JP2008011867A - Dilator, dilator manufacturing method, and sheath introducer - Google Patents

Abstract

A dilator that has a smaller puncture resistance and can be smoothly inserted into a body by a surgeon and a sheath introducer including the dilator.
A dilator having a lumen that penetrates from a proximal end side to a distal end side, wherein a tube portion on the proximal end side, and a taper that is tapered from the distal end of the tube portion toward the distal end side are formed. A tapered portion and a distal end portion formed so as to extend from the distal end of the tapered portion toward the distal end side. The distal end portion narrows toward the distal end side and is inclined at the distal end portion of the tapered portion. A small taper having a smaller inclination angle is formed.
[Selection] Figure 2

Description

  The present invention relates to a dilator used when a device such as a catheter is inserted into a blood vessel such as a blood vessel, a method of manufacturing the dilator, and a sheath introducer including the dilator.

  When a device such as a catheter is inserted into a vessel in the body, a sheath introducer is generally used to secure an approach path for the catheter or the like from the body surface into the vessel. The sheath introducer includes a sheath for connecting the inside of the blood vessel and the outside of the body, and a dilator for passing through the sheath and expanding a hole formed in the body surface.

  For example, FIG. 1 shows a conventional sheath introducer 200. As shown in FIG. 1A, the sheath introducer 200 includes a dilator 70 and a sheath 80, and has a lumen that penetrates from the proximal end side to the distal end side. As shown in FIG. 1A, the dilator 70 includes a dilator tip 74, a dilator tube 72, and a dilator housing 76. The sheath 80 is provided on the proximal end side of the tubular sheath tube 82, the sheath tube 82, a sheath housing 86 having an opening on the proximal end side, and a chemical solution injection connected to the side portion of the sheath housing portion 86. A tube 88 and a stopcock 89 are provided. In the present specification, the right side in FIG. 1 is the front end side, and the left side is the base end side.

  As shown in FIG. 1, the sheath introducer 200 is used in a state where the dilator 70 is inserted into the sheath tube 82 from the opening of the sheath housing 86. When the dilator 70 is completely inserted into the sheath tube 82, the tip portion 74 of the dilator 70 is exposed from the tip of the sheath tube 82 as shown in FIGS.

  A catheter insertion operation using the sheath introducer 200 will be briefly described below. First, a perforation is made at a predetermined position on the skin using an introduction needle (not shown) or the like, and a guide wire (not shown) is inserted into the blood vessel through the perforation. Then, the guide wire is inserted into the lumen from the distal end of the sheath introducer 200, and the sheath introducer 200 is inserted into the blood vessel along the guide wire. At this time, the tip 74 of the dilator 70 expands the diameter of the skin perforation. Thereby, the distal end side of the sheath introducer 200 can be inserted into the blood vessel. After the sheath introducer 200 is inserted into the blood vessel, the guide wire and dilator 70 are removed, leaving only the sheath 80. Thereby, the sheath 80 functions as a passage connecting the outside of the body and the inside of the blood vessel, and an instrument such as a catheter can be inserted into the blood vessel through the sheath 80.

  As a dilator described above, Patent Document 1 describes a dilator having a flexible tip portion and having a tapered shape toward the tip.

Patent Document 2 describes a dilator having a predetermined tapered tapered tip.
Japanese Patent Laid-Open No. 9-51953 JP 2002-191697 A

  Each of the dilators described in Patent Documents 1 and 2 has a tapered shape toward the tip. When a sheath introducer is inserted into a blood vessel, resistance occurs when the tip of the dilator is inserted into a perforation on the skin and when the dilator expands the diameter of the perforation on the skin. Because this resistance occurs, the operator who operates the sheath introducer feels resistance when the tip of the dilator reaches the perforation on the skin, and the sheath introducer cannot be inserted smoothly. was there. Such problems still occur even when the dilators described in Patent Documents 1 and 2 are used, and there is little resistance, and the sheath introducer can be smoothly inserted into a vessel such as a blood vessel. There was a need for a dilator that could be used.

  Therefore, an object of the present invention is to provide a dilator that has a smaller resistance during insertion and allows an operator to smoothly insert a sheath introducer into a blood vessel, and a sheath introducer including the dilator.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.

  The first aspect of the present invention is a dilator having a lumen (60) penetrating from the proximal end side to the distal end side, the proximal end side tube portion (30), and the distal end of the tube portion (30) from the distal end. A taper portion (20) formed with a taper that narrows toward the side, and a tip portion (10) formed so as to extend from the tip of the taper portion (20) toward the tip side. The part (10) is a dilator (100) that is tapered toward the tip side and is formed with a fine taper having an inclination angle smaller than the inclination angle at the tip part of the taper part (20).

  In the first aspect of the present invention, the length of the tip (10) is preferably not less than 0.5 mm and not more than 4 mm.

  In the first aspect of the present invention, it is preferable that a taper (15) is formed at the distal end of the distal end portion (10) so as to become narrower from the proximal end side toward the distal end side.

  In the first aspect of the present invention, the inclination angle of the fine taper is preferably more than 0 ° and not more than 10 °, more preferably more than 0 ° and not more than 0.5 °.

  The second aspect of the present invention uses a high-frequency molding machine having a cylindrical mold (300), a tube portion (30) having a lumen penetrating from the proximal end side to the distal end side, and the tube portion (30). A taper portion (20) formed with a taper that narrows from the tip end toward the tip end side, and a tip end portion (10) formed to extend from the tip end of the taper portion (20) toward the tip end side. The mold (300) includes a mold straight pipe part (330) on the base end side and a tip side from the tip of the mold straight pipe part (330). And a taper portion (320) capable of high-frequency induction heating, and a taper portion (320) that is capable of high-frequency induction heating, and is formed to extend from the tip of the die taper portion (320) toward the tip side. A die tip (310), and a die tip ( 10), the die tip (310) has an outer diameter larger than the inner diameter of the die straight pipe portion (330) and the inner diameter of the straight tubular body having the outer diameter smaller than the inner diameter of the die straight pipe portion (330). A core material insertion step of inserting a core material having an outer diameter smaller than the inner diameter, and a cylindrical body into which the core material is inserted are inserted from the mold straight pipe part (330) side to the mold tip part (310). And a molding step of forming a dilator having a predetermined shape by high-frequency induction heating at the location of the mold taper portion (320).

  In the second aspect of the present invention, it is preferable that the die tip portion (310) is formed with a small taper that becomes thinner toward the tip side. The inclination angle of the fine taper is preferably greater than 0 ° and not greater than 10 °, and more preferably greater than 0 ° and not greater than 0.5 °.

  In the second aspect of the present invention, it is preferable to provide a cutting step of cutting a taper that becomes narrower from the proximal end side toward the distal end side at the distal end portion of the dilator after the molding step.

  The third aspect of the present invention is a sheath introducer including the dilator of the first aspect of the present invention and a sheath through which the dilator is inserted.

  The dilator (100) of the present invention has a tapered portion (20) that is tapered at the tip portion, and a tip portion (10) that is further on the tip side of the tapered portion. Thereby, the sheath introducer provided with the dilator of the present invention has smaller resistance, and the operator can smoothly insert it into the blood vessel. Moreover, the follower | trackability to the guide wire of the sheath introducer containing a dilator can be improved by forming the front-end | tip part (10) in the front-end | tip part.

<Dilator 100>
FIG. 2 is a diagram schematically showing the shape of the tip portion of the dilator 100 of the present invention. The dilator 100 is a tubular member having a lumen 60 penetrating from the proximal end side to the distal end side. The dilator 100 is formed so as to extend from the distal end of the tube portion 30 to the distal end side, and the tapered portion 20 formed with a taper that becomes thinner from the distal end of the tube portion 30 toward the distal end side. It is comprised with the tip part 10 made. In addition, let the left side of FIG. 2 be a base end side, and let the right side be a front end side. In FIG. 2, the description of the proximal end side of the tube portion 30 is omitted, but actually, the tube portion 30 further extends to the proximal end side.

  A guide wire can be inserted into the lumen 60. As described in the background art section, first, a guide wire is inserted into a blood vessel (vessel) using an introduction needle or the like, and a sheath introducer including a dilator 100 and a sheath is provided along the guide wire. Insert into the blood vessel. The sheath 80 shown in FIG. 1 is used as the sheath. However, the sheath is not limited to the sheath 80. The lumen 60 has an inner diameter that is slightly larger than the outer diameter of the guide wire. The lumen 60 is formed with a constant inner diameter over the entire length of the dilator 100.

(Tube part 30)
The tube part 30 is a site | part of the base end side of the dilator 100 of this invention. The base end side of the tube portion 30 omitted in FIG. 2 is connected to the dilator housing 76 as shown in FIG. The dilator housing 76 is formed with an opening communicating with the lumen 60, and a guide wire or the like can be inserted into the lumen 60 through the opening.

  The tube part 30 is a cylindrical tubular member having a constant outer diameter. As shown in FIG. 1A, the dilator 70 is inserted into the sheath tube 80 from the opening of the sheath housing 86. For this reason, the outer diameter of the tube portion 30 is formed to be smaller than the inner diameter of the sheath tube 80.

  Examples of the material constituting the dilator 100 include a urethane resin such as polyvinyl chloride resin and polyurethane, a polyolefin resin such as polyethylene, polypropylene, and an ethylene-propylene copolymer, a polyamide resin, and a fluorine resin such as Teflon (registered trademark). And various synthetic resin materials such as ethylene-vinyl acetate copolymer. Among these, it is preferable to use a thermoplastic resin because it can be thermally processed. Moreover, what added various additives, such as a modifier, may be used for a resin material. Furthermore, as a material for the dilator, it is preferable to use a crystalline resin such as polypropylene in that sufficient tip strength can be imparted to the tip portion.

(Taper part 20)
The tapered portion 20 is formed from the distal end side to the distal end side of the tube portion 30 and is formed in a tapered shape that becomes thinner from the proximal end side toward the distal end side. In other words, the outer diameter of the proximal end side of the tapered portion 20 is substantially the same as the outer diameter of the tube portion 30, but may be formed larger than the outer diameter of the tube portion 30. Moreover, the outer diameter of the front end side of the taper part 20 is substantially the same as the outer diameter of the front-end | tip part 10 demonstrated later.

  The length of the tapered portion 20 (length in the longitudinal direction) is preferably 5 to 30 mm. If the length is too short, the taper becomes steep, and resistance when the dilator 100 is inserted into the body is increased. The taper inclination angle (angle formed with respect to the longitudinal direction (center line)) is preferably in the range of 5 ° to 30 °. In the dilator 100 shown in FIG. 2, the inclination of the taper portion 20 is abrupt on the distal end side and gentle on the proximal end side to form a two-stage inclination. The taper portion 20 may have a multi-step inclination as described above. The multi-stage inclination has an effect that the dilator 100 can be smoothly inserted.

(Tip 10)
The distal end portion 10 extends from the distal end of the tapered portion 20 toward the distal end side. The distal end portion 10 is a cylindrical tube-shaped member, and is thinned toward the distal end side, and a minute taper having an inclination angle smaller than the inclination angle of the distal end portion of the taper portion 20 is formed. The inclination angle of the minute taper is preferably more than 0 ° and not more than 10 °, and more preferably more than 0 ° and not more than 0.5 °. By forming such a fine taper, release from a high-frequency molding die described later becomes easy.

  The outer diameter of the distal end portion 10 is preferably as small as possible from the viewpoint of reducing insertion resistance into the blood vessel. However, the thickness of the tip 10 needs to be at least 0.05 mm or more from the viewpoint of imparting a predetermined strength to the tip 10. In addition to this point, since the lumen 60 is formed in the distal end portion 10, the outer diameter of the distal end portion 10 is preferably in the range of 0.75 to 1.20 mm.

  The length of the tip 10 is preferably in the range of 0.5 mm to 4.0 mm, and more preferably in the range of 0.5 mm to 3.0 mm. If the length is too short, it is difficult to exhibit the effect of reducing the puncture resistance due to the provision of the distal end portion 10. If the length is too long, the distal end portion 10 may be bent due to resistance or the like when inserted into the blood vessel.

  It is preferable that a taper 15 is formed at the distal end of the distal end portion 10 so as to become narrower from the proximal end side toward the distal end side. By forming the taper 15, the puncture resistance of the dilator 100 of the present invention can be further reduced. The inclination angle of the taper 15 is preferably in the range of 20 ° to 40 °, more preferably in the range of 25 ° to 35 °. The taper 15 is preferably formed by cutting as will be described later.

(About minimally invasiveness of the dilator 100 of the present invention)
In the dilator 100 of the present invention, a tapered portion 20 is formed at the distal end portion, and the distal end portion 10 is further formed on the distal end side of the tapered portion 20. By adopting such a shape, the resistance can be reduced as compared with the conventional dilator, and the operator can insert the sheath introducer into the body more smoothly. Hereinafter, the reason why the present inventor considers the reason why such an effect occurs will be described.

  It is considered that there are two types of resistance as resistance when the sheath introducer is inserted into the body along the guide wire. The first is the resistance when the distal end of the dilator of the sheath introducer is inserted into the perforation on the skin through which the guide wire passes (this resistance is referred to as “puncture resistance”). The second resistance is a resistance when the perforation is expanded by the taper shape of the tip of the dilator after the leading end of the dilator is inserted (this resistance is referred to as “expanded resistance”). .

  In the conventional dilator, there is no tip portion 10 at the tip portion, and a tapered shape is formed immediately from the most advanced portion. Therefore, the expansion resistance is applied almost simultaneously with the above puncture resistance, and these two resistances are added, so that the operator feels a large resistance.

  On the other hand, since the dilator 100 of the present invention has the distal end portion 10 formed on the distal end side with respect to the tapered portion 20, the surgeon first has to insert the distal end portion 10 into the skin. A puncture resistance is felt, and after a little later, a diameter expansion resistance when the taper portion 20 is inserted is felt. Thus, the surgeon does not feel the two resistances at the same time, but feels them as small resistances, so that the operation of inserting the sheath introducer into the body can be performed more smoothly.

<Method for Manufacturing Dilator 100>
The manufacturing method of the dilator 100 is demonstrated below using FIG. First, as shown in FIG. 3 (a), a tube having a lumen (not shown) over its entire length and having a constant outer diameter is formed by extrusion molding. A certain cylindrical member is formed. Then, a core material (not shown) is inserted into the lumen of the tube, and heat molding is performed using an outer frame (not shown) for forming the tapered portion 20 and the tip portion 10 on the tip side. As shown in FIG. 3B, the tapered portion 20 and the distal end portion 10 are formed at the distal end portion. The heat forming is preferably performed by high frequency forming. In addition, when forming the taper part 20 and the front-end | tip part 10 by this thermoforming, a thermoplastic resin is used as a material which forms the dilator 100. FIG.

  Specifically, as shown in FIG. 4, a high-frequency molding machine having a cylindrical mold 300 is used for manufacturing the dilator 100. The mold 300 of this high-frequency molding machine is formed with a mold straight pipe section 330 on the base end side, and a taper that becomes narrower from the tip of the mold straight pipe section 330 toward the tip side, and high-frequency induction. A die taper portion 320 that can be heated and a die tip portion 310 formed so as to extend from the tip end of the die taper portion 320 toward the tip end side are provided.

  Using such a high frequency molding machine, the dilator 100 of the present invention is manufactured as follows. First, at least the portion of the mold taper portion 320 is heated by high frequency induction using a high frequency molding machine, and in this state, the outer diameter is larger than the inner diameter of the die tip portion 310 and the inner diameter of the die straight tube portion 330 is larger. A core material having an outer diameter smaller than the inner diameter of the die tip portion 310 is inserted into the lumen of a straight tubular cylinder having a small outer diameter (corresponding to FIG. 3A) (core material). Insertion process). Next, the cylindrical body in which the core material is inserted is inserted from the mold straight pipe section 330 side to the mold tip section 310, and the dilator 100 having a predetermined shape is formed by high-frequency induction heating at the mold taper section 320. Mold (molding process). In this way, the dilator 100 is manufactured.

  Further, after the forming step, as shown in FIG. 3C, a predetermined taper 15 can be formed by cutting (taper cut) the tip side of the tip portion 10 as necessary. The dilator 100 is manufactured by the above procedure.

What was actually produced as the dilator of the present invention is shown below.
(Example 1)
A dilator having the shape shown in FIG. The dimensions of each part are described below.
Lumen 60: Inner diameter 0.61mm
Tube portion 30: outer diameter 1.78 mm
Tapered portion 20: the inclination angle of the first taper 22 is 10 °, the inclination angle of the second taper 24 is 4 °, the inclination angle of the third taper 26 is 6 °, the length of the first taper 22 is 0.5 mm, and the second taper 24 10 mm length, 3 mm length of the third taper 26, large diameter X ¹ 1.81 mm, small diameter X ² 0.98 mm
Tip portion 10: large diameter Y ¹ 0.79 mm, small diameter Y ² 0.786 mm, minute taper tilt angle 0.07 °, length 1.5 mm, tip taper 15 tilt angle 30 °

(Comparative Example 1)
A dilator having the shape shown in FIG. 5B was produced. The dimensions of each part are described below.
Lumen 60: Inner diameter 0.61mm
Tube portion 30: outer diameter 1.78 mm
Tapered portion 20: the inclination angle of the first taper 22 is 10 °, the inclination angle of the second taper 24 is 4 °, the inclination angle of the third taper 26 is 6 °, the length of the first taper 22 is 0.3 mm, and the second taper 24 Length 20 mm, third taper 26 length 5 mm, large diameter X ³ 1.81 mm, small diameter X ⁴ 0.93 mm, tip diameter 0.77 mm

  In the dilators of the above examples and comparative examples, a third taper 26 is provided. By providing the third taper 26, the distal end of the sheath and the distal end of the dilator are brought into close contact with each other, and there is an effect that resistance when the sheath introducer is inserted into the vascular vessel can be further reduced.

(Evaluation methods)
Using the dilators of the above examples and comparative examples, a perforation experiment was performed as a sheath introducer in combination with a sheath. As the sheath, the one attached to the sheath introducer for angiography manufactured by Zeon Medical was used.

  The measurement is performed using a vinyl chloride sheet having a thickness of 0.3 mm, and a guide wire having an outer diameter of 0.60 mm is inserted into the sheet, and the dilators of the above-described examples and comparative examples are formed along the guide wire. This was done by inserting a sheath introducer equipped with The maximum resistance value when the sheath introducer was inserted into the vinyl chloride sheet was measured. The results are shown in Table 1.

  6A and 6B are cross-sectional views of the tip portions of the dilator (a) of the present invention and the conventional dilator (b). As described above, the conventional dilator is formed with a tapered shape immediately from the most advanced part, and at this time, the most advanced part is subjected to a polishing process to prevent the occurrence of fluffing, etc. Has been processed. That is, as shown in FIG. 6B, in the conventional dilator, the thickness of the tube portion 30 is, for example, 0.44 mm, and the thickness of the tip portion of the tapered portion 20 is, for example, 0.07 mm. Further, the inclination angle of the tapered portion 20 is 10.5 °.

  On the other hand, in the dilator 100 of the present invention, as shown in FIG. 6A, the thickness of the tube portion 30 is 0.44 mm, for example, and the most advanced thickness of the taper portion 20 is 0.08 mm, for example. And the thickness of the front-end | tip part 10 is 0.08 mm, for example. Further, a taper with an inclination angle of 30 degrees is formed at the distal end of the distal end portion 10 by a cutting process (taper cut) so as to become narrower from the proximal end side toward the distal end side. The inclination angle of the taper portion 20 is 10.5 °, the inclination angle of the minute taper of the tip portion 10 is 0.07 °, and the length of the tip portion 10 is 2 mm.

  When the strength of the tip portion of these dilators was examined as follows, the maximum stress before yield of the tip portion of the dilator of the present invention was 4.9 N, and the maximum stress before yield of the tip portion of the conventional dilator was It was 3.9N. For this reason, although the dilator 100 of this invention has the front-end | tip part 10 at the front-end | tip of the taper part 20, it turned out that it has sufficient intensity | strength compared with the past.

(Measurement method of strength at tip)
FIG. 7 shows an outline of the measurement method. A dilator sample 410 having the above dimensions cut to a length of 7 cm was fixed to a rheometer by chucking with a pin vice. A flat SUS steel plate 430 was placed on the jig base 420 and the jig base 420 was raised at a speed of 2 cm / min. The stress at this time was captured as digital data by NR2000 of Keyence Corporation. And the time when the slope of the stress increase changed from the straight line was judged as the time when the dilator yielded, and the stress at this time was measured. The laboratory atmosphere was room temperature 19 ° C. and humidity 23%.

  In the dilator according to the present invention, since the thickness of the tip of the tip is thinner than that of the conventional one, it is possible to prevent the occurrence of the scalding or the like only by performing the cutting process. For this reason, it is not necessary to perform the tip polishing treatment as in the prior art. Moreover, since the dilator of this invention does not add extra heat to the front-end | tip part tip by the grinding | polishing process in this way, it can be considered that the front-end | tip part was able to maintain sufficient intensity | strength. Further, since polypropylene, which is a crystalline resin, was used as the resin for the dilator, it can be considered that the crystallinity at the tip portion was improved and sufficient strength could be maintained.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. Rather, the dilator, the dilator manufacturing method, and the sheath introducer can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. Should be understood as being included in the technical scope of

(A) is a figure which shows the whole structure of the conventional sheath introducer 200 containing a dilator and a sheath, (b) is a figure which shows the sheath introducer 200 of the state by which the dilator was inserted in the sheath, (C) is the enlarged view of the front-end | tip part of this sheath introducer. It is an enlarged view of the front-end | tip part of the dilator 100 of this invention. It is a figure explaining the manufacturing method of the dilator 100 of this invention. (A) is side surface sectional drawing of the cylindrical metal mold | die used in the manufacturing method of the dilator of this invention. (B) is an expanded sectional view of the front-end | tip part of this cylindrical metal mold | die. It is a figure which shows the shape of the dilator manufactured in the Example and the comparative example. It is sectional drawing which showed typically the dilator sample used in the measurement of the intensity | strength of a front-end | tip part. It is explanatory drawing which shows the method for measuring the intensity | strength of a front-end | tip part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Tip part 15 Taper 20 Taper part 30 Tube part 60 Lumen 80 Sheath 100 Dilator 200 Sheath introducer 300 Mold 310 Mold tip part 320 Mold taper part 330 Mold straight pipe part

Claims (8)

A dilator having a lumen penetrating from the proximal side to the distal side,
A tube portion on the base end side, a taper portion that is tapered from the tip of the tube portion toward the tip side, and a tip formed to extend from the tip of the taper portion toward the tip side With
The dilator wherein the tip end portion is formed with a fine taper that becomes narrower toward the tip end side and has an inclination angle smaller than an inclination angle at a tip end portion of the taper portion.   The dilator according to claim 1, wherein a length of the tip portion is not less than 0.5 mm and not more than 4 mm.   The dilator according to claim 1 or 2, wherein a taper is formed at a distal end of the distal end portion so as to become narrower from the proximal end side toward the distal end side.   The dilator according to any one of claims 1 to 3, wherein an inclination angle of the minute taper is more than 0 ° and not more than 10 °.   The dilator according to claim 4, wherein an inclination angle of the minute taper is more than 0 ° and not more than 0.5 °. Using a high-frequency molding machine having a cylindrical mold, a tube portion having a lumen that penetrates from the proximal end side to the distal end side and a taper that narrows from the distal end of the tube portion toward the distal end side are formed. A dilator comprising a tapered portion and a tip portion formed so as to extend from the tip of the taper portion toward the tip side,
The mold includes a mold straight pipe portion on the base end side, and a mold taper capable of high-frequency induction heating while being tapered from the tip of the mold straight pipe portion toward the tip side. A mold tip formed to extend from the tip of the die taper portion toward the tip side,
The inner diameter of the die tip is inserted into the lumen of a straight tubular cylinder having an outer diameter larger than the inner diameter of the die tip and an outer diameter smaller than the inner diameter of the mold straight tube. A core material insertion step of inserting a core material having a smaller outer diameter,
The cylindrical body in which the core material is inserted is inserted from the mold straight pipe part side to the mold tip part, and is formed into a dilator having a predetermined shape by high-frequency induction heating at the mold taper part. A dilator manufacturing method comprising: a molding step. It is a manufacturing method of the dilator according to claim 6,
The manufacturing method of a dilator provided with the cutting process which cuts the taper which becomes thin toward the front end side from the base end side in the front-end | tip part of the said dilator after the said formation process.   A sheath introducer comprising the dilator according to claim 1 and a sheath through which the dilator is inserted.

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