Multilayer balloons

An example medical device includes a balloon that is inflatable to an inflated configuration. The balloon includes a non-compliant layer coextruded on an inner layer, and an outer layer coextruded on the non-compliant layer. The non-compliant layer is configured to delaminate from the inner and the outer layers in the inflated configuration. The non-compliant layer may be configured to rupture in the inflated configuration. An example technique includes inflating the balloon to a predetermined pressure sufficient to rupture the non-compliant layer and insufficient to rupture both the inner and outer layers. The example technique further includes deflating the balloon, and introducing the balloon into a vasculature. Another example technique includes coextruding a non-compliant layer on an inner layer, coextruding an outer layer on the non-compliant layer, and forming a balloon from the inner layer, the non-compliant layer, and the outer layer.

TECHNICAL FIELD

This disclosure relates to medical devices including balloons.

BACKGROUND

Catheters may be used in intravascular procedures or other procedures to facilitate minimally invasive access to a target site. For example, an angioplasty catheter may include balloons mounted to the catheter that may be advanced to the target site and inflated to clear or compress a blockage, for example a stenosis. As another example, a stent delivery catheter may include a stent positioned over a balloon, which may be inflated to deploy the stent.

SUMMARY

Example medical devices include multilayer balloons are described herein. In some examples, a multilayer balloon includes nested balloons, and may have a higher burst pressure than a single layer or single wall balloon having a wall thickness equivalent to the combined wall thickness of the multilayer balloon. Arranging, nesting, and inflating balloons to form multilayer balloons with uniform inflation characteristics may be relatively difficult or inefficient. Some example techniques according to the disclosure allow manufacturing a multilayer balloon from a single extrusion.

Clause 1: In some examples, a medical device includes a balloon inflatable to an inflated configuration. The balloon includes a non-compliant layer coextruded on an inner layer, and an outer layer coextruded on the non-compliant layer. The non-compliant layer is configured to delaminate from the inner and the outer layers in the inflated configuration.

Clause 2: In some examples of the medical device of clause 1, the non-compliant layer is configured to delaminate from the inner layer before delaminating from the outer layer.

Clause 3: In some examples of the medical device of clause 1, the non-compliant layer is configured to delaminate from the outer layer before delaminating from the inner layer.

Clause 4: In some examples of the medical device of any of clauses 1 to 3, the inner layer and the outer layers are more flexible than the non-compliant layer.

Clause 5: In some examples of the medical device of any of clauses 1 to 4, the non-compliant layer is configured to rupture in the inflated configuration at a predetermined pressure, wherein the predetermined pressure is insufficient to rupture both the inner and the outer layers.

Clause 6: In some examples of the medical device of clause 5, the non-compliant layer is configured to rupture after delamination of the non-compliant layer from the inner and outer layers.

Clause 7: In some examples of the medical device of clause 5, the non-compliant layer is configured to fragment in the inflated configuration at the predetermined pressure.

Clause 8: In some examples of the medical device of clause 7, an inner surface defined by the outer layer is configured to contact an outer surface defined by the inner layer in the inflated configuration.

Clause 9: In some examples of the medical device of clause 8, the inner layer defines an inner balloon and the outer layer defines an outer balloon, the inner balloon being nested in the outer balloon.

Clause 10: In some examples of the medical device of clause 9, the inner balloon is fluidically isolated from the outer balloon.

Clause 11: In some examples of the medical device of any of clauses 1 to 10, the non-compliant layer has a greater stiffness than each of the inner layer and the outer layer.

Clause 12: In some examples of the medical device of any of clauses 1 to 11, the non-compliant layer includes a thermoplastic.

Clause 13: In some examples of the medical device of clause 12, the thermoplastic includes a high-density polyethylene (HDPE).

Clause 14: In some examples of the medical device of any of clauses 1 to 13, one or both of the inner layer and the outer layer includes a thermoplastic elastomer.

Clause 15: In some examples of the medical device of clause 14, the thermoplastic elastomer includes a polyether block amide (PEBA).

Clause 16: In some examples of the medical device of any of clauses 1 to 15, the non-compliant layer is coextensive with one or both of the inner layer and the outer layer.

Clause 17: In some examples of the medical device of any of clauses 1 to 16, the non-compliant layer defines at least one of a discontinuity, a perforation, a window, or an opening in the inflated configuration.

Clause 18: In some examples, a system includes the medical device of any of clauses 1 to 17 and a second medical device secured to the balloon.

Clause 19: In some examples of the system of clause 18, the second medical device includes a stent crimped to the balloon.

Clause 20: In some examples, a system includes the medical device of any of clauses 1 to 17, and further includes an elongated member. The balloon is mounted to the elongated member. The elongated member includes a catheter body.

Clause 21: In some examples, a medical device includes a balloon inflatable to an inflated configuration. The balloon includes a non-compliant layer coextruded on an inner layer, and an outer layer coextruded on the non-compliant layer. The non-compliant layer is configured to rupture in the inflated configuration at a predetermined pressure. The predetermined pressure is insufficient to rupture both the inner and the outer layers.

Clause 22: In some examples of the medical device of clause 21, the non-compliant layer is configured to delaminate from the inner and the outer layers before the rupture.

Clause 23: In some examples of the medical device of clause 21 or clause 22, the non-compliant layer has a greater stiffness than each of the inner layer and the outer layer.

Clause 24: In some examples of the medical device of any of clauses 21 to 23, the balloon is in the inflated configuration at the predetermined pressure, and the non-compliant layer is ruptured such that the non-compliant layer defines a plurality of perforations.

Clause 25: In some examples of the medical device of any of clauses 21 to 23, the balloon is in the inflated configuration at the predetermined pressure, and the non-compliant is substantially disintegrated such that an inner surface defined by the outer layer substantially uniformly contacts an outer surface defined by the inner layer.

Clause 26: In some examples of the medical device of any of clauses 21 to 23, the non-compliant layer defines at least one of a discontinuity, a perforation, a window, or an opening in the inflated configuration.

Clause 27: In some examples, a method includes inflating a balloon to a predetermined pressure. The balloon includes a non-compliant layer coextruded on an inner layer and an outer layer coextruded on the non-compliant layer. The predetermined pressure is sufficient to rupture the non-compliant layer and insufficient to rupture both the inner and the outer layers. The method includes deflating the balloon, and introducing the balloon into vasculature of a patient.

Clause 28: In some examples of the method of clause 27, inflating the balloon at the predetermined pressure includes causing only the non-compliant layer to rupture to cause an inner surface defined by the outer layer to contact an outer surface defined by the inner layer.

Clause 29: In some examples of the method of clause 27, inflating the balloon at the predetermined pressure includes causing only the non-compliant layer to rupture to cause the non-compliant layer to define at least one of a discontinuity, a perforation, a window, or an opening in the inflated configuration.

Clause 30: In some examples, the method of any of clauses 27 to 29 further includes, after introducing the balloon into the vasculature, pressurizing the balloon to an operational pressure.

Clause 31: In some examples, a method includes inflating a balloon to a predetermined pressure. The balloon includes a non-compliant layer coextruded on an inner layer and an outer layer coextruded on the non-compliant layer. The predetermined pressure is sufficient to delaminate the non-compliant layer from the inner and the outer layers. The method includes deflating the balloon, and introducing the balloon into vasculature of a patient.

Clause 32: In some examples, the method of clause 31 further includes, after introducing the balloon into the vasculature, pressurizing the balloon to an operational pressure.

Clause 33: In some examples, a method includes coextruding a non-compliant layer on an inner layer, coextruding an outer layer on the non-compliant layer, and forming a balloon from the inner layer, the non-compliant layer, and the outer layer. The non-compliant layer is configured to delaminate from the inner and the outer layers in an inflated configuration of the balloon.

Clause 34: In some examples of the method of clause 33, co-extruding the non-compliant layer on the inner layer and coextruding the outer layer on the non-compliant layer includes coextruding a tubing including the inner layer, the non-compliant layer, and the outer layer.

Clause 35: In some examples of the method of clause 33 or clause 34, the forming the balloon includes molding the inner layer, the non-compliant layer, and the outer layer over a scaffold.

Clause 36: In some examples, the method of any of clauses 33 to 35 further includes heat-setting the balloon.

Clause 37: In some examples, the method of any of clauses 33 to 36 further includes inflating the balloon to a predetermined pressure sufficient to rupture the non-compliant layer, the predetermined pressure is insufficient to rupture both the inner and the outer layers.

Clause 38: In some examples, the method of clause 37 further includes allowing only the non-compliant layer to fragment at the predetermined pressure to cause an inner surface defined by the outer layer to contact an outer surface defined by the inner layer.

Clause 39: In some examples, the method of any of clauses 33 to 38 further includes securing a second medical device to the balloon.

Clause 40: In some examples, the method of clause 39 includes securing the second medical device to the balloon includes crimping a stent to the balloon.

Clause 41: In some examples, the method of any of clauses 33 to 40 further includes mounting the balloon to an elongated member.

Clause 42: In some examples, a method includes coextruding a non-compliant layer on an inner layer, coextruding an outer layer on the non-compliant layer, and forming a balloon from the inner layer, the non-compliant layer, and the outer layer. Only the non-compliant layer is configured to rupture in an inflated configuration of the balloon at a predetermined pressure.

Clause 43: In some examples of the method of clause 42, co-extruding the non-compliant layer on the inner layer and coextruding the outer layer on the non-compliant layer includes coextruding a tubing including the inner layer, the non-compliant layer, and the outer layer.

Clause 44: In some examples of the method of clause 42 or clause 43, the forming the balloon includes molding the inner layer, the non-compliant layer, and the outer layer over a scaffold.

Clause 45: In some examples, the method of any of clauses 42 to 44 further includes heat-setting the balloon.

Clause 46: In some examples, the method of any of clauses 42 to 45 further includes inflating the balloon to the predetermined pressure to delaminate the non-compliant layer from the inner and the outer layers.

Clause 47: In some examples, the method of any of clauses 42 to 46 further includes securing a second medical device to the balloon.

Clause 48: In some examples of the method of clause 47, securing the second medical device to the balloon includes crimping a stent to the balloon.

Clause 49: In some examples, the method of any of clauses 42 to 48 further includes mounting the balloon to an elongated member.

DETAILED DESCRIPTION

In examples described herein, a multilayer balloon configured to expand from a deflated configuration to an inflated configuration includes at least three layers. An example multilayer balloon may be prepared by coextrusion, for example, a trilayer extrusion. The inner and outer layers of the multilayer balloon may include materials having the same composition or having different compositions. The middle layer may include a material that has poor adhesion properties to the inner and outer layers, thus causing delamination of the middle layer from the inner and outer layers and the separation of the inner and outer layers from each other. The delamination could be activated during the extrusion of the multilayer balloon, for example, when the extrusion is under a relatively high stress, or after the extrusion.

In some examples, the middle layer may be a relatively non-compliant layer that exhibits perforation or partial or complete rupture during inflation, so that the inner and outer layer may contact each other at one or more regions, or substantially contact across a major area of the inner layer, the outer layer, or the balloon following rupture or disintegration of the middle layer. A relatively compliant layer (also called a compliant layer herein) is a layer including a material that inflates, deflates or deforms without resulting in mechanical failure of the material. A relatively non-compliant layer (also called a non-compliant layer herein) is a layer including a material that resists inflation or deformation (relative to a compliant layer), for example, resulting in mechanical failure of the material in response to inflation or deformation beyond a predetermined threshold.

One or both of the delamination and the rupture of the middle layer may result in a multilayer balloon that includes inner and outer layers capable of independent movement, similar to the behavior of multilayer balloons formed by nesting structurally distinct balloons. However, one of the drawbacks to nesting multiple balloons may be that traditional nesting balloons require additional manufacturing steps such as aligning respective nested balloons to form the nested structure. The nesting step may also result in the introduction of air or fluid pockets between adjacent balloon surfaces, needing additional manufacturing steps for removal of fluid pockets to provide uniform inflation of the balloon. Example techniques and multilayer balloons according to the disclosure may provide a nested balloon configuration obtained from a single coextrusion, without requiring a nesting step for nesting separate balloons. Coextruding a single construction that results in a nested balloon configuration may thus be easier to manufacture compared to nesting individual balloons into a nested configuration. Thus, example techniques according to the disclosure may be used to prepare multilayer balloons including nested inner and outer layers.

FIG. 1is a schematic and conceptual side view of an example medical device10including an elongated member12and a balloon14mounted closer to a distal tip16of elongated member12than a proximal end of elongate member12. A hub18connected to the proximal end of elongated member12may allow elongated member12to be manipulated, advanced, or retracted, and may provide ports for communicating with lumens defined by elongated member12. For example, hub18may include an inflation arm20that may be connected to a source of inflating fluid to deliver inflating fluid through an inflation lumen port22to inflate balloon14, or deflate balloon14by withdrawing the inflating fluid. In some examples, hub18may include an adapter24to receive a guidewire through a guidewire lumen in elongated member12(not shown). In some examples, elongated member12may include a catheter body, for example, a balloon catheter, and hub18may include a catheter hub. In some examples, instead of a guidewire catheter, medical device10may include a rapid-exchange balloon catheter system.

Elongated member12may be advanced to a target site, for example, through a body lumen such as a blood vessel of a patient. In some examples, distal tip16may be introduced into the vasculature of the patient through an incision or opening, followed by a shaft of elongated member12. Elongated member12may be advanced through the body lumen, for example, over a guidewire introduced through adapter24of hub18. Balloon14may be maintained in an uninflated or partly inflated configuration while advancing elongated member12through the vasculature. When elongated member12is sufficiently advanced, for example, such that balloon14is adjacent the target site, inflating fluid may be delivered through inflation lumen port22to inflate balloon14to an inflated configuration at the target site. Balloon14is illustrated in an inflated configuration inFIG. 1. In some examples, inflation of balloon14may result in expansion of the vasculature, or removal of blockage, for example, clots, debris, or fat at the target site. The inflating fluid may subsequently be withdrawn through inflation lumen port22to result in deflation of balloon14, and deflated balloon14may be withdrawn through the vasculature by retracting elongated member12.

In some examples, balloon14may include one or more radiopaque markers17. For example, radiopaque marker17may include one or more radiopaque bands disposed about balloon14, such as one marker17adjacent the proximal end of balloon14and another marker17adjacent a distal end of balloon14, as shown inFIG. 1. Radiopaque marker17may allow balloon14to be observed using suitable radioimaging techniques during a medical procedure, for example, while advancing or retracting balloon14with elongated member12.

In some examples, medical device10may include a second medical device26.FIG. 2is a schematic and conceptual partial side view of medical device10ofFIG. 1further including second medical device26positioned over (e.g., co-axial with) balloon14, and, in some examples, secured to balloon14. In some examples, as illustrated inFIG. 2, second medical device26may include a stent crimped to balloon14. Balloon14is illustrated in an uninflated configuration inFIG. 2, with the stent in an unexpanded configuration ready for deployment. In examples in which second medical device26is secured to balloon14, second medical device26may be advanced with balloon14to the target site, and the inflation of balloon14may trigger deployment of second medical device26. For example, in examples in which second medical device26includes a stent, inflation of balloon14may expand the stent to an expanded state to scaffold a region of the vasculature adjacent the stent. In examples in which second medical device26was secured to balloon14, after deploying second medical device26at a target site within the patient and subsequently partially or fully deflating balloon14, second medical device26may remain in a deployed configuration at the target site, and only balloon14can be withdrawn from the patient. In other examples, second medical device26may be withdrawn with balloon14after balloon14is partly or completely deflated.

Balloon14may be defined by a balloon wall15. Balloon wall15includes multiple layers, such that balloon14is a multilayer balloon. Balloon14and balloon wall15are further described with reference toFIGS. 3A-3D, which illustrate schematic and cross-sectional views of balloon14in different configurations, the cross-section being taken in a direction orthogonal to a longitudinal axis of elongated member12(FIG. 1).FIG. 3Ais a schematic and conceptual cross-sectional view of balloon14a, which is similar to balloon14ofFIG. 1, in a partly inflated configuration. Balloon wall15includes outer layer32and inner layer36. In some examples, outer layer32defines an outermost surface of balloon14a, while inner layer36defines an innermost surface of balloon14a. However, in some examples, balloon14amay include one or more additional layers. In addition, in some examples, one or more coatings or surface treatments may be applied to outer layer32, such as, but not limited to, a lubricious coating, a lubricious surface treatment or a therapeutic agent. Outer layer32and inner layer36may be formed of an inflatable material, for example, a polymer composition. In some examples, outer layer32and inner layer36may have the same composition. In some examples, outer layer32and inner layer36may have different compositions.

In some examples, balloon14aincludes at least one middle layer34disposed between outer layer32and inner layer36, as shown inFIG. 3A. In some examples, middle layer34is formed of a material configured to have relatively poor adhesion to or relatively easy delamination from one or both of outer layer32and inner layer36. In some examples, middle layer34may be coextensive with one or both of inner layer36and outer layer32. In some examples, middle layer34may define at least one of a discontinuity, a perforation, a window, or another such opening, such that outer layer32and inner layer36may contact each other directly through the opening. In some examples, the discontinuity, the perforation, the window, or the opening may form in middle layer34as a result of expansion or inflation of middle layer34. In some examples, middle layer34may define the discontinuity, the perforation, the window, or the opening before expansion or inflation. For example, middle layer34may be coextruded with one or both of inner layer36and outer layer32such that middle layer34defines the discontinuity, the perforation, the window, or the opening.

In some examples, middle layer34may include a material selected to have relatively poor adhesion to outer layer32and inner layer36. Poor adhesion may be evaluated using a polymer welding compatibility matrix as a guide. In some examples, pairs of materials that form bad welding joints, fail to form a welding joint, or otherwise poorly adhere to each other may be potential pair materials (“P”) as indicated by TABLE 1. One of a respective potential pair (for example, TPE and HDPE) may be selected for middle layer34and the other of the respective potential pair may be selected for one or both of outer layer32and inner layer36. For example, both outer layer32and inner layer36may include a TPE such as a PEBA, for example, PEBAX® 7033 or 7233, and middle layer34may include a thermoplastic, for example, an HDPE, so that middle layer34has poor adhesion with outer layer32and inner layer36.

While in the examples shown inFIGS. 3A-3D, balloons14a,14b,14c, and14dare illustrated having a circular cross-section, in some examples, balloons14,14b,14c, and14dmay have any suitable shape, configuration, or cross-section. In some examples, balloon14may have a geometrically similar shape in an uninflated and an inflated configuration. For example, balloon14may be cylindrical in both uninflated and inflated configurations. In some examples, balloon14may have different shapes in uninflated and inflated configurations. For example, balloon14may be folded or otherwise have a compact uninflated configuration.

While in the examples shown inFIGS. 3A-3D, balloons14a,14b,14c, and14dare illustrated as having two or three layers, in some examples, balloons14a,14b,14c, and14dmay have any number of additional layers, and the number of layers may change after one or more of delamination, perforation, rupture, or disintegration of balloon14or part of balloon14. In some examples, one or more tie layers may be provided between adjacent layers of balloon14. For example, a tie layer may include an adhesive to promote adhesion of adjacent layers. In some examples, one or more lubricant layers may be provided between adjacent layers of balloon14. For example, the lubricant layer may include a lubricant to reduce adhesion between adjacent layers. In some examples, the lubricant may include one or more of silicone, graphene, or a graphitic coating. Providing a lubricant layer may promote delamination by reducing a joining compatibility between layers adjacent the lubricant layer.

In some examples, middle layer34may include a non-compliant layer. A non-compliant layer may be a layer that has lower flexibility, lower softness, higher rigidity, or compliance to expansion or inflation compared to a compliant layer. A compliant layer, for example, a layer including a PEBA, may exhibit stretching in response to an inflationary pressure. In contrast, a non-compliant layer, for example, a layer including an HDPE, may exhibit reduced or relatively no stretching compared to a compliant layer. Whether a layer is compliant or non-compliant may depend on the composition, hardness, and dimensions, for example, thickness, of the layer. Compliance may be measured, for example, by measuring radial expansion of a layer as a ratio of inflation pressure. In some examples, a compliant layer may exhibit an expansion greater than about 10 millimeters/atmospheres (mm/atm), or greater than about 20 millimeters/atmospheres, or greater than about 50 millimeters/atmospheres. In some examples, a non-compliant layer may exhibit an expansion lower than about 0.02 mm/atm, or lower than about 0.01 mm/atm, or lower than about 0.001 mm/atm. A semi-compliant layer may exhibit an expansion greater than about 0.02 mm/atm and less than about 10 mm/atm. In some examples, middle layer34may include a semi-compliant layer.

In some examples, outer layer32may have a thickness between about 0.005 millimeters (mm) and about 0.10 mm, for example, for coronary balloon applications. The total thickness of balloon14may be higher for non-coronary balloon applications, for example, up to 1 mm. In some examples, middle layer34may have a thickness between about 0.001 mm and about 0.10 mm. In some examples, inner layer36may have a thickness between about 0.005 and about 0.10 mm. In some examples, one or more of outer layer32, middle layer34, or outer layer36may have a hardness between about 25 Shore D and about 75 Shore D.

The hardness of respective layers of balloon14may vary. For example, the hardness of respective layers may increase from an outermost layer to an innermost layer of balloon14. In some examples, the hardness of respective layers may decrease from an outermost layer to an innermost layer of balloon14. For example, outer layer32may be softer than middle layer34to facilitate printing of patterns, instructions, or text, or to facilitate securing or crimping of second medical device26to balloon14. In some examples, the hardness of a respective middle layer or layers may be higher than the hardness of respective inner and outer layer or layers. In some examples, an inner layer or layers may have substantially the same hardness as an outer layer or layers of balloon14. In some examples, outer layer32and inner layer36may each be more flexible than middle layer34. Thus, in examples in which middle layer34includes a non-compliant layer, the non-compliant layer may have a greater stiffness than each of inner layer36and outer layer32. Middle layer34may be softer, more flexible, or both softer and more flexible than outer layer32and inner layer36to provide a predetermined softness to balloon14.

In some examples, a compliance of a layer of balloon14may be reduced by adding components, for example, reinforcing material or fibers that resist stretching or inflation. For example, one or more of outer layer32, middle layer34, and inner layer36may include one or more reinforcing components, materials, or fibers. In some examples, the reinforcing components may include one or more of glass, metal, alloy, carbon, or polymers.

In some examples, middle layer34may be configured to delaminate from outer layer32and inner layer36in an inflated configuration of balloon14a, for example, a fully inflated configuration of balloon14a. In some examples, middle layer34may delaminate from outer layer32and inner layer36when balloon14ais inflated to a predetermined delamination pressure. For example, middle layer34may have relatively low welding or joining compatibility with one or both of outer layer32and inner layer36such that middle layer34may separate from one or both of outer layer32and inner layer36as balloon14ais inflated to the predetermined pressure to result in delamination. In some examples, the predetermined pressure may be between about 0.1 atmospheres (atm) and 45 atm. While inflating may result in delamination, in some examples, middle layer34may separate from one or both of outer layer32and inner layer36in an uninflated configuration of balloon14a(for example, without inflation or prior to inflation) to result in delamination.FIG. 3Bis a schematic and conceptual expanded view of the cross-sectional view of an example balloon14bsimilar to balloon14ashown inFIG. 3Ain an inflated delaminated configuration. In the delaminated configuration illustrated inFIG. 3B, a balloon wall15bof balloon14bincludes middle layer34delaminated from outer layer32and inner layer36. For example, delamination may be a state in which an inner surface32bof outer layer32is separated from an outer surface34aof middle layer34, and an outer surface36aof inner layer36is separated from an inner surface34bof middle layer34.

In some examples, inner surface32bof outer layer32and outer surface34aof middle layer34may define a first inter-layer void35a, and outer surface36aof inner layer36and inner surface34bof middle layer34may define a second inter-layer void35b. One or both of first and second inter-layer voids35aor35bmay exhibit a vacuum or a pressure lower than a pressure within an interior volume defined by inner layer36. In some examples, rupture or perforation of middle layer34may cause first and second inter-layer voids35aor35bto be fluidically connected. In some examples, debris or material originating from rupture or perforation of middle layer34may occupy one or both of first and second inter-layer voids35aor35b.

While the layers are illustrated as being physically separated with intermediate spacing in the example illustrated inFIG. 3B, in some examples, the layers may be substantially in contact (e.g., in contact along only some parts of the layers or along the entire adjacent surfaces) in the delaminated configuration. For example, the delamination may entail loss of adhesion between respective surfaces of respective layers, while still maintaining or being succeeded by contact between the respective surfaces of respective layers. In some examples, delamination of middle layer34from outer layer32and inner layer36may result from relatively poor weld, adhesion, or joining compatibility between pairs of respective materials of outer layer32and middle layer34, and inner layer36and middle layer34, as indicated by poor compatibility of potential pair materials in TABLE 1.

Outer layer32, middle layer34, and inner layer36may be capable of independent movement, for example, expansion or contraction, in the delaminated configuration. For example, one or both of outer layer32or inner layer36may be capable of independent movement relative to middle layer34, or one or both of middle layer34or inner layer36may be capable of independent movement relative to outer layer32, or even one or both of middle layer34or outer layer32may be capable of independent movement relative to inner layer36. Thus, in some examples of the delaminated configuration illustrated inFIG. 3B, balloon14bmay behave similar to a nested series of balloons formed from a first balloon including outer layer32, a second balloon including middle layer34, and a third balloon including inner layer36. For example, the first, second, and third balloons may be fluidically isolated from each other. A balloon wall of a predetermined thickness including fluidically isolated nested balloons may exhibit better puncture resistance and robustness compared to a balloon wall including a single layer or a laminated multilayer having the same thickness. For example, a puncture in an outer surface of a single layer or laminated multilayer balloon may propagate to an inner surface across the balloon wall, leading to balloon failure. In contrast, a puncture in an outermost balloon of a series of fluidically isolated nested balloons may not propagate to an innermost balloon, such that even if an outermost balloon is punctured, at least one unpunctured innermost layer will remain inflated.

In some examples, middle layer34includes the non-compliant layer. Balloon14amay thus include non-compliant middle layer34coextruded on inner layer36, and outer layer32coextruded on middle layer34. Non-compliant middle layer34may be configured to delaminate from outer layer32and inner layer36in an inflated configuration of balloon14a. In some examples, non-compliant middle layer34may be configured to delaminate from inner layer36before delaminating from outer layer32. For example, the joining compatibility of the pair of materials of non-compliant middle layer34and of inner layer36may be lower than the joining compatibility of the pair of materials of non-compliant middle layer34and outer layer32. In other examples, non-compliant middle layer34may be configured to delaminate from outer layer32before delaminating from inner layer36. For example, the joining compatibility of the pair of materials of non-compliant middle layer34and of outer layer32may be lower than the joining compatibility of the pair of materials of non-compliant middle layer34and inner layer36. Thus, middle layer34may promote delamination of one or more layers of balloon14. In some examples, balloon14may include additional layers that promote delamination. For example, balloon14may include more than one layer that promotes delamination, for example, non-compliant layers or lubricant layers, to further improve delamination of predetermined layers of balloon14.

In examples in which middle layer34includes a non-compliant layer, inflating balloon14abeyond a predetermined pressure may cause middle layer34to perforate, or partly or completely rupture, while outer layer32and inner layer36remain intact and act to maintain balloon14ain an inflated or inflatable state. For example,FIG. 3Cis a schematic and conceptual cross-sectional view of an example balloon14csimilar to balloon14aofFIG. 3Aincluding middle layer34in an inflated perforated configuration. In some examples, a balloon wall15cof balloon14cincludes middle layer34defining a plurality of perforations34c. In some examples, when balloon14aofFIG. 3Ais inflated to a predetermined pressure, middle layer34at least partly ruptures or perforates, forming balloon14cshown inFIG. 3C. While inner surface32bof outer layer32is shown spaced from outer surface36aof inner layer36, in some examples, inner surface32bof outer layer32may contact outer surface36aof inner layer36at least at regions defined by perforations34c, i.e., outer layer32and inner layer36may contact each other through the open spaces defined by perforations34c, for example, through first or second inter-layer voids35aor35b. In some examples, as shown inFIGS. 3B and 3C, first and second inter-layer voids35aand35bof balloon14bmay combine to form a combined inter-layer void35of balloon14cafter rupture or perforation of middle layer34, and perforations34cmay extend through combined inter-layer void35.

In examples in which middle layer34includes a non-compliant layer, the non-compliant layer is configured to rupture in the inflated configuration at a predetermined pressure. The predetermined pressure is insufficient to rupture both inner layer36and outer layer32, thereby maintaining balloon14ain an inflated or inflatable state. In some examples, the non-compliant layer may be configured to rupture after delamination of the non-compliant layer from inner layer36and outer layer32. In some examples, the non-compliant layer may be configured to fragment in the inflated configuration at the predetermined pressure.

In some examples, inflating balloon14ato the predetermined pressure sufficient to cause one or both of delamination and rupture may be performed as part of a technique for manufacturing balloon14a, as described with reference to some example techniques according to the disclosure, for example, techniques described with reference toFIGS. 4 and 5. In addition to, or instead of delaminating during the manufacturing stage, in some examples, inflating balloon14ato the predetermined pressure sufficient to cause one or both of delamination and rupture may be performed by a medical practitioner while using medical device10, as described with reference to some example techniques according to the disclosure, for example, techniques described with reference toFIGS. 4 and 5. In some examples, after inflating balloon14ato the predetermined pressure, balloon14amay be deflated to allow folding or otherwise compacting balloon14ato facilitate packaging and use.

In some examples, the perforations, rupture, or tears in middle layer34may cause middle layer34to substantially disintegrate in an inflated configuration of balloon14a, so that middle layer34no longer separates outer layer32and inner layer36. For example,FIG. 3Dis a schematic and conceptual cross-sectional view of an example balloon14dsimilar to balloon14aofFIG. 3Awith inner layer36directly contacting outer layer32. For example, a balloon wall15dof balloon14dmay include inner surface32bdefined by outer layer32substantially uniformly (e.g., uniformly or nearly uniformly) contacting outer surface36adefined by inner layer36in the inflated configuration of balloon14d. Outer layer32and inner layer36may be capable of independent movement, for example, expansion or contraction, in the inflated configuration shown inFIG. 3D. Thus, in the inflated configuration illustrated inFIG. 3D, balloon14dmay behave similar to a nested pair of balloons formed from a first balloon including outer layer32, and a second balloon including inner layer36. For example, inner layer36may define an inner balloon, and outer layer32may define an outer balloon, with the inner balloon being nested in the outer balloon. In some examples, the inner balloon may be fluidically isolated from the outer balloon. For example, a loss of pressure or increase in pressure in one of the inner or the outer balloons may not affect the pressure in the other of the inner or the outer balloons. If second medical device26, for example, a stent, punctures the outer balloon, at least an inner balloon may still remain pressurized, maintaining balloon14dinflated. Similarly, if the outer balloon punctures as a result of contact with a calcified lesion or another rigid structure within a body lumen, at least an inner balloon may still remain pressurized, maintaining balloon14dinflated.

Each of the delaminated configuration of balloon14dshown inFIG. 3Dand the inflated configurations of balloons14cand14drespectively shown inFIGS. 3C and 3Dmay exhibit higher burst or puncture resistance compared to a single layer balloon having the same respective effective wall thickness as respective balloon walls15b,15c, and15d. For example, a puncture in an outer surface of a single layer or laminated multilayer balloon may propagate to an inner surface across the balloon wall, leading to balloon failure. In contrast, the first, second, and third layers may form nested balloons that are fluidically isolated from each other, preventing a loss of pressure in an outermost balloon from resulting in a loss of pressure in an innermost balloon. A puncture in an outermost balloon of a series of fluidically isolated nested balloons may not propagate to an innermost balloon, such that even if an outermost balloon is punctured, at least one unpunctured innermost layer will remain inflated, maintaining the structural integrity and function of the balloon. Thus, example multilayer balloons according to the disclosure may be used in procedures where robustness and puncture-resistance of balloons is desired.

FIG. 4is a flowchart illustrating an example technique for using balloon14in a procedure. As discussed with reference toFIGS. 3A-3D, in some examples, balloons14a-14dmay include middle layer34including a non-compliant layer coextruded on inner layer36, and outer layer32coextruded on the non-compliant layer. While the example technique ofFIG. 4is described with reference to balloon14shown inFIG. 1, balloons14a-14dshown inFIGS. 3A-3Dmay be representative of different configurations of balloon14ofFIG. 1, for example, during performing the example technique ofFIG. 4. The example technique ofFIG. 4optionally includes inflating balloon14to the predetermined pressure sufficient to rupture the non-compliant layer, and insufficient to rupture both inner layer36and outer layer32(40). As discussed below, inflating balloon14to the predetermined pressure (40) may not be required if inflating balloon14to an operational pressure would result in rupture of the non-compliant layer or middle layer34without rupturing both inner layer36and outer layer32. For example, the operational pressure may be greater than or equal to the predetermined pressure, and inflating to the operational pressure may therefore result in rupture of the non-compliant layer, without requiring a separate inflating of balloon14to the predetermined pressure.

Inflating balloon14may include delivering inflating fluid to balloon14through inflation lumen port22causing balloon14to expand to an inflated ruptured configuration, for example, the configuration of balloon14cshown inFIG. 3C, in which middle layer34is at least partly perforated or ruptured, or the configuration of balloon14dshown inFIG. 3D, in which middle layer34is substantially ruptured or disintegrated. In some examples, inflating balloon14to the predetermined pressure (40) may result in delamination of one or both of outer layer32from middle layer34or of middle layer34from inner layer36. For example, outer layer32may delaminate from middle layer34, or middle layer34may delaminate from inner layer36, during the inflating, as shown inFIG. 3B(40). In some examples, at least partial delamination may occur before the rupture of middle layer34. For example, at least a portion of one of outer layer32, middle layer34, and inner layer36may separate from a portion of another of outer layer32, middle layer34, and inner layer36, before the rupture of any portion of middle layer34. In some examples, complete delamination may occur before the rupture of middle layer34. For example, outer layer32may completely delaminate from middle layer34, and middle layer34may completely delaminate from inner layer36, before the rupture of any portion of middle layer34. In other examples, delamination may be at least partly concurrent in time with rupture during the inflating (40). For example, at least a portion of one of outer layer32, middle layer34, and inner layer36may separate from a portion of another of outer layer32, middle layer34, and inner layer36during rupture of a portion of middle layer34.

In some examples, inflating balloon14to the predetermined pressure (40) may be performed before initiating a medical procedure, for example, after removing balloon14from a medical package, or while balloon14is in the medical package. In addition, or instead, inflating balloon14to the predetermined pressure (40) may be performed during manufacture of balloon14, for example, during or after coextruding outer layer32, middle layer34, and inner layer36so that balloon14is in a configuration similar to that of balloon14cor balloon14din the medical package.

In some examples, the technique ofFIG. 4includes introducing balloon14into vasculature of a patient (42). For example, distal tip16of elongated member12may be introduced at an incision or body opening and into the vasculature, followed by the shaft of elongated member12carrying balloon14. In some examples, introducing balloon14into the vasculature (42) may include advancing balloon14carried on elongated member12over a guidewire or other guide member through the vasculature to a target site within the vasculature. In examples in which balloon14includes radiopaque marker17, a clinician may use radiopaque marker17to visualize the position of balloon14arelative to the target site within the vasculature, for example, by radioimaging. In another example, inflating balloon14to the predetermined pressure (40) may be performed after introducing balloon14into the vasculature (42).

After balloon14arrives at the target site, balloon14may be inflated, such as by pressurizing the balloon to an operational pressure (44). The operational pressure may be a pressure sufficient to expand balloon14to an operational dimension, for example, an operational diameter. For example, the operational diameter may be an average diameter of balloon14in an inflated configuration that is sufficient to expand, clear, or scaffold a region of the vasculature adjacent the target site. In some examples, the operational diameter may be a diameter sufficient to deploy second medical device26at the target size, for example, by causing second medical device26to expand, move, or decouple from balloon14or elongated member12, and occupy the target site. In some examples, the operational pressure may be more, less, or the same as the predetermined pressure. In another example, balloon14may not be inflated to the predetermined pressure (40) prior to introducing balloon14into vasculature of a patient (42). Rather, pressurizing the balloon to an operational pressure (44) may sufficiently rupture the non-compliant layer of middle layer34.

In some examples, the technique ofFIG. 4includes, after the pressurizing (44), deflating balloon14(46). A clinician may, for example, withdraw inflating fluid from inflating lumen port22to cause balloon14to depressurize and contract, shrink, collapse, fold, or otherwise attain a compact configuration allowing safe withdrawal of balloon14afrom the vasculature. After deflating balloon14(46), the clinician may withdraw balloon14from the vasculature (48). For example, elongated member12carrying balloon14may be withdrawn from the vasculature.

While the example technique ofFIG. 4is described with respect to the vasculature, the example technique ofFIG. 4may be used to advance and deploy balloon14at a target site within any body lumen accessible through a body opening or incision. Thus, an example technique for using balloon14has been described with reference toFIG. 4.

Example techniques for manufacturing or preparing balloon14are described with reference toFIG. 5, which is a flowchart illustrating an example technique for manufacturing balloon14. In some examples, the technique ofFIG. 5may include coextruding a non-compliant layer on inner layer36(50), and coextruding outer layer36on the non-compliant layer (52). As described with reference toFIGS. 3A-3D, in some examples, middle layer34includes the non-compliant layer. In some examples, inner layer36, middle layer34including the non-compliant layer, and outer layer32are coextruded simultaneously. For example, respective heated, flowable, or molten compositions for inner layer36, middle layer34, and outer layer32may be coextruded from an extrusion die onto a substrate, for example, a mandrel. As described elsewhere in the disclosure, coextrusion of the different layers may be used to obtain a nested configuration of balloons without requiring a nesting step. A nesting step including nesting individual balloons may introduce fluid or air pockets or other nonuniformities in the balloon structure. In contrast, coextrusion of multiple layers results in a uniform balloon structure. In some examples, the technique ofFIG. 5may include coextruding a tubing including inner layer36, middle layer34including the non-compliant layer, and outer layer32.

In other examples, inner layer36, middle layer34, and outer layer32may be coextruded as a multilayer sheet, for example, by coextruding onto a flat substrate. In some examples, inner layer36, middle layer34including the non-compliant layer, and outer layer32may be sequentially extruded. In some examples, a pair of layers may be coextruded, followed by extrusion of another layer. For example, middle layer34and inner layer36may be coextruded, followed by extrusion of outer layer32on the coextruded structure. In some examples, middle layer34and outer layer32may be coextruded, followed by extrusion of inner layer36on the coextruded structure. In some examples, the order of layers during extrusion or coextrusion may be different from the order of layers in balloon14. For example, when balloon14includes three or more layers, pairs or groups of layers may be coextruded, and reordered, stacked or otherwise combined in a mold followed by pressurizing in the mold to eventually form balloon14.

In some examples, the extrusion or coextrusion die for middle layer34may be configured to extrude middle layer34defining at least one of a discontinuity, a perforation, a window, or an opening. In some examples, the discontinuity, the perforation, the window, or the opening may be stamped, cut, or otherwise formed in middle layer34after extrusion or coextrusion of middle layer34, and before middle layer34is eventually assembled into the multilayer wall15aof balloon14a.

Balloon14may be formed from the multilayer tube or sheet including inner layer36, middle layer34including the non-compliant layer, and outer layer32(54). For example, the multilayer tube or sheet may be placed in a mold configured to provide the shape of the balloon, and may be expanded to occupy the periphery of the mold before the tube or sheet has cooled or otherwise cured or solidified. In some examples, the respective compositions for inner layer36, middle layer34including the non-compliant layer, and outer layer32may be directly coextruded into the mold, so that balloon14is shaped during coextrusion. In some examples, one or more of inner layer36, middle layer34, and outer layer32may be extruded onto a reinforcing substrate, for example, a reinforcing fabric, an or an arrangement of reinforcing components or fibers. In some examples, reinforcing components may be introducing during the coextrusion.

The coextruding (50and52) may include stretching balloon14. For example, a region or side of balloon14may be intermittently heated or stretched during or after the coextruding. In some examples, the stretching may include double stretching, or stretching balloon14from two sides. In some examples, the stretching may include a primary stretching at a first pressure followed by a secondary stretching at a second pressure. The stretching may promote a uniform wall thickness and promote uniform inflation of balloon14.

In some examples, the technique ofFIG. 5includes heat-setting balloon14(56). In some examples, heat-setting may include annealing, for example, heating and maintaining balloon14at a predetermined temperature for a predetermined period of time. The predetermined temperature may be near or above a melt transition of one or more of layers32,34, or36, or near or above a glass transition temperature of one or more polymers in layers32,34, or36. Heat-setting may remove creases, wrinkles, or marks from surfaces of balloon14, and may further provide a uniform thickness to a wall of balloon14, for example, wall15aof balloon14a. For example, heat-setting may also be used to control the wall thickness of wall15aof balloon14a. Heat-setting may be performed using any suitable technique. For example, balloon14may be heated in the mold, such that the heat-setting may provide a permanent set or shape for balloon14. Heat-setting may be used to control compliance of one or more of layers32,34, or36, or overall compliance and burst resistance of balloon14. In some examples, the configuration of balloon14as molded and heat-set may correspond to an uninflated configuration of balloon14. In some examples, the configuration of balloon14as molded and heat-set may correspond to an inflated configuration of balloon14.

In some examples, the technique ofFIG. 5may include inflating balloon14to a predetermined pressure sufficient to rupture middle layer34including the non-compliant layer (58). The predetermined pressure is insufficient to rupture both inner layer36and outer layer32. For example, inflating balloon14to the predetermined pressure may result in formation of structures corresponding to balloons14a,14b,14c, or14das described with reference toFIGS. 3A-3D. In some examples, the technique ofFIG. 5may include inflating balloon14to allow only the non-compliant layer to fragment at the predetermined pressure to cause inner surface32bdefined by outer layer32to contact outer surface36adefined by inner layer36.

In some examples, inflating balloon14to the predetermined pressure (58) may result in delamination of one or both of outer layer32from middle layer34or of middle layer34from inner layer36. For example, outer layer32may delaminate from middle layer34, or middle layer34may delaminate from inner layer36, during the inflating (58). In some examples, at least partial delamination may occur before the rupture of middle layer34. For example, at least a portion of one of outer layer32, middle layer34, and inner layer36may separate from a portion of another of outer layer32, middle layer34, and inner layer36, before the rupture of any portion of middle layer34. In some examples, complete delamination may occur before the rupture of middle layer34. For example, outer layer32may completely delaminate from middle layer34, and middle layer34may completely delaminate from inner layer36, before the rupture of any portion of middle layer34. In other examples, delamination may overlap with rupture during the inflating (58). For example, at least a portion of one of outer layer32, middle layer34, and inner layer36may separate from a portion of another of outer layer32, middle layer34, and inner layer36during rupture of a portion of middle layer32.

While forming balloon14(54) may precede inflating balloon14(58) as shown in the example ofFIG. 5. In other examples, balloon14may be inflated to the predetermined pressure sufficient to rupture non-compliant middle layer34during forming balloon14(54). Thus, one or both of delamination or rupture of non-compliant middle layer34may occur during forming balloon14(54), and the example technique may not include an additional or separate inflation of balloon14to the predetermined pressure sufficient to rupture balloon14(58).

In some examples, the technique ofFIG. 5may further include securing second medical device26to balloon14(60). For example, when second medical device26includes a stent, securing second medical device26to the balloon (60) may include crimping the stent to balloon14.

In some examples, the technique ofFIG. 5may further include mounting balloon14to elongated member12(62). For example, elongated member12may include a catheter body, and balloon14may be mounted to the catheter body.

Other techniques for forming balloon14may be used in other examples.