Sheath and balloon catheter unit

Abstract

To provide a technique for adjusting an axial position of an outer diameter changing part formed in a dilatation body with respect to a balloon.SOLUTION: A sheath for use in a balloon catheter, includes a first region 30 and a second region 32 provided closer to a proximal side relative to the first region 30, the sheath 20 being axially slidable relative to the balloon catheter when the balloon 14 of the balloon catheter is in a deflated state. The sheath 20 can become such a state that the second region 32 is dilated more than the first region 30 when the balloon 14 is covered by the first region 30 and the second region 32 and a standard internal pressure of 2.0 atm is applied to the balloon 14.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a sheath used for a balloon catheter.

Background Art

[0002] A balloon catheter may include a covering member composed of a band that covers a part of the balloon in addition to a shaft and a balloon provided at the tip side portion of the shaft (see, for example, Patent Document 1). By covering a part of the balloon with the covering member, an expansion body composed of the balloon and the covering member is provided in a certain axial range of the balloon. When the balloon is expanded, by restraining the expansion of a part of the balloon with the covering member, two outer diameter changing portions that form a constricted portion are formed in the expansion body. By suppressing the axial slip with respect to the constricted portion of the living organ by this outer diameter changing portion, the axial positioning of the balloon catheter with respect to the living organ becomes easy.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The covering member of Patent Document 1 is fixed to the balloon. Therefore, the axial position of the outer diameter changing portion formed in the expansion body with respect to the balloon is also fixed. From the viewpoint of increasing the degree of freedom during the procedure using the balloon catheter, it is desired that the axial position of the outer diameter changing portion of the expansion body with respect to the balloon can be adjusted.

[0005] Therefore, one of the objects of the present disclosure is to provide a technique for enabling adjustment of the axial position of the outer diameter changing portion formed in the expansion body with respect to the balloon.

Means for Solving the Problems

[0006] The sheath of the present disclosure is a sheath used for a balloon catheter, and includes a first region and a second region provided on the proximal side of the first region. The sheath is axially slidable with respect to the balloon catheter when the balloon of the balloon catheter is in a contracted state. When a reference internal pressure of 2.0 atm is applied to the balloon with the balloon covered by the first region and the second region, the second region can be in a state of being expanded more than the first region.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0008] Hereinafter, embodiments for implementing the sheath of the present disclosure will be described. The same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. In each drawing, for the sake of convenience of explanation, components are appropriately omitted, enlarged, or reduced. The drawings should be viewed in accordance with the orientation of the reference numerals. In this specification, the notations "first", "second", etc., "nth" (n is a natural number) are used only as formal notations for distinguishing a plurality of elements, and have no other substantial meaning. For example, the notations "nth" do not limit the order of each element with the "nth" notation.

[0009] (First Embodiment) Referring to FIGS. 1 and 2, a balloon catheter 10 used in combination with a sheath (not shown in FIG. 1) will be described. The balloon catheter 10 is used for treating a living body. Here, the "treatment" refers to an act related to the treatment or examination of a living body. The balloon catheter 10 of this embodiment is used to facilitate the passage of a medical device through a stenotic portion of a living body organ by expanding the stenotic portion of the living body organ using a balloon 14. The stenotic portion of this living body organ is, for example, the papilla of the digestive organ, etc., but in addition to this, it may also be a part of a circulatory organ such as the heart, blood vessels, etc.

[0010] The balloon catheter 10 includes a shaft 12 that is inserted into the body at least at the distal end side portion, a balloon 14 provided at the distal end side portion of the shaft 12, and a handle 16 attached to the proximal end side portion of the shaft 12. The handle 16 is grasped by an operator such as a doctor. In this specification, the direction along the center line C12 of the shaft 12 is simply referred to as the "axial direction", and the radial direction and the circumferential direction of a circle centered on the center line of the shaft 12 are simply referred to as the "radial direction" and the "circumferential direction".

[0011] The shaft 12 has flexibility that allows for bending deformation. The shaft 12 includes a main portion 12a provided in the axial range from the tip of the handle 16 to the proximal end of the balloon 14. The shaft 12 is composed of at least one shaft member 18A, 18B. The shaft 12 of this embodiment includes, as the shaft members 18A, 18B, a cylindrical outer shaft member 18A and an inner shaft member 18B passed through the outer shaft member 18A. A fluid lumen (not shown) through which the fluid supplied into the balloon 14 flows is formed in the outer shaft member 18A. The inner shaft member 18B protrudes from the outer shaft member 18A toward the tip side and constitutes the portion from the tip of the outer shaft member 18A to the tip of the shaft 12. An inner lumen (not shown) for passing a medical device such as a guide wire is formed in the inner shaft member 18B.

[0012] The balloon 14 is expandable by the fluid supplied from the proximal end side of the shaft 12. FIGS. 1 and 2 show the state in which the balloon 14 is expanded. The fluid is supplied into the balloon 14 from a fluid supply device (not shown) such as an inflator via a port 16a provided in the handle 16 and the fluid lumen of the shaft 12. This fluid may be various gases such as air in addition to various liquids such as a contrast agent, physiological saline, and sterilized water. The internal pressure of the balloon 14 is adjusted by changing the pressure applied by the fluid supply device.

[0013] As the balloon 14, for example, a compliant balloon whose outer diameter changes according to the internal pressure may be used, but a non-compliant balloon whose outer diameter hardly changes from the outer diameter defined by the internal pressure may also be used. The balloon 14 includes an expansion portion 14a that is expandable by the fluid supplied therein and a pair of sleeve portions 14b provided on both axial sides with respect to the expansion portion 14a. The expansion portion 14a of this embodiment includes a cylindrical body portion 14c that extends straight in the axial direction and an outer diameter change portion 14d provided on both axial sides with respect to the body portion 14c and having a reduced diameter as it extends axially outward from the body portion 14c. The pair of sleeve portions 14b are attached to a part of the shaft 12 by welding, adhesion, or the like.

[0014] Next, the sheath 20 will be described. Refer to FIGS. 2 and 3. FIG. 2 shows the balloon 14 in a contracted state, and FIG. 3 shows the balloon 14 in an expanded state. In the cross-sectional views such as FIG. 2, the outer shape rather than the cross-section of the balloon 14 is shown.

[0015] The sheath 20 is used as a balloon catheter unit 22 combined with the balloon catheter 10. The balloon catheter 10 may be used in a state separated from the sheath 20. A sheath lumen 26 through which the balloon catheter 10 passes is formed inside the sheath 20. The sheath 20 functions as a covering member that covers the balloon 14. The sheath 20 is axially slidable with respect to the balloon catheter 10 when the balloon 14 is in a contracted state.

[0016] The sheath 20 is set to an axial length that can cover at least the axial range from the proximal end of the main body 12a of the shaft 12 to the balloon 14. Consider the case where the balloon 14 is disposed at a location in the body to be treated by the balloon catheter 10. In this case, while the balloon 14 is covered by the sheath 20 in the body, an axial load is applied to the sheath 20 at a location that covers the main body 12a of the shaft 12 outside the body, so that the sheath 20 can slide with respect to the balloon catheter 10. A sheath handle (not shown) is attached to the proximal end of the sheath 20 of the present embodiment. An axial load may be applied to the sheath 20 by moving this sheath handle. In addition to this, an axial load may be applied to the sheath 20 by an operation on an operation mechanism using a slider knob, a rotary handle, etc. provided on the sheath handle.

[0017] The sheath 20 includes a first region 30, a second region 32, and a third region 34 in order from the distal end side to the proximal end side of the sheath 20. The first region 30 is provided at the distal end side portion of the sheath 20. In this embodiment, there is no other part of the sheath 20 on the distal end side of the first region 30. The second region 32 is provided on the proximal end side of the first region 30. The third region 34 is provided on the proximal end side of the second region 32.

[0018] At least the first region 30 and the second region 32 of the sheath 20 can cover at least a part of the expansion part 14a of the balloon 14. Thereby, an expansion body 36 composed of the balloon 14 and the sheath 20 is provided in an axial range where the expansion part 14a of the balloon 14 is located. The expansion body 36 includes an intermediate part 38 provided in an axial range of the first region 30 of the sheath 20, and a proximal end side part 40 and a distal end side part 42 adjacent to both axial sides of the intermediate part 38. The proximal end side part 40 is on the proximal end side of the intermediate part 38, and the distal end side part 42 is on the distal end side of the intermediate part 38. When there is no other part of the sheath 20 on the distal end side of the first region 30 of the sheath 20 as in this embodiment, the distal end side part 42 is composed only of the balloon 14 not covered by the sheath 20. On the other hand, when a fourth region 60 of the sheath 20 exists on the distal end side of the first region 30 of the sheath 20 (see FIG. 8), the distal end side part 42 is composed of both the fourth region 60 of the sheath 20 and the expansion part 14a of the balloon 14.

[0019] The third region 34 of the sheath 20 has an axial length capable of covering most of the main part 12a of the shaft 12. Here, "most" means, for example, an axial range of at least 80% or more of the axial length of the main part 12a.

[0020] As shown in FIG. 2, the internal pressure of the balloon 14 is not pressurized from the atmospheric pressure, and the state where the balloon 14 is not expanded is referred to as the unexpanded state S1. As shown in FIG. 3, the state where a reference internal pressure of 2.0 atm is applied to the balloon 14 by pressurizing the internal pressure of the balloon 14 with a fluid supply device is referred to as the reference internal pressure state S2. Each region 30, 32, 34 of the sheath 20 in the present embodiment has the same outer diameter when the balloon 14 is in the unexpanded state S1. The outer diameter referred to in this specification means the diameter.

[0021] As shown in FIG. 3, the sheath 20 can be in a state where at least a part of the second region 32 is expanded more than the first region 30 when the balloon 14 is in the reference internal pressure state S2 with the balloon 14 covered by the first region 30 and the second region 32. At this time, the sheath 20 can be in a state where the proximal end side portion 40 in the expansion body 36 is expanded more than the intermediate portion 38. Thereby, a proximal end side outer diameter changing portion 44a is formed at the tip of the proximal end side portion 40 of the expansion body 36. The proximal end side outer diameter changing portion 44a increases in outer diameter toward the proximal end side.

[0022] Further, the sheath 20 in the present embodiment can be in a state where the proximal end side portion 40 and the distal end side portion 42 in the expansion body 36 are expanded more than the intermediate portion 38 when the balloon 14 is in the reference internal pressure state S2. Thereby, a constricted portion 44 is formed by the intermediate portion 38 and the respective portions 40, 42 of the expansion body 36. In addition to the proximal end side outer diameter changing portion 44a described above, this constricted portion 44 includes a distal end side outer diameter changing portion 44b formed at the proximal end portion of the distal end side portion 42. The distal end side outer diameter changing portion 44b increases in outer diameter toward the distal end side.

[0023] By disposing the proximal end side outer diameter changing portion 44a of the expansion body 36 axially proximal to the constricted portion of the living organ, slipping of the balloon catheter toward the axial distal end side with respect to the constricted portion can be suppressed. Further, by disposing the constricted portion of the living organ inside the constricted portion 44 of the expansion body 36, slipping in both axial directions with respect to the constricted portion can be suppressed by the respective outer diameter changing portions 44a, 44b.

[0024] As described above, in order to expand the second region 32 of the sheath 20 more than the first region 30, the sheath 20 is configured to satisfy both the following first condition and second condition. Further, in order to expand the proximal end side portion 40 and the distal end side portion 42 of the expander 36 more than the intermediate portion 38, the sheath 20 satisfies both the following first condition and second condition, and is configured to satisfy the third condition.

[0025] Refer to FIG. 3. In FIG. 3, the shape of the uncovered balloon 14 when it is in the reference internal pressure state in which the reference internal pressure is applied to the balloon 14 not covered with the sheath 20 (hereinafter referred to as the uncovered balloon 14) is shown by a two-dot chain line. When the uncovered balloon 14 is in the reference internal pressure state, the maximum outer diameters of the uncovered balloon 14 at certain positions of the proximal end side portion 40 and the distal end side portion 42 of the expander 36 are referred to as Rp0 and Rd0.

[0026] The first condition is a condition regarding the first region 30 of the sheath 20. The first condition is to restrain the expansion of the balloon 14 by the first region 30 of the sheath 20 when expanding the balloon 14 until the internal pressure of the balloon 14 reaches the reference internal pressure from the atmospheric pressure. In order to satisfy this condition, it is sufficient to restrain the expansion of the balloon 14 at the timing from when the internal pressure of the balloon 14 exceeds the atmospheric pressure until it reaches the reference internal pressure. In order to satisfy this condition, the expansion of the balloon 14 is restrained so that the outer diameter Ra1 of the first region 30 when the balloon 14 is in the reference internal pressure state S2 is smaller than the maximum outer diameters Rp0 and Rd0 of the uncovered balloon 14. Thereby, in the process of expanding the balloon 14, it becomes possible to expand the balloon 14 more than the intermediate portion 38 at the proximal end side portion 40 and the distal end side portion 42 of the expander 36. In order to satisfy the first condition, the larger the difference between the outer diameter Ra1 of the first region 30 and the maximum outer diameters Rp0 and Rd0 of the uncovered balloon 14, the easier it is to form the constricted portion 44 with a large outer diameter difference. In order to satisfy the first condition, it is preferable to adjust the ease of elongation of the first region 30 of the sheath 20 in the radial direction of the sheath 20. The lower the ease of elongation of the first region 30 of the sheath 20, the easier it is to restrain the expansion of the balloon 14 by the first region 30 of the sheath 20.

[0027] The second condition is a condition regarding the first and second regions 30 and 32 of the sheath 20. It is also a condition regarding the intermediate portion 38 and the proximal end portion 40 of the extension body 36. The second condition is that when the balloon 14 is expanded until the internal pressure thereof reaches the reference internal pressure from the atmospheric pressure, the second region 32 can be expanded together with the balloon 14 until the outer diameter becomes larger than the maximum outer diameter Ra1 of the first region 30. Here, the maximum outer diameter Ra1 of the first region 30 means the maximum outer diameter of the first region 30 when the balloon 14 is in the reference internal pressure state S2. The sheath 20 of the present embodiment is configured such that when the balloon 14 is expanded in this way, the amount of expansion in the radial direction of the second region 32 is larger than the amount of expansion in the radial direction of the first region 30. Thereby, when the balloon 14 is in the reference internal pressure state S2, the second region 32 can be made to be in a state of being expanded more than the first region 30. It can also be said that when the balloon 14 is in the reference internal pressure state S2, the proximal end portion 40 of the extension body 36 can be made to be in a state of being expanded more than the intermediate portion 38. In order to satisfy the second condition, it is sufficient that the second region 32 of the sheath 20 is more likely to expand than the first region 30 when the sheath 20 expands in the radial direction. The higher the ease of expansion of the second region 32 is made compared to the ease of expansion of the first region 30, the easier it is for the second region 32 of the sheath 20 to expand together with the balloon 14 until the outer diameter becomes larger than the maximum outer diameter Ra1 of the first region 30.

[0028] The third condition is a condition regarding the intermediate portion 38 and the distal end portion 42 of the extension body 36. The third condition is that when the balloon 14 is expanded until the internal pressure thereof reaches the reference internal pressure from the atmospheric pressure, the distal end portion 42 of the extension body 36 can be expanded until the outer diameter becomes larger than the maximum outer diameter Ra1 of the first region 30. Thereby, when the balloon 14 is in the reference internal pressure state S2, the distal end portion 42 of the extension body 36 can be made to be in a state of being expanded more than an intermediate portion 38 where the first region 30 of the sheath 20 is located.

[0029] Consider a case where, as in this embodiment, there is no other part of the sheath 20 on the distal side of the first region 30 of the sheath 20. In this case, in order to satisfy the third condition, the balloon 14 at the distal end portion 42 of the expander 36 is expanded until it has an outer diameter exceeding the maximum outer diameter Ra1 of the first region 30. In this case, if the first condition of making the outer diameter Ra1 of the first region 30 of the sheath 20 described above smaller than the maximum outer diameter Rd0 of the non-covered balloon 14 is satisfied, the balloon 14 can be expanded in this way. In this case, the third condition can be said to be the fact that there is no other part of the sheath 20 on the distal side of the first region 30 of the sheath 20 itself.

[0030] As described in the third embodiment (see FIG. 7), consider a case where a fourth region 60 exists on the distal side of the first region 30 of the sheath 20. In this case, in order to satisfy the third condition, it is sufficient that the fourth region 60 of the sheath 20 can be expanded together with the balloon 14 until it has an outer diameter exceeding the maximum outer diameter Ra1 of the first region 30 of the sheath 20. In order to achieve this, it is sufficient to make the fourth region 60 of the sheath 20 more likely to expand than the first region 30 when the sheath 20 expands in the radial direction. The higher the ease of expansion of the fourth region 60 is than the ease of expansion of the first region 30, the easier it is for the fourth region 60 of the sheath 20 to expand together with the balloon 14 until it has an outer diameter exceeding the maximum outer diameter Ra1 of the first region 30. Note that the sheath 20 of the third embodiment is configured such that when the balloon 14 is expanded from the atmospheric pressure to the reference internal pressure, the amount of expansion in the radial direction of the fourth region 60 is larger than the amount of expansion in the radial direction of the first region 30.

[0031] As an index indicating the ease of stretching of each of the regions 30, 32, and 34 of the sheath 20, the reference outer diameter change amount, which is the amount of change in the outer diameter of each of the regions 30, 32, and 34 when the balloon 14 is expanded from atmospheric pressure to the reference internal pressure, may be used. The larger this reference outer diameter change amount is, the easier it indicates that each of the regions 30, 32, and 34 is to stretch. When measuring the reference outer diameter change amount, the balloon 14 is disposed inside the regions 30, 32, and 34 to be measured, and the internal pressure of the balloon 14 is pressurized from atmospheric pressure until it reaches the reference internal pressure. The amount of change from the maximum outer diameter of the regions 30, 32, and 34 to be measured when the balloon 14 is at atmospheric pressure to the maximum outer diameter of those regions 30, 32, and 34 when the balloon 14 is at the reference internal pressure is defined as the reference outer diameter change amount. For example, under the condition of satisfying the second condition, the statement "making the ease of stretching of the second region 32 higher than that of the first region 30" is synonymous with making the reference outer diameter change amount of the second region 32 larger than that of the first region 30.

[0032] This reference outer diameter change amount also serves as an index indicating the hardness of each of the regions 30, 32, and 34 of the sheath 20 itself. The larger this reference outer diameter change amount is, the lower the hardness of each of the regions 30, 32, and 34 itself indicates.

[0033] In adjusting the ease of stretching of each of the regions 30, 32, and 34, at least one of (1) the hardness of the material of each of the regions 30, 32, and 34 and (2) the thickness of each of the regions 30, 32, and 34 may be adjusted. In order to increase the ease of stretching of each of the regions 30, 32, and 34, a soft material may be adopted as the material of each of the regions 30, 32, and 34, or the thickness of each of the regions 30, 32, and 34 may be made thinner. For example, in order to make the ease of stretching of the second region 32 higher than that of the first region 30, a softer material may be adopted as the material of the second region 32 than that of the first region 30, or the thickness of the second region 32 may be made thinner than the thickness of the first region 30.

[0034] The ease of stretching of each of the regions 30, 32, and 34 of this embodiment decreases in the order of the second region 32, the first region 30, and the third region 34. In order to obtain the sheath 20 having a plurality of regions with different stretching properties in this way, after individually preparing the cylindrical members constituting each of the regions 30, 32, and 34, they may be formed by integrating them by welding, adhesion, or the like. The sheath 20 of this embodiment has a uniform axial distribution of the thickness of each of the regions 30, 32, and 34 and has different hardnesses of the materials of each of the regions 30, 32, and 34 while satisfying such a relationship of ease of stretching. Although the material used for each of the regions 30, 32, and 34 of the sheath 20 is not particularly limited in order to satisfy such a relationship of ease of stretching, for example, rubber-based materials such as polyurethane, polyolefin, silicone, and latex, and other elastomeric polymers may be employed.

[0035] The effect of the sheath 20 described above will be explained. When the sheath 20 covers the balloon 14 with its first region 30 and second region 32 and is in the reference internal pressure state S2 in which the reference internal pressure is applied to the balloon 14, the second region 32 can be in a state of being expanded more than the first region 30. Thereby, when an internal pressure within the internal pressure range including the reference internal pressure is applied to the balloon 14, the balloon 14 and the sheath 20 can form a proximal end side outer diameter changing portion 44a in the expanded body 36.

[0036] Refer to FIGS. 3 and 4. FIG. 4 is an example in which the axial position of the sheath 20 with respect to the balloon 14 is changed to the distal end side more than in FIG. 3 by sliding the sheath 20 with respect to the balloon catheter 10. Thus, the sheath 20 can be axially slid with respect to the balloon catheter 10. Thereby, the axial position of the proximal end side outer diameter changing portion 44a of the expanded body 36 with respect to the balloon 14 can be adjusted. Consequently, the proximal end side outer diameter changing portion 44a can be formed at an arbitrary axial position with respect to the balloon 14, and the degree of freedom during the treatment using the balloon catheter 10 can be increased.

[0037] When the balloon 14 is in the reference internal pressure state S2, the sheath 20 can be in a state where the proximal end portion 40 and the distal end portion 42 of the expansion body 36 are expanded more than the intermediate portion 38. As a result, when an internal pressure within an internal pressure range including the reference internal pressure is applied to the balloon 14, a constriction portion 44 can be formed in the expansion body 36. Further, by axially sliding the sheath 20 with respect to the balloon catheter 10, the axial position of the constriction portion 44 with respect to the balloon 14 can be adjusted. Consequently, the constriction portion 44 can be formed at an arbitrary axial position with respect to the balloon 14, and the degree of freedom during the procedure using the balloon catheter 10 can be increased.

[0038] Thereby, the axial position of the constriction portion 44 can be adjusted according to the width of the distal end side space located on the distal end side of the balloon catheter 10 relative to the constricted portion of the living body organ. For example, consider the case where the axial length of the distal end side space is narrow. In this case, by shifting the axial position of the constriction portion 44 of the expansion body 36 to the distal end side of the balloon 14, the axial length of the expansion body 36 disposed in the distal end side space can be shortened, making it easier to dispose the expansion body 36 within the distal end side space. On the other hand, consider the case where the axial length of the distal end side space is wide. In this case, by shifting the axial position of the constriction portion 44 of the expansion body 36 to the proximal end side, the axial length of the expansion body 36 disposed in the distal end side space can be lengthened, and it may be easier to suppress the slip of the balloon catheter 10 toward the proximal end side.

[0039] Next, other features of the sheath 20 will be described. Referring to FIG. 2, the hardness of each of the regions 30, 32, 34 of the sheath 20 increases in the order of the second region 32, the first region 30, and the third region 34, similar to the relationship of the ease of elongation described above. The hardness of the third region 34 will be higher than the hardness of the second region 32. The hardness of each of the regions 30, 32, 34 itself means the difficulty of deformation when an external force is applied to each of the regions 30, 32, 34, and the harder the hardness, the more difficult it is to deform.

[0040] As a result, compared with the case where the hardness of the third region 34 is made the same as that of the second region 32, the axial load applied to the third region 34 of the sheath 20 is more easily transmitted through the third region 34 to the first and second regions 32 of the sheath 20. Consequently, by applying an axial load to the third region 34 of the sheath 20 outside the body, the first and second regions 30, 32 of the sheath 20 inside the body can be easily slid relative to the balloon catheter 10.

[0041] From such a perspective, the hardness of the third region 34 is preferably higher than the hardness of the first region 30 of the sheath 20. In specifying the high and low relationship of this hardness, the above-mentioned reference outer diameter change amount, which also serves as an index of this hardness, may be measured and evaluated based on the measured value. In addition to this, if possible, in addition to known hardness evaluation methods (for example, three-point bending test, etc.), a hardness evaluation method that can be used in the future may also be used for evaluation.

[0042] A marker portion 50 having radiation impermeability to radiation such as X-rays may be provided in the first region 30 of the sheath 20. In order to achieve this, in this embodiment, the marker portion 50 is provided throughout the first region 30, but the marker portion 50 may also be provided in a part thereof. The marker portion 50 is configured using a material having radiation impermeability. Specifically, the marker portion 50 is configured using, for example, a resin material in which a metal powder having radiation impermeability is kneaded. As the metal powder, for example, barium, gold, platinum, tungsten, or the like may be used.

[0043] As a result, when using the sheath 20 while imaging the inside of the living body using radiation, the position of the first region 30 of the sheath 20 can be grasped by checking the position of the marker portion 50 that appears in the captured image. This is effective when the sheath 20 is disposed inside a blood vessel or the like where the sheath 20 cannot be imaged by an endoscope.

[0044] FIG. 5 is a view showing the expander 36 when a recommended expansion pressure described later is applied to the balloon 14. The outer diameter of the expansion part 14a (barrel part 14c) of the balloon 14 expands so as to approach a predetermined nominal diameter as the internal pressure applied to the balloon 14 approaches the recommended expansion pressure determined in advance from the reference internal pressure, and hardly changes after exceeding the nominal diameter. This recommended expansion pressure refers to what the manufacturer has predetermined as the internal pressure to be applied to the balloon 14 in order to obtain the nominal diameter of the balloon 14. The recommended expansion pressure is appropriately changed according to the use of the balloon 14 and the like, and is set to, for example, 4 atm to 6 atm.

[0045] Let the minimum outer diameter of the middle part 38 of the expander 36 be Rm1, and the maximum outer diameters of the proximal end side part 40 and the distal end side part 42 be Rp1 and Rd1, respectively, when the balloon 14 is in the reference internal pressure state S2. Also, let the minimum outer diameter of the middle part 38 of the expander 36 be Rm2, and the maximum outer diameters of the proximal end side part 40 and the distal end side part 42 be Rp2 and Rd2, respectively, when the recommended expansion pressure is applied to the balloon 14 (hereinafter referred to as the recommended expansion pressure state S3). The minimum outer diameters Rm1 and Rm2 of the middle part 38 are the minimum outer diameters of the first region 30 of the sheath 20 in the middle part 38, and the outer diameter of the balloon 14 in the middle part 38 is not considered. The maximum outer diameter of the proximal end side part 40 is the maximum outer diameter of the second region 32 of the sheath 20 in the proximal end side part 40. The maximum outer diameter of the distal end side part 42 is the maximum outer diameter of the balloon 14 in the distal end side part 42 when there is no other part of the sheath 20 on the distal end side of the first region 30 of the sheath 20. On the other hand, when the fourth region 60 (see FIG. 8) of the sheath 20 exists on the distal end side of the first region 30 of the sheath 20, it is the maximum outer diameter of the fourth region 60 in the distal end side part 42 of the expander 36.

[0046] Consider the case where the balloon 14 is in the reference internal pressure state S2. At this time, the outer diameter difference between the intermediate portion 38 and the proximal end side portion 40 is defined as the proximal end side outer diameter difference ΔRp1 (= Rp1 - Rm1), and the outer diameter difference between the intermediate portion 38 and the distal end side portion 42 is defined as the distal end side outer diameter difference ΔRd1 (= Rd1 - Rm1). The proximal end side outer diameter difference ΔRp1 is a value obtained by subtracting the minimum outer diameter Rm1 of the intermediate portion 38 from the maximum outer diameter Rp1 of the proximal end side portion 40. The distal end side outer diameter difference ΔRd1 is a value obtained by subtracting the minimum outer diameter Rm1 of the intermediate portion 38 from the maximum outer diameter Rd1 of the distal end side portion 42. The proximal end side outer diameter difference ΔRp1 is also the outer diameter difference between the first and second regions 30 and 32 of the sheath 20 when the balloon 14 is in the reference internal pressure state S2. In FIG. 5, for convenience of explanation, half values (ΔRp1 / 2, ΔRd1 / 2) of each of ΔRp1 and ΔRd1 are shown. The same applies to ΔRp2 and ΔRd2 described below.

[0047] Consider the case where the balloon 14 is in the recommended expansion pressure state S3. At this time, the outer diameter difference between the intermediate portion 38 and the proximal end side portion 40 is defined as the proximal end side outer diameter difference ΔRp2 (= Rp2 - Rm2), and the outer diameter difference between the intermediate portion 38 and the distal end side portion 42 is defined as the distal end side outer diameter difference ΔRd2 (= Rd2 - Rm2). The proximal end side outer diameter difference ΔRp2 is a value obtained by subtracting the minimum outer diameter Rm2 of the intermediate portion 38 from the maximum outer diameter Rp2 of the proximal end side portion 40. The distal end side outer diameter difference ΔRd2 is a value obtained by subtracting the minimum outer diameter Rm2 of the intermediate portion 38 from the maximum outer diameter Rd2 of the distal end side portion 42. The proximal end side outer diameter difference ΔRp2 is also the outer diameter difference between the first and second regions 30 and 32 of the sheath 20 when the balloon 14 is in the recommended expansion pressure state S3.

[0048] The sheath 20 can reduce the outer diameter difference between its first region 30 and second region 32 when the balloon 14 is in the recommended expansion pressure state S3 compared to when the balloon 14 is in the reference internal pressure state S2. In other words, the sheath 20 can make the proximal end side outer diameter difference ΔRp2 smaller than the proximal end side outer diameter difference ΔRp1. Thereby, in the process of the internal pressure of the balloon 14 changing from the reference internal pressure to the recommended expansion pressure, the first region 30 can expand the stenosis of the living organ more greatly compared to the case where the outer diameter difference between the first region 30 and the second region 32 remains constant.

[0049] On the condition of meeting this requirement, as described above, when the balloon 14 is in the reference internal pressure state S2, the sheath 20 only needs to be able to be in a state where the second region 32 is expanded more than the first region 30. Thereby, as the internal pressure of the balloon 14 approaches the recommended expansion pressure from the reference internal pressure, the outer diameters of the balloon 14 at the covered portions by the first and second regions 30 and 32 become values close to a common nominal diameter. As a result, the outer diameter difference between the first and second regions 30 and 32 becomes smaller.

[0050] Also, when the balloon 14 is in the recommended expansion pressure state S3, the sheath 20 can make the outer diameter difference between the middle portion 38 and the proximal end side portion 40 and the distal end side portion 42 smaller than when the balloon 14 is in the reference internal pressure state S2. In other words, the sheath 20 can make the proximal end side outer diameter difference ΔRp2 smaller than the proximal end side outer diameter difference ΔRp1, and make the distal end side outer diameter difference ΔRd2 smaller than the distal end side outer diameter difference ΔRd1. The outer diameter differences ΔRp2 and ΔRd2 at the recommended expansion pressure may be zero. Thereby, in the process of the internal pressure of the balloon 14 changing from the reference internal pressure to the recommended expansion pressure, the constricted portion 44 of the expander 36 can greatly expand the stenotic portion of the living organ.

[0051] On the condition of meeting this requirement as well, as described above, when the balloon 14 is in the reference internal pressure state S2, the sheath 20 only needs to be able to be in a state where the proximal end side portion 40 and the distal end side portion 42 are expanded more than the middle portion 38. Thereby, as the internal pressure of the balloon 14 approaches the recommended expansion pressure from the reference internal pressure, the outer diameters of the balloon 14 at the respective portions 38, 40, and 42 become values close to a common nominal diameter. As a result, the outer diameter differences between the respective portions 38, 40, and 42 can be made smaller.

[0052] Note that a constricted portion 44 is formed in the expander 36 at least in part of the internal pressure range from the reference internal pressure to the recommended expansion pressure of the balloon 14.

[0053] An example of a treatment using the balloon catheter unit 22 described above will be described. The procedure for expanding a stenosis in a living organ will be described. First, the balloon 14 of the balloon catheter 10 is placed within the stenosis of the living organ. At this time, when used for a digestive organ, for example, while confirming the position of the balloon 14 relative to the stenosis of the living organ using an endoscope, the balloon catheter 10 may be fed out from the endoscope to place the balloon 14 within the stenosis. Next, while guiding the sheath 20 with the balloon catheter 10, the sheath 20 is moved toward the distal end side to move the sheath 20 close to the balloon 14. After that, the axial position of the sheath 20 relative to the balloon catheter 10 is adjusted so that a part of the balloon 14 can be covered by the first and second regions 30, 32 of the sheath 20. At this time, as described above, the axial position of the sheath 20 relative to the balloon catheter 10 is adjusted by applying an axial load to the proximal end portion of the sheath 20 outside the body. After that, the balloon 14 is expanded by applying an internal pressure within the internal pressure range from the reference internal pressure to the recommended expansion pressure within the balloon 14. Thereby, a constricted portion 44 is formed in the expander 36, and while placing the stenosis of the living organ inside thereof, the stenosis is expanded. In this state, if necessary, by bringing the internal pressure of the balloon 14 closer to the recommended expansion pressure, the stenosis of the living organ may be greatly expanded by the constricted portion 44 of the expander 36.

[0054] Whether the balloon 14 is in the reference internal pressure state may be determined as follows. The inflator used as the fluid supply device may be equipped with a pressure gauge capable of displaying the pressure corresponding to the amount of pressurization when pressurizing the internal pressure of the balloon 14 by supplying fluid. Consider the case where, in an atmospheric pressure environment, the balloon 14 is in a contracted and unexpanded state without supplying fluid by the inflator. In this case, since the internal pressure of the balloon 14 is not pressurized by the pressure gauge of the inflator, it is displayed that the pressure corresponding to the amount of pressurization is 0 atm. When the internal pressure of the unexpanded balloon 14 is pressurized by 1 atm by the inflator in this way, ideally, the internal pressure of the balloon 14 becomes the reference internal pressure state of 2 atm. At this time, the pressure gauge of the inflator displays that 1 atm has been pressurized as the pressure corresponding to the amount of pressurization. Thus, when it is displayed on the pressure gauge of the inflator that 1 atm has been pressurized by supplying fluid to the unexpanded balloon 14 in an atmospheric pressure environment, it may be regarded that the internal pressure of the balloon 14 is in the reference internal pressure state of 2 atm. In addition to this, a pressure sensor capable of detecting the internal pressure of the balloon 14 may be provided inside the balloon or the like, and when the detected value of the internal pressure of the balloon detected by the pressure sensor is 2 atm, it may be determined that the internal pressure of the balloon 14 is in the reference internal pressure state of 2 atm.

[0055] (Second Embodiment) In the embodiments hereinafter, among the components described in the first embodiment, the components not described below may have the same content applied as in the first embodiment. Refer to FIGS. 6 and 7. In the first embodiment, the case where the balloon 14 is not covered by the third region 34 of the sheath 20 was described. By sliding the sheath 20 axially with respect to the balloon catheter 10, at least a part of the expansion portion 14a of the balloon 14 may be covered by each of the first, second, and third regions 30, 32, and 34 of the sheath 20. At this time, as in this embodiment, while leaving a part of the expansion portion 14a of the balloon 14 on both axial sides with respect to the first region 30 of the balloon 14, a part of the axial range from the proximal end to the distal end side of the expansion portion 14a of the balloon 14 may be covered by the third region 34. In order to achieve this, the sheath 20 of the present embodiment has a shorter axial length of the second region 32 of the sheath 20 than the sheath 20 of the first embodiment.

[0056] Thereby, when the balloon 14 is in the reference internal pressure state S2, the third region 34 can be in a state of restraining the expansion of the balloon 14 so as to have an outer diameter equal to or less than the outer diameter (minimum outer diameter) of the first region 30. At this time, the proximal end side portion 40 and the distal end side portion 42 of the expansion body 36 are in a state of expanding more than the third region 34 of the sheath 20. In order to satisfy this condition, it is only necessary to make the third region 34 less likely to expand than the first region 30 when the sheath 20 expands in the radial direction. The lower the ease of expansion of the third region 34 is than the ease of expansion of the first region 30, the more difficult it is for the third region 34 to expand more than the first region 30 together with a part of the balloon 14, and the easier it is to satisfy the above-described condition. Note that the third region 34 of the sheath 20 may be non-expandable by the balloon 14 or may be expandable by the balloon 14 until the internal pressure of the balloon 14 reaches the reference internal pressure from the atmospheric pressure.

[0057] The range from the tip of the balloon 14 to the proximal end of the axial range where the balloon 14 and the second region 32 of the sheath 20 overlap is defined as the expansion range R1 of the expander 36. The longer the axial coverage range of the balloon 14 by the third region 34 of the sheath 20, the shorter the axial dimension of the expansion range R1 of the expander 36 can be. Also, by sliding the sheath 20 relative to the balloon catheter 10, the coverage range of the balloon 14 by the third region 34 of the sheath 20 can be adjusted, and thereby the axial dimension of the expansion range R1 of the expander 36 can be adjusted. This expansion range R1, when the expander 36 expands, facilitates positioning with respect to the living organ by the constriction portion 44 of the expander 36 and becomes a portion that is more easily applied to the living organ by the portions 38, 40, 42 having a larger outer diameter than a certain location of the third region 34.

[0058] In addition to this, the sheath 20 of the present embodiment can also obtain the same effects as the sheath 20 of the first embodiment.

[0059] (Third Embodiment) Refer to FIG. 8. FIG. 8 shows the balloon 14 in the reference internal pressure state S2. The sheath 20 of the present embodiment includes a fourth region 60 provided on the distal end side of the first region 30 in addition to the first region 30, the second region 32, and the third region 34 of the sheath 20 of the first embodiment. As described above, the fourth region 60 constitutes the distal end side portion 42 of the expander 36. The sheath 20 can be in a state where the fourth region 60 is expanded more than the first region 30 when the balloon 14 is in the reference internal pressure state S2 with at least a part of the balloon 14 covered by the first, second, and fourth regions 30, 32, 60. Thereby, a distal end side outer diameter changing portion 44b is formed in the distal end side portion 42 of the expander 36. On the condition of satisfying this, as described in the third condition above, the ease of elongation of the fourth region 60 and the first region 30 may be adjusted.

[0060] In this form, when the balloon 14 is in the reference internal pressure state S2, the maximum outer diameter R60 of the fourth region 60 of the sheath 20 can be made smaller than the maximum outer diameter R32 of the second region 32. To satisfy this condition, the fourth region 60 may be made less likely to expand than the second region 32 when the sheath 20 expands in the radial direction. Thereby, while forming the constricted portion 44 in the expandable body 36, by reducing the outer diameter of the distal end side portion 42 of the expandable body 36, it is possible to make the distal end side portion 42 less likely to interfere with the living organ. In addition to this, when the balloon 14 is in the reference internal pressure state S2, the maximum outer diameter S60 of the fourth region 60 of the sheath 20 may be made the same as the maximum outer diameter R32 of the second region 32.

[0061] Next, modified forms of each of the components described so far will be described.

[0062] The sheath 20 may not include the third region 34, and the second region 32 may be continuous to the proximal end of the sheath 20. The hardness of the third region 34 may be the same as the hardness of the second region 32. The hardness of the third region 34 may be higher than the hardness of the second region 32 and lower than the hardness of the first region 30.

[0063] A load transmission member capable of transmitting an axial load applied from the proximal end side of the sheath 20 to the first region 30 of the sheath 20 may be attached to the sheath 20. This load transmission member can transmit an axial load applied outside the body to the first region 30 of the sheath 20 when the balloon 14 is disposed at a location in the body to be treated by the balloon catheter 10. The load transmission member may be embedded in a portion between the outer peripheral surface of the sheath 20 and the sheath lumen 26, or may be passed through the sheath lumen 26. The load transmission member is constituted by, for example, a wire material made of metal, resin, or the like.

[0064] The above embodiments and modified forms are illustrative. The technical ideas abstracted from these should not be construed as being limited to the content of the embodiments and modified forms. Many design changes such as changes, additions, deletions, etc. of components are possible for the content of the embodiments and modified forms. In the foregoing embodiments, with regard to the content for which such design changes are possible, notations such as "embodiment" and "this form" are attached and emphasized. However, design changes are also permitted for the content without such notations. The hatching attached to the cross-section of the drawing does not limit the material of the object to which the hatching is attached. Any combination of the above components is also effective. For example, any explanatory items of other embodiments may be combined with the embodiments, or any explanatory items of the embodiments and other modified forms may be combined with the modified forms.

Explanation of Reference Numerals

[0065] 10…Balloon catheter, 14…Balloon, 20…Sheath, 22…Balloon catheter unit, 30…First region, 32…Second region, 34…Third region, 36…Expansion body, 38…Intermediate portion, 40…Proximal end side portion, 42…Distal end side portion, 44…Expansion body, 50…Marker portion.

Claims

1. A sheath used for a balloon catheter, a first region, and a second region provided on the proximal side of the first region, and the sheath is axially slidable with respect to the balloon catheter when the balloon of the balloon catheter is in a contracted state, and the sheath is a sheath that can be in a state where at least a part of the second region is expanded more than the first region when a reference internal pressure of 2.0 atm is applied to the balloon in a state where the balloon is covered by the first region and the second region.

2. The sheath according to claim 1, further comprising a third region provided on the proximal side of the second region, and the hardness of the third region is higher than the hardness of the second region.

3. The sheath according to claim 2, wherein the hardness of the third region is higher than the hardness of the first region.

4. The sheath according to claim 1, further comprising a third region provided on the proximal side of the second region, and when the reference internal pressure is applied to the balloon in a state where at least a part of the balloon is covered by each of the first region, the second region, and the third region, the third region can be in a state of restricting the expansion of the balloon so as to have an outer diameter equal to or less than the outer diameter of the first region.

5. The sheath according to claim 1, wherein when a recommended expansion pressure higher than the reference internal pressure is applied to the balloon, the outer diameter difference between the first region and the second region can be made smaller than when the reference internal pressure is applied to the balloon.

6. The sheath according to claim 1, wherein a marker portion having radiation impermeability is provided in the first region.

7. When the sheath covers the balloon, an expansion body composed of the balloon and the sheath is provided in a certain axial range of the balloon, and the expansion body includes an intermediate portion provided in a certain axial range of the first region, and a proximal end side portion and a distal end side portion adjacent to both axial sides of the intermediate portion. The sheath according to claim 1, which can be in a state where the proximal end side portion and the distal end side portion are expanded more than the intermediate portion when the reference internal pressure is applied to the balloon.

8. The sheath according to any one of claims 1 to 7, and ​ ​ ​ ​ A balloon catheter unit comprising the balloon catheter according to any one of claims 1 to 7.

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