U.S. patent application number 10/738066 was filed with the patent office on 2004-07-08 for heat transfer catheter with elastic fluid lumens.
This patent application is currently assigned to Radiant Medical, Inc.. Invention is credited to Callister, Jeffrey P..
Application Number | 20040133256 10/738066 |
Document ID | / |
Family ID | 25360359 |
Filed Date | 2004-07-08 |
United States Patent
Application |
20040133256 |
Kind Code |
A1 |
Callister, Jeffrey P. |
July 8, 2004 |
Heat transfer catheter with elastic fluid lumens
Abstract
The heat exchange catheters comprise a catheter body having a
heat exchange structure formed over a distal region thereof. Heat
exchange structure comprises an elastic chamber or balloon which
conforms closely to the catheter body when uninflated and which
expands to enhance the available heat transfer surface when heat
exchange medium is introduced. The elastic structures may consist
of elastomeric sheets or membranes or may comprise non-distensible
sheets or membranes having elastic elements in order to control
expansion and contraction. Methods for fabrication and use are also
disclosed.
Inventors: |
Callister, Jeffrey P.;
(US) |
Correspondence
Address: |
STOUT, UXA, BUYAN & MULLINS, LLP
Suite 300
4 Venture
Irvine
CA
92618
US
|
Assignee: |
Radiant Medical, Inc.
|
Family ID: |
25360359 |
Appl. No.: |
10/738066 |
Filed: |
December 17, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10738066 |
Dec 17, 2003 |
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10142659 |
May 8, 2002 |
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10142659 |
May 8, 2002 |
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09872818 |
May 31, 2001 |
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Current U.S.
Class: |
607/105 ;
607/113 |
Current CPC
Class: |
A61F 2007/0054 20130101;
A61F 7/123 20130101; Y02P 20/141 20151101; Y10T 428/24942 20150115;
A61F 2007/126 20130101 |
Class at
Publication: |
607/105 ;
607/113 |
International
Class: |
A61F 007/00; A61F
007/12 |
Claims
What is claimed is:
1. A heat exchange catheter comprising: a catheter body having a
proximal end and a distal region; and a heat exchange balloon
structure disposed over the distal region; wherein the heat
exchange balloon structure expands and deflates elastically when
uninflated.
2. A heat exchange catheter as in claim 1, wherein the heat
exchange balloon structure conforms without folding to the distal
region of the catheter body when uninflated.
3. A heat exchange catheter as in claim 1, wherein the heat
exchange balloon structure has a diameter when uninflated which
does not exceed that of the catheter body.
4. A heat exchange catheter as in claim 1, wherein the surface area
of the heat exchange balloon structure increases by at least 10%
when inflated by heat exchange medium at a pressure in the range
from 0.5 psig to 50 psig.
5. A heat exchange catheter as in claim 1, wherein the catheter
body comprises a polymeric material having a hardness in the range
from 75 A to 80 D.
6. A heat exchange catheter as in claim 4, wherein the catheter
body has a length in the range from 15 cm to 100 cm and a diameter
in the range from 1 mrn to 4 mm.
7. A heat exchange catheter as in any of claim 1 to 6, wherein the
heat exchange balloon structure comprises a polymeric material
having a hardness in the range from 65 A to 45 D.
8. A heat exchange catheter as in claim 6, wherein the polymeric
material is selected from the group consisting of polyurethanes,
silicone rubber, latex, polyvinyls, plasticized PVC, and
styrene-ethylene-butylene modified block copolymer with silicone
oil.
9. A heat exchange catheter as in claim 7, wherein the catheter
body and the balloon comprise the same material having different
hardnesses.
10. A heat exchange catheter as in claim 9, wherein the same
material is selected from the group consisting of polyurethanes,
silicone rubber, latex, polyvinyls, plasticized PVC, and
styrene-ethylene-butylene modified block copolymer with silicone
oil.
11. A heat exchange catheter comprising: a catheter body having a
proximal end, a distal region, an inflow lumen, and an outflow
lumen; and a heat exchange balloon structure comprising a plurality
of elastic polymeric chambers disposed over the distal region and
fluidly connected at an inlet end to the inflow lumen and at an
outlet end to the outflow lumen.
12. A heat exchange catheter as in claim 11, wherein the elastic
polymeric chambers are arranged axially over the distal region.
13. A heat exchange catheter as in claim 11, wherein the elastic
polymeric chambers are arranged spirally over the distal
region.
14. A heat exchange catheter as in any of claims 11-13, wherein the
heat exchange balloon structure comprises from two to twelve
elongated chambers.
15. A heat exchange catheter as in claim 14, wherein the elongated
chambers are circumferentially spaced apart.
16. A heat exchange catheter as in claim 11, wherein the heat
exchange balloon structure conforms without folding to the distal
region of the catheter body when uninflated.
17. A heat exchange catheter as in claim 11, wherein the heat
exchange balloon structure has a diameter when uninflated which
does not exceed that of the catheter body.
18. A heat exchange catheter as in claim 11, wherein the surface
area of the heat exchange balloon structure increases by at least
10% when inflated by heat exchange medium at a pressure in the
range from 0.5 psig to 50 psig.
19. A heat exchange catheter as in claim 11, wherein the catheter
body comprises a polymeric material having a hardness in the range
from 75 A to 80 D.
20. A heat exchange catheter as in claim 19, wherein the catheter
body has a length in the range from 15 cm to 100 cm and a diameter
in the range from 1 mm to 4 mm.
21. A heat exchange catheter as in any of claim 11 to 20, wherein
the heat exchange balloon structure comprises a polymeric material
having a hardness in the range from 65 A to 45 D.
22. A heat exchange catheter as in claim 21, wherein the catheter
body and the balloon comprise the same material having different
hardnesses.
23. A heat exchange catheter as in any of claim 11 to 12, wherein
the heat exchange balloon structure comprises a polymeric material
having a hardness in the range from 65 A to 45 D.
24. A heat exchange catheter comprising: a catheter body having a
proximal end, a distal region, an inflow lumen, and an outflow
lumen; and an elastomer tube coaxially positioned over the distal
region; wherein the elastomer tube is sealed to the catheter body
along a multiplicity of lines to define a plurality of separate
inflatable chambers, each at which is fluidly connected at an inlet
end to the inflow lumen and at an outlet end to the outflow
lumen.
25. A heat exchange catheter as in claim 24, wherein the inflatable
chambers are arranged axially over the distal region.
26. A heat exchange catheter as in claim 24, wherein the inflatable
chambers are arranged spirally over the distal region.
27. A heat exchange catheter as in claim 24, wherein the catheter
comprises from two to twelve inflatable chambers.
28. A heat exchange catheter as in claim 27, wherein the inflatable
chambers are circumferentially spaced apart.
29. A heat exchange catheter as in claim 24, wherein the heat
exchange balloon structure conforms without folding to the distal
region of the catheter body when uninflated.
30. A heat exchange catheter as in claim 24, wherein the heat
exchange balloon structure has a diameter when uninflated which
does not exceed that of the catheter body.
31. A heat exchange catheter as in claim 24, wherein the surface
area of the heat exchange balloon structure increases by at least
10% when inflated by heat exchange medium at a pressure in the
range from 0.5 psig to 50 psig.
32. A heat exchange catheter as in claim 24, wherein the catheter
body comprises a polymeric material having a hardness in the range
from 75 A to 80 D.
33. A heat exchange catheter as in claim 32, wherein the catheter
body has a length in the range from 15 cm to 100 cm and a diameter
in the range from 1 mm to 4 mm.
34. A heat exchange catheter as in any of claim 24 to 33, wherein
the heat exchange balloon structure comprises a polymeric material
having a hardness in the range from 65 A to 45 D.
35. A heat exchange catheter as in claim 34 wherein the catheter
body and the elastomer tube comprise the same material having
different hardnesses.
36. A heat exchange catheter as in any of claim 24 to 33, wherein
the heat exchange balloon structure comprises a polymeric material
having a hardness in the range from 65 A to 45 D.
37. A method for fabricating a catheter, said method comprising:
positioning a tubular catheter body over a mandrel, wherein said
catheter body has at least an inflow lumen and an outflow lumen;
placing an elastomer tube over a distal region of the catheter
body; attaching the elastomer tube to the tubular catheter body to
define a plurality of separate elastically expandable chambers
between the outside of the catheter body and the inside of the
elastomer tube, wherein an inlet end of the chamber is fluidly
connected to the inflow lumen and an outlet end of the chamber is
fluidly connected to the outflow lumen.
38. A method as in claim 37, wherein tubular catheter body
comprises a polymer having a hardness in the range from 75 A to 82
D and the elastomer tube comprises an elastomer having a hardness
in the range from 65 A to 45 D.
39. A method as claim 38, wherein the polymer is selected from the
group consisting of polyurethanes, silicone rubber, latex,
polyvinyls, plasticized PVC, and styrene-ethylene-butylene modified
block copolymer with silicone oil and the elastomer is selected
from the group consisting of polyurethanes, silicone rubber, latex,
polyvinyls, plasticized PVC, and styrene-ethylene-butylene modified
block copolymer with silicone oil (C-Flex.RTM.), polyurethanes.
40. A method as in claim 39, wherein the polymer and the elastomer
are the same material but have different hardnesses.
41. A method as in claim 37, wherein attaching comprises heat
staking.
42. A method as in claim 37 or 41, wherein attaching comprises
sealing along a multiplicity of lines to define the chambers
therebetween.
43. A method as in claim 42, wherein the lines are arranged
axially.
44. A method as in claim 42, wherein the lines are arranged
spirally.
45. A method as in claim 42, wherein the lines have a width in the
range from 0.01 mm to 2 mm to circumferentially separate adjacent
chambers.
46. A method for exchanging heat with vascular circulation of a
patient, said method comprising; percutaneously introducing a
catheter to a blood vessel of the patient, wherein the catheter
includes at least one elastic chamber conformed over a surface
thereof; elastically inflating the chamber with a heat exchange
medium, whereby heat is exchanged between the heat exchange medium
and the vascular circulation.
47. A method as in claim 46, wherein the catheter is introduced to
a blood vessel selected from the group consisting of a. the
inferior vena cava; b. the superior vena cave; c. a jugular vein;
d. a carotid artery; e. the aorta; and f. a renal artery.
48. A method as in claim 46, wherein the at least one chamber is
inflated with the heat exchange medium at a pressure in the range
from 0.5 psig to 50 psig and a flow rate in the range from 5 ml/min
to 1000 ml/min.
49. A method as in claim 46, wherein elastically inflating
comprises pulsing the pressure of the heat exchange medium, whereby
the surface of the elastic chamber moves in order to enhance heat
transfer.
50. A method as in claim 46, wherein pressure feedback from the
pressure of the heat exchange fluid is used to control the
expansion of the heat exchange balloon.
51. A method as in claim 46, wherein the flow rate feedback from
the heat exchange fluid is used to control the expansion of the
balloon.
52. A method as in claim 46, wherein the balloon is expanded to a
sized based on the size of the vessel in which the heat exchange
region is located.
53. A method as in claim 46, wherein the pulse rate of the
expansion/deflation cycle is controlled to optimize heat exchange
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of
application Ser. No. 09/872,818 (Attorney Docket No.
020878-000200), filed on May 31, 2001, the full disclosure of which
is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to medical apparatus
and methods. More particularly, the present invention relates to
the construction and use of heat exchange catheters having
elastically inflatable heat exchange surfaces.
[0004] Under ordinary circumstances, the thermoregulatory system of
the human body maintains a near constant temperature of about
37.degree. C. (98.6.degree. F.), a temperature referred to as
normothermia. For various reasons, however, a person may develop a
body temperature that is below normal temperature, a condition know
as hypothermia, or a temperature that is above normal temperature,
a condition known as hyperthermia. Hypothermia and hyperthermia are
generally harmful, and if severe, the patient is generally treated
to reverse the condition and return the patient to normothermia.
Accidental hypothermia significant enough to require treatment may
occur in patients exposed to overwhelming cold stress in the
environment or whose thermoregulatory ability has been lessened due
to injury, illness or anesthesia. For example, this type of
hypothermia sometimes occurs in patients suffering from trauma or
as a complication in patients undergoing surgery. Likewise,
examples of hyperthemnia include exposure to overwhelming exposure
to hot environmental stimulation, injury or illness, or
complications of anesthesia.
[0005] In certain situations, however, hyperthermia and especially
hypothermia may be desirable and may even be intentionally induced.
For instance, hypothermia is generally recognized as being
neuroprotective, and may, therefore, be induced in conjunction with
treatments for ischemic or hemorrhagic stroke, blood deprivation
such as caused by cardiac arrest, intracerebral or intracranial
hemorrhage, and head and spinal trauma. In each of these instances,
damage to neural tissue may occur because of ischemia, increased
intracranial pressure, edema or other processes, often resulting in
a loss of cerebral function and permanent neurological deficits.
Intentionally induced hypothermia may reduce or avoid the damage
that would otherwise occur if the patient temperature was
normothennic or hyperthermic.
[0006] Other examples where hypothermia may be neuroprotective
include periods of cardiac arrest in myocardial infarction and
heart surgery, neurosurgical procedures such as aneurysm repair
surgeries, endovascular aneurysm repair procedures, spinal
surgeries, procedures where the patient is at risk for brain,
cardiac or spinal ischemia such as beating heart by-pass surgery or
any surgery where the blood supply to the heart, brain or spinal
cord may be temporarily interrupted. Hypothermia has also been
found to be advantageous as a treatment to protect both neural
tissue and cardiac muscle tissue during or after a myocardial
infract (MI).
[0007] Body heating and cooling can be achieved in a variety of
ways. Body heating is most simply achieved by wrapping a patient in
blankets and/or heated jackets in order to raise body temperature
over time. Body cooling can be similarly achieved using cooling
jackets. The ability to cool patients using external cooling,
however, is problematic. Induced cooling will trigger a patient's
thermoregulatory responses, causing patient's body to generate more
heat in order to maintain body temperature. It has also been found
that external cooling can cause the patient to "shiver," and that
shivering not only causes discomfort but also induces the patient's
body to generate still more heat in response.
[0008] In order to overcome the deficiencies of external body
heating and cooling, it has been proposed to heat or cool blood in
a patient's circulation, thus effecting an internal modification of
body temperature. For example, it has been proposed to remove blood
in a patient, e.g., from the inferior vena cava, externally heat or
cool the blood, and then return the blood to patient circulation.
Such external cooling of patient blood is performed, for example,
during cardiopulmonary bypass surgery where the heart is stopped
and the blood is also oxygenated. Such external blood cooling,
however, suffers from a number of deficiencies. It is quite
invasive to the patient, is damaging to the blood (causing
significant hemolysis over time), generally must be performed in a
sophisticated operating room and by highly trained and expensive
medical specialists, and can only be performed for up to several
hours before it must be discontinued. Thus, external blood heating
or cooling is not appropriate for many circumstances.
[0009] Of particular interest to the present invention, an improved
method for adding or removing heat from patient circulation uses a
heat exchange catheter placed in the bloodstream of a patient, as
described in U.S. Pat. No. 5,486,208 to Ginsburg, the complete
disclosure of which is incorporated herein by reference. The
Ginsburg patent discloses a method of controlling the temperature
of a body by adding or removing heat to the blood by inserting a
heat exchange catheter having a heat exchange region into the
vascular system and exchanging heat between the heat exchange
region and the blood to affect the temperature of a patient. One
method disclosed for doing so includes inserting a catheter having
a heat exchange region comprising a balloon into the vasculature of
a patient and circulating warm or cold heat exchange fluid through
the balloon while the balloon is in contact with the blood. Other
patents and applications describing heat exchange catheters are
listed below.
[0010] Heretofore, the balloons of heat exchange catheters have
generally been formed from polyethylene terephthalate (PET) and
other substantially non-distensable materials, i.e., materials
which are essentially non-elastic and do not stretch when the
balloon is filled with heat exchange medium. Distensible or
elastomeric heat exchange structures, however, may have certain
advantages over non-distensible heat exchange structures in many
situations. For example, when the balloon is non-elastic, it needs
to be folded or otherwise constrained on the distal end of the heat
exchange catheter in order to facilitate introduction. After use
and deflection prior to withdrawal, the heat exchange balloon
becomes loose and floppy, rendering withdrawal of the catheter more
difficult. In its loose and floppy condition, it may be more prone
to damage upon withdrawal from the patient. Further, responsiveness
to various ranges of pressures is sometimes an advantage, for
example when pulsing or fluctuating motion desirable to induce
mixing for enhanced heat exchange in flowing fluid such as blood.
The control of size by control of pressure in the elastomeric heat
exchange structure may be an advantage, for example, when a range
of heat exchange surface sized can be obtained for different sized
patients using the same type of device by controlling the pressure
of the heat exchange fluid. Moreover, manufacturing of heat
exchange catheters with PET and other non-distensible balloon
materials may be more difficult and expensive than manufacturing
the device with elastomeric material.
[0011] For these reasons, it would be desirable to provide improved
heat exchange catheters, and in particular improved balloon
structures on such heat exchange catheters. Such balloon structures
will preferably conform closely to the exterior surface of the heat
exchange catheter when introduced and will return to such a closely
conforming configuration when withdrawn after use. Such balloon
structures should provide adequate or improved heat transfer
characteristics when compared with the PET and other
non-distensible balloon materials of prior art. Moreover, such
balloon structures should be fabricated from materials which are
bio-compatible and which induce little or no clot formation (are
non-thrombogenic). At least some of these objectives will be met by
the inventions described hereinafter.
[0012] 2. Description of the Background Art
[0013] Patents and published applications assigned to the assignee
of the present invention include U.S. Pat. Nos. 6,306,161;
6,264,679; 6,231,594; 6,149,676; 6,149,673; 6,110,168; 5,989,238;
5,879,329; and 5,837,003; U.S. Patent Publication US 2001/005791;
and Published PCT Applications WO 01/64164; WO 01/58397; WO
01/152781; WO 01/43661; WO 01/13809; WO 01/10323; WO 00/10494; WO
98/31312; and WO 98/26831. Other patents relating to body cooling
include U.S. Pat. Nos. 6,325,818; 6,312,452; 6,261,312; 6,254,626;
6,251,130; 6,251,129; 6,245,095; 6,238,428; 6,235,048; 6,231,595;
6,224,624; 6,149,677; 6,096,068; 6,042,559; 6,299,599; 6,290,717;
6,287,326; 6,165,207; 6,149,670; 6,146,411; 6,126,684; 6,019,703;
and 5,269,758. The full disclosures of each of these patents and
published applications are incorporated herein.
BRIEF SUMMARY OF THE INVENTION
[0014] This section describes what may be typical features and
characteristics of a medical device of the invention, but unless
the feature is specifically stated to be necessary, the references
are not limiting of the invention despite their inclusion in this
section.
[0015] The present invention provides improved heat exchange
catheters having elastic heat exchange structures, referred to
hereinafter as "balloons" or "chambers." The heat exchange
structures are elastically expansible so that they inflate or
enlarge when a suitable heat exchange medium, such as heated or
cooled saline, is introduced to the heat exchange structure under
pressure. The heat exchange medium will usually, although not
necessarily be non-compressible. The pressure-induced expansion
enlarges the heat exchange structure, thus increasing the surface
area of the heat exchange structure which is available for
transferring heat to or from the circulating blood in a patient's
vasculature.
[0016] Many aspects of the construction of the heat exchange
catheters may be conventional and may, for example, incorporate
many elements of the heat exchange catheters described in the
patents and applications, which have been incorporated by reference
above. For example, the heat exchange structures of the present
invention will be incorporated on a catheter body having a proximal
end, a distal region, and usually at least two fluid flow lumens
therethrough. The catheter body will be suitable for percutaneous
introduction to the patient's vasculature through a variety of
access sites, such as introduction into the femoral vein and
advancement into the inferior vena cave (IVC) or introduction into
one of the carotid veins or the subclavian vein and advancement
into the superior vena cava (SVC). Any other appropriate site may
be used; for example placement in the arterial vasculature may be
made by introduction into the femoral artery and advancement into
the aorta. Other placement as may be appropriate for the particular
purpose is within the contemplation of this patent, for example
into the renal arteries to cool the kidneys, into the hepatic
arteries to cool the liver or into the carotid arteries to cool the
bead or brain.
[0017] The catheter bodies will typically have a length in the
range from 15 cm to 100 cm, typically from 25 cm to 75 cm, and a
diameter from 1 mm to 4 mm, usually from 2 mm to 4 mm. The catheter
bodies will typically be formed from a relatively hard, non-elastic
polymer, typically having a hardness in the range from 75 A to 82
D, usually from 85 A to 72 D. Suitable polymeric materials include
polyurethanes, C-Flex.RTM., and the like. Specific catheter body
designs are disclosed, for example, in U.S. Pat. No. 6,264,679,
assigned to the assignee in the present application, and WO
00/10494, the full disclosures which are incorporated herein by
reference, as well as PCT application PCT/US01/03828, assigned to
the assignee in the present application, and WO 00/10494, the full
disclosures of which are incorporated herein by reference.
[0018] As used herein, the term "elastic" includes heat exchange
structures which are formed from a suitable elastomer, as well as
structures which are formed from non-elastomeric sheets or
membranes and which incorporate elastic reinforcement or
constraining materials so that the structures may elastically
expand and deflate as the heat exchange medium is introduced and
removed. Suitable elastomers will usually be softer and often
thinner than the material from which the catheter body has been
formed, but may be composed of the same polymeric resin. Suitable
elastomeric balloon or chamber materials will have hardness in the
range from 65 A to 45 D, usually from 75 A to 100 A. Suitable
elastomers include polyurethanes, silicone ruber, natural and
synthetic latex (although generally not preferred), polyvinyls,
plastisized PVC and the like. An exemplary and presently preferred
material is styrene-ethylene-butylene-modified block copolymer with
silicone oil, available under the C-Flex.RTM. tradename. The use of
a heat exchange structure material which is the same as (although
softer and more elastic than) the catheter body material is
advantageous since it facilitates heat sealing of the materials
together, as will be described in more detail below.
[0019] The catheter bodies of the heat exchange catheters of the
present invention will usually have at least two lumens to provide
for inflow and outflow of the heat exchange medium, respectively.
Optionally, additional lumens may be provided for supply of heat
exchange medium to different compartments within the heat exchange
structure or for other purposes.
[0020] In a first aspect of the present invention, heat exchange
catheters comprise a catheter body having a proximal end and a
distal end. A heat exchange balloon structure is disposed over the
distal region, and the balloon structure is constructed or composed
of the elastic material selected so that the structure initially
conforms to the distal region of the catheter body (preferably
without folding as is characteristic of non-distensible balloons
such as angioplasty balloons) and expands elastically in response
to the introduction of the heat exchange medium under pressure.
When the treatment is done, and the supply of the heat exchange
medium terminated, the heat exchange balloon structure will deflate
elastically so that it again conforms to the catheter body to
facilitate removal of the catheter. While the heat exchange
structures will be highly elastic, it will be appreciated that some
hysteresis, i.e., loss of the elasticity, is acceptable. It is
preferred, however, that the elongation of the balloon structure in
any one direction be less than 10% after use, preferably being less
than 0.5%.
[0021] Preferred balloons and other heat exchange structures will
be relatively small when deflated, having a diameter or width which
does not significantly exceed that of round catheter body. The
functional deflated cross-sectional size is sometimes called
profile. If the catheter is not round, this still gives a
functional measure of the size since this is the size of puncture
introducer hole that is necessary in order to insert the catheter.
Profile is generally measured in French size (Fr) with one Fr equal
to 0.33 mm. The Fr size of the preferred catheters including
balloons will generally be between 4 Fr and 14 Fr with a size
between about 6 Fr and 10 Fr being preferable. Generally, a smaller
French size for insertion is preferable to a larger size, and one
advantage of the elastomeric heat exchange region is the potential
of having a very large heat exchange surface when inflated despite
a small French size when deflated for insertion. When inflated at a
typical heat exchange medium pressure in the range from 0.5 psig to
50 psig, however, the heat exchange balloons or other structures
will have a surface area which is significantly greater, typically
increasing by at least 10% more typically by at least 25%.
[0022] In a second aspect of the present invention, the heat
exchange catheter comprises a catheter body having a proximal end,
a distal region, an inflow lumen, and an outflow lumen. The heat
exchange balloon or other structure comprises a plurality of
elastic polymer chambers disposed over the distal region and
fluidly connected at an inlet end to the inflow lumen and at an
outlet end to the outflow lumen. By dividing the inflow of heat
exchange medium among a plurality of heat exchange chambers, the
heat transfer rate can be improved. Polymeric chambers may be
arranged axially, helically, or in other patterns over the distal
region of the catheter body. The number of chambers may vary,
typically be in the range from two to twelve, usually from two to
eight, and preferably from four to eight. In order to further
enhance heat transfer, it is sometimes desirable to
circumferentially space-apart the axial or spiral chambers which
are formed over the distal region. The surface areas when inflated
and deflated, material properties, and other characteristics of
these catheters will generally be the same as described with
respect to the first embodiment of the catheter set forth
above.
[0023] In a third embodiment, a heat exchange catheter constructed
in accordance with the principles of the present invention
comprises a catheter body having a proximal end, a distal region,
an inflow lumen, and an outflow lumen. An elastomer tube (either
consisting of an elastomeric material or reinforced or constrained
by elastomeric components) is coaxially positioned over the distal
region, and the tube is sealed to the catheter body along a
multiplicity of lines to define at least one, and usually a
plurality of separate inflatable chambers, each of which is fluidly
connected at an inlet end to the inflow lumen and at an outlet end
to the outflow lumen. The surface areas of the chambers, materials
of the balloon and catheter body, catheter dimensions, and the
like, may all be the same as described with the first and second
embodiments of the present invention as set forth above.
[0024] In a fourth aspect, the present invention comprises a method
for fabricating a catheter. A tubular catheter body is first
positioned over a mandrel where the catheter body has at least an
inflow lumen and an outflow lumen. An elastomer tube (as defined
above) is placed over the distal region of the catheter body, and
the elastomer tube is then attached to the catheter body in order
to define a plurality of separate, elastically expandable chambers
between the outside of the catheter body and the inside of the
elastomer tube. The chambers are arranged so that an inlet end of
each chamber is fluidly connected to the inflow lumen and an outlet
end of each chamber is fluidly connected to the outflow lumen. The
dimensions, materials, and other characteristics of the catheter
body and elastomer tube may generally be the same as set forth
above for the catheter body and elastic heat exchange region.
[0025] In the preferred embodiments, the elastomer tube is attached
to the catheter body using heat staking in which case it further
preferred that the elastomer tube be "heat sealable" with the
material of the catheter body, typically being the same material
but having a different hardness. By "heat sealable" it is meant
that the materials of the catheter body and the elastomer tube
will, when exposed to heat, at least partially melt and meld
together along lines formed by a suitable heating tool. Such heat
staking or other sealing will preferably be performed over a
multiplicity of lines to define the plurality of chambers
therebetween. Chambers may be formed axially, helically, or in
other patterns as desired. In a preferred aspect of the fabrication
method, the heat stake or other attachment lines will be formed to
have a width in the circumferential direction in the range from
0.01 mm to 2 mm, preferably from 0.1 mm to 0.5, in order to
circumferentially separate adjacent heat exchange chambers.
[0026] In a fifth aspect of the present invention, a method for
exchanging heat with vascular circulation of a patient comprises
percutaneously introducing a catheter to a blood vessel of the
patient. The catheter includes at least one elastic chamber
conformed over a surface thereof while it is introduced. After
introduction, the chamber is elastically inflated with a heat
exchange medium, typically heated or cooled saline, whereby heat is
exchanged between the heat exchange medium and the vascular
circulation. Typically, the catheter may be introduced into a blood
vessel, such as the femoral vein, an advanced so that the heat
exchange region is at a desired location in the vasculature such as
the IVC. The heat exchange chamber is inflated with heat exchange
medium at a pressure in the range from 0.5 psi to 50 psi,
preferably from 1 psi to 30 psi, and a flow rate in the range from
5 ml/min to 1000 m/min, preferably from 100 ml/min to 500 ml/min.
For heating, the temperature of the medium will typically be in the
range from 33.degree. C. to 48.degree. C., usually from 38.degree.
C. to 42.degree. C. For cooling, the temperature of the medium will
typically be from -10.degree. C. to 34.degree. C., usually from
0.degree. C. to 10.degree. C. In a particular aspect of the present
invention, the heat exchange medium may be pulsed within the
elastic heat exchange structure in order to cause the heat exchange
surface to move or pulse, as generally described in commonly
assigned patent application Ser. No. 09/872,818, the full
disclosure which has previously been incorporated herein by
reference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a perspective illustration of a heat exchange
catheter constructed in accordance with the principles of the
present invention.
[0028] FIGS. 2A and 2B illustrate a first embodiment of a heat
exchange structure according to the present invention.
[0029] FIGS. 3A and 3B illustrate a second embodiment of the heat
exchange structure of the present invention.
[0030] FIGS. 4A and 4B illustrate a third embodiment of the heat
exchange structure of the present invention.
[0031] FIGS. 5A and 5B illustrate alternate cross-sectional views
taken along line 5-5 of FIG. 4B.
[0032] FIGS. 6A-6C illustrate a method of fabricating the heat
exchange catheters of the present invention.
[0033] FIG. 7 illustrates the heat exchange catheter of FIG. 1
being used to treat a patient.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0034] Referring to FIG. 1, a heat exchange catheter 10 comprises a
catheter body 12 having a proximal end 14 and a distal region 16.
The catheter body 12 is a multi-lumen tube having the dimensions
and characteristics set forth above. A hub 18 is attached at the
proximal end 14 of the catheter body and includes an inlet port 20
and an outlet port 22. The inlet port is fluidly connected to an
inflow lumen 24 (FIG. 2A) in the catheter body while the outlet
port 22 is connected to an outflow lumen 26. The inlet port 20 and
outlet port 22 will typically comprise luer fittings or rather
conventional attachments suitable for connecting to a source of
recirculating heat exchange medium, such as heated or cooled
saline. Other suitable heat exchange medium may include saline in
other concentration, superoxygenated fluid, carbon dioxide, helium,
water, or any other similar fluid that is non-toxic in case of
rupture in the heat exchange region. Suitable external heat
exchange sources such as pumps and mechanical heat exchangers are
described in the patent and medical literature. See, for example,
WO 01/64146, a PCT publication whose applicant is the assignee of
the present application.
[0035] A heat exchange structure, such as a helical elastic chamber
30 is formed over the distal region 16 and fluidly connected to the
inflow lumen 24 and outflow lumen 26, as best illustrated in FIGS.
2A and 2B. In its deflated state (FIG. 2A) the heat exchange
structure 20 comprises an elastomer tube having a closed distal end
32 which is tightly conformed over the catheter body 12. The
structure 30 will be sealed or staked to the catheter body 12 along
a line or multiplicity of lines which define the geometry of the
structure when inflated, e.g., as a helical structure as shown in
FIGS. 1 and 2B. Other geometries will described below.
[0036] Heat exchange medium will flow in through port 20 and lumen
24 until reaching an open distal port 34 of the lumen. At this
point, the medium inflates the heat exchange structure to create an
expanded helical chamber 36. The heat exchange medium then flows
back in the direction as shown by the arrows in FIG. 2B until
reaching an outlet port 38 which permits the medium to flow into
the outlet lumen 26 and eventually out through outlet port 22. A
plug 40 is provided at the distal end of the outlet lumen 26 in
order to prevent flow of the heat exchange medium in the wrong
direction.
[0037] Although illustrated as a single spiral structure in FIGS.
1, 2A, 2B, it will appreciated that the helical heat exchange
structure may preferably be formed as two or more parallel helical
lumens. The use of a plurality of lumens is generally preferred
since it increases the total heat exchange area between the heat
exchange medium and the blood flowing through the vasculature.
[0038] While the heat exchange structures will preferably be formed
from a tubular member attached over the outer surface of the distal
region of the catheter body (to form the heat exchange volume
between the other surface of the catheter body and an inner surface
of the tubular member), in some instances it could be formed from a
separate tube which is wound or otherwise arranged over the
catheter body 12, e.g., as shown in FIGS. 3A and 3B. An elastomer
tube 42 can be inserted through a port 38 and attached to the inner
surface of lumen 26, as illustrated in FIG. 3A. An opposite end of
the tube 42 can then be inserted into the distal end of lumen 24
and attached, as also shown in FIG. 3A. Introduction of heat
exchange medium through lumen 24 will then expand the tube, as
shown in FIG. 3B. Removal of the heat exchange medium, will, of
course, result in the elastic tubes collapsing into their low
profile configuration, again as shown in FIG. 3A.
[0039] A variety other configurations could also be employed. A
simple balloon structure without helical or other chambers formed
therein is illustrated in FIGS. 4A and 4B. The structure of the
catheter body 12 remains the same, but an elastomer tube 50 is
formed over the entire length of the catheter body, as shown in
FIG. 4A. By heat staking or otherwise sealing the tube over only a
proximal portion of the catheter body, a balloon may be fully
inflated, as shown in FIG. 4B. Such full inflation is shown in the
cross-sectional view of FIG. 5A. Alternatively, the tube 50 could
be axially heat staked or otherwise sealed to the catheter body,
resulting in a multiple axial lobe embodiment as illustrated in the
cross-sectional view of FIG. 5B. As with the helical embodiments,
it will be desirable to heat stake or otherwise attach the
elastomeric sheath along a line having a width W in the ranges set
forth above. In this way, the distances between each of the lobes
54 are circumferentially spaced apart to enhance heat transfer. In
the embodiment of FIG. 5, pairs of inflow and outflow lumens 24 and
26 are provided for each of the pairs of lobes. Other manifold
means could be provided in order to interconnect the lobes in the
desired manner.
[0040] The preferred catheters of the present invention may be
fabricated according to the method illustrated in FIGS. 6A-6C. The
catheter body 12 is placed over a plurality of mandrels 60, with
one mandrel being provided for each internal lumen. At least one of
the mandrels 60 will be spaced in a proximal direction to permit
introduction of plug 40. An elastomer tube is then expanded and
placed over the distal region 16 of the catheter body 12, as
illustrated in FIG. 6A. Distal end 72 of the elastomer tube 70 is
then closed and sealed, as shown in FIG. 6B. A heating unit 74 is
then used to heat stake the elastomer tube 70 to the exterior
surface of the catheter body 12 allowing axial, spiral, or other
desired lines in order to define the number and geometry of heat
transfer chambers that is desired. Then the mandrels are removed
and the catheter is ready for final fabrication and use.
[0041] Use of the catheter 10 for exchanging heat with patient
circulation and a blood vessel BV, as illustrated in FIG. 7. The
catheter is percutaneously introduced to the target blood vessel,
such as the IVC, and proximal hub 18 (FIG. 1) attached to a
suitable source of heat exchange medium, such as the heat exchange
device illustrated in WO 01/64146, incorporated herein by reference
previously. The heat exchange medium is introduced at a pressure
and a flow rate in the ranges generally described above so that the
spiral heat exchange chamber 36 inflates. The inflation increases
the available heat exchange area, but does not cause the catheter
to engage the blood vessel walls and inhibit blood flow. Thus,
blood flowing in the direction of arrows 80 passes by the exterior
of the spiral heat exchange structure 36, with heat transfer taking
place between the structure and the blood. The availability of an
elastic heat exchange structure permits some control over the rate
of heat transfer based on the pressure the flow rate of the heat
exchange medium being introduced, and if the inflation is
pulsitile, the rate of pulsation. For example, the amount of
inflation may be adjusted to optimize the heat exchange surface. If
a large surface with a high flow rate of the heat exchange fluid is
desired to maximize heat exchange, the pressure of the heat
exchange fluid may be increased. If the patient is small and a
smaller heat exchange surface is desired because, for example, the
vessel in which the heat exchange region is located is small, then
lower pressure may be used to circulate heat exchange fluid. If a
very small rate of heat exchange is desired, for example, if the
patient is being maintained at a target temperature, then a very
low inflation/circulation pressure may be used. It is also true
that heat exchange may be increased by pulsation of the heat
exchange region. The rate of pulsation may be controlled to control
the rate of heat exchange.
[0042] The pressure and the rate of pulsation may be controlled by
feedback from either the patient or from the heat exchange fluid.
For example, pressure feedback from the heart exchange fluid may be
used to control the pressure for the expansion of the heat exchange
region. Alternatively, the expansion of the balloon may be
controlled based on feedback of the flow rate of the heat exchange
fluid, patient temperature, rate of change of patient temperature.
Similarly the pulse rate if any applied to the balloon may be
controlled based on pressure feedback, flow rate of heat exchange
fluid, patient temperature, rate of change of patient temperature,
and the like.
[0043] Another advantage to the ability of this catheter to expand
under pressure might be to seal off a vessel where the balloon is
located or a side branch over which the balloon is located. For
example, it might be advantageous to expand the heat exchange
balloon sufficiently to block flow through the vessel or into a
side branch vessel in coordination with an intraaortic balloon
pump. Similarly it might be advantageous to temporarily seal off a
section of a patient's vasculature to help localize the application
of certain drugs within the vasculature while at the same time
providing a heating or cooling balloon structure.
[0044] The embodiments set forth herein are merely exemplary of the
systems and methods of the present invention. Such exemplary
methods are not meant to be limiting, and it will be appreciated
that a number of modifications and variations of the specific
methods and structures described herein may be practiced within the
scope of the invention as set forth in the claims below.
* * * * *