JPH0381391B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a small-diameter, thin-walled catheter with excellent kink resistance, pressure resistance, and flexibility. (Prior Art) Various catheters have been used to introduce fluid into and out of living bodies. Such catheters are required to be flexible and thin. However, reducing the wall thickness to ensure a sufficient flow rate of fluid is contradictory to making the wall less likely to collapse. That is, the thinner the wall, the greater the risk that the catheter will collapse during use. If the catheter were to collapse and become occluded, it would cause serious injury or death to the patient using the catheter.
Therefore, such catheters must be constructed so that they do not kink and occlude when bent to a small radius. Recently, in order to provide these catheters with anti-occlusion properties, it has been proposed to provide reinforcing materials such as wires or synthetic fibers spirally within the walls of the catheters.
(Japanese Patent Application Laid-Open No. 58-38565, etc.) A catheter having such a reinforcing material is called a "reinforced type". (Problem to be solved by the invention) However, in the case of a catheter using a non-metallic wire material with a small initial tensile resistivity (longitudinal elastic modulus) as a reinforcing material, the wire diameter is Since it is necessary to make the material thicker or to use an elastomer with high hardness, there is a problem in that even though the occlusion resistance is improved, the flexibility is poor. On the other hand, in the case of catheters using metal wires with high initial tensile resistivity, such as piano wire or stainless steel wire, when formed into thin walls, the torsional force resulting from the repulsion of the spiral of the wire material causes severe unevenness on the inner and outer surfaces of the tube. Since it is inferior in pressure resistance, it is necessary to make the wall thicker, and it is difficult to strike a balance between flexibility and kink resistance. Furthermore, even if a thin-walled catheter can be obtained, the wall thickness of the catheter will be thinner than the diameter of the metal wire, so if internal pressure is applied to the catheter, the metal wire and elastomer will separate, resulting in a rupture, which will lead to problems with pressure resistance. It was hot. (Means for Solving the Problems) Therefore, an object of the present invention is to provide a thin-walled catheter that uses a reinforcing material and has excellent kink resistance, pressure resistance, and flexibility. That is, the present invention is a thin-walled catheter in which an insertion tip is connected to one end of a small-diameter tube in which a spiral metal wire is embedded in the wall, and a connector portion with an enlarged inner diameter is connected to the other end. Inside the tube wall, which is made of an elastomer with a tensile resistivity y of 1×10 ² Kgf/mm ² or less and whose wall thickness t is 0.5 mm or less and whose inner diameter is 20 mm or less, has an initial tensile resistivity Y of 1×10 ⁴ Kgf/mm ²
The above spiral metal wire is embedded, and the diameter d and spiral pitch p of the spiral metal wire are p>d, and Ck
This is a thin-walled caliber catheter characterized in that it is configured to have a value of 1 to 30. However, the C _k value is a value expressed by the following formula. C _k = Y・d ⁴ /y・D・p・t ^1/2 (mm ^1.5 ) where, Y: Initial tensile resistivity of metal wire (Kgf/mm ² ) y: Initial tensile resistivity of elastomer (Kgf / ^mm2 ) d: Diameter of metal wire (mm) D: Tube inner diameter (mm) t: Tube wall thickness (mm) p: Helical pitch of metal wire (mm) Next, the catheter of the present invention will be explained with reference to the drawings. .
FIG. 1 is a perspective view of the catheter of the present invention, which is composed of a small diameter tube 1, an insertion tip 2 connected to one end of the tube, and a connector portion 3 connected to the other end of the tube. has been done. The small diameter tube 1 satisfies the above-mentioned conditions, that is, the C _k value is within the range of 1 to 30, and a catheter using a tube that satisfies these conditions has a minimum bending radius of 0.6 times the inner diameter of the tube. It has excellent performance with no kink or collapse even under harsh conditions. Here, the minimum bending radius refers to the minimum bending radius at which no bending or buckling of the wire is observed when the tube is bent, and is a value measured at the center line of the tube. When the C _k value is less than 1.0, it is not possible to reduce the minimum bending radius (minimum bending radius) at which a kink occurs for small diameter tubes even with wire assistance.
Kinks are likely to occur, and when the tube is used in a slightly bent state, the tube has a large degree of flatness and the flow rate of the fluid inside the tube is significantly reduced. When the C _k value exceeds 10, the kink resistance is good, but when used with a small bending radius, minute folds occur, although this is not a practical problem. Furthermore, if C _k exceeds 30, only a thin wall thickness can be obtained relative to the wire diameter of the reinforcing wire, and when used with a small bending radius, the tube wall will become indented, and large folds will occur on the inner surface. This is undesirable because it reduces the flow rate in the tube and creates a stagnation area, and the wall thickness becomes too thin, resulting in a decrease in pressure resistance. It is important to use a metal with a sufficiently high initial tensile resistivity as the wire for the small diameter tube used in the present invention, so that even if the diameter of the wire embedded in the tube wall is small, it will have good flexibility. A thin-walled, small-diameter tube with kink resistance and pressure resistance can be obtained. Also, since the diameter of this metal wire is small,
The tube wall thickness can be set to be sufficient for the wire diameter, and a tube with a smooth surface in which the metal wire is completely embedded in the wall can be obtained. According to the research results of the present inventors, a metal wire that can exhibit such characteristics must have an initial tensile resistivity of at least 1×10 ⁴ Kgf/mm ² or more, and anything less than this is sufficient. If we try to obtain good kink resistance, the wire diameter becomes too thick. Suitable metal wire materials include steel wire, stainless steel wire, and tungsten wire. Among these, tungsten wire has a much higher initial tensile resistivity than other wire materials, so it can have the same resistance even with a thinner wire diameter. It exhibits kingability, pressure resistance, and flexibility, making it possible to obtain a thinner and smoother tube. The diameter of the metal wire for small diameter tubes may be smaller than the wall thickness, but is usually 0.4 mm or less, preferably 0.1 mm or less. The smaller the diameter, the thinner the wall thickness and the smoother it can be. Furthermore, the smaller the diameter of the wire, the smaller the pitch, and a thin tube with excellent kink resistance, flexibility, and pressure resistance can be obtained. The usual pitch in the present invention is 1 mm or less, preferably 0.5 mm or less. An elastomer with very high rigidity is not suitable for small-diameter tubes, and the initial tensile resistance is 1.
If it exceeds ×10 ² Kgf/mm ² , satisfactory flexibility will not be achieved. Suitable elastomers include polyvinyl chloride, polyurethane, silicone rubber, fluorocarbon rubber, or materials with similar initial tensile resistivity. Among these, segmented polyurethane consisting of soft segments and hard segments has high biocompatibility and an elongation modulus of approximately 100%, and is therefore particularly suitable for the thin-walled, small-diameter tube of the present invention. The inner diameter of the catheter in the present invention is 20 mm or less,
More preferably 10 mm or less, even more preferably 8 mm
or less, and the wall thickness is 0.5mm or less, preferably 0.3mm
It is as follows. If the inner diameter exceeds 20mm, 1.0≦C _k ＜30
Even within this range, the flatness of the tube becomes large in a slightly bent state, which is not preferable. Inner diameter is 20
If it is less than 10 mm, only creases will occur on the surface even when it is bent a little, and if it is less than 10 mm, the creases will hardly occur. Further, if the wall thickness exceeds 0.5 mm, the kink resistance will be good but the flexibility will be poor, and if the wall thickness is 0.3 mm or less, extremely excellent flexibility will be exhibited. The insertion tip 2 in the catheter of the present invention is
As long as the inner and outer surfaces of the reinforced thin-walled tube are smoothly connected or do not have integrated wires, any known material and structure can be used, but there is no risk of injuring the living body during insertion. It is preferable to use a form or material that has appropriate roundness or flexibility to avoid sagging. Further, a structure having one or more side holes is effective in preventing blockage at the distal end, and a radiopaque structure is also practically meaningful. The connector portion 3 having an enlarged inner diameter and connected to the other end of the small-diameter tube can be made of known materials and structures. In the present invention, in order to prevent kinking at the connection between the connector portion and the small-diameter tube, the connection is structured to protect the connection, as shown in FIG. 2, for example. In other words, in FIG. 2a, the connector part 6 with an enlarged inner diameter has a thickness at least 1.5 times the tube wall thickness t at the connection end with the small diameter tube 1, and a part of the connector part 6 has a thickness on the outer surface side of the tube. covers. If the thickness of the connector part is less than 1.5 times, the connection between the tube and the connector part will be weak and prone to kinks when connected with a connector such as an extracorporeal circulation circuit. If the bending radius is extremely small, kinking can be safely and reliably prevented if the thickness is twice or more. Further, the length S that the connector part covers the outer surface of the reinforcing tube needs to be longer as the inner diameter of the tube becomes thicker, and is usually 3 mm or more, preferably 5 mm or more. The longer this portion is, the more effective it is in preventing kinks at the connecting portion between the tube and the connector portion, but if it is too long, the insertion length of the catheter will be reduced. FIG. 2b shows that the connector part 6 is reinforced at the connection between the tube and the connector part by another elastomer layer 7 covering the connector part. Again, 1.5 of the tube wall thickness at the tube connection end.
It needs to be more than twice as thick. Further, FIG. 2c shows an example in which the connector portion 6 shown in FIG. 2b and the reinforcing elastomer layer 7 are integrally molded. In Fig. 2c, the inner diameter of the connector portion 6 is set to a desired length l (usually
It has the same inner diameter as tube 1 over a range of 10 to 20 mm). Therefore, the kink resistance at the connection portion between the connector portion and the tube can be significantly improved. The catheter of the present invention can be manufactured as follows. First, the insertion tip is extruded by an extruder together with the inner tube of the small-diameter tube, that is, the inner surface tube before the wire is wound, or,
A separately molded product, such as injection molding, can be glued to the end of the small-diameter tube so that at least the outer surface is smooth, or alternatively, a polymer solution can be applied onto a mandrel for small-diameter tubes and dried or heated. forming a tip that is integrated with the small diameter tube by repeating curing;
By the above method, at least the outer surface of the connecting portion between the small diameter tube and the tip can be made smooth. It is important to keep the outer surface of the connection portion smooth so that it can be inserted into and removed from the living body easily and without damaging the living body. Furthermore, by recoating with elastomer solution, etc.
If the inner surface of the catheter is also connected smoothly, it is possible to prevent thrombus formation and deposition of body fluid components at the connection portion. A known method can also be used for forming the small diameter tube portion. For example, first, a thin-walled tube is formed by extruding it with an extruder or by coating a mandrel with an elastomer solution and drying it (inner tube layer forming), and then wrapping a non-metallic wire at a predetermined pitch. A small-diameter tube can be obtained by covering the inner tube layer by extruding an elastomer of the same quality as the inner tube layer using an extruder, or by coating with an elastomer solution and drying (outer tube layer forming). The elastomers used for the inner and outer tube layers do not have to be the same, but it is desirable that they have mutual affinity for the integration of the inner and outer layers. If an elastomer having a hardness equal to or higher than that of the outer tube layer is used for the inner tube layer, a tube with even better flexibility and kink resistance can be obtained. Furthermore, it is effective to bond the nonmetallic wire with an adhesive such as an elastomer, polyurethane, or epoxy resin in advance in order to make it have excellent pressure resistance. Further, when the ratio of the thicknesses of the inner tube layer and the outer tube layer is adjusted so that the wire rod is located approximately in the center of the wall thickness, the smoothness of the inner and outer surfaces of the small diameter tube becomes particularly excellent. The connector portion with an enlarged inner diameter can be formed by extruding it as a thick-walled tube with an enlarged inner diameter using an extruder at the same time as forming a small-diameter inner tube, but it is also possible to mold the connector part with an enlarged inner diameter using an extruder. It can also be formed by forming a thick-walled tube whose inner diameter is larger than the diameter of the small-diameter tube by coating, etc., and then integrating it with the small-diameter tube by fusion or adhesion. In addition, when long-term antithrombotic properties or biocompatibility are required for the catheter of the present invention, it is free to bind or coat with a suitable substance depending on the purpose. Furthermore, the catheter of the present invention can be freely applied to other purposes including endotracheal tubes. (Example) Example 1 A thermoplastic segmented polyurethane elastomer (hereinafter referred to as SPU) with a Shore hardness (A) of 85 was extruded into an inner tube with an inner diameter of 2.6 mm and a wall thickness of 0.12 mm using a conventional extruder, and the tube was then inserted into a mandrel. The initial tensile resistivity was 3.6× using a small lathe.
A tungsten wire of 10 ⁴ Kgf/mm ² and a thickness of 0.08 mm was wound with a pitch of 0.3 mm. The wires were glued and fixed, leaving 10 mm of wire-free sections at both ends, and then the same type of thermoplastic SPU used for the inner tube was immersed in a 6% tetrahydrofuran (THF) solution with a Shore hardness (A) of 80. Form an outer tube layer by coating, 10mm each on both ends.
Zuzu has obtained a flexible small-diameter tube with a wall thickness of 0.25 mm and good smoothness on both the inner and outer surfaces without wires.
The average value of the initial tensile resistivity of SPU for the inner and outer layers is 0.6Kg
f/mm ² and therefore the C _k value is 6.3 mm ^1.5 . This reinforced tube has a minimum bending radius of 1.3 D when a kink occurs, and a withstand pressure of 2.0 Kgf/cm ² or more.
It also had excellent kink resistance and pressure resistance. Next, a mandrel with an enlarged outer diameter is inserted into one end of this small diameter tube, and the mandrel has a Shore hardness (A) of 85.
The SPU solution was coated and the thickness at the end of the small diameter tube was adjusted to 0.7 mm. Also, cut the other end of this tube diagonally and make two side holes with a diameter of 2 mm.
After that, the catheter should be inserted to show hardness.
(A) Immersed in 80% SPU solution and recoated, with inner diameter 2.55 mm and wall thickness as shown in Figure 1.
A 0.35 mm catheter was obtained. This product had excellent kink resistance, flexibility, and pressure resistance, and had smooth inner and outer surfaces. Examples 2 to 7 and Comparative Examples 1 and 2 A tungsten wire with a diameter d (mm) was spirally wound at a constant pitch p (mm) into a core tube with an inner diameter D (mm) made of the same segmented polyurethane elastomer as in Example 1. After winding it into a shape, its surface was coated with the above elastomer in the same manner as in Example 1 to obtain eight types of thin-walled, small-diameter tubes having tube wall thicknesses of t (mm) as shown below. Table 1 shows the relationship between the C _k value and the minimum bending radius of these tubes. Further, the results of Table 1 are shown graphically in FIG. As is clear from the graph, the minimum bending radius reached equilibrium when the C _k value was 10 or more. Therefore, it can be said that a C _k value in the range of 1 to 10 is practical.

[Table] (Effects of the Invention) As described above, since the catheter of the present invention has a thin wall, a large flow rate of fluid can flow even with the same outer diameter. Therefore, when inserted into a blood vessel, for example, it is possible to obtain the same blood flow rate as a conventional catheter even from a smaller blood vessel that is closer to the body surface than in the past, making surgery and other operations easier. Because it is a reinforced type, it has excellent kink resistance, pressure resistance, and flexibility even though it is thin, making it safe. The surface is smooth and does not damage living tissue. It has excellent characteristics such as, and can be effectively used in various medical fields.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the thin-walled catheter of the present invention, FIG. 2 is a cross-sectional view showing the structure of the connection between the thin-walled small-diameter tube and the connector, and FIG. 3 is a graph showing the relationship between the minimum bending radius that will not occur and the C _k value.

Claims (1)

[Scope of Claims] 1. A thin-walled catheter in which an insertion tip is connected to one end of a small-diameter tube in which a spiral metal wire is embedded in the wall, and a connector portion with an enlarged inner diameter is connected to the other end. , initial tensile resistivity y is 1×10 ² Kg
Wall thickness t made of elastomer of f/mm ² or less is 0.5
A helical metal wire with an initial tensile resistivity Y of 1×10 ⁴ Kgf/mm ² or more is embedded in the wall of a tube with an inner diameter of 20 mm or less, and the diameter d and helical pitch p of the helical metal wire are d and a Ck value of 1 to 30. However, the Ck value is a value expressed by the following formula. Ck=Y・d ⁴ /y・D・p・t ^1/2 (mm ^1.5 ) where, Y: Initial tensile resistivity of metal wire (Kgf/mm ² ) y: Initial tensile resistivity of elastomer (Kgf/ mm ² ) d: Diameter of metal wire (mm) D: Tube inner diameter (mm) t: Tube wall thickness (mm) p: Helical pitch of metal wire (mm)