape, nevertheless, of the end of the cannula means that it can be easily introduced into the slit of the septum.

A second known type of septum is one which is not cut and which must receive a cannula sufficiently pointed and sharp to pierce it correctly and penetrate the septum.

The cannulas known in the prior art are designed to be used only in one of these two types of septums.

The patent US 5,445,630 describes a cannula with a pointed end for insertion into a fluid line or fluid reservoir by piercing an access site of the line or of the reservoir. The end of the cannula defines an edge having a profile which is straight and inclined in relation to the longitudinal axis of the needle. This cannula with cutting edge is used exclusively to pierce a septum which has not been pre-cut.

Similarly, patent application WO2004/054643 describes a needle body with pointed end, where the end defines an edge having a profile which is straight and inclined in relation to the longitudinal axis of the needle. The other end of this needle body - which is not the penetrating end - is placed inside a grip part attached to the needle body and permitting manipulation thereof. This end has an edge delimiting a curved profile of specific shape.

In these two documents, the end of the cannula intended to penetrate the access site defines an edge whose profile, in longitudinal section, is straight and inclined in relation to the longitudinal axis of the cannula.

Such an edge does of course allow the septum in the access site to be cut through. However, it has been found that the septum may be torn and damaged by this type of needle upon insertion of such a cannula into the latter: if the septum is torn, leaks then occur, the flow rate of fluid drops, and the septum, and consequently the entire access device, must be changed.

In contrast to the teaching concerning a beveled profile of the edge at the end of the cannula as disclosed by these first two documents, a third document, WO89/06553, describes a cannula which has a penetrating end whose edge defines a profile, seen in a longitudinal view, which is straight and perpendicular to the longitudinal axis of the cannula for penetration into an injection site with pre-cut septum.

The shape of the penetrating end is thus "blunted" in comparison to the shape described in the two first-mentioned documents and allows the cannula to be engaged in a pre-cut septum without being able to further cut it and without damaging the cut already made.

In conclusion, these two types of cannula profile ("straight and perpendicular" profile, and beveled profile) are reserved for use on one of the two existing septums: the profile intended for the pre-cut septum cannot be effectively used in the non-cut septum, and vice versa.

Moreover, a cannula can have a frustoconical penetrating end part, that is to say it can have a cross-sectional surface which diminishes toward the end. Such a cannula is described in particular in document US 5,445,630 and in document WO89/06553. This shape permits easier penetration of the penetrating end part of the cannula because it guides the penetration of the end part. Nevertheless, it has been found that the cannula, once inserted and with fluid passing through it, has a tendency to suffer a phenomenon referred to as "kickback" by the person skilled in the art.

To solve this "kickback" problem, cannulas with a penetrating end part having a cylindrical outer surface have been developed. The cross- sectional surface of the penetrating part is constant. Such a cannula is described in particular in document WO89/06553.

Such a cylindrical shape avoids "kickback" of the cannula. However, this shape is not suitable for all configurations because such cannulas are not able to easily penetrate a septum. They may be deflected upon insertion of the end part more so than in the case of an end part of frustoconical cross section.

The subject of the invention is a cannula which can be easily used in a septum not pre-cut and is able to cut the septum without tearing it.

Another object of the invention is to have a cannula which permits easy insertion of the whole of the penetrating part.

Another object of the invention is to make available a cannula which suffers the least possible "kickback".

Another aspect of the invention is the production of such a cannula by molding. Another object is to facilitate mold extraction by virtue of the shape of the cannula to be produced.

Disclosure of the invention

The invention concerns a plastic cannula 1 comprising a body with a passage for fluid 1a extending through it. This body comprises a penetrating end part 2 intended to penetrate a septum, a connecting end part 4 remote from the penetrating end part 2, and an intermediate grip part 3 situated between the two end parts 2, 4, the penetrating end part 2 defining, at its free end 2a, an edge 2c about the longitudinal axis of the cannula. This edge 2c, seen in a longitudinal side view in Figure 2, has a curved profile with a concavity facing toward the outside of the cannula.

Brief description of the drawings

Other advantages and characteristics of the invention will become apparent on reading the following description.

Reference will be made to the attached drawings in which:

Figure 1 shows a longitudinal cross section of the cannula according to the invention;

Figure 2 shows a longitudinal side view of the cannula according to the invention;

Figure 3 shows a detail of the free end of the penetrating end part of the cannula according to the invention, still in a longitudinal side view;

Figure 4 shows a view of the cannula taken along the straight line IV-IV in Fig. 2. Detailed description of an embodiment of the invention

The cannula according to the invention is made of plastic and comprises a body 1 with a passage for fluid 1a which extends through it and brings a proximal opening 1b into communication with a distal opening 1c. Referring to Figure 1 , this body 1 comprises a penetrating end part 2 intended to penetrate a septum, a connecting end part 4 remote from the penetrating end part 2, and an intermediate grip part 3 situated between the two end parts 2, 4.

The penetrating end part 2 defines, at its free end 2a, a terminal edge 2c delimiting the distal opening 1c, which is situated around the longitudinal axis of the cannula. The edge 2c of the penetrating end part 2, seen in a longitudinal side view (see Figures 2 and 3), has a curved profile with a concavity facing toward the outside of the cannula 1.

This cannula therefore has an end which increasingly narrows (rather than extending linearly) in the direction toward its distal part, as is illustrated in Figures 2 and 3; this does not require such a high penetration force as is needed for a cannula having an end with a beveled edge. This also makes it possible to cut a septum correctly, with less probability of tearing it. This is because the septum surface exposed to the insertion and cut increases, during the insertion, less rapidly than in the case of a cannula having an end with a beveled edge, in the initial phase of the cutting. To be more precise, the cutting of the septum by the edge can be divided into two phases: the initial phase of cutting in which the insertion is facilitated, and the second phase of cutting in which the insertion is made more difficult because the septum surface exposed to the insertion increases more rapidly than in the case of the cannula with a beveled edge. The initial phase of cutting, which is the phase made easier by the outward concave shape of the profile of the edge, is however the most important phase in the insertion of the cannula. This is why the concave shape of the profile affords such an advantage in inserting the cannula.

To increase the stability of the cannula once inserted, the latter can have a penetrating end part 2 whose outer surface is conical. Moreover, the phase of insertion of the penetrating end part, once the two cutting phases have been completed, is facilitated by this frustoconical shape. The penetrating end part 2 of the cannula can have a conical or cylindrical inner surface depending on the desired flow rate of the fluid and on the viscosity of the fluid intended to pass through it.

More precisely, the connecting end part with a conical outer surface has a constant conicity. The conicity can present an angle of between 0 (connector not included) and 4°, for example equal to 2°. This angle is the angle defined by the outer wall of the connecting end part and the longitudinal axis of the cannula (angle α shown in Figure 1). The conicity is thus made slight in order to ensure considerable ease of insertion and to give the cannula a certain stability once it has been inserted.

Let us now once again consider the distal part of the penetrating portion 2 of the cannula. As is illustrated in Figure 3, at least part of the edge 2c of the penetrating end part 2 can have a widening 7 from the inside of the edge 72 to the outside of the edge 71. For at least part of the edge, in line with the widening, this means that the thickness of the edge of the end part decreases constantly from the outer part of the edge to the inner part of the edge. Figure 3 shows the detail of the end edge 2c of the penetrating part. A first circle 71 ' and a second circle 72' are shown in order to define the widening 7 of the edge. An arc of the second circle 72' delimits the inner part of the edge, and an arc of the first circle 71' delimits the outer part of the end edge 2c. The two circle arcs are offset and thus define the widening 7. The diameters of the two circle arcs can be identical or substantially identical. If the diameters are different, the diameter of the first circle 71' is greater than that of the second circle 72'.

Thus, a pointing of the edge is obtained in 3 dimensions, on the one hand via its curved profile in longitudinal section, and on the other hand via the widening 7 of at least part of the edge. In particular, the widening can be uniform all round the edge, except on the distal part of the edge.

The reason for this is that, if part of the edge has a widening, another part - the distal end 21a in Fig. 3 - of the edge cannot have such a widening because it defines a termination segment situated in a plane orthogonal to the longitudinal axis of the cannula. Thus, the thickness of the distal end is constant and does not include a widening.

This segment 21a is the first part of the cannula to come into contact with the septum. The segment must have a shape which is such that it will be sufficiently strong and at the same time sufficiently fine to slit the septum without tearing it.

As regards the intermediate grip part 3 of the cannula, this is shown in Figures 1 , 2 and 4.

The intermediate grip part 3 is tubular with a cross section in the form of a circular crown; its external diameter is greater than the maximum external diameter of the conical surface of the penetrating end part 2. These dimensions lead to the formation of a shoulder 5. This shoulder serves as an abutment for the cannula on the septum once it has been introduced.

This shoulder defines the maximum length of the cannula to be inserted.

This shoulder 5 can be in a plane orthogonal to the longitudinal axis of the cannula 1. Consequently, its function is also to keep the cannula inserted in the septum in a stable position.

The intermediate grip part 3 can have an internal diameter greater than the maximum internal diameter of the conical surface of the penetrating end part 2. This permits, in particular, efficient passage of the fluid as a function of its viscosity.

The intermediate part comprises a protuberance 30 situated all round the longitudinal axis, and symmetrically with respect to the latter. It has a shape allowing a user to grip it with at least two fingers.

Still with a view to improving the handling of the cannula by any user, the protuberance 30 can have a substantially prismatic outer shape with four plane surfaces (30a, 30b, 30c, 3Od) which are parallel to the longitudinal axis and are provided with axially spaced ridges 32. The ridges 32 avoid any slipping of the finger on the plane surface.

The protuberance 30 and a portion of the intermediate grip part 3 can be such that they define an annular seat 31 around the longitudinal axis of the cannula, allowing the cannula 1 to receive a protective cap (not shown). It is possible to use any known type of connection permitting coupling of the cannula to the protective cap, such as an interference fit, a bayonet coupling, a screw thread etc., and able to be used with a material such as plastic. Finally, as regards the connecting end part 4, this is tubular also and can have a cylindrical outer surface and a cylindrical inner surface.

Either the inner surface or the outer surface of the connecting end part 4 is provided with connecting means, so as to be able to connect the cannula 1 to a source of fluid. These connecting means are any type of connecting means known to the person skilled in the art: interference fit, bayonet coupling, screw, etc.

Advantages of the invention

The many advantages afforded by the invention are as follows:

- easier penetration into a septum which is not cut, at the same time avoiding too great an opening or tearing of said septum,

easy deliberate insertion of the whole of the penetrating part of the cannula into the septum,

accidental insertion into the skin of a user made difficult,

easier and more secure manual grip by the user,

- penetration of the cannula limited to the desired length,

protection of the penetrating part when the cannula is not in use,

improved flow rate of fluids of a defined viscosity,

increased stability of the cannula in the inserted position,

easier mold removal by virtue in particular of the shape of the free end of the penetrating end part: the thin shape of the cannula and the curved shape of the profile permit precise formation by molding of the end of the cannula and simplified removal because the mold material slides easily in the mold suitable for the invention.

Claims

1. A plastic cannula (1) comprising a body with a passage for fluid extending through it, the body comprising:

a penetrating end part (2) intended to penetrate a septum,

a connecting end part (4) remote from the penetrating end part, and

an intermediate grip part (3) situated between the two end parts (2, 4),

the penetrating end part (2) defining, at its free end (2a), an edge (2c) about the longitudinal axis of the cannula,

wherein

the edge (2c) of the penetrating end part, seen in a longitudinal side view, has a curved profile with a concavity facing toward the outside of the cannula.

2. The cannula (1) as claimed in claim 1 , wherein the penetrating end part (2) has a conical outer surface.

3. The cannula (1) as claimed in claim 1 or 2, wherein the penetrating end part (2) has a conical or cylindrical inner surface.

4. The cannula (1) as claimed in either of claims 2 and 3, wherein the conicity of said outer surface is constant and equal to 2°.

5. The cannula (1) as claimed in one of the preceding claims, wherein at least part of the edge (2c) of the penetrating end part (2) has a widening (7) from the inside of the edge (72) to the outside of the edge (71).

6. The cannula (1) as claimed in one of the preceding claims, wherein the distal end (21a) of said edge (2c) defines a termination segment (21a) situated in a plane orthogonal to the longitudinal axis of the cannula.

7. The cannula (1) as claimed in one of the preceding claims, wherein the intermediate grip part (3) comprises a protuberance (30) situated all round the longitudinal axis, and symmetrically with respect to the latter, and having a shape allowing a user to grip it with at least two fingers.

8. The cannula (1) as claimed in the preceding claim, wherein the protuberance (30) has a substantially prismatic outer shape with four plane surfaces (30a, 30b, 30c, 3Od) which are parallel to the longitudinal axis and are provided with axially spaced ridges to improve the grip.

9. The cannula (1) as claimed in one of the preceding claims, wherein the intermediate grip part (3) comprises a cylindrical outer surface whose external diameter is greater than the maximum external diameter of the conical surface of the penetrating end part (2) so as to form a shoulder (5).

10. The cannula (1) as claimed in the preceding claim, wherein the shoulder (5) is in a plane orthogonal to the longitudinal axis of the cannula (1).

11. The cannula (1) as claimed in one of the preceding claims, wherein the intermediate grip part (3) comprises a cylindrical inner surface whose internal diameter is greater than the maximum internal diameter of the conical surface of the penetrating end part (2).

12. The cannula (1) as claimed in one of claims 7 through 11 , wherein the protuberance (30) and a portion of the intermediate grip part (3) define an annular seat (31) around the longitudinal axis of the cannula, allowing the cannula (1 ) to receive a protective cap.

13. The cannula (1) as claimed in one of the preceding claims, wherein the connecting end part (4) has a cylindrical outer surface and a cylindrical inner surface.

14. The cannula (1) as claimed in the preceding claim, wherein either the inner surface or the outer surface of the connecting end part (4) is provided with means of connection so as to connect the cannula (1) to a source of fluid.