U.S. patent application number 14/024340 was filed with the patent office on 2014-01-16 for energy delivery devices and methods.
This patent application is currently assigned to Asthmatx, Inc.. The applicant listed for this patent is Asthmatx, Inc.. Invention is credited to Timothy R. DALBEC, Christopher J. DANEK, Gary S. KAPLAN, Huy PHAN, Noah WEBSTER, William J. WIZEMAN.
Application Number | 20140018789 14/024340 |
Document ID | / |
Family ID | 46326955 |
Filed Date | 2014-01-16 |
United States Patent
Application |
20140018789 |
Kind Code |
A1 |
KAPLAN; Gary S. ; et
al. |
January 16, 2014 |
ENERGY DELIVERY DEVICES AND METHODS
Abstract
A method for treating a subject includes positioning an
intraluminal device at a treatment location in an airway of the
subject, and delivering energy from an electrode of the
intraluminal device to nerve tissue extending along the airway so
as to permanently damage the nerve tissue while cooling airway
tissue disposed radially between the electrode and the nerve
tissue.
Inventors: |
KAPLAN; Gary S.; (Mountain
View, CA) ; DANEK; Christopher J.; (San Carlos,
CA) ; WIZEMAN; William J.; (Mountain View, CA)
; DALBEC; Timothy R.; (Saratoga, CA) ; WEBSTER;
Noah; (San Francisco, CA) ; PHAN; Huy; (San
Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Asthmatx, Inc. |
Sunnyvale |
CA |
US |
|
|
Assignee: |
Asthmatx, Inc.
Sunnyvale
CA
|
Family ID: |
46326955 |
Appl. No.: |
14/024340 |
Filed: |
September 11, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13860216 |
Apr 10, 2013 |
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14024340 |
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13087161 |
Apr 14, 2011 |
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13860216 |
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11618533 |
Dec 29, 2006 |
7949407 |
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13087161 |
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11256295 |
Oct 21, 2005 |
7200445 |
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11618533 |
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11420442 |
May 25, 2006 |
7853331 |
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11256295 |
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PCT/US2005/040378 |
Nov 7, 2005 |
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11420442 |
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60625256 |
Nov 5, 2004 |
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60650368 |
Feb 4, 2005 |
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Current U.S.
Class: |
606/33 ; 607/105;
607/113 |
Current CPC
Class: |
A61B 18/1492 20130101;
A61B 18/18 20130101; A61B 2018/00797 20130101; A61B 2018/1437
20130101; A61F 7/123 20130101; A61N 1/05 20130101; A61B 2018/00541
20130101; A61B 2018/00214 20130101; A61B 2018/00267 20130101 |
Class at
Publication: |
606/33 ; 607/113;
607/105 |
International
Class: |
A61B 18/18 20060101
A61B018/18 |
Claims
1. A method for treating a subject, comprising: positioning an
intraluminal device at a treatment location in an airway of the
subject; and delivering energy from an electrode of the
intraluminal device to nerve tissue extending along the airway so
as to permanently damage the nerve tissue while cooling airway
tissue disposed radially between the electrode and the nerve
tissue.
2. The method of claim 1, wherein the airway is an airway of a
lung.
3. The method of claim 1, wherein cooling airway tissue inhibits
permanent injury to the airway tissue.
4. The method of claim 3, wherein the nerve tissue extends along a
wall of the airway.
5. The method of claim 4, wherein the nerve tissue is located in
tissue outside of the airway.
6. The method of claim 3, wherein the nerve tissue is at a position
that is within at least one of the left and right lung of the
subject.
7. The method of claim 3, wherein permanently damaging the nerve
tissue includes destroying nerve tissue to inhibit the passage of
nerve signals sufficiently to reduce airway resistance in an airway
distal to the treatment location.
8. The method of claim 3, wherein the cooling step includes
protecting an inner surface of a wall of the airway from permanent
injury.
9. The method of claim 3, wherein the treatment location is in an
airway other than a first generation airway of the subject.
10. The method of claim 9, wherein delivering energy from the
electrode of the intraluminal device at the treatment location
treats multiple generations of airways within the right lung or the
left lung of the subject.
11. The method of claim 10, wherein delivering energy from the
electrode of the intraluminal device at the treatment location
treats airway generations 2-8 within the right lung or the left
lung of the subject.
12. A method for decreasing resistance to airflow within a
bronchial tree of a subject, the method comprising: moving an
intraluminal device along a lumen of an airway of a bronchial tree,
the intraluminal device comprising an expandable member and an
energy emitter; and damaging nerves along the airway using the
intraluminal device without irreversibly damaging an inner surface
of an airway wall disposed radially between the intraluminal device
and the nerves, wherein damaging nerves along the airway comprises
applying energy to nerve tissue along the airway wall using the
energy emitter while cooling airway tissue at the inner surface of
the airway wall.
13. The method of claim 12, wherein the airway tissue is cooled by
receiving a cooling fluid through the intraluminal device.
14. The method of claim 13, wherein the expandable member is an
inflatable balloon and the airway tissue is cooled by receiving the
cooling fluid into the balloon.
15. The method of claim 14, wherein receiving the cooling fluid
into the balloon includes introducing the cooling fluid into the
balloon through an opening.
16. The method of claim 15, wherein the opening is located at a
distal end of an inflow line.
17. The method of claim 16, wherein the opening is located at an
end of the balloon.
18. The method of claim 14, wherein receiving the cooling fluid
into the balloon inflates the balloon.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/860,216, filed Apr. 10, 2013, which is a
continuation of U.S. patent application Ser. No. 13/087,161, filed
Apr. 14, 2011 (now abandoned), which is a continuation of U.S.
patent application Ser. No. 11/618,533, filed Dec. 29, 2006 (now
U.S. Pat. No. 7,949,407), which is a continuation-in-part of U.S.
patent application Ser. No. 11/256,295, filed Oct. 21, 2005 (now
U.S. Pat. No. 7,200,445) and U.S. patent application Ser. No.
11/420,442, filed May 25, 2006 (now U.S. Pat. No. 7,853,331), which
is a continuation of PCT Application No. PCT/US2005/040378, filed
Nov. 7, 2005, which claims the benefit of U.S. Provisional Patent
Application Nos. 60/625,256, filed Nov. 5, 2004, and 60/650,368,
filed Feb. 4, 2005, the full disclosures of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] Asthma is a disease in which (i) bronchoconstriction, (ii)
excessive mucus production, and (iii) inflammation and swelling of
airways occur, causing widespread but variable airflow obstruction
thereby making it difficult for the asthma sufferer to breathe.
Asthma is a chronic disorder, primarily characterized by persistent
airway inflammation. However, asthma is further characterized by
acute episodes of additional airway narrowing via contraction of
hyper-responsive airway smooth muscle.
[0003] Asthma is managed pharmacologically by: (1) long term
control through use of anti-inflammatories and long-acting
bronchodilators and (2) short term management of acute
exacerbations through use of short-acting bronchodilators. Both of
these approaches require repeated and regular use of the prescribed
drugs. High doses of corticosteroid anti-inflammatory drugs can
have serious side effects that require careful management. In
addition, some patients are resistant to steroid treatment. The
difficulty involved in patient compliance with pharmacologic
management and the difficulty of avoiding stimulus that triggers
asthma are common barriers to successful asthma management.
[0004] Current management techniques are neither completely
successful nor free from side effects. Presently, a new treatment
for asthma is showing promise. This treatment comprises the
application of energy to the airway smooth muscle tissue.
Additional information about this treatment may be found in
commonly assigned patents and applications in U.S. Pat. Nos.
6,411,852, 6,634,363 and U.S. published application nos.
US-2005-0010270-A1 and US-2002-0091379-A1, the entirety of each of
which is incorporated by reference.
[0005] The application of energy to airway smooth muscle tissue,
when performed via insertion of a treatment device into the
bronchial passageways, requires navigation through tortuous anatomy
as well as the ability to treat a variety of sizes of bronchial
passageways. As discussed in the above referenced patents and
applications, use of an RF energy delivery device is one means of
treating smooth muscle tissue within the bronchial passageways.
[0006] FIG. 1A illustrates a bronchial tree 90. As noted herein,
devices treating areas of the lungs must have a construction that
enables navigation through the tortuous passages. As shown, the
various bronchioles 92 decrease in size and have many branches 96
as they extend into the right and left bronchi 94. Accordingly, an
efficient treatment requires devices that are able to treat airways
of varying sizes as well as function properly when repeatedly
deployed after navigating through the tortuous anatomy.
[0007] Tortuous anatomy also poses challenges when the treatment
device requires mechanical actuation of the treatment portion
(e.g., expansion of a treatment element at a remote site). In
particular, attempting to actuate a member may be difficult in view
of the fact that the force applied at the operator's hand-piece
must translate to the distal end of the device. The strain on the
operator is further intensified given that the operator must
actuate the distal end of the device many times to treat various
portions of the anatomy. When a typical device is contorted after
being advanced to a remote site in the lungs, the resistance within
the device may be amplified given that internal components are
forced together.
[0008] It is also noted that the friction of polymers is different
from that of metals. Most polymers are viscoelastic and deform to a
greater degree under load than metals. Accordingly, when energy or
force is applied to move two polymers against each other, a
significant part of friction between the polymers is the energy
loss through inelastic hysteresis. In addition, adhesion between
polymers also plays a significant part in the friction between such
polymers.
[0009] In addition to basic considerations of navigation and site
access, there exists the matter of device orientation and tissue
contact at the treatment site. Many treatment devices make contact
or are placed in close proximity to the target tissue. Yet,
variances in the construction of the treatment device may hinder
proper alignment or orientation of the device. For example, in the
case of a device having a basket-type energy transfer element that
is deployed intralumenally, the treatment may benefit from uniform
contact of basket elements around the perimeter of the lumen.
However, in this case, design or manufacturing variances may tend
to produce a device where the angle between basket elements is not
uniform. This problem tends to be exacerbated after repeated
actuation of the device and/or navigating the device through
tortuous anatomy when the imperfections of the device become
worsened through plastic deformation of the individual components.
Experience demonstrates that once a member becomes predisposed to
splaying (i.e., not maintaining the desired angular separation from
an adjacent element), or inverting (i.e., buckling inward instead
of deploying outward), the problem is unlikely to resolve itself
without requiring attention by the operator. As a result, the
operator is forced to remove the device from the patient, make
adjustments, then restart treatment. This interruption tends to
increase the time of the treatment session.
[0010] As one example, commonly assigned U.S. Pat. No. 6,411,852,
incorporated by reference herein, describes a treatment for asthma
using devices having flexible electrode members that can be
expanded to better fill a space (e.g., the lumen of an airway.)
However, the tortuous nature of the airways was found to cause
significant bending and/or flexure of the distal end of the device.
As a result, the spacing of electrode members tended not to be
even. In some extreme cases, electrode elements could tend to
invert, where instead of expanding an electrode leg would invert
behind an opposing leg.
[0011] For many treatment devices, the distortion of the energy
transfer elements might cause variability in the treatment effect.
For example, many RF devices heat tissue based on the tissue's
resistive properties. Increasing or decreasing the surface contact
between the electrode and tissue often increases or decreases the
amount of current flowing through the tissue at the point of
contact. This directly affects the extent to which the tissue is
heated. Similar concerns may also arise with resistive heating
elements, devices used to cool the airway wall by removing heat, or
any energy transfer device. In any number of cases, variability of
the energy transfer/tissue interface causes variability in
treatment results. The consequential risks range from an
ineffective treatment to the possibility of patient injury.
[0012] Furthermore, most medical practitioners recognize the
importance of establishing acceptable contact between the transfer
element and tissue. Therefore, distortion of the transfer element
or elements increases the procedure time when the practitioner
spends an inordinate amount of time adjusting a device to
compensate for or avoid such distortion. Such action becomes
increasingly problematic in those cases where proper patient
management limits the time available for the procedure.
[0013] For example, if a patient requires an increasing amount of
medication (e.g., sedatives or anesthesia) to remain under
continued control for performance of the procedure, then a medical
practitioner may limit the procedure time rather than risk
overmedicating the patient. As a result, rather than treating the
patient continuously to complete the procedure, the practitioner
may plan to break the procedure in two or more sessions.
Subsequently, increasing the number of sessions poses additional
consequences on the part of the patient in cost, the residual
effects of any medication, adverse effects of the non-therapeutic
portion of the procedure, etc.
[0014] In view of the above, the present methods and devices
described herein provide an improved means for treating tortuous
anatomy such as the bronchial passages. It is noted that the
improvements of the present device may be beneficial for use in
other parts of the anatomy as well as the lungs.
SUMMARY OF THE INVENTION
[0015] The present invention includes devices configured to treat
the airways or other anatomical structures, and may be especially
useful in tortuous anatomy. The devices described herein are
configured to treat with uniform or predictable contact (or near
contact) between an active element and tissue. Typically, the
invention allows this result with little or no effort by a
physician. Accordingly, aspects of the invention offer increased
effectiveness and efficiency in carrying out a medical procedure.
The increases in effectiveness and efficiency may be especially
apparent in using devices having relatively longer active end
members.
[0016] In view of the above, a variation of the invention includes
a catheter for use with a power supply, the catheter comprising a
flexible elongate shaft coupled to at least one energy transfer
element that is adapted to apply energy to the body lumen. The
shaft will have a flexibility to accommodate navigation through
tortuous anatomy. The energy transfer elements are described below
and include basket type design, or other expandable designs that
permit reduction in size or profile to aid in advancing the device
to a particular treatment site and then may be expanded to properly
treat the target site. The basket type designs may be combined with
expandable balloon or other similar structures.
[0017] Variations of the device can include an elongate sheath
having a near end, a far end adapted for insertion into the body,
and having a flexibility to accommodate navigation through tortuous
anatomy, the sheath having a passageway extending therethrough, the
passageway having a lubricious layer extending from at least a
portion of the near end to the far end of the sheath. Where the
shaft is slidably located within the passageway of the sheath.
[0018] Variations of devices described herein can include a
connector for coupling the energy transfer element to the power
supply. The connector may be any type of connector commonly used in
such applications. Furthermore, the connector may include a cable
that is hard-wired to the catheter and connects to a remote power
supply. Alternatively, the connector may be an interface that
connects to a cable from the power supply.
[0019] As noted below, variations of the device allow for reduce
friction between the shaft and sheath to allow relatively low force
advancement of a distal end of the shaft out of the far end of the
sheath for advancement the energy transfer element.
[0020] Additional variations of the invention include devices
allowing for repeatable deployment of the expandable energy
transfer element while maintaining the orientation and/or profile
of the components of the energy transfer element. One such example
includes an energy transfer basket comprising a plurality of legs,
each leg having a distal end and a proximal end, each leg having a
flexure length that is less than a full length of the leg. The legs
are coupled to near and far alignment components. The near
alignment component includes a plurality of near seats extending
along an axis of the alignment component. The near alignment
component can be secured to the elongate shaft of the device. The
far alignment component may have a plurality of far seats extending
along an axis of the alignment component, where the plurality of
near seats are in alignment with the plurality of far seats. In
these variations of the device, each distal end of each leg is
nested within a far seat of the far alignment component and each
proximal end of each leg is nested within a near seat of the near
alignment component such that an angle between adjacent legs is
determined by an angle between adjacent near seats and the flexure
length of each length is determined by the distance between near
and far alignment components.
[0021] One or both of the components may include stops that control
flexure length of each leg. Such a design increases the likelihood
that the flexure of each leg is unif rm.
[0022] An additional variation of the device includes a catheter
for use in tortuous anatomy to deliver energy from a power supply
to a body passageway. Such a catheter includes an expandable energy
transfer element having a reduced profile for advancement and an
expanded profile to contact a surface of the body passageway and an
elongate shaft having a near end, a far end adapted for insertion
into the body, the expandable energy transfer element coupled to
the far end of the shaft, the shaft having a length sufficient to
access remote areas in the anatomy. The design of this shaft
includes a column strength sufficient to advance the expandable
energy transfer element within the anatomy, and a flexibility that
permits self-centering of the energy transfer element when expanded
to contact the surface of the body passageway.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Each of the following figures diagrammatically illustrates
aspects of the invention. Variation of the invention from the
aspects shown in the figures is contemplated.
[0024] FIG. 1 is an illustration of the airways within a human
lung.
[0025] FIG. 2A is a schematic view of an exemplary system for
delivering energy according to the present invention.
[0026] FIG. 2B is a side view of a device extending out of an
endoscope/bronchoscope, where the device has an active distal end
for treating tissue using energy delivery.
[0027] FIGS. 3A-3G show various features of the device allowing for
low force deployment of the energy element.
[0028] FIG. 3H illustrates a sheathless device having an oblong or
oval shaft cross section.
[0029] FIG. 3I illustrates another variation of the device having a
D-shaped cross section.
[0030] FIGS. 4A-4C illustrate various alignment components of the
device.
[0031] FIGS. 4D-4E demonstrate the alignment components coupled to
a leg of the device.
[0032] FIGS. 4F-4H illustrate an additional variation of an
alignment component.
[0033] FIG. 41 illustrates yet another variation of an alignment
component.
[0034] FIG. 4J illustrates an angle between basket electrode
legs.
[0035] FIGS. 5A-5B is a variation of an energy transfer element
according to the present device.
[0036] FIGS. 5C-5D show variations in which the legs of the device
are biased to expand outward.
[0037] FIGS. 5E-5F illustrate another variation of the leg having a
pre-shaped form.
[0038] FIGS. 5G-5I show further variations of the pre-bent
legs.
[0039] FIGS. 5J-5L illustrate the pre-shaped legs in a collapsed
and expanded configuration, wherein the proximal and distal
alignment components extend within the expandable basket.
[0040] FIGS. 5M-5N illustrate the pre-shaped legs in an expanded
configuration, wherein a basket support is disposed within the
expandable basket.
[0041] FIGS. 6A-6C show various basket configurations for the
device.
[0042] FIGS. 7A-7D illustrate various features of variations of
legs for use with the present devices.
[0043] FIGS. 8A-8D show various junctions for use with the present
devices to improve alignment when the device is advanced through
tortuous anatomy.
[0044] FIGS. 9A-9J are addition variations of junctions.
[0045] FIGS. 10A-10D shows additional variations of junctions for
use in the present devices.
[0046] FIG. 11 is a cross sectional view of an airway in a healthy
lung.
[0047] FIG. 12 shows a section through a bronchiole having an
airway diameter smaller than that shown in FIG. 11.
[0048] FIG. 13 illustrates the airway of FIG. 11 in which the
smooth muscle 314 has hypertrophied and increased in thickness
causing reduction of the airway diameter.
[0049] FIG. 14 is a schematic side view of the lungs being treated
with a treatment device 330 as described herein.
DETAILED DESCRIPTION
[0050] It is understood that the examples below discuss uses in the
airways of the lungs. However, unless specifically noted, the
invention is not limited to use in the lung. Instead, the invention
may have applicability in various parts of the body. Moreover, the
invention may be used in various procedures where the benefits of
the device are desired.
[0051] As described in U.S. Pat. No. 6,634,363, the entirety of
which has been incorporated by reference above, one way of
improving airflow is to decrease the resistance to airflow within
the lungs. There are several approaches to reducing this
resistance, including but not limited to reducing the ability of
the airway to contract, increasing the airway diameter, reducing
the inflammation of airway tissues, and/or reducing the amount of
mucus plugging of the airway. Embodiments described herein include
advancing a treatment device into the lung and treating the lung to
at least reduce the ability of the lung to produce at least one
symptom of reversible obstructive pulmonary disease. The following
is a brief discussion of some causes of increased resistance to
airflow within the lungs and the treatment described herein. As
such, the following discussion is not intended to limit the aspects
or objective of the method as the method may cause physiological
changes not described below but such changes still contributing to
reducing or eliminating at least one of the symptoms of reversible
obstructive pulmonary disease.
Reducing the Ability of the Airway to Contract
[0052] In embodiments, the inventive treatment reduces the ability
of the airways to narrow or to reduce in diameter due to airway
smooth muscle contraction. The treatment uses a modality of
treatments including, but not limited to the following: chemical,
radio frequency, radioactivity, heat, ultrasound, radiant, laser,
microwave, or mechanical energy (such as in the form of cutting,
punching, abrading, rubbing, or dilating). This treatment reduces
the ability of the smooth muscle to contract thereby lessening the
severity of an asthma attack. The reduction in the ability of the
smooth muscle to contract may be achieved by treating the smooth
muscle itself or by treating other tissues which in turn influence
smooth muscle contraction or the response of the airway to the
smooth muscle contraction. Treatment may also reduce airway
responsiveness or the tendency of the airway to narrow or to
constrict in response to a stimulus.
[0053] The amount of smooth muscle surrounding the airway can be
reduced by exposing the smooth muscle to energy which either kills
the muscle cells or prevents these cells from replicating. The
reduction in smooth muscle reduces the ability of the smooth muscle
to contract and to narrow the airway during a spasm. The reduction
in smooth muscle and surrounding tissue has the added potential
benefit of increasing the caliber or diameter of the airways, this
benefit reduces the resistance to airflow through the airways. In
addition to the use of debulking smooth muscle tissue to open up
the airways, the device used in embodiments of the present
invention may also eliminate smooth muscle altogether by damaging
or destroying the muscle. The elimination of the smooth muscle
prevents the contraction or spasms of hyper-reactive airways of a
patient having reversible obstructive pulmonary disease. By doing
so, the elimination of the smooth muscle may reduce some symptoms
of reversible obstructive pulmonary disease.
[0054] The ability of the airway to contract can also be altered by
treatment of the smooth muscle in particular patterns. The smooth
muscle is arranged around the airways in a generally helical
pattern with pitch angles ranging from about -30 to about +30
degrees. Thus, the treatment of the smooth muscle in appropriate
patterns interrupts or cuts through the helical pattern of the
smooth muscle at a proper pitch and prevents the airway from
constricting. This procedure of patterned treatment application
eliminates contraction of the airways without completely
eradicating smooth muscle and other airway tissue. A pattern for
treatment may be chosen from a variety of patterns including
longitudinal or axial stripes, circumferential bands, helical
stripes, and the like as well as spot patterns having rectangular,
elliptical, circular or other shapes. The size, number, and spacing
of the treatment bands, stripes, or spots are chosen to provide a
desired clinical effect of reduced airway responsiveness while
limiting insult to the airway to a clinically acceptable level.
[0055] The patterned treatment of the tissues surrounding the
airways with energy provides various advantages. The careful
selection of the portion of the airway to be treated allows desired
results to be achieved while reducing the total healing load.
Patterned treatment can also achieve desired results with decreased
morbidity, preservation of epithelium, and preservation of a
continuous or near continuous ciliated inner surface of the airway
for mucociliary clearance. The pattern of treatment may also be
chosen to achieve desired results while limiting total treatment
area and/or the number of airways treated, thereby improving speed
and ease of treatment.
[0056] Application of energy to the tissue surrounding the airways
may also cause the DNA of the cells to become cross linked. The
treated cells with cross linked DNA are incapable of replicating.
Accordingly, over time, as the smooth muscle cells die, the total
thickness of smooth muscle decreases because of the inability of
the cells to replicate. The programmed cell death causing a
reduction in the volume of tissue is called apoptosis. This
treatment does not cause an immediate effect but causes shrinking
of the smooth muscle and opening of the airway over time and
substantially prevents re-growth. The application of energy to the
walls of the airway may also be used to cause a cross linking of
the DNA of the mucus gland cells thereby preventing them from
replicating and reducing excess mucus plugging or production over
time.
[0057] The ability of the airways to contract may also be reduced
by altering mechanical properties of the airway wall, such as by
increasing stiffness of the wall or by increasing parenchymal
tethering of the airway wall. Both of these methods increase the
strength of the airway wall and further oppose contraction and
narrowing of the airway.
[0058] There are several ways to increase the stiffness of the
airway wall. One way to increase stiffness is to induce fibrosis or
a wound healing response by causing trauma to the airway wall. The
trauma can be caused by delivery of therapeutic energy to the
tissue in the airway wall, by mechanical insult to the tissue, or
by chemically affecting the tissue. The energy is preferably
delivered in such a way that it minimizes or limits the
intra-luminal thickening that may occur.
[0059] Another way to increase the effective stiffness of the
airway wall is to alter the submucosal folding of the airway upon
narrowing. The mucosal layer includes the epithelium, its basement
membrane, and the lamina propria, a subepithelial collagen layer.
The submucosal layer may also play a role in airway folding. As an
airway narrows, its perimeter remains relatively constant, with the
mucosal layer folding upon itself. As the airway narrows further,
the mucosal folds mechanically interfere with each other,
effectively stiffening the airway. In asthmatic patients, the
number of folds is fewer and the size of the folds is larger, and
thus, the airway is free to narrow with less mechanical
interference of mucosal folds than in a healthy patient. Thus,
asthmatic patients have a decrease in airway stiffness and the
airways have less resistance to narrowing.
[0060] The mucosal folding in asthmatic patients can be improved by
treatment of the airway in a manner which encourages folding.
Preferably, a treatment will increase the number of folds and/or
decrease the size of the folds in the mucosal layer. For example,
treatment of the airway wall in a pattern such as longitudinal
stripes can encourage greater number of smaller mucosal folds and
increase airway stiffness.
[0061] The mucosal folding can also be increased by encouraging a
greater number of smaller folds by reducing the thickness of the
mucosa and/or submucosal layer. The decreased thickness of the
mucosa or submucosa may be achieved by application of energy which
either reduces the number of cells in the mucosa or submucosal
layer or which prevents replication of the cells in the mucosa or
submucosal layer. A thinner mucosa or submucosal layer will have an
increased tendency to fold and increased mechanical stiffening
caused by the folds.
[0062] Another way to reduce the ability of the airways to contract
is to improve parenchymal tethering. The parenchyma surrounds
airways and includes the alveolus and tissue connected to and
surrounding the outer portion of the airway wall. The parenchyma
includes the alveolus and tissue connected to and surrounding the
cartilage that supports the larger airways. In a healthy patient,
the parenchyma provides a tissue network which connects to and
helps to support the airway. Edema or accumulation of fluid in lung
tissue in patients with asthma or COPD is believed to decouple the
airway from the parenchyma reducing the restraining force of the
parenchyma which opposes airway constriction. Energy can be used to
treat the parenchyma to reduce edema and/or improve parenchymal
tethering.
[0063] In addition, the applied energy may be used to improve
connection between the airway smooth muscle and submucosal layer to
the surrounding cartilage, and to encourage wound healing, collagen
deposition, and/or fibrosis in the tissue surrounding the airway to
help support the airway and prevent airway contraction.
Increasing the Airway Diameter
[0064] Hypertrophy of smooth muscle, chronic inflammation of airway
tissues, and general thickening of all parts of the airway wall can
reduce the airway diameter in patients with reversible obstructive
pulmonary, disease. Increasing the overall airway diameter using a
variety of techniques can improve the passage of air through the
airways. Application of energy to the airway smooth muscle of an
asthmatic patient can debulk or reduce the volume of smooth muscle.
This reduced volume of smooth muscle increases the airway diameter
for improved air exchange.
[0065] Reducing inflammation and edema of the tissue surrounding
the airway can also increase the diameter of an airway.
Inflammation and edema (accumulation of fluid) of the airway are
chronic features of asthma. The inflammation and edema can be
reduced by application of energy to stimulate wound healing and
regenerate normal tissue. Healing of the epithelium or sections of
the epithelium experiencing ongoing denudation and renewal allows
regeneration of healthy epithelium with less associated airway
inflammation. The less inflamed airway has an increased airway
diameter both at a resting state and in constriction. The wound
healing can also deposit collagen which improves parenchymal
tethering.
[0066] Inflammatory mediators released by tissue in the airway wall
may serve as a stimulus for airway smooth muscle contraction.
Therapy that reduces the production and release of inflammatory
mediator can reduce smooth muscle contraction, inflammation of the
airways, and edema. Examples of inflammatory mediators are
cytokines, chemokines, and histamine. The tissues which produce and
release inflammatory mediators include airway smooth muscle,
epithelium, and mast cells. Treatment of these structures with
energy can reduce the ability of the airway structures to produce
or release inflammatory mediators. The reduction in released
inflammatory mediators will reduce chronic inflammation, thereby
increasing the airway inner diameter, and may also reduce
hyper-responsiveness of the airway smooth muscle.
[0067] A further process for increasing the airway diameter is by
denervation. A resting tone of smooth muscle is nerve regulated by
release of catecholamines. Thus, by damaging or eliminating nerve
tissue in the airways the resting tone of the smooth muscle is
reduced, and the airway diameter is increased. Resting tone may
also be reduced by directly affecting the ability of smooth muscle
tissue to contract.
[0068] FIGS. 11 and 12 illustrate cross sections of two different
airways in a healthy patient. The airway of FIG. 11 is a medium
sized bronchus having an airway diameter D1 of about 3 mm. FIG. 12
shows a section through a bronchiole having an airway diameter D2
of about 1.5 mm. Each airway includes a folded inner surface or
epithelium 310 surrounded by stroma 312 and smooth muscle tissue
314. The larger airways including the bronchus shown in FIG. 11
also have mucous glands 316 and cartilage 318 surrounding the
smooth muscle tissue 314. Nerve fibers 320 and blood vessels 322
also surround the airway.
[0069] FIG. 13 illustrates the bronchus of FIG. 11 in which the
smooth muscle 314 has hypertrophied and increased in thickness
causing the airway diameter to be reduced from the diameter D1 to a
diameter D3.
[0070] FIG. 14 is a schematic side view of the lungs being treated
with a treatment device 330 as described in the references
incorporated by reference herein, as set forth below. The treatment
device 330 is an elongated member for treating tissue at a
treatment site 334 within a lung. The treatment device 330 may use
a variety of processes to achieve a desired response. The treatment
device 330 may use a modality of treatments as represented by the
treatment source 332, including, but not limited to the following:
chemical, radio frequency, radioactivity, heat, ultrasound,
radiant, laser, microwave, or mechanical energy (such as in the
form of cutting, punching, abrading, rubbing, or dilating).
Although the invention discusses treatment of tissue at the surface
it is also intended that the invention include treatment below an
epithelial layer of the lung tissue.
[0071] As described in U.S. patent application Ser. No. 09/436,455
(now U.S. Pat. No. 7,425,212), the entirety of which has been
incorporated by reference below, the airways which are treated with
the device according to embodiments of the present invention are
preferably 1 mm in diameter or greater, more preferably 3 mm in
diameter. The devices are preferably used to treat airways of the
second to eighth generation, more preferably airways of the second
to sixth generation.
[0072] FIG. 2A shows a schematic diagram of one example of a system
10 for delivering therapeutic energy to tissue of a patient for use
with the device described herein. The illustrated variation shows,
the system 10 having a power supply (e.g., consisting of an energy
generator 12, a controller 14 coupled to the energy generator, a
user interface surface 16 in communication with the controller 14).
It is noted that the device may be used with a variety of systems
(having the same or different components). For example, although
variations of the device shall be described as RF energy delivery
devices, variations of the device may include resistive heating
systems, infrared heating elements, microwave energy systems,
focused ultrasound, cryo-ablation, or any other energy deliver
system. It is noted that the devices described should have
sufficient length to access the tissue targeted for treatment. For
example, it is presently believed necessary to treat airways as
small as 3 mm in diameter to treat enough airways for the patient
to benefit from the described treatment (however, it is noted that
the invention is not limited to any particular size of airways and
airways smaller than 3 mm may be treated). Accordingly, devices for
treating the lungs must be sufficiently long to reach deep enough
into the lungs to treat these airways. Accordingly, the length of
the sheath/shaft of the device that is designed for use in the
lungs should preferably be between 1.5-3 ft long in order to reach
the targeted airways.
[0073] The particular system 10 depicted in FIG. 2A is one having a
user interface as well as safety algorithms that are useful for the
asthma treatment discussed above. Addition information on such a
system may be found in U.S. Provisional application No. 60/674,106,
filed Apr. 21, 2005 entitled CONTROL METHODS AND DEVICES FOR ENERGY
DELIVERY, the entirety of which is incorporated by reference
herein.
[0074] Referring again to FIG. 2A, a variation of a device 100
described herein includes a flexible sheath 102, an elongate shaft
104 (in this example, the shaft extends out from the distal end of
the sheath 102), and a handle or other operator interface 106
(optional) secured to a proximal end of the sheath 102. The distal
portion of the device 100 includes an energy transfer element 108
(e.g., an electrode, a basket electrode, a resistive heating
element, cryoprobe, etc.). Additionally, the device includes a
connector 110 common to such energy delivery devices. The connector
110 may be integral to the end of a cable 112 as shown, or the
connector 110 may be fitted to receive a separate cable 112. In any
case, the device is configured for attachment to the power supply
via some type connector 110. The elongate portions of the device
102 and 104 may also be configured and sized to permit passage
through the working lumen of a commercially available bronchoscope
or endoscope. As discussed herein, the device is often used within
an endoscope, bronchoscope or similar device. However, the device
may also be advanced into the body with or without a steerable
catheter, in a minimally invasive procedure or in an open surgical
procedure, and with or without the guidance of various vision or
imaging systems.
[0075] FIG. 2A also illustrates additional components used in
variations of the system. Although the depicted systems are shown
as RF type energy delivery systems, it is noted that the invention
is not limited as such. Other energy delivery configurations
contemplated may include or not require some of the elements
described below. The power supply (usually the user interface
portion 16) shall have connections 20, 28, 30 for the device 100,
return electrode 24 (if the system 10 employs a monopolar RF
configuration), and actuation pedal(s) 26 (optional). The power
supply and controller may also be configured to deliver RF energy
to an energy transfer element configured for bipolar RF energy
delivery. The user interface 16 may also include visual prompts 32,
60, 68, 74 for user feedback regarding setup or operation of the
system. The user interface 16 may also employ graphical
representations of components of the system, audio tone generators,
as well as other features to assist the user with system use.
[0076] In many variations of the system, the controller 14 includes
a processor 22 that is generally configured to accept information
from the system and system components, and process the information
according to various algorithms to produce control signals for
controlling the energy generator 12. The processor 22 may also
accept information from the system 10 and system components,
process the information according to various algorithms and produce
information signals that may be directed to the visual indicators,
digital display or audio tone generator of the user interface in
order to inform the user of the system status, component status,
procedure status or any other useful information that is being
monitored by the system. The processor 22 of the controller 14 may
be digital IC processor, analog processor or any other suitable
logic or control system that carries out the control algorithms.
U.S. Provisional application No. 60/674,106 filed Apr. 21, 2005
entitled CONTROL METHODS AND DEVICES FOR ENERGY DELIVERY the
entirety of which is incorporated by reference herein.
[0077] As described in U.S. Patent Application Publication No.
2002/0091379, the entirety of which has been incorporated by
reference above, the power supply can include circuitry for
monitoring parameters of energy transfer: (for example, voltage,
current, power, impedance, as well as temperature from the
temperature sensing element), and use this information to control
the amount of energy delivered. In the case of delivering RF
energy, typical frequencies of the RF energy or RF power waveform
are from 300 to 1750 kHz with 300 to 500 kHz or 450 to 475 being
preferred. The RF power-level generally ranges from about 0-30 W
but depends upon a number of factors such as the size and number of
the electrodes. The controller may also be configured to
independently and selectively apply energy to one or more of the
basket leg electrodes.
[0078] A power supply may also include control modes for delivering
energy safely and effectively. Energy may be delivered in open loop
(power held constant) mode for a specific time duration. For
example, a power setting of 8 to 30 Watts for up to 10 seconds is
suitable and a power setting of 12 to 30 Watts for up to 5 seconds
is preferred. For more permanent restructuring of the airways, a
power setting of 8 to 15 Watts for 5 to 10 seconds is suitable. For
mere temporary relief or enlargement of the airway, a power setting
of 10 to 25 Watts for up to 3 seconds is suitable. With higher
power settings, correspondingly lower time durations are preferred
to limit collateral thermal damage.
[0079] Energy may also be delivered in temperature control mode,
with output power varied to maintain a certain temperature-for a
specific time duration. For example, energy may be delivered for up
to 20 seconds at a temperature of 55 to 80 degrees C., and more
preferably, energy is delivered up to 10 seconds at a temperature
in the range of 60 to 70 degrees C. For more permanent
restructuring of the airways, energy is delivered for 5 to 10
seconds at a temperature in the range of 60 to 70 degrees C. For
mere temporary relief or enlargement of the airway, energy is
delivered for up to 5 seconds at a temperature of 55 to 80 degrees
C. Additionally, the power supply may operate in impedance control
mode.
[0080] FIG. 2B illustrates one example of an energy transfer
element 108. In this example the energy transfer element 108 is a
"basket-type" configuration that requires actuation for expansion
of the basket in diameter via a slide mechanism 114 on the handle
106. Such a feature is useful when the device is operated
intralumenally or in anatomy such as the lungs due to the varying
size of the bronchial passageways that may require treatment. As
illustrated, the basket contains a number of arms 120 which carry
electrodes (not shown). In this variation the arms 120 are attached
to the elongated shaft 104 at a proximal end while the distal end
of the arms 120 are affixed to a distal tip 122. To actuate the
basket 108 a wire or tether 124 is affixed to the distal tip 122 to
enable compression of the arms 120 between the distal tip 122 and
elongate sheath 104.
[0081] FIG. 2B also illustrates the device 100 as being advanced
through a working channel 33 of a bronchoscope 18. While a
bronchoscope 18 may assist in the procedure, the device 100 may be
used through direct insertion or other insertion means as well.
[0082] As noted above, some variations of the devices described
herein have sufficient lengths to reach remote parts of the body
(e.g., bronchial passageways around 3 mm in diameter). FIGS. 3A-3G
illustrate various configurations that reduce the force required to
actuate the device's basket or other energy transfer element.
[0083] FIG. 3A illustrates a cross section taken from the sheath
102 and elongate shaft 104. As shown, the sheath 102 includes an
outer layer 126 and an inner lubricious layer 128. The outer layer
126 may be any commonly known polymer such as Nylon, PTFE, etc. The
lubricious layers 128 discussed herein may comprise a lubricious
polymer (for example, HDPE, hydrogel, polytetrafluoroethylene).
Typically, lubricious layer 128 will be selected for optimal
pairing with the shaft 104. One means to select a pairing of
polymers is to maximize the difference in Gibbs surface energy
between the two contact layers. Such polymers may also be chose to
give the lubricious layer 128 a different modulus of elasticity
than the outer layer 126. For example, the modulus of the
lubricious layer 128 may be higher or lower than that of the outer
layer 126.
[0084] Alternatively, or in combination, the lubricious layers 128
may comprise a fluid or liquid (e.g., silicone, petroleum based
oils, food based oils, saline, etc.) that is either coated or
sprayed on the interface of the shaft 104 and sheath 102. The
coating may be applied at the time of manufacture or at time of
use. Moreover, the lubricious layers 128 may even include polymers
that are treated such that the surface properties of the polymer
changes while the bulk properties of the polymer are unaffected
(e.g., via a process of plasma surface modification on polymer,
fluoropolymer, and other materials). Another feature of the
treatment is to treat the surfaces of the devices with substances
that provide antibacterial/antimicrobial properties.
[0085] In one variation of the invention, the shaft 104 and/or
sheath 102 will be selected from a material to provide sufficient
column strength to advance the expandable energy transfer element
within the anatomy. Furthermore, the materials and or design of the
shaft/sheath will permit a flexibility that allows the energy
transfer element to essentially self-align or self-center when
expanded to contact the surface of the body passageway. For
example, when advanced through tortuous anatomy, the flexibility of
this variation should be sufficient that when the energy transfer
element expands, the shaft and/or sheath deforms to permit
self-centering of the energy transfer element. Examples of shaft
104 or sheath 102 materials include nylon, PET, LLDPE, HDPE, Plexar
PX, PTFE, teflon and/or any other polymer commonly used in medical
devices. As described above, the inner or outer surfaces of the
shaft 104 and/or sheath 102 may also comprise lubricant
impregnations or coatings, such as silicone fluid, carbon, PTFE, or
any of the materials described with reference to lubricous layer
128. It is noted that the other material selection and/or designs
described herein shall aid in providing this feature of the
invention.
[0086] FIG. 3A also depicts a variation of a shaft 104 for use in
the present device. In this variation the shaft 104 includes a
corrugated surface 130. It is envisioned that the corrugated
surface 130 may include ribbed, textured, scalloped, striated,
ribbed, undercut, polygonal, or any similar geometry resulting in a
reduced area of surface contact with any adjoining surface(s). The
corrugated surface 130 may extend over a portion or the entire
length of the shaft 104. In addition, the shape of the corrugations
may change at varying points along the shaft 104.
[0087] The shaft 104 may also include one or more lumens 132, 134.
Typically, one lumen will suffice to provide power to the energy
transfer elements (as discussed below). However, in the variation
show, the shaft may also benefit from additional lumens (such as
lumens 134) to support additional features of the device (e.g.,
temperature sensing elements, other sensor elements such as
pressure or fluid sensors, utilizing different lumens for different
sensor leads, and utilizing separate or the same lumen(s) for fluid
delivery or suctioning, lumens for blowing gas (e.g., pressurized
air, hot air) into the airway to move or desiccate secretions
(e.g., mucus) out of the way, etc.). In addition, the lumen(s) may
be used to simultaneously or sequentially deliver fluids and/or
suction fluid to assist in managing the moisture within the
passageway. Such management may optimize the electrical coupling of
the electrode to the tissue (by, for example, altering
impedance).
[0088] Since the device is suited for use in tortuous anatomy, a
variation of the shaft 104 may have lumens 134 that are
symmetrically formed about an axis of the shaft. As shown, the
additional lumens 134 are symmetric about the shaft 104. This
construction provides the shaft 104 with a cross sectional symmetry
that aid in preventing the shaft 104 from being predisposed to flex
or bend in any one particular direction. Further, the shaft 104 may
be designed to increase clearance between a center wire 124 that
runs through the shaft lumen 132 so as to minimize friction and
improve basket 108 deployment in tortuous anatomy. Still further,
the shaft 104 may be designed so as to efficiently transmit torque
from the handle 106 to the basket array 108 in order to rotate the
basket array 108 within the airways so as to enhance device
positioning. For example, this may be accomplished by incorporating
a braided member (e.g., braided wire) into the shaft 104 extrusion
or by joining the shaft 104 coaxially with the braided member.
[0089] FIG. 3B illustrates another variation where the sheath 102
includes an outer layer 126 and a lubricious layer 128. However, in
this variation the lubricious layer 128 also includes a corrugated
surface 136. It is noted that any combination of the sheath 102 and
shaft 104 may have a corrugated surface.
[0090] FIG. 3C illustrates yet another aspect of construction of a
sheath 102 for use with the present device. In this variation, the
sheath 102 includes a multi-layer construction having an outer
layer 126, one or more middle layers 138. The middle layers 138 may
be selected to have properties that transition between the outer
layer properties and the lubricious layer properties, and improve
the bonding between inner and outer layer. Alternatively, the
middle layer 138 may be selected to aid in the column strength of
the device. An example of the middle layer includes LLDPE, Plexar
PX 306, 3060, and/or 3080.
[0091] FIG. 3D depicts a variation of a shaft 104 for use with the
devices described herein where the shaft outer surface comprises a
lubricious layer 140. As illustrated, the shaft outer surface may
also optionally have a corrugated surface 130. FIGS. 3E-3G
illustrate additional variations of corrugated surfaces. As shown
in FIGS. 3E and 3F, either or both the sheath 102 and the shaft 104
may have corrugated surfaces that are formed by interrupting the
surface. Naturally, different shapes and configurations may be
otherwise constructed. FIG. 3G illustrates a variation where the
sheath 102 comprises protrusions or spacer 142 to separate the
surfaces of the sheath/shaft.
[0092] FIGS. 3H and 3I illustrate further variations of a shaft 104
which may be incorporated within any of the devices described
herein. FIG. 3H illustrates a two lumen shaft 104 having an oblong
or oval shaped cross section. The first lumen 132 may be utilized
to receive the conductive center wire 124 which electrically
couples the legs 120 to the energy generator 12. The second lumen
134 may be utilized to receive temperature detecting leads 172 as
described in more detail with reference to FIG. 7C. Further, a coil
135 or other reinforcing element (e.g., polymeric insert, braided
member) may be utilized to prevent kinking or collapse of the shaft
104, which is of particular benefit during basket 108 deployment in
tortuous anatomy. In this depiction, the coiled wire 135 is
disposed within lumen 132 of the shaft 104 and surrounding the
center wire 124. Referring now to FIG. 3I, a single lumen shaft 104
having a D-shaped cross section is illustrated. The single lumen
132 receives the center wire 124 as in FIG. 3H, but in this
embodiment the reinforcing coil 135 is disposed outside the shaft
104 and further encompasses the temperature detecting leads 172.
The coil 135 may also reinforce a tubular sheath 102 which is
disposed over the coil 135 and extends along a length of the shaft
104. The embodiments of FIGS. 3I and 3H also provide an exposed
basket 108 configuration (e.g., sheathless) which reduces friction
and as such improves basket 108 deployment mechanics.
[0093] These oblong, oval, or D-shaped shaft cross sections
advantageously allow for a reduced profile while still axially
centering the center wire 124 with respect to the expandable basket
108. This reduced size profile not only permits passage of the
sheathless catheter of FIG. 3H or sheathed catheter of FIG. 3I
through the working channel lumen of an access device, such as a
bronchoscope, but allows for fluid delivery or suction through an
opening created between the working channel lumen and an outer
surface of the catheter. As already described above, alternatively
or in the adjunct, additional lumens 134 within the device shaft
104 may be utilized for fluid delivery of cleaning fluids (e.g.,
saline, bio-compatible fluids), drugs (e.g., lidocaine,
tetracaine), cooling fluids (e.g., cooled saline, cooled sterile
water, or other fluids for cooling the airway wall), electrically
conductive fluids (e.g., saline), thermally conductive fluids, or
fluids to increase the viscosity of mucus so it can be more easily
suctioned (e.g., saline), or for suctioning of delivered fluids or
excretions within the airway (e.g., mucus). Advantageously,
suctioning or fluid delivery from or to the airway may be
accomplished while the asthma treatment device remains within the
airways without requiring the device user to pull the device out of
the airway, which in turn reduces procedure time and improves
patient manageability. For example, irrigation and/or suctioning
may be carried out simultaneously or sequentially with energy
delivery to the airway wall while the device is within the
airway.
[0094] As described in U.S. Pat. No. 6,634,363, the entirety of
which has been incorporated by reference above, embodiments of the
invention may also include the additional step of reducing or
stabilizing the temperature of lung tissue near to a treatment
site. This may be accomplished for example, by injecting a cold
fluid into lung parenchyma or into the airway being treated, where
the airway is proximal, distal, or circumferentially adjacent to
the treatment site. The fluid may be sterile normal saline, or any
other bio-compatible fluid. The fluid may be injected into
treatment regions within the lung while other regions of the lung
normally ventilated by gas. Or, the fluid may be oxygenated to
eliminate the need for alternate ventilation of the lung. Upon
achieving the desired reduction or stabilization of temperature the
fluid may be removed from the lungs. In the case where a gas is
used to reduce temperature, the gas may be removed from the lung or
allowed to be naturally exhaled. One benefit of reducing or
stabilizing the temperature of the lung may be to prevent excessive
destruction of the tissue, or to prevent destruction of certain
types of tissue such as the epithelium, or to reduce the systemic
healing load upon the patient's lung.
[0095] FIGS. 4A-4D illustrate yet another feature that may be
incorporated with any of the subject devices. FIG. 4A illustrates
an example of an alignment component 150. In this variation, the
alignment component 150 includes a plurality of seats 152 that nest
electrode arms (not shown). As discussed herein, the seats 152
allow for improved control of the angular spacing of the arms.
Moreover, the seats 152 permits design of a device in which the
flexure length of each of the arms of a basket type device is
uniform (even if the tolerance of each arm varies). Though the
alignment component 150 is shown as having four seats 152, any
number of seats may be employed.
[0096] The alignment component 150 also includes a stop 154. The
stop 154 acts as a reference guide for placement of the arms as
discussed below. In this variation, the stop 154 is formed from a
surface of an end portion 158. This end portion 158 is typically
used to secure the alignment component 150 to (or within) the
sheath/shaft of the device. The alignment component 150 may
optionally include a through hole or lumen 156.
[0097] FIG. 4B illustrates another variation of an alignment
component 150. This variation is similar to the variation shown in
FIG. 4A, with the difference being the length of the end portion
158. The smaller end portion 158 may optionally be employed when
the component 150 is used at the distal end of the device. In such
a case, the component 158 may not be attached to the sheath or
shaft. In addition, the end portion 158 may optionally be rounded,
for example, to minimize tissue trauma that may be caused by the
end of the device.
[0098] The alignment components 150 of the present invention may be
fabricated from a variety of polymers (e.g., PEEK, ULTEM, PEI,
nylon, PET and/or any other polymer commonly used in medical
devices), either by machining, molding, or by cutting an extruded
profile to length. One feature of this design is electrical
isolation between the legs, which may also be obtained using a
variation of the invention that employs a ceramic material for the
alignment component. However, in one variation of the invention, an
alignment component may be fabricated from a conductive material
(e.g., stainless steel, polymer loaded with conductive material, or
metallized ceramic) so that it provides electrical conductivity
between adjacent electrode legs and the conductive wire. In such a
case, a power supply may be coupled to the alignment component,
which then electrically couples all of the legs placed in contact
with that component. The legs may be attached to the conductive
alignment component with conductive adhesive, or by soldering or
welding the legs to the alignment component. This does not preclude
the legs and alignment component form being formed from one piece
of metal.
[0099] Devices of the present invention may have one or more
alignment components. Typically the alignment components are of the
same size and/or the angular spacing of the seats is the same.
However, variations may require alignment components of different
sizes and/or different angular spacing. Another variation of the
invention is to have the seats at an angle relative to the axis of
the device, so as to form a helically shaped energy delivery
element.
[0100] FIG. 4C illustrates another variation of an alignment
component 150. In this variation, the alignment component 150
includes four seats 152. This variation includes an alignment stop
154 that protrudes from the surface of the component 150. In
addition, the end portion 158 of the alignment component 150 is
also of a cross section that may improve strength of the connection
between the component and the sheath/shaft. In this case, the end
portion 158 allows for crimping of the sheath/shaft. Optionally as
shown, radial protrusions 178 at the right of the end portion 158
may be included to allow heat bonding of the alignment component to
the shaft. In this case, the shaft may be a polymer with a melting
temperature lower than that of the alignment component. When
constrained to be coaxial, heat, and if necessary axial pressure,
may be applied to join the two components.
[0101] FIG. 4D illustrates the protrusion-type stop 154 that
retains a notch 162 of the electrode leg 160. This mode of securing
the electrode leg 160 provides a "redundant-type" joint. In one
example, the leg 160 is secured to the alignment component 150
using a sleeve (not shown) placed over both the leg 160 and
alignment component 150 with or without the use of an adhesive
within the sleeve. The notch 162 in the leg 160 is placed around
the protrusion-type-stop 154. As a result, the notch-stop interface
prevents the leg from being pulled from the device and is
especially useful to prevent the proximal or near ends of the legs
from separating from the device. It is noted that this safety
feature is especially important when considering that if the
proximal/near ends of the legs separate and hook on the anatomical
passage, it may be difficult or impossible to remove the device
from the passage. Such a failure may require significant medical
intervention.
[0102] FIG. 4E illustrates one example of a leg 160 affixed to
near/proximal and far/distal alignment components 144, 146. As
shown, the leg 160 may have an insulated portion 164 and an exposed
portion 166 that form electrodes. The near and far ends of the leg
160 are secured to respective alignment components 144, 146. In
this example, sleeves 168 and 170 cover the leg and alignment
component. As noted above, one or both of the alignment components
may be electrically conductive to provide power to the electrodes.
Furthermore, adhesive (e.g., cyanoacrylate (e.g., loctite),
UV-cured acrylic, epoxy, and/or any such adhesive) may also be used
to secure the leg and/or sleeves to the components.
[0103] Additionally, the alignment components may be designed such
that the sleeves 168, 170 may be press or snap fit onto the
alignment components, eliminating the need for adhesively bonding
the sleeves to the alignment components. FIG. 4F illustrates a
perspective view of an end portion of an alignment component 150
having one or more slots 186 to create end portion segments 184.
The slots 186 permit deflection of the end portion segments 184 to
allow sliding of a sleeve or hypotube (either a near or far sleeve
168 or 170) over the end portion. FIG. 4G shows a cross sectional
view of the component 150 of FIG. 4F. As shown, once advanced over
the end portion segment 184, the sleeve or hypotube becomes secured
to the component 150. To lock the sleeve in place, an insert or
wire member 124 (not shown) is placed in the through hole or lumen
156. The insert or wire member prevents inward deflection of the
end portion segments 184 thereby ensuring that the sleeve or
hypotube remains secured to the component 150.
[0104] Referring now to FIG. 41, another variation of the alignment
component 150 is shown. This proximal joint 150 is similar to that
of FIG. 4C, but has a reduced axial length by omission of the
radial protrusions 178. This shortening improves joint flexibility
in tortuous airways as a user can translate the shaft 104 and
basket assembly 108 with more ease through the sheath 102 which in
turn improves basket 108 deployment. In this embodiment, the end
portion 158 may be directly coupled to the shaft 104 by utilizing
heat shrink (e.g., PET) with a wicking adhesive as described above.
This coupling results in a lower proximal joint profile so as to
reduce the friction between the sheath 102 and shaft 104 which in
turn improves joint 150 flexibility and basket 108 deployment.
Further, in this embodiment, a PET shaft 104 may be utilized to
provide enhanced pushability of the shaft 104 so as to further aid
in basket 108 deployment and to reduce susceptibility to water
absorption so as to ensure greater consistency of deployed basket
diameter (e.g., >10 mm).
[0105] As discussed herein, the seats 152 allow for improved
control of the angular spacing of the legs 160. In particular, the
seats 152 of the proximal and distal alignment components 144, 146
are aligned, wherein the angle between adjacent legs 160 is
determined by the angle between adjacent seat 152. The seats 152
preferably provide for symmetrical deployment of the arms 160,
wherein any angle between adjacent legs varies less than 20
degrees. As shown in cross sectional view of FIG. 4J, in the case
of a four leg basket 108, the angle .alpha. between adjacent legs
is in a range from about 70 degrees to about 110 degrees,
preferably 90 degrees. Likewise, in the case of a six leg basket
108, the angle between adjacent legs is in a range from about 45
degrees to about 75 degrees, preferably 60 degrees so that a
variance is less than 15 degrees. Further, in the case of a eight
leg basket 108, the angle between adjacent legs is in a range from
about 33 degrees to about 57 degrees, preferably 45 degrees so that
a variance is less than 12 degrees or for a ten leg basket 108, the
angle between adjacent legs is in a range from about 26 degrees to
about 46 degrees, preferably 36 degrees so that a variance is less
than 10 degrees. Symmetrical deployment ensures proper temperature
distribution, which may be important for the treatment of asthma in
the lung airways. It will be appreciated that the present invention
is not limited to an even number of basket legs 160. For example,
five or seven basket legs 160 may be employed as long as the
spacing between each leg 160 is equivalent.
[0106] FIG. 5A shows a cross sectional view of two legs 160
attached to alignment components 144, 146. The sheath and shaft
have been omitted for clarity. The flexure length 164 of the leg
160 is defined as the length between the alignment components 144,
146 over which the leg may flex when the proximal and distal ends
are moved closer to one another. As noted above, the alignment
components permit the flexure length 164 of the legs 160 to be
uniform even if the leg lengths vary. The flexure length 164 is
essentially set by the longest leg, the shorter legs may float
between the stops 154 of the alignment components 144, 146. As an
additional measure to prevent the legs 160 from inverting, the
lengths of the sleeves 168 and 170 may be selected to be less than
the length of the respective alignment components 144, 146 (as
shown in the figure). The tendency of the leg to deflect outward
can be improved by selecting the sleeve length as such. When the
legs 160 expand they are supported by their respective seat on the
interior side but unsupported on outer side. In yet another
variation, the seats can slant to predispose the arms to deflect in
a desired direction. For example, as shown in FIG. 5C, the seats
152 can slant as shown to predispose the legs 160 to outward
deflection. Such a construction can be accomplished by machining or
by drafting a molded part in the direction of the catheter axis. As
shown in FIG. 5D, the leg can have a slight bend or shape that
predisposes the legs to bow outward.
[0107] FIG. 5B illustrates the variation of FIG. 5A in an expanded
state. As shown, the device may have a wire 124 or other similar
member that permits movement of the far alignment component 146
relative to the near alignment component 144. As noted herein, the
wire 124 may be electrically conductive to provide power to
electrodes on the device. FIG. 5B also illustrates a ball tip 148
at the end of the device. The ball tip 148 may serve as a means to
secure the wire 124 as well as providing an atraumatic tip for the
device.
[0108] Variations of the wire 124 may include a braided or coiled
wire. The wire may be polymer coated or otherwise treated to
electrically insulate or increase lubricity for easier movement
within the device.
[0109] To expand the energy transfer element 108, the wire 124 may
be affixed to a handle 106 and actuated with a slide mechanism 114
(as shown in FIG. 2A.) In an alternative design, the wire 124 may
be affixed between the handle 106 and the distal end of the energy
transfer element 108. In such a case, the slide mechanism 114 may
be affixed to the shaft 104. Movement of the slide mechanism 114
causes expansion of the element 108 as the shaft 104 causes
movement of the proximal end of the energy transfer element (being
fixed to the shaft) relative to the distal end of the energy
transfer element (being fixed to the wire 124). In an additional
variation, movement of the slide 114 may have two outcomes: 1)
advancing the energy transfer element out of the sheath; and 2)
subsequently expanding the energy transfer element. Such
constructions are disclosed in U.S. patent application Ser. No.
09/436,455 filed Nov. 8, 1999 the entirety of which is incorporated
by reference herein. In a still further variation, movement of the
slide 114 may cause the wire 124 to be pulled proximally while the
shaft 104 is pushed distally so that energy transfer element
remains stationary during deployment.
[0110] Referring now to FIGS. 5E-5N, the electrode legs 160 may be
pre-shaped as already described herein. In particular, the
electrodes 160 may be pre-shaped so as to control the direction in
which the legs deflect upon basket deployment 108 so as to prevent
electrode inversion, provide controlled buckling of the basket
electrode 108, and improve tissue contact.
[0111] FIG. 5E illustrates a pre-bent leg 160 having four discrete
bends 161. As shown in FIG. 5F, when axial compressive loads 163
are applied to the electrode 160 during deployment, the pre-shaped
leg is predisposed to buckle or deflect in a predictable, desired
outwards direction 165 to make contact with the airway wall. Hence,
the pre-shaped leg 160 provides for preferential buckling in the
outward direction 165, which is of particular benefit in tortuous
airways where orthogonal or side loads commonly cause leg
inversions. As illustrated in the example of FIG. 5F, an angle
.beta. of the discrete pre-bends 161 on the proximal and distal
ends of the electrode 160 may be at an angle that is in a range
from about 10 degrees to about 20 degrees, preferably 15
degrees.
[0112] It will be appreciated that several other pre-shaped
variations may be employed to induce buckling in the desired
outward direction 165. For example, the pre-bent electrode may
comprise a single bend 161 as shown in FIG. 5G, two bends 161 as
shown in FIG. 5H, three bends 161 as shown in FIG. 5I, and the
like. Further, the angle .beta. of the bend 161 or the positioning
of the bend 161 may vary depending on a variety of factors. Still
further, the electrode 160 may be pre-shaped to form a continuous
curve, as illustrated in FIG. 2B, or a parabolic curve as
illustrated below in FIG. 6A, or some other pre-shaped
configuration in which a portion of the electrode 160 is
out-of-plane from the axially active compressive loads 163.
[0113] Referring now to FIGS. 5J-5L, cross sectional views of the
pre-bent legs 160 attached to proximal and distal alignment
components 144, 146 are illustrated. The shaft 102 in this
depiction has been omitted for clarity. In this particular
embodiment, the alignment components extend within the expandable
basket 108, as illustrated by reference numerals 144a, 146a. As the
basket is deployed, as shown in FIG. 5L, the proximal and distal
extrusions or flanges 144a, 146a in the basket 108 further prevent
against electrode leg 160 inversions from the desired outward
direction 165.
[0114] In addition or alternatively, inward leg buckling or
inversions may also be prevented by disposing basket support(s)
inside the expandable basket 108. For example, as shown in the
cross sectional view of FIGS. 5M and 5N, a balloon member 171 may
also be deployed inside the basket 108 and inflated to prevent
inward deflection of the electrode legs 160. Further, the balloon
member 171 may utilize its inflation lumen to receive cooling
fluids so as to cool the electrode 160 and airway wall. Still
further, the balloon member 171 may also be utilized to deploy the
basket 108 in lieu of the pull wire 124.
[0115] FIG. 6A illustrates a variation of an energy transfer
element 108 in which the legs 160 have a pre-determined shape. This
shape may be selected as required for the particular application.
As shown, the predetermined shape provides a certain length of the
electrode 166 that may be useful for treatment of a long section of
tissue.
[0116] FIG. 6B illustrates another variation of the energy transfer
element 108. In this variation, the legs 160 extend out of openings
180 in the sheath 102 (in other variations, the legs may extend out
of openings in the shaft). Accordingly, the alignment components
and other parts of the device would be located within the sheath
102.
[0117] FIG. 6C illustrates yet another variation of an energy
transfer element 108. In this variation, the basket is connected at
a proximal end and opened at a distal end. The electrode legs 160
only have a single alignment component 150. The conductive member
(or wire) may be located within the shaft 104. In this variation,
advancement of the energy transfer element 108 out of the sheath
102 causes expansion of the element. The energy transfer elements
may be predisposed or spring loaded to bow outward when advanced
from the sheath.
[0118] FIG. 7A illustrates an example of a leg 160 with an energy
element 180 coiled around the leg 160. In this example, the energy
element 182 uses conductive heating and comprises a resistance
heating element coiled around the leg 160. FIG. 7B illustrates a
variation of the invention having an RF electrode attached to the
basket leg 160. The RF electrode may be attached to the basket leg
160 via the use of a fastener. For example, the electrode may be
attached via the use of a heat shrink fastener, (e.g., polymeric
material such as PET or polyethylene tubing). Alternatively, as
discussed above, the entire leg may be a conductive medium where a
non-conductive coating insulates the majority of the leg leaving
the electrode portion uninsulated. Further examples of energy
transfer element configurations include paired bipolar electrodes,
where the pairs are leg to leg or within each leg, and large
matrices of paired electrodes affixed to a variety of expanding
members (balloons, mechanisms, etc.)
[0119] FIG. 7C illustrates a variation of the invention having
thermocouple leads 172 attached to an electrode 166 or leg of the
device. The leads may be soldered, welded, or otherwise attached.
This variation of the invention shows both leads 172 of the
thermocouple 174 attached in electrical communication to a leg 160
at separate joints (or the leads may be separated but the solder on
each connection actually flows together). In this case, the
temperature sensor is at the surface of the leg. This variation
provides a safety measure in case either joint becomes detached,
the circuit will be open and the thermocouple 174 stops reading
temperature. Such a condition may be monitored via the power supply
and allow a safe shutdown of the system.
[0120] By spacing the leads of the thermocouple closely together to
minimize temperature gradients in the energy transfer element
between the thermocouple leads, thermoelectric voltage generated
within the energy transfer element does not compromise the accuracy
of the measurement. The leads may be spaced as close together as
possible while still maintaining a gap so as to form an intrinsic
junction with the energy transfer element. In another variation of
the device, the thermocouple leads may be spaced anywhere along the
tissue contacting region of the energy transfer element.
Alternatively, or in combination, the leads may be spaced along the
portion of an electrode that remains substantially straight. The
intrinsic junction also provides a more accurate way of measuring
surface temperature of the energy transfer element, as it minimizes
the conduction error associated with an extrinsic junction adhered
to the device.
[0121] The thermocouple leads may be attached to an interior of the
leg or electrode. Such a configuration protects the thermocouple as
the device expands against tissue and protects the tissue from
potential trauma. The device may also include both of the
thermocouple leads as having the same joint.
[0122] The devices of the present invention may use a variety of
temperature sensing elements (a thermocouple being just one
example, others include, infrared sensors, thermistors, resistance
temperature detectors (RTDs), or any other component capable of
detecting temperatures or changes in temperature). The temperature
detecting elements may be placed on a single leg, on multiple legs
or on all of the legs.
[0123] The present invention may also incorporate a junction that
adjusts for misalignment between the branching airways or other
body passages. This junction may be employed in addition to the
other features described herein. FIG. 8A illustrates a device 100
having such a junction 176 allowing alignment of the device to
closely match the alignment of the airway. It is noted that the
present feature also benefits those cases in which the pathway and
target site are offset as opposed to having an angular
difference.
[0124] The junction 176 helps to eliminate the need for alignment
of the axis of the active element 108 with the remainder of the
device in order to provide substantially even tissue contact. The
junction may be a joint, a flexure or equivalent means. A
non-exhaustive listing of examples is provided below.
[0125] The legs 160 of the energy transfer element may have various
shapes. For example, the shapes may be round, rounded or polygonal
in cross section. Additionally, each leg may change cross section
along its axis, providing for, for example, electrodes that are
smaller or larger in cross section that the distal and proximal
portions of each leg. This would provide a variety of energy
delivery characteristics and bending profiles, allowing the design
to be improved such that longer or wider electrode configurations
can be employed. For example, as shown in FIG. 7D, if the
cross-sectional thickness of the electrode portion 166 of the leg
160 is greater than the cross-sectional thickness of the distal and
proximal portions of the leg, the leg would be predisposed to bow
outward in the distal and proximal sections, while remaining
flatter in the electrode area of the leg, potentially providing
improved tissue contact.
[0126] As for the action the junction enables, it allows the distal
end of the device to self-align with the cavity or passageway to be
treated, irrespective of the alignment of the access passageway.
FIG. 8A illustrates an example of where the access passageway and
passageway to be treated are misaligned by an angle .alpha. In the
example shown in FIG. 8B, the misalignment angle .alpha. is greater
than the angle illustrated in FIG. 8A. Yet, the energy transfer
element 108 of the treatment device 100 remains substantially
aligned with the target area.
[0127] FIGS. 8C and 8D illustrate an additional variation of the
junction 176. In this variation the junction 176 may be reinforced
with a reinforcing member 230. The reinforcing member may have some
degree of flexibility to navigate the tortuous anatomy, but the
flexibility will be less than the junction 176. As shown in FIG.
8C, the reinforcing member 230 maintains the device shaft 104 in an
aligned position, preferably for insertion, removal, and or
navigation of the device. When desired, the reinforcing member 230
may be removed from the junction 176 as illustrated in FIG. 8D.
Accordingly, upon removal, the device is free to flex or orientate
as desired. Furthermore, the reinforcing member may be reinserted
within the junction 176 when repositioning or removing the device
from the target site. In additional variations, it is contemplated
that the reinforcing member may be placed external to the
device/junction.
[0128] FIGS. 9A-9I illustrate additional junctions for use in the
devices described herein. As for these examples, FIG. 9A
illustrates a junction 176 in the form of a plurality of turns or
coils 200 of a spring. The coil offers a flexure with 3-dimensional
freedom allowing realignment of the active end of the subject
device in any direction. Of course, a simple hinge or universal
joint may also be employed.
[0129] The length of the junction (whether a spring junction or
some other structure) may vary. Its length may depend on the
overall system diameter. It may also depend on the degree of
compliance desired. For example, with a longer effective junction
length (made by extending the coil with additional turns), the
junction becomes less rigid or more "floppy".
[0130] In any case, it may be desired that the junction has
substantially the same diameter of the device structure adjacent
the junction. In this way, a more atraumatic system can be
provided. In this respect, it may also be desired to encapsulate
the junction with a sleeve or covering if they include open or
openable structures. Junction 176 shown in FIGS. 8A and 8B is
illustrated as being covered. A covering can help avoid
contaminating the joint with body fluid or debris which could
compromise junction function.
[0131] Some of the junctions are inherently protected. Junction 176
shown in FIG. 9B comprises a polymer plug 220 or a section of
polymer having a different flexibility or durometer than adjacent
sections. When a separate piece of polymer is to be employed, it
can be chemically, adhesively, or heat welded to adjacent
structure; when the junction is formed integrally, this may be
accomplished by selective vulcanizing, or reinforcement (even with
a braid or by other means of forming a composite structure).
Generally, it is noted that any connection of pieces or
construction provided may be produced by methods known by those
with skill in the art.
[0132] As for junction 176 shown in FIG. 9C, it is formed by
removing sections of material from the body of the device. Openings
218 formed at the junction may be left empty, covered or filled
with a more compliant material. FIG. 9D also shows a junction 176
in which openings are provided to provide increased flexibility.
Here, openings 218 are offset from each other to form a sort of
flexible universal joint. In either junction variation shown in
FIG. 9C or 9D, the size, number shape, etc. of the opening may vary
or be tuned as desired.
[0133] FIG. 9E shows a junction 176 in the form of a bellows
comprising plurality of pleats 216. Here too, the number of pleats,
etc. may be varied to achieve desirable performance.
[0134] Junction 176 in FIG. 9F shows a true "joint" configuration.
In this case, it is a universal joint provided by ball 204 and
socket 206. These elements may be held together by a tie wire 208,
possibly with caps 210. Other configurations are possible as
well.
[0135] FIG. 9G illustrates a junction 176 in the form of a reduced
diameter section 202. This variation offers greater flexibility by
virtue of its decreased moment of inertia at the junction. While
section 202 is integrally formed, the related junction 176 in FIG.
9H is formed from a hypotube or wire 212 having an exposed junction
section 214 on the shaft 104. Variations of the invention will
permit a junction having a reduced bending moment of inertia
section as compared to the remainder of the device and/or shaft of
the device. Reducing the bending moment of inertia may be
accomplished in any number of ways. For example, there could be an
area of reduced diameter, a section of material having a lower
modulus, a section having a different shape, a flexible joint
structure, etc. It should be noted that there are many additional
ways to reduce the bending moment that will be readily apparent to
those skilled in the art viewing the invention disclosed
herein.
[0136] Yet another junction example is provided in FIG. 9I. Here
junction 176 comprises a plurality of wires 222, 224, 226. In one
variation, the wires simply offer increased flexibility of the
junction. In another variation, the wires serve as an "active" or
"dynamic" junction. The wires may be adjusted relative to one
another to physically steer the distal end of the device. This
junction may be manipulated manually with an appropriate user
interface--especially one, like a joy-stick, that allows for full
3-dimensional or rotational freedom--or it may be controlled by
automation using appropriate hardware and software controls. Of
course, other "dynamic" junctions are possible as well.
[0137] FIG. 9J shows another joint configuration 176 employing an
external sleeve 262 between sections of the shaft 104. A moveable
wire 124 to actuate a distal basket or the like is also shown. The
space between the wire and sleeve may be left open as shown, or
filled in with a flexible polymer 264, such as low durometer
urethane, a visco-elastic material, etc. Though not necessary,
providing an internal member may improve system pushability. The
sleeve itself will typically be a polymeric sleeve. It may be
heat-shrink material such as PET tubing; it may be integrally
formed with either catheter body portion and press fit or slip fit
and glued over other etc.
[0138] Another variation of the junctions includes junctions
variations where the shaft 104 is "floppy" (i.e., without
sufficient column strength for the device to be pushable for
navigation). In FIG. 10A, a tether 232 connects energy transfer
element 108 to the shaft 104 of the device 100. The tether may
simply comprise a flexible wire or cable, it may comprise a
plurality of links, etc. The tether variation of the invention also
accommodates relative motion between the device and the body (e.g.,
tidal motion of breathing, other muscle contractions, etc.) The
tether permits the device to move relative to its intended
treatment location unless the user desires and uses the tether or
the sheath to pull the device back or drive it forward. The tether
may have an alignment component (not illustrated) at the near end
of the energy transfer element 108.
[0139] To navigate such a device to a treatment site, the energy
transfer element 108 and tether 232 may be next to or within the
sheath 102. In this manner, the column strength provided by the
sheath allows for advancement of the active member within the
subject anatomy.
[0140] The same action is required to navigate the device shown in
FIG. 10B. What differs in this variation of the invention, however,
is that the "tether" is actually a continuation of a highly
flexible shaft 104. In this case, the shaft 104 of the device is
shown with a thicker or reinforced wall. In such a device, the
shaft carries the compressive loads on the device back to its
distal end.
[0141] Like the device in FIG. 10B, the devices in FIGS. 10C and
10D have highly flexible shafts 104. However, instead of a
stiffening external sheath, the device may employ a stiffening
obturator 230 within a lumen of the shaft 104. As shown in FIG.
10C, when the obturator 230 fills the lumen, the device is
relatively straight or stiff. When the shaft is withdrawn as shown
in FIG. 10D, the distal end of the device is "floppy" or easily
conformable to the subject anatomy. With the shaft advanced
substantially to the end of the device, it offers ease of
navigation; when withdrawn, it offers a compliant section according
to an aspect of the present invention.
[0142] As for other details of the present invention, materials and
manufacturing techniques may be employed as within the level of
those with skill in the relevant art. The same may hold true with
respect to method-based aspects of the invention in terms of
additional acts a commonly or logically employed. In addition,
though the invention has been described in reference to several
examples, optionally incorporating various features, the invention
is not to be limited to that which is described or indicated as
contemplated with respect to each variation of the invention.
[0143] Various changes may be made to the invention described and
equivalents (whether recited herein or not included for the sake of
some brevity) may be substituted without departing from the true
spirit and scope of the invention. Also, any optional feature of
the inventive variations may be set forth and claimed
independently, or in combination with any one or more of the
features described herein. Accordingly, the invention contemplates
combinations of various aspects of the embodiments or of the
embodiments themselves, where possible. Reference to a singular
item, includes the possibility that there are plural of the same
items present. More specifically, as used herein and in the
appended claims, the singular forms "a," "and," "said," and "the"
include plural referents unless the context clearly dictates
otherwise.
* * * * *