U.S. patent application number 11/612620 was filed with the patent office on 2007-05-10 for expandable electode devices and methods of treating bronchial tubes.
This patent application is currently assigned to Asthmatx, Inc.. Invention is credited to Keith M. Burger, Michael D. Laufer, Bryan E. Loomas, Don A. Tanaka.
Application Number | 20070106296 11/612620 |
Document ID | / |
Family ID | 23373636 |
Filed Date | 2007-05-10 |
United States Patent
Application |
20070106296 |
Kind Code |
A1 |
Laufer; Michael D. ; et
al. |
May 10, 2007 |
EXPANDABLE ELECTODE DEVICES AND METHODS OF TREATING BRONCHIAL
TUBES
Abstract
Methods are provided for treating collapsed bronchial tubes
found in patients with chronic obstructive pulmonary diseases, such
as asthma. The method includes heating the bronchial tube to cause
tissue in the wall of the bronchial tube to undergo a structural
transformation effective to render the wall capable of supporting a
non-collapsed lumen. The procedure effectively reinforces the
structural integrity of the bronchial tube wall and thereby
prevents the lumen from collapsing.
Inventors: |
Laufer; Michael D.; (Menlo
Park, CA) ; Burger; Keith M.; (San Francisco, CA)
; Loomas; Bryan E.; (Los Gatos, CA) ; Tanaka; Don
A.; (Saratoga, CA) |
Correspondence
Address: |
ASTHMATX, INC.;c/o LEVINE BAGADE HAN, LLP
2483 EAST BAYSHORE ROAD
SUITE 100
PALO ALTO
CA
94303
US
|
Assignee: |
Asthmatx, Inc.
Mountain View
CA
|
Family ID: |
23373636 |
Appl. No.: |
11/612620 |
Filed: |
December 19, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10232909 |
Aug 30, 2002 |
|
|
|
11612620 |
Dec 19, 2006 |
|
|
|
09349715 |
Jul 8, 1999 |
6488673 |
|
|
10232909 |
Aug 30, 2002 |
|
|
|
09260401 |
Mar 1, 1999 |
6283988 |
|
|
09349715 |
Jul 8, 1999 |
|
|
|
09003750 |
Jan 7, 1998 |
5972026 |
|
|
09260401 |
Mar 1, 1999 |
|
|
|
08833550 |
Apr 7, 1997 |
6273907 |
|
|
09003750 |
Jan 7, 1998 |
|
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|
08994064 |
Dec 19, 1997 |
6083255 |
|
|
10232909 |
|
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Current U.S.
Class: |
606/50 ; 606/46;
607/101 |
Current CPC
Class: |
A61B 18/08 20130101;
A61M 25/0043 20130101; A61M 2210/1039 20130101; A61B 2017/22062
20130101; A61B 18/00 20130101; A61B 18/1492 20130101; A61B 18/14
20130101; A61M 29/02 20130101; A61N 1/06 20130101; A61B 2018/00214
20130101; A61B 2017/00115 20130101; A61B 2018/044 20130101; A61N
1/403 20130101; A61B 2018/1807 20130101; A61B 2018/00541 20130101;
A61M 2025/0096 20130101; A61B 2018/1407 20130101; A61B 2018/046
20130101 |
Class at
Publication: |
606/050 ;
606/046; 607/101 |
International
Class: |
A61B 18/18 20060101
A61B018/18 |
Claims
1. A method for treating an air passage in a lung, the method
comprising: delivering energy to an air passage in a lung to heat
the air passage to cause a structural transformation resulting in
improved lung function.
2. The method of claim 1, wherein the structural transformation
comprises rendering the air passage capable of supporting a
non-collapsed lumen such that air flow through the lumen
increases.
3. The method of claim 1, wherein the structural transformation
resulting in improved lung function ameliorates the effects of
asthma.
4. The method of claim 1, wherein delivering energy to the air
passage comprises heating the air passage to a temperature in a
range between 60.degree. C. and 95.degree. C.
5. The method of claim 1, wherein delivering energy to the air
passage comprises delivering between 1 watt to 25 watts of energy
to the air passage.
6. The method of claim 1, wherein energy is delivered for a time
period in a range between 1 second to about 60 seconds.
7. A method of treating asthma, the method comprising: advancing a
treatment apparatus into a lumen of an air passage in a lung;
expanding the apparatus to contact a wall of the air passage; and
energizing the apparatus to raise a temperature of the wall
sufficiently to cause the air passage to undergo a structural
transformation effective to treat asthma.
8. The method of claim 7, wherein advancing further comprises
inserting the apparatus through a working channel of a
bronchoscope.
9. The method of claim 7, wherein energizing the apparatus
comprises applying monopolar or bipolar radio frequency energy.
10. The method of claim 7, wherein energizing the apparatus
comprises simultaneously or sequentially activating electrodes.
11. The method of claim 7, further comprising monitoring a
temperature or impedance of the air passage wall while delivering
energy to the airway passage.
12. A device for delivering radio frequency energy to a wall of an
air passage of a lung so as to treat asthma, the device comprising:
a tubular member having a proximal end, a distal end, and a lumen
extending therebetween; a plurality of expandable radio frequency
electrodes attached to the distal end of the tubular member and
terminating at a distal tip, each of the electrodes having an
insulated sleeve and an exposed contact region; and a deployment
member attached to the distal tip and positioned in the lumen of
the tubular member, the deployment member configured to move the
expandable electrodes between a collapsed and a radially expanded
configuration, wherein the electrode contact regions are configured
to contact a wall in an air passage in a lung when in the expanded
radial configuration and which when energized causes the air
passage to undergo a structural transformation effective to treat
asthma.
13. The device of claim 12, wherein the electrodes comprise wire
shaped electrodes.
14. The device of claim 12, wherein the electrodes comprise four
curved electrodes.
15. The device of claim 12, wherein the exposed contact region is
located midway between a first and second end of each
electrode.
16. An energy delivery system comprising: the device of claim 12;
and a bronchoscope having an illumination element, a visualization
element, and a working channel for slidably receiving the
device.
17. The system of claim 16, further comprising a source of energy
electrically connected to the electrodes for the delivery of
monopolar or bipolar energy.
Description
REFERENCE TO RELATED APPLICATION
[0001] This is a continuation application of U.S. application Ser.
No. 10/232,909, filed Aug. 30, 2002, which is a continuation of
U.S. application Ser. No. 09/349,715, filed Jul. 8, 1999 now U.S.
Pat. No. 6,488,673, which is a continuation-in-part application of
U.S. application Ser. No. 09/260,401 filed Mar. 1, 1999 now U.S.
Pat. No. 6,283,988, which is a continuation-in-part of U.S.
application Ser. No. 09/003,750 filed Jan. 7, 1998 now U.S. Pat.
No. 5,972,026, which is a continuation-in-part of U.S. application
Ser. No. 08/833,550, filed Apr. 7, 1997 now U.S. Pat. No.
6,273,907; U.S. application Ser. No. 09/349,715 is also a
continuation-in-part of U.S. application Ser. No. 08/994,064, filed
Dec. 19, 1997 now U.S. Pat. No. 6,083,255, each of which is
incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a device and method for
treatment of the airway obstruction found in chronic obstructive
pulmonary diseases (COPD), such as cystic fibrosis, chronic
bronchitis, emphysema, and asthma.
BACKGROUND OF THE INVENTION
[0003] Chronic obstructive pulmonary diseases (COPD), which include
such entities as cystic fibrosis, chronic bronchitis, emphysema,
and asthma are steadily increasing in frequency, possibly due to
continued smoking, increasing air pollution, and the continued
aging of the population. COPD is characterized by edema of the
mucous membranes, which line the interior walls of the
tracheobronchial tree. When the mucosa accumulates an abnormal
quantity of liquid, the profuse and thickened serous fluid excreted
may seriously affect ventilation in the alveoli. The mucus resists
movement up the walls of the tracheobronchial tree, normally
efficiently accomplished by the cilia throughout the airways which
are also destroyed. Consequently, the serous fluid can form mucus
plugs, which can shut off alveoli or entire airways. in addition to
secretion accumulation, airway obstruction can occur because the
tubes collapse due to destruction of connective tissue. This
reduces the ability to get oxygen into the blood and carbon dioxide
out of the blood.
[0004] Asthma is the most common form of bronchoconstrictive
disease and pathologically involves constriction of the
bronchioles, hypertrophy of the muscles of the bronchioles, and a
characteristic infiltrate of eosinophils. Both asthma and other
COPI)s are characterized by the constriction or collapse of airway
passages in the lungs that are not supported by cartilage. This
condition is marked by labored breathing accompanied by wheezing,
by a sense of constriction in the chest, and often by attacks of
coughing and gasping.
[0005] Individuals who are afflicted may attempt to compensate by
blowing harder only to have the airways collapse further. A person
with poor resulting ventilation suffers from a number of metabolic
conditions including accumulation of carbon dioxide. These
individuals also often have hyperinflated enlarged lungs and
barrel-shaped chests.
[0006] A wide variety of drugs are available for treating the
symptoms of COPD but none is curative. Cystic fibrosis, chronic
bronchitis, and emphysema are typically treated with agents to thin
and dry up the secretions and with antibiotics to combat infection
and with bronchodilators. These drugs include potassium iodide,
antihistamines, various antibiotics, beta agonists, and
aminophylline. Unfortunately, a large number of patients are not
responsive to these medications or become non-responsive after
prolonged periods of treatment. For severe cases involving
collapsed air passages, surgeons have endeavored to alleviate this
disabling condition by either removing a portion of the lungs or
constricting the volume of lung available for respiration by
stapling off sections thereof. The result is that functionally the
diaphragm and muscles in the chest wall operate on a smaller lung
volume which may improve air movement for some individuals. These
operations are quite risky and are associated with a large number
of deaths. Patients undergoing these treatments are quite ill and
these procedures are considered final options.
[0007] Notwithstanding the conventional treatments available, there
exists a need in the art for an effective treatment for chronic
obstructive pulmonary diseases, such as cystic fibrosis, chronic
bronchitis, emphysema, and asthma. Specifically, there is a need
for effective treatment for individuals with obstructed airway
passages to restore pulmonary function which only requires minimal
surgery.
SUMMARY OF THE INVENTION
[0008] Many types of tissue can be molded and remodeled to correct
defects and dysfunction. One technique involves physical
manipulation using mechanical instruments and/or balloons to effect
selective shrinking, stretching, flattening, thinning, or
thickening in addition to changing the material properties of the
tissue. These changes of properties include alteration of the
elastic coefficient of the tissue causing it to be stiffer,
changing the tensile strength of the tissue, changing the shear
strength of the tissue, and changing the floppiness or resiliency
of the tissue. When the tissue is close to the surface of the skin
or part of a non-critical organ, physical manipulation is feasible
and can be executed with minimal trauma to the patient. However,
when the tissue is in an internal organ, in particular, in the
lungs or other vital organ, molding and remodeling by physical
manipulation can involve complicated and often risky surgery.
[0009] The present invention is based, in part, on the development
of a heat treatment apparatus having expandable electrodes that are
capable of delivering energy to bronchial tubes uniformly. The heat
is preferably inductively applied by directing electromagnetic
energy, such as radio frequency, into the tissue to keep the
bronchial tubes open.
[0010] In accordance with one aspect of the present invention, a
method for treating a bronchial tube includes the steps of:
[0011] a) maneuvering a heating apparatus into a lumen of the
bronchial tube;
[0012] b) heating tissue of the bronchial tube to cause tissue in a
wall of the lumen to undergo a structural transformation effective
to render the wall capable of supporting the lumen without
collapsing; and
[0013] c) removing the apparatus from the bronchial tube.
[0014] Prior to treatment, the lumen can be non-collapsed,
partially, or fully collapsed. Preferably, the bronchial tube is
heated to a temperature in the range of about 60.degree. C. to
about 95.degree. C. for about 0.1 to about 600 seconds. With the
inventive procedure, extensive surgery and the accompanying trauma
are avoided.
[0015] This invention is particularly useful for treating subjects
experiencing difficulty in breathing as a result of obstructed
airway passages caused by, for example, chronic obstructive
pulmonary disease, including, for example, cystic fibrosis, chronic
bronchitis, emphysema, and asthma. This invention ameliorates the
affects of these diseases by improving lung function by keeping the
airway passages open. Specifically, the present invention provides
a device and method for effecting changes in soft tissue in the
bronchial tubes or air passages of the lungs which have collapsed.
The causes of the collapse may be the destruction of the connective
tissue, the disease process, swelling, and/or muscle-dependant
constriction. The invention is directed to a treatment process
which effectively creates an internal bronchial stent which
prevents the air passages from collapsing.
[0016] In one aspect, the invention is directed to an apparatus for
treating a bronchial tube having a lumen, which includes:
[0017] a tubular member having a lumen;
[0018] an elongated shaft that is at least partially slidably
positioned in the lumen of the tubular member;
[0019] at least one electrode supported by the elongated shaft,
which when energized causes tissue in the wall of the bronchial
tube to undergo a structural transformation effective to render the
wall capable of supporting the bronchial tube in a non-collapsed
configuration, wherein the at least one electrode is pivotally
mounted on the elongated shaft and expandable radially outward to
contact the wall of the bronchial tube; and
[0020] a source of energy electrically connected to the at least
one electrode.
[0021] In another aspect, the invention is directed to a method of
treating a bronchial tube comprising a lumen of an individual that
includes the step of: advancing the above described treatment
apparatus into the lumen of the bronchial tube; and activating the
treatment device to raise the temperature of the wall to
sufficiently effect a structural transformation in the tissue of
the wall.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] As used herein, like reference numerals will designate
similar elements in the various embodiments of the present
invention wherein:
[0023] FIG. 1 is a schematic side view of one embodiment of a heat
treatment apparatus of the present invention which employs two
collapsible and retractable electrodes;
[0024] FIG. 2 is an enlarged partial cross sectional view of a
distal end of another embodiment of a heat treatment having one
collapsible electrode;
[0025] FIG. 3 is a side cross sectional view of an alternative
embodiment of a heat treatment device having two wire shape
electrodes;
[0026] FIG. 4 is a side cross sectional view of the device of FIG.
3 in an enlarged state within a bronchial tube;
[0027] FIG. 5 is a side cross sectional view of an alternative
embodiment of a heat treatment device with four electrodes in an
enlarged state within a bronchial tube;
[0028] FIG. 5A is an end view of the device of FIG. 5;
[0029] FIG. 6 is a side cross sectional view of an alternative
embodiment of a heat treatment apparatus with a loop shaped
electrode in a contracted state;
[0030] FIG. 7 is a side cross sectional view of the apparatus of
FIG. 6 with the electrode in an expanded state within a bronchial
tube;
[0031] FIG. 8 is a side cross sectional view of an alternative
embodiment of the invention with a plate shaped electrode in a
contracted state;
[0032] FIG. 9 is an end view of the apparatus of FIG. 8 in the
contracted state;
[0033] FIG. 10 is a side cross sectional view of the apparatus of
FIG. 8 with the plate shaped electrodes in an expanded
configuration; and
[0034] FIG. 11 is an end view of the expanded apparatus of FIG.
10.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] FIG. 1 shows a first embodiment of a heat treatment
apparatus 10 which is introduced through a catheter, bronchoscope,
or other tubular introducer member 12. The heat treatment apparatus
includes a shaft 14 and one or more electrodes 16. Electrically
connected to the electrodes 16 is an RF generator 18 or other
energy source. The RF generator is controlled by a controller 20.
Although the invention will be described as employing an RF
generator, other energy sources, such as alternating current and
microwave may also be used.
[0036] In accordance with the embodiment of FIG. 1, the electrodes
include a first conical electrode 16A connected to an inner shaft
22 and a second conical electrode 16B connected to an outer shaft
24. The conical electrodes 16A, 16B are positioned with their axes
aligned and may be fixed or movable with respect to each other.
Each of the conical electrodes 16A, 16B, includes at least two
overlapping sections 26. The sections 26 are flexible and overlap
one another to allow the electrodes 16A, 16B to be compressed
within the lumen of the catheter 12 for insertion into the
bronchial tube of a patient. Once the catheter 12 is positioned
with a distal end at a desired treatment location within the
bronchial tubes, the shaft 14 is used to push the electrodes 16A,
16B out of the distal end of the catheter. Once deployed from the
catheter 12 the electrodes 16A, 16B expand radially outwardly until
the distal ends of the electrodes contact the walls of the
bronchial tube.
[0037] The electrodes 16A, 16B are electrically connected to the RF
generator 18 by electrical cables 28, 30. When the heat treatment
apparatus 10 employs two electrodes 16A, 16B the two electrodes are
preferably oppositely charged with one of the electrodes connected
to a negative output of the RF generator and the other electrode
connected to a positive output of the RF generator. Alternatively,
both the electrodes 16A, 16B or a single electrode 16 may be
connected to the same output of the RF generator and an external
electrode 34 may be used. The external electrode 34 is connected to
an output of the RF generator 18 having an opposite polarity of the
output connected to the internal electrode 16.
[0038] The present invention is based in part on the discovery that
the structural integrity of bronchial tubes, especially those which
do not have significant amounts of cartilage present, can be
significantly recreated by subjecting the bronchial tube to a
sufficient amount of heat to cause at least a portion of the soft
tissue to undergo a structural transformation thereby causing the
tubes to remain patent. This structural transformation may be due
to a variety of sources such as, scar tissue buildup, collagen
restructuring, or the like. This heating procedure changes the
structure of the tissue and the shape of the tube.
[0039] As used herein, the term "bronchial tube" or "air passage"
refers to the sub-segments that branch from the main stem bronchus
of the lungs. The term "collapsed lumen" refers to a condition of
lumen of a bronchial tube wherein the lumen is occluded to the
extent that substantial blockage of air flow through the lumen
exists. The diameter of a non-collapsed lumen may be substantially
equal to that of a normal bronchial tube or may be less as in the
case of a partially collapsed but functional lumen. It is
understood that the term "collapsed lumen" encompasses partially
collapsed lumens. Cartilage is not present around these air
passages in appreciable amounts so they have little intrinsic
supportive structures.
[0040] FIG. 2 shows an alternative embodiment of a heat treatment
apparatus 40 having a single electrode 16 positioned on a shaft 14.
The electrode 16 is shown as it is deployed from the distal end of
a catheter 12 for heat treatment of the lumen of bronchial
tubes.
[0041] The electrodes 16 of the embodiment of FIGS. 1 and 2 are
formed of a suitable conductive material such as metal, plastic
with a metal coating, or the like. The two or more sections 26 of
each of the cone shaped electrodes is fixed to the shaft 14 and
biased outwardly so that the sections expand or unfold to an
enlarged diameter upon release from the distal end of the catheter
12. The electrodes 16 preferably have an enlarged diameter which is
equal to or slightly greater than an interior diameter of the
bronchial tube to be treated. As shown most clearly in FIG. 2, the
sides of the sections 26 overlap one another even in the expanded
state.
[0042] In operation of the embodiments of FIGS. 1 and 2, the distal
end of the catheter 10 is first positioned at the treatment site by
known catheter tracking methods. The catheter 10 is then retracted
over the heat treatment apparatus to exposed and expand the
electrodes 16. Each electrode 16 of the energy emitting apparatus
10 expands radially outward upon retraction of the catheter 12
until the electrodes come into contact with the wall of the
bronchial tube. In the embodiment of FIG. 2, the distance between
the two energy emitting electrodes 16A, 16B may be fixed or may be
changeable by sliding the inner shaft 22 within the outer shaft 24.
When treatment is completed the heat treatment apparatus 10 is
retracted back inside the catheter 12 by sliding the catheter over
the electrodes. As the heat treatment apparatus 10 is retracted the
sides of the sections 26 of the electrode 16 slide over each other
upon coming into contact with a distal edge of the catheter 12.
[0043] FIGS. 3 and 4 illustrate an alternative embodiment of a heat
treatment apparatus 50. The heat treatment apparatus may be
delivered to a treatment site in a collapsed configuration
illustrated in FIG. 3. The heat treatment apparatus 50 includes two
leaf spring or wire shaped electrodes 54A and 54B. The electrodes
54A, 54B are connected to an insulating end cap 56 of a hollow
shaft 58. The electrodes 54A, 54B are electrically connected to the
RF generator or other energy source by electric cables 60, 62. The
heat treatment apparatus 50 is provided with a central shaft 64
which is slidable within the hollow shaft 58. The central shaft 64
has a shaft tip 48 which is connected to a distal end of each of
the electrodes 54A, 54B.
[0044] Each of the electrodes 54A, 54B is preferably insulated with
an insulating sleeve 66 except for an exposed contact section 68.
The heat treatment apparatus 50 is delivered to the lumen of a
bronchial tube to be treated either alone or through a catheter,
bronchoscope, or other channel. The electrodes 54A, 54B are
expanded radially outwardly by moving the central shaft 64
proximally with respect to the hollow shaft 58 of the heat
treatment apparatus 50. Upon expansion, the exposed contact
sections 68 of the electrodes 54A, 54B come into contact with the
walls of the bronchial tube B, shown in FIG. 4. The electrodes 54A,
54B may be configured to bend at a predetermined location forming a
sharp bend as shown in FIG. 4. Alternatively, the electrodes 54A,
54B may form a more gradual curve in the expanded configuration.
The electrodes 54A, 54B are preferably connected to opposite poles
of the energy source. Alternatively, both of the electrodes 54A,
54B may be connected to the same lead of the energy source and the
external electrode 34 may be used. Upon completion of the treatment
process the electrodes 54 are retracted back into the catheter for
removal or moving to a subsequent treatment site.
[0045] FIGS. 5 and 5a illustrate an alternative embodiment of the
invention in which the heat treatment apparatus 50 includes four
electrodes 54A, 5413, 54C, 54D. The four electrode embodiment of
FIGS. 5 and 5a operates in the same manner as the embodiments of
FIGS. 3 and 4 with a slidable central shaft 64 employed to move the
electrodes from a compressed configuration to the expanded
configuration illustrated in FIGS. 5 and 5a. Each electrode 54A-54D
is connected at a proximal end to the insulating end cap 56 of the
hollow shaft 58 and at a distal end to the central shaft 64.
Relative motion of the hollow shaft 58 with respect to the central
shaft 64 moves the electrodes 54 from the collapsed to the expanded
position.
[0046] FIGS. 6 and 7 illustrate a further embodiment of a heat
treatment apparatus 90 employing one or more wire or leaf spring
shaped loop electrodes 94. As in the previous embodiments, the loop
electrode 94 expands from a contracted positioned within a catheter
92 as illustrated in FIG. 10 to an expanded position illustrated in
FIG. 7. In the expanded position, the loop shaped electrode 94
comes into contact with the walls of the bronchial tube B. Although
the embodiment of FIGS. 6 and 7 has been illustrated with a single
loop shaped electrode 94, it should be understood that multiple
loop shaped electrodes may also be use. The loop shaped electrode
92 is connected to the shaft 96 of the heat treatment apparatus 90
by an end cap 98 and is electrically connected to the energy source
by the electric cables 100.
[0047] FIGS. 8-11 illustrate an alternative embodiment of a heat
treatment apparatus 110 having a flexible plate shaped electrode
114. The flexible plate shaped electrode 114 is substantially
flower shaped in plan having a plurality of petals 116 with curved
distal ends extending from a central section 120. The petals 116
flex along a hinge line 118 to the compressed insertion
configuration illustrated in FIG. 8 in which the petals 116 extend
substantially perpendicularly from the central section 120 of the
flexible plate shaped electrode 114.
[0048] As illustrated in FIGS. 10 and 11, when the heat treatment
apparatus 110 is moved distally with respect to the catheter 112 to
deploy the electrode 114 the petals 116 move outwardly until the
petal tips come into contact with the walls of the bronchial tube
B. The flexible plate shaped electrode 114 is preferably formed of
a conductive material and fixed to the end of a shaft 122. Electric
cables 124 connect the plate shaped electrode 114 to the energy
source.
[0049] The electrodes in each of the forgoing embodiments may be
fabricated of any material which when compressed will return to an
expanded configuration upon release of the compression forces. For
example, one method of controlling the expansion of the electrodes
is the use of shape memory alloy electrodes. With a shape memory
alloy, the constraint of the electrodes within a catheter may not
be necessary. The shape memory alloy electrodes may be formed to
expand to an expanded energy delivery configuration upon heating to
body temperature within the body. The expansion of the electrodes
is limited by the size of the bronchial tube in which the electrode
is positioned.
[0050] The heat treatment apparatus according to the present
invention may be employed in a bipolar mode in which two different
expandable electrodes are connected to two different outputs of the
RF generator 18 having opposite polarities. For example, the
electrodes 16A, 16B may be connected by the electrical cables 28,
30 to different terminals of the RF generator 18. Alternatively,
when more than two electrodes 16 are employed, multiple electrodes
may be connected to one terminal of the RF generator. In each of
the embodiments of the heat treatment apparatus, the oppositely
charged electrodes are separated by an insulating material. For
example, in the embodiment of FIG. 1, the inner shaft 22 and outer
shaft 24 are formed of an insulating material. Further, in the
embodiments of FIGS. 3-5 the end cap 56 and central shaft distal
tip 82 are formed of insulating materials.
[0051] In the case where the apparatus includes only one electrode
16 as shown in FIG. 2, the electrode will be connected to the
positive or negative terminal of the RF generator 18 and the
opposite terminal of the RF generator will be connected to the
external electrode 32.
[0052] The frequency range of RF radiation useful in the present
invention is typically about 10 KHz to about 100 MHz, preferably in
the range of about 200 KHz to about 800 KHz. However, frequencies
outside this range may be used at the discretion of the operating
surgeon. Typically, the amount of power employed will be from about
0.01 to 100 watts and preferably in the range of about 1 to 25
watts for about 1 to 60 seconds. Alternatively, alternating current
or microwave radiation typically in the frequency range of about
1,000 MHz to about 2,000 MHz and preferably from about 1, 100 MHz
to about 1,500 MHz may be used in place of RF radiation. In the
latter case, the RF generator 18 is replaced with a microwave
generator, and the electric cables 28, 30 are replaced with
waveguides.
[0053] When the heat treatment apparatus with the bipolar
electrodes is positioned inside the lumen of a bronchial tube,
activation of the RF generator 18 causes tissue in the lumen wall
to increase in temperature. The heating may be caused by resistance
heating of the electrodes themselves and/or power losses through
the tissue of the bronchial wall. The particular heat pattern in
the tissue will depend on the path of the electric field created by
the positioning and configuration of the electrodes.
[0054] In the monopolar mode, the external electrode 34, shown in
FIG. 1, having a much larger surface area than the inner electrodes
is placed on the outer surface of the patient's body. For example,
the external electrode 34 can be an external metal mesh or a solid
plate that is placed on the skin. Both the internal and external
electrodes are connected to the RF generator 18 which produces an
electric field at a high frequency. Because the collective surface
area of the internal electrodes is much smaller than that of the
outer electrode 34, the density of the high frequency electric
field is much higher around the internal electrodes. The electric
field reaches its highest density in the region near the internal
electrodes. The increased density of the field around the internal
electrodes produces localized heating of the tissue around the
bronchial tube without causing significant heating of the body
tissue between the bronchial tube and the external electrode.
[0055] In use, after the operating surgeon has placed the heat
treatment apparatus within the lumen of a bronchial tube to be
treated, if necessary, the catheter is retracted to expose the
electrodes. In the case where the lumen of the bronchial tube has
collapsed or is partially collapsed, the size of the energy
emitting device is designed so that expansion of the electrodes
causes the lumen to expand to its normal or non-collapsed diameter
due to contact of the electrodes with the inner surface of the
lumen. Alternatively, in the case where the lumen has not
collapsed, the device is designed so that upon expansion the
electrodes are in substantial contact with the inner surface of the
lumen. Indeed, only minimum expansion may be necessary in treating
a non-collapsed bronchial lumen.
[0056] The degree of expansion of the electrodes of the heat
treatment apparatus can be monitored by means of endoscopy,
fluoroscopy, or by other suitable imaging methods of the art.
Generally, the heat required is induced in the tissue of the
bronchial tube wall by the RF or microwave radiation emitting from
the electrodes. The RF or microwave energy is applied while
observing the tissue for changes via simultaneous endoscopy, or
other suitable imaging methods of the art.
[0057] As is apparent, the inventive heat treatment apparatus can
be employed to treat a bronchial tube regardless of whether the
tube lumen has collapsed or not. Specifically, the devices can be
used to treat bronchial tubes that have not collapsed, are
partially collapsed, or are fully collapsed. Moreover, bronchial
tubes may exhibit different degrees of closure depending on the
state of respiration. For example, a bronchial tube may have a
fully expanded lumen after inhalation but partially or completely
closed during exhalation.
[0058] The electrodes employed in the present invention are
constructed of a suitable current conducting metal or alloys such
as, for example, copper, steel, platinum, and the like or of a
plastic material with a conductive metal insert. The electrodes can
also be constructed of a shape memory alloy which is capable of
assuming a predetermined, i.e., programmed, shape upon reaching a
predetermined, i.e., activation temperature. Such metals are well
known in the art as described, for example, in U.S. Pat. Nos.
4,621,882 and 4,772,112 which are incorporated herein by reference.
For the present invention, the shape memory metal used should have
the characteristic of assuming a deflection away (i.e., expands)
from the elongated rod when activated, i.e., heated in excess of
the normal body temperature and preferably between 60.degree. C.
and 95.degree. C. A preferred shape memory alloy is available as
NITINOL from Raychem Corp., Menlo Park, Calif. In one embodiment,
the electrodes are constructed of NITINOL in a predetermined shape
and in the alloy's super elastic phase which can withstand very
large deflections without deformation.
[0059] The function of the heat treatment apparatus is to apply a
sufficient amount of energy to the walls of air passages to cause
tissue in the walls to undergo a structural transformation to
create more rigid walls that can support a non-collapsed, patent
lumen. RF energy is no longer applied after there has been
sufficient transformation, e.g., shrinkage, of the tissue fibers
which may be gauged by removing the heating device from the
treatment site and visually determining whether the lumen remains
noncollapsed. Sufficient shrinkage may also be detected by
fluoroscopy, external ultrasound scanning, pulse-echo ultrasound
scanning, sensing the collapsing or straightening of the heating
element with appropriate feedback variables, impedance monitoring
or any other suitable method.
[0060] Substantial tissue transformation may be achieved very
rapidly, depending upon the specific treatment conditions. Because
the transformation can proceed at a rather rapid rate, the RF
energy should be applied at low power levels. Preferably, the RF
energy is applied for a length of time in the range of about 0.1
second to about 600 seconds, and preferably about 1 to about 60
seconds. Suitable RF power sources are commercially available and
well known to those skilled in the art. In one embodiment the RF
generator 18 employed has a single channel, delivering
approximately 1 to 100 watts, preferably 1 to 25 watts, and most
preferably 2 to 8 watts of RF energy and possessing continuous flow
capability. The rate of collagen transformation can be controlled
by varying the energy delivered to the heat treatment device.
Regardless of the source of energy used during treatment, the lumen
or the bronchial tube is maintained at a temperature of at least
about 45.degree. C., preferably between .degree. C. and 95.degree.
C. and more preferably between 70.degree. C. and 85.degree. C.
[0061] When the heat treatment apparatus includes multiple energy
emitting devices, not all the electrodes need to be activated at
the same time, that is, different combinations of electrodes can be
employed sequentially. For example, in the case of the embodiment
shown in FIG. 1, with two electrodes 16A, 16B, the electrodes can
be activated simultaneously or sequentially.
[0062] In addition, when a heat treatment apparatus includes
multiple energy emitting devices, the apparatus can operate in the
monopolar, bipolar mode, or both modes at the same time. For
instance, one of the electrodes can be designed to operate in the
bipolar mode while another electrode operates in the monopolar
mode.
[0063] When treating a person with obstructed air passages, a
preliminary diagnosis is made to identify the air passages or
bronchial tube that can be treated. In treating a particular site,
excessive fluid is first removed from the obstructed air passage by
conventional means such as with a suction catheter. Thereafter, the
inventive heat treatment device is maneuvered to the treatment
site. Depending on the diameter of the lumen of the bronchial tube,
the device can be positioned directly at the treatment site or it
can be positioned into place with a bronchoscope. The elongated
shafts 22, 24 and outer catheter 12 are preferably made of a
flexible material so that the catheter can be maneuvered through a
bronchoscope. A bronchoscope is a modified catheter which includes
an illuminating and visualization instrument for monitoring the
treatment site and a channel for passing instruments (e.g., the
treatment device) into the bronchial tubes.
[0064] In operation, the bronchoscope is advanced from the person's
nasal or oral cavity, through the trachea, main stem bronchus, and
into an obstructed air passage. The heat treatment apparatus is
advanced forward through the bronchoscope to expose the tip of the
heat treatment device before the treatment device is energized.
Depending on the size of the treatment device, the treatment device
can be moved to another position for further heat treatment of the
air passage. This process can be repeated as many times as
necessary to form a series of patency bands supporting an air
passage. This procedure is applied to a sufficient number of air
passages until the physician determines that he is finished. As is
apparent, the procedure can be completed in one treatment or
multiple treatments. After completion of the treatment, energy is
discontinued and the treatment device is removed from the
patient.
[0065] The heating apparatus can be made to provide protection
against overheating of the connective tissue which will cause the
collagen to denature. Temperature monitoring and impedance
monitoring can be utilized in a system which provides feedback to
the user in the form of sounds, lights, other displays or a
mechanism which shuts down the application of energy from the
heating element to the treatment site when sufficient tissue
transformation is detected and to avoid burning of the treatment
site. The amount of energy applied can be decreased or eliminated
manually or automatically under certain conditions. For example,
the temperature of the wall of the air passage, or of the heating
element can be monitored and the energy being applied adjusted
accordingly. The surgeon can, if desired, override the feedback
control system. A microprocessor can be included and incorporated
into the feedback control system to switch the power on and off, as
well as to modulate the power. The microprocessor can serve as a
controller to monitor the temperature and modulate the power.
[0066] The invention is also directed to the demonstration or
instruction of the inventive surgical techniques including, but not
limited to, written instructions, actual instructions involving
patients, audio-visual presentations, animal demonstrations, and
the like.
[0067] While the invention has been described in detail with
reference to the preferred embodiments thereof, it will be apparent
to one skilled in the art that various changes and modifications
can be made and equivalents employed, without departing from the
present invention.
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