CN113974766B - Thrombolysis catheter - Google Patents

Abstract

The present invention provides a thrombus removal catheter, which includes: a blocking sheath, a dilator and a thrombus removal device; the blocking sheath includes a sheath tube, a balloon is provided at the distal end of the sheath tube, an opening is provided at the proximal end, at least two cavities are provided in the sheath tube, the distal end of the first cavity is connected to the inner cavity of the balloon, and the second cavity is axially connected to the opening; the dilator can extend into the second cavity of the sheath tube from the opening; the thrombus removal device can extend into the second cavity from the opening of the handle, and includes a coaxially sleeved outer tube and an inner tube, and a dense mesh thrombus removal device, one end of the dense mesh thrombus removal device is connected to the distal end of the inner tube, and the other end of the dense mesh thrombus removal device is connected to the distal end of the outer tube, and pulling the inner tube can expand or relax the dense mesh thrombus removal device. The thrombus removal catheter of the present invention can effectively improve the thrombus removal rate and reduce blood loss.

Description

Embolectomy catheter

The filing date of the parent application of this divisional application is January 19, 2018, the application number is 201810052511.6, and the name of the invention is "Thrombectomy catheter and thrombectomy device for thrombectomy catheter".

Technical Field

The present invention relates to the technical field of thrombus removal, and in particular to a thrombus removal catheter.

Background technique

Thromboembolic diseases include arterial embolism, arterial thrombosis and venous thromboembolism. Existing treatment methods mainly include vascular embolectomy, catheter-directed thrombolysis and percutaneous mechanical thrombectomy. Open embolectomy requires anatomical separation and vascular incision, such as femoral artery, femoral vein or brachial artery incision. With the development of intravascular interventional technology and the innovation of materials, this open surgical method has gradually been replaced by minimally invasive interventional intravascular treatment, namely catheter-directed thrombolysis and percutaneous mechanical thrombectomy. Catheter-directed thrombolysis has a high risk of bleeding due to thrombolytic drugs and extremely strict surgical indications. A large proportion of patients have contraindications to catheter-directed thrombolysis, so many patients cannot benefit from it.

Stent-type thrombectomy is a recently emerged mechanical thrombectomy method. With the assistance of medical imaging technology, this method delivers a stent-type thrombectomy device to the site of vascular embolism via a catheter and releases it. The stent-type thrombectomy device unfolds on its own and relies on its own expansion force to engage with the thrombus. The thrombectomy device is then retrieved and the thrombus is removed.

Chinese invention patent CN103417257B discloses an intracranial vascular thrombectomy catheter, the spiral mesh ring units of which have different distribution densities, with denser distribution at the distal end and relatively sparse distribution at the proximal end, which can effectively prevent small thrombi from falling off. Chinese invention patent CN103997976A discloses a thrombectomy cage with a slender axis and a circumference, including slender components that together define a plurality of open units, and the thrombectomy cage can effectively remove emboli. Chinese invention patent CN105726088A discloses a thrombus removal device, including a mesh self-expanding stent and a core wire, the stent is cylindrical in the expanded state, has an opening at the proximal end, and is closed at the distal end, the thrombus removal device can evenly embed the thrombus in the axial mesh of the stent, and the generated thrombus fragments enter the interior through the proximal opening of the stent and are collected by the closed distal end.

As mentioned above, due to structural limitations, the current stent-type thrombectomy device or thrombectomy catheter simply uses a sparse stent rod to capture the thrombus or negative pressure suction, and pulls the thrombus to bring the thrombus out of the body. However, when removing the thrombus, the force exerted by the stent-type thrombectomy device or thrombectomy catheter on the thrombus is uneven, and the thrombus is easy to fall off the thrombectomy device, or thrombus fragments are generated to block the distal blood vessels, or enter other blood vessels. Long-term negative pressure will also lead to excessive blood loss. In addition, the current stent-type thrombectomy device or thrombectomy catheter is not effective for old thrombi and large-scale embolism. Based on existing medical knowledge, deep vein thrombosis often has a large volume, and the acute thrombus is soft and fragile; arterial thrombosis often has a small volume, and the acute thrombus is soft, and old thrombi often adhere to the blood vessel wall. At present, the sparsely structured stent-type thrombectomy catheter is usually developed for arterial thrombi, and the effect is often not ideal for large-volume venous thrombosis. Therefore, a thrombectomy catheter that is easy to remove thrombi is needed.

Summary of the invention

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a thrombus removal catheter for solving the problems of thrombus shedding and excessive bleeding when using the stent thrombus removal device in the prior art.

To achieve the above objectives and other related objectives, the present invention provides a thrombectomy catheter, which includes:

The blocking sheath comprises a sheath tube, wherein a balloon is arranged at the distal end of the sheath tube, and an opening is arranged at the proximal end of the sheath tube; at least two axially extending cavities are arranged in the sheath tube, wherein the distal end of the first cavity is communicated with the inner cavity of the balloon, and the second cavity is axially communicated with the opening;

a dilator, the dilator being extendable from the opening into the second cavity, the distal end of the dilator passing through the second cavity and blocking the second cavity;

The thrombus remover comprises an outer tube and an inner tube which are coaxially sleeved, and an expandable dense mesh thrombus remover. The inner tube can move axially relative to the outer tube, one end of the dense mesh thrombus remover is connected to the distal end of the inner tube, and the other end of the dense mesh thrombus remover is connected to the distal end of the outer tube. Pulling the inner tube can expand or relax the dense mesh thrombus remover. The thrombus remover can be extended into the second cavity from the opening, the distal end of the outer tube passes through the second cavity, and the proximal end of the outer tube is exposed outside the opening.

Preferably, the proximal end of the sheath is connected to a handle, and the opening is arranged on the handle; the first cavity connects the inner cavity of the balloon and the balloon filling connector connected to the handle; the proximal end of the second cavity is connected to the negative pressure suction device connected to the handle.

Preferably, a connecting buckle is provided at the opening of the handle, a hand-held portion is connected to the proximal end of the expander, and a connecting portion that cooperates and is fixed with the connecting buckle is provided on the hand-held portion.

Preferably, the outer diameter of the expander matches the inner diameter of the second cavity.

Preferably, the expander is made of a thermoplastic elastomer, and the thermoplastic elastomer is filled with a developer-containing material such as barium sulfate, bismuth oxide or bismuth oxychloride.

Preferably, the dense mesh thrombus removal member is woven from superelastic memory nickel-titanium alloy wire mixed with platinum-iridium alloy wire, gold wire or stainless steel wire, and the platinum-iridium alloy wire, gold wire or stainless steel wire is used for development under an X-ray machine.

Preferably, a hand piece is connected to the proximal end of the outer tube, and a positioning portion for locking the inner tube is provided on the hand piece.

Preferably, both ends of the inner tube are exposed outside the two ends of the outer tube, and the proximal end of the inner tube is connected to a pull-out handle.

Preferably, the sheath tube, the inner tube and the outer tube are all made of polyamide thermoplastic elastomer.

Preferably, the distal ends of the sheath tube and the inner tube are tapered.

As described above, the thrombus removal catheter of the present invention has the following beneficial effects: blood flow is blocked by filling the balloon at the distal end of the sheath, so that the thrombus is surrounded by the dense mesh thrombus removal component and the balloon, which makes it easy to remove the thrombus. At the same time, the dense mesh thrombus removal component allows blood to pass through the mesh holes on it, which can effectively prevent the thrombus from overflowing to other blood vessels during the thrombus removal process. The dense mesh thrombus removal component and the blocking balloon can simultaneously cooperate with negative pressure suction to reduce the blood loss to a minimum. The thrombus removal device has an inner tube with a thinner tip and an outer tube with a thinner body, which can reach deeper positions of the thrombus. It is suitable for thrombus removal of large and medium-sized blood vessels, including relatively old lesions, and is particularly suitable for absorbing thrombi on limbs, such as thrombi with larger volumes in veins. The thrombus removal catheter of the present invention is a passive thrombus removal device with low cost and simple operation, which can greatly reduce the cost of thrombus removal surgery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the dilator of the present invention being inserted into a blocking sheath.

FIG. 2 is a cross-sectional view taken along line AA in FIG. 1 .

FIG. 3 is a schematic diagram of a blocking sheath according to the present invention.

FIG. 4 is a schematic diagram of a dilator according to the present invention.

FIG. 5 is a schematic diagram of the thrombus remover of the present invention.

FIG. 6 is a cross-sectional view taken along line BB in FIG. 5 .

FIG. 7 is a schematic diagram showing the thrombus remover of the present invention being inserted into the blocking sheath and in a relaxed state.

FIG. 8 is a schematic diagram showing the thrombus remover of the present invention being inserted into the blocking sheath and in an expanded state.

Component number description:

1 Dilator

2 Development Mark

3 Balloon

4 Sheath

5 Negative pressure suction device

6 Handle

7 Balloon inflation connector

8 Handheld

9 Two-way

10 Connecting pipe

11 Connection buckle

12 Connection

121 Notch

13 dense mesh thrombus remover

14 Outer tube

15 Handpiece

16 Inner tube

17 Pull-out handle

Detailed ways

The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

Please refer to Figures 1 to 8. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

For ease of description, in this specification, the end of the embolectomy catheter along its length, when in use, that is away from the operator is defined as the distal end, and the end held by the operator is defined as the proximal end.

As shown in FIGS. 1 to 8 , the present invention provides a thrombectomy catheter, which includes:

The blocking sheath, as shown in FIG3 , comprises a sheath tube 4, a balloon 3 is provided at the distal end of the sheath tube 4, and preferably, a handle 6 is connected to the proximal end of the sheath tube 4; at least two axially extending cavities are provided in the sheath tube 4, the distal end of the first cavity is communicated with the inner cavity of the balloon 3, preferably, the proximal end of the first cavity is communicated with the balloon filling joint 7 connected to the handle 6, preferably, developing marks 2 are provided on the sheath tube 4 on both sides of the balloon 3; preferably, the proximal end of the second cavity is communicated with the negative pressure suction device 5 connected to the handle 6, and the handle 6 is also provided with an opening portion axially communicated with the second cavity;

The dilator 1 preferably has an outer diameter that matches the inner diameter of the second cavity of the sheath tube 4, and can be inserted into the second cavity of the sheath tube 4 from the opening of the handle 6, and the distal end of the dilator 1 passes through the second cavity of the sheath tube 4 and blocks the second cavity of the sheath tube 4;

The thrombus remover, as shown in FIG5 , comprises an outer tube 14 and an inner tube 16 which are coaxially sleeved, and an expandable dense mesh thrombus remover 13, and both ends of the inner tube 16 are exposed outside the two ends of the outer tube 14, and the inner tube 16 can move axially relative to the outer tube 14 or can be positioned relative to each other, one end of the dense mesh thrombus remover 13 is connected to the distal end of the inner tube 16, and the other end of the dense mesh thrombus remover 13 is connected to the distal end of the outer tube 16, and pulling the inner tube 16 can expand or relax the mesh thrombus remover 13; the thrombus remover can be extended into the second cavity from the opening of the handle 6, and the distal end of the outer tube 14 passes through the second cavity, as shown in FIGS. 7 and 8, and the proximal end of the outer tube 14 is exposed outside the opening of the handle 6.

The thrombus removal catheter of the present invention has three components, namely the above-mentioned blocking sheath, dilator 1 and the above-mentioned thrombus removal device. The balloon 3 at the distal end of the sheath 4 is filled to serve as a sealing plug for the proximal end of the thrombus, thereby blocking the blood flow and enclosing the thrombus between the dense mesh thrombus removal member 13 and the balloon 3, which is easy to remove the thrombus. At the same time, the dense mesh thrombus removal member 13 allows blood to pass through the mesh holes on it, and the dense mesh thrombus removal member 13 has a density. When performing a thrombus removal operation, the thrombus is easy to form a stopper film on the surface of the dense mesh thrombus removal member 13, which can effectively prevent the thrombus from crossing the dense mesh thrombus removal member to overflow into other blood vessels during the removal process. The dense mesh thrombus removal member and the blocking balloon thrombus removal are combined with negative pressure suction to minimize blood loss, which is particularly suitable for absorbing large-volume thrombi in veins.

In this embodiment, a connection buckle 11 is provided at the opening of the handle 6, and a connection portion 12 that cooperates with the connection buckle 11 is provided on the dilator 1. The dilator 1 is fixed to the blocking sheath by the connection portion 12 and the connection buckle 11, so as to facilitate insertion into the blood vessel. In this embodiment, a protrusion is provided on the connection buckle 11, and a notch 121 is provided on the connection buckle 12. When the dilator 1 is inserted into the second cavity of the sheath tube 4 from the opening of the handle 6, the protrusion is engaged in the notch 121, so that the dilator 1 is positioned and connected to the blocking sheath. The cooperation of the protrusion and the notch 121 also facilitates the separation of the two, and the dilator 1 is easily withdrawn from the blocking sheath.

The positioning connection between the handle 6 and the expander 1 is not limited to the cooperation between the connection buckle 12 and the connection part 11, and can also be achieved by providing a rotatable positioning part, which can lock the expander after being tightened. The handle 6 can also lock the thrombus remover by rotating the positioning part.

In order to facilitate the insertion of the dilator 1, a hand-held portion 8 is connected to the proximal end of the dilator 1, and the operator can hold the hand-held portion 8 and insert the dilator 1 into the sheath 4 from the opening of the handle 6. In order to facilitate medical imaging, the dilator 1 in this embodiment is made of thermoplastic elastomers such as polyethylene or polyurethane, and the thermoplastic elastomer is filled with barium sulfate, bismuth oxide or bismuth oxychloride containing developer materials.

In this embodiment, the sheath tube 4 in the blocking sheath is a double-chamber structure or a multi-chamber structure, wherein one of the cavities, namely the first cavity, is used as a channel for filling the balloon 3, and the other cavity, namely the second cavity, is used as a working cavity for inserting the dilator 1 or the thrombus remover or other medical devices into and out of the blood vessel, and the sheath tube 4 is made of polyurethane or polyamide thermoplastic elastomer. In this embodiment, the material of the balloon 3 is a thermoplastic elastomer such as natural latex, synthetic rubber, silicone or polyurethane, and the contrast agent is injected through the balloon filling cavity joint 7 on the handle 6 to fill and expand the compliant balloon to form a blood circulation blocking effect. In order to facilitate the extraction of thrombus, in this embodiment, the negative pressure suction device 5 is connected to the handle 6 through a connecting tube 10, and the negative pressure suction device 5 is also connected with two passes 9, which are convenient for connecting with an electric negative pressure aspirator to form a suction negative pressure, so that the thrombus flows more efficiently from the blocking sheath into the collection device of the negative pressure suction device 5.

In the above-mentioned thrombus remover in this embodiment, the dense mesh thrombus remover 13 is woven from superelastic memory nickel-titanium alloy wire, and a certain amount of platinum-iridium alloy wire, gold wire or stainless steel wire is mixed in for development under an X-ray machine, which allows blood to flow through the dense mesh thrombus remover during thrombus removal, and can effectively prevent the thrombus from overflowing to other blood vessels during the thrombus removal process; the dense mesh thrombus remover can effectively reduce blood loss and improve the thrombus suction effect while removing the thrombus. The superelastic memory nickel-titanium alloy wire used in the dense mesh thrombus remover in this embodiment is very fine, and the pore size of the woven mesh is approximately between 0.3-1.0mm, that is, the dense mesh thrombus remover in this embodiment is a dense mesh that can allow blood to pass through and prevent thrombus blocks from passing through. The outer tube 14 and the inner tube 16 are both made of polyamide thermoplastic elastomer. The entire thrombus remover is made of soft material, which reduces the damage to the vascular endothelium during the thrombus removal process.

In order to facilitate the expansion and relaxation of the dense mesh thrombus removal device, a handpiece 15 is connected to the proximal end of the outer tube 14 in this embodiment, as shown in FIG5 , and a positioning portion for locking the inner tube 16 is provided at the proximal end of the handpiece 15. In this embodiment, the handpiece 15 can be used as a handle to facilitate the operator to take the thrombus removal device. The positioning portion in the handpiece 15 can position the inner tube 16 and the outer tube 14, so that the mesh thrombus removal device 13 can be kept in an expanded state, which is convenient for pulling the thrombus into the blocking sheath. The positioning portion can be a rotating or switch-type locking member, and the inner tube and the outer tube are locked by rotation or switching.

As shown in Figures 5 and 6, in this embodiment, the inner tube 16 is inserted into the outer tube 14, and the length of the inner tube 16 is longer than that of the outer tube 14. Both ends of the inner tube 16 are located outside the outer tube 14. One end of the dense mesh thrombus removal member 13 is connected to the distal end of the inner tube 16, and the other end of the dense mesh thrombus removal member 13 is connected to the distal end of the outer tube 14. The relative distance between the distal end of the inner tube 16 and the distal end of the outer tube is changed by pulling the inner tube 16, so that the dense mesh thrombus removal member 13 can be expanded and relaxed. When the inner tube is pulled in the direction of the arrow in Figure 5, the dense mesh thrombus removal member expands, and vice versa.

To facilitate the pulling of the inner tube, as shown in Fig. 5, a pulling handle 17 is connected to the proximal end of the inner tube 16 in this embodiment. To facilitate the thrombus remover to pass through the thrombus and move to the distal end of the thrombus, the distal end of the inner tube 16 in this embodiment is rounded and has a certain taper, that is, its end is tapered.

The specific process of extracting thrombus from blood vessel by using the above-mentioned thrombectomy catheter is as follows:

After puncturing and cannulating the blood vessel and understanding the location of the thrombus and the surrounding blood vessels through arterial or venography, the dilator 1 is first inserted into the second cavity of the sheath 4, as shown in Figures 1 and 2, which show the state of the dilator 1 inserted into the blocking sheath. Then, under the guidance of the guide wire, the sheath 4 is guided to the proximal end of the thrombus; physiological saline or other suitable liquid medicine is connected to the balloon cavity connector 7 to fill the balloon 3 to the size of the inner diameter of the blood vessel, so that the balloon blocks the blood vessel proximal to the thrombus and blocks the blood flow; the dilator 1 is withdrawn from the blocking sheath, and the thrombus remover is placed along the guide wire, as shown in Figure 7, and the dense mesh thrombus remover 13 in the thrombus remover is inserted. The thrombus is passed through the thrombus and placed at the far end of the thrombus; the inner tube 16 of the thrombus remover is pulled outward, as shown in FIG8 , the dense mesh thrombus remover 13 expands, the inner tube 16 and the outer tube 14 are locked, and the dense mesh thrombus remover 13 is kept in an expanded state; the outer tube 14 is pulled outward to collect the thrombus into the sheath tube 4 of the blocking sheath, and the thrombus is discharged into the negative pressure suction device 5 by negative pressure suction at the same time, and when the thrombus is pulled, blood can pass through the dense mesh thrombus remover 13 to reduce the amount of blood loss, but the block thrombus will be sucked out with the suction; after the thrombus is removed from a certain section of the blood vessel, the balloon on the blocking sheath is filled and released to move to the next section of the thrombus for thrombus removal. The thinner tip and tube body of the thrombus remover in this embodiment can reach a deeper position of the thrombus.

In summary, the thrombus removal catheter and the thrombus removal device used for the thrombus removal catheter of the present invention block the blood flow by filling the balloon at the distal end of the blocking sheath. During the thrombus removal process, the soft thrombus removal device reduces the damage to the vascular endothelium; the dense mesh thrombus removal device allows blood to pass through the mesh holes on it, and can effectively prevent the thrombus embolus from overflowing to other parts of the blood vessels during the thrombus removal process. The dense mesh thrombus removal device cooperates with negative pressure suction while removing the thrombus, which is conducive to the removal of the thrombus and reduces the blood loss to a minimum; the inner tube of the thrombus removal device has a thinner tip and tube body, which can reach a deeper position of the thrombus; it is suitable for thrombus removal of large and medium-sized blood vessels, including relatively old lesions; the present invention is a passive thrombus removal device with low cost and simple operation, which can greatly reduce the cost of thrombus removal surgery; it can efficiently remove large-volume thrombi, reduce valve damage, use less thrombolytic drugs, less blood loss, less trauma, and faster recovery period. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims (7)

1. A thrombectomy catheter, comprising: The blocking sheath comprises a sheath tube, wherein a balloon is arranged at the distal end of the sheath tube, and an opening is arranged at the proximal end of the sheath tube; at least two axially extending cavities are arranged in the sheath tube, wherein the distal end of the first cavity is connected to the inner cavity of the balloon, and the second cavity is axially connected to the opening; a dilator, the dilator being extendable from the opening into the second cavity, the outer diameter of the dilator matching the inner diameter of the second cavity, the distal end of the dilator passing through the second cavity and blocking it; The thrombus remover comprises an outer tube and an inner tube which are coaxially sleeved, and an expandable dense mesh thrombus remover, wherein the dense mesh thrombus remover is woven from superelastic memory nickel-titanium alloy wire mixed with platinum-iridium alloy wire, gold wire or stainless steel wire, the inner tube can move axially relative to the outer tube, one end of the dense mesh thrombus remover is connected to the distal end of the inner tube, and the other end of the dense mesh thrombus remover is connected to the distal end of the outer tube, and pulling the inner tube can expand or relax the dense mesh thrombus remover, and a handpiece is connected to the proximal end of the outer tube, and the proximal end of the handpiece A positioning part is provided for locking the inner tube, and the positioning part includes a rotating or switch-type locking part, and the inner tube and the outer tube are locked by rotation or switch; the dense mesh thrombus removal part allows blood to pass through the mesh holes on it, and the thrombus forms a stopper film on the surface of the dense mesh thrombus removal part; after the dilator is withdrawn from the blocking sheath, the thrombus removal part can be extended into the second cavity from the opening, the distal end of the outer tube passes through the second cavity, and the proximal end of the outer tube is exposed outside the opening; During the thrombus removal process, the dense mesh thrombus removal device is used to pass through the thrombus and is placed at the distal end of the thrombus and then expands. The dense mesh thrombus removal device and the balloon can surround large-capacity thrombi in medium and large veins between the two. The dense mesh thrombus removal device and the balloon cooperate with negative pressure suction while removing the thrombus to minimize blood loss, and are suitable for absorbing large-capacity thrombi in veins. 2. The thrombectomy catheter according to claim 1 is characterized in that a handle is connected to the proximal end of the sheath, and the opening is arranged on the handle; the first cavity connects the inner cavity of the balloon and the balloon filling connector connected to the handle, and the proximal end of the second cavity is connected to the negative pressure suction device connected to the handle. 3. The thrombectomy catheter according to claim 2 is characterized in that a connecting buckle is provided on the handle, a hand-held portion is connected to the proximal end of the dilator, and a connecting portion that cooperates and is fixed with the connecting buckle is provided on the hand-held portion. 4. The thrombectomy catheter according to claim 1 is characterized in that the dilator is made of a thermoplastic elastomer, and the thermoplastic elastomer is filled with a developer-containing material such as barium sulfate, bismuth oxide or bismuth oxychloride. 5. The thrombus removal catheter according to claim 1 is characterized in that both ends of the inner tube are exposed outside the two ends of the outer tube, and the proximal end of the inner tube is connected to a pulling handle. 6. The thrombectomy catheter according to claim 1 is characterized in that the sheath tube, the inner tube and the outer tube are all made of polyurethane or polyamide thermoplastic elastomer. 7. The thrombectomy catheter according to claim 1 is characterized in that the distal ends of the sheath tube and the inner tube are tapered.