Stylet and catheter assembly

Abstract

To provide a stylet that prevents kinking and breakage, provides flexibility on the tip end side, maintains a desired hardness on the base end side, and allows a catheter assembly to be suitably inserted along a guide wire. [Solution] A stylet 50 comprises an outer tube 51 extending in the axial direction, and an inner tube 52 that is hollow and harder than the outer tube, and is disposed around the inner circumference of the outer tube. The inner tube has a tapered section 52B on the inner circumferential surface at the distal end of the inner tube, the diameter of which tapers toward the base end in the axial direction and which guides a guide wire into the lumen of the inner tube.

Description

[Technical Field]

[0001] The present invention relates to a stylet and catheter assembly. [Background technology]

[0002] Percutaneous cardiopulmonary support (PCPS) has traditionally been used to provide cardiopulmonary resuscitation, circulatory support, and respiratory support in emergency care. PCPS is a method of temporarily supporting or substituting for cardiopulmonary function using an extracorporeal circulation device.

[0003] The extracorporeal circulation device includes an extracorporeal circulation circuit composed of a centrifugal pump, an artificial lung, a blood removal line, a blood transfer line, etc., and performs gas exchange on the removed blood before transferring it to the blood transfer line.

[0004] The blood removal and blood return paths of such an extracorporeal circuit can use, for example, a high-performance cannula disclosed in Patent Document 1. The high-performance cannula (catheter assembly) disclosed in Patent Document 1 is inserted into a living body with a mandrel (stylet) inserted into the cannula body (catheter).

[0005] With such a stylet, the tip side needs to be flexible to prevent damage to blood vessels when the catheter assembly is percutaneously inserted into the body, while the proximal side (base end) needs to maintain a certain hardness from the standpoint of operability.

[0006] In this regard, for example, Patent Document 2 listed below discloses a catheter that has flexibility on the distal end side while maintaining hardness on the proximal end side by joining together resins of different materials and hardness. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5059305 specification [Patent Document 2] Japanese Patent Application Publication No. 1-310666 Summary of the Invention [Problem to be solved by the invention]

[0008] When the catheter disclosed in Patent Document 2 is used as a stylet, it is constructed by joining together resins of different materials, and depending on the compatibility between the different materials, they may not be joined properly, which could result in kinking or breakage at the joint.

[0009] On the other hand, a possible configuration for preventing kinking or breakage at the joint while providing flexibility at the distal end and maintaining a desired hardness at the proximal end is to arrange an inner-layer tube on the inner circumferential surface of the outer-layer tube at a position a predetermined distance proximal to the distal end of the outer-layer tube. However, when a stylet of this configuration is inserted into the tube and then inserted into a living body along a guidewire, the guidewire may collide with a step caused by the thickness of the inner-layer tube, preventing the catheter assembly from being inserted properly.

[0010] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a stylet and catheter assembly that prevents kinking and breakage, provides flexibility at the tip end, maintains a desired hardness at the base end, and allows the catheter assembly to be suitably inserted along a guidewire. [Means for solving the problem]

[0011] A stylet that achieves the above object is a stylet that can be inserted into a catheter having a lumen through which blood can flow. The stylet includes an outer-layer tube extending in the axial direction, and an inner-layer tube that is disposed around the inner periphery of the outer-layer tube, has a hollow shape, and is harder than the outer-layer tube. The inner-layer tube has a tapered portion on the inner periphery of the distal end of the inner-layer tube, the diameter of which tapers toward the proximal end in the axial direction, and which guides a guide wire into the lumen of the inner-layer tube.

[0012] Furthermore, a catheter assembly that achieves the above object includes the above-mentioned stylet and a catheter configured so that the stylet can be inserted therein. [Effects of the Invention]

[0013] The stylet and catheter assembly configured as described above includes an outer-layer tube extending in the axial direction and an inner-layer tube disposed around the outer-layer tube and harder than the outer-layer tube, thereby preventing kinking and breakage while maintaining flexibility at the distal end and a desired hardness at the proximal end. Furthermore, because the inner-layer tube has a tapered portion, when the catheter assembly is inserted into a living body along a guidewire, the guidewire can pass through the lumen of the inner-layer tube along the tapered portion. Thus, a stylet and catheter assembly can be provided that prevents kinking and breakage while maintaining flexibility at the distal end and a desired hardness at the proximal end, and allows the catheter assembly to be inserted smoothly along a guidewire. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a system diagram showing an example of an extracorporeal circulation device to which a percutaneous catheter according to an embodiment of the present invention is applied. [Figure 2] FIG. 2 is a side view showing the state before the stylet according to the present embodiment is inserted into the catheter. [Figure 3] FIG. 1 is a side cross-sectional view showing a catheter. [Figure 4] FIG. 10 is a side view showing the state after the stylet according to the present embodiment has been inserted into the catheter. [Figure 5] FIG. 10 is a diagram for explaining the braiding angle of the first reinforcing body. [Figure 6] FIG. 10 is a diagram for explaining the braiding angle of the second reinforcing body. [Figure 7] FIG. 2 is a schematic cross-sectional view showing the configuration of a stylet according to the present embodiment. [Figure 8] FIG. 8 is a partial enlarged view of part A in FIG. 7. [Figure 9] 9 is a view corresponding to FIG. 8, but showing a case where no recess is provided in the outer tube. [Figure 10] 9 is a view corresponding to FIG. 8 in which the reduced diameter portion and the recessed portion of the outer tube are not provided. [Figure 11] FIG. 2 is a plan view showing the state before the stylet according to the embodiment is inserted into the double lumen catheter. [Figure 12] FIG. 1 is a side cross-sectional view showing a double lumen catheter. [Figure 13] FIG. 10 is a plan view showing the state after the stylet according to the embodiment has been inserted into the double lumen catheter. [Figure 14] FIG. 10 is a schematic diagram showing a state in which a catheter assembly according to a modified example is used. [Figure 15] FIG. 10 is a schematic diagram showing a state in which a catheter assembly according to a comparative example is used. [Figure 16] FIG. 10 is a view corresponding to FIG. 8 of a stylet according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following description does not limit the technical scope or meaning of terms described in the claims. Also, the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0016] FIG. 1 is a system diagram showing an example of an extracorporeal circulation device to which a percutaneous catheter according to an embodiment of the present invention is applied and which is used as percutaneous cardiopulmonary support (PCPS) to temporarily assist and substitute for the functions of the heart and lungs of a patient whose heart is weakened until cardiac function recovers.

[0017] The extracorporeal circulation device 1 can perform a veno-arterial (VA) procedure in which a pump is operated to withdraw blood from a patient's vein (vena cava), an artificial lung is used to exchange gases in the blood to oxygenate the blood, and the blood is then returned to the patient's artery (aorta). This extracorporeal circulation device 1 is a device that assists the heart and lungs. Hereinafter, the procedure of withdrawing blood from a patient, performing a prescribed treatment outside the body, and then returning the blood to the patient's body will be referred to as "extracorporeal circulation."

[0018] 1, the extracorporeal circulation device 1 has a circulation circuit for circulating blood. The circulation circuit has an oxygenator 2, a centrifugal pump 3, a drive motor 4 as a driving means for driving the centrifugal pump 3, a venous catheter (percutaneous catheter for blood removal) 5, an arterial catheter (catheter for blood supply) 6, and a controller 10 as a control unit.

[0019] A venous catheter (blood removal catheter) 5 is inserted through the femoral vein, and the tip of the venous catheter 5 is placed in the right atrium via the inferior vena cava. The venous catheter 5 is connected to the centrifugal pump 3 via a blood removal tube (blood removal line) 11. The blood removal tube 11 is a conduit for sending blood.

[0020] The arterial catheter (blood transfer catheter) 6 is inserted from the femoral artery.

[0021] When the drive motor 4 operates the centrifugal pump 3 in response to a command SG from the controller 10, the centrifugal pump 3 can draw blood from the blood removal tube 11, pass the blood through the oxygenator 2, and then return the blood to the patient P via the blood transfer tube (blood transfer line) 12.

[0022] The oxygenator 2 is disposed between the centrifugal pump 3 and the blood feed tube 12. The oxygenator 2 performs gas exchange (addition of oxygen and / or removal of carbon dioxide) with the blood. The oxygenator 2 is, for example, a membrane oxygenator, but a hollow fiber membrane oxygenator is particularly preferred. Oxygen gas is supplied to the oxygenator 2 from an oxygen gas supply unit 13 via a tube 14. The blood feed tube 12 is a conduit connecting the oxygenator 2 and the arterial catheter 6.

[0023] Pipes made of highly transparent, elastically deformable, flexible synthetic resin, such as polyvinyl chloride resin or silicone rubber, can be used for the blood removal tube 11 and the blood transfer tube 12. In the blood removal tube 11, blood, which is liquid, flows in the direction V1, and in the blood transfer tube 12, blood flows in the direction V2.

[0024] 1, an ultrasonic air bubble detection sensor 20 is disposed midway through the blood removal tube 11. A fast clamp 17 is disposed midway through the blood transfer tube 12.

[0025] The ultrasonic air bubble detection sensor 20 detects air bubbles that have been introduced into the circulation circuit during extracorporeal circulation due to erroneous operation of the three-way stopcock 18, tube damage, or the like. When the ultrasonic air bubble detection sensor 20 detects the presence of air bubbles in the blood being sent into the blood removal tube 11, the ultrasonic air bubble detection sensor 20 sends a detection signal to the controller 10. Based on this detection signal, the controller 10 issues an alarm and either reduces the rotation speed of the centrifugal pump 3 or stops the centrifugal pump 3. Furthermore, the controller 10 commands the fast clamp 17 to immediately close the blood transfer tube 12 with the fast clamp 17, thereby preventing air bubbles from being sent into the body of the patient P. The controller 10 controls the operation of the extracorporeal circulation device 1 to prevent air bubbles from entering the body of the patient P.

[0026] A pressure sensor is provided in the tube 11 (12, 19) of the circulation circuit of the extracorporeal circulation apparatus 1. The pressure sensor can be attached to, for example, any one or all of the following: attachment position A1 of the blood removal tube 11, attachment position A2 of the blood transfer tube 12 of the circulation circuit, or attachment position A3 of the connection tube 19 connecting the centrifugal pump 3 and the oxygenator 2. This allows the pressure sensor to measure the pressure inside the tube 11 (12, 19) when extracorporeal circulation is being performed for the patient P by the extracorporeal circulation apparatus 1. The attachment position of the pressure sensor is not limited to the above-mentioned attachment positions A1, A2, and A3, and it can be attached to any position in the circulation circuit.

[0027] Next, with reference to Figures 2 to 6, the configuration of a percutaneous catheter (hereinafter referred to as "catheter") 30 through which a stylet 50 according to an embodiment of the present invention is inserted will be described. Figures 2 to 6 are diagrams provided for explaining the configuration of catheter 30. This catheter 30 is used as the venous catheter (catheter for blood removal) 5 in Figure 1. Note that the configuration of catheter 30 described below is one example, and the catheter through which stylet 50 according to this embodiment is inserted is not limited to the following configuration.

[0028] As shown in FIG. 2 , the catheter 30 has a catheter tube 31 with a first side hole 63 and a second side hole 46, a distal tip 41 disposed at the distal end of the catheter tube 31 and having a through-hole 47, a clamping tube 34 disposed on the proximal end side of the catheter tube 31, a catheter connector 35 connecting the catheter tube 31 and the clamping tube 34, and a lock connector 36.

[0029] In this specification, the side inserted into the living body is referred to as the "distal end" or "distal side," and the side operated by the surgeon is referred to as the "proximal end" or "proximal side." The distal end refers to a certain range including the distal end (the most extreme end) and its surroundings, and the proximal end refers to a certain range including the proximal end (the most proximal end) and its surroundings.

[0030] 3, the catheter 30 has a lumen 30A that penetrates from the distal end to the proximal end. The through-hole 47 provided in the distal tip 41 and the first and second side holes 63 and 46 provided in the catheter tube 31 are configured to be positioned at different blood removal targets within a living body to enable efficient blood removal.

[0031] When inserting the catheter 30 into a living body, a stylet 50 shown in Figure 2 is used. The stylet 50 is inserted into the lumen 30A of the catheter 30, and the catheter 30 and stylet 50 are previously integrated together before insertion into the living body. In this specification, the structure in which the catheter 30 and stylet 50 are integrated together is referred to as a catheter assembly 7.

[0032] The following describes each component of the catheter 30. However, the configuration of the catheter 30 is not limited to the following.

[0033] As shown in FIG. 2, the catheter tube 31 has an expansion section 32 and a shaft section 33 connected to the proximal end side of the expansion section 32.

[0034] The expansion section 32 is configured to be more flexible than the shaft section 33. The expansion section 32 is also configured to have larger outer and inner diameters than the shaft section 33.

[0035] The lengths of the expansion section 32 and the shaft section 33 are configured to be lengths necessary for positioning the through-hole 47 of the distal tip 41 and the first side hole 63 and second side hole 46 of the catheter tube 31 at the desired target for blood removal. The length of the expansion section 32 can be, for example, 20 to 40 cm, and the length of the shaft section 33 can be, for example, 20 to 30 cm.

[0036] In this embodiment, blood is removed from two locations: the right atrium and the inferior vena cava. The catheter 30 is inserted and placed in the living body so that the through-hole 47 of the distal tip 41 and the second side hole 46 of the catheter tube 31 are positioned in the right atrium, and the first side hole 63 of the catheter tube 31 is positioned in the inferior vena cava.

[0037] With the through hole 47, the second side hole 46, and the first side hole 63 positioned in the blood removal target, the expansion portion 32 is positioned in the inferior vena cava, which is a relatively large blood vessel, and the shaft portion 33 is positioned in the femoral vein, which is a relatively small blood vessel.

[0038] Furthermore, when the stylet 50 is inserted into the lumen 30A of the catheter 30, the highly elastic expansion section 32 stretches in the axial direction, reducing its outer and inner diameters, as shown in Figure 4. At this time, the outer diameter of the expansion section 32 becomes approximately the same as the outer diameter of the shaft section 33. Because the catheter 30 is inserted into the living body with the expansion section 32 stretched in the axial direction and its outer and inner diameters reduced, the catheter 30 can be inserted minimally invasively.

[0039] Furthermore, after the catheter 30 is placed in the living body, when the stylet 50 is removed from the lumen 30A of the catheter 30, the expansion section 32 contracts from its axially extended state, increasing its inner diameter. Here, the expansion section 32 is placed in the inferior vena cava, which is a relatively large blood vessel. Therefore, the outer diameter of the expansion section 32 can be increased, and therefore the inner diameter can be increased.

[0040] Here, the pressure loss inside the expansion section 32 is calculated as the total length of the expansion section 32 multiplied by the (average) cross-sectional area of ​​the passage. That is, by increasing the inner diameter of the expansion section 32, the pressure loss inside the expansion section 32 is reduced. When the pressure loss inside the expansion section 32 is reduced, the flow rate of blood flowing through the circulation circuit increases. For this reason, in order to obtain a sufficient amount of blood circulation, it is necessary to increase the inner diameter of the expansion section 32.

[0041] On the other hand, if the wall thickness is approximately constant, increasing the inner diameter of the expansion section 32 and the shaft section 33 will increase the outer diameter, which will increase the burden on the patient when inserting the catheter 30 into the body and hinder minimally invasive procedures.

[0042] From the above viewpoints, the inner diameter of the extension portion 32 may be, for example, 9 to 11 mm, and the inner diameter of the shaft portion 33 may be, for example, 4 to 8 mm. The thickness of the extension portion 32 and the shaft portion 33 may be, for example, 0.4 to 0.5 mm.

[0043] 2, the distal end of the expansion section 32 preferably has a tapered section that gradually narrows from the center of the expansion section 32 toward the distal end in the axial direction, so that the inner diameter of the distal end of the expansion section 32 is continuous with the inner diameter of the distal tip 41 disposed on the distal end side.

[0044] As shown in FIG. 5, the expansion portion 32 has a first reinforcing body 321 made of wires W braided to cross each other, and a first resin layer 322 provided to cover the first reinforcing body 321.

[0045] As shown in FIG. 6, the shaft portion 33 has a second reinforcing body 331 made of wires W braided to cross each other, and a second resin layer 332 provided to cover the second reinforcing body 331.

[0046] The first reinforcing body 321 is configured by braiding a wire W so as to have a braiding angle θ1, as shown in Fig. 5. The second reinforcing body 331 is configured by braiding a wire W so as to have a braiding angle θ2, as shown in Fig. 6.

[0047] In this specification, the braiding angles θ1 and θ2 are defined as the interior angles in the axial direction among the angles formed by the intersecting wires W, as shown in FIGS.

[0048] 5 and 6, the braiding angle θ1 of the first reinforcing body 321 is configured to be smaller than the braiding angle θ2 of the second reinforcing body 331. Therefore, the inclination angle of the wires W constituting the first reinforcing body 321 with respect to the axial direction is smaller compared to when the braiding angle of the first reinforcing body 321 is larger than the braiding angle of the second reinforcing body 331. Note that the braiding angle θ1 of the first reinforcing body 321 may be configured to be larger than the braiding angle θ2 of the second reinforcing body 331.

[0049] Here, as the expansion section 32 expands in the axial direction, the wire W constituting the first reinforcing body 321 of the expansion section 32 deforms so that the inclination angle with respect to the axial direction gradually decreases. Then, when the inclination angle with respect to the axial direction of the wire W constituting the first reinforcing body 321 of the expansion section 32 becomes approximately zero, the expansion of the expansion section 32 in the axial direction is restricted.

[0050] Therefore, by configuring the braiding angle θ1 of the first reinforcement body 321 to be smaller than the braiding angle θ2 of the second reinforcement body 331, the extension distance along the axial direction of the expansion section 32 associated with inserting the stylet 50 into the catheter 30 is shorter than when the braiding angle of the first reinforcement body 321 is larger than the braiding angle of the second reinforcement body 331.

[0051] The braiding angle θ1 of the first reinforcing member 321 is not particularly limited, but is in the range of 100 degrees to 120 degrees. The braiding angle θ2 of the second reinforcing member 331 is not particularly limited, but is in the range of 130 degrees to 150 degrees. By making the braiding angle θ2 of the second reinforcing member 331 larger than the braiding angle θ1 of the first reinforcing member 321 in this way, the kink resistance of the second reinforcing member 331 can be improved. This allows the catheter 30 to be suitably inserted into the living body through the femoral vein, which has a complex structure.

[0052] 5 and 6, the first reinforcing body 321 of the expansion section 32 is braided more loosely than the second reinforcing body 331 of the shaft section 33. This configuration makes the expansion section 32 softer than the shaft section 33, thereby increasing its stretchability.

[0053] In this embodiment, the wire W is made of a shape-memory material such as a known shape-memory metal or shape-memory resin. Examples of shape-memory metals that can be used include titanium-based alloys (Ni-Ti, Ti-Pd, Ti-Nb-Sn, etc.) and copper-based alloys. Examples of shape-memory resins that can be used include acrylic resins, transisoprene polymers, polynorbornene, styrene-butadiene copolymers, and polyurethanes.

[0054] Because the wire W is made of a shape memory material, the axial contraction distance of the expansion portion 32 associated with removing the stylet 50 from the catheter 30 is the same as the axial extension distance of the expansion portion 32 associated with inserting the stylet 50 through the catheter 30.

[0055] The diameter of the wire W is preferably 0.1 mm to 0.2 mm.

[0056] By making the wire diameter of the wire W 0.1 mm or more, the wire W can suitably exhibit its function as a reinforcing member that improves strength.

[0057] On the other hand, by setting the wire diameter of the wire W to 0.2 mm or less, it is possible to reduce the outer diameter of the expansion section 32 while increasing the inner diameter, thereby reducing the burden on the patient's body and reducing pressure loss when inserting the catheter 30. In this embodiment, the cross section of the wire W is circular, but is not limited to this and may be rectangular, square, elliptical, or the like.

[0058] The first resin layer 322 of the extension portion 32 is made of a softer material with lower hardness than the second resin layer 332 of the shaft portion 33. With this configuration, the extension portion 32 can be made softer than the shaft portion 33, and the stretchability can be improved.

[0059] The first and second resin layers 322, 332 can be formed using vinyl chloride, silicone, polyethylene, nylon, urethane, polyurethane, fluororesin, thermoplastic elastomer resin, or the like, or using a composite material of these.

[0060] Silicone material has the advantage of being highly biocompatible and soft, making it less likely to damage blood vessels. Polyethylene material is soft yet hard enough to withstand pressure. Moreover, polyethylene material has biocompatibility comparable to that of silicone material. Polyethylene material is harder than silicone, making it easier to insert into thin blood vessels. Polyurethane material also has the advantage of becoming soft after insertion. Applicable materials can be used for the first and second resin layers 322, 332, taking advantage of the advantages of these materials.

[0061] Alternatively, a hydrophilic coating can be applied to the polyurethane material. This makes the tube surface smooth, making it easier to insert into the blood vessel and less likely to damage the blood vessel wall. It is also expected that blood and protein will not adhere to the tube, preventing the formation of blood clots.

[0062] The method for forming the extension portion 32 and the shaft portion 33 is not particularly limited, but they can be formed by, for example, dip coating (immersion method), insert molding, etc. It is sufficient that at least the outer surfaces of the reinforcing bodies 321 and 331 are covered with the resin layers 322 and 332.

[0063] As shown in Figure 2, the expansion section 32 has second side holes 46. As shown in Figure 2, multiple second side holes 46 (four in Figure 2) are provided along the axial direction. It is preferable that multiple second side holes 46 are also provided in the circumferential direction. The second side holes 46 function as blood removal holes.

[0064] As shown in FIG. 2, the shaft portion 33 has a first side hole 63. The first side hole 63 functions as a blood removal hole. It is preferable to have a plurality of first side holes 63 in the circumferential direction. In the present embodiment, four first side holes 63 are provided in the shaft portion 33 in the circumferential direction. As a result, even if one first side hole 63 is adsorbed to the blood vessel wall and blocked during blood removal, blood removal can still be performed through the other first side holes 63, and blood circulation can be stabilized.

[0065] 2 to 4, the distal tip 41 is disposed at the distal end of the expansion section 32. The distal tip 41 has a tapered shape with a diameter that gradually decreases toward the distal end.

[0066] The distal tip 41 has a flat receiving surface 48 formed on the inside thereof, which comes into contact with a flat surface 51D of a stylet 50 that is used prior to insertion of the catheter 30 into a living body.

[0067] As shown in Figure 3, the distal tip 41 is configured to accommodate the distal end of the wire W. The distal tip 41 has a through-hole 47. The through-hole 47 functions as a hole for removing blood. The through-hole 47 of the distal tip 41 forms part of the lumen 30A of the catheter 30. The distal tip 41 can be made of, for example, urethane.

[0068] As shown in Figures 2 to 4, the clamping tube 34 is provided on the proximal end side of the shaft portion 33. A lumen through which the stylet 50 can be inserted is provided inside the clamping tube 34. The clamping tube 34 can be made of the same material as the catheter tube 31.

[0069] 2 and 4, catheter connector 35 connects shaft portion 33 and clamp tube 34. Inside catheter connector 35, a lumen is provided through which stylet 50 can be inserted.

[0070] As shown in Figures 2 to 4, lock connector 36 is connected to the proximal end side of clamp tube 34. A lumen through which stylet 50 can be inserted is provided inside lock connector 36. A male screw portion 36A having a screw thread is provided on the outer surface of the proximal end side of lock connector 36.

[0071] Next, the configuration of the stylet 50 according to this embodiment will be described with reference to Figures 7 to 10. Figures 7 and 8 are diagrams illustrating the configuration of the stylet 50 according to this embodiment. Figure 9 is a diagram corresponding to Figure 8, but showing a case in which no recess is provided in the outer tube. Figure 10 is a diagram corresponding to Figure 8, but showing a case in which neither a reduced diameter section nor a recess is provided in the outer tube.

[0072] As shown in FIGS. 7 and 8, the stylet 50 has an outer tube 51 extending in the axial direction and an inner tube 52 disposed on the inner periphery of the outer tube 51 .

[0073] The outer diameter of the outer tube 51 is configured to be the same as the inner diameter of the shaft portion 33. Note that "same as the inner diameter of the shaft portion 33" does not mean exactly the same, but also includes some degree of error. The outer tube 51 has a lumen 55 in which the inner tube 52 is disposed.

[0074] As shown in Figure 7, the distal end 51A of the outer tube 51 is tapered so that it gradually becomes smaller toward the distal end. With this configuration, the outer periphery of the distal end 51A of the outer tube 51 has a gently tapered shape, so that when the stylet 50 is inserted into the catheter 30 and integrated with it, the catheter 30 tapers to match the shape of the distal end 51A. This improves the insertability of the catheter 30 into a living body.

[0075] 7 and 8, a recess 51B recessed radially outward is formed on the inner peripheral surface of the outer tube 51. The inner diameter of the recess 51B of the outer tube 51 is slightly larger than the outer diameter of the inner tube 52. The inner tube 52 is fixed to the outer tube 51 with the tip 52C of the reduced diameter portion 52B of the inner tube 52 abutting against the tip 51C of the recess 51B of the outer tube 51.

[0076] As shown in FIG. 2, the distal end of the outer tube 51 has a flat surface 51D with which the receiving surface 48 of the distal tip 41 abuts.

[0077] The total axial length of the outer tube 51 is longer than the total axial length of the catheter 30 before the expansion section 32 is extended. In addition, the total axial length of the outer tube 51 is configured to be the same as the total axial length of the catheter 30 after the expansion section 32 is extended.

[0078] The outer diameter of the outer tube 51 is, but is not limited to, 4.0 to 9.0 mm. The inner diameter of the outer tube 51 is, but is not limited to, 1.2 to 7.0 mm. The recess 51B formed on the inner peripheral surface of the outer tube 51 has a recess depth C1, but is not limited to, 0.9 to 3.4 mm. The length L1 (see FIG. 7) from the tip 51C of the recess 51B of the outer tube 51 to the flat surface 51D of the outer tube 51 is, but is not limited to, 50 to 150 mm.

[0079] The outer tube 51 is a long body having a relatively high rigidity. The material for the outer tube 51 is not particularly limited, but may be the same as that for the first and second resin layers 322 and 332 described above.

[0080] The inner tube 52 is provided on the inner periphery of the outer tube 51 .

[0081] 8, the inner-layer tube 52 has a lumen 52A through which a guidewire GW can be inserted. The outer-layer tube 51 and the inner-layer tube 52 are guided by the guidewire GW and inserted into the living body together with the catheter 30.

[0082] The inner layer tube 52 is configured so that the outer diameter is uniform along the axial direction.

[0083] As shown in Figures 7 and 8, the inner-layer tube 52 has a tapered portion 52B on the inner circumferential surface of the distal end 52C, the diameter of which tapers toward the proximal end. In this embodiment, as shown in Figure 8, the tapered portion 52B has a linear shape. The taper angle θ of the tapered portion 52B is not particularly limited, but is preferably 80 degrees or less. By setting the taper angle to 80 degrees or less, when the catheter assembly 7 is inserted into a living body along the guidewire GW, the guidewire GW is guided along the tapered portion 52B into the lumen 52A of the inner-layer tube 52 and can pass through the lumen 52A of the inner-layer tube 52.

[0084] As shown in Fig. 8, the distal end 52C of the reduced diameter section 52B has a predetermined thickness D1. As shown in Fig. 8, the thickness D1 is preferably approximately the same as the recess amount C1 of the recess 51B formed on the inner circumferential surface of the outer-layer tube 51. With this configuration, no step is formed at the distal end 52C of the inner-layer tube 52. Therefore, when the catheter assembly 7 is inserted into a living body along the guidewire GW, the guidewire GW can pass through the lumen 52A of the inner-layer tube 52 along the reduced diameter section 52B. Note that the above effect can be achieved even if the recess amount C1 is greater than the thickness D1.

[0085] 9, if the outer-layer tube 151 does not have a recess 51B, a step is formed corresponding to the thickness D1 of the distal end 52C of the tapered portion 52B. Therefore, when the catheter assembly 7 is inserted into a living body along the guidewire GW, the guidewire GW may come into contact with the distal end 52C of the tapered portion 52B, potentially preventing the catheter assembly from being inserted properly. In contrast, with the stylet 50 of this embodiment, the outer-layer tube 51 has a recess 51B formed therein, as shown in FIG. 8, allowing the catheter assembly 7 to be inserted properly. Note that a configuration in which the outer-layer tube 151 does not have a recess 51B is considered within the scope of the present invention because it can prevent the guidewire GW from colliding with the inner-layer tube 52 compared to a configuration in which the tapered portion 52B, as described below, is not present.

[0086] 10 discloses, as a comparative example, a catheter assembly 90 having an inner-layer tube 952 without a reduced diameter section 52B and an outer-layer tube 151 without a recess 51B. When the reduced diameter section 52B is not provided as in the catheter assembly 90 of the comparative example, a step is formed corresponding to the thickness of the inner-layer tube 952. As a result, when the catheter assembly 90 is inserted into a living body along the guidewire GW, the guidewire GW comes into contact with the inner-layer tube 952, making it difficult to insert the catheter assembly 90.

[0087] The outer diameter of the inner layer tube 52 is not particularly limited, but is 1.3 to 7.0 mm. The inner diameter of the inner layer tube 52 is not particularly limited, but is 1.1 to 5.0 mm.

[0088] The inner-layer tube 52 is a relatively rigid, elongated tube. The inner-layer tube 52 is made of a harder material than the outer-layer tube 51. The material for the inner-layer tube 52 is not particularly limited, but may be the same as that for the first and second resin layers 322 and 332 described above. This configuration makes it possible to increase the rigidity of the proximal end of the stylet 50 while maintaining a soft distal end. This prevents damage to biological tissue when the catheter assembly 7 is inserted into a living body, and provides the rigidity that enables the force of the hand to be transmitted to the distal tip 41 when the catheter assembly 7 is pushed distally.

[0089] As shown in FIG. 2, the stylet 50 further includes a stylet hub 53 to which the proximal ends of the outer tube 51 and the inner tube 52 are fixed, and a screw ring 54 provided at the distal end of the stylet hub 53.

[0090] The stylet hub 53 is provided at the proximal ends of the outer tube 51 and the inner tube 52 and is configured to be graspable. After the catheter 30 has been placed in the living body, the stylet 50 is removed from the catheter 30 by pulling the stylet hub 53 toward the proximal end.

[0091] The screw ring 54 has a female thread portion (not shown) with a screw groove formed on the inner surface of the lumen. The stylet 50 can be attached to the catheter 30 by screwing the female thread portion of the screw ring 54 into the male thread portion 36A of the lock connector 36.

[0092] <How to use the stylet> Next, a method of using the above-described stylet 50 will be described.

[0093] First, the inner tube 52 is fixed to the outer tube 51 to manufacture the stylet 50. Then, the stylet 50 is inserted into the lumen 30A of the catheter 30. The stylet 50 passes through the shaft portion 33 and the expansion portion 32 in that order, and the flat surface 51D of the outer tube 51 of the stylet 50 abuts against the receiving surface 48 of the distal tip 41.

[0094] 2, the overall axial length of the outer tube 51 is longer than the overall axial length of the catheter 30 before the expansion section 32 is extended. Therefore, with the flat surface 51D of the outer tube 51 of the stylet 50 abutting against the receiving surface 48 of the distal tip 41, the expansion section 32 is pressed toward the distal end.

[0095] The distal end of the expansion section 32 is then pulled toward the distal end. As a result, the catheter 30 receives a force that stretches it in the axial direction, and the expansion section 32, which has a relatively high degree of elasticity within the catheter 30, stretches in the axial direction.

[0096] Thereafter, the stylet 50 is attached to the catheter 30 by screwing the female thread portion of the screw ring 54 into the male thread portion 36A provided on the lock connector 36 of the catheter.

[0097] Next, the catheter 30 with the stylet 50 inserted therethrough is inserted along the guidewire GW, which has been inserted into a target site in the living body beforehand. With the stylet 50 according to this embodiment, the inner-layer tube 52 is provided with a reduced-diameter section 52B, and the outer-layer tube 51 is provided with a recess 51B, allowing the catheter assembly 7 to be suitably inserted along the guidewire GW. Furthermore, because the stylet 50 is inserted through the catheter 30, the outer diameter of the expansion section 32 is substantially the same as the outer diameter of the shaft section 33, allowing the catheter 30 to be inserted into the living body in a minimally invasive manner, thereby minimizing the strain on the patient's body.

[0098] The catheter 30 is inserted and left in the living body until the through-hole 47 of the distal tip 41 and the second side hole 46 of the catheter tube 31 are positioned in the right atrium, and the first side hole 63 of the catheter tube 31 is positioned in the inferior vena cava. With the through-hole 47, the first side hole 63, and the second side hole 46 positioned in the blood removal target, the expansion section 32 is positioned in the inferior vena cava, which is a relatively large blood vessel, and the shaft section 33 is positioned in the femoral vein, which is a relatively small blood vessel.

[0099] Next, the stylet 50 and guidewire are removed from the catheter 30. At this time, the stylet 50 and guidewire are first pulled back to the clamping tube 34 of the catheter 30 and clamped with forceps (not shown), and then completely removed from the catheter 30. By removing the stylet 50 from the lumen of the catheter 30, the catheter 30 is released from the axially stretching force that the catheter 30 was receiving from the stylet 50. As a result, the expansion section 32 contracts in the axial direction, and the inner diameter of the expansion section 32 increases. This reduces pressure loss within the expansion section 32 and ensures the required flow rate of liquid.

[0100] Next, the lock connector 36 of the catheter 30 is connected to the blood removal tube 11 of the extracorporeal circulation device shown in Figure 1. After confirming that the connection of the blood supply catheter is complete, the clamp on the clamping tube 34 is released to start extracorporeal circulation.

[0101] After the extracorporeal circulation is completed, the catheter 30 is removed from the blood vessel, and the insertion site is surgically repaired for hemostasis, if necessary.

[0102] As described above, the stylet 50 according to this embodiment is configured to be insertable into a catheter 30 having a lumen 30A through which blood can flow. The stylet 50 comprises an outer-layer tube 51 extending in the axial direction and an inner-layer tube 52 that is hollow and rigid relative to the outer-layer tube 51, and is disposed around the inner periphery of the outer-layer tube 51. The inner-layer tube 52 has a tapered portion 52B on the inner periphery of the distal end of the inner-layer tube 52, the diameter of which tapers toward the proximal end in the axial direction. The stylet 50 configured in this manner, comprising the outer-layer tube 51 extending in the axial direction and the inner-layer tube 52 that is disposed around the inner periphery of the outer-layer tube 51 and is rigid relative to the outer-layer tube 51, allows for flexibility at the distal end and a desired rigidity at the proximal end while preventing kinking and breakage. Furthermore, because the inner-layer tube 52 has a reduced diameter section 52B, when the catheter assembly 7 is inserted into a living body along the guidewire GW, the guidewire GW can pass through the lumen 52A of the inner-layer tube 52 along the reduced diameter section 52B. As described above, a stylet 50 can be provided that prevents kinking and breakage, provides flexibility at the distal end, maintains hardness at the proximal end, and allows the catheter assembly 7 to be suitably inserted along the guidewire GW.

[0103] Furthermore, with the stylet 50 configured as described above, the range of flexibility of the tip of the stylet 50 can be appropriately controlled by appropriately changing the axial position of the tip of the inner tube 52 relative to the outer tube 51.

[0104] The outer-layer tube 51 has a recess 51B on its inner circumferential surface that is recessed radially outward, and the inner-layer tube 52 is fixed to the outer-layer tube 51 with the distal end 52C of the inner-layer tube 52 abutting against the distal end 51C of the recess 51B of the outer-layer tube 51. The stylet 50 configured in this manner allows the catheter assembly 7 to be inserted more efficiently along the guidewire GW.

[0105] Furthermore, the reduced diameter portion 52B has a linear shape. According to the stylet 50 configured in this manner, the reduced diameter portion 52B can be easily formed.

[0106] <Modified Catheter> Next, modified examples of the catheter will be described. In the above-described embodiment, the stylet 50 is applied to a catheter 30 having one lumen 30A. However, it can also be used for a catheter 60 having double lumens, as shown in Figures 11 to 13. The configuration of a catheter 60 having double lumens will be described below with reference to Figures 11 to 13.

[0107] The catheter 60 is a so-called double lumen catheter, which is capable of both blood feeding and blood removal at the same time. Therefore, in this embodiment, the extracorporeal circulation device of Fig. 1 does not use two catheters, a venous catheter (blood removal catheter) 5 and an arterial catheter (blood feed catheter) 6, but instead uses only one catheter 60 to perform the procedure.

[0108] As shown in Figures 11 and 12, the catheter 60 has a double-tube structure in which a third tube 161 having a first lumen 61 communicating with a blood feed side hole 163 is disposed in the inner cavity of the shaft portion 133.

[0109] The catheter 60 enables veno-venous (VV) extracorporeal blood circulation using an artificial lung, in which blood is drawn from the patient's vein (vena cava) by operating the pump of the extracorporeal circulation device, gas exchange is carried out in the blood using an artificial lung to oxygenate the blood, and the blood is then returned to the patient's vein (vena cava).

[0110] 11 to 13, the catheter 60 has an expansion section 32, a shaft section 133, a distal tip 41 disposed at the distal end of the expansion section 32, and a third tube 161 disposed in the lumen of the shaft section 133. The configurations of the expansion section 32 and the distal tip 41 are the same as those of the catheter 30 of the first embodiment, and therefore description thereof will be omitted.

[0111] As shown in FIG. 12, the catheter 60 has a first lumen 61 that functions as a blood feed channel and a second lumen 62 that functions as a blood removal channel.

[0112] The first lumen 61 is formed in the inner cavity of the third tube 161. The second lumen 62 is formed in the inner cavities of the expansion portion 32 and the shaft portion 133, and passes through from the distal end to the proximal end.

[0113] The shaft portion 133 is provided with a blood feed side hole 163 that communicates with the first lumen 61, which is a blood feed path.

[0114] The shaft portion 133 is provided with a blood removal side hole 164 that communicates with the second lumen 62, which is the blood removal path.

[0115] The blood feed side hole 163 and the blood removal side hole 164 are configured in an oval shape.

[0116] The third tube 161 is inserted into the second lumen 62 from the base end side of the shaft portion 133 and is connected to the blood feed side hole 163 .

[0117] The blood feed side hole 163 is placed at a blood feed target inside the living body, and blood that has been oxygenated by the artificial lung is fed into the living body via the blood feed side hole 163.

[0118] The through hole 47 of the distal tip 41, the second side hole 46 of the expansion section 32, and the blood removal side hole 164 of the shaft section 133 are configured to enable efficient blood removal when placed at different blood removal targets within a living body. Furthermore, even if the through hole 47, the second side hole 46, or the blood removal side hole 164 is adsorbed to the blood vessel wall and blocked, blood removal can be performed from the unblocked hole, allowing stable extracorporeal circulation.

[0119] In this embodiment, the catheter 60 is inserted through the internal jugular vein in the neck, passes through the superior vena cava and the right atrium, and its tip is placed in the inferior vena cava. The target for blood supply is the right atrium, and the targets for blood removal are the superior vena cava and the inferior vena cava.

[0120] As shown in FIG. 13 , with the stylet 50 inserted, the catheter 60 is inserted and placed in the living body so that the through hole 47 of the distal tip 41 and the second side hole 46 of the expansion section 32 are positioned in the inferior vena cava, and the blood removal side hole 164 of the shaft section 133 is positioned in the internal jugular vein.

[0121] The expansion section 32 is configured to have a larger inner diameter than the shaft section 133. With the through-hole 47, the second side hole 46, and the blood removal side hole 164 positioned in the blood removal target, the expansion section 32 is positioned in the inferior vena cava, which is a relatively large blood vessel, and the shaft section 133 is positioned in the femoral vein, which is a relatively small blood vessel.

[0122] 12, lock connector 136 has a first lock connector 137 that communicates with first lumen 61, and a second lock connector 138 that is provided in parallel to first lock connector 137 and communicates with second lumen 62. Lock connector 136 is a Y-shaped Y connector formed by first lock connector 137 branching off from second lock connector 138.

[0123] The first lock connector 137 is connected to the base end of the third tube 161. The second lock connector 138 is coaxially connected to the base end of the shaft portion 133. A blood transfer tube (blood transfer line) is connected to the first lock connector 137, and a blood removal tube (blood removal line) is connected to the second lock connector 138.

[0124] As described above, the catheter 60 according to this embodiment can perform both the functions of blood removal and blood transfer with a single catheter. <Modifications of Catheter Assembly>

[0125] Next, the configuration of a catheter assembly 8 according to a modified example will be described with reference to Figures 14 and 15. The catheter assembly 7 according to the above-described embodiment is employed as a so-called dilation catheter in which the flat surface 51D of the outer tube 51 of the stylet 50 abuts against the receiving surface 48 of the distal tip 41, thereby extending the dilation section 32 of the catheter 30.

[0126] In contrast, a catheter assembly 8 according to a modified example has a configuration in which a stylet 250 protrudes from the tip of the catheter 30, as shown in Fig. 14. In this configuration, the tip of the outer tube 51 does not need to have a flat surface 51D, and may have a shape without edges.

[0127] Here, for example, if the stylet 81 is configured to be uniformly relatively hard along the axial direction, when the catheter assembly 80 is inserted along the guidewire GW, the stylet 81 will be difficult to bend and will have poor followability to the guidewire GW, which may result in unintended contact with a blood vessel, as shown in Fig. 15. In contrast, the catheter assembly 8 according to the modified example uses a stylet 250 that is flexible on the distal end side and has a desired hardness on the proximal end side, so that the stylet 250 is easy to bend and has good followability to the guidewire GW, as shown in Fig. 14, thereby reducing the risk of damaging a blood vessel.

[0128] At this time, with the stylet 250 inserted into the catheter 30, it is preferable that the tip of the inner-layer tube 52 be positioned closer to the base end than the tip of the catheter 30. This configuration allows the surgeon to grasp the base end side, which has a higher hardness and where the inner-layer tube 52 is positioned, making the surgery easier.

[0129] The catheter according to the present invention has been described above through the embodiments, but the present invention is not limited to the configurations described in the embodiments and modifications, and can be modified as appropriate based on the claims.

[0130] For example, in the above-described embodiment, the reduced diameter section 52B has a linear shape. However, the reduced diameter section 152B may have a curved shape that is convex toward the proximal end, as shown in Fig. 16. With a stylet 150 configured in this manner, when the catheter assembly is inserted into a living body along the guidewire GW, the guidewire GW is suitably guided along the reduced diameter section 152B into the lumen 52A of the inner-layer tube 152.

[0131] Furthermore, the material constituting the wire W is not limited to a shape-memory material as long as it has the restoring force to return to its original shape after being deformed and has the function of reinforcing the resin layer, and can be made of, for example, a known elastic material. [Explanation of symbols]

[0132] 7, 8 Catheter assembly, 30, 60, 230 catheters (percutaneous catheters), 30A catheter lumen, 50, 150, 250 stylet, 51, 151 outer layer tube; 51B recess, 51C tip of recess; 52, 152 inner layer tube; 52B, 152B reduced diameter part, 52C Tip of inner layer tube.

Claims

1. A stylet configured to be insertable into a catheter having a lumen through which blood can flow, an outer tube extending in an axial direction; an inner tube disposed on the inner periphery of the outer tube, having a hollow shape and being harder than the outer tube; The inner tube has a reduced diameter portion on the inner peripheral surface of the distal end of the inner tube, the reduced diameter portion decreasing in diameter toward the proximal end in the axial direction and guiding a guide wire into the lumen of the inner tube.

2. the outer tube has a recessed portion recessed radially outward on at least a portion of an inner circumferential surface of the outer tube, The stylet according to claim 1 , wherein the inner tube is fixed relative to the outer tube with the tip end of the inner tube abutting against the tip end of the recess of the outer tube.

3. The stylet according to claim 1 or 2, wherein the reduced diameter portion has a linear shape.

4. The stylet according to claim 1 or 2, wherein the reduced diameter section has a curved shape that is convex toward the base end side.

5. The stylet according to any one of claims 1 to 4, a catheter into which the stylet can be inserted.

6. With the stylet inserted into the catheter, 6. The catheter assembly according to claim 5, wherein the distal end of the inner layer tube is located closer to the proximal end than the distal end of the catheter.

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