CANNULA

Description

[0001] The invention relates to a cannula with a tip and an outlet. Such cannulas are used in particular as arterial cannulas. They are available in various diameters and lengths.

[0002] A cannula with a valve is known from DE 196 05 864 A1. Several spiral-shaped slits are formed at the end of the cannula, which widen or narrow in response to pressure changes in the lumen of the cannula to reduce the fluid velocity.

[0003] See further, for example, WO 99 / 37351 A1.

[0004] The invention is based on the object of further developing such a cannula.

[0005] This object is achieved in that the cannula according to the invention according to independent claim 1 has a reduction in the inner diameter and a valve is arranged in the region of the reduction in the diameter.

[0006] The reduction in the inner diameter can be designed, by way of example and not according to the invention, as a conically tapered tip. In this case, it is advantageous if the conical end of the tip has a length that is shorter than the inner diameter of the adjacent region of the cannula.

[0007] The reduction of the inner diameter according to the arterial cannula according to the invention is designed as a caliber constriction between two cylindrical cannula sections with different diameters.

[0008] The reduction in the inner diameter is located 25%-40%, preferably approximately 30%-35% of the insertion length, from the tip of the cannula. In an advantageous embodiment, the taper begins after approximately two-thirds of the cannula or insertion length.

[0009] A preferred insertion length for the cannula is 20–50 cm, preferably between 28 and 45 cm. This allows for various placement options depending on the length. A short insertion length allows for placement below the renal artery, while a long insertion length allows for placement above or at the level of the renal artery.

[0010] Depending on the diameter reduction, different caliber jumps occur, ranging from 2 Fr to 4 Fr. Practical examples include 15 Fr to 13 Fr, 17 Fr to 15 Fr, 17 Fr to 13 Fr, 19 Fr to 17 Fr, and 19 Fr to 15 Fr.

[0011] Such a reduction of the inner diameter of a cannula leads to a jet stream at the cannula tip, in the short insertion length or in the reduced diameter cannula area.

[0012] The cannula according to the invention is provided with lateral holes, and the diameter reduction is arranged between the lateral holes and the tip of the cannula. The arrangement of such holes in the cannula ensures perfusion of the lower extremities and reduces afterload.

[0013] The side holes can be provided either in all four quadrants of a cannula, so that several holes are located on the same cross-sectional plane of the cannula. Alternatively, several holes, such as one to three holes, can be arranged in a row.

[0014] Another embodiment provides for one to three holes to be arranged one behind the other in two quadrants (180°) or three quadrants (120°). However, two areas with three holes each, one behind the other, or holes offset by 90° from each other can also be provided.

[0015] The cannula according to the invention has a valve arranged in the region of the reduced diameter. A preferred embodiment provides a cannula with a valve that has at least one and preferably several flaps.

[0016] Such a valve mechanism is based on the principle of the aortic valve, which has, for example, three leaflets. The valve base is preferably located at the transition to the caliber jump. The stronger flow during pump acceleration causes the valve to open. The ratio of relative valve opening to volume flow can be adjusted by positioning and designing the valve.

[0017] According to the inventive design, the valve is located between the opening at the cannula tip and the lateral holes in the cannula. Thus, one partial flow of the perfusion occurs through the cannula center to the cannula tip, and another partial flow occurs through the holes in the cannula wall. The valve, located between the lateral holes and the cannula tip, can thus vary these two partial flows. When the valve is constricted, the volume flow in the lateral holes increases, and when the valve is open, the volume flow to the cannula tip increases.

[0018] A preferred embodiment provides for the valve to have at least one and preferably several flaps. These flaps can be arranged within the cannula to restrict the flow within the cannula to the cannula tip. It is advantageous if at least one flap has a spring mechanism. This spring mechanism can be achieved by a spring or by the material selection and design of the flaps.

[0019] When the cannula is inserted, the spring force of the valve can close the cannula or reduce the flow during phases of low flow through the cannula, for example during cardiac systole. The force of the volume flow counteracts the spring force of the valve. If the force of the volume flow is less than the spring force of the valve, the valve closes. This means that, if side holes are present, the blood flow is largely directed through the side holes and thus supplies the lower extremities, for example. This happens, for example, with cardiac systole during cardiogenic shock, as this is too weak to open the valve, which means that the lower extremities are better supplied with blood. Depending on the arrangement of the side holes, the renal artery can also be supplied in this situation.

[0020] A passive mechanism can be provided for closing the valve, in which the material stiffness of the flap reduces the flow through the valve when the volume flow is reduced. Alternatively or cumulatively, a spring mechanism can be provided on the outer edges of the flap leaflets.

[0021] A further embodiment of the invention provides that the cannula has a spiral structure on its inside, at least in some areas. Such a structure can impart a swirl to the fluid flowing inside the cannula, which stabilizes the flow. This is particularly advantageous in conjunction with the tapered portion, the openings, or the valve, since any change on the inside of the cannula influences the stable volume flow.

[0022] A spiral structure on the inside of the cannula can be achieved, for example, by a spiral arrangement of the holes within the cannula. Alternatively or cumulatively, however, it is provided that a spiral embossing is provided on the inside of the cannula according to the principle of a gun barrel. According to a first embodiment, the structure is designed as an elevation. For this purpose, for example, a spiral-shaped single- or multi-thread structure protruding convexly into the interior of the volume is provided. Such a structure can be incorporated into the inner wall of the cannula or applied to it. Mixed shapes between convex and concave cannula regions can also be provided, which are achieved by application and removal on the inner wall of the cannula or by a corresponding design of the inner wall of the cannula.

[0023] The structure can extend over the entire length of the cannula or only over a portion of it. For example, the structure can be provided only in the last third of the insertion length, in the direction of flow, to impart a swirl to the medium flowing through the cannula only there.

[0024] The pitch of the spiral structure determines the respective twist. The pitch of the structure can be specified as sine α (cannula length divided by cannula diameter) or as sine α of the reciprocal value. This results in a pitch = sine α (cannula length divided by diameter) or a pitch = sine α (1 divided by cannula length divided by diameter).

[0025] A special design variant provides for the structure to be formed by a wire reinforcement of the cannula. A wire reinforcement provided within the cannula can be spiral-shaped and lead to a corresponding spiral structure within the cannula, which creates a twist within the cannula.

[0026] Examples of cannulas according to the invention are shown in the drawing and are explained in more detail below. Figure 1 shows a side view of a cannula with a tapered section and an extended tip. Figure 2 shows a side view of a cannula not according to the invention with a conical tip. Figure 3 shows a side view of a cannula with several holes on the circumference. Figure 4 shows a side view of a cannula with holes arranged offset from one another on the circumference. Figure 5 shows a schematic representation of the function of an open valve in a partially sectioned side view. Figure 6 shows a schematic representation of a front view of the cannula shown in Figure 5shown valve, Figure 7 schematically shows a side view of a partially closed valve, Figure 8 schematically shows a front view of the valve shown in Figure 7 shown valve, Figure 9 schematically shows a section through a cannula with a convex spiral elevation, Figure 10 schematically shows a section through a cannula with two opposite spiral elevations and Figure 11 schematically shows a section through a cannula with four concave spiral depressions.

[0027] The Figure 1 The cannula 1 according to the invention shown has a cylindrical base body 2, a cylindrical cannula tip 3, and a conical taper 4 between them as a diameter reduction, which forms a transition between the cylindrical base body 2 with the larger diameter and the cylindrical tip 3 with the smaller diameter. The position of the taper 4 is selected such that the length 5 is two-thirds of the cannula or insertion length.

[0028] The Figure 2 shows an alternative front end of a cannula 6 not according to the invention, in which a conical constriction 7 forms the front end of the cannula 6, so that the cannula 6 has a conical cannula tip with the length 8.

[0029] Holes 9, 10 are provided inside the cannula and in the main body 2 of the cannula with a larger diameter. Figure 3 shows an arrangement of holes that are offset by 90° in the longitudinal direction of the cannula. In the exemplary embodiment, this results in four slightly offset rows of holes 11, 12, each with three holes 13 - 15, 16 - 18, and 19 - 21.

[0030] In the Figure 4 In the embodiment shown, the entire rows of holes 22, 23, 24 are arranged offset from one another. In the embodiment shown, the rows of holes each have three holes. However, two or more holes can also be provided.

[0031] In the Figures 5 - 8 In the valve 30 shown, three valve leaflets 34, 35, 36 are provided in the tapered region 31 between a cannula region 32 with a larger diameter and a cannula region 33 with a reduced diameter. These leaflets are attached to the inner wall of the cannula in the tapered region 31. These valve leaflets 34-36 are opened by a volume flow 37, creating an opening 38 through which a fluid can flow from the cannula region 32 to the cannula region 33.

[0032] If the pressure of the volume flow 37, as in the Figures 7 and 8 shown, the valve leaflets 34 - 36 are pushed inwards by their material stiffness so that they close the opening 38 by the valve leaflets 34 - 36 coming into contact with each other at point 39 and obstructing or stopping the flow.

[0033] Different variants for applying a twist inside the cannula are described in the Figures 9 - 11These are only schematically illustrated design variants intended to indicate the possibility of applying a twist within the cannula. Figure 9 shows a cannula 40 with a radially inwardly bulging protrusion 41, which extends spirally within the cannula. A two-threaded embodiment is shown in Figure 10 shown. Here, a first elevation 43 is provided within the cannula 42, and a second elevation 44 is provided opposite the elevation 43. Both elevations are part of a double-threaded spiral formed within the cannula 42.

[0034] In Figure 11 is shown using the example of four depressions, how a swirl can be exerted on a liquid guided in the cannula by means of depressions 45 - 48 within a cannula 49.

Claims

1. Arterial cannula (1) with a tip (3) and an outlet, the cannula having a reduction (4) of the internal diameter, which is formed as a caliber narrowing between two cylindrical cannula sections with different diameters, and a valve (30) which is arranged in the region of the reduction (4) of the diameter, wherein the cannula has lateral holes (13-18) and wherein the reduction of the diameter is arranged between the lateral holes and the tip (3) of the cannula characterized in that the reduction (4) of the internal diameter is 25 % to 40 % of the insertion length away from the tip (3) of the cannula (1) and is at a reduction of 2 to 4 Fr.

2. Arterial cannula according to claim 1, characterized in that the valve (30) has at least one and preferably several flaps (34 - 36).

3. Arterial cannula according to claim 2, characterized in that the at least one flap (34 - 36) has a spring mechanism.

4. Arterial cannula according to claim 1 or 2, characterized in that a base of a flap is arranged at the transition zone to the caliber change.

5. Arterial cannula according to one of the preceding claims, characterized in that the reduction (4) of the internal diameter is designed as a conically tapering tip (7).

6. Arterial cannula according to claim 5, characterized in that the conical end of the tip (3) has a length (5) which is shorter than the internal diameter of the adjoining section of the cannula.

7. Arterial cannula according to one of the preceding claims, characterized in that the reduction of the internal diameter is 30 % to 35 % of the insertion length away from the tip of the cannula.

8. Arterial cannula according to one of the preceding claims, characterized in that it has an insertion length of 20 to 50 cm, preferably 28 to 45 cm.

9. Arterial cannula according to one of the preceding claims, characterized in that the reduction (4) in diameter comprises a change in caliber from 15 Fr to 13 Fr, 17 Fr to 15 Fr, 17 Fr to 13 Fr, 19 Fr to 17 Fr or 19 Fr to 15 Fr.

10. Arterial cannula according to one of the preceding claims, characterized in that it has a spiral-shaped structure (41) on its inner side, at least in certain sections.

11. Arterial cannula according to claim 10, characterized in that the structure (41) is an elevation.

12. Arterial cannula according to claim 10, characterized in that the structure (45 - 48) is a recession.

13. Arterial cannula according to any one of claims 10 to 12, characterized in that the structure (43, 44) is multi-threaded.

14. Arterial cannula according to any one of claims 10 to 13, characterized in that the structure is formed by a wire reinforcement of the cannula.