Patent Publication Number: US-2009234282-A1

Title: Outer Catheter Shaft to Balloon Joint

Description:
FIELD OF THE INVENTION 
     The invention relates generally to a medical device. More particularly, the present invention relates to a catheter having an inflatable balloon at the distal end thereof joined on to the inside of an outer catheter shaft. In addition, the present invention relates to a balloon as bonded to the outer catheter shaft in an unexpanded configuration that has uniform dimensions including wall thickness, inner diameter, and outer diameter along its full length. 
     BACKGROUND OF THE INVENTION 
     Cardiovascular disease, including atherosclerosis, is the leading cause of death in the U.S. One method for treating atherosclerosis and other forms of coronary narrowing is percutaneous transluminal coronary angioplasty, commonly referred to as “angioplasty” or “PTCA”. The objective in angioplasty is to enlarge the lumen of the affected coronary artery by radial hydraulic expansion. The procedure is accomplished by inflating a balloon of a balloon catheter within the narrowed lumen of the coronary artery. Radial expansion of the coronary artery occurs in several different dimensions, and is related to the nature of the plaque. Soft, fatty plaque deposits are flattened by the balloon, while hardened deposits are cracked and split to enlarge the lumen. 
     In addition to PTCA, balloon catheters are used for delivery of stents or grafts, therapeutic drugs (such as vaso-occlusion agents or tumor treatment drugs) and radiopaque agents for radiographic viewing. Other uses for such catheters are well known in the art. 
     In the design of catheter balloons, balloon characteristics such as strength, flexibility and compliance must be tailored to provide optimal performance for a particular application. In order to treat very tight stenoses with small openings, there has been a continuing effort to reduce the profile of the balloon catheter so that the balloon can reach and pass through the small opening of the stenoses. 
     Catheter balloons preferably have high flexibility and softness for improved ability to track the tortuous anatomy and cross lesions in the uninflated state. The anatomy of coronary arteries varies widely from patient to patient. Often a patient&#39;s coronary arteries are irregularly shaped, highly tortuous and very narrow. The tortuous configuration of the arteries may present difficulties to the physician in advancement of the balloon catheter to a treatment site. A highly tortuous coronary anatomy typically will present considerable resistance to advancement of the catheter over the guidewire. Therefore, it is important for the balloon catheter to be flexible and have a smooth profile to enable the balloon to be tracked to the treatment site. However, it is also important for a catheter shaft to be stiff enough to push the catheter into the vessel in a controlled manner from a position far away from the distalmost point of the catheter. 
     One factor that affects the profile of the balloon catheter is the joint between the proximal balloon neck and the outer catheter shaft. Typically, the balloon is welded or otherwise mechanically attached to the outer catheter shaft by placing the proximal balloon neck on the outside of the catheter shaft. By placing the balloon neck on the outside of the catheter shaft, the catheter presumably possesses a smoother profile for tracking the balloon to the treatment site since the “edge” created by the balloon to shaft joint is not pushed against the vessel wall while the balloon is being tracked through the patient&#39;s tortuous anatomy. 
     Another factor that affects the profile of the balloon catheter is the wall thickness of the balloon material. The profile of the deflated balloon is limited by the thickness of the neck and taper portions of the balloon. Usually, the neck and taper wall thicknesses of a torpedo-shaped angioplasty balloon are thicker than that of the body of the balloon due to the smaller diameter of the neck and taper portions. The thicker neck walls contribute to the overall thickness of the catheter, making tracking, crossing and re-crossing of lesions more difficult. Further, thick necks interfere with refolding of the balloon on deflation such that further inserting or withdrawing the deflated balloon may be difficult, occasionally even damaging the blood vessel. Reducing the wall thickness of the neck and taper portions reduces the overall profile of the deflated balloon. 
     Another factor which affects the profile of the balloon catheter is the balloon material itself. Angioplasty balloons are generally formed from relatively strong materials in order to withstand the pressures necessary for various procedures without failing. Typically, such characteristics require the use of a material that does not stretch appreciably. Use of polymeric materials that do not stretch appreciably consequently necessitates that the balloon is first formed by blow molding, and then the deflated balloon material, in the form of deflated wings, are folded around the catheter shaft prior to introduction of the balloon into the patient&#39;s body lumen. However, it may be desirable to employ balloons that do not have deflated folded wings, but which instead can be expanded to the working diameter within the patient&#39;s body lumen from an essentially wingless, cylindrical or tubular shape which conforms to the catheter shaft. 
     Thus, it is one aspect of the present invention to provide a balloon catheter with improved crossability and trackability, having a smooth reduced profile while simultaneously being sufficiently stiff to be tracked to the treatment site. 
     BRIEF SUMMARY OF THE INVENTION 
     Embodiments of the present invention relate to a catheter having an outer catheter shaft, an inner catheter shaft, and a balloon. The outer catheter shaft has a proximal portion, a distal portion, an inside surface, an outside surface, and an inflation lumen extending there through. The inner catheter shaft has a proximal portion, a distal portion, an inside surface, an outside surface, and a guidewire lumen extending there through, wherein at least a portion of the inner catheter shaft is disposed within at least the distal portion of the outer catheter shaft. The balloon has a proximal end, a distal end, an inside surface, an outside surface, and an interior which is in fluid communication with the inflation lumen, wherein the outside surface of the balloon at the proximal end of the balloon is attached to the inside surface of the outer catheter shaft at the distal portion of the outer catheter shaft. In one embodiment of the present invention, the balloon has a uniform wall thickness, a uniform inner diameter, and a uniform outer diameter along its full length in an unexpanded configuration. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The foregoing and other features and advantages of the invention will be apparent from the following description of the invention as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. The drawings are not to scale. 
         FIG. 1  is a side perspective view of a balloon delivery system with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the catheter of  FIG. 1  taken along line A-A of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of a catheter in accordance with another embodiment of the present invention taken along line A-A of  FIG. 1 . 
         FIG. 4  is an enlarged sectional view of the catheter of  FIG. 1  taken along line B-B of  FIG. 1 . 
         FIG. 5  is a side perspective view of a balloon delivery system in accordance with another embodiment of the present invention. 
         FIG. 6  is an enlarged sectional view of the balloon delivery system of  FIG. 5  along line C-C. 
         FIG. 7  is a cross-sectional view of the balloon of  FIG. 5 . 
         FIG. 8  is a side elevational view of tubing material for forming the balloon of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Specific embodiments of the present invention are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. The drawing in which an element first appears is typically indicated by the leftmost digit(s) in the corresponding reference number. The terms “distal” and “proximal” are used in the following description with respect to a position or direction relative to the treating clinician. “Distal” or “distally” are a position distant from or in a direction away from the clinician. “Proximal” and “proximally” are a position near or in a direction toward the clinician. 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. It is noted that the invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Although the description of the invention is in the context of treatment of blood vessels such as the coronary, carotid and renal arteries, the invention may also be used in any other body passageways where it is deemed useful. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     Embodiments of the present invention relate to a balloon catheter having an outer catheter shaft having a balloon mounted at the distal portion thereof. The profile of the balloon catheter is improved by placing the proximal balloon neck inside the outer catheter shaft. This outer shaft to balloon neck joint allows for a smaller outer diameter at the joint between the outer catheter shaft and the balloon, thus providing a reduced catheter profile in the joint transition area with improved crossability, trackability and stiffness. In one embodiment of the present invention, the balloon as bonded to the outer catheter shaft in an unexpanded configuration has uniform dimensions including wall thickness, inner diameter, and outer diameter along its full length. A balloon with such uniform dimensions provides for a more flexible balloon by eliminating the thicker neck and taper portions of the balloon. A balloon with such uniform dimensions is not folded prior to inflation, but is instead expanded to the working diameter from a generally cylindrical or tubular shape. This no-fold aspect of the balloon also reduces the profile of the balloon catheter, thus resulting in improved crossability and trackability. Another advantage associated with a balloon having uniform dimensions as described above is ease of manufacture. By eliminating the neck and taper regions from the balloon, the balloon may be formed from a simple mould design, which can be longer than the balloon length required, thus allowing multiple balloons be cut to length from balloons formed from the overlength mould. Further explanation and details will now be described with reference to  FIGS. 1-8 . 
     Referring now to  FIGS. 1-4 , an embodiment of a balloon catheter  100  according to the present invention is shown. Balloon catheter  100  includes a proximal portion  102 , a distal portion  104 , and an inflatable balloon  108  located at distal portion  104 . Catheter  100  may be used for angioplasty procedures, stent delivery, and/or localized drug delivery. 
     Catheter  100  includes an outer catheter shaft  106  which includes at least one continuous lumen  214  extending from at or near its proximal end  110  to at or near its distal end  112  in order to provide for balloon inflation. Balloon  108  is located at or near distal end  112  of shaft  106 , and a hub  116  is located at or near proximal end  110  of shaft  106 . Hub  116  includes a balloon inflation port  118  to allow fluid communication between inflation lumen  214  and balloon  108  so that the balloon  108  may be inflated. Hub  116  will serve in a conventional manner to provide a luer or other fitting in order to connect the catheter  100  to a source of balloon inflation, such as conventional angioplasty activation device. 
     Balloon  108  includes a proximal neck end  120  and a distal neck end  122 . At joint transition area  124 , proximal neck end  120  of balloon  108  is placed inside and joined to the distal end  112  of outer catheter shaft  106 , as shown in  FIG. 4 . Balloon  108  may be joined to outer catheter shaft  106  in any conventional manner, such as laser welding, adhesives, heat fusing, ultrasonic welding, or any other mechanical method. The profile of balloon catheter  100  is reduced by placing the proximal neck end  120  of balloon  108  inside outer catheter shaft  106  because such a configuration allows for a smaller outer diameter at joint transition area  124 . 
       FIG. 4  is an enlarged sectional view at the location along line B-B of  FIG. 1 , and illustrates joint transition area  124  of catheter  100 . As previously mentioned, typically an angioplasty balloon is welded or otherwise mechanically attached to the outer catheter shaft by placing the proximal balloon neck on the outside of the catheter shaft. By placing the proximal balloon neck on the outside of the catheter shaft, the catheter presumably possessed a smoother profile for tracking the balloon to the treatment site since the “edge” created by the balloon to shaft joint was not pushed against the vessel wall while the balloon was being tracked through the patient&#39;s tortuous anatomy. However, it is found that the edge  426  created by proximal neck end  120  of balloon  108  being placed inside the outer catheter shaft  106  did not hinder the crossability and trackability of catheter  100  while balloon  108  was being tracked through the patient&#39;s tortuous anatomy. Rather, having the proximal neck end  120  of balloon  108  placed inside the outer catheter shaft allows for a smaller outer diameter at joint transition area  124  and thus provides a reduced catheter profile with improved crossability, trackability and stiffness. 
     In addition, edge  426  may be modified in order to create a tapered edge  427 . Tapered edge  427  is illustrated as a dotted line in  FIG. 4 . Tapered edge  427  creates a smoother joint transition area  124  to ensure that the distal edge of the catheter shaft is not pushed against the vessel wall while being tracked through the patient&#39;s tortuous anatomy. Edge  426  may also be rounded or otherwise modified such as by a necking or thinning operation to create a smoother joint transition area  124 . 
     Referring now to  FIG. 2 ,  FIG. 2  is a cross-sectional view of a portion of balloon catheter  100  taken along line A-A of  FIG. 1 , and illustrates a coaxial dual lumen arrangement. In this embodiment, an inner or guidewire shaft  128  is disposed coaxially within outer catheter shaft  106 . Inner shaft  128  includes at least one continuous lumen  230  extending from at or near its proximal end  134  to at or near its distal end  136  in order to track catheter  100  over a guidewire  132 . As illustrated in  FIG. 1 , inner shaft  128  may extend the entire length of catheter  100 , with a proximal guidewire port  138  provided in hub  116  and a distal guidewire port  140  provided at the distal portion  104  of catheter  100 . 
     In the coaxial dual lumen arrangement illustrated in  FIG. 2 , inflation lumen  214  is created by a space between the outer surface of inner shaft  128  and the inner surface of outer catheter shaft  106 . Lumen  214  is in fluid communication with an interior of balloon  108  such that balloon  108  may be inflated.  FIG. 2  shows a guidewire  132  within guidewire lumen  230 . 
     Other embodiments of balloon catheter  100  may have guidewire lumen  230  and inflation lumen  214  in other dual lumen arrangements, such as a circular guidewire lumen above a D-shaped inflation lumen or a circular guidewire lumen set above a crescent-shaped inflation lumen. For example, an alternative non-coaxial dual lumen arrangement is illustrated in  FIG. 3 . In this embodiment, inner shaft  128  may be disposed within outer catheter shaft  106  in a non-coaxial relationship. This alternate configuration results in a guidewire lumen  330  and an inflation lumen  314  being in a side-by-side arrangement through the length of the catheter. Guidewire  132  is shown within lumen  330  of inner shaft  128 . 
     As previously described, the embodiments illustrated in  FIGS. 1-3  include inner shaft  128  disposed within outer catheter shaft  106 , with inner shaft  128  extending the entire length of catheter  100 . Such a configuration is typically referred to as an over-the-wire (OTW) catheter. An OTW catheter&#39;s guidewire shaft runs the entire length of the catheter and is attached to, or enveloped within, an inflation shaft. Thus, the entire length of an OTW catheter is tracked over a guidewire during a PTCA procedure. 
     One skilled in the art can appreciate how the balloon to catheter joint of the present invention, described in detail above, may also be incorporated in a rapid exchange (RX) catheter. A RX catheter has a guidewire shaft that extends within only the distalmost portion of the catheter. Thus, during a PTCA procedure only the distalmost portion of a RX catheter is tracked over a guidewire. 
     Outer catheter shaft  106  may be formed of any appropriate polymeric material. In addition, inner shaft  128  may be made of any appropriate polymeric material. Non-exhaustive examples of material for outer catheter shaft  106  and inner shaft  128  include polyethylene, PEBAX, nylon or combinations of any of these, either blended or co-extruded. Preferred materials for shafts  106  and  128  are polyethylene, nylon, PEBAX, or co-extrusions of any of these materials. 
     Optionally, shafts  106  and  128  or some portion thereof may be formed as a composite having a reinforcement material incorporated within a polymeric body in order to enhance strength, flexibility, and/or toughness. Suitable reinforcement layers include braiding, wire mesh layers, embedded axial wires, embedded helical or circumferential wires, and the like. For example, at least a proximal portion of outer catheter shaft  106  may in some instances be formed from a reinforced polymeric tube. As a further alternative, at least a proximal portion of outer catheter shaft  106  may in some instances be formed from a metal, highly elastic, or super elastic hypotube material. 
     Balloon  108  can be any appropriate shape or size, and any material which is relatively elastic and deformable. Non-exhaustive examples for balloon  108  include polymers such as polyethylene, PEBAX, PET, nylon, polyurethane. 
     Now referring to  FIGS. 5-7 , another aspect of the present invention relates to a catheter  500  including a balloon  508  bonded to an outer catheter shaft  506 .  FIG. 5  illustrates balloon catheter  500  having a proximal portion  502  and a distal portion  504  with inflatable balloon  508  located at distal portion  504 . As best shown in  FIG. 6 , balloon  508  has a length  652 . In addition to forming the basis for balloon angioplasty procedures, catheter  500  may form the basis of a stent delivery system and/or a drug delivery system. 
       FIG. 7  is a cross-sectional view of the balloon of  FIG. 5 , and illustrates that balloon  508  has a wall thickness  758 , an inner diameter  754 , and an outer diameter  756 . In an unexpanded configuration, wall thickness  758 , inner diameter  754 , and outer diameter  756  are uniform along the full length  652  of balloon  508 . A balloon with such uniform dimensions provides for a more flexible balloon by eliminating the thicker neck and taper portions of the balloon. In addition, a balloon with such uniform dimensions is not folded prior to inflation, but is instead expanded to the working diameter from a generally cylindrical or tubular shape. This no-fold aspect of balloon  508  also reduces the profile of catheter  500 , thus resulting in improved crossability and trackability. 
     Preferably, length  652  of balloon  508  is about 0.5 cm to about 4 cm and typically about 2 cm. When bonded to outer catheter shaft  506  in an unexpanded configuration, outer diameter  756  of balloon  508  is generally approximately 0.6 mm to about 0.9 mm along the full length  652  of balloon  508 . Wall thickness  758  of balloon  508  is generally approximately 0.035 mm to about 0.05 mm, and inner diameter  754  is thus generally approximately 0.53 mm to about 0.8 mm. When inflated, balloon  508  assumes a torpedo shape having an inflated working outer diameter of about 1 mm to about 5 mm, typically about 3 mm, in order to enlarge the lumen of the affected coronary artery. 
     Catheter  500  includes outer catheter shaft  506  which includes at least one continuous lumen  614  extending from at or near its proximal end  510  to at or near its distal end  512  in order to provide for balloon inflation. Balloon  508  is located at or near distal end  512  of shaft  506 , and a hub  516  is located at or near proximal end  510  of shaft  506 . Hub  516  includes a balloon inflation port  518  to allow fluid communication between inflation lumen  614  and balloon  508  so that the balloon  508  may be inflated. Hub  516  will serve in a conventional manner to provide a luer or other fitting in order to connect the catheter  500  to a source of balloon inflation, such as conventional angioplasty activation device. 
       FIG. 6  is an enlarged sectional view at the location along line C-C of  FIG. 5 , and illustrates joint transition area  524  of catheter  500 . Balloon  508  includes a proximal end  520  and a distal end  522 . At joint transition area  524 , proximal end  520  of balloon  508  is placed inside and joined to the distal end  512  of outer catheter shaft  506 . Balloon  508  may be joined to outer catheter shaft  506  in any conventional manner, such as laser welding, adhesives, heat fusing, ultrasonic welding, or any other mechanical method. The profile of balloon catheter  500  is reduced by placing the proximal end  520  of balloon  508  inside outer catheter shaft  506  because such a configuration allows for a smaller outer diameter at joint transition area  524 . Transition area  524  in  FIG. 6  may also be rounded or otherwise modified such as by a necking or thinning operation to create a smoother transition joint. 
     Similar to the embodiment described above with respect to  FIG. 2 , catheter  500  includes an inner or guidewire shaft  528  disposed coaxially within outer catheter shaft  506 . Inner shaft  528  includes at least one continuous lumen  630  extending from at or near its proximal end  534  to at or near its distal end  536  in order to provide a guidewire  532 . As illustrated in  FIG. 5 , inner shaft  528  may extend the entire length of catheter  500 , with a proximal guidewire port  538  provided in hub  516  and a distal guidewire port  540  provided at the distal portion of catheter  500 . The distal end  522  of balloon  508  is joined to the inner shaft  528  at joint  650 . Balloon  508  may be joined to inner shaft  528  in any conventional manner, such as laser welding, adhesives, heat fusing, ultrasonic welding, or any other mechanical method. 
     Inner shaft  528  and outer catheter shaft  506  may be arranged in various dual lumen configurations. Similar to the embodiment described above with respect to  FIG. 2 , inner shaft  528  and outer catheter shaft  506  may be arranged in a coaxial dual lumen configuration. In the coaxial dual lumen configuration, inflation lumen  614  is created by a space between the outer surface of inner shaft  528  and the inner surface of outer catheter shaft  506 . Lumen  614  is in fluid communication with an interior of balloon  508  such that balloon  508  may be inflated. 
     Other embodiments of balloon catheter  500  may have guidewire lumen  630  and inflation lumen  614  in other dual lumen arrangements, such as a circular guidewire lumen above a D-shaped inflation lumen or a circular guidewire lumen set above a crescent-shaped inflation lumen. For example, similar to the configuration illustrated in  FIG. 3 , inner shaft  528  may be disposed within outer catheter shaft  506  in a non-coaxial relationship. This configuration results in a guidewire lumen  630  and an inflation lumen  614  being in a side-by-side arrangement through the length of the catheter. 
     As previously described, the embodiments illustrated in  FIGS. 5-6  include inner shaft  528  disposed within outer catheter shaft  506 , with inner shaft  528  extending the entire length of catheter  500 . Such a configuration is typically referred to as an over-the-wire (OTW) catheter. An OTW catheter&#39;s guidewire shaft runs the entire length of the catheter and is attached to, or enveloped within, an inflation shaft. Thus, the entire length of an OTW catheter is tracked over a guidewire during a PTCA procedure. 
     One skilled in the art can appreciate how the balloon to catheter joint of the present invention, described in detail above, may also be incorporated in a rapid exchange (RX) catheter. A RX catheter has a guidewire shaft that extends within only the distalmost portion of the catheter. Thus, during a PTCA procedure only the distalmost portion of a RX catheter is tracked over a guidewire. 
     Outer catheter shaft  506  may be formed of any appropriate polymeric material. In addition, inner shaft  528  may be made of any appropriate polymeric material. Non-exhaustive examples of material for outer catheter shaft  506  and inner shaft  528  include polyethylene, PEBAX, nylon or combinations of any of these, either blended or co-extruded. Preferred materials for shafts  506  and  528  are polyethylene, nylon, PEBAX, or co-extrusions of any of these materials. 
     Optionally, shafts  506  and  528  or some portion thereof may be formed as a composite having a reinforcement material incorporated within a polymeric body in order to enhance strength, flexibility, and/or toughness. Suitable reinforcement layers include braiding, wire mesh layers, embedded axial wires, embedded helical or circumferential wires, and the like. For example, at least a proximal portion of outer catheter shaft  506  may in some instances be formed from a reinforced polymeric tube. As a further alternative, at least a proximal portion of outer catheter shaft  506  may in some instances be formed from a metal, highly elastic, or super elastic hypotube material. 
     As previously described, balloon  508  with such uniform dimensions as described above is not folded prior to inflation, but is instead expanded to the working diameter from a generally cylindrical or tubular shape. This no-fold aspect of balloon  508  reduces the profile of catheter  500  during insertion, thus resulting in improved crossability and trackability. Once balloon  508  is inflated, balloon  508  assumes a torpedo shape having a working outer diameter of approximately  3  mm in order to enlarge the lumen of the affected coronary artery. Upon deflation, shrinkage of the working outer diameter of the balloon occurs such that balloon  508  may be folded around catheter  500  and catheter  500  may be retracted from the patient. 
     The process of molding balloons for balloon catheters is generally known in the art. The process generally begins by placing an extruded tubular parison made of a drawable polymer having a specified diameter and wall thickness into the cavity of a mold. The balloon is then heated to a temperature in the range from the second-order transition temperature to the first-order transition temperature of the polymer used. Although the heating temperature will depend on the material, a temperature in the range of about 220-285° F. will generally suffice. While heated, the balloon is pressurized so that it will radially expand. A pressure in the range of about 300-450 psi is generally sufficient. The tubular product may also be axially elongated by stretching before, during, or after being radially expanded. Longitudinally stretching the material at a controlled velocity and distance thins out the material thickness in the balloon to the point where it will radially expand at the temperature and pressure in the balloon. The material of the balloon is thus biaxially oriented. A second process step is often used in balloon forming whereby the balloon inside the mould is exposed to a normalising or stress relieving step. This is usually achieved by applying a specific heat and pressure to the balloon for a fixed time period. Frequently the temperatures and pressures chosen for this process step are different to the heats and pressures used in the initial forming steps described above. This process step is often called a post-heat stage and its purpose is to impart uniformity to the balloons properties and to stabilise the balloon during storage and in further processing. Finally, the balloon is cooled in the mold to a temperature below the second-order transition temperature of the polymer. The completed balloon may then be removed from the mold. 
     In order to form balloon  508  having no-fold characteristics, the pressure is turned off during the post-heat stage (that is, after the balloon material is stretched both radially and longitudinally) in the balloon forming process to allow the balloon to shrink radially. In the post-heat stage of the manufacturing process, the balloon is in its stressed configuration. By turning off the pressure during this stage, the balloon in its stressed configuration is allowed to shrink radially to obtain an appropriate wingless unexpanded outer diameter. 
     By eliminating the importance of the neck and taper regions, a simpler mould design can be used to form balloon  508  since the taper and cone regions of the mould do not have to be tightly controlled as is the case with moulds for standard balloon designs. Balloon  508  is preferably formed from cut to length tubing. More specifically,  FIG. 8  illustrates tubing  860  having a length  862 . Tubing  860  Length  862  of tubing  800  is of such an amount that several balloons  508  may be formed from tubing  800 . In other words, balloons  508  may be cut to length post-processing, thus allowing several balloons to be made in one manufacturing cycle. 
     In the alternative, balloon  508  may be formed by removing or cutting off the neck and taper regions of a torpedo-shaped balloon. In this method of manufacture, balloon  508  may be formed by heat-shrinking a blow-molded torpedo-shaped balloon to shrink the balloon to an appropriate wingless unexpanded outer diameter. Thereafter, the neck and taper regions may be cut off or otherwise removed to form balloon  508  having a uniform wall thickness, a uniform inner diameter, and a uniform outer diameter along its entire length. 
     Balloon  508  can be formed from any appropriate material which is relatively elastic and deformable. Non-exhaustive examples for balloon  108  include polymers such as polyethylene, PEBAX, PET, nylon, polyurethane, and polyamide. The preferred material for obtaining the no-fold aspect of balloon  508  is elastic, such as polyurethane. 
     Other advantages associated with balloon  508  having uniform dimensions as described above are ease of manufacture. The manufacturing process is simplified because balloon  508  eliminates the importance of the neck and taper regions during balloon forming. 
     While various embodiments according to the present invention have been described above, it should be understood that they have been presented by way of illustration and example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the appended claims and their equivalents. It will also be understood that each feature of each embodiment discussed herein, and of each reference cited herein, can be used in combination with the features of any other embodiment. All patents and publications discussed herein are incorporated by reference herein in their entirety.