GUIDE WIRE FOR USE IN TUBULAR MEDICAL PROBES, IN PARTICULAR FOR NUTRITIONAL THERAPY

Abstract

A guide wire is provided with radial play for use as reinforcement in a soft probe tube, and has behind an insertion aid first a more flexible portion, before it is adjoined by the conventional guide wire. In that portion, the insertion aid and the guide wire grip coaxially into oppositely located ends of a tubular annular spring, in particular a flat wire coil spring wound on a block.

Claims

1-6. (canceled)

7. A guide wire (13) designed for inserting into the tube (11) of a nutritional probe (12) and provided at its end (16) with an insertion aid (15), wherein proximally behind the insertion aid (15) there is provided a portion (17) of the guide wire (13) of which the flexural stiffness is made to be less than that of the rest of the guide wire (13) proximally adjoining it, wherein a pliable portion (17) typically about 5 cm long of the guide wire (13) between the insertion aid (15) and the rest of the guide wire (13) is formed by a helical spring (19a) wound from flat wire under prestress on block, at which distally the rounded insertion aid (15) is formed and proximally the rest of the guide wire (13), this a stranded wire, engages into the spring (19a), in which it is fixed in a material-bonding manner.

Description

[0014] Additional developments and modifications of the solution according to the invention are provided by the further claims and, while taking their advantages into consideration, from the following description of preferred embodiments of the invention, which are outlined in the drawing in a greatly enlarged form approximately to scale. Depicted in a broken-away representation in the drawing, in each case with a restriction to what is functionally essential:

[0015] FIG. 1 shows in the probe tube a more flexible since narrowed portion of a solid or stranded guide wire as a transition from an insertion aid to the conventional rest of the guide wire according to the prior art and

[0016] FIG. 2 shows in the probe tube a helical spring as such a more flexible portion according to the invention;

[0017] FIG. 3 shows a flat-wire helical spring between the distal insertion aid and the proximal connection to the rest of the guide wire,

[0018] FIG. 4 shows as an insertion aid a short round wire that is rounded off at the end in a flat-wire helical spring;

[0019] FIG. 5 shows a distally weakened guide wire supported against a deflection of the probe tube at risk of perforation and

[0020] FIG. 6 shows the action of a flat-wire helical spring in a situation approximately according to FIG. 5.

[0021] The pliant tube 11, for instance of a nasogastric probe 12, undergoes over its length of typically 50 to 150 cm during the insertion into the patient an internal reinforcement, while having sufficient radial play with respect to the tube inner wall 24, by means of a stranded wire or by means of a solid spring wire of acid-resistant stainless steel as a guide wire 13 of a diameter in the range of typically about 0.75 mm to 1 mm. The distal end 16 of the guide wire 13 is provided with an insertion aid 15 that is rounded off at the end. Its diameter may be much greater than that of the guide wire 13, but it is less than the inside diameter of the tube 11; so that—after the navigation of the probe 12—gastric acid can be drawn off through the tube 11 without any complication, in order to verify the correct position of the probe. For commercially available tubes 11, with an inside diameter of 2 mm to 3 mm, the diameter of a spherical insertion aid 15 at the end is about 1.3 mm. Proximally following the insertion aid 15 there is first a portion 17 of reduced flexural stiffness of the guide wire 13, before it is proximally adjoined by the stiffer conventional rest of the guide wire 13.

[0022] This more flexible portion 17, typically about 5 cm long, between the insertion aid 15 and the rest of the guide wire 13 is provided with a single or multiple wire 18 that is thinner by about 20% to 50% in comparison with the thickness of the rest of the guide wire 13.

[0023] According to the prior art, the wire 18 may be for example an unspliced central part of the strands of the guide wire 13, or a solid stainless steel spring wire welded in between the insertion aid 15 and the rest of the guide wire 13; according to the invention, however, it is a helical spring 19 according to FIG. 2, in particular a flat-wire helical spring 19a according to FIG. 3.

[0024] The free end of such a spring, also known as an annular tube spring, is preferably ground transversely to the longitudinal axis, so that the convex insertion aid 15 to be welded on in front in the form of a prefabricated steel sphere engages in a self-centering manner in the distal end turn of this helical spring 19 or 19a.

[0025] In the case of the exemplary embodiment according to FIG. 3/FIG. 4, the portion 17 in the form of such a flat-wire helical spring 19a is fixed in a frictionally engaging or material-bonding manner on the outer lateral surface 20 of the rest of the guide wire 13 by its greater spring stiffness in comparison with the portion 17. For this, the rest of the guide wire 13 engages in the way shown with its distal end coaxially in the helical spring 19 or 19a by a few turns. Axially opposite, the outside diameter of the helical spring 19/19a in the case that is represented by way of example in FIG. 3 of a spherical insertion aid 15 fastened distally in front is slightly overlapped radially by it.

[0026] According to FIG. 3/FIG. 4, the helical spring 19a is wound from (rolled) flat wire, preferably under prestress between the successive turns on a block. Then, this portion 17 cannot move away as easily under axial compressive loading. On the other hand, this produces the advantage that higher tensile forces can be introduced under tensile loading for withdrawing the guide wire 13 from the positioned tube 11 without any complication, without permanently deforming the flat-wire helical spring 19a thereby.

[0027] The welding operation between the small dimensions for mounting an insertion aid 15 as shown in FIG. 3 is critical in process engineering terms. To be preferred, therefore, is to distally round a wire-shaped flexible portion 17 according to FIG. 1; or to make a short linear portion of wire 14 (FIG. 4) of the order of magnitude of 3-4 mm in length engage instead of a sphere in the distal end of the helical spring 19 or 19a and fix it coaxially therein in a material-bonding manner, in particular by welding. If this pin-shaped insertion aid 15 is not already supplied in such a rounded-off form, the distally projecting end of the portion of wire 14 can without any problem be given a rounding 21 by laser melting forming after mounting. In any event, with this development according to the invention of the use of a short linear portion of wire 14 according to FIG. 4, there is no need for the requirement of grinding the spring transversely to the longitudinal axis, since a sphere no longer has to be centered on the distal end of the annular tube spring.

[0028] If, during its advancement, the probe tube 11 has undergone a deflection 22, for instance according to FIG. 5, then conventionally there is the risk here, at the supporting point 23, of being perforated by the insertion aid 15 at the end 16 of a relatively stiff, and therefore virtually linearly pushed-after guide wire 13 according to the prior art.

[0029] This risk is then averted by the more flexible front portion 17 according to the invention of the guide wire 13; especially if, according to FIG. 6, the insertion aid 15 is followed proximally by the more flexible portion 17 of the guide wire 13 in the form of a flat-wire helical spring 19a. This is so because then, when axial pressure is exerted externally on the guide wire 13, the insertion aid 15 can approximately follow the course of the bend of the probe 12 along the tube inner wall 24. The helical spring 19a is therefore elastically deformed, which brings about a restoring force into the linear series of flat wire turns; with the tendency of straightening out the course of the deflection 22. Also, the relatively more rigid rest of the guide wire 13 following the portion 17 in the bend 22 of the probe exerts a straightening moment on this deflection 22, which to some degree straightens the bending, when it is pushed after the portion 17. In this case, a portion 17 in the form of a helical spring 19 delivers a greater straightening moment than a spring wire or even a stranded wire, which leaves greater permanent deformations. In any event, as a result of the portion 17 (FIG. 6), virtually no supporting point at risk of perforation (23 in FIG. 5) occurs any longer in the probe tube 11.

[0030] If, however, the deflection 22 becomes so severe that the insertion aid 15 can no longer pass this buckling point, for instance because of the reduced remaining diameter of the interior tube space 25, the support of the insertion aid 15 against the buckling point has the effect in the interior of the tube 11 that, when pressure is exerted longitudinally on the proximal guide wire 13 according to FIG. 6, initially there is a buckling of the portion 17 in the probe tube 11 and then, because it is butting against the inner wall 24 of the tube 11, also deflection of the latter. This has the consequence that force components are transferred over the surface area radially onto the wall of the tube 11 and dissipated thereover, so that the remaining other, locally limited force component is usually no longer enough for the tube 11 to be punctured by the insertion aid 15 blocked at the buckling point.

[0031] What has been described above for the example of a nasogastric probe 11 can also be realized within the scope of the present invention in the case of intravascular insertion aids.

[0032] A guide wire 13 provided for use as a reinforcement in a pliable probe tube 11, while having radial play, therefore has proximally behind an insertion aid 15 first a flexible tip in the form of a more flexible portion 17 in comparison with the rest of the guide wire 13, before it is in turn adjoined proximally by the rest of this guide wire 13 of a conventional form. According to the invention, that portion 17 may be designed in such a way that, for this, the insertion aid 15 and the conventional rest of the guide wire 13 engage coaxially in ends opposite one another of an annular tube spring wound with or without prestress, in particular a flat-wire helical spring 19a of lower flexural stiffness wound under prestress on a block.

LIST OF DESIGNATIONS

[0033] 11 Tube (of 12) [0034] 12 Probe [0035] 13 Guide wire (with 17, 15; in 11) [0036] 14 Portion of wire (with 21; in 19/19a) [0037] 15 Insertion aid (at 16) [0038] 16 End (of 13, 17) [0039] 17 Portion (of reduced flexural stiffness; 13 proximally behind 15) [0040] 18 Solid wire (as 13, 17) [0041] 19 helical spring (as 17); 19a flat wire helical spring (as 17) [0042] 20 Outer lateral surface (of 13) [0043] 21 Rounding (as 15) [0044] 22 Deflection (of 11) [0045] 23 Supporting point (of 24 against 15 at 22) [0046] 24 Inner wall (of 11) [0047] 25 Interior space (of 11)