U.S. patent application number 14/997520 was filed with the patent office on 2016-07-14 for multiple lumen heat exchange catheters.
The applicant listed for this patent is ZOLL Circulation, Inc.. Invention is credited to Wade A. Keller, Timothy R. Machold.
Application Number | 20160199224 14/997520 |
Document ID | / |
Family ID | 28795180 |
Filed Date | 2016-07-14 |
United States Patent
Application |
20160199224 |
Kind Code |
A1 |
Keller; Wade A. ; et
al. |
July 14, 2016 |
MULTIPLE LUMEN HEAT EXCHANGE CATHETERS
Abstract
Catheter devices and methods for intravascular heating and/or
cooling of human or veterinary patients. The catheter devices
generally comprise catheters having inflow and outflow lumens and
at least one curvilinear balloon connected to the inflow and
outflow lumens such that heat exchange fluid may be circulated
through the balloon(s). The catheter is inserted into the
vasculature and heated or cooled fluid is circulated through the
balloon(s) to heat or cool blood flowing in heat-exchange proximity
to the balloon(s), thereby effecting heating or cooling of all or a
portion of the patient's body.
Inventors: |
Keller; Wade A.; (San Jose,
CA) ; Machold; Timothy R.; (Moss Beach, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZOLL Circulation, Inc. |
Sunnyvale |
CA |
US |
|
|
Family ID: |
28795180 |
Appl. No.: |
14/997520 |
Filed: |
January 16, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13855521 |
Apr 2, 2013 |
9237964 |
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14997520 |
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12511015 |
Jul 28, 2009 |
8409265 |
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13855521 |
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10442483 |
May 21, 2003 |
7566341 |
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12511015 |
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09777612 |
Feb 6, 2001 |
6610083 |
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10442483 |
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09138830 |
Aug 24, 1998 |
6620188 |
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09777612 |
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09489142 |
Jan 21, 2000 |
6428563 |
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09138830 |
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60181249 |
Feb 9, 2000 |
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Current U.S.
Class: |
607/105 |
Current CPC
Class: |
A61M 2025/1072 20130101;
A61F 2007/0096 20130101; A61F 2007/0086 20130101; A61M 2025/0078
20130101; A61F 2007/0054 20130101; A61M 2230/50 20130101; A61M
2025/1086 20130101; A61M 2206/10 20130101; A61M 25/1002 20130101;
A61M 25/1011 20130101; A61B 2018/00095 20130101; A61B 18/245
20130101; A61B 2017/22051 20130101; A61F 7/123 20130101; A61B
2017/00084 20130101; A61M 2205/366 20130101; A61F 7/12 20130101;
A61F 2007/0056 20130101; A61B 18/082 20130101; A61F 2007/0095
20130101; A61F 7/007 20130101; A61F 2007/126 20130101; A61B 18/00
20130101; A61F 7/10 20130101; A61M 25/00 20130101 |
International
Class: |
A61F 7/12 20060101
A61F007/12 |
Claims
1. A method for controlling the temperature of at least a portion
of the body of a human or animal subject, said method comprising
the steps of: A) obtaining a heat exchange catheter syste that
comprises a heat exchange catheter and a controller, wherein: the
heat exchange catheter comprises an elongate, flexible catheter
having an inflow lumen and an outflow lumen and at least one heat
exchanger having first and second ends, the inflow lumen of the
catheter being connected to the first end of the heat exchanger and
the outflow lumen being connected to second end of the heat
exchanger such that heat exchange fluid may be circulated into the
first end of the heat exchanger, through the heat exchanger and out
of the second end of the heat exchanger; and the controller
receives i) a target temperature input and ii) a sensed subject
body temperature input and causes heated or cooled fluid to
circulate into the first end of the heat exchanger, through the
heat exchanger and out of the second end of the heat exchanger, to
warm or cool the sensed subject body temperature as needed to cause
the sensed subject body temperature to be approximately the same as
the target temperature; B) inserting the heat exchange catheter
into the vasculature of the patent and positioning the heat
exchanger within a blood vessel through which blood is flowing such
that the heated or cooled fluid will circulate through the heat
exchanger in a direction opposite the direction in which blood
flows through the blood vessel; C) causing a temperature sensor to
sense the temperature of at least a portion of the subject's body
and to communicate a sensed subject body temperature input to the
controller; D) inputting a target temperature to the controller;
and E) allowing the controller to circulate heated or cooled fluid
through the heat exchanger in a direction opposite the direction in
which blood flows through the blood vessel to thereby warm or cool
the sensed subject body temperature as needed to cause the sensed
subject body temperature to be approximately the same as the target
temperature;
2. A method according to claim 1 wherein the controller is adapted
to receive sensed subject body temperature inputs from first and
second temperature sensors and wherein Step C comprises causing
first and second temperature sensors to sense the temperature of at
least a portion of the subject's body and to communicate first and
second sensed subject body temperature inputs to the
controller.
3. A method according to claim 1 wherein the temperature sensor is
selected from the group consisting of: tympanic temperature probes,
esophageal probes, rectal probes, temperature probes for measuring
the temperature of the patient's blood, myocardial temperature
probes, probes that measure core body temperature and skin
temperature probes.
4. A method according to claim 1 wherein the heat exchanger has a
diameter of 9 French or less, at least during insertion in Step
B.
5. A method according to claim 1 wherein the heat exchange catheter
further comprises imageable markers useable to ascertain the
location of the heat exchanger within the subject's body and
wherein the method further comprises the step of: imaging the
imageable markers to ascertain the location of the heat exchanger
within the subject's body.
6. A method according to claim 1 wherein the target temperature is
below normothermia and the method is carried out to cause the
sensed subject body temperature to be hypothermic.
7. A method according to claim 1 wherein the subject is initially
hyperthermic and the method is carried out to cause the sensed
subject body temperature to be approximately normothermic.
8. A method according to claim 1 wherein the subject is initially
hypothermic and the method is carried out to cause the sensed
subject body temperature to be approximately normothermic.
9. A method according to claim 1 wherein the heat exchanger has an
outer surface wherein blood flow channels are formed.
10. A method according to claim 9 wherein helical blood flow
channels are formed in the outer surface of the heat exchanger.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/855,521 filed and issuing on Jan. 19, 2016
as U.S. Pat. No. 9,237,964, which is a continuation of U.S. patent
application Ser. No. 12/511,015 filed Jul. 28, 2009 and issued Apr.
2, 2013 as U.S. Pat. No. 8,409,265, which is a continuation of U.S.
patent application Ser. No. 10/442,483 filed May 21, 2003 and
issued on Jul. 28, 2009 as U.S. Pat. No. 7,566,341, which is a
continuation of U.S. patent application Ser. No. 09/777,612 filed
Feb. 6, 2001 and issued on Aug. 26, 2003 as U.S. Pat. No.
6,610,083, which claims priority to previously filed Provisional
Application Ser. No. 60/181,249 filed Sep. 2, 2000 and which is
also a continuation-in-part of a) U.S. patent application Ser. No.
09/138,830 filed Aug. 24, 1998 and issued on Sep. 16, 2003 as U.S.
Pat. No. 6,620,188 and b) U.S. patent application Ser. No.
09/489,142 filed Jan. 21, 2000 and issued on Aug. 6, 2002 as U.S.
Pat. No. 6,428,563, the entire disclosure of each such related
patent and application being hereby expressly incorporated herein
by reference.
[0002] This invention relates generally to medical devices and a
method of using them for selectively affecting the temperature of a
patient's body, or portion of the patient's body, by adding or
removing heat from the patient's body fluid through the use of a
heat exchange catheter with a heat exchange region in contact with
the body fluid, the heat exchange region being shaped for maximum
heat exchange with minimum insertion profile and minimum
obstruction to the flow of the body fluid. More particularly, this
invention relates to a heat exchange catheter with a heat exchange
region which is an advantageously shaped balloon, wherein the
balloon is placed in flowing body fluid and heat exchange fluid
circulates within the balloon to add or remove heat from the body
fluid in order to treat or induce whole body or regional
hypothermia or hyperthermia. This invention also relates to a
method of controlling the amount of heat removed or added by the
heat exchange region to affect the temperature of all or part of
the patient's body in response to a signal representing the
temperature of all or part of a patient's body.
BACKGROUND OF THE INVENTION
[0003] Under ordinary circumstances, thermoregulatory mechanisms
exist in the healthy human body to maintain the body at a constant
temperature of about 37.degree. C. (98.6.degree. F.), a condition
sometimes referred to as normothermia. Normothermia is generally a
desirable condition, and to maintain normothermia, the
thermoregulatory mechanisms act so that heat lost to the
environment is replaced by the same amount of heat generated by
metabolic activity in the body.
[0004] For various reasons, a person may develop a body temperature
that is below normothermia, a condition known as hypothermia, or a
temperature that is above normothermia, a condition known as
hyperthermia. These conditions are generally harmful and are
usually treated to reverse the condition and return the patient to
normothermia. In certain other situations, however, they may be
desirable and may even be intentionally induced.
[0005] Accidental hypothermia may result when heat loss to the
environment exceeds the body's ability to produce heat internally
or when a person's thermoregulatory ability has been lessened due
to injury, illness or anesthesia. For example, a person exposed to
a cold environment such as a hiker wandering in a very cold climate
for too long, or a sailor overboard in cold water, may become
dangerously hypothermic. Likewise, anesthesia generally disables a
patient's thermoregulatory ability, and it is often the case that,
during long surgery with significant exposure of the patient's
internal body cavities, a patient becomes significantly
hypothermic. Such hypothermia is generally harmful, and must be
quickly reversed to restore the victim to health.
[0006] Simple methods for treating hypothermia have been known
since very early times. Such methods include wrapping the patient
in blankets, administering warm fluids by mouth, and immersing the
patient in a warm water bath. If the hypothermia is not too severe,
and the need to reverse the hypothermia is not to urgent, these
methods may be effective. However, wrapping a patient in a blanket
depends on the ability of the patient's own body to generate heat
to re-warm the body. Administering warm fluids by mouth relies on
the patient's ability to swallow, and is limited both in the
temperature of the liquid consumed and the amount of fluid that may
be administered in a limited period of time. Immersing a patient in
warm water is often impractical, particularly if the patient is
simultaneously undergoing surgery or some other medical
procedure
[0007] More recently, hypothermia may be treated by the application
of a warming blanket that applies heat to the skin of the patient.
Applying heat to the patient's skin, however, may be ineffective in
providing heat to the core of the patient's body. Heat applied to
the skin has to transmit through the skin by conduction or
radiation which may be slow and inefficient, especially if the
patient has a significant layer of fat between the warming blanket
and the body's core.
[0008] Paradoxically, if the patient is suffering significant core
hypothermia, the application of warmth to the patient's skin,
whether by immersion in hot water or application of a warm blanket,
may actually exacerbate the core hypothermia and may even induce
shock. The body's thermoregulatory responses to cold that work to
conserve heat in the body's core include vasoconstriction and
arterio-venous shunting (AV shunts). Vasoconstriction occurs when
the capillaries and other blood vessels in the skin and extremities
constrict so that most of the blood pumped by the heart circulates
within the core rather than through the skin and extremities.
Similarly, in AV shunting, naturally occurring blood shunts exist
between some arteries providing blood to capillary beds in the skin
and extremities and veins returning blood from those capillary beds
and extremities. When the body is cooled, the vessels in the
capillary beds constrict, and the shunts may be opened, causing
blood to by-pass those capillary beds altogether. Thus when the
body is cold, the tissues in the extremities, and particularly at
the surface, have little blood flowing to them and may become quite
cold relative to the body's core temperature.
[0009] When heat is applied to the skin of such a patient, the
temperature sensors in the skin may cause the vasoconstriction to
reverse and the AV shunts to close. When this happens, blood from
the core floods into the very cold tissue on the body surface and
extremities, and as a result the blood loses heat to those tissues,
often far more than the amount of heat being added by the surface
warming. As a result, the victim's core temperature may plummet and
the patient may even go into shock.
[0010] Partly in response to the inadequacies of surface
application of heat, methods have been developed for adding heat to
a patient's body by internal means. A patient being administered
breathing gases, for example a patient under anesthesia, may have
the breathing gases warmed. For some situations, particularly mild
hypothermia requiring the addition of small amounts of heat, this
method may be effective, but it is limited in the amount of heat
that can be administered without injuring the lungs. Similarly, a
patient receiving IV fluids may have the fluids warmed, or a bolus
of warm fluid may be administered intravenously. Again, this may be
effective in the case of mild hypothermia, but the amount of heat
that may be added to a patient's body is limited because the
temperature of the IV fluid is limited to a temperature that will
not be destructive to the blood, generally thought to be about
41.degree. C.-49.degree. C., and the amount of fluid that is
acceptable to administer to the patient.
[0011] A more invasive method may be used to add heat to a
patient's blood, particularly in the case of heart surgery. A
cannula is attached to a vein, usually the inferior vena cava (IVC)
of a patient, the vein clamped off and virtually all the patient's
blood shunted through the cannula to an external pump. The blood is
then pumped back into the patient's body, generally to the arterial
side of the patient's circulation. Blood removed from a patient may
be heated or cooled externally before it is reintroduced into the
patient's body. An example of such a by-pass arrangement is the
Cardio-Pulmonary By-pass system (CPB) often used in open heart
surgery.
[0012] This by-pass method, once it is initiated, is both fast and
effective in adding or removing heat from a patient's blood and in
exercising control over the patient's body temperature in general,
but has the disadvantage of involving a very invasive medical
procedure which requires the use of complex equipment, a team of
highly skilled operators, is generally only available in a surgical
setting, and because of these complexities, requires a long time to
initiate. In fact, it generally cannot begin until after the
patient's thorax has been surgically opened. For all these reasons,
it is generally not useful for emergency treatment of hypothermia.
By-pass also involves mechanical pumping of blood, which is
generally very destructive to the blood resulting in cytotoxic and
thrombolytic problems associated with removal of blood from the
body, channeling the blood through various tubes, artificially
oxygenating the blood, and returning the blood subjected to these
stresses to the circulatory system, including the brain. Because of
the potential harmful impact on the patient, most surgeons attempt
to limit the time a patient is subjected to by-pass to less than
four hours.
[0013] Methods for adding heat to the core of the body that do not
involve pumping the blood with an external, mechanical pump have
been suggested. For example, a method of treating or inducing
hypothermia or hyperthermia by means of a heat exchange catheter
placed in the bloodstream of a patient was described in U.S. Pat.
No. 5,486,208 to Ginsburg, the complete disclosure of which is
incorporated herein by reference. That patent discloses and claims
a method of increasing a patient's body temperature by adding heat
to the blood by inserting a heat exchange catheter having a balloon
with heat exchange fins into the vascular system and circulating
heat exchange fluid through the balloon while the balloon is in
contact with the blood.
[0014] Although accidental hypothermia is generally harmful and
requires treatment, in some instances it may be desirable to induce
hypothermia or permit it to persist in a controlled situation.
Hypothermia is generally recognized as being neuroprotective and
may be induced for that reason. Neural tissue such as the brain or
spinal cord, is particularly subject to damage by vascular disease
processes including, but not limited to ischemic or hemorrhagic
stroke, blood deprivation for any reason including cardiac arrest,
intracerebral or intracranial hemorrhage, and head trauma. Other
where hypothermia may be protective include treatment of myocardial
infarction, and heart surgery, neurosurgical procedures such as
aneurysm repair, 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. In each of these instances,
damage to brain tissue may occur because of brain ischemia,
increased intracranial pressure, edema or other processes, often
resulting in a loss of cerebral function and permanent neurological
deficits. Hypothermia may be intentionally induced because it is
advantageous in such situations. In fact, in some of these
situations, such as beating heart by-pass surgery, hypothermia
currently occurs as a normal side effect of anesthesia disabling a
patient's normal thermoregulatory responses in conjunction with
prolonged exposure of the chest cavity. The resultant hypothermia
may not itself be harmful if adequate control over the patient's
temperature is established, and where the hypothermic condition is
controlled as to depth and duration, it may be permitted to persist
or even induced. Control of the depth of hypothermia and reversal
of hypothermia after the operation are both important, and if that
control is not possible, hypothermia is generally thought to be
undesireable.
[0015] Although the exact mechanism for neuroprotection is not
fully understood, lowering the brain temperature is believed to
effect neuroprotection through several mechanisms including, the
blunting of any elevation in the concentration of neurotransmitters
(e.g., glutamate) occurring after ischemic insult, reduction of
cerebral metabolic rate, moderation of intracellular calcium
transport/metabolism, prevention of ischemia-induced inhibitions of
intracellular protein synthesis and/or reduction of free radical
formation as well as other enzymatic cascades and even genetic
responses.
[0016] Besides its benefit as a prophylactic measure, for example
during surgery to prevent damage in case of neurologic ischemia, it
is also sometimes desirable to induce whole-body or regional
hypothermia for as a treatment in response to certain neurological
diseases or disorders such as head trauma, spinal trauma and
hemorrhagic or ischemic stroke. Hypothermia has also been found to
be advantageous as a treatment to protect both neural tissue and
cardiac muscle tissue after a myocardial infract (MI). Again, the
exact mechanism of benefit is not known, but inducing hypothermia
in such situations, after the initial ischemic insult, may lessen
damage by decreasing reperfusion injury, interrupting various
chemical cascades that would otherwise damage the cells involved,
protecting membrane integrity and perhaps even preventing certain
genetic changes leading to apoptosis.
[0017] Intentionally inducing hypothermia has generally been
attempted by either surface cooling or by-pass pumping. Surface
cooling has generally proved to be unacceptably slow, since the
body heat to be removed must be transmitted from the core to the
surface, and has sometimes been altogether unsuccessful since the
body's thermoregulatory mechanisms act to oppose any attempt to
induce hypothermia and generally succeed in preventing surface
cooling from reducing the core temperature of the body. For
example, the vasoconstriction and AV shunting may prevent heat
generated in the core from being transmitted to the surface by the
blood. Thus the surface cooling may only succeed in removing heat
from the skin and surface tissue and thus cooling the surface, and
not succeed in reducing the core temperature of the patient.
[0018] Another thermoregulatory mechanism that may thwart attempts
to reduce core temperature by surface cooling is shivering. There
are numerous temperature sensors on the body's surface, and these
may trigger the body to begin shivering. Shivering results in the
generation of a significant amount of metabolic heat, as much as
five times more than the resting body, and especially where
vasoconstriction and AV shunting reduce blood to the surface of the
body, suface cooling such as by a cooling blanket can only reduce
the temperature of the patient very slowly, if at all. Even if the
thermoregulatory mechanisms are disabled by anesthesia or other
drugs, it has generally been found that the cooling by surface
measures such as blankets is unacceptably slow for inducing
hypothermia. If the patient has fever and thus an elevated set
point temperature (the temperature which the body's
thermoregulatory responses act to maintain), the patient may even
shiver at a temperature above normothermia. In such situations, it
has been found that surface cooling is often unable to reduce the
patient's temperature even to normothermia. Furthermore, besides
often being ineffective and generally being unacceptably slow,
surface cooling lacks sufficient control over the target
temperature of the patient, since the methods are inadequate to
quickly adjust the patient's body temperature and therefore may
result in overshoot or other uncontrolled body temperature problems
that cannot be adequately managed.
[0019] Inducing hypothermia using by-pass techniques is generally
effective, fast and controllable, but is also subject to the
shortcomings of the by-pass method for adding heat to control
accidental hypothermia; it requires a very invasive procedure in an
operating room under full anesthesia, with intubation, expensive
equipment and highly trained personnel. Even in the situation of
open heart surgery or neurosurgery where the patient is in the
operating suite and has highly skilled personnel in attendance
anyway, the by-pass mechanism requires pumping the blood with a
mechanical pump through external circuit, which is generally
thought to be very destructive of the blood and is generally not
maintained for very long, preferably four hours or less, and
cooling cannot be begun before the patient's thorax is opened and a
shunt surgically installed, itself a procedure that might induce
some neurological ischemia, or continued, nor warming effected,
after the patient's thorax is closed. Thus any advantage of
pre-cooling before the patient is opened, or continued after or
re-warmed after the patient is closed, is not attained by this
method, and the patient is exposed to the undesirable effects of
external pumping.
[0020] Cold breathing gases and cold infusions have generally not
been used to induce hypothermia. Breathing cold gases is generally
ineffective to induce hypothermia since the lungs are generally
structured to be able to breathe very cold air without rapidly
inducing hypothermia. Injection of cold infusate would generally be
unacceptable as a method of inducing and maintaining hypothermia
because infusing the large volume of liquid that would be necessary
to induce and maintain hypothermia for a useful length of time
would be unacceptable.
[0021] The previously mentioned heat exchanged cathetger placed in
the bloodstream of a patient overcomes many of these inadequacies
of the other methods of combating accidental hypothermia, or
intentionally inducing hypothermia. Particularly in view of the
body's own thermoregulatory attempts to maintain normothermia, a
very efficient heat exchange catheter is highly desirable.
[0022] Under certain conditions heat is generated within the body
or heat is added from the environment in excess of the body's
ability to dissipate heat, and a persons develops a condition of
abnormally high body temperature, a condition known as
hyperthermia. Examples of this condition may result from exposure
to a hot and humid environment or surroundings, overexertion, or
exposure to the sun while the body's thermoregulatory mechanisms
are disabled by drugs or disease. Additionally, often as a result
of injury or disease, a person may establish a set point
temperature that is above the normal body temperature of about
37.degree. C. a condition generally known as fever. In another
condition, malignant hyperthermia, a condition not well understood,
the body may fail to dissipate enough heat and the temperature of
the body may spiral to dangerous levels without the body's normal
mechanisms being effective to return the patient to
normothermia.
[0023] Prolonged and severe hyperthermia may have serious and very
negative effects. For example, a child with prolonged and high
fever as a result of spinal meningitis might suffer permanent brain
damage. In stroke, the presence of even a mild fever has been found
to correlate with very negative outcome. In such cases, it may be
very desirable to counteract the body's attempt to establish a
higher temperature, and instead to maintain at temperature at or
near normothermia. However, the unaided body is acting to maintain
a temperature above 37.degree. C. and the body's own
thermoregulatory mechanisms, such as AV shunting and shivering may
render surface cooling altogether ineffective in reestablishing
normothermia. The advantages of an effective core cooling method
are sorely needed in such situations.
[0024] As with hypothermia, counter-parts to simple methods for
treating undesirable hyperthermia exist, such as cold water baths
and cooling blankets, as well as more effective but complex and
invasive means such as cooled breathing gases and blood cooled
during by-pass. These, however, are subject to the limitations and
complications as described above in connection with hypothermia. In
addition, as is the case when attempting to induce hypothermia, the
thermoregulatory responses of the body such as vasoconstriction, AV
shunting and shivering, may act directly to combat the attempt to
cool the patient and thereby defeat the effort to treat the
hyperthermia. In order to achieve the reduction of accidental,
diseased or malignant hyperthermia, a catheter with sufficient heat
exchange effectiveness to override the body's thermoregulatory
defenses is needed.
[0025] For various reasons, it may be desirable to induce and/or
maintain hyperthermia. For example, certain cancer cells may be
sensitive to temperature elevations, and thus it may be possible to
destroy those cancerous cells by elevating a patient's temperature
to a level that is toxic to the cancer cells but the rest of the
body can tolerate. As another example, a high temperature may be
toxic to certain viruses at a level that the rest of the body can
tolerate. Raising the patient's temperature above that which the
virus can tolerate but within a temperature range the body can
tolerate would help to rid the body of the virus. A heat exchanger
that can add heat to the bloodstream of a patient at a sufficient
rate to maintain the patient in a state of hyperthermia would
therefore be desirable.
[0026] Besides intentionally induced hypothermia or hyperthermia,
it is sometimes desirable to control a patient's temperature to
maintain a target temperature, sometimes but not always
normothermia. For example, in a patient under general anesthesia
during major surgery, the anesthesiologist may wish to control the
patient's body temperature by directly adding or removing heat. In
such a situation, the patient's normal thermoregulatory responses
are reduced or eliminated by anesthesia, and the patient may lose
an extraordinary amount of heat to the environment. The patient's
unaided body may not generate sufficient heat to compensate for the
heat lost and the patient's temperature may drift lower. The
anesthesiologist may wish to control the temperature at
normothermia, or may prefer to allow the patient to become somewhat
hypothermic, but control the depth and duration of the hypothermia.
A device and method for precisely controlling body temperature by
efficiently adding or removing heat to control a patient's
temperature would be very desirable.
[0027] In addition to controlling the patient's body temperature,
fast and precise control of the adjustments to a patient's thermal
condition is very important when a patient's temperature is being
manipulated. When using heat transfer from the surface to the core
of a patient as by the application of warming or cooling blankets,
besides being slow and inefficient, the control of the patient's
core temperature is very difficult, if not impossible. The
temperature of the patient tends to Aovershoot@ the desired low
temperature, a potentially catastrophic problem when reducing the
core temperature of a patient, especially to moderate or sever
levels. The body's own metabolic activity and thermoregulatory
responses may make even gross adjustments of core temperature by
surface cooling difficult, slow, or even impossible. Speedy and
precise control is generally not possible by such methods at
all.
[0028] Control of body temperature using by-pass techniques is
generally fairly precise and relatively fast, especially if large
volumes of blood are being pumped through the system very quickly.
However, as was previously stated, this method is complex,
expensive, invasive and it is this very pumping of large quantities
of blood that may be seriously damaging to the patient,
particularly if maintained for any significant period of time, for
example for or more hours.
[0029] An efficient heat exchanger might make possible the
manipulation of temperature of a select portion of a patient's
body. Generally, the temperature throughout the body is relatively
constant and generally does not vary significantly from one
location to another. (One exception is the skin, which because of
exposure to the environment may vary significantly in temperature.
In fact, many of the thermoregulatory mechanisms discussed above
depend on the ability of the skin to maintain a different
temperature, generally a lower temperature, than the temperature of
the core of the body.) The mammalian body generally functions most
efficiently at normothermia. In some instances, however, regional
hypothermia or hyperthermia (hypothermia or hyperthermia of only a
part of the body while the rest of the body is at a different
temperature, preferably normothermia) may be advantageous. For
example, it could be advantageous to cool the head for purposes of
neuroprotection of the brain or cool the heart to protect the
myocardium from suffering infarction during or after ischemia, or
heating a cancerous region to destroy cancerous cells, while
maintaining the rest of the body at normal, healthy temperature so
that the disadvantages of whole body hypothermia or hyperthermia
would not occur. Additionally, where the entire body is cooled,
shivering and other thermoregulatory mechanisms may act to counter
attempts to cool the body, and if only a specific region were
targeted for cooling, those mechanisms might be obviated or
eliminated.
[0030] A heat exchanger in contact with body fluid, such as blood,
which was directed to the target area, might alter the temperature
of that region if the heat exchanger was efficient enough to cool
the blood sufficiently to cool the tissue in question even if the
body temperature, i.e. the initial temperature of the blood flowing
past the heat exchange region was normothermic. A heat exchange
catheter with a highly efficient heat exchange region would be
required for such an application. Where the catheter is inserted
percutaneously into the vasculature, it is also highly desirable to
have as small an insertion profile as possible to allow as small a
puncture as possible, yet allow maximum surface area of the heat
exchange region in contact with the flowing blood. Such a catheter
is the subject of this application.
[0031] For all the foregoing reasons, there is a need for a means
to add or remove heat from the body of a patient in an effective
and efficient manner, while avoiding the inadequacies of surface
heat exchange and avoiding the dangers of internal methods
including by-pass methods. There is the need for a means of
rapidly, efficiently and controllably exchanging heat with the
blood of a patient so the temperature of the patient or target
tissue within the patient can be altered or controllably maintained
at some target temperature.
[0032] Positioning a catheter centrally within the flowing
bloodstream may be important for various reasons. Contact between a
hot or cold heat exchange region and the walls of a body conduit
such as a blood vessel may affect the tissue at the point of
contact. In some applications, such as where the user seeks to tack
the surface of a dissected vessel to the wall of the vessel, or to
thermally treat or ablate the tissue in question, the contact
between the balloon and the surrounding body structure is
important, even critical. Where, however, the contact is
undesirable, it would be advantageous to have a means to prevent
the heat exchange region from resting against the vessel wall.
[0033] Where temperature control of the temperature of the blood is
the goal, it is also advantageous to position the heat exchange
region in the center of a flow of body fluid, for example in the
center of the lumen of a blood vessel so that the blood flow would
surround the entire balloon and no portion of the balloon surface
would be sheltered from the flow and thus prevented from exchanging
heat at the balloon surface with the body fluid. This would also
help prevent blood to pool in areas of low flow or lack of flow,
which has been shown to cause blood to clot.
[0034] It would be particularly advantageous if the heat exchange
surface could be configured to maximize the surface area in contact
with the blood while minimizing the obstruction to fluid flow
within the vessel. This is desirable both because maximum flow is
important for maximum heat exchange and because maximum flow will
assure that there is adequate blood supply to tissue downstream of
the heat exchange region. Thus the rate of the blood flow past the
heat exchange region should be maximized at the same time that the
surface area of the heat exchange region within the stream of
flowing blood is maximized. A catheter that could achieve these
seemingly contradictory goals would be highly desirable.
[0035] Additionally, where heat exchange is occurring between two
flowing fluids, it is most efficient to have counter-current flow.
That is, the flow of the heat exchange liquid is counter to the
flow direction of the fluid with which it is exchanging heat. Since
a heat exchange catheter might be inserted into blood vessels in
various ways that would result in the natural blood flowing being
different in different instances (i.e. proximal to distal, or
distal to proximal) it would advantageous to have a catheter
wherein the direction of the fluid flow in the portion of the
balloon exposed to the flow of the body fluid could be adjusted to
flow in either direction to permit the catheter could be inserted
into the blood vessel in either direction, and the direction of the
flow of the heat exchange fluid adjusted to flow counter to the
flow in the vessel.
[0036] If the heat exchange catheter is to be inserted into the
vasculature of a patient, it is very advantageous to have a small
insertion profile, that is to say a diameter of the device at
insertion that is a small as possible. This permits the insertion
of the device through as small sheath, puncture, or incision. Yet
the surface area of the heat exchange region should be maximized
when the catheter is functioning to exchange heat with the blood.
Once again, these goals seem contradictory, and a heat exchange
catheter that could achieve both characteristics would be highly
advantageous.
SUMMARY OF THE INVENTION
[0037] The present invention provides a heat exchange catheter
having a heat exchange region that comprises a balloon having
multiple lumens for circulation of a heat exchange medium and a
method for accomplishing intravascular heat exchange by circulation
of heat exchange medium from outside the body through a multi-lumen
shaft and through a multi-lumen balloon having curvilinear (e.g.,
helical, twisted or other curved configuration) balloon elements
such as balloon lobes in contact with a patient's blood.
[0038] Further in accordance with the invention, there is provided
a heat exchange catheter having a heat exchange region that
comprises at least one balloon having multiple lumens for
circulation of a heat exchange medium and a method for
accomplishing intravascular heat exchange by circulation of heat
exchange medium from outside the body through a multi-lumen shaft
and through a shaped multi-lumen balloon in contact with a
patient's blood. The method further may include altering the
temperature of the heat exchange fluid outside the body so that it
is a temperature different than the temperature of the patient's
blood, placing the heat exchange region in contact with the
patient's blood, and circulating the heat exchange fluid through
the heat exchange region to exchange heat with the bloodstream at a
sufficient rate and for a sufficient length of time to effect
regional or whole body temperature modification of the patient.
[0039] Further in accordance with the invention, a heat exchange
catheter of the invention may comprise a flexible catheter body or
shaft having a proximal end and a distal end, the distal end of
such catheter shaft being adapted to be inserted percutaneously
into the vasculature or body cavity of a mammalian patient. A heat
exchange region is provided on the catheter shaft, comprising a
balloon with a plurality of lumens helically wound around a central
axis. (A balloon is defined as a structure that is readily
expandable under pressure and collapsible under vacuum and includes
both elastomeric structures and non-elastomeric structures that are
deformable in the manner described.) The shaft of the catheter
preferably includes a fluid circulation path or lumen, and each
heat exchange element preferably is attached at both ends of the
shaft and incorporates a fluid circulation path or lumen that is in
fluid communication with the fluid circulation path or lumen of the
catheter shaft. In this manner, heat exchange fluid may be
circulated into or through the heat exchange region as it is
circumferentially surrounded by the body fluid.
[0040] Further in accordance with some embodiments of the
invention, the heat exchange region may be less than the length of
the portion of the catheter inserted into the patient and may be
located at or near the distal end thereof. In such embodiments, an
insulating region may be formed on the catheter shaft proximal to
the heat exchange region to reduce unwanted transfer of heat to and
from the proximal portion of the catheter shaft.
[0041] Further in accordance with the present invention, there is
provided a system for heat exchange with a body fluid, the system
including a) a liquid heat exchange medium and b) a heat exchange
catheter having a heat exchange region comprising a balloon having
helicaly formed lumens. The catheter includes a shaft having a
proximal end and a distal end, the distal end adapted to be
inserted percutaneously into a body cavity. The shaft having a
circulation pathway therein for the circulation of heat exchange
medium therethrough. The heat exchange region is attached to the
catheter so that when the catheter is inserted in the body cavity,
body fluid surrounds the heat exchange region.
[0042] Further in accordance with the present invention, the heat
exchange region is deflated for percutaneous insertion into the
patient's vasculature to a small diameter, and once positioned with
the heat exchanger in the vasculature, the heat exhange region may
be inflated to a larger diameter to increase the surface area of
the heat exchange region for maximum heat exchange with the
blood.
[0043] The system further may include a sensor or sensors attached
to the patient to provide feedback on the condition of the patient,
for example the patient's temperature. The sensors are desirably in
communication with a controller that controls the heat exchange
catheter based on the feedback from the sensors.
[0044] Still further in accordance with the present invention,
there is provided a method for exchanging heat with a body fluid of
a mammal. The method includes the steps of a) providing a catheter
that has a circulatory fluid flow path therein and a heat exchange
region thereon, such heat exchange region including heat exchange
elements that are attached to the catheter shaft at the heat
exchange region, b) inserting the catheter into a body cavity and
into contact with a body fluid, the heat exchange elements thus
being surrounded by the body fluid and c) causing a heat exchange
medium to flow through the circulatory flow path of the catheter so
that the medium exchanges heat with a body fluid through the heat
exchange elements. Each of the heat exchange elements may be hollow
balloon lobes, and step C of the method may include causing heat
exchange fluid to flow through the hollow heat exchange
elements.
[0045] It is an object of this invention to provide an effective
and advantageous heat exchange region for adding heat to a patient
suffering from hypothermia.
[0046] It is a further object of this invention to provide an
effective means for removing heat from the bloodstream of a patient
suffering from hyperthermia.
[0047] It is a further object of this invention to provide an
effective means of adding or removing heat from a patient to induce
normothermia.
[0048] It is a further object of this invention to provide an
effective means for maintaining normothermia.
[0049] It is a further object of this invention to provide an
effective means of cooling a patient to a target temperature and
controllably maintaining that temperature.
[0050] It is a further object of this invention to provide a heat
exchange catheter that has an advantageous configuration that
provides for maximum heat exchange with blood flowing in heat
exchange proximity to the heat exchange region.
[0051] It is a further object of this invention to provide a heat
exchange catheter that has an advantageous shape that attains an
advantageous ratio of heat exchange surface area while maintaining
adequate flow in a blood vessel.
[0052] It is a further object of this invention to provide a
catheter with a sufficiently effective and efficient heat exchange
region to cool a target region of a patient.
[0053] It is a further object of this invention to provide a
catheter with a sufficiently effective and efficient heat exchange
region to precisely maintain a patient at a target temperature.
[0054] It is a further object of this invention to provide a heat
exchange catheter that is configured to efficiently exchange heat
with the blood of a patient while allowing continued flow of the
blood past the catheter with a minimum of restriction to that blood
flow.
[0055] It is a further object of this invention to provide a heat
exchange catheter having a heat exchange region comprised of
multiple balloon elements such as lobes.
[0056] It is a further object of this invention to provide a heat
exchange catheter having an insulated shaft.
[0057] It is a further object of this invention to provide an
effective method of controlling the temperature of a body
fluid.
[0058] It is a further object of this invention to provide an
effective method of warming a body fluid.
[0059] It is a further object of this invention to provide an
effective method of cooling a body fluid.
[0060] It is a further object of this invention to provide an
effective method for inducing hypothermia.
[0061] It is a further object of this invention to provide a
catheter having a heat exchange region wherein the temperature is
controlled by the temperature of flowing heat exchange fluid and
wherein the direction of the fluid flow may be reversed.
[0062] It is a further object of this invention to provide a heat
exchange catheter having a heat exchange region wherein, when the
heat exchange region is placed within a blood vessel, the shape of
the heat exchange region assists in centering the heat exchange
region within the vessel.
[0063] It is a further object of this invention to provide a heat
exchange catheter having a heat exchange region composed of
multiple, non-coaxial balloon elements such as lobes of a
multi-lobed balloon.
[0064] These and other objects of this invention will be understood
with reference to the following drawings and description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0065] FIG. 1 is a perspective drawing of an embodiment of the
catheter of the invention.
[0066] FIG. 1A is a perspective drawing of an alternative tie-down
at the proximal end of the catheter shown in FIG. 1.
[0067] FIG. 2 is a cross-sectional drawing of the shaft of the
catheter taken along the line 2-2 in FIG. 1.
[0068] FIG. 3 is a cross-sectional drawing of the heat exchange
region of the catheter taken along the line 3-3 in FIG. 1.
[0069] FIG. 3A is a cross-sectional drawing of the heat exchange
region of the catheter taken along the line 3A-3A in FIG. 1.
[0070] FIG. 4 is a perspective drawing of a segment of the heat
exchange region of the catheter within the circle 4-4 in FIG.
1.
[0071] FIG. 5 is a cross-sectional drawing of the heat exchange
region of the catheter taken along the line 5-5 in FIG. 1.
[0072] FIG. 6 is a perspective drawing of a segment of the heat
exchange region of the catheter within the circle 6-6 in FIG.
1.
[0073] FIG. 7 is a perspective drawing of the multi-lobed balloon
of one embodiment of the invention.
[0074] FIG. 8 is a perspective drawing of the distal portion of the
shaft of one embodiment of the invention.
[0075] FIG. 9 is a perspective drawing, partially in ghost, of the
heat exchange region formed by the shaft and multi-lobed balloon of
FIGS. 7 and 8.
[0076] FIG. 10 is an expanded view of the attachment of the central
lumen of the balloon to the shaft of the catheter of FIG. 9 showing
the region within the circle 10-10 in FIG. 9.
[0077] FIG. 10A is an expanded view of the plug between the shaft
and the central lumen of the balloon of the catheter of FIG. 9
showing the region within the circle 10A-10A in FIG. 9.
[0078] FIG. 11 is a perspective view of a portion of a multi-lobed
curvilinear heat exchange balloon of one embodiment of the
invention.
[0079] FIG. 11A is a cross sectional view of the heat exchange
region taken along the line 11A-11A in FIG. 11.
[0080] FIG. 12 is a sectional view of the proximal portion of the
heat exchange region of one embodiment of the invention.
[0081] FIG. 12A is a cross-sectional view of a portion of the heat
exchange region taken along the line 12A-12A of FIG. 12.
[0082] FIG. 12B is a cross-sectional view of a portion of the heat
exchange region taken along the line 12B-12B of FIG. 12.
[0083] FIG. 12C is a cross-sectional view of a portion of the heat
exchange region taken along the line 12C-12C of FIG. 12.
[0084] FIG. 13 is a sectional view of the distal portion of the
heat exchange region of one embodiment of the invention.
[0085] FIG. 13A is a cross-sectional view of a portion of the heat
exchange region taken along the line 13A-13A of FIG. 13.
[0086] FIG. 13B is a cross-sectional view of a portion of the heat
exchange region taken along the line 13B-13B of FIG. 13.
[0087] FIG. 14 is a sectional view of the distal portion of the
heat exchange region of one embodiment of the invention.
[0088] FIG. 15A is a side view, partially in ghost, of the heat
exchange region of one embodiment of the invention.
[0089] FIG. 15B is a cross-section taken along the line 15B-15B in
FIG. 15A.
[0090] FIG. 15C is a cross-section taken along the line 15C-15C in
FIG. 15A.
[0091] FIG. 15D is a cross-section taken along the line 15D-15D in
FIG. 15A.
[0092] FIG. 15E is a cross-section taken along the line 15E-15E in
FIG. 15A.
[0093] FIG. 15F is a cross-section taken along the line 15F-15F in
FIG. 15A.
[0094] FIG. 16A is a perspective view of one embodiment of an
intavascular heat exchange catheter according to the present
invention.
[0095] FIG. 16B is a front perspective view of one embodiment of an
extracorporeal temperature control console that is useable in
conjunction with the catheter of FIG. 16A to accomplish temperature
management of a human or veterinary patient.
[0096] FIG. 17 is a flowchart of an exemplary method of the
invention.
DETAILED DESCRIPTION
[0097] The present invention provides an improved heat exchange
catheter that provides an efficient and effective heat exchange
region to exchange heat with body fluid while maintaining a minimum
insertion profile of the catheter. The heat exchange catheter
generally comprises a catheter having a shaft for the flow of heat
exchange fluid to and from a heat exchange region, and the heat
exchange region comprising an advantageously configured multiple
lumen balloon wherein the heat exchange fluid flows through the
balloon and blood flows over the outside of the balloon and heat is
exchanged through the walls of the balloon between the heat
exchange fluid flowing inside the balloon and the blood flowing
outside the balloon.
[0098] Referring to FIGS. 1 through 10A, in one advantageous
embodiment, the catheter is comprised of a shaft 50 with a heat
exchange region 100 thereon.
[0099] The shaft has two roughly parallel lumens running through
the proximal shaft, an inflow lumen 52 and an outflow lumen 54. The
shaft generally also comprises a working lumen 56 running
therethrough for the insertion of a guide wire, or the application
of drugs, radiographic dye, or the like to the distal end of the
catheter. The heat exchange region comprises a four-lumen balloon,
with three outer lumens 58, 60, 62 disposed around an inner lumen
64 in a helical pattern. In the particular embodiment shown, the
balloon preferable makes one full rotation about the inner lumen 64
for each 2 to 4 inches of length. All four lumens are thin walled
balloons and each outer lumen shares a common thin wall segment 66,
68, 70 with the inner lumen. The balloon is approximately
twenty-five centimeters long, and when inflated has an outer
circumference 72 of approximately 0.328 in. When deflated, the
profile is generally less than about 9 French (3 French is 1 mm in
diameter). When the balloon portion is installed on the shaft, both
the balloon proximal end 74 and the distal end 76 are sealed around
the shaft in a fluid tight seal as will be described below.
[0100] The catheter is attached at its proximal end to a hub 78. At
the hub, the guide wire lumen 56 communicates with a guide wire
port 80, the inflow lumen 52 is in fluid communication with an
inflow port 82, and the outflow lumen 54 is in communication with
an outflow port 84. Attached at the hub and surrounding the
proximal shaft is a length of strain relief tubing 86 which may be,
for example, a length of heat shrink tubing. The strain relief
tubing may be provided with suture tie downs 88, 90. Alternatively,
a butterfly tie-down 92 may be provided. (See FIG. 1A). Between the
strain relief tubing 86 and the proximal end of the balloon 74, the
shaft 50 is extruded with an outer diameter of about 0.118 inches.
The internal configuration is as shown in cross-section in FIG. 2.
Immediately proximal of the balloon attachment 74, the shaft is
necked down 94.
[0101] The outer diameter of the shaft is reduced to about 0.100 to
0.110 inches, but the internal configuration with the three lumens
is maintained. Compare, for example, the shaft cross-section of
FIG. 2 with the cross-section of the shaft shown in FIG. 3. This
length of reduced diameter shaft remains at approximately constant
diameter of about 0.100 to 0.110 inches between the necked down
location at 94 and the distal location 96 where the outflow lumen
is sealed and the guide wire extension tube 98 is attached as will
be described.
[0102] At the necked down location 94, a proximal balloon marker
band 102 is attached around the shaft. The marker band is a
radiopaque material such as a platinum or gold band or radiopaque
paint, and is useful for locating the proximal end of the balloon
by means of fluoroscopy while the catheter is within the body of
the patient.
[0103] At the marker band, all four lobes of the balloon are
reduced down and fastened to the shaft 50. This may be accomplished
by folding the outer lobes of the balloon 58, 60, 62 down around
the inner lumen 64, placing a sleeve, for example a short length of
tubing, over the balloon and inserting adhesive, for example by
wicking the adhesive, around the entire inner circumference of the
sleeve. The inner lumen is then fastened to the shaft using a
second short length of tubing. A short length for example 1 mm, of
intermediate tubing 104 is heat welded to the inside of the inner
lumen. The intermediate tube has an outer diameter approximately
the same as the inner diameter of the inner lumen. The intermediate
tube is then slid over the shaft at about the location of the
neck-down near the proximal marker 102 and adhesive 106 is wicked
into the space between the inside of the intermediate tubing and
the outer surface of the shaft 50.
[0104] A similar process may be used to attach the distal end o the
balloon. The distal end of the balloon is attached down around the
guide wire extension tube 98 rather than the shaft, but otherwise
the attachment is essentially similar.
[0105] Distal of the proximal balloon seal, under the balloon, an
elongated window 108 cut through the wall of the outflow lumen in
the shaft. Along the proximal portion of the balloon, five slits,
e.g. 110, are cut into the common wall between each of the outer
lumens 58, 60, 62 and the inner lumen 64. Because the outer lumens
are twined about the inner lumen in a helical fashion, each of the
outer tubes passes over the outflow lumen of the inner shaft member
at a slightly different location along the length of the inner
shaft, and therefore an elongated window 108 is cut into the
outflow lumen of the shaft so that each outer lumen has at least
one slit e.g. 110 that is located over the window in the shaft.
Additionally, there is sufficient clearance between the outer
surface of the shaft and the wall of the inner lumen to create
sufficient space to allow relatively unrestricted flow through heat
exchange fluid through all 5 slits in each outer lumen, around the
shaft, and through the elongate window 108 into the outflow lumen
54 in the shaft 50.
[0106] Distal of the elongated window in the outflow lumen, the
inner member 64 of the four-lumen balloon is sealed around the
shaft in a fluid tight plug. Referring to FIG. 10a, the plug is
formed by, for example shrinking a relatively thick length of PET
tubing to form a length of plug tubing 112 where the inner diameter
of the length of plug tubing is approximately the same as the outer
diameter of the shaft at the location where the plug is to be
formed. The plug tubing is slid over the shaft and fits snugly
against the shaft. The shaft is generally formed of a material that
is not heat shrinkable. As may be seen in FIG. 10A and FIG. 3, some
clearance exists between the outer wall of the shaft and the inner
wall of the inner lumen 64. The walls of the inner lumen are
composed of thin heat shrinkable material, for example PET. A probe
with a resistance heater on the distal end of the probe is inserted
into the guide wire lumen of the shaft and located with the heater
under the plug tubing. The probe is heated, causing the heat shrink
wall of the inner lumen to shrink down against the plug tubing, and
the plug tubing to shrink slightly down against the shaft. The
resultant mechanical fit is sufficiently fluid tight to prevent the
outflow lumen and the space between the shaft and the wall of the
inner lumen from being in fluid communication directly with the
inner member or the inflow lumen except through the outer lumens as
will be detailed below.
[0107] Just distal of the plug, the outflow lumen is closed by
means of heat sealing 99, and the inflow lumen is skived open to
the inner member 101. This may be accomplished by necking down the
shaft at 96, attaching a guide wire extension tube 98 to the guide
wire lumen, and at the same location opening the inflow lumen to
the interior of the inner lumen and heat sealing the outflow lumen
shut. The guide wire extension tube continues to the distal end of
the catheter 114 and thereby creates communication between the
guide wire port 80 and the vessel distal of the catheter for using
a guide wire to place the catheter or for infusing drugs,
radiographic dye, or the like beyond the distal end of the
catheter.
[0108] The distal end of the balloon 76 is sealed around the guide
wire extension tube in essentially the same manner as the proximal
end 74 is sealed down around the shaft. Just proximal of the distal
seal, five slits 116 are cut into the common wall between each of
the three outer lumens 58, 60 62 of the balloon and the inner lumen
64 so that each of the outer lumens is in fluid communication with
the inner lumen.
[0109] Just distal of the balloon, near the distal seal, a distal
marker band 118 is placed around the guide wire extension tube. A
flexible length of tube 120 may be joined onto the distal end of
the guide wire tube to provide a soft tip to the catheter as a
whole.
[0110] In use, the catheter is inserted into the body of a patient
so that the balloon is within a blood vessel, for example in the
inferior vena cava (IVC). Heat exchange fluid is circulated into
the inflow port 82, travels down the inflow lumen 52 and into the
inner lumen 64 distal of the plug tube 112. The heat exchange fluid
travels down the inner lumen, thence through slits 116 between the
inner lumen 64 and the three outer lumens 58, 60, 62.
[0111] The heat exchange fluid then travels back through the three
outer lumens of the balloon to the proximal end of the balloon. A
window 108 is cut in the outflow lumen of the shaft proximal of the
plug 99. in the distal portion of the balloon, approximately above
the window, about five slits 110 are cut in the wall between each
of the outer balloon lumens 58, 60, 62 and the inner lumen 64.
[0112] Since the outer lumens are wound in helical pattern around
the inner lumen, at some point at least one of the slits from each
of the outer lumens is located directly over the window 108 in the
outflow lumen. Additionally, there is sufficient clearance between
the wall of the inner lumen and the shaft, as illustrated at 102 in
FIG. 10A, that even if the slits are not directly over the window
108, flow into the space between the wall of the inner lumen and
the outer wall of the shaft 50 allows the fluid to flow ultimately
into the window 108 and out the outflow lumen without undue
resistance. It then flows out the outflow lumen and out of the
catheter through the outflow port 84. The fluid may be pumped at a
pressure of, for example, 40-50 pounds per square inch (psi), and
at a pressure of about 41 psi, a flow of as much as 500 milliliters
per minute may be achieved.
[0113] Counter-current circulation between the blood and the heat
exchange fluid is highly desirable for efficient heat exchange
between the blood and the heat exchange fluid. Thus if the balloon
is positioned in a vessel where the blood flow is in the direction
from proximal toward the distal end of the catheter, for example if
it were placed from the femoral vein into the ascending vena cava,
it is desirable to have the heat exchange fluid in the outer
balloon lumens flowing in the direction from the distal end toward
the proximal end of the catheter. This is achieved by the
arrangement described above. It is to be readily appreciated.
however, that if the balloon were placed so that the blood was
flowing along the catheter in the direction from distal to
proximal, for example if the catheter was placed into the IVC from
a jugular insertion, it would be desirable to have the heat
exchange fluid circulate in the outer balloon lumens from the
proximal end to the distal end. Although in the construction shown
this is not optimal and would result is somewhat less effective
circulation; this could be accomplished by reversing which port is
used for inflow direction and which for outflow.
[0114] Where heat exchange fluid is circulated through the balloon
that is colder than the blood in the vessel into which the balloon
is located, heat will be exchanged between the blood and the heat
exchange fluid through the outer walls of the outer lumens, so that
heat is absorbed from the blood. If the temperature difference
between the blood and the heat exchange fluid (sometimes called
.DELTA.T), for example if the blood of the patient is about
37.degree. C. and the temperature of the heat exchange fluid is
about 0.degree. C., and if the walls of the outer lumens conduct
sufficient heat, for example if they are thin (0.002 inches or
less) of a plastic material such as polyethylene terephthalate
(PET), enough heat may be exchanged (for example about 200 watts)
to lower the entire body temperature of the patient at a useful
rate, for example 3-6.degree. C. per hour.
[0115] The helical structure of the outer lumens has the advantage
over straight lumens of providing greater length of heat exchange
fluid path for each length of the heat exchange region. It may also
provide for enhanced flow patterns for heat exchange between
flowing liquids. Additionally, the helical shape may assist in
maintaining flow in a roughly tubular conduit, for example blood
flow in a blood vessel, by not creating a firm seal around the heat
exchange region since the exterior of the heat exchange region is
not tubular.
[0116] The fact that the heat exchange region is in the form of an
inflatable balloon also allows for a minimal insertion profile, for
example 9 French or less, while the heat exchange region may be
inflated once inside the vessel for dramatically increased
functional diameter of the heat exchange region in operation. After
use, the balloon can be collapsed for easy withdrawal.
[0117] Such a configuration is adequately efficient in heat
exchange, the use of a system which controls the temperature of the
heat exchange fluid which system is directed in response to signals
representing the temperature of a patient is adequate to exercise
control over the body temperature of a patient.
[0118] Referring now to FIGS. 11 through 13B, in another example of
a preferred embodiment, the heat exchange region is in the form
that may be called a twisted ribbon. The heat transfer fluid
circulates to and from the heat exchange region 202 via channels
formed in the shaft 206 in much the same manner as previously
described for shaft 50. FIGS. 11 and 11A illustrate this embodiment
of a heat exchange region 202 comprising a plurality of balloon
elements in the form of tubular members that are stacked in a
helical plane.
[0119] More specifically, a central tube 220 defines a central
lumen 222 therewithin. A pair of smaller intermediate tubes 224a,
224b attaches to the exterior of the central tube 220 at
diametrically opposed locations. As illustrated here, the tubes are
attached or alternatively extruded in a unitary extrusion so that
the balloon elements form essentially the lobes of a multi-lobed
balloon.
[0120] Each of the smaller tubes 224a, 224b defines a fluid lumen
226a, 226b therewithin. A pair of outer tubes 228a, 228b attaches
to the exterior of the intermediate tubes 224a, 224b in alignment
with the aligned axes of the central tube 220 and intermediate
tubes 224a, 224b. Each of the outer tubes 228a, 228b defines a
fluid lumen 230a, 230b within. By twisting the intermediate and
outer tubes 224a, 224b, 228a, 228b around the central tube 220, the
helical ribbon-like configuration of FIG. 11 is formed.
[0121] An inflow path of heat exchange medium is provided by the
central tube 220, as described in greater detail below. The
intermediate tubes 224a, 224b and outer tubes 228a, 228b define a
fluid outflow path within the heat exchange region 202. Heat
exchange fluid is transferred into the catheter through an inflow
port of a hub at the proximal end of the shaft and after
circulation is removed via an outflow port in essentially the same
manner as previously described. Likewise, a guide wire port is
provided on the hub.
[0122] Now with reference to FIGS. 12 and 12A-12C, a proximal
manifold of the heat exchange region 202 will be described. The
shaft 206 extends a short distance, desirably about 3 cm, within
the central tube 220 and is thermally or adhesively sealed to the
interior wall of the central tube as seen at 250. As seen in FIG.
12A, the shaft 206 includes a planar bulkhead 252 that generally
evenly divides the interior space of the shaft 206 into an inflow
lumen 254 and an outflow lumen 256. A working or guide wire lumen
260 is defined within a guide wire tube 262 that is located on one
side of the shaft 206 in line with the bulkhead 252. Desirably, the
shaft 206 is formed by extrusion.
[0123] The outflow lumen 256 is sealed by a plug 264 or other
similar expedient at the terminal end of the shaft 206 within the
central tube 220. The inflow lumen 254 remains open to the central
lumen 222 of heat exchange region 202.
[0124] The guide wire tube 262 continues a short distance and is
heat bonded at 270 to a guide wire extension tube 272 generally
centered within the central tube 220.
[0125] A fluid circulation path is illustrated by arrows in FIG. 12
and generally comprises fluid passing distally through the inflow
lumen 254 and then through the entirety of the central lumen 222.
Fluid returns through the lumens 226a, 226b, and 230a, 230b of the
intermediate and outer tubes 224a, 224b, and 228a, 228b,
respectively, and enters reservoirs 274 and 275. These reservoirs
are in fluid communication with each other, forming essentially one
terminal reservoir in fluid communication with one window 276 in
the outflow lumen. Alternatively, two windows may be formed 276 and
a counterpart not shown in FIG. 12 one helical twist farther down
the shaft, between each side of the twisted ribbon (i.e., lumens
224a and 224b on one side, and 228a and 228b on the other side). In
this way, one reservoir from each side of the twisted ribbon is
formed in fluid communication with the outflow lumen 256, each
through its own window (configuration not shown). Fluid then enters
the outflow lumen 256 through apertures, e.g., 276, provided in the
central tube 220 and a longitudinal port 278 formed in the wall of
the shaft.
[0126] A distal manifold of the heat exchange region 202 is shown
and described with respect to FIGS. 13 and 13A-13B. The outer tubes
228a, 228b taper down to meet and seal against the central tube 220
which, in turn, tapers down and seals against the guide wire
extension tube 272. Fluid flowing distally through the central
lumen 222 passes radially outward through a plurality of apertures
280 provided in the central tube 220. The apertures 280 open to a
distal reservoir 282 in fluid communication with lumens 226a, 226b,
and a distal reservoir 281 in fluid communication with lumens 230a,
230b of the intermediate and outer tubes 224a, 224b, and 228a,
228b.
[0127] With this construction, heat exchange fluid introduced into
the input port 240 will circulates through the inflow lumen 254,
into the central lumen 222, out through the apertures 280, and into
the distal reservoir 282. From there, the heat exchange fluid will
travel proximally through both intermediate lumens 226a, 226b and
outer lumens 230a, 230b to the proximal reservoirs 274 and 275.
Fluid then passes radially inwardly through the apertures 276 and
port 278 into the outflow lumen 256. Then the fluid circulates back
down the shaft 206 and out the outlet port.
[0128] The twisted ribbon configuration of FIGS. 11-13C is
advantageous for several reasons. First, the relatively flat ribbon
does not take up a significant cross-sectional area of a vessel
into which it is inserted. The twisted configuration further
prevents blockage of flow through the vessel when the heat exchange
region 202 is in place. The helical configuration of the tubes
224a, 224b, 228a, 228b also aids to center the heat exchange region
202 within a vessel by preventing the heat exchange region from
lying flat against the wall of the vessel along any significant
length of the vessel. This maximizes heat exchange between the
lumens and the blood flowing next to the tubes. It also helps
prevent thermal injury to the vessel wall by avoiding prolonged
contact between a specific location on the vessel wall and the heat
exchange region of the catheter. Because of these features, the
twisted ribbon configuration is ideal for maximum heat exchange and
blood flow in a relatively small vessel such as the carotid artery.
As seen in FIG. 11A, an exemplary cross-section has a maximum
functional diameter 300 of about 5 mm, permitting treatment of
relatively small vessels.
[0129] The deflated profile of the heat exchange region is small
enough to make an advantageous insertion profile, as small as 7
French for some applications. Even with this low insertion profile,
the heat exchange region is efficient enough to adequately exchange
heat with blood flowing past the heat exchange region to alter the
temperature of the blood and affect the temperature of tissue
downstream of the heat exchange region. Because of its smaller
profile, it is possible to affect the temperature of blood in
smaller vessels and thereby provide treatment to more localized
body areas.
[0130] This configuration has a further advantage when the heat
exchange region is placed in a tubular conduit such as a blood
vessel, especially where the diameter of the vessel is
approximately that of the major axis (width) of the cross section
of the heat exchange region. The configuration tends to cause the
heat exchange region to center itself in the middle of the vessel.
This creates two roughly semicircular flow channels within the
vessel, with the blood flow channels divided by the relatively flat
ribbon configuration of the heat exchange region. It has been found
that the means for providing maximum surface for heat exchange
while creating minimum restriction to flow is this configuration, a
relatively flat heat exchange surface that retains two
approximately equal semi-circular cross-sections. This can be seen
in reference to FIG. 11A if the essential functional diameter of
the dashed circle 300 is essentially the same as a vessel into
which the twisted ribbon is placed. Two roughly semi-circular flow
paths 302, 304 are defined by the relatively flat ribbon
configuration of the heat exchange region, i.e. the width or major
axis (from the outer edge of 228a to the outer edge of 228b) is at
least two times longer than the height, or minor axis (in this
example, the diameter of the inner tube 222) of the overall
configuration of the heat exchange region. It has been found that
if the heat exchange region occupies no more than about 50% of the
overall cross-sectional area of the circular conduit, a highly
advantageous arrangement of heat exchange to flow is created. The
semi-circular configuration of the cross-section of the flow
channels is advantageous in that, relative to a round
cross-sectioned heat exchange region (as would result from, for
example, a sausage shaped heat exchange region) the flow channels
created minimize the surface to fluid interface in a way that
minimizes the creation of laminar flow and maximizes mixing.
[0131] Maximum blood flow is important for two reasons. The first
is that maximum flow downstream to the tissue is important,
especially if there is obstruction in the blood flow to the tissue,
as would be the case in ischemic stroke or an MI. The second reason
is that heat exchange is highly dependent on the rate of blood flow
past the heat exchange region, with the maximum heat exchange
occurring with maximum blood flow, so maximum blood flow is
important to maximizing heat transfer.
[0132] A third exemplary embodiment is very similar to the twisted
ribbon embodiment just described, except that the outermost tubes
230a', 230b' are shorter than the intermediate tubes 226a', 226b',
and terminate short of the intermediate tubes, and therefore the
heat exchange region has a staggered diameter. Such a construction
is illustrated in FIG. 14. The configuration of the shaft and the
proximal portion of the balloon are essentially the same as the
twisted ribbon catheter just described. However, on the distal end
of the heat exchange region, the central lumen 220' is manifolded
to the intermediate lumens 226a' and 226b' by slits, for example
280'. The outer lumens 230a' and 230b', however, do not extend all
the way to the distal location where the intermediate tubes are
manifolded to the central lumen. Instead, at a location proximal of
the distal end of the intermediate tube, the wall between the outer
lumens and the intermediate lumens are cut 295' so that the outer
and intermediate lumens are manifolded to be in fluid communication
with each other. In this way, heat exchange fluid may be introduced
into the inflow port, flow down the inflow lumen to the central
lumen, exit the central lumen through slits into the intermediate
lumen. The heat exchange fluid then travels proximately down the
intermediate lumen for some distance to the point where the outer
lumens are in fluid communication with the intermediate lumens
through slits 295'. The heat exchange fluid travels proximally down
both the intermediate lumen and the outer lumen to the proximal
manifold, which is essentially the same as described in the
previous embodiment and illustrated in FIG. 12. According to this
construction, a very small diameter heat exchange region can be
placed very distal in a small vessel, and yet a larger diameter
heat exchange region be located proximally in a larger vessel or a
larger diameter portion of the vessel into which the distal portion
of the staggered diameter heat exchange region is located. The
lengths of the various lumens illustrated in FIG. 14 is not meant
to be literal, and it will readily be appreciated that the lengths
and diameters of the lumens may be adjusted to achieve the
configuration that may be desired for various applications. In some
applications as will be readily appreciated by those of skill in
the art, more than merely two lumens may be similarly stacked to
achieve a configuration with one, two, three or even more steps in
diameter of the heat exchange region.
[0133] In any configuration, for maximum heat exchange results, it
is important that the difference in temperature between the blood
and heat exchange region be as large as possible. Because of the
long length of catheter required for selective cooling of the brain
within the carotid artery in conjunction with femoral insertion,
maximum thermal insulation of the shaft is important to maximize
heat transfer with the blood flowing to the brain and minimize heat
transfer with the blood flowing away from the brain. In use, the
catheter is generally passed through a vessel of relatively large
diameter, for example the Vena Cava or the abdominal aorta, so that
there is room within the vessel around the proximal shaft to
utilize an inflatable insulating region around the shaft. Such an
inflatable region is more fully described in parent application
Ser. No. 09/489,142 filed Jan. 21, 2000, Titled Heat Exchange
Catheter with Improved Insulated Region of which this application
is a Continuation in Part and which has previously been
incorporated in full by reference. Because the insulating region
204 is deflated at insertion, and inflated thereafter, the incision
or puncture into the vasculature is minimized but once inflated,
the insulation is maximized. The insulation region is, of course,
deflated for removal.
[0134] An alternative construction to the heat exchange balloon is
illustrated in FIGS. 15A through 15F wherein the heat exchange
region is formed of a four lobed balloon, the balloon having three
collapsible outer balloon lobes 902, 904, 906 located in roughly
linear and parallel configuration around a central collapsible
lumen 908. The catheter has a proximal shaft 910 formed having two
lumens running the length of the shaft, the first lumen forming an
inlet channel 912 and the second lumen forming an outlet channel
914. The interior of the shaft is divided into the two lumens by
webs 916, 917, but the lumens do not occupy equal portions of the
interior of the shaft. The inlet channel occupies about 1/3 of the
circumference of the interior; the outlet channel occupies about
2/3 of the circumference of the interior for reasons that will be
explained below. A guide wire lumen 929 is formed running down the
center of the shaft.
[0135] Within the proximal portion of the heat exchange region of
the catheter, the shaft is affixed to the balloon. A transition
region 915 is formed between the shaft 910 and the tube 911 forming
the central collapsible lumen 908. The outlet channel is plugged
917, the tube 911 is affixed over the shaft 910 by, for example
gluing, at the transition 915, and the shaft ends. A guide wire
extension tube 930 is attached to the guide wire lumen 929 with the
guide wire tube running to the distal end of the catheter.
Alternatively, the outer wall of the shaft may be removed at the
transition region, leaving only the tube which forms the guide wire
lumen intact.
[0136] After the outlet lumen is plugged 917 and the shaft attached
to the interior of the tube which forms the central lumen of the
balloon, with the inlet channel open into the interior of the
central lumen, as shown at FIG. 15C, the inlet channel is then
occupies the entire inner lumen of the balloon 908 except for the
guide wire extension tube 930.
[0137] At the distal end of the balloon, inlet orifices 918, 920,
922 are formed between the inlet channel and the three collapsible
balloon outer lobes 902, 904, 906. At the proximal end of the heat
exchange region, outlet orifices 924, 926, 928 are formed between
the interior of each outer balloon lobe and the outlet channel 914
in the shaft. These may be formed by, for example, cutting or
burning holes in the common wall between the central lumen and the
outer balloon lobes and simultaneously through the wall of the
shaft over the outlet lumen. As may be seen in FIG. 15D, the
configuration of the outlet channel is such that the wall of the
outlet channel occupies a sufficient circumference of the shaft, as
noted above, that communication between the outlet channel and the
interior of each of the three outer balloon lobes may be
created.
[0138] As may be appreciated, in use, heat exchange fluid may be
introduced into the inlet channel through an inlet port (not
shown), flow down the inlet channel in the shaft 912 and into the
central lumen of the balloon 908. It then flows to the distal end
of the heat exchange region, through the inlet orifices 918, 920,
922 in the common wall between the central lumen and the three
outer balloon lobes and flows into the interior lumens of the
balloon lobes 919, 921, 923, travel back down each of the three
balloon lobes and re-enter the shaft through the outlet orifices
924, 926, 928. The heat exchange fluid then flows down the outlet
channel 914 to the proximal end of the catheter. In this way heat
exchange fluid may be circulated through the three outer balloon
lobes to add heat to the blood flowing in heat transfer proximity
to the balloons if the heat exchange fluid is warmer than the
blood, or to remove heat from the blood if the heat exchange fluid
is cooler than the blood.
[0139] The balloon is formed from a material that will permit
significant thermal exchange between the heat exchange fluid on the
interior of the balloon and the body fluid flowing over the outside
of the balloon in heat exchange proximity to the surface of the
balloon. One such appropriate material is very thin plastic
material such as PET, which may also be made strong enough to
withstand the pressure necessary for adequate flow of the heat
exchange fluid while at the same time being thin enough, perhaps
less than 2 mils (0.002 inches).
[0140] It may also readily be appreciated that the same heat
exchange balloons of the various types described herein may be used
to add heat to the blood stream or remove heat from the blood
stream depending on the relative temperature of the heat exchange
fluid and the blood flowing in heat exchange proximity to the
balloon. That is, the same device at the same location may be used
alternately to add or to remove heat merely by controlling the
temperature of the heat exchange fluid within the device. When
attached to a control unit that can alter the temperature of the
heat exchange fluid in response to an external signal, for example
a sensed temperature of a patient in which the catheter has been
placed, the device may be used to automatically control the
temperature of the patient.
[0141] As previously described, precise control over a patient's
temperature is highly desirable. Because the heat exchange regions
of the catheters of this invention are highly efficient and are
able to add or remove heat from a patient with great speed and
effectiveness, very precise control over the temperature of a
patient is possible. Precise control, for example with a precision
of one or two tenths of a degree Celsius, is possible using a heat
exchange catheter of this invention and a feedback control
mechanism as illustrated in FIG. 16. In that example, a reservoir
of heat exchange fluid is placed in contact with a heater or
cooler, for example thermoelectric coolers (TEC) located within the
controller box 600 but not illustrated. A source of heat exchange
liquid 602, for example saline, is attached the reservoir to supply
heat exchange fluid to the system. A pump within the controller box
circulates the fluid through the reservoir and out the outflow line
604 which directs the heated or cooled fluid to the inflow port 82
of the catheter. After the fluid circulates through the catheter as
described earlier, it returns to the reservoir through the inflow
line 606, which receives fluid from the outflow port 84 of the
catheter hub. The fluid is then circulated through the reservoir in
contact with the heater or cooler, which heats or cools the fluid,
and is then recirculated in a closed loop back through the
catheter.
[0142] Temperature probes 608, 610 are placed on or in the patient
so that they generate a signal that represents the temperature of
the patient of the portion of the patient that is controlled by the
system. A single probe may be used, but dual probes may also be
used, for example to provide for redundancy as a safety measure.
Those probes may be tympanic temperature probes, esophageal probes,
rectal probes, temperature probes for measuring the temperature of
the patient's blood, myocardial temperature probes, or any other
probes that will generate a signal representative of the
temperature sought to be controlled by the system which may be, for
example, a temperature of a target tissue or core body temperature.
Skin temperature probes are generally not sufficiently accurate or
free from environmental influences to act as control probes for
this system. However there is no fundamental reason why such probes
could not be used, and if they were sufficiently accurate, even
surface temperature probes would suffice.
[0143] A series of desired control parameters are manually input
into a microprocessor control unit such as a dedicated computer in
the control unit, via the user input interface 612. The parameters
may include for example, the desired patient temperature and the
rate of warming or cooling. The temperature probes 610, 608 provide
patient temperature signals to the temperature input terminals 614,
616. The computer then controls the temperature of the heat
exchange fluid based on the desired parameters as input by the user
and the temperature signal as input by the temperature probes.
[0144] The controller might, for example, add heat to the heat
exchange fluid to either warm the patient or reduce the rate of
cooling. Similarly, the controller might reduce the temperature of
the heat exchange fluid to cool the patient or to reduce the rate
of warming, depending on the current temperature of the heat
exchange fluid and the desired parameters.
[0145] A method is also disclosed for warming, cooling or
controlling a patient using the system disclosed here. That method
entails placing a catheter of the invention with the heat exchange
region in the bloodstream of a patient. Temperature probes are
placed to sense the temperature of the patient or the target tissue
in question. A controller is provided that can control the heat
exchange between the catheter and the blood by, for example,
controlling the temperature of heat exchange region. In the
catheters of this invention that comprises controlling the
temperature of or rate of flow of the heat exchange fluid provided
to the heat exchange region. The controller's microprocessor is
capable of receiving the signal representing the temperature of the
patient and responding by controlling the heat exchange catheter to
increase, decrease or maintain the temperature of the patient
within precise parameters as input by the user.
[0146] A heat exchange device may also be supplied as a kit
comprising the heat exchange device and a set of instruction for
using the heat exchange device. The heat exchange device may
comprise, for example, a heat exchange catheter as described in
this application. The instructions for use will generally instruct
the user to insert the heat exchange device into a body fluid
containing region and to establish the temperature of the heat
exchange device to affect the temperature of the body fluid. The
instructions for use may direct the user to heat or cool the body
fluid to achieve any of the purposes described in this
application.
[0147] While all aspects of the present invention have been
described with reference to the aforementioned applications, this
description of various embodiments and methods shall not be
construed in a limiting sense. The aforementioned is presented for
purposes of illustration and description. It shall be understood
that all aspects of the invention are not limited to the specific
depictions, configurations or relative proportions set forth herein
which depend upon a variety of conditions and variables. The
specification is not intended to be exhaustive or to limit the
invention to the precise forms disclosed herein. Various
modifications and insubstantial changes in form and detail of the
particular embodiments of the disclosed invention, as well as other
variations of the invention, will be apparent to a person skilled
in the art upon reference to the present disclosure. It is
therefore contemplated that the appended claims shall cover any
such modifications or variations of the described embodiments as
falling within the true spirit and scope of the invention.
* * * * *