CA2100091A1 - Low profile balloon catheter and method for making same - Google Patents
Low profile balloon catheter and method for making sameInfo
- Publication number
- CA2100091A1 CA2100091A1 CA002100091A CA2100091A CA2100091A1 CA 2100091 A1 CA2100091 A1 CA 2100091A1 CA 002100091 A CA002100091 A CA 002100091A CA 2100091 A CA2100091 A CA 2100091A CA 2100091 A1 CA2100091 A1 CA 2100091A1
- Authority
- CA
- Canada
- Prior art keywords
- wall
- balloon
- transition
- thickness
- central
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M25/00—Catheters; Hollow probes
- A61M25/10—Balloon catheters
- A61M25/1027—Making of balloon catheters
- A61M25/1029—Production methods of the balloon members, e.g. blow-moulding, extruding, deposition or by wrapping a plurality of layers of balloon material around a mandril
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M25/00—Catheters; Hollow probes
- A61M25/10—Balloon catheters
- A61M25/1027—Making of balloon catheters
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M25/00—Catheters; Hollow probes
- A61M25/10—Balloon catheters
- A61M2025/1043—Balloon catheters with special features or adapted for special applications
- A61M2025/1075—Balloon catheters with special features or adapted for special applications having a balloon composed of several layers, e.g. by coating or embedding
Abstract
2100091 9211892 PCTABS00014 A non-distensible balloon (16) is adapted to be disposed circumferentially on a tube (12) having an elongate axis and to be compressed against the tube (12) to achieve a low profile. The balloon (16) includes an end wall (21), a central wall (27), and a transition wall (32) defined by a height transition region having a first axial length and defined by a thickness transition region having a second axial length less than the first axial length. An associated method includes the step of reducing the average volume of material per unit axial length in the transition wall of the balloon relative to the average volume of material per unit axial length in either the end wall or central wall of the balloon.
Description
~92t11892 - P~rJIJS92~307 LOW PROFILE BALL~9~-5~I~E3~B
A M~ E~ d~
CKGROUND OF T~INVENT~
The present inven~ion relates generally to surglcal devices, and more specifically to nondistensible balloon catheters.
~t Balloon catheters ar~ used to dilate or occlude various body conduits, cavities and openings ~uch as blood vessels and the urethra. This is norma1ly accomplished with a catheter formed from an elongate cannula and an inflatahle balloo~ disposed circumferentially of tAe cannula near the dist~l end o~ the catheter.
In accordance with a typical procedure, the catheter is provided with the balloon in a deflated or otherwise low profile state. With this co~iguration, the catheter is introduced into the body co~duit and posit.ioned with the balloon in the low profile state at the point of desired : dilatation. At this point the balloon is inflated or ~otherwise expanded to a high profile state thereby radially stretchlng the walls o~ the conduit.
This procedure is particularly applicable in the case of blood vessels which are occluded by plaque. In such a procedure, t:he balloon in its low pro~ile state i5 positioned in proximi~y ~o ~he plaque. At this poin~ the : balloon is inflated to press the plaque radially against .
::
WO~2/~l~92 - PCr/US92/U030 :2 the walls of the blood vessel and thereby dilate or open the vessel to blood flow.
The procedure is also applicable for dilating large body conduits such as th~ gastrointestinal tract or the prostatic urethra. In the latter case, restrictions are common to men of older age where the prostate, which encircles the urethra, tends to grow inwardly ~hereby restricting the urethra pas~age. With the balloon in i~s low profile state, the. catheter can be inserted into the urethra until the balloon is positioned in proXimity to the restriction. At this point the balloon can be inflated to dilate the urethra and thereby increase the flow capacity of this conduit.
These dilatation catheters are typically characterized by nondistensible balloons which are formed from materials such as polyethylene that are relati~ely inflexlble and therefore - 20 do not expand or distend significantly beyond a known dimension. This characteristi~ of non-distensibility is of par~iGular advantage in order to insure that the vessel or conduit is not injured by overextension. Unfortunat~ly, the rPlatively inflexible ma~erials which produce the nondistensible characteriitics, tend to inhibit the ability of the balloon to be rolled, compressed, collapsed, deflated or otherwise formed into a low pro~ile state.
Such a state is of paxkicular int~r~st in ordPr that the catheter can be easily inser~ed into the vessel or conduit.
:~
Nondistensible balloons are typically formed circumf~rentially ~nd co-axially on the cannula. The balloons are characteri2ed by two cylindrical end reglons which are attached to the cannula, a cylindrical c~ntral region which is spaced ~rom the cannula when the balloon i5 .
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W~92~11892 - PCT/U~2/~ ~7 U ~ l ~
infla~ed, and a pair o~ conica:l transition regions each extending from an associated end region outwardly to the central region.
With this configuration, the nQndistensible balloons of the past have been blow molded from materials which are commonly provided in the confi~lration of a tube having a substantially constant wall thickness. In the blow molding process, the walls o~ the tube are expanded agains~ the -10 inner surface of a mold which is provided with a shape desired for the balloon. Ends of th~ balloon remain at the initial diameter and thickness o~ the tube, while the central region of th~ balloon expands to the maximum diamet~r and minimum wall thickness of the balloon. It is these walls in ~he cen~ral region, which may have a thickness reduced by a factor as much as 100, that dictat~
the strength o~ the balloon. Between the c~ntral region and each of the end regions of the balloon, one of the transition zone~ is characterized by a wall thickness which varies from the original thick~ess of the wall of the tube to the reduced thickness of the wall of the central region.
When these nondistensible balloon catheters are initially inserted, it is of par~icular importance that the balloon be rolled on the catheter tube to the smallest : diameter in order to provide the catheter with the lowest profile possible. The rolling of the balloon has not been a problem in the end regions. Even though end walls contain the thickest wall s~ction, they are fixed in close proximity ~o the cannula and therefore maintain a low profile even when the balloon is in~lated~ Similarly, rolling the balloon on the cannula has not been a problem in the central reqion. Even though the walls in ~his region are disposed at the highest radial distance ~rom the cannula, the very thin walls in this region are adaptable .:: ., : , :: ., , . , ,, : ,. . :
W~2~ 2 PCT/US92/~3~7 to being xolle~ into close compliance wi~h the cannula.
:: However, in the transition reglons of the balloon, both the thickness of the wall and t:he radial displacement of the ; wall tend to create a problem. Although the transition - 5 wall is thinner than ~hat in the end region, it is disposed at a ~reater radial distanGe than the end wall. And although this radial distallce is less than that of the central region, the wall thickness is greater a~d therefore more rigid than the central region.
When a nondistensible balloon of the past has been rolled onto a cannula, it has resulted in enlarged sections at each transition region, giving the rolled balloon the appearance o~ a dog bone. These enlarged transition sections typically hav~ diameters as much a~ 50~ greater than those associated with either the c~ntral section or the end section of the rolled balloon. Furthermore they tend to form sharp corners which can severely damage ~he body condu~t during ~oth in~ertion and withdrawal of the catheter..
With these deficiencles of the prior art, it is an object of the present in~ention to provide a balloon cakheter wherein the b~lloon can be ralled or otherwise compr~ssed onto the catheter ~ube to a diameter which is substantially constant along the entire length o~ the rolled balloon.
.
~0 In accordance with the present invention, a balloon cathe~er is proYided wherein th~ balloon can he rolled on the cathet:er tube to a pro~ile which is substantlally constant in diam~ter along the length of the balloon.
Further~ore, there are no sharp points associated wit~ this , W~ 92/1189~ - P~r/uss2/oo3o7 low profil~. As a re~ul~, the great~st diameter of the catheter with the balloon in its low profile state, is reduced by as much as 5G% with substantially no sharp edges to damage the body conduit.
In one aspect of the invention, a nondistensible balloon is adapted to be rolled on a cannula having an elongate axis, in order to achi~ve a low proile. The balloon comprises an end wall diiposed in an end region of the balloon and having a ~ixed circumferential relationship with the cannula. A central wall disposed in a central region of the balloon is displaced from the cannula when the balloon is inflated. A transition wall disposed between the ~nd wall and the central wall includes a height transition xegion where th~ transition wall extends from the height of the end wal} to the height of the central wall, and a thick~essi transition r~gion where the transikion wall extends from the thickne~s of the ~nd wall to the thickness of the central wall. The axial length of the thickness transition zone is less than the axial length of the height transition zone.
In another aspect o~ the invention, a method for making a nondistensible balloon characterized by an end wall, central wall and ~ran~iition w~11, includes the fi~ep of providing a blow ~old having an end wall surface, a central wall surface and a transition wall surface equivalent to the external shape desired ~or the respective end wall, ce~tral wall and transition wall when the balloon is inflated. The method further comprises the steps o~
inserting a tube of material into the mold and blow molding the material of the tube ag~inist the surface o~ the mold.
Finally, thP process calls for reducing the quantity of material per unit length in the transition wall to an amount less than the average volume of material per unit ~ .
' ' . : .. , ' .
W~92~ 92 - P~/U592/~307 ~lUUlj91 length in ~i~her ~he end wall or ~the central wall of the . balloon.
In other aspects of the invention, the traditional S blow molding method is alte!red by pro-~iding the tu~e of material with a reduced wall thickness in those areas which correspond to the transition reqions of the balloon. This automatically reduces thP guanttty of ~at~rial and hence - the thickness of the transition walls.
In another method, a balloon formed in accordance with the prior art is inserted into a funnel or mold which is configured to receive at least the transition wall of the balloon. This second mold is heated to increase the flexibility of ~he balloon in the tra~sition region, and the balloon is str~tched axially to thin the heated wall.
In still a ~urther method, th~ blow mold is formed with recPs~es in the transition surface. In such a mold, the balloon is for~ed with projections in the transition reglon, which increase the surface area and therefore decrease the thickness of the transition walls.
These and other features and adva~tages of the in~ention will be more apparent with a description of preferred embodiments and referPnce to the associated drawings.
:
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Fig. 1 is an axial cross-ssctisn view of one embodiment of a balloon cathet:er o~ the present invention, showing the catheter operat:ively disposed in a body conduit;
Fig. 2 is an axial cross-section view o~ a balloon associated with the prior ~rt rolled onto a cannula and illustrating the dog bone profile associa~ed with the prior art;
Fig. 3 is an axial cross-section ~iew illustrating the low profile, rolled characteristics a~ociated with the balloo~ of Fig. l;
Fig. 4 illustra~es a top plan view of a blow mold used in the prior art method for making the balloon illustrated in Fig. 2;
: Fig. 4a is an axial cross-section view of blow mold ~ tubing used in the prior art method;
- Fig. 4b is an axial cross-section view o f the tubing of Fig. 4a being heated in the prior art process;
Fig. 4c is an axial cro~s-~ection view o~ the tubing o~ Fig. 4 coaxially disposed in the mold of Fig. 4;
30: Fig. 4d illu~trates the blow molding step in the process of the prior art;
Fig. 5 i.s an enlarged axial cross-sec~ion view of one quadrant o~ the balloon of the prior art illustrated in an inflated sta1:e;
W~92/~9~ ~ P~T/U~2/~3~7 ~1~lj091 Fig. 5a is a cross-sec~ional view taken alony lines 5a-5a of Fig. 5;
FigO Sb is an axial c:ross-sacti4n view taken along lines 5b 5b of Fig. S;
Fig. 5c is an axial cross-section view taken along lines 5c-5c of Fig. 5;
Fig. 6 is an axial cross-section view of one quadrant of the balloon of Fig. 1 illustrated in an inflated state;
Fig. 6a is a cross-sectional view taken along lines :
6a-6a of Fig. 6;
~5 Fig. 6b is an axial cross~s~ction viaw taken ~long lines 6b-6b o~ Fig. 6;
Fig. 6c is an axial cross~-section view taken along lines 6C-6C Gf Fig 6;
Fig. 7 is an axial cross-section ~iew ~imilar to Fig.
6 of a further embodiment of the balloon associated with the present inventiQn;
Fig. 7a is a cross-sectional view taken along linas 7a-7a of Fig 7;
Fig. '7b is an axial cross~section view taken along lines 7b-7b of Fig. 7;
Fig. 7c is an axial cross-section view tak@n ~long lines 7c-7c of Fig~ 7; .;
W~2/~l~s2 ~ PCT/US92/~;
~UI~l~9~
:Fig. 8 is an axial cross-section vi~w of bump tubing used in a method o~ the present inv2ntio~;
Fig. 8a is an axial cross-section Yiew of the bump tubing ~f Fi~. 8 inserted in ~ conventional blow ~old associated with the present invention;
Fig. 8b is an axial cross-s~ction view showing the molded balloon with a ~ran~ition wall of su~stantially constant thickness;
Fig. 9 is an axial cross-section view of a second mold or funnel associated with a urther method of the present invention;
Fig. 9a illustrate~ a balloon dispo~ed in the funnel of Fig. 9, heated, and stretched in the transition region to form a transition wall o~ reduced thickness;
20Fig. 10 is a top plan view of a blow mold associated with a fuxther method of the present inv~ntion;
Fig. lOa is an axial cross~section view of the balloon disposed in the mold o Fig. 10, heated, and axially stretch~d in the tran ition region~ to provide a transition wall of reduced thickne~s;
Fig. 11 i~ a top plan view o a mold associated with a further method of the present invention;
Fig. 12 is an axial cross-section view of a conventional b~alloon with a sle~ve bonded to the central regions o~ the balloon; and W~92/11~9~ - PCT/US~2/~307 0 '~ 1 1~
Fig. 13 is an axial cross-section view of two balloon portions wherein central rlegions of each balloon portion are overlapping and bonded t:o increase the thickness of the central wall of the balloon.
Description oP Preferred Embodlments lOA dilatation catheter is illustrated generally in Figure l and designated hy the reference numeral lO. The :
catheter lO is operatively disposed in a body conduit de~ined ~y walls ll, and includes an elongate cannula 12 having a distal end 14 and a proximal end (not shown~.
The catheter lO also includes a balloon 16 having a distal end wall 18 and a proxi~al end wall 21 dispssed in respective end regions 23 and 25 of the balloon 16.
central wall 27 is disposed between the end walls 18 and 2l in a central region 30 of the balloon l6.
In thls particul~r embodiment the end walls 18 and 2l are .relatively thicX and relatively small in diameter.
This is in compari~on to ~he central wall 27 of the balloon 16 which is relatively thin and relatively large in diamet~r.
'~
A pai.r of transition walls 32 and 34, each having a generally conical configuration, are o~ particular interest to the present invention. The transition wall ~2 is disposed in a proximal transition region 36 between the end region 25 and the central region 30. The transition wall 34 is disposed in a di~tal transitio~ regio~ 38 between the end region 23 and the ~ntral region 30 of the balloon.
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". . .. , . . ~ i ; ... , : : . ~ . . . . . . . .
WO92t11892 - PCT/US92/~307 Two separate ~ran~itions occur to th~ walls 32, 34 in each of the transi~ion regions ~6, 38. First, the walls 32, 34 are each characterized by a transition in height from the height of the respective end walls 18, 21 to the height of the central wall 27. This transition region will be referred to as the height tranrition region 4l. Second, in the transition regions 36, 38 the walls 32, 3~
respectively, undergo a transition from their greatest thickn~ss in proximity to the end region 25, 23 respectively, to their least thickness in proximity to the central region 30. This transition region is referred to as the thickness transition region 43. It is the relative axial length of the two regions of transition, the height transition region 41 and the thickness transition 431 which are of particular interes~ in this ca~.
I~ accordance witn the present invention, the thickness transition region 43 has a shorter axial dimension than does the height ~ransition region 41. This occurs because the thickness of the end wall 21 thins to a dimension generally equiYalent to the thickness o~ the central wall 27 over a relatively ~hort distance along the transition wall 32. It is particularly desirable that this thickness transition region 43 be positioned in close proximity to the end wall 21 so that a~y substantial wall thickness associated with the region 43 is closely spaced to the outer surface of the ca~nula 12.
As will be discus~ed in greater detail below, the balloons of the prior art have a thickness transition region 43 which i5 generally equivalent in axial length to the height transition region 4l. In other words, the thickness of the transition wall 32 gradually decreases over the entire axial distance between the end region 25 and the central r~gion 30. While this does not adversely ,.
W~92/~1~92 - P~/U~92~307 ~ l U ~ d ~ l affect the balloon in its infla~ed, high profile state, it has a dramatic af~ec~ on the rolled, low profile state of the balloon as illustrated ln Figure 2. With the relative thickness of the transition wall spaced even a short radlal distance ~rom the cannula 12, the balloon 10 in its rolled confi~uration tends to have an undesirable dog bone shape.
. Thus in the low profile state, in the low profile state, enlargements occur at both o~ the transition regions 36 and 38 with the halloon of the prior artO It is in these regions that the respective walls 32 and 34 are too thi~k and too far displaced from the cannula 12 to adequately ~omply to the cannula in the rolled state.
~y thinning the walls 32 and 34 of the transition 15 regions 36, ~8 respectively, the walls of the balloon 16 are either thick in proximity to the cannula 12 or thin at any substantial xadial distance from th~ cannula 12. It is in this manner that the balloon of Figure 1 in the rolled ..
configuration achieves a low profile state as illustrated in Figure 3.
An understanding of the wall thickness associated with the transition zones 36, 38 and its effect on the rolled configuration of the balloon 10 will be better understood with re~erenc~ to a typical blow molding process used to manufacture the balloon o~ the prior art. Figure 4 and Figures 4a-4d illustrate steps ih a hlow molding process of the prior art; however, some of these steps also apply to the ~ethods associa~ed with the present invenkion.
In the plan view o~ Figure 4, a blow mold 50 is illustrated with an in~er mold surface 52 which defines ~ .
ca~ity 54 having the shape desired for the external surface of the bal.loon 16. Thus tha surface 52 includes end :
35 sur~ac~s.56, 58 which correspond to the end regions 23, 25 ~, ,; .
' ., : . . . ~ . . . ~ . . . . . . .. .. ..
W~92/11892 - PCr/US~/~307 respectively, a central sur~ace 61 which corresponds to the cen~ral region 30, and transition surfaces 63, 65 which correspond to the transition ret~ion~ 36, 38 respectively.
In accordance with this process of the prior art, matexial is provided in the for:m o~ a tube 67 which has a generally cylindrical con~iguration and a relatively constant wall thickness as illustrated irl Figure 4a. The tube 67 is heated, for example in a conventional ~ven 69, to provide the tube 67 with a generally limp, pliable conf iguration . In this state, the tube 67 is inserted into the mold 50 and stretched axially as shown by the arrows 70 in Figure ~c. This axial s~retching tends to align the tube 67 coaxially with the cavity 54 of the mold 50.
At this point in the process, one end o~ the tube 67 is ~ealad by a cla~p shown generally at 72 in Figure 4d~
The other end of the tube 67 is in~lated by a fluid, such as air, provided by a compressor 74. This air is blown into the heated tube G7 stretching the walls of the tube 67 until they contact the surface 52 of the mold 50. Upon contact, the walls of the balloon 16 are cooled by the mold 50 and ~rozen in their expanded state.
It will be apparen~ with referenc~ to Figure 4d that the volume of material per unit length provide by the tube 67 will also be equivalent to the ~olume o~ material per unit leng~h o~ the walls fo~ming ~he balloon 16. Where ~he central wall 27 is greatly spaced from the axis of the ~alloon, this constant volume will necessarily require a reIatively thin central wall 27. Where th~re is substantially no radial displaoement of th~ tube 67, for exampIe in the end region 23, 25 the thickn~ss of the respective end walls 18, 21 will be substantially th~ same as the thickness as the wall~ of the tube 67. Along the WO g2~ 92 Pcr/uss~/~307 .~4 transition walls 32, 3~, the resul~ achieved with the formation of the end wall~ 18, 21 ~iYes way to the result achieved with the formation of the central wall 27. Thus the greater the radial displacement of the walls of the tube 67, the less the thickness of the resultiny ~all of the balloon 16.
In a ~urther description of the invention, ~ocus will be dira¢ted primarily to the transition region 36 lo illustrated in the upper left hand corner o~ the balloon 16 in Figure 1. However, the comments will apply equally as .~-well to the quadrant o~ the balloon 16 in the lower left hand corner of Figure 1~ Comments ~ay also apply to transition region 38 illustrated on the right hand side of 15 the balloon 16 of Figure 1. -.
ThP transition region, ~uch as the region 36, is illustrated for a balloon o~ the prior art in the enlarged ~:
YieW of Figure 5. In this view it i~ apparent that the thickness transition zone 43 is substantially equival~nt in axial dimen~ion to the thlckness transition zone 41.
Because there is substantial thickness o~ the wall 32 in the transition zone 36 at substantial radial dimensions from the cannula 12, the balloon 16 in the rolled configuration has the dos bone pro~ile illustrated in Figure 2. The thickn~ss of the walls 21, 32 and ~7 is measur~d and discus~ad with respect to their dimen~ion in a radial plane as illustrated by the thickness "t" in Figure 5. ~.
As long as the ~olume of material p~r unit axial length remains constant along th~ walls of the balloon 16, as is the case with the balloons o~ ~he prior art, a relation~hip carl be establi~h~d based on the thickness "t"
35 at any two locations along th~ balloon walls~ Figures sa, --, . , , ., , , .......... .. ~ , , ~ . .................... :
. , . ~: , . .......... . . . .
. .
WO~2/11892 P~T/U~2/~307 5b and 5c show radial cros~/se!ctions of the prior art balloon in Figure 5 taken along ~he lines 5a, 5b and 5c respectively. Re~erring to Figure 5h, th~ transition wal7 32 has a thickness t, at a point "l" in Figure 5. This thickness t~ is equivalent to the differ~nce between the inner radius r~ and the outer radius R~ of the wall 32.
Similarly in Figure 5c, the wall of the balloon 16 has a thickness t2 at a point "2" between the central region 30 and the transi~ion region 36. This thickness t2 is equivalent to the difference between the inner radius r2 and the outer radius R2 f the wall 32. If the volume per unit length of material in the walls 21, 32 and 27 is equivalent, as is the case with th~ balloons of the prior art, then the shaded ar~as in Figures 5b and 5c will be equivalent in size. It follows that the thicknPss of the wall at any point, such as the point l, can be determined given the radii rl and Rl at point l, the thicXness at any point 2 and the associated radii r2 and ~ at point 2. It follows that this relationship is establishPd by the following Formula I:
'Cl = t2 ( ~ R~ ) This relationship has existed in the prior art and has yiven rise to the noncompliant, dog bone shape of the balloon 16 in its low profile configuration as illustrated in Fi.gure 2. In accordance with the present invention, the thickness tl will be given by the following Formula II:
- - - . . . . . . . : . . .
. .
W~92~1~892 - PCT/~92/~3~7 t1 < ~2(r2 + R~) This is illustrated in the embodiment of Figure 6 where the thickness t~ at t'he point 1 is substantially equivalent to the thickne~s t2 at the point 2. The conditions of Formula II will be met since the sum of r~ +
R~ is 1Q~S than the sum of r2 ~ Rto This can be appreciated by merely noticing that the ~haded area in Figure 6b has a smaller area than do s the shaded area in Figure 6c.
In particular embodiments of the invent.ion, it is desirable that the axial l~n~th of the thickness transition region 43 be maintained a~ less than on~-hal~ the axial length o~ t~e height transition region 41. ~n the most pre~erred embodim~nt, the full transitlon in thickness from the ~hickest wall ~1 ~o the ~hinnest wall 27 occurs within only one-fourth of the axial di~tance along the height transition region 41. Of course, the maximum advantage is ~ .
achieved where the wall ~2 is consistently thin throughout ,' the entire height transition reqion 41. And in an ideal case, the end wall 21, the transition wall 32, and central wall 27 alI have the same thinness. Even in this case the stre~gth of the balloon is still d~termined by the thickness of the central wall 27.
.
This r~.duced wall thickness of the transition region 36 can be provided in an embodiment where the walls 32 are provided with an increa~ed area so that they are automatically thinned due to the scarcity o~ the ~aterial. :
In the embodiment o~ Fi~ure 7, the increase~ area in t~e transition region 36 is provided in the ~orm of projections 81. By adding these projections 81, the area of the balloon in the region 36 is increased ~o that the thicknes~
.
i, .'.' : ; ' ' ` ' ' ' ~ .
,' ;. '' ,, ', '',,, ".' ., ,. :' ~,' ' ', '' ' ' ' , ' ., ' :` ',, ' W~92/1189~ - PCT/U59~/W307 of the wall 32 is sub~tan~ially ~quivalent to the wall 27.
In such an embodiment, the thin walls in the transition region 36 are as compliant as the walls 27 in the central region 30. This facilitates rol:Ling the balloon into a low profile sta~e as illustrated in Figure 3.
The ~alloons of the present invention also can be made in accordance with a preferred method ~hown by the ~ eps illustrated in Figures 8-8b. Thus the process of Figure 4 can be revised in the step illustrated in Figure 4a by providing the tube 67 in a configuration illustrated in Figure 8. In this case, the tube 67 has walls o~ generally constant thicXness in ~ pair of end zones 90 and 92 which are associated with the end r~gione 23 and 25 respectively o~ the balloon 16. The wall of the tube 67 has a greater cross sectional area in a central zone 94 which is associated with the central region 30 o~ the balloon 16.
Between each o~ the zo~es 90, 92 and the central zone 94, a pair of transition zones 96, 98 respectively, are ~ 20 provided which supply the matarial associated with the transition regions 36 and 38 of the balloon 16.
The walls of the tube 67 in the transition zones 96, 98 have reduced cros~-sectional area relative to the walls in the cen~ral zone ~4. When the tube o~ Figure 8 is inserted into the mold 50 as illustrated in Figure 8a, the reduced material availa~le in the transition zones 96, 98 automatically produces a balloon 16 with transition regions 36, 38 of reduced thickness. In this manner, the balloon o~ Figure 1 can be produced in accordance with the method steps illustrat:ed in Figures 8 - 8b.
Referring to Figures 9 and ga, it will be apparent that all of the steps associated with Figures 4-4d which produce the prior art balloon of Figure 5, are equally W092/~892 . ~CT/US~2/~307 0 9 ~
applicable to an improved pro~ess wherein a second mold is provided in the shape of a fllnnel 101. The funnel 101 can be formed ~rom stainless st~el or other suitable material and surrounded by induction coils 103. An inner surface 105 of the funnel 101 is provid~d wi~h the shape desired for the exterior surface of t:he balloon 16 particularly in the transition region 36.
In this extended process the induction coils 103 can be energized by a signal from a radiofrequency generator 107. This radiofrequency energy is induc~ively coupled to the Punnel 101 to heat the interior surface 105. Inserting the balloon 16 of the prior art into the funnel 101, as illustrated in Figure 9, heats the transition zone 36. ,:~
When axial tension is applied to the end wall 21 o~ ~he balloon 16, as illu~trated by the arrow 109, th2 hPated transition wall thin~ to the reduced thickness illustrated in Figure 6.
In a similar method illustrated in Figures 10 and lOa, the mold 50 is provided with a pair of end sections llo and 112, a ce~tral section 114, and a pair of transition .:
sections 116 and 118. In this case, the material forming the transition ~ections 116, 118 and the end sections 110 and 112, is preferably heatconductiYe, such as metallic, while the material forming the central section 114, is preferably non-heakconductlve such as pla~tic.
With the. balloon 16 disposed in the mold 50, the entire mold can be heated by a heater 119 to inGrease the temperature O:e the metallic sections 116, 118, 110 and 112~
The plastic s~ction 114, however, will not easily transmit the h~at ~o the cP~tral regi4n 30 of the balloon 16 remains relatively cool. By axially stretching the balloon 16 under these conditions, the heated material in the .. . . . . . .
WQ 9~/11892 PCr/~S92/00~07 transition regions 36, 3~ and ~he end re~ions 110, 112 will be thinned to provide ~he balloon 16 with the configuration illustrated in Figure 8b.
In still a further method of the present invention the mold 50 illustrat~d in Figur-e 4 can be modified by providing recesses 125 in the transition sur~aces 63 and 65. Usiny the remainder of the steps illustrated in Figures 4a-4d will produce a balloon 16 having the configuration illustrated in Figure 7. With the reduced wall thickness provided by ~he projections 81, the balloon 16 can be rolled to a low profile state as illustrated in Figure 3.
As previously discussed, ~he strength of the ~alloon 16 is dictated primarily by the wall thickne~s in the centr l region 39 while the problems a~sociated with the low profile are dictated primarily by the wall thickness in the transition zones 36, ~8. The prior art has not been able to d~velop reduced wall thicknesses in the transition zones 36 and 38 which are ~uffiGiently thin to avoid the dog bone effect without sacrificing strength in the central - region 30.
A M~ E~ d~
CKGROUND OF T~INVENT~
The present inven~ion relates generally to surglcal devices, and more specifically to nondistensible balloon catheters.
~t Balloon catheters ar~ used to dilate or occlude various body conduits, cavities and openings ~uch as blood vessels and the urethra. This is norma1ly accomplished with a catheter formed from an elongate cannula and an inflatahle balloo~ disposed circumferentially of tAe cannula near the dist~l end o~ the catheter.
In accordance with a typical procedure, the catheter is provided with the balloon in a deflated or otherwise low profile state. With this co~iguration, the catheter is introduced into the body co~duit and posit.ioned with the balloon in the low profile state at the point of desired : dilatation. At this point the balloon is inflated or ~otherwise expanded to a high profile state thereby radially stretchlng the walls o~ the conduit.
This procedure is particularly applicable in the case of blood vessels which are occluded by plaque. In such a procedure, t:he balloon in its low pro~ile state i5 positioned in proximi~y ~o ~he plaque. At this poin~ the : balloon is inflated to press the plaque radially against .
::
WO~2/~l~92 - PCr/US92/U030 :2 the walls of the blood vessel and thereby dilate or open the vessel to blood flow.
The procedure is also applicable for dilating large body conduits such as th~ gastrointestinal tract or the prostatic urethra. In the latter case, restrictions are common to men of older age where the prostate, which encircles the urethra, tends to grow inwardly ~hereby restricting the urethra pas~age. With the balloon in i~s low profile state, the. catheter can be inserted into the urethra until the balloon is positioned in proXimity to the restriction. At this point the balloon can be inflated to dilate the urethra and thereby increase the flow capacity of this conduit.
These dilatation catheters are typically characterized by nondistensible balloons which are formed from materials such as polyethylene that are relati~ely inflexlble and therefore - 20 do not expand or distend significantly beyond a known dimension. This characteristi~ of non-distensibility is of par~iGular advantage in order to insure that the vessel or conduit is not injured by overextension. Unfortunat~ly, the rPlatively inflexible ma~erials which produce the nondistensible characteriitics, tend to inhibit the ability of the balloon to be rolled, compressed, collapsed, deflated or otherwise formed into a low pro~ile state.
Such a state is of paxkicular int~r~st in ordPr that the catheter can be easily inser~ed into the vessel or conduit.
:~
Nondistensible balloons are typically formed circumf~rentially ~nd co-axially on the cannula. The balloons are characteri2ed by two cylindrical end reglons which are attached to the cannula, a cylindrical c~ntral region which is spaced ~rom the cannula when the balloon i5 .
~' ' . ''. . '., ' .' ,' ' '. ' " ' ', .: . ' '' ' .',, ' ' .. ' .' ' ' ' ' " ' "' ; ' ., '' ". '" '''' ' ' " '' ' . ' '~
W~92~11892 - PCT/U~2/~ ~7 U ~ l ~
infla~ed, and a pair o~ conica:l transition regions each extending from an associated end region outwardly to the central region.
With this configuration, the nQndistensible balloons of the past have been blow molded from materials which are commonly provided in the confi~lration of a tube having a substantially constant wall thickness. In the blow molding process, the walls o~ the tube are expanded agains~ the -10 inner surface of a mold which is provided with a shape desired for the balloon. Ends of th~ balloon remain at the initial diameter and thickness o~ the tube, while the central region of th~ balloon expands to the maximum diamet~r and minimum wall thickness of the balloon. It is these walls in ~he cen~ral region, which may have a thickness reduced by a factor as much as 100, that dictat~
the strength o~ the balloon. Between the c~ntral region and each of the end regions of the balloon, one of the transition zone~ is characterized by a wall thickness which varies from the original thick~ess of the wall of the tube to the reduced thickness of the wall of the central region.
When these nondistensible balloon catheters are initially inserted, it is of par~icular importance that the balloon be rolled on the catheter tube to the smallest : diameter in order to provide the catheter with the lowest profile possible. The rolling of the balloon has not been a problem in the end regions. Even though end walls contain the thickest wall s~ction, they are fixed in close proximity ~o the cannula and therefore maintain a low profile even when the balloon is in~lated~ Similarly, rolling the balloon on the cannula has not been a problem in the central reqion. Even though the walls in ~his region are disposed at the highest radial distance ~rom the cannula, the very thin walls in this region are adaptable .:: ., : , :: ., , . , ,, : ,. . :
W~2~ 2 PCT/US92/~3~7 to being xolle~ into close compliance wi~h the cannula.
:: However, in the transition reglons of the balloon, both the thickness of the wall and t:he radial displacement of the ; wall tend to create a problem. Although the transition - 5 wall is thinner than ~hat in the end region, it is disposed at a ~reater radial distanGe than the end wall. And although this radial distallce is less than that of the central region, the wall thickness is greater a~d therefore more rigid than the central region.
When a nondistensible balloon of the past has been rolled onto a cannula, it has resulted in enlarged sections at each transition region, giving the rolled balloon the appearance o~ a dog bone. These enlarged transition sections typically hav~ diameters as much a~ 50~ greater than those associated with either the c~ntral section or the end section of the rolled balloon. Furthermore they tend to form sharp corners which can severely damage ~he body condu~t during ~oth in~ertion and withdrawal of the catheter..
With these deficiencles of the prior art, it is an object of the present in~ention to provide a balloon cakheter wherein the b~lloon can be ralled or otherwise compr~ssed onto the catheter ~ube to a diameter which is substantially constant along the entire length o~ the rolled balloon.
.
~0 In accordance with the present invention, a balloon cathe~er is proYided wherein th~ balloon can he rolled on the cathet:er tube to a pro~ile which is substantlally constant in diam~ter along the length of the balloon.
Further~ore, there are no sharp points associated wit~ this , W~ 92/1189~ - P~r/uss2/oo3o7 low profil~. As a re~ul~, the great~st diameter of the catheter with the balloon in its low profile state, is reduced by as much as 5G% with substantially no sharp edges to damage the body conduit.
In one aspect of the invention, a nondistensible balloon is adapted to be rolled on a cannula having an elongate axis, in order to achi~ve a low proile. The balloon comprises an end wall diiposed in an end region of the balloon and having a ~ixed circumferential relationship with the cannula. A central wall disposed in a central region of the balloon is displaced from the cannula when the balloon is inflated. A transition wall disposed between the ~nd wall and the central wall includes a height transition xegion where th~ transition wall extends from the height of the end wal} to the height of the central wall, and a thick~essi transition r~gion where the transikion wall extends from the thickne~s of the ~nd wall to the thickness of the central wall. The axial length of the thickness transition zone is less than the axial length of the height transition zone.
In another aspect o~ the invention, a method for making a nondistensible balloon characterized by an end wall, central wall and ~ran~iition w~11, includes the fi~ep of providing a blow ~old having an end wall surface, a central wall surface and a transition wall surface equivalent to the external shape desired ~or the respective end wall, ce~tral wall and transition wall when the balloon is inflated. The method further comprises the steps o~
inserting a tube of material into the mold and blow molding the material of the tube ag~inist the surface o~ the mold.
Finally, thP process calls for reducing the quantity of material per unit length in the transition wall to an amount less than the average volume of material per unit ~ .
' ' . : .. , ' .
W~92~ 92 - P~/U592/~307 ~lUUlj91 length in ~i~her ~he end wall or ~the central wall of the . balloon.
In other aspects of the invention, the traditional S blow molding method is alte!red by pro-~iding the tu~e of material with a reduced wall thickness in those areas which correspond to the transition reqions of the balloon. This automatically reduces thP guanttty of ~at~rial and hence - the thickness of the transition walls.
In another method, a balloon formed in accordance with the prior art is inserted into a funnel or mold which is configured to receive at least the transition wall of the balloon. This second mold is heated to increase the flexibility of ~he balloon in the tra~sition region, and the balloon is str~tched axially to thin the heated wall.
In still a ~urther method, th~ blow mold is formed with recPs~es in the transition surface. In such a mold, the balloon is for~ed with projections in the transition reglon, which increase the surface area and therefore decrease the thickness of the transition walls.
These and other features and adva~tages of the in~ention will be more apparent with a description of preferred embodiments and referPnce to the associated drawings.
:
' ' ' : , ' ' . ' ~ ~ `, ', ' , ' ~ ' W~9~/11892 - PC~/US92/~307 .
Fig. 1 is an axial cross-ssctisn view of one embodiment of a balloon cathet:er o~ the present invention, showing the catheter operat:ively disposed in a body conduit;
Fig. 2 is an axial cross-section view o~ a balloon associated with the prior ~rt rolled onto a cannula and illustrating the dog bone profile associa~ed with the prior art;
Fig. 3 is an axial cross-section ~iew illustrating the low profile, rolled characteristics a~ociated with the balloo~ of Fig. l;
Fig. 4 illustra~es a top plan view of a blow mold used in the prior art method for making the balloon illustrated in Fig. 2;
: Fig. 4a is an axial cross-section view of blow mold ~ tubing used in the prior art method;
- Fig. 4b is an axial cross-section view o f the tubing of Fig. 4a being heated in the prior art process;
Fig. 4c is an axial cro~s-~ection view o~ the tubing o~ Fig. 4 coaxially disposed in the mold of Fig. 4;
30: Fig. 4d illu~trates the blow molding step in the process of the prior art;
Fig. 5 i.s an enlarged axial cross-sec~ion view of one quadrant o~ the balloon of the prior art illustrated in an inflated sta1:e;
W~92/~9~ ~ P~T/U~2/~3~7 ~1~lj091 Fig. 5a is a cross-sec~ional view taken alony lines 5a-5a of Fig. 5;
FigO Sb is an axial c:ross-sacti4n view taken along lines 5b 5b of Fig. S;
Fig. 5c is an axial cross-section view taken along lines 5c-5c of Fig. 5;
Fig. 6 is an axial cross-section view of one quadrant of the balloon of Fig. 1 illustrated in an inflated state;
Fig. 6a is a cross-sectional view taken along lines :
6a-6a of Fig. 6;
~5 Fig. 6b is an axial cross~s~ction viaw taken ~long lines 6b-6b o~ Fig. 6;
Fig. 6c is an axial cross~-section view taken along lines 6C-6C Gf Fig 6;
Fig. 7 is an axial cross-section ~iew ~imilar to Fig.
6 of a further embodiment of the balloon associated with the present inventiQn;
Fig. 7a is a cross-sectional view taken along linas 7a-7a of Fig 7;
Fig. '7b is an axial cross~section view taken along lines 7b-7b of Fig. 7;
Fig. 7c is an axial cross-section view tak@n ~long lines 7c-7c of Fig~ 7; .;
W~2/~l~s2 ~ PCT/US92/~;
~UI~l~9~
:Fig. 8 is an axial cross-section vi~w of bump tubing used in a method o~ the present inv2ntio~;
Fig. 8a is an axial cross-section Yiew of the bump tubing ~f Fi~. 8 inserted in ~ conventional blow ~old associated with the present invention;
Fig. 8b is an axial cross-s~ction view showing the molded balloon with a ~ran~ition wall of su~stantially constant thickness;
Fig. 9 is an axial cross-section view of a second mold or funnel associated with a urther method of the present invention;
Fig. 9a illustrate~ a balloon dispo~ed in the funnel of Fig. 9, heated, and stretched in the transition region to form a transition wall o~ reduced thickness;
20Fig. 10 is a top plan view of a blow mold associated with a fuxther method of the present inv~ntion;
Fig. lOa is an axial cross~section view of the balloon disposed in the mold o Fig. 10, heated, and axially stretch~d in the tran ition region~ to provide a transition wall of reduced thickne~s;
Fig. 11 i~ a top plan view o a mold associated with a further method of the present invention;
Fig. 12 is an axial cross-section view of a conventional b~alloon with a sle~ve bonded to the central regions o~ the balloon; and W~92/11~9~ - PCT/US~2/~307 0 '~ 1 1~
Fig. 13 is an axial cross-section view of two balloon portions wherein central rlegions of each balloon portion are overlapping and bonded t:o increase the thickness of the central wall of the balloon.
Description oP Preferred Embodlments lOA dilatation catheter is illustrated generally in Figure l and designated hy the reference numeral lO. The :
catheter lO is operatively disposed in a body conduit de~ined ~y walls ll, and includes an elongate cannula 12 having a distal end 14 and a proximal end (not shown~.
The catheter lO also includes a balloon 16 having a distal end wall 18 and a proxi~al end wall 21 dispssed in respective end regions 23 and 25 of the balloon 16.
central wall 27 is disposed between the end walls 18 and 2l in a central region 30 of the balloon l6.
In thls particul~r embodiment the end walls 18 and 2l are .relatively thicX and relatively small in diameter.
This is in compari~on to ~he central wall 27 of the balloon 16 which is relatively thin and relatively large in diamet~r.
'~
A pai.r of transition walls 32 and 34, each having a generally conical configuration, are o~ particular interest to the present invention. The transition wall ~2 is disposed in a proximal transition region 36 between the end region 25 and the central region 30. The transition wall 34 is disposed in a di~tal transitio~ regio~ 38 between the end region 23 and the ~ntral region 30 of the balloon.
:.
". . .. , . . ~ i ; ... , : : . ~ . . . . . . . .
WO92t11892 - PCT/US92/~307 Two separate ~ran~itions occur to th~ walls 32, 34 in each of the transi~ion regions ~6, 38. First, the walls 32, 34 are each characterized by a transition in height from the height of the respective end walls 18, 21 to the height of the central wall 27. This transition region will be referred to as the height tranrition region 4l. Second, in the transition regions 36, 38 the walls 32, 3~
respectively, undergo a transition from their greatest thickn~ss in proximity to the end region 25, 23 respectively, to their least thickness in proximity to the central region 30. This transition region is referred to as the thickness transition region 43. It is the relative axial length of the two regions of transition, the height transition region 41 and the thickness transition 431 which are of particular interes~ in this ca~.
I~ accordance witn the present invention, the thickness transition region 43 has a shorter axial dimension than does the height ~ransition region 41. This occurs because the thickness of the end wall 21 thins to a dimension generally equiYalent to the thickness o~ the central wall 27 over a relatively ~hort distance along the transition wall 32. It is particularly desirable that this thickness transition region 43 be positioned in close proximity to the end wall 21 so that a~y substantial wall thickness associated with the region 43 is closely spaced to the outer surface of the ca~nula 12.
As will be discus~ed in greater detail below, the balloons of the prior art have a thickness transition region 43 which i5 generally equivalent in axial length to the height transition region 4l. In other words, the thickness of the transition wall 32 gradually decreases over the entire axial distance between the end region 25 and the central r~gion 30. While this does not adversely ,.
W~92/~1~92 - P~/U~92~307 ~ l U ~ d ~ l affect the balloon in its infla~ed, high profile state, it has a dramatic af~ec~ on the rolled, low profile state of the balloon as illustrated ln Figure 2. With the relative thickness of the transition wall spaced even a short radlal distance ~rom the cannula 12, the balloon 10 in its rolled confi~uration tends to have an undesirable dog bone shape.
. Thus in the low profile state, in the low profile state, enlargements occur at both o~ the transition regions 36 and 38 with the halloon of the prior artO It is in these regions that the respective walls 32 and 34 are too thi~k and too far displaced from the cannula 12 to adequately ~omply to the cannula in the rolled state.
~y thinning the walls 32 and 34 of the transition 15 regions 36, ~8 respectively, the walls of the balloon 16 are either thick in proximity to the cannula 12 or thin at any substantial xadial distance from th~ cannula 12. It is in this manner that the balloon of Figure 1 in the rolled ..
configuration achieves a low profile state as illustrated in Figure 3.
An understanding of the wall thickness associated with the transition zones 36, 38 and its effect on the rolled configuration of the balloon 10 will be better understood with re~erenc~ to a typical blow molding process used to manufacture the balloon o~ the prior art. Figure 4 and Figures 4a-4d illustrate steps ih a hlow molding process of the prior art; however, some of these steps also apply to the ~ethods associa~ed with the present invenkion.
In the plan view o~ Figure 4, a blow mold 50 is illustrated with an in~er mold surface 52 which defines ~ .
ca~ity 54 having the shape desired for the external surface of the bal.loon 16. Thus tha surface 52 includes end :
35 sur~ac~s.56, 58 which correspond to the end regions 23, 25 ~, ,; .
' ., : . . . ~ . . . ~ . . . . . . .. .. ..
W~92/11892 - PCr/US~/~307 respectively, a central sur~ace 61 which corresponds to the cen~ral region 30, and transition surfaces 63, 65 which correspond to the transition ret~ion~ 36, 38 respectively.
In accordance with this process of the prior art, matexial is provided in the for:m o~ a tube 67 which has a generally cylindrical con~iguration and a relatively constant wall thickness as illustrated irl Figure 4a. The tube 67 is heated, for example in a conventional ~ven 69, to provide the tube 67 with a generally limp, pliable conf iguration . In this state, the tube 67 is inserted into the mold 50 and stretched axially as shown by the arrows 70 in Figure ~c. This axial s~retching tends to align the tube 67 coaxially with the cavity 54 of the mold 50.
At this point in the process, one end o~ the tube 67 is ~ealad by a cla~p shown generally at 72 in Figure 4d~
The other end of the tube 67 is in~lated by a fluid, such as air, provided by a compressor 74. This air is blown into the heated tube G7 stretching the walls of the tube 67 until they contact the surface 52 of the mold 50. Upon contact, the walls of the balloon 16 are cooled by the mold 50 and ~rozen in their expanded state.
It will be apparen~ with referenc~ to Figure 4d that the volume of material per unit length provide by the tube 67 will also be equivalent to the ~olume o~ material per unit leng~h o~ the walls fo~ming ~he balloon 16. Where ~he central wall 27 is greatly spaced from the axis of the ~alloon, this constant volume will necessarily require a reIatively thin central wall 27. Where th~re is substantially no radial displaoement of th~ tube 67, for exampIe in the end region 23, 25 the thickn~ss of the respective end walls 18, 21 will be substantially th~ same as the thickness as the wall~ of the tube 67. Along the WO g2~ 92 Pcr/uss~/~307 .~4 transition walls 32, 3~, the resul~ achieved with the formation of the end wall~ 18, 21 ~iYes way to the result achieved with the formation of the central wall 27. Thus the greater the radial displacement of the walls of the tube 67, the less the thickness of the resultiny ~all of the balloon 16.
In a ~urther description of the invention, ~ocus will be dira¢ted primarily to the transition region 36 lo illustrated in the upper left hand corner o~ the balloon 16 in Figure 1. However, the comments will apply equally as .~-well to the quadrant o~ the balloon 16 in the lower left hand corner of Figure 1~ Comments ~ay also apply to transition region 38 illustrated on the right hand side of 15 the balloon 16 of Figure 1. -.
ThP transition region, ~uch as the region 36, is illustrated for a balloon o~ the prior art in the enlarged ~:
YieW of Figure 5. In this view it i~ apparent that the thickness transition zone 43 is substantially equival~nt in axial dimen~ion to the thlckness transition zone 41.
Because there is substantial thickness o~ the wall 32 in the transition zone 36 at substantial radial dimensions from the cannula 12, the balloon 16 in the rolled configuration has the dos bone pro~ile illustrated in Figure 2. The thickn~ss of the walls 21, 32 and ~7 is measur~d and discus~ad with respect to their dimen~ion in a radial plane as illustrated by the thickness "t" in Figure 5. ~.
As long as the ~olume of material p~r unit axial length remains constant along th~ walls of the balloon 16, as is the case with the balloons o~ ~he prior art, a relation~hip carl be establi~h~d based on the thickness "t"
35 at any two locations along th~ balloon walls~ Figures sa, --, . , , ., , , .......... .. ~ , , ~ . .................... :
. , . ~: , . .......... . . . .
. .
WO~2/11892 P~T/U~2/~307 5b and 5c show radial cros~/se!ctions of the prior art balloon in Figure 5 taken along ~he lines 5a, 5b and 5c respectively. Re~erring to Figure 5h, th~ transition wal7 32 has a thickness t, at a point "l" in Figure 5. This thickness t~ is equivalent to the differ~nce between the inner radius r~ and the outer radius R~ of the wall 32.
Similarly in Figure 5c, the wall of the balloon 16 has a thickness t2 at a point "2" between the central region 30 and the transi~ion region 36. This thickness t2 is equivalent to the difference between the inner radius r2 and the outer radius R2 f the wall 32. If the volume per unit length of material in the walls 21, 32 and 27 is equivalent, as is the case with th~ balloons of the prior art, then the shaded ar~as in Figures 5b and 5c will be equivalent in size. It follows that the thicknPss of the wall at any point, such as the point l, can be determined given the radii rl and Rl at point l, the thicXness at any point 2 and the associated radii r2 and ~ at point 2. It follows that this relationship is establishPd by the following Formula I:
'Cl = t2 ( ~ R~ ) This relationship has existed in the prior art and has yiven rise to the noncompliant, dog bone shape of the balloon 16 in its low profile configuration as illustrated in Fi.gure 2. In accordance with the present invention, the thickness tl will be given by the following Formula II:
- - - . . . . . . . : . . .
. .
W~92~1~892 - PCT/~92/~3~7 t1 < ~2(r2 + R~) This is illustrated in the embodiment of Figure 6 where the thickness t~ at t'he point 1 is substantially equivalent to the thickne~s t2 at the point 2. The conditions of Formula II will be met since the sum of r~ +
R~ is 1Q~S than the sum of r2 ~ Rto This can be appreciated by merely noticing that the ~haded area in Figure 6b has a smaller area than do s the shaded area in Figure 6c.
In particular embodiments of the invent.ion, it is desirable that the axial l~n~th of the thickness transition region 43 be maintained a~ less than on~-hal~ the axial length o~ t~e height transition region 41. ~n the most pre~erred embodim~nt, the full transitlon in thickness from the ~hickest wall ~1 ~o the ~hinnest wall 27 occurs within only one-fourth of the axial di~tance along the height transition region 41. Of course, the maximum advantage is ~ .
achieved where the wall ~2 is consistently thin throughout ,' the entire height transition reqion 41. And in an ideal case, the end wall 21, the transition wall 32, and central wall 27 alI have the same thinness. Even in this case the stre~gth of the balloon is still d~termined by the thickness of the central wall 27.
.
This r~.duced wall thickness of the transition region 36 can be provided in an embodiment where the walls 32 are provided with an increa~ed area so that they are automatically thinned due to the scarcity o~ the ~aterial. :
In the embodiment o~ Fi~ure 7, the increase~ area in t~e transition region 36 is provided in the ~orm of projections 81. By adding these projections 81, the area of the balloon in the region 36 is increased ~o that the thicknes~
.
i, .'.' : ; ' ' ` ' ' ' ~ .
,' ;. '' ,, ', '',,, ".' ., ,. :' ~,' ' ', '' ' ' ' , ' ., ' :` ',, ' W~92/1189~ - PCT/U59~/W307 of the wall 32 is sub~tan~ially ~quivalent to the wall 27.
In such an embodiment, the thin walls in the transition region 36 are as compliant as the walls 27 in the central region 30. This facilitates rol:Ling the balloon into a low profile sta~e as illustrated in Figure 3.
The ~alloons of the present invention also can be made in accordance with a preferred method ~hown by the ~ eps illustrated in Figures 8-8b. Thus the process of Figure 4 can be revised in the step illustrated in Figure 4a by providing the tube 67 in a configuration illustrated in Figure 8. In this case, the tube 67 has walls o~ generally constant thicXness in ~ pair of end zones 90 and 92 which are associated with the end r~gione 23 and 25 respectively o~ the balloon 16. The wall of the tube 67 has a greater cross sectional area in a central zone 94 which is associated with the central region 30 o~ the balloon 16.
Between each o~ the zo~es 90, 92 and the central zone 94, a pair of transition zones 96, 98 respectively, are ~ 20 provided which supply the matarial associated with the transition regions 36 and 38 of the balloon 16.
The walls of the tube 67 in the transition zones 96, 98 have reduced cros~-sectional area relative to the walls in the cen~ral zone ~4. When the tube o~ Figure 8 is inserted into the mold 50 as illustrated in Figure 8a, the reduced material availa~le in the transition zones 96, 98 automatically produces a balloon 16 with transition regions 36, 38 of reduced thickness. In this manner, the balloon o~ Figure 1 can be produced in accordance with the method steps illustrat:ed in Figures 8 - 8b.
Referring to Figures 9 and ga, it will be apparent that all of the steps associated with Figures 4-4d which produce the prior art balloon of Figure 5, are equally W092/~892 . ~CT/US~2/~307 0 9 ~
applicable to an improved pro~ess wherein a second mold is provided in the shape of a fllnnel 101. The funnel 101 can be formed ~rom stainless st~el or other suitable material and surrounded by induction coils 103. An inner surface 105 of the funnel 101 is provid~d wi~h the shape desired for the exterior surface of t:he balloon 16 particularly in the transition region 36.
In this extended process the induction coils 103 can be energized by a signal from a radiofrequency generator 107. This radiofrequency energy is induc~ively coupled to the Punnel 101 to heat the interior surface 105. Inserting the balloon 16 of the prior art into the funnel 101, as illustrated in Figure 9, heats the transition zone 36. ,:~
When axial tension is applied to the end wall 21 o~ ~he balloon 16, as illu~trated by the arrow 109, th2 hPated transition wall thin~ to the reduced thickness illustrated in Figure 6.
In a similar method illustrated in Figures 10 and lOa, the mold 50 is provided with a pair of end sections llo and 112, a ce~tral section 114, and a pair of transition .:
sections 116 and 118. In this case, the material forming the transition ~ections 116, 118 and the end sections 110 and 112, is preferably heatconductiYe, such as metallic, while the material forming the central section 114, is preferably non-heakconductlve such as pla~tic.
With the. balloon 16 disposed in the mold 50, the entire mold can be heated by a heater 119 to inGrease the temperature O:e the metallic sections 116, 118, 110 and 112~
The plastic s~ction 114, however, will not easily transmit the h~at ~o the cP~tral regi4n 30 of the balloon 16 remains relatively cool. By axially stretching the balloon 16 under these conditions, the heated material in the .. . . . . . .
WQ 9~/11892 PCr/~S92/00~07 transition regions 36, 3~ and ~he end re~ions 110, 112 will be thinned to provide ~he balloon 16 with the configuration illustrated in Figure 8b.
In still a further method of the present invention the mold 50 illustrat~d in Figur-e 4 can be modified by providing recesses 125 in the transition sur~aces 63 and 65. Usiny the remainder of the steps illustrated in Figures 4a-4d will produce a balloon 16 having the configuration illustrated in Figure 7. With the reduced wall thickness provided by ~he projections 81, the balloon 16 can be rolled to a low profile state as illustrated in Figure 3.
As previously discussed, ~he strength of the ~alloon 16 is dictated primarily by the wall thickne~s in the centr l region 39 while the problems a~sociated with the low profile are dictated primarily by the wall thickness in the transition zones 36, ~8. The prior art has not been able to d~velop reduced wall thicknesses in the transition zones 36 and 38 which are ~uffiGiently thin to avoid the dog bone effect without sacrificing strength in the central - region 30.
2 5 Xn order to reduce wall thickn Rses in the transition regions of the prior art, it has required that the wall thickne~ses in the central region 30 also be reduced below the thick~ess required f or minimum strength. However, it will noW be possible in accordanc~ with the concept of the present in~ention to ~orm just suCh a ~alloon with reduced wall thicknesses in ~he ~ransition regions 36 and 38, and then to reinforce th~ central region 30, for example with a sl~eve 13V as illustrated in Figure 12. Bonding the sleeve 130 onto the central wall 27 will incr2ase the strength o~ this critical central region 30 without W092/11~92 P~r/VS92/~3~7 otherwise increasing ~he ~hic~ness o~ the walls in the transitlon regions 36 and 3~.
It is also within the scope of the present invention S to provide two separate wal.l sections each formed in accorda~ce with the method of Figure 4. For example, in Figure 13, a wall section 136 :i5 illustrated to include the end wall 21, the transition wall 32 and a central wall 27a.
Simllarly, a second balloon SQCtion 138 includes the end wall 18, the transition wall 34 and a central wall 27b.
The central wall 27b can be inserted into the central wall 27a and bonded in this position. The resulting wall in the central region 30 will have a double, reinforced thickness without increasing the thickness o~ the transition walls 32 or 34.
Although the inventio~ has been described with reference to preferred embodiments and methods, it will be apparent that th~ balloon and catheter a~sociated with the present invention can b2 otherwise embodied and manufactured. For example, in all of the foregoing examples requiring a blow mold, the mold can be entirely eliminated in which case the balloon is free formed. In the ~bsence of a mold, control over the ultimate ~hape of the balloon is somewhat restricted. Nevertheless, the concepts disclos~d herein for reducing the wall thicknesses particularly in the transition region of the balloon are equally applicable. Due ko these variations in the concept, one should not refer merely to the drawings or the particular e~bodiments di~cussed. Rather, the scope o~ the invention should be ascertained only with reference to the following claims.
It is also within the scope of the present invention S to provide two separate wal.l sections each formed in accorda~ce with the method of Figure 4. For example, in Figure 13, a wall section 136 :i5 illustrated to include the end wall 21, the transition wall 32 and a central wall 27a.
Simllarly, a second balloon SQCtion 138 includes the end wall 18, the transition wall 34 and a central wall 27b.
The central wall 27b can be inserted into the central wall 27a and bonded in this position. The resulting wall in the central region 30 will have a double, reinforced thickness without increasing the thickness o~ the transition walls 32 or 34.
Although the inventio~ has been described with reference to preferred embodiments and methods, it will be apparent that th~ balloon and catheter a~sociated with the present invention can b2 otherwise embodied and manufactured. For example, in all of the foregoing examples requiring a blow mold, the mold can be entirely eliminated in which case the balloon is free formed. In the ~bsence of a mold, control over the ultimate ~hape of the balloon is somewhat restricted. Nevertheless, the concepts disclos~d herein for reducing the wall thicknesses particularly in the transition region of the balloon are equally applicable. Due ko these variations in the concept, one should not refer merely to the drawings or the particular e~bodiments di~cussed. Rather, the scope o~ the invention should be ascertained only with reference to the following claims.
Claims (24)
1. A non-distensible balloon adapted to be disposed circumferentially on a tube having an elongate axis, and adapted to be rolled on the tube to achieve a low profile, the balloon comprising:
an end wall disposed in an end region of the balloon and in a fixed circumferential relationship With the tube;
a central wall disposed in a central region of the balloon and in a displaced relationship with the tube when the balloon is inflated;
a transition wall disposed between the end wall and the central wall of the balloon;
first portions of the balloon disposed in the transition wall and having a thickness t1, an inside radius R1, and an outside radius R1;
second portions of the balloon disposed in one of the end wall, central wall and the transition wall, and having a thickness t2, an inside radius r2 and an outside radius R2;
and the thickness t1 of the first portions of the balloon are characterized by the following formula:
an end wall disposed in an end region of the balloon and in a fixed circumferential relationship With the tube;
a central wall disposed in a central region of the balloon and in a displaced relationship with the tube when the balloon is inflated;
a transition wall disposed between the end wall and the central wall of the balloon;
first portions of the balloon disposed in the transition wall and having a thickness t1, an inside radius R1, and an outside radius R1;
second portions of the balloon disposed in one of the end wall, central wall and the transition wall, and having a thickness t2, an inside radius r2 and an outside radius R2;
and the thickness t1 of the first portions of the balloon are characterized by the following formula:
2. The non-distensible balloon recited in Claim wherein:
the transition wall extends from the end wall to the central wall and defines a height transition region wherein the transition wall extends from a first radius at the end wall to a second radius at the central wall, the height transition region having a first axial length; and the transition wall defining a thickness transition region wherein the transition wall varies from a maximum thickness to a minimum thickness, the thickness transition region having a second axial length less than the first axial length.
the transition wall extends from the end wall to the central wall and defines a height transition region wherein the transition wall extends from a first radius at the end wall to a second radius at the central wall, the height transition region having a first axial length; and the transition wall defining a thickness transition region wherein the transition wall varies from a maximum thickness to a minimum thickness, the thickness transition region having a second axial length less than the first axial length.
3. The non-distensible balloon recited in Claim 2 wherein the second axial length of the thickness transition region is less than one half the first axial length of the height transition region.
4. The non-distensible balloon recited in Claim 2 wherein the thickness of the transition wall is constant between two different locations along the height transition region.
5. The non-distensible balloon recited in Claim 1 wherein the entire thickness transition region is disposed within an axial distance from the end zone equal to one half the axial length of the height transition region.
6. The non-distensible balloon recited in Claim 1 wherein the thickness t1 of the first portions of the balloon is characterized by the following formula:
7. A method for making a non-distensible, inflatable balloon characterized by an end wall disposed in an end region of the balloon, a central wall disposed in a central region of the balloon, and a transition wall disposed between the end wall and the central wall, the method comprising the steps of:
providing a blow mold having an end wall surface, a central wall surface, and a transition wall surface equivalent in shape to the external shape desired for the respective end wall, central wall and transition wall of the balloon when the balloon is inflated;
inserting an elongate tube of material into the mold;
blow molding the material of the tube against the surface of the mold; and reducing the average volume of material per unit axial length in the transition wall of the balloon to an amount less than the average volume of material per unit axial length in one of the end wall and central wall of the balloon.
providing a blow mold having an end wall surface, a central wall surface, and a transition wall surface equivalent in shape to the external shape desired for the respective end wall, central wall and transition wall of the balloon when the balloon is inflated;
inserting an elongate tube of material into the mold;
blow molding the material of the tube against the surface of the mold; and reducing the average volume of material per unit axial length in the transition wall of the balloon to an amount less than the average volume of material per unit axial length in one of the end wall and central wall of the balloon.
8. The method recited in Claim 7 wherein:
prior to the inserting step the tube of material is characterized by an end zone providing the material to form the end wall of the balloon, a central zone providing the material to form the central wall of the balloon, and a transition zone providing the material to form the transition wall of the balloon; and during the reducing step the method further comprises the step of limiting the volume of the material per unit axial length in the transition zone of the tube to an amount less than the volume of material per unit axial length in the one wall of the balloon.
prior to the inserting step the tube of material is characterized by an end zone providing the material to form the end wall of the balloon, a central zone providing the material to form the central wall of the balloon, and a transition zone providing the material to form the transition wall of the balloon; and during the reducing step the method further comprises the step of limiting the volume of the material per unit axial length in the transition zone of the tube to an amount less than the volume of material per unit axial length in the one wall of the balloon.
9. The method recited in Claim 8 wherein prior to the inserting step the tube of material is provided with a cylindrical wall having a first thickness in the end zone, a second thickness in the transition zone, and a third thickness in the central zone, and the second thickness is less than at least the third thickness.
10. The method recited in Claim 8 wherein during the blow molding step the method further comprises the steps of:
heating the tube of material; and blowing a fluid into the tube against the surface of the blow mold.
heating the tube of material; and blowing a fluid into the tube against the surface of the blow mold.
11. The method recited in Claim 10 wherein during the reducing step the method further comprises the steps of:
increasing the temperature of the material in the transition zone relative to the temperature of the material in one of the end region and the central zone; and axially stretching the tube to thin the transition wall of the balloon.
increasing the temperature of the material in the transition zone relative to the temperature of the material in one of the end region and the central zone; and axially stretching the tube to thin the transition wall of the balloon.
12. The method recited in Claim 11 wherein during the increasing step the method further comprises the step of cooling the central wall of the balloon.
13. The method recited in Claim 11 wherein during the increasing step the method further comprises the step of heating the transition wall of the balloon.
14. The method recited in Claim 11 wherein during the providing step the blow mold is characterized by a central wall formed of a non-heatconductive material and a transition wall formed of a heatconductive material, and the increasing step includes the step of heating the mold to increase the temperature of the transition wall relative to the central wall of the mold.
15. A method for making a non distensible balloon having a first wall characterized by a relatively small diameter, a second wall characterized by a relatively large diameter, and a third wall disposed between the first wall and the second wall, the method comprising the steps of:
providing a blow mold having an inner surface;
inserting into the mold an elongate tube having a first zone associated with the first wall, a second zone associated with the second wall, and a third zone associated with the third wall of the balloon;
blowing a fluid into the tube to expand at least the second zone of the tube against the inner surface of the mold;
heating the third wall of the balloon; and stretching the third wall of the balloon axially to reduce the thickness of the third wall of the balloon.
providing a blow mold having an inner surface;
inserting into the mold an elongate tube having a first zone associated with the first wall, a second zone associated with the second wall, and a third zone associated with the third wall of the balloon;
blowing a fluid into the tube to expand at least the second zone of the tube against the inner surface of the mold;
heating the third wall of the balloon; and stretching the third wall of the balloon axially to reduce the thickness of the third wall of the balloon.
16. The method recited in Claim 15 wherein during the heating step the method further comprises the steps of:
providing a second mold with an inner surface;
inserting at least the third wall of the balloon into the second mold; and heating the second mold in order to heat the third wall of the balloon.
providing a second mold with an inner surface;
inserting at least the third wall of the balloon into the second mold; and heating the second mold in order to heat the third wall of the balloon.
17. The method recite in Claim 16 wherein the step of heating the second mold further comprises the step of applying radiofrequency energy to the second mold to heat the second mold.
18. The method for thinning the wall of a balloon, comprising the steps of:
providing a non-distensible balloon having an elongate axis and characterized by a first relatively thick wall, a second relatively thin wall and a third wall disposed between the first and the second wall, the first wall, second wall and third wall having substantially the same volume of material per unit axial length of the balloon;
and increasing the average volume of material per unit axial length of the second wall relative to the third wall of the balloon.
providing a non-distensible balloon having an elongate axis and characterized by a first relatively thick wall, a second relatively thin wall and a third wall disposed between the first and the second wall, the first wall, second wall and third wall having substantially the same volume of material per unit axial length of the balloon;
and increasing the average volume of material per unit axial length of the second wall relative to the third wall of the balloon.
19. The method recited in Claim 18 wherein:
the providing step includes the steps of providing a first balloon section including one of the first wall, second wall and third wall, and providing a second balloon section including one of the first wall, second wall and third wall; and the increasing step includes the steps of inserting the second wall of the first balloon section into the second wall of the second balloon section, and bonding the second wall of the first balloon section to the second wall of the second balloon section.
the providing step includes the steps of providing a first balloon section including one of the first wall, second wall and third wall, and providing a second balloon section including one of the first wall, second wall and third wall; and the increasing step includes the steps of inserting the second wall of the first balloon section into the second wall of the second balloon section, and bonding the second wall of the first balloon section to the second wall of the second balloon section.
20. The method recited in Claim 18 wherein the increasing step further comprises the steps of:
providing a sleeve of wall material;
inserting the sleeve over the second wall of the balloon; and bonding the sleeve of the material to the second wall of the balloon to increase the volume of material per unit axial length of the second wall relative to the third wall of the balloon.
providing a sleeve of wall material;
inserting the sleeve over the second wall of the balloon; and bonding the sleeve of the material to the second wall of the balloon to increase the volume of material per unit axial length of the second wall relative to the third wall of the balloon.
21. The method of Claim 18 wherein the increasing step includes the step of reducing the average volume of material per unit axial length of the third wall relative to the second wall of the balloon.
22. A method for making a non-distensible balloon having a first wall characterized by a relatively small diameter, a second wall characterized by a relatively large diameter, and a third wall disposed between the first wall and the second wall, the method comprising the steps of:
providing an elongate tube having a first zone associated with the first wall, second zone associated with the second wall and a third zone associated with the third wall of the balloon;
blowing a fluid into the tube to expand at least the second zone of the tube;
heating the third wall of the balloon; and stretching the third wall of the balloon axially to reduce the thickness of the third wall of the balloon.
providing an elongate tube having a first zone associated with the first wall, second zone associated with the second wall and a third zone associated with the third wall of the balloon;
blowing a fluid into the tube to expand at least the second zone of the tube;
heating the third wall of the balloon; and stretching the third wall of the balloon axially to reduce the thickness of the third wall of the balloon.
23. The method recited in Claim 22 wherein during the heating step, the method further comprises the step of heating the first wall of the balloon.
24. The method recited in Claim 23 wherein during the stretching step, the method further comprises the step of stretching the first wall of the balloon axially to reduce the thickness of the first wall of the balloon.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US639,672 | 1991-01-08 | ||
| US07/639,672 US5254091A (en) | 1991-01-08 | 1991-01-08 | Low profile balloon catheter and method for making same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2100091A1 true CA2100091A1 (en) | 1992-07-09 |
Family
ID=24565093
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002100091A Abandoned CA2100091A1 (en) | 1991-01-08 | 1992-01-07 | Low profile balloon catheter and method for making same |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US5254091A (en) |
| EP (1) | EP0566684B1 (en) |
| JP (1) | JPH06508532A (en) |
| CA (1) | CA2100091A1 (en) |
| DE (1) | DE69220476T2 (en) |
| WO (1) | WO1992011892A1 (en) |
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| CN111182861A (en) * | 2017-10-04 | 2020-05-19 | 佐里安医疗公司 | Delivery balloon with retractable retention cuff |
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-
1991
- 1991-01-08 US US07/639,672 patent/US5254091A/en not_active Expired - Lifetime
-
1992
- 1992-01-07 JP JP4504558A patent/JPH06508532A/en active Pending
- 1992-01-07 DE DE69220476T patent/DE69220476T2/en not_active Expired - Fee Related
- 1992-01-07 EP EP92904652A patent/EP0566684B1/en not_active Expired - Lifetime
- 1992-01-07 WO PCT/US1992/000307 patent/WO1992011892A1/en active IP Right Grant
- 1992-01-07 CA CA002100091A patent/CA2100091A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111182861A (en) * | 2017-10-04 | 2020-05-19 | 佐里安医疗公司 | Delivery balloon with retractable retention cuff |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH06508532A (en) | 1994-09-29 |
| WO1992011892A1 (en) | 1992-07-23 |
| EP0566684A1 (en) | 1993-10-27 |
| DE69220476D1 (en) | 1997-07-24 |
| US5254091A (en) | 1993-10-19 |
| DE69220476T2 (en) | 1997-10-02 |
| EP0566684A4 (en) | 1994-03-23 |
| EP0566684B1 (en) | 1997-06-18 |
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