U.S. patent application number 17/651609 was filed with the patent office on 2022-08-04 for devices, systems and methods for endovascular temperature control.
The applicant listed for this patent is ZOLL Circulation, Inc.. Invention is credited to Jeremy Thomas Dabrowiak, John William Jacobsen, Ayan Majumdar, Sean W. Yip.
Application Number | 20220241108 17/651609 |
Document ID | / |
Family ID | 1000006276901 |
Filed Date | 2022-08-04 |
United States Patent
Application |
20220241108 |
Kind Code |
A1 |
Jacobsen; John William ; et
al. |
August 4, 2022 |
DEVICES, SYSTEMS AND METHODS FOR ENDOVASCULAR TEMPERATURE
CONTROL
Abstract
Devices, systems and methods for controlling a patient's body
temperature by endovascular heat exchange and/or surface heat
exchange.
Inventors: |
Jacobsen; John William; (San
Jose, CA) ; Majumdar; Ayan; (San Jose, CA) ;
Yip; Sean W.; (Mountain View, CA) ; Dabrowiak; Jeremy
Thomas; (Santa Clara, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZOLL Circulation, Inc. |
San Jose |
CA |
US |
|
|
Family ID: |
1000006276901 |
Appl. No.: |
17/651609 |
Filed: |
February 18, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16052551 |
Aug 1, 2018 |
11337851 |
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17651609 |
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15594541 |
May 12, 2017 |
11116657 |
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16052551 |
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15423581 |
Feb 2, 2017 |
11185440 |
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15594541 |
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PCT/US2018/016754 |
Feb 2, 2018 |
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15423581 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2007/0054 20130101;
A61F 2007/0086 20130101; A61M 2205/6018 20130101; A61F 2007/0093
20130101; A61B 90/90 20160201; A61M 25/00 20130101; A61F 2007/126
20130101; A61M 2205/127 20130101; A61F 7/12 20130101; A61F 7/0085
20130101; A61F 2007/0096 20130101 |
International
Class: |
A61F 7/12 20060101
A61F007/12; A61F 7/00 20060101 A61F007/00; A61B 90/90 20060101
A61B090/90 |
Claims
1-14. (canceled)
15. A body temperature management system comprising: a body heat
exchanger positionable on or in a subject's body, a heat exchange
fluid warmer and/or cooler; a heat exchange fluid pump which
circulates heat exchange fluid through the heat exchange fluid
warmer and/or cooler and through the body heat exchanger; a sensor
for sensing the subject's actual body temperature; a user interface
configured to receive a user-input patient temperature set point;
and a controller which receives signals indicating the user-input
patient temperature and the currently-sensed actual body
temperature; wherein the controller is programmed to control the
heat exchange fluid warmer or cooler and/or the heat exchange fluid
pump to: i) initially cause the system to perform a first phase of
warming or cooling, during which the heat exchange fluid circulates
through the body heat exchanger at temperature and flow rate to
cause the sensed actual body temperature to increase or decrease
until the sensed actual body temperature reaches a predetermined
interim temperature, said interim body temperature being less than
the user-input patient temperature set point if the subject is
being warmed or greater than the patient temperature set point if
the subject is being cooled; and, thereafter, ii) cause the system
to perform a second phase of warming or cooling to increase or
decrease from the interim temperature to the user input temperature
set point at one or more rates which are slower than said initial
rate, until the sensed actual body temperature becomes equal to the
user-input patient temperature set point without substantially
overshooting the user input patient temperature set point; and,
thereafter, iii) cause the system to perform a third phase of
warming or cooling during which the temperature and/or flow rate of
the heat exchange fluid is/are periodically adjusted as needed to
maintain the sensed actual body temperature substantially equal to
the user-input patient temperature set point.
16. A system according to claim 15 wherein the user interface
allows the user to select a rate of warming or cooling and the
controller will cause the system to perform said first, second and
third phases only when the selected rate of warming or cooling is
greater than a triggering rate.
17. A system according to claim 16 wherein the triggering rate is
greater than 0.1 degrees C. per hour.
18. A system according to claim 15 wherein the user interface
allows the user to select a maximum rate of warming or cooling and
the controller will cause the system to perform said first, second
and third phases when the maximum rate is selected.
19. A system according to claim 15 wherein during the first phase
the temperature and/or flow rate of the heat exchange fluid or pump
speed is/are periodically adjusted as needed to cause the sensed
actual body temperature to increase or decrease until the sensed
actual body temperature reaches a predetermined interim
temperature.
20. A system according to claim 15 wherein during the second phase
the temperature and/or flow rate of the heat exchange fluid or pump
speed is/are periodically adjusted as needed to cause the sensed
actual body temperature to increase or decrease to the user input
temperature set point.
21. A system according to claim 15 wherein during the first phase
the temperature and flow rate of the heat exchange fluid are
substantially constant and are not varied based on sensed changes
in the actual patient temperature.
22. A system according to claim 15 wherein, during phase 2, the
actual patient body temperature warms or cools at a rate of 0.05
degrees C. per hour to 0.1 degrees C. per hour.
23. A system according to claim 15 wherein the user interface
allows the user to select a patient temperature set point and the
controller will cause the system to perform said first, second and
third phases only when the patient temperature set point is greater
than a triggering patient temperature set point.
24. A system according to claim 21, wherein the triggering patient
temperature set point is greater than 37.8 degrees C.
Description
RELATED APPLICATIONS
[0001] This is a continuation in part of copending U.S. patent
application Ser. No. 15/594,541 entitled Devices, Systems and
Methods for Endovascular Temperature Control filed May 12, 2017,
which is a continuation in part of U.S. patent application Ser. No.
15/423,581 entitled Devices, Systems and Methods or Endovascular
Temperature Control filed Feb. 2, 2017. Additionally, this
application is a continuation in part of copending PCT
International Patent Application No. PCT/US18/16754 entitled
Devices, Systems and Methods for Endovascular Temperature Control
filed Feb. 2, 1018. The entire disclosure of each such prior
application is hereby expressly incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present disclosure relates generally to the fields of
medicine and engineering and more particularly to devices, systems
and methods for controlling a patient's body temperature by
endovascular heat exchange.
BACKGROUND
[0003] Pursuant to 37 CFR 1.71(e), this patent document contains
material which is subject to copyright protection and the owner of
this patent document reserves all copyright rights whatsoever.
[0004] In various clinical situations, it is desirable to warm,
cool or otherwise control the body temperature of a subject. For
example, hypothermia can be induced in humans and some animals for
the purpose of protecting various organs and tissues (e.g., heart,
brain, kidneys) against the effects of ischemic, anoxic or toxic
insult. For example, animal studies and/or clinical trials suggest
that mild hypothermia can have neuroprotective and/or
cardioprotective effects in animals or humans who suffer from
ischemic cardiac events (e.g., myocardial infract, acute coronary
syndromes, etc.), postanoxic coma after cardiopulmonary
resuscitation, traumatic brain injury, stroke, subarachnoid
hemorrhage, fever and neurological injury. Also, studies have shown
that whole body hypothermia can ameliorate the toxic effects of
radiographic contrast media on the kidneys (e.g., radiocontrast
nephropathy) of patients with pre-existing renal impairment who
undergo angiography procedures.
[0005] One method for inducing hypothermia is by endovascular
temperature management (ETM) wherein a heat exchange catheter is
inserted into a blood vessel and a thermal exchange fluid is
circulated through a heat exchanger positioned on the portion of
the catheter that is inserted in the blood vessel. As the thermal
exchange fluid circulates through the catheter's heat exchanger, it
exchanges heat with blood flowing past the heat exchange in the
blood vessel. Such technique can be used to cool the subject's
flowing blood thereby resulting in a lowering of the subject's core
body temperature to some desired target temperature. ETM is also
capable of warming the body and/or of controlling body temperature
to maintain a monitored body temperature at some selected
temperature. If a controlled rate of re-warming or re-cooling from
the selected target temperature is desired, that too can be
accomplished by carefully controlling the amount of heat added or
removed from the body and thereby controlling the temperature
change of the patient.
SUMMARY
[0006] In accordance with the present disclosure, there are
provided heat exchange devices, systems and methods which
facilitate efficient endovascular and/or body surface heat
exchange.
[0007] In accordance with one embodiment, there is provided a
system for circulating a warmed or cooled thermal exchange fluid
through an endovascular heat exchanger (e.g., an endovascular heat
exchange catheter), wherein a) the system produces a pulsatile flow
of thermal exchange fluid and b) the system is connected to the
endovascular heat exchanger by way of one or more conduits which
comprise a pulse damping conduit that functions not only as a
conduit through which the thermal exchange fluid flows but also a
pulse damper for damping pulses or pressure in the thermal exchange
fluid as it flows therethrough. The pulse damping conduit may
comprise, for example, tubing that has sufficient elastic or
flexural properties to dampen or reduce the amplitude of pulses in
the thermal exchange fluid as it flows therethrough.
[0008] In accordance with another embodiment, there is provided a
system for warming or cooling the body of a human or animal
subject, such system comprising an extracorporeal control system
that is connectable to one or more changeable component(s) (e.g.,
an endovascular heat exchange catheter, a body surface heat
exchange pad, tubing, a cassette through which thermal exchange
fluid circulates, other disposable components, etc.). When the
changeable component(s) is/are connected to the extracorporeal
control system, the system is useable to effect heat exchange with
the subject's body. The changeable component(s) may include machine
readable encoded information. The extracorporeal control system
includes a reader or processor that receives and reads the encoded
information. The extracorporeal control system uses such encoded
information to identify, qualify, confirm or control the operation
of the changeable component(s). The encoded information may be
stored in any suitable electronic storage medium and may be
embedded in a chip or microchip mounted on or in the changeable
component(s). Examples of the types of encoded information that may
be stored include but are not limited to; unique identifier(s) for
the changeable components (e.g., manufacturer identification, part
number, lot number, etc.), indications of whether the changeable
component(s) have previously been used (e.g., an encoded indication
of first use), indications of whether the changeable component(s)
is/are expired (e.g., encoded expiration date), operational
characteristic(s) and or operational variables (e.g., minimum
and/or maximum pressure, minimum and or maximum flow rate, control
algorithm to be used, etc.) of the changeable component(s) (e.g.,
encoded indications of the size, type, volume, etc. of the
changeable component(s). Examples of the types of information
storage that may be utilized include but are not necessarily
limited to: non-volatile random access memory (RAM), non-volatile
flash memory, electrically erasable programmable read-only memory
(EEPROM) or ferroelectric random access memory (FRAM). The
extracorporeal control system may comprises a controller (e.g., a
processor) programmed to take one or more actions in response to
the encoded information. For example, the controller may be
programmed to determine whether the encoded information meets a
prerequisite requirement and to proceed with warming or cooling of
the subject's body only if said prerequisite requirement is
met.
[0009] In accordance with another embodiment, there is provided a
thermal exchange engine for warming or cooling a thermal exchange
fluid. Such thermal exchange engine comprises thermal exchange
plates or evaporators which are alternately coolable by circulation
of refrigerant through the plates and warmable by heaters
positioned on or in the plates. A cassette receiving space is
located between the temperature controlled plates and is configured
for receiving a cassette or heat exchanger. The cassette comprises
a frame and an expandable vessel (e.g., a bag or other expandable
fluid containing vessel). The expandable vessel is finable with
thermal exchange fluid, e.g., after the cassette has been inserted
into the cassette receiving space. Heat is thereby transferred
between the refrigerant and the thermal exchange fluid or the
heater(s) and the thermal exchange fluid. In some embodiments,
outer surface(s) of the expandable vessel may be coated with a
release material, covered with a layer of releasable material or
otherwise treated or modified to deter sticking of the expandable
vessel to the adjacent thermal exchange plates. In some
embodiments, surface(s) of the thermal exchange plates and/or
surfaces of the expandable vessel or a layer on a surface of the
expandable vessel may be textured or provided with holes, groves or
other surface features to deter sticking of the expandable vessel
to the adjacent thermal exchange plates. In some embodiments, the
cassette may comprise a housing attached to an insertable portion
(e.g., the frame and expandable vessel) by a hinged attachment such
that the cassette may be disposed in a folded or closed
configuration prior to use and converted to an unfolded or open
configuration at the time of use. Such hinged connection between
the housing and the insertable portion may be constructed so that,
once unfolded or opened, the cassette locks in the unfolded or open
configuration. In some embodiments, a plurality of hooks located in
the console or system may be initially positioned in retracted
positions allowing insertion of the insertable portion into the
cassette receiving space between the thermal exchange plates and,
thereafter, may be moved to advanced positions wherein they hold
the insertable portion of the cassette within the cassette
receiving space.
[0010] In accordance with another embodiment, there is provided a
system configured to circulate warmed or cooled thermal exchange
fluid through a body heat exchanger to warm or cool the body or a
human or animal subject, wherein the system comprises a first
display device which receives signals from one or more temperature
sensors and displays temperature data based on signals received
from said one or more temperature sensors. The first display device
is connectable, by wired or wireless connectivity, to a second
display device (e.g., a bedside monitor, central unit monitor,
remote monitor, etc.), so as to transmit said signals received from
said one or more temperature sensors from the first display device
to the second display device. The system further comprises
circuitry for minimizing or eliminating any effect of ambient
temperature on such signals as they are transmitted from the first
display device to the second display device. In some embodiments,
the signals transmitted from the first display device to the second
display device may comprise signals representative of sensed
temperatures, such as patient body temperature, temperature of
thermal exchange fluid flowing to the body heat exchanger,
temperature of thermal exchange fluid flowing from the body heat
exchanger, etc.
[0011] Disclosed herein is a system comprising: a heat exchange
catheter which comprises (i) a catheter body having a distal end,
(ii) a elongate member attached to the catheter body and extending
beyond its distal end, and (iii) at least one helically coiled tube
disposed on the elongate member and connected to delivery and
return lumen in the catheter body; and fluid cooling apparatus
comprising a refrigeration apparatus, cooling plates, and a
cassette connected to the delivery and return lumens of the
catheter body and operative to circulate a cooled thermal exchange
fluid through the cassette, into the catheter, through said at
least one helically coiled tube, out of the catheter and back into
the cassette, wherein the heat exchange catheter and fluid cooling
apparatus and said at least one helically coiled tube are sized,
configured and constructed to render the system capable of
delivering at least about 600 watts of cooling power. The fluid
cooling apparatus may be configured to deliver to the heat exchange
catheter a flow of heat exchange fluid that is cooled to a
temperature at or below 4.degree. C. at a rate of at least 600
mL/min at steady state, when up to 700 W of heat is being added to
the flowing saline as a result of heat exchange through the
catheter's heat exchanger. The fluid cooling apparatus may be
configured to deliver to the heat exchange catheter a flow of heat
exchange fluid that is cooled to a temperature at or below
4.degree. C. at a rate of from 200 mL/min to 240 mL/min at steady
state, when up to 70 W of heat is being added to the flowing saline
as a result of heat exchange through the catheter's heat exchanger.
The fluid cooling apparatus may be configured to deliver to the
heat exchange catheter a flow of heat exchange fluid that is warmed
to a temperature at or above 42.degree. C. at a rate of at least
400 mL/min at steady state, when up to 200 W of heat is being
removed from the flowing saline as a result of heat exchange
through the catheter's heat exchanger. The system may be configured
to deliver greater than or equal to 600 W of cooling power by
circulating heat exchange fluid that is cooled to a temperature at
or below 4.degree. C. through the heat exchange catheter at a
catheter pressure of about 60 PSI. The system may further comprise
heating apparatus useable for warming rather than cooling the heat
exchange fluid. Such heating apparatus may deliver greater than or
equal to 50 W of warming power by circulating heat exchange fluid
that is warmed to a temperature above 37.degree. C. through the
heat exchange catheter at a catheter pressure of about 40 PSI.
[0012] In another aspect, disclosed herein is a system comprising:
at least one set of thermal exchange plates which warm or cool a
heat exchange fluid for delivery to a body surface or endovascular
heat exchanger; a refrigeration unit for circulating cold
refrigerant through said at least one thermal exchange plate; at
least one heater for heating the thermal exchange plate; a
programmable controller; wherein the system further comprises a
bypass circuit for alternately circulating hot refrigerant from the
refrigeration unit through said at least one thermal exchange
plate; and wherein the controller is programmed to monitor the
power output of said at least one heater and, if said power output
exceeds a limit, to cause hot refrigerant to flow through the
bypass circuit and through said at least one thermal exchange
plate, thereby assisting said at least one heater in warming said
at least one thermal exchange plate. The controller may be further
programmed to incrementally or progressively reduce the amount of
hot refrigerant being circulated through said at least one thermal
exchange plate in the event that the power output of said at least
one heater falls below the limit until a target temperature has
been reached.
[0013] In another aspect, disclosed herein is a body heat exchange
system comprising: heater/cooler apparatus for alternately warming
or cooling a heat exchange fluid for delivery to a body heat
exchange device for surface or endovascular heat exchange in or on
the body of a subject; a pump for circulating the heat exchange
fluid through the body heat exchange device; a controller which is
programmed to selectively vary both the temperature and flow rate
of the heat exchange fluid to maintain the subject's body
temperature at or within a permissible range of a target body
temperature. The controller may be programmed such that, after a
body temperature of the subject has been warmed or cooled to a
target temperature, the controller will cause the system to
maintain said body temperature at or within a permissible variance
range of the target temperature by: holding the temperature of the
heat exchange fluid constant and varying the operation of the pump
to adjust the flow rate of heat exchange fluid through the catheter
as needed to maintain said body temperature at or within a
permissible variance range of the target temperature so long as the
speed of the pump does not exceed a maximum pump speed; and if the
pump exceeds the predetermined maximum pump speed, adjusting the
temperature of the heat exchange fluid such that said body
temperature at or within a permissible variance range of the target
temperature without exceeding the maximum pump speed. If it is
necessary to switch between cooling mode and warming mode in order
to maintain said body temperature at or within a permissible
variance range of the target temperature, the controller may, upon
making such switch, adjust the temperature of the heat exchange
fluid irrespective of whether the maximum pump speed has been
exceeded. The system may be combined with a body heat exchange
device. The body heat exchange device may comprise an endovascular
heat exchange catheter. The body heat exchange device comprises a
body surface heat exchange member.
[0014] In another aspect, disclosed herein is a body heat exchange
system comprising: heater/cooler apparatus for alternately warming
or cooling a heat exchange fluid for delivery to a body heat
exchange device for surface or endovascular heat exchange in or on
the body of a subject; a pump for circulating the heat exchange
fluid through the body heat exchange device; a temperature sensor
for sensing the temperature of the heat exchange fluid; a pressure
sensor for sensing the pressure of the heat exchange fluid and a
controller which receives a maximum pump speed set point and
signals from the temperature sensor and pressure sensor, said
controller being programmed to: a) establish current cold/warm
status of the heat exchange fluid based on the sensed temperature
of the heat exchange fluid; b) determining whether operation of the
pump at the maximum pump speed set point will cause
over-pressurization of the heat exchange fluid or
under-pressurization of the heat exchange fluid; and c) if it is
determined that operation of the pump at the maximum pump speed set
point will cause over-pressurization of the heat exchange fluid,
causing the maximum pump speed set point to change to an adjusted
maximum pump speed set point at which the pump may operate without
causing over-pressurization of the heat exchange fluid; or d) if it
is determined that operation of the pump at the maximum pump speed
set point will cause an under-pressurization of the heat exchange
fluid, causing the maximum pump speed set point to change to an
adjusted maximum pump speed set point at which the pump may operate
without causing under-pressurization of the heat exchange fluid.
The controller may be programmed to perform steps a through c
repeatedly. The controller may be programmed to repeat Steps a
through c at least once every 3 seconds. The controller may be
programmed to repeat Steps a through c every three seconds. The
controller may be programmed to cause the maximum pump speed set
point to change by applying a maximum pump speed set point
adjustment integrator. The application of the maximum pump speed
adjustment integrator may cause the maximum pump speed set point to
change slowly. The controller may be programmed to determine that
operation of the pump at the maximum pump speed set point will
cause over-pressurization of the heat exchange fluid based on
different maximum pressure limits for cold status and warm status.
The maximum pressure limit when operating with cold status heat
exchange fluid may, for example, be 40 psi and the maximum pressure
limit when operating with warm status heat exchange fluid may, for
example, be 60 psi. The controller may be programmed to establish
warm status in Step a if the sensed temperature of the heat
exchange fluid is above 19.5 degree C. and to establish cold status
in Step a if the sensed temperature of the heat exchange fluid is
not above 19.5 degrees C. The controller may be further programmed
to store the most recent prior maximum pump speed set point for
warm status and cold status. The controller may be further
programmed such that, if performance of Step a results in a change
from warm status to cold status, the controller will reset the
maximum pump speed set point to the most recent stored maximum pump
speed set point for cold status heat exchange fluid. The controller
may be further programmed such that, if performance of Step a
results in a change from cold status to warm status, the controller
will reset the maximum pump speed set point to the most recent
stored maximum pump speed set point for warm status heat.
[0015] In another aspect, disclosed herein is a method for
deterring reperfusion injury in a human or animal subject who is
suffering from ischemia and who undergoes reperfusion to relieve
the ischemia, said method comprising the steps of: cooling a body
temperature of the subject to a target temperature of 35 degrees C.
or below; and performing the reperfusion after the body temperature
of the subject has been cooled to the target temperature; and
maintaining the target temperature for a period of time after
reperfusion. The target temperature may be between 32 degrees C.
and 34 degrees C. The step of cooling a body temperature of the
subject to a target temperature of 35 degrees C. or below may be
performed in less than 30 minutes. The target temperature may be
maintained for a period of 1-5 hours after reperfusion. The step of
cooling a body temperature of the subject to a target temperature
of 35 degrees C. or below in less than 30 minutes may comprise:
inserting a heat exchange catheter into the subject's vasculature;
circulating heat exchange fluid through the heat exchange catheter
at a temperature and flow rate sufficient to cold said body
temperature to said target temperature in less than 30 minutes. The
heat exchange catheter may comprise (i) a catheter body having a
distal end, (ii) a elongate member attached to the catheter body
and extending beyond its distal end, and (iii) at least one
helically coiled tube disposed on the elongate member and connected
to delivery and return lumen in the catheter body; and the heat
exchange fluid may be circulated through the delivery lumen, at
least one helically coiled tube and return lumen of the catheter by
a cooling apparatus that comprises a refrigeration apparatus,
cooling plates, and a cassette which is connected to the delivery
and return lumens of the catheter body and may be operative to
circulate the cooled heat exchange fluid through the cassette, into
the catheter, through the delivery lumen, through said at least one
helically coiled tube, out of the return lumen and back into the
cassette; wherein the heat exchange catheter and fluid cooling
apparatus and said at least one helically coiled tube are sized,
configured and constructed to render the system capable of
delivering at least about 600 watts of cooling power. The fluid
cooling apparatus may be configured to deliver to the heat exchange
catheter a flow of heat exchange fluid that is cooled to a
temperature at or below 4.degree. C. at a rate of at least 600
mL/min at steady state, when up to 700 W of heat is being added to
the flowing saline as a result of heat exchange through the
catheter's heat exchanger. The fluid cooling apparatus may be
configured to deliver to the heat exchange catheter a flow of heat
exchange fluid that is cooled to a temperature at or below
4.degree. C. at a rate of from 200 mL/min to 240 mL/min at steady
state, when up to 70 W of heat is being added to the flowing saline
as a result of heat exchange through the catheter's heat exchanger.
The fluid cooling apparatus may be configured to deliver to the
heat exchange catheter a flow of heat exchange fluid that is warmed
to a temperature at or above 42.degree. C. at a rate of at least
400 mL/min at steady state, when up to 200 W of heat of heat is
being removed from the flowing saline as a result of heat exchange
through the catheter's heat exchanger. s added to the saline loop.
The fluid cooling apparatus may be configured to deliver to greater
than or equal to 600 W of cooling power by circulating heat
exchange fluid that is cooled to a temperature at or below
4.degree. C. through the heat exchange catheter at a catheter
pressure of about 60 PSI.
[0016] In another aspect, disclosed herein is a system comprising:
a heat exchange catheter which comprises (i) a catheter body having
a distal end, (ii) a elongate member attached to the catheter body
and extending beyond its distal end, and (iii) at least one
helically coiled tube disposed on the elongate member and connected
to delivery and return lumen in the catheter body; and fluid
cooling apparatus comprising a refrigeration apparatus, thermal
exchange plates through which refrigerant circulates having a
cassette receiving space between the thermal exchange plates, a
cassette connected to the delivery and return lumens of the
catheter body and operative to circulate a cooled thermal exchange
fluid through the cassette, into the catheter, through said at
least one helically coiled tube, out of the catheter and back into
the cassette; wherein the heat exchange catheter and fluid cooling
apparatus are configured to render the system capable of delivering
at least about 600 watts of cooling power.
[0017] A system according to claim 38 wherein the fluid cooling
apparatus are configured to deliver to the heat exchange catheter a
flow of heat exchange fluid that is cooled to a temperature at or
below 4.degree. C. at a rate of at least 600 mL/min at steady
state, when up to 700 W of heat is being added to the flowing
saline as a result of heat exchange through the catheter's heat
exchanger. The fluid cooling apparatus may be configured to deliver
to the heat exchange catheter a flow of heat exchange fluid that is
cooled to a temperature at or below 4'C at a rate of from 200
mL/min to 240 mL/min at steady state, when up to 70 W of heat is
being added to the flowing saline as a result of heat exchange
through the catheter's heat exchanger. The fluid cooling apparatus
may be configured to deliver to the heat exchange catheter a flow
of heat exchange fluid that is warmed to a temperature at or above
42.degree. C. at a rate of at least 400 mL/min at steady state,
when up to 200 W of heat is being removed from the flowing saline
as a result of heat exchange through the catheter's heat exchanger.
s added to the saline loop. The fluid cooling apparatus are
configured to deliver greater than or equal to 600 W of cooling
power by circulating heat exchange fluid that is cooled to a
temperature at or below 4.degree. C. through the heat exchange
catheter at a catheter pressure of about 60 PSI. The system may
further comprise apparatus useable for warming rather than cooling
the heat exchange fluid. The system may be configured to deliver
greater than or equal to 50 W of warming power by circulating heat
exchange fluid that is warmed to a temperature above 37.degree. C.
through the heat exchange catheter at a catheter pressure of about
40 PSI. The system may further comprise at least one heater for
warming the thermal exchange plates and a controller programmed to
monitor the power output of said at least one heater and, if said
power output exceeds a limit, to cause hot refrigerant to flow
through the bypass circuit and through said at least one thermal
exchange plate, thereby assisting said at least one heater in
warming said at least one thermal exchange plate. The controller
may be further programmed to incrementally or progressively reduce
the amount of hot refrigerant being circulated through said at
least one thermal exchange plate in the event that the power output
of said at least one heater falls below the limit until a target
temperature has been reached. The system may further comprise at
least one heater for warming the thermal exchange plates, a pump
for pumping the heat exchange fluid at varied flow rates, and a
controller programmed to selectively vary both the temperature and
flow rate of the heat exchange fluid to maintain the subject's body
temperature at or within a permissible range of a target body
temperature. The controller may be programmed such that, after a
body temperature of the subject has been warmed or cooled to a
target temperature, the controller will cause the system to
maintain said body temperature at or within a permissible variance
range of the target temperature by: holding the temperature of the
heat exchange fluid constant and varying the operation of the pump
to adjust the flow rate of heat exchange fluid through the catheter
as needed to maintain said body temperature at or within a
permissible variance range of the target temperature so long as the
speed of the pump does not exceed a maximum pump speed; and if the
pump exceeds the predetermined maximum pump speed, adjusting the
temperature of the heat exchange fluid such that said body
temperature at or within a permissible variance range of the target
temperature without exceeding the maximum pump speed. If it is
necessary to switch between cooling mode and warming mode in order
to maintain said body temperature at or within a permissible
variance range of the target temperature, the controller may, upon
making such switch, adjust the temperature of the heat exchange
fluid irrespective of whether the maximum pump speed has been
exceeded. The system may further comprise at least one heater for
warming the thermal exchange plates, a pump for pumping the heat
exchange fluid at varied flow rates, a temperature sensor for
sensing the temperature of the heat exchange fluid, a pressure
sensor for sensing the pressure of the heat exchange fluid, and a
controller which receives a maximum pump speed set point and
signals from the temperature sensor and pressure sensor, said
controller being programmed to: a) establish current cold/warm
status of the heat exchange fluid based on the sensed temperature
of the heat exchange fluid; b) determine whether operation of the
pump at the maximum pump speed set point will cause
over-pressurization of the heat exchange fluid or
under-pressurization of the heat exchange fluid; and c) if it is
determined that operation of the pump at the maximum pump speed set
point will cause over-pressurization of the heat exchange fluid,
causing the maximum pump speed set point to change to an adjusted
maximum pump speed set point at which the pump may operate without
causing over-pressurization of the heat exchange fluid; or d) if it
is determined that operation of the pump at the maximum pump speed
set point will cause an under-pressurization of the heat exchange
fluid, causing the maximum pump speed set point to change to an
adjusted maximum pump speed set point at which the pump may operate
without causing under-pressurization of the heat exchange fluid.
The controller may be programmed to perform steps a through c
repeatedly. The controller may be programmed to repeat Steps a
through c at least once every 3 seconds. The controller may be
programmed to repeat Steps a through c every three seconds. The
controller may be programmed to cause the maximum pump speed set
point to change bay applying a maximum pump speed set point
adjustment integrator. The application of the maximum pump speed
adjustment integrator may cause the maximum pump speed set point to
change slowly. The controller may be programmed to determine that
operation of the pump at the maximum pump speed set point will
cause over-pressurization of the heat exchange fluid based on
different maximum pressure limits for cold status and warm status.
The maximum pressure limit when operating with cold status heat
exchange fluid may be, for example, 40 psi and the maximum pressure
limit when operating with warm status heat exchange fluid may be,
for example, 60 psi. The controller may be programmed to establish
warm status in Step a if the sensed temperature of the heat
exchange fluid is above 19.5 degree C. and to establish cold status
in Step a if the sensed temperature of the heat exchange fluid is
not above 19.5 degrees C. The controller may be further programmed
to store the most recent prior maximum pump speed set point for
warm status and cold status. The controller may be further
programmed such that, if performance of Step a results in a change
from warm status to cold status, the controller will reset the
maximum pump speed set point to the most recent stored maximum pump
speed set point for cold status heat exchange fluid. The controller
may be further programmed such that, if performance of Step a
results in a change from cold status to warm status, the controller
will reset the maximum pump speed set point to the most recent
stored maximum pump speed set point for warm status heat. The
system may be configured to deliver greater than or equal to 700 W
of cooling power.
[0018] In another aspect; disclosed herein is a system usable for
circulating warmed or cooled thermal exchange fluid through a
plurality of different changeable heat exchange components which
are available and alternately connectable to the system, said
system comprising: thermal exchange fluid warming/cooling apparatus
for warming, cooling or alternately warming and cooling the thermal
exchange fluid; a pump for pumping the thermal exchange fluid; a
controller; and apparatus for communicating, to the controller,
identifying data which is associated with a selected one of said
plurality of changeable heat exchange components; wherein the
controller is programmed to assign, on the basis of the identifying
data, operational variables for use in connection with the selected
one of said plurality of different changeable heat exchange
components and to thereafter control the operation of at least one
of said thermal exchange fluid warming/cooling apparatus and said
pump in accordance with the assigned operational variables. The
thermal exchange fluid warming/cooling apparatus may comprise an
extracorporeal heat exchange system through which the thermal
exchange circulates. The apparatus for communicating to the
controller may comprise apparatus for communicating to the
controller machine readable identifying data that is encoded on or
in the selected one of said plurality of different changeable heat
exchange components. The plurality of different changeable heat
exchange components may be selected from: endovascular heat
exchange catheters, body surface heat exchangers, tubings or tubing
sets and cassettes through which the thermal exchange fluid
circulates. The plurality of different changeable heat exchange
components may comprise a plurality of different types of heat
exchange catheters or a plurality of different cassettes each of
which is used in connection with a different type of heat exchange
catheter and the operational variables may comprise at least one
of: minimum fluid pressure, maximum fluid pressure, minimum fluid
flow rate, maximum fluid flow rate, number of temperature sensors,
location(s) of temperature sensor(s), maximum temperature, minimum
temperature and control algorithm to be used.
[0019] In another aspect, disclosed herein is a system for warming
or cooling the body of a human or animal subject, such system
comprising: an extracorporeal control console having a warming
and/or cooling apparatus, a pump and a controller and a cassette
having a fluid flow path that is connectable to a body heat
exchanger positionable on or in a subject's body, such cassette
being positionable at an operating position on or in the
extracorporeal unit while connected to a body heat exchanger, such
that a) the pump will circulate heat exchange fluid through the
cassette's heat exchange fluid flow path, through the connected
body heat exchanger and back into the cassette's heat exchange
fluid flow path and b) the warming and/or cooling apparatus will
warm and/or cool the circulating heat exchange fluid. Such cassette
may further comprise an electronic storage medium containing
machine readable encoded information. The extracorporeal control
console may further comprise a reader which receives and reads the
cassette's encoded information and the controller may use the
cassette's encoded information, as read by the reader, to control
operation of one or more components of the system. In some
embodiments, the cassette is useable or approved for use with only
a single body heat exchanger type and the encoded information
either includes, or causes the controller to select and use, a
control algorithm, operational setting or parameter that is
suitable for that single body heat exchanger type. In some
embodiments the cassette may be useable or approved for use with a
plurality of different body heat exchanger types and the encoded
information includes, or causes the controller to select and use, a
control algorithm, operational setting or parameter that is
suitable for any of the body heat exchanger types useable or
approved for use with the cassette. In some embodiments the
extracorporeal control console may be alternately useable with a
first cassette that is useable or approved for use with only a
single body heat exchanger type and has encoded information that
either includes, or causes the controller to select and use, a
control algorithm, operational setting or parameter that is
suitable for that single body heat exchanger or a second cassette
having a fluid flow path that is connectable to a body heat
exchanger, such second cassette being alternately positionable,
instead of said cassette, in said operating position such that a)
the pump will circulate heat exchange fluid through the second
cassette's heat exchange fluid flow path, through the connected
body heat exchanger and back into the second cassette's heat
exchange fluid flow path and b) the warming and/or cooling
apparatus will warm and/or cool the circulating heat exchange
fluid; the second cassette further comprising an electronic storage
medium containing machine readable encoded information; wherein the
reader receives and reads the second cassette's encoded
information; and wherein the controller uses the second cassette's
encoded information, as read by the reader, to control operation of
one or more components of the system. Such second cassette may be
useable or approved for use with a plurality of different body heat
exchanger types and the encoded information includes, or causes the
controller to select and use, a control algorithm, operational
setting or parameter that is suitable for any of the body heat
exchanger types useable or approved for use with the second
cassette. Such plurality of approved body heat exchangers may have
a recommended pressure limit and the second cassette's encoded
information may include, or cause the controller to select and use,
a control algorithm, operational setting or parameter that limits
the speed of the pump such that heat exchange fluid pressure within
the body heat exchanger connected to the second cassette will not
exceed a maximum pressure limit for that body heat exchanger,
irrespective of which of the plurality of body heat exchanger types
is connected to the second cassette. In some embodiments, the
second cassette's encoded information may distinguish the second
cassette from the cassette and wherein the controller is
pre-programmed to select and use, in the basis of that encoded
information, a control algorithm, operational setting or parameters
suitable for the body heat exchanger(s) that are useable or
approved for use of either the cassette or the second cassette,
depending on which is presently inserted in the operating position.
The electronic storage medium may comprise a medium type selected
from: non-volatile random access memory (RAM); non-volatile flash
memory; electrically erasable programmable read-only memory
(EEPROM); ferroelectric random access memory (FRAM); a
chip-embedded storage medium and a microchip-embedded storage
medium. The cassette's encoded information may include an
indication that the cassette meets a prerequisite requirement and
the extracorporeal unit will proceed with warming or cooling of the
heat exchange fluid only if the reader has determined that the
encoded information includes said indication that the cassette
meets a prerequisite requirement. An indication that the cassette
meets a prerequisite requirement may comprise at least one of: an
expiration date and the absence of an indication that the cassette
has been previously used. The body heat exchanger(s) may comprise
heat exchange catheters or body surface heat exchangers.
[0020] In another aspect, disclosed herein is a body temperature
management system comprising: a body heat exchanger positionable on
or in a subject's body,
[0021] a heat exchange fluid warmer and/or cooler; a heat exchange
fluid pump which circulates heat exchange fluid through the heat
exchange fluid warmer and/or cooler and through the body heat
exchanger; a sensor for sensing the subject's actual body
temperature; a user interface configured to receive a user-input
patient temperature set point; and a controller which receives
signals indicating the user-input patient temperature and the
currently-sensed actual body temperature; wherein the controller is
programmed to control the heat exchange fluid warmer or cooler
and/or the heat exchange fluid pump to initially cause the system
to perform a first phase of warming or cooling, during which the
heat exchange fluid circulates through the body heat exchanger at
temperature and flow rate to cause the sensed actual body
temperature to increase or decrease until the sensed actual body
temperature reaches a predetermined interim temperature, said
interim body temperature being less than the user-input patient
temperature set point if the subject is being warmed or greater
than the patient temperature set point if the subject is being
cooled; and, thereafter, cause the system to perform a second phase
of warming or cooling to increase or decrease from the interim
temperature to the user input temperature set point at one or more
rates which are slower than said initial rate, until the sensed
actual body temperature becomes equal to the user-input patient
temperature set point without substantially overshooting the user
input patient temperature set point; and, thereafter, cause the
system to perform a third phase of warming or cooling during which
the temperature and/or flow rate of the heat exchange fluid is/are
periodically adjusted as needed to maintain the sensed actual body
temperature substantially equal to the user-input patient
temperature set point. The user interface may allow a user to
select a rate of warming or cooling and the controller will cause
the system to perform said first, second and third phases only when
the selected rate of warming or cooling is greater than a
triggering rate. Such triggering rate may be greater than 0.1
degrees C. per hour. The user interface may allow the user to
select a maximum rate of warming or cooling and the controller will
cause the system to perform said first, second and third phases
when the maximum rate is selected. During the first phase, the
temperature and/or flow rate of the heat exchange fluid or pump
speed may be periodically adjusted as needed to cause the sensed
actual body temperature to increase or decrease until the sensed
actual body temperature reaches a predetermined interim
temperature. During the second phase the temperature and/or flow
rate of the heat exchange fluid or pump speed may be periodically
adjusted as needed to cause the sensed actual body temperature to
increase or decrease to the user input temperature set point.
During the first phase the temperature and flow rate of the heat
exchange fluid may be substantially constant and not varied based
on sensed changes in the actual patient temperature. During the
second phase, the actual patient body temperature may warm or cool
at a rate of 0.05 degrees C. per hour to 0.1 degrees C. per hour.
The user interface may allow the user to select a patient
temperature set point and the controller will cause the system to
perform said first, second and third phases only when the patient
temperature set point is greater than a triggering patient
temperature set point. Such triggering patient temperature set
point may be greater than 37.8 degrees C.
[0022] Still further aspects and details of the present invention
will be understood upon reading of the detailed description and
examples set forth herebelow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The following detailed description and examples are provided
for the purpose of non-exhaustively describing some, but not
necessarily all, examples or embodiments of the invention, and
shall not limit the scope of the invention in any way.
[0024] FIG. 1 shows one embodiment of an endovascular heat exchange
system comprising an endovascular heat exchange catheter, an
extracorporeal control console and a tubing/cassette/sensor module
assembly useable for operatively connecting the heat exchange
catheter to the control console.
[0025] FIG. 2A is a left/front perspective view of the control
console with its access cover in an open position.
[0026] FIG. 2B is a left/rear perspective view of the control
console.
[0027] FIG. 3 is an exploded view of the control console with its
access cover in an open position and the tubing/cassette/sensor
module assembly staged for insertion in, and operative connection
to, the control console.
[0028] FIG. 4 is a top (perspective) view of the control console
with its access cover in an open position and the
tubing/cassette/sensor module assembly operatively inserted in and
connected to the control console.
[0029] FIG. 5 is a top (plan) view of the control console with its
access cover in an open position and the tubing/cassette/sensor
module assembly operatively inserted in and connected to the
control console.
[0030] FIG. 6 is a right/front perspective view of the control
console with its housing and access cover removed.
[0031] FIG. 7 is a left cross-sectional view of the control
console.
[0032] FIG. 8 is a top cross-sectional view of the control
console.
[0033] FIG. 9 is a right cross-sectional view of the control
console.
[0034] FIG. 10 is a perspective view of a thermal exchange engine
component of the control console.
[0035] FIG. 11 is a bottom/perspective view of a thermal exchange
plate assembly of the thermal exchange engine.
[0036] FIG. 12 is a top/perspective view of the thermal exchange
plate assembly.
[0037] FIG. 13 is a top (plan) view of the thermal exchange plate
assembly of the thermal exchange engine.
[0038] FIG. 14 is disassembled view of one of the thermal exchange
plates of the thermal exchange plate assembly, exposing a
vertically oriented serpentine refrigerant flow path formed in the
inner surface of the plate.
[0039] FIG. 15 is a rear view of the thermal exchange plate
assembly with the outer plate and heater removed.
[0040] FIG. 16 is a partially disassembled rear perspective view of
with the thermal exchange plate wherein rear plates have been
removed so as to expose secondary fluid flow channels useable for
optional non-cassette warming/cooling of a fluid.
[0041] FIG. 17 is a top view of the fully assembled thermal
exchange plate assembly.
[0042] FIG. 18 is a schematic diagram illustrating the functional
lay out of the thermal exchange engine.
[0043] FIG. 19 is a front perspective view of the pump assembly of
extracorporeal control console.
[0044] FIG. 20 is a partially disassembled view of the pump
assembly wherein the cover has been removed.
[0045] FIG. 20A is a separate view of a barrel-shaped guide roller
of the pump assembly.
[0046] FIG. 21 is a top view of the pump assembly.
[0047] FIG. 22 is a rear perspective view of the pump assembly
disposed in an operative configuration.
[0048] FIG. 23 is a rear perspective view of the pump assembly
disposed in a loading configuration.
[0049] FIG. 24 is a rear perspective view of the
tubing/cassette/sensor module assembly of the endovascular heat
exchange system.
[0050] FIG. 25 is a front perspective view of the
tubing/cassette/sensor module assembly.
[0051] FIG. 26 is a side view of the cassette and pump tubing
portions of the tubing/cassette/sensor module assembly disposed in
an open/locked configuration useable for insertion and
operation.
[0052] FIG. 27 is a rear perspective view of the cassette and pump
tubing portions of the tubing/cassette/sensor module assembly
disposed in a closed configuration prior to insertion and
operation.
[0053] FIG. 28 is a cross sectional view of the cassette portion of
the tubing/cassette/sensor module assembly.
[0054] FIG. 29 is an exploded view of the sensor module portion of
the tubing/cassette/sensor module assembly.
[0055] FIG. 30 is a schematic diagram of an endovascular heat
exchange system. (convert to black/white formalize)
[0056] FIG. 31 is a schematic diagram of a heat exchange system
capable of providing endovascular and/or body surface heat
exchange.
[0057] FIG. 32 shows the heat exchange catheter of the system of
FIG. 1.
[0058] FIG. 32A is a cross-sectional view through line A-A of FIG.
32.
[0059] FIG. 32B is a cross-sectional view through line B-5 of FIG.
32.
[0060] FIGS. 33A through 330 show certain components of the
endovascular heat exchange catheter embodiment of FIG. 32.
Specifically, FIG. 33A is a side view of the elongate member; FIG.
33B is a side view of the heat exchange tube and FIG. 33C is a side
view of an optional elongate luminal member and the distal tip
member.
[0061] FIG. 34 is a flow diagram showing one example of a process
by which a body heat exchange system may employ hot refrigerant
from its cooling engine to augment the warming effect of resistance
heaters.
[0062] FIG. 35 is a flow diagram showing one example of a process
by which a body heat exchange system may combine variations in heat
exchange fluid flow rate with variations in heat exchange fluid
temperature for precise maintenance of a target body
temperature.
[0063] FIG. 36 is a flow diagram showing one example of a process
by which a body heat exchange system may optimize pump speed and
heat exchange fluid pressure during operation with either warm or
cool heat exchange fluid.
[0064] FIG. 37 is a flow diagram showing one embodiment of a
process for using a heat exchange catheter system to deter
reperfusion injury in a subject who is suffering from an ischemic
event that is treatable by a reperfusion procedure or
administration of a reperfusion agent (e.g., thrombolytic
drug).
[0065] FIG. 38 is a flow diagram showing one example of a process
by which a system that is configured and programmed to operate with
more than one type of heat exchange device and/or body heat
exchange device may detect the particular type of heat exchange
device that has been connected to the system and adjust the
system's operation in accordance with the detected type of heat
exchange device and/or body heat exchange device.
[0066] FIG. 39 shows the system of FIG. 3 in combination with
partial views of a plurality of heat exchange catheters, any of
which may be connected to and used in conjunction with the
system.
[0067] FIG. 40 is a graph of body temperature versus time during a
body warming process using a body heat exchange system as described
herein.
[0068] FIG. 41 is a flow diagram showing steps in one embodiment of
a body warming process using a body heat exchange system as
described herein.
DETAILED DESCRIPTION
[0069] The following detailed description and the accompanying
drawings to which it refers are intended to describe some, but not
necessarily all, examples or embodiments of the invention. The
described embodiments are to be considered in all respects only as
illustrative and not restrictive. The contents of this detailed
description and the accompanying drawings do not limit the scope of
the invention in any way.
[0070] FIG. 1 shows one embodiment of an endovascular heat exchange
system 10 in operation to control the body temperature of a human
subject. This endovascular heat exchange system 10 generally
comprises an endovascular heat exchange catheter 12, an
extracorporeal control console 14, a tubing/cassette/sensor module
assembly 60 or cassette assembly which facilitates connection of
the catheter 12 to the control console 14 and a temperature sensor
TS. In at least some embodiments, the catheter 12,
tubing/cassette/sensor module assembly 60 or cassette assembly and
temperature sensor TS may be disposable items intended for a single
use, while the control console 14 may be a non-disposable device
intended for multiple uses.
[0071] In the embodiment shown, the endovascular heat exchange
catheter 12 comprises an elongate catheter body 16 and a heat
exchanger 18 positioned on a distal portion of the catheter body
16. Inflow and outflow lumens (not shown) are present within the
catheter body 16 to facilitate circulation of a thermal exchange
fluid (e.g., sterile 0.9% sodium chloride solution or other
suitable thermal exchange fluid) through the heat exchanger 18.
Optionally, the catheter shaft 16 may also include a working lumen
(not shown) which extends through the catheter body 16 and
terminates distally at an opening in the distal end of the catheter
body 16. Such working lumen may serve as a guidewire lumen to
facilitate insertion and position of the catheter 12 and/or may be
used after insertion of the catheter 12 for delivery of fluids,
medicaments or other devices. For example, as shown in FIG. 1, in
some embodiments, the temperature sensor TS may be inserted through
the catheter's working lumen and advanced out of the distal end
opening to a location beyond the distal end of the catheter body
16. Alternatively, in other embodiments, the temperature sensor TS
may be positioned at various other locations on or in the subject's
body to sense the desired body temperature(s). Various heat
exchange catheters may be used in the embodiments described
herein.
[0072] With reference to FIGS. 32 through 33C, the elongate body 16
of the catheter 12 may comprise a proximal body 1300 and an
assembly 1302 which comprises the heat exchanger 1304 attached to
and/or extending distally from the proximal body 1300. As seen in
the cross sectional view of FIG. 32B, in this particular
embodiment, the proximal body 1300 has three lumens, an inflow
lumen 1500a, an outflow lumen 1500b and an optional through lumen
1500c.
[0073] A hub 1700 is mounted on the proximal end PE of the proximal
catheter body 1300. The hub 1700 has an inflow connector 30000 that
is connected to the inflow lumen 1500a of the catheter body 1300
and an outflow connector 32000 that is connected to the outflow
lumen 1500b of the proximal catheter body 1300. A through lumen
port 2200 on the hub 1700 is connected to the through lumen
1500c.
[0074] The heat exchanger 1304 of this catheter embodiment
comprises at least first and second coiled heat exchange tube
segments 1307a, 1307b. In some embodiments, additional (e.g.,
third, fourth) heat exchange tube segments may be used. The heat
exchange tube segments 1307a, 1307b may be formed of any suitable
material. In the particular example shown, the heat exchange tube
segments 1307a, 1307b may be advantageously formed of a
noncompliant polymeric material, such as polyethylene terephthalate
(PET), Pebax, Polyolefin, Polyurethane and/or Nylon, or other
suitable compliant or noncompliant material and may be formed of a
single tube or one or more tubes. In some embodiments the heat
exchange tube segments 1307a, 1307b may expand and collapse
depending on whether or not they are filled with fluid and, in such
embodiments, the heat exchange tube segments 1307a, 1307b may be
referred to a "balloons." For some applications, the heat exchange
tube segments 130fa, 1307b may have outer diameters in the range of
2 mm-19 mm and wall thicknesses in the range of 0.0127 mm-0.1
mm.
[0075] In this example, the proximal end of the first tube segment
1307a is connected to the inflow lumen 1500a and the proximal end
of the second tube 1307b segment is connected to the outflow lumen
1500b. The distal ends of the first and second tube segment 1307a,
1307b are directly or indirectly in fluidic connection with each
other such that heat exchanger fluid that has flowed in the distal
direction through the first tube segment 1307a will then return in
the proximal direction through the second tube segment 1307b. The
distal ends of the heat exchange tube segment 1307a, 1307b are
connected to the inflow and outflow connectors 30000, 32000 of the
catheter 12
[0076] As seen in detail in FIGS. 33A-33C, the heat exchange
assembly 1302 may comprise a spine or elongate member 4000 and at
least one heat exchange member 1307 disposed on the spine or
elongate member 4000. The heat exchange assembly 1302 is attached
to and extends distally from the proximal body 1300, as shown. An
introducer sheath may be used to introduce the catheter into a
patient's body. Alternatively, the catheter may be introduced
without using an introducer sheath.
[0077] The term "elongate member," may mean, in at least some
embodiments, a member, e.g., a spine or similar structure, which
extends from a catheter body and upon which at least one heat
exchange member is disposed. In at least some embodiments, the
elongate member 4000 is distinguishable from the proximal body 1302
on the basis of one or more differences in structure or physical
property. In the particular embodiment shown, the elongate member
4000 comprises an elongate, generally C-shaped member having
receiving features 4600 which comprise spaced-apart transverse
notches, recesses or grooves formed along the open side of the
generally C-shaped member. The heat exchange member(s) 1307 may be
inserted in these recessed, groove, or notch-type receiving
features 4600 such that the helical loops extend around the closed
side of the generally C-shaped elongate member 4000. The heat
exchange member(s) 1307 may be secured to the receiving features
4600 by adhesive or other suitable means.
[0078] Non-limiting examples of other heat exchange catheters and
related apparatus that may be used are described in U.S. Pat. No.
9,492,633, and United States Patent Application Publications Nos.
2013/0090708, 2013/0178923, 2013/0079855, 2013/0079856,
2014/0094880, 2014/0094882, 2014/0094883, and unpublished,
copending U.S. patent application Ser. Nos. 15/395,858, 15/395,923
and 15/412,390, the entire disclosure of each such patent and
application being expressly incorporated herein by reference. Other
examples of catheters that may be used in this invention include
those commercially available from ZOLL Circulation, Inc., San Jose,
Calif., such as the Cool Line.RTM. Catheter, Icy.RTM. Catheter,
Quattro.RTM. Catheter: Solex 7.RTM. Catheter, InnerCool.RTM. RTx
Accutrol Catheter and the InnerCool RTx Standard Catheter.
Additionally incorporated herein by reference is the entire
disclosure of U.S. patent application Ser. No. 15/594,539 entitled
Advanced Systems and Methods for Patent Body Temperature Control,
filed on May 12, 2017.
[0079] The extracorporeal control console 14 generally comprises a
main housing 20 and a console head 24. As described in detail
herebelow, the main housing 20 contains various apparatus and
circuitry for warming/cooling thermal exchange fluid to controlled
temperature(s) and for pumping such warmed or cooled thermal
exchange fluid through the catheter 18 to effectively modify and/or
control the subject's body temperature. The console head 24
comprises a display device or user interface, such as a touch
screen system, whereby certain information may be input by, and
certain information may be displayed to, users of the system 10. On
the housing 20 there are provided a first connection port 40 for
connection of a temperature sensor TS that is inserted through the
heat exchange catheter 12 as shown in FIG. 1 as well as other
connection ports 36, 38 for connection of additional or alternative
types of temperature sensors and/or other apparatus.
[0080] The tubing/cassette/sensor module assembly 60 or cassette
assembly, which is seen in further detail in FIGS. 3-5, generally
comprises a sensor module 34, an inflow conduit 32, inflow
connector 33, outflow conduit 30, outflow connector 35, temperature
lead TL, temperature lead connector 31, pressure lead PL, cassette
64, cassette housing 62 and peristaltic pump tubing 65. In certain
embodiments, the pump tubing may be made of materials suitable for
continuous or intermittent use over a desired period of time, e.g.,
suitable for use over a period of time from 20 minutes to 12 hours
or 1 hour to 7 days or longer. Nonlimiting examples of such
material include Elastollan.RTM. and Norprene.RTM. and other
similar materials.
[0081] FIGS. 2A through 9 show further detail of the components
within the housing 20 and the manner in which the
tubing/cassette/sensor module assembly 60 or cassette assembly is
inserted in and connected to the control console 14. As seen in
FIGS. 2A through 3, the control console 14 has an openable/closable
access cover 42 which, when opened, permits insertion of the
cassette 64 into a cassette receiving space 66 as well as other
connection of the tubing/cassette/sensor module assembly 60 or
cassette assembly to other components of the system described
below. A magnet 44 on the access cover 42 interacts with a magnetic
sensor 46 to emit signal(s) indicating whether the access cover 42
is opened or closed. Other sensors and detection mechanisms known
to persons having skill in the art may be utilized as well. The
system controller located in the housing 20 may be programmed to
halt running of certain components of the system when the access
cover 44 is opened. On the rear of the housing 20, there is
provided a power switch 50 and a power cord holder 52. A bracket 48
is provided on an upstanding portion of the housing which supports
the console head 24 for hanging a bag or container of fluid.
[0082] As seen in FIGS. 3 through 5, with the access cover 42 in an
open position, the cassette 64 is insertable downwardly into the
cassette receiving space 66 and the pump tubing 65 is insertable
into a tubing raceway 72 of pump 70.
[0083] FIGS. 6 through 10 provide partially disassembled and
sectional views which reveal various components of the control
console 14. The thermal exchange engine 108, includes a
refrigeration system which comprises a compressor 92, stepper motor
for turning an expansion valve 106, fans 96 and 104, condenser 98
and compressor heat sink 100. The heat sink may be a metallic,
e.g., aluminum, cylindrical enclosure that surrounds the
compressor. The heat sink is in contact with the compressor and
increases the surface area of the compressor to facilitate enhances
removal of heat from the compressor. The thermal exchange system is
powered by power supply 94. Thermal exchange plates 80, are
provided to alternately warm or cool thermal exchange fluid as it
circulates through a cassette 64 that has been inserted in the
cassette receiving space 66 between the thermal exchange plates.
Resistance heaters 82 are mounted on the plates 80 for warming the
plates 80 when operating in a warming mode and a refrigerant, such
as Refrigerant R143a (1,1,1,2 Tetrafluoroethane) is compressed by
the compressor 92 and circulated through the condenser 98 and
plates 80 to cool the plates when operating in a cooling mode. In
certain embodiments, heaters may include a thermal cutout switch
for automatically turning one or more of the heaters off if the
heaters were to overheat.
[0084] When operating in a cooling mode, the thermal exchange
engine 108 emits heat. Fans 96 and 104 circulate air through air
plenums or spaces adjacent to the thermal exchange engine 108 and
over surfaces of the compressor and compressor heat sink 100 to
exhaust emitted heat and maintain the thermal exchange engine 108
at a suitable operating temperature. Specifically, in the
embodiment shown, air enters air intake 84 through filter 90,
circulates through the device as indicated by arrows on FIGS. 7 and
8, and is exhausted through an air outlet or exhaust vent on a side
of the console 14 as shown specifically in FIG. 8. The airflow
pathway is specifically configured to minimize the amount of sound
that escapes from the system via the airflow pathway and is audible
to a user or patient. The airflow pathway includes a convoluted
pathway or channels which provide reflective surfaces to contain
the acoustic energy within the cooling engine enclosure. Also, the
interior of the intake and exhaust ducts and pathway or channels
are lined with an acoustically absorbent material, e.g.,
open-celled elastomeric foam. The combination of these features
minimizes the amount of sound, such as that generated by the fans
and compressor, that escapes the system. For example, in certain
embodiments, the operating noise level of a system may not exceed
65 dBA measured at a distance of 1 m from the system when the
system is in maximum cooling and 58 dBA measured at a distance of 1
m from the system when the system is in maintenance or warming.
[0085] The structure and function of the thermal exchange plates
may be appreciated in further detail in FIGS. 11 through 17.
Thermal exchange plates 80 may be positioned on either side of the
cassette receiving space 66. The thermal exchange plates are
connected on their ends forming a cassette receiving space or slot
between the plates. The thermal exchange plates may be referred to
as a thermal exchange plate assembly. Resistance heaters 82 are
mounted in one or more of plates 80 and are useable to warm the
plates 80 when warming of the circulating thermal exchange fluid is
desired. In certain embodiments, vertically oriented, serpentine or
convoluted, refrigerant flow channels 120 are formed within the
plates 80. This orientation and design of the refrigerant flow
channels help maximize and realize the cooling power of the cooling
engine, For example, the plates are configured to evaporate the
refrigerant moved by a 900 W compressor (e.g., a Masterflux
compressor) within a cooling engine envelope sized to fit within
the housing 20, as illustrated in the figures herein. In each
plate, cold refrigerant circulates through refrigerant inlet 112,
through the refrigerant flow channels 120 and out of refrigerant
outlet 114. The refrigerant changes phase from a liquid
substantially to a gas while flowing through the refrigerant flow
channels 120, thereby cooling the plates 80. Such warming or
cooling of the plates 80, in turn causes warming or cooling of
thermal exchange fluid being circulated through a cassette
positioned within the cassette receiving space 66. Temperature
sensors 110, e.g., thermistors, may be located on the plates to
detect the temperature of the plates. Signals from the temperature
sensors may be fed back to the system controller or control
processor to control warming and/or cooling (e.g., to prevent
freezing) by the system.
[0086] Optionally, as shown in the views of FIGS. 15 and 16, the
thermal exchange plates 80 may incorporate channels 125 for
circulation of a thermal exchange fluid directly through the
plates. For example, a desired thermal exchange fluid may circulate
in inlet 122, through horizontal flow channels 125 and out of
outlet 124. A single inlet port may be used to supply thermal
exchange fluid to both plates as the fluid passes from a first
plate to the second plate, through channels located at the ends of
the thermal exchange plate assembly, and exits the thermal exchange
plate assembly through a single outlet port. A drain port 127 may
be provided for draining residual thermal exchange fluid or
flushing debris from the flow channels 125, when required. These
channels 125 may be used for cooling or warming a secondary thermal
exchange fluid simultaneously with, or as an alternative to, the
warming or cooling of a heat exchange fluid circulating through a
cassette 64 inserted within the cassette receiving space 66. In
some embodiments, the channels 125 may be configured to provide a
volume flow of secondary thermal exchange fluid that differs from
the volume flow of thermal exchange fluid which circulates through
the cassette 64. For example, a cassette 64 may be inserted in the
cassette receiving space 66 and used for circulating a relatively
small volume of warmed or cooled thermal exchange fluid (e.g.,
sterile saline solution) through an endovascular catheter 12 and,
simultaneously or alternately, the channels 125 may be used to warm
or cool a larger volume of a secondary thermal exchange fluid
(e.g., nonsterile water) for circulation through body surface
cooling device(s) such as surface cooling pad(s), blanket(s),
garment(s), etc. Further details and examples of such concurrent or
separate use of endovascular and body surface temperature exchange
are described in copending U.S. patent application Ser. No.
15/412,390 entitled Managing Patient Body Temperature Using
Endovascular Heat Exchange in Combination With Body Surface Heat
Exchange, the entire disclosure of which is expressly incorporated
herein by reference.
[0087] A schematic diagram of an embodiment of a thermal exchange
engine or refrigeration loop useable in the systems described
herein is shown in FIG. 18. This embodiment has a high side HS and
a low side LS. The components shown in this diagram include
superheat temperature sensor 130, thermal exchange plate
evaporators 132, electric heaters 134, an electronic expansion
valve, compressor 140, counterflow heat exchanger 142, filter/drier
sight glass 138, and electronic expansion valve 144. In the normal
operational state of the cooling engine, the hot gas bypass valve
136 is closed, the compressor 140 is running, and refrigerant flows
through the system as follows. First, refrigerant exits the
compressor in the gaseous phase at high pressure (typically 8-14
bar) and high temperature (typically 100 to 130 degrees F.) and
enters the condenser. In the condenser, heat is transferred from
the refrigerant, causing it to condense into it's liquid phase and
cool further (typically to 75-95 degrees F.). Liquid refrigerant
then passes through the filter dryer 138 which filters the liquid
for particulate and absorbs any water contained in the liquid. From
there, liquid refrigerant passes the sight glass "S" which allows
an observer (e.g. service person) to confirm the refrigerant is in
the liquid phase. Liquid refrigerant then passes through the
primary channel of the counterflow heat exchanger 142, which causes
it to cool further (typically to 40-75 degrees F.) due to heat
transfer with the secondary channel of the counterflow heat
exchanger. From there, liquid refrigerant passes through the
expansion valve 144, which acts as a restriction on the system.
After passing through the expansion valve, refrigerant is suddenly
at low pressure (typically 2-4 bar) and as a result drops in
temperature (to typically 25-35 degrees F.) and partially enters
the gaseous phase. Cold, low-pressure, liquid refrigerant then
enters the heat exchange plates 132. Heat is added to the
refrigerant from the following sources: from the thermal mass of
the plates, from saline passing through the cassette heat
exchanger, or from water passing through the liquid channels within
the cold plates, all of which cause the refrigerant to mostly or
entirely enter the gas phase. From the heat exchange plates 132,
low-pressure refrigerant flows into the secondary channel of the
counterflow heat exchanger where it transfers heat from the
refrigerant contained in the primary channel, causing it to warm
(to typically 35 to 70 degrees F.). Refrigerant at this point may
be mostly or entirely in the gas phase, and then enters the
compressor 140, thus completing the circuit. A secondary
operational state exists for the cooling engine, where the HGBP
valve 136 is open. In this state, hot, gaseous refrigerant exits
the compressor and directly enters the heat exchange plates,
causing them to warm up rapidly. This secondary state is used when
it is desirable to slow down the cooling provided to the patient,
or to warm the patient, without turning off the compressor.
Alternatively, the compressor can be shut off, however use of the
HGBP valve 136 has the advantage of being able to be opened and
closed rapidly and repeatedly as necessary to maintain the desired
heat exchange plate temperature. One embodiment of a pump 70 (e.g.,
a peristaltic pump) and associated assembly is shown in FIGS. 19
through 23. The pump 70 comprises a rotor assembly 160 and cover
161 connected to a drive motor 170 which causes the rotor assembly
to rotate. The rotor assembly includes guide rollers 164a and 164b,
and drive rollers 166a and 166b. As the rotor assembly rotates,
during pump operation, the drive rollers apply pressure to the pump
tubing (not shown), which is positioned in the pump raceway,
thereby causing thermal exchange fluid to move through the pump
tubing. The pump raceway is designed with a low height (i.e. as
measured along the axes of the rollers) in order to allow the pump
to be smaller, lighter weight, and lower cost. However with this
low height it is critical to keep the pump tubing aligned with the
raceway, in order to avoid jamming of the tubing within the pump
assembly (leading to wear of the pump and wear or rupture of the
tubing), and to avoid the tubing partially or entirely coming out
of contact with the drive rollers and thereby not generating some
or all of the pressure needed to pump heat exchange fluid through
the catheter. As seen in FIG. 20A, each guide roller 164a, 164b has
a tapered (e.g., barrel shaped) side wall 165. The guide roller may
include a central section which is not tapered (i.e. parallel to
the axis of rotation) 167. The tapered or barrel shape of the guide
roller facilitates self-centering of the pump tubing on the guide
roller, to ensure that the pump continues to perform as intended.
Because the tubing is being stretched over the guide rollers, a
normal force is generated, which in turn creates a frictional
force. The taper on the rollers is at a shallow angle (e.g., of a
range of 5 to 25 degrees) so that the frictional force is
sufficient to prevent the tubing from sliding on the roller
surface. Given that the tubing does not slide, the taper or barrel
shape puts a higher tensile load on the pump tubing at the center
of the roller (i.e. at the widest part of the barrel or roller),
and a lower tensile load on the pump tubing at either the top or
bottom edges of the roller (i.e. the narrowest part of the barrel
or roller). This difference in tensile forces leads to the
self-centering effect by developing a net force acting on the
tubing along the axis of the roller, in the direction of the center
of the roller. A front portion of the pump 70 is mounted on a front
plate 172. Optical sensors 174, for detecting when a cassette 64
and its cassette housing 62 are in place and properly positioned
for operation, may also be located on the front plate 172. Hooks
176a, 176b extend through slots in the front plate 172. These hooks
176a, 176b are positionable in retracted positions which allow
installation of the cassette 64 and insertion of the pump tubing 65
in the pump raceway 162. Thereafter, these hooks 176a and 176b are
movable to advanced positions wherein they exert a force on the
cassette housing 62 at two separate points of contact thereby
deterring unwanted movement of the cassette 64, cassette housing 62
or attached pump tubing 65, and securing the cassette in position
for system operation. Also mounted on the front plate 172 are level
sensors for sensing fluid levels within a reservoir formed within
the cassette housing 62. The pump 70 is alternately disposable in
an operative configuration (FIG. 22) and a loading configuration
(FIG. 23). Translational motor 180 causes the hooks to move between
a retracted and advanced position, and causes the pump to move
between an operative and loading configuration or positon.
[0088] Priming of the system, when the cassette 64 is positioned in
the cassette receiving space 66 between thermal exchange plates 80,
may be performed quickly by using one or more pump direction
changes. The pump 70 may be switched back and forth between running
in reverse and running in a forward direction for various durations
of time, at various speeds. The first pump reversal creates a
vacuum and the subsequent reversals help remove bubbles from the
system/line.
[0089] To purge the thermal exchange fluid from the system the pump
70 may be run in reverse. In one example, the pump 70 may be run in
reverse at 60% of max pump speed for about 20 seconds, during which
the return line or vessel outlet line is closed to prevent the
cassette vessel/bag from refilling with thermal exchange fluid or
saline when the pump is reversed or opened. A check valve may be
utilized, which may be positioned in the cassette housing, e.g., in
the vessel outlet tubing, between the tubing and the reservoir, to
prevent the vessel/bag from refilling with thermal exchange fluid
or saline when the pump is reversed or open. For example, in some
embodiments, the check valve may be integrated into the inflow
connector 206 seen in FIG. 28 to prevent fluid from back-flowing
into the vessel/bag 63 when the pump is reversed or open.
[0090] FIGS. 24 through 28 show further details of the
tubing/cassette/sensor module assembly 60 or cassette assembly. The
cassette housing 62 is attached to a frame 69 which supports the
side edges of the expandable vessel or bag 63. In certain
embodiments, the vessel or bag may include one or more sides having
a thickness suitable to prevent tears during use or manufacture.
For example, the thickness may be 0.001 inches-0.005 inches. In
certain embodiments the thickness may be about 0.002 inches. A
lower edge 63a of the expandable vessel or bag is sealed and may
include a support. As seen in FIG. 28, the cassette housing (bottom
cover removed) 62 encloses a reservoir 207, pressure sensor 202,
outflow connector 204 which is connected to the pulse-damping
outflow conduit 30, inflow connector 206 which is connected to
return or inflow conduit 32. During system operation, thermal
exchange fluid returns from the catheter, flowing through inflow
conduit 32, through inflow connector 206, through vessel inlet
tubing, into the expandable vessel or bag 63, through the
expandable vessel or bag 63 from one side to the other as indicated
by arrows on FIG. 28, exchanging heat with refrigerant flowing
through the thermal exchange plates, then out of the vessel through
vessel outlet tubing, into reservoir 207, through pump tubing 65,
through outflow connector 204, through pulse-damping outflow
conduit 30 and back to the catheter. Refrigerant flows through the
refrigerant flow channels in the thermal exchange plates in a first
direction, while thermal exchange fluid flows though the expandable
vessel in a second direction that is substantially opposite the
first direction. This counter flow of refrigerant and thermal
exchange fluid helps maximize heat exchange between the two
fluids.
[0091] To minimize the force required to insert or remove the Heat
Exchange (Hx) Bag or vessel from the Cold Plates, several methods
are described below.
[0092] The frictional force between the Cold Plates and the Hx Bag
may be reduced by adding coating to the surface of the Cold Plates
that lowers its coefficient of friction. Possible coatings include
Teflon or similar. The surface of the Cold Plates may be polished.
A coating may be added to the surface of the Hx Bag that lowers its
coefficient of friction, e.g., materials that may be used include
silicone, or similar (these can be brushed, sprayed, dipped,
etc.)
[0093] In some embodiments, a layer (release layer or antifriction
layer) of material may be placed over the outside surface of the Hx
Bag which lowers its coefficient of friction. Possible materials
include paralyene, HDPE (Triton), ePTFE, PTFE, FEP or similar. A
low friction sheet made of these materials may be used. In certain
embodiments, a fluoropolymer may be placed on the cold plates and
use a urethane HX bag with HDPE release layer on the bag. The HX
bag may include an HDPE release layer on each side of the bag with
each layer and the urethane bag affixed to the cassette frame h
pegs or clamps. Alternatively, a single longer piece of HDPE
release layer may be folded around the HX bag and then the hag and
release layers are affixed to the cassette frame with pegs or
clamps
[0094] The pulse-damping outflow conduit 30 functions not only as a
conduit through which the thermal exchange fluid flows but also a
pulse damper for damping pulses in the thermal exchange fluid as it
flows through the outflow conduit, to a catheter. Pulses may arise
due to the nature of the pump used for the thermal exchange fluid.
For example, in the case of a peristaltic pump with two drive
rollers, at certain times both drive rollers are in contact with
the pump tubing, and at other times only one drive rollers is in
contact with the pump tubing, depending on the angular position of
the pump rotor within the raceway. The thermal exchange fluid
system volume suddenly increases when a roller from the peristaltic
pump loses contact with the pump tubing as a normal part of the
pump's rotation. This happens because a section of the pump tubing
that had been flattened, and had zero cross-sectional area,
suddenly becomes round and contains a non-zero cross-sectional
area. The increase in system volume is approximately the
cross-sectional area of the tubing in its round state multiplied by
the length of tubing flattened by the roller. The pulse dampener
should have enough flexibility to contract suddenly and decrease
its volume by approximately this amount in order to dampen the
pulse. For example, the volume gained by the pump tubing when a
roller leaves contact with it may be 2 to 3 mL. Therefore it is
desirable for a pulse dampener to be able to decrease its volume by
this amount with a minimal change in system pressure. The pulse
damping conduit may comprise, for example, tubing that has
sufficient elastic or flexural properties to dampen, attenuate or
reduce the amplitude of pulses in the thermal exchange fluid as it
flows therethrough. For example, if the conduit is able to expand
by a volume of 20 to 30 mL under 60 psi of pressure, then it will
be able to contract by 2 to 3 mL when the pressure drops by
approximately 6 psi. The more compliant the conduit is, the smaller
the pressure drop that occurs when the tubing contracts, and
therefore the better the conduit performs its damping function.
While a highly compliant tubing is desirable, at the same time, the
conduit should have sufficient mechanical strength to expand and
contract by this amount repeatedly without rupture. For example if
a peristaltic pump has two driving rollers, turns at 40 RPM, and a
procedure lasts for 12 hours, the conduit must withstand 57,600
pulsation cycles. To balance these conflicting requirements, for
example, in certain embodiments, the length of the pulse damping
conduit may be about 90'' and could range between 20'' and 100''.
The conduit may be made of a low durometer polyurethane (Prothane
II 65-70A) and have a large ID at 0.25'' and could range between
0.15'' and 0.40''. The wall thickness of the conduit is about
0.094'' and could range between 0.06'' and 0.25''.
[0095] As seen in FIGS. 26 and 27 the cassette housing 62 is
connected to the frame 69 by a hinged connection 200. As packaged
prior to use, the hinged connection 200 is in a closed
configuration so that the housing 62 and accompanying pump tubing
65 are folded over the cassette's flexible vessel or bag 63 in the
manner seen in FIG. 27. At the time of use, the hinged connection
is moved to an open configuration causing the housing 62 and
accompanying pump tubing 65 to extend at a substantially right
angle relative to the expandable vessel or bag 63, as seen in FIG.
26. The hinged connection 200 locks in such open position so that
the cassette 64 cannot be returned to the folded configuration seen
in FIG. 27 without removing, disrupting or altering the hinged
connection 200. For example, the hinged connection may be unlocked
or disengaged by sliding a hinge protrusion forward or backward
within a hinge slot, thereby disengaging the lock.
[0096] Details of the sensor module 34 are shown in FIG. 29. The
sensor module comprises upper and lower housing portions 302a, 302b
which, in combination, form an enclosed housing. Within the housing
there is positioned an electronic storage medium 310 which holds
encoded information. Examples of the types of encoded information
that may be stored include but are not limited to; unique
identifier(s) for the changeable components (e.g., manufacturer
identification, part number, lot number, etc.), indications of
whether the changeable component(s) have previously been used
(e.g., an encoded indication of first use), indications of whether
the changeable component(s) is/are expired (e.g., encoded
expiration date), operational characteristic(s) of the changeable
component(s) (e.g., encoded indications of the size, type, volume,
etc. of the changeable component(s). In this non-limiting example,
the electronic storage medium comprises electrically erasable
programmable read-only memory (EEPROM). One example of how the
controller may check to determine whether the components had
previously been used is by checking the EEPROM or other data
storage medium 310 for a First-Use date. The First-Use date would
be "EMPTY" if this is the first time the changeable component
(e.g., the cassette assembly) has been connected to a console 14.
If the First-Use date is "EMPTY", the controller will write the
current date to the EEPROM's memory location where the First-Use
date will then be stored. Also, within the housing of the sensor
module 34, there are provided a first temperature sensor (e.g., a
thermistor) for sensing the temperature of thermal exchange fluid
flowing to the catheter 12 and a second temperature sensor 300b
(e.g., a second thermistor) for sensing the temperature of thermal
exchange fluid returning from the catheter 12. Signals from these
first and second temperature sensors 300a, 300b, as well as body
temperature signals from the connected body temperature sensor TS
and encoded data from the electronic storage medium 310, are
transmitted through temperature lead TL. A pressure lead PL, which
carries signals from a pressure sensor that senses the pressure of
thermal exchange fluid within the cassette tubing or console 14,
combines with the temperature lead TL, as shown, and the combined
leads are connected to the control console 14. In this manner, the
controller in the console main housing receives signals indicating
a) the encoded data from the electronic storage medium 310, b)
subject body temperature, c) thermal exchange fluid temperature
flowing to catheter, d) thermal exchange fluid temperature flowing
from catheter and e) thermal exchange fluid pressure. The
controller may be programmed to use the encoded information and/or
sensed temperatures and/or sensed pressure for control of the
system 10 and/or for computation/display of data. For example, the
controller may be programmed to use the difference between the
sensed temperature of thermal exchange fluid flowing to the
catheter and the sensed temperature of thermal exchange fluid
flowing from the catheter, along with the fluid flow rate or pump
speed, to calculate the Power at which the body heat exchanger is
operating or the power output of the heat exchanger. Power may be
calculated by the following equation: Such Power may be displayed
on the display or user interface 24.
Power (Watts)=(HE Fluid Temp OUT-HE Fluid Temp IN)Flow RateCP
[0097] wherein: [0098] HE Fluid Temp IN is the current measured
temperature of heat exchange fluid flowing into the heat exchanger
18; [0099] HE Fluid Temp OUT is the current measured temperature of
heat exchange fluid flowing out of the heat exchanger; [0100] Flow
Rate is the measured or calculated flow rate of heat exchange fluid
through the heat exchanger; and [0101] CP is the specific heat
capacity of the heat exchange fluid.
[0102] Also, the controller may be programmed to check and accept
the encoded information from the electronic storage medium 310
before allowing the system 10 to be used for warming or cooling the
body of the subject and/or to adjust operating variable or
parameters to suit operative characteristics (e.g., size, operating
volume, type) of the catheter 14, cassette 64, temperature probe,
tubing or other components. This pre-check of the encoded
information may occur in various sequences or processes. One
example of a process by which this pre-check may occur is by the
following steps: [0103] 1. User connects tubing/cassette/sensor
module assembly 60 to control console 14. [0104] 2. Console
controller detects this connection. Such detection of the
connection may occur by the controller scanning the temperature
sensor channels, which will open channels when no
tubing/cassette/sensor module assembly 60 is connected but will
become non-open when a tubing/cassette/sensor module assembly 60 is
connected. Alternatively, this could be done by the controller
polling the pressure sensor in the cassette 64 or the EEPROM in the
sensing module 34 for a response. [0105] 3. Controller establishes
a secure communication session with the EEPROM and reads its
content. The EEPROM's content may be encrypted such that it is
readable only by a processor having a secret key. In some
embodiments, the EEPROM itself may be encoded with a secret key
such that the controller may establish a secure session in
connection with the sensing module 34. [0106] 4. In some
embodiments, the EEPROM content may comprise the following
information, some or all of which must be checked and
verified/accepted by the controller before priming and operation of
the system 10 may occur: [0107] a. Manufacturer ID (factory
written) [0108] b. Cassette part #(factory written) [0109] c.
Shelf-life Expiration date (factory written) [0110] d. Lot
#(factory written) [0111] e. Expiration duration since first use
(factory written) [0112] f. First-Use date (written when the
cassette is first plugged into the console)
[0113] Referring to FIG. 38, in some embodiments, the system 10 may
be configured and programmed to alternately operate with more than
one type of heat exchange device. In such embodiments, the system
controller may be programmed to detect the particular type of heat
exchange device or component that has been connected to the system
and adjust the system's operation in accordance with the detected
type of heat exchange device or component, e.g.,
tubing/cassette/sensor module assembly 60 or cassette assembly,
and/or heat exchange device or component or body heat exchange
device or component, e.g., catheter 12 or a body surface heat
exchanger. For example, electronic storage medium 310 may include
information identifying a particular model or size of cassette
assembly 60 or heat exchange catheter 12 that is used in
combination with the cassette assembly 60. The system controller
may determine from that information the particular model and/or
size of cassette assembly or heat exchange catheter 12 being used.
The system user interface may be modified or altered depending on
the particular cassette assembly or catheter identified. The
controller may determine the number/location/type of patient
temperature sensors used with that particular cassette assembly 60
or catheter, select and actuate a control algorithm e.g.,
temperature control algorithm, that is appropriate for the detected
type and/or size of cassette assembly 60 or catheter 12 and set
limits or parameters, such as maximum pressure limits, suitable for
the detected type and/or size of cassette assembly 60 or catheter
12. The patient temperature sensors, e.g., patient temperature
sensors A or B in exemplary FIG. 38, may include patient blood
sensors, tissue sensors and/or deep tissue sensors, and such
sensors may be positioned on or through a catheter or in remote
location. Selection of the control algorithm may include selection
of any control algorithm described herein and/or selection of
whether the heat exchange rate is to be varied by a) altering the
temperature of thermal exchange fluid being circulated through the
catheter, altering the flow rate of thermal exchange fluid being
circulated through the catheter and/or altering both the
temperature and flow rate of thermal exchange fluid being
circulated through the catheter. In certain embodiments, the above
steps or actions may be performed for a body surface heat
exchanger, e.g., a pad, based on e.g., identifying information of
the pad and or associated cassette. Moreover, although the diagram
of FIG. 38 shows only two possible cassette assemblies and
catheters (i.e., Cassette Assembly A, Cassette Assembly B, Catheter
A or Catheter B), it is to be appreciated that the electronic
storage medium 310 may include information identifying any number
of cassette assemblies, catheters or other body heat exchange
devices, e.g., body surface heat exchangers or pads, that are
alternately useable with the system 10. For example, the electronic
storage medium 310 may include information identifying each of the
following cassette assemblies and/or catheters:
TABLE-US-00001 Catheter A The catheter 12 shown in FIG. 32 through
33C and described herein Catheter B Cool Line .RTM. Catheter (ZOLL
Circulation, Inc., San Jose, California) Catheter C Icy .RTM.
Catheter (ZOLL Circulation, Inc., San Jose, California) Catheter D
Quattro .RTM. Catheter (ZOLL Circulation, Inc., San Jose,
California) Catheter E Solex 7 .RTM. Catheter (ZOLL Circulation,
Inc., San Jose, California) Catheter F InnerCool .RTM. RTx Accutrol
Catheter (ZOLL Circulation, Inc., San Jose, California) Catheter G
InnerCool RTx Standard Catheter (ZOLL Circulation, Inc., San Jose,
California) Cassette Assembly A Cassette assembly associated with
Catheter A Cassette Assembly B Cassette assembly associated with
one or more of Catheters B-G
[0114] In some embodiments, a particular tubing/cassette/sensor
module assembly 60 (a "first" cassette assembly) may be useable or
approved for use with only one type of body heat exchanger. In such
embodiments, the sensing module 34 may be encoded with information
that is specific not only to the first cassette but which also
includes or causes the system controller to use algorithms and/or
operational settings/variables that are specific to the particular
body heat exchanger type, e.g., catheter type or body surface heat
exchanger (e.g., pad or garment) type that is useable or approved
for use with that first cassette assembly 60. In other embodiments,
an example of which is shown in FIG. 39, the first cassette
assembly 60 or another cassette assembly 60a (a "second" cassette
assembly) may be useable or approved for use with a plurality of
different types of body heat exchangers, such as heat exchange
catheters or body surface heat exchangers, e.g., heat exchanging
blankets, pads or garments. In such embodiments, the sensing module
34 may be encoded with information that is specific not only to the
cassette but which also includes or causes the system controller to
use algorithms and/or operational settings/variables that are
specific to the particular body heat exchanger, e.g., catheter type
or body surface heat exchanger (e.g., pad or garment) type that is
useable or approved for use with that cassette assembly. In the
particular non-limiting example shown in FIG. 39, the second
cassette assembly 60a is alternately connectable to and useable
with a plurality of different types of approved heat exchange
catheters 12a, 12b, 12c and 12d. In this particular example, the
first approved heat exchange catheter 12a shown in FIG. 39 is
commercially available as the Cool Line.RTM. Catheter (ZOLL
Circulation, Inc., San Jose, Calif.), the second approved heat
exchange catheter 12b is commercially available as the Solex 7.RTM.
Catheter (ZOLL Circulation, Inc., San Jose, Calif.), the third
approved heat exchange catheter 12c is commercially available as
the Icy.RTM. Catheter (ZOLL Circulation, Inc., San Jose, Calif.)
and the fourth approved heat exchange catheter 12d is commercially
available as the Quattro.RTM. Catheter (ZOLL Circulation, Inc., San
Jose, Calif.). Although these different types of catheters may have
different operating parameters (e.g., different maximum fluid
pressure ratings) they are all approved for use with cassette
assembly 60a and the sensing module 34 of cassette assembly 60a may
contain encoded information which includes, or which causes the
system controller to select and use, algorithms and/or operational
settings/parameters that are suitable for any of these heat
exchange catheters 12a-12d. Specifically, the encoded information
in the sensing module 34 may include the particular algorithms
and/or operational settings/parameters to be used, or alternatively
the system controller may be pre-programmed with a number of
different algorithms and/or operational settings/parameters and may
be further programmed to select and implement, on the basis of the
encoded cassette information, the algorithm and/or operational
settings/parameters suitable for the catheter or catheters that are
useable or approved for use with the inserted cassette assembly 60
or 60a. For example, in certain embodiments, each of the plurality
of approved body heat exchangers, e.g., catheters, may have a
recommended pressure limit and a cassette's encoded information may
include, or cause the controller to select and use, a control
algorithm, operational setting or parameter that limits the speed
of a pump such that heat exchange fluid pressure within the body
heat exchanger connected to the cassette will not exceed a maximum
pressure limit for that body heat exchanger, irrespective of which
of the plurality of body heat exchanger types is connected to the
cassette.
[0115] In other embodiments, the body heat exchanger, e.g.,
catheter or body surface heat exchanger such as pad or garment, may
contain encoded information which includes, or which causes the
system controller to select and use, algorithms and/or operational
settings/parameters suitable for the particular body heat
exchanger. Specifically, the encoded information in the body heat
exchanger may include the particular algorithms and/or operational
settings/parameters to be used, or alternatively the system
controller may be pre-programmed with a number of different
algorithms and/or operational settings/parameters and may be
further programmed to select and implement, on the basis of the
encoded body heat exchanger information, the algorithm and/or
operational settings/parameters suitable for the particular body
heat exchanger. Encoded information that is specific to a cassette
or body heat exchanger may also cause a change in the user display
of the console or system, which corresponds to the algorithms or
operational settings/parameters for the cassette or body heat
exchanger. FIG. 30 is a schematic diagram of the endovascular heat
exchange system 10. This schematic diagram shows major components
of the system 10, including the console 14, heat exchange catheter
12, thermal exchange engine 108, console head/user interface 24,
thermal exchange plates 80 and cassette 64. Additionally, this
schematic diagram includes other components and functional
indicators labeled according to the following legend:
TABLE-US-00002 FS FLOW, SALINE FW FLOW, WATER LS LEVEL, SALINE LW
LEVEL, WATER PSR PRESSURE SWITCH, REFRIGERANT PS PRESSURE, SALINE S
SWITCH TACH TECHOMETER TA TEMPERATURE, AIR TR TEMPERATURE,
REFRIGERANT TP TEMPERATURE, PLATE TS TEMPERATURE, SALINE TW
TEMPERATURE, WATER
[0116] To set up the system 10 a new tubing/cassette/sensor module
assembly 60 or cassette assembly is obtained and removed from its
packaging and the cassette 64 is unfolded to the opened and locked
configuration seen in FIG. 26. The access cover 42 of the control
console 14 is opened. An "open" button is pressed on the touch
screen user interface 24 causing the pump 70 to shift to its
loading configuration as seen in FIG. 23. The cassette frame 69 and
expandable vessel or bag 63 are inserted downwardly into the
cassette receiving space 66 until the housing 62 abuts front plate
172. The pump tubing 165 is inserted within the pump raceway 162.
The access cover 42 is then closed and a "close" button is
depressed on user interface 24 causing the pump 70 to shift to the
operative configuration (FIG. 22). The user then presses a "prime"
button on user interface 24 to prime the system with thermal
exchange fluid from a bag or other container that has been hung on
bracket 48 and connected to the system 10.
[0117] After the system has been primed, the catheter 12 is
connected and inserted into the subject's body and the system 10 is
operated to warm or cool the subject's body as desired.
[0118] FIG. 31 is a schematic diagram of an example of a heat
exchange system 10a capable of providing endovascular and/or body
surface heat exchange. The system includes all of the elements
described in the system 10 of FIG. 30 and, like FIG. 30, includes
labeling according to the legend set forth above.
[0119] Additionally, this system 10a includes a body surface heat
exchange fluid circuit 400 such that the system can provide body
surface heat exchange by circulating warmed or cooled heat exchange
fluid through at least one body surface heat exchanger 402 (e.g., a
heat exchange pad, blanket, garment, etc.) Such operation of the
body surface heat exchange fluid circuit 400 and body surface heat
exchanger 402 may be performed in addition to or instead of
endovascular heat exchange. The body surface heat exchange fluid
circuit includes a fluid reservoir, a pump, a bypass valve, a vent
valve, thermal exchange plates and a body surface heat exchange
device, e.g., a pad. A fluid, e.g., water, is added to the fluid
reservoir. When the bypass valve is closed to the vent valve and
open to the bypass line, fluid circulates from the pump, through
the body surface fluid chambers in the thermal exchange plates, the
reservoir, the bypass valve, and back into the pump. This allows
the volume of fluid within the system to come to thermal
equilibrium with the thermal exchange plates, which may be useful
in preparing the device to deliver temperature management treatment
to the patient. In normal operation, the bypass valve is open to
the vent valve and the vent valve is closed, and fluid circulates
from the pump, through the body surface fluid chambers in the
thermal exchange plates, through the reservoir, bypass valve, and
vent valve, to the body surface heat exchange device and then back
through the pump. To drain the body surface heat exchange device,
the vent valve is opened which allows air into the circuit and
prevents fluid from flowing from the bypass valve. This forces
fluid out of the body surface heat exchange device to the pump. The
pump is a positive displacement pump capable of pumping air or
liquid through the body surface fluid chambers in the thermal
exchange plates, to the reservoir. The reservoir is open to ambient
air (to allow excess air to escape the system if introduced by the
draining process or normal operation, or to accommodate changes in
fluid volume due to thermal expansion) and includes a fill port or
drain. The circuit also includes body surface heat exchange fluid
temperature sensors to provide feedback to the controller, and
fluid temperature sensors and fluid flow sensors for use in power
calculations.
[0120] In certain embodiments, one or more of the systems described
herein may also include one or more physiological alarms and/or
technical alarms. The physiological alarms may appear next to the
patient's temp on the display screen, and may occur when the
patient temperature exceeds the high or low patient temperature
alarm value. Technical alarms may appear elsewhere on the display
screen and may be triggered by console errors or other events,
e.g., probe or catheter disconnection, saline loop overpressure,
pump malfunction or open lid, and may be displayed by priority. Any
of the alarms may be audible. The system may also transmit data,
including patient and/or treatment data wirelessly, e.g., via Wifi,
Bluetooth or other wireless connection. Data may also be
transmitted via USB, Ethernet or wired connection. The system may
be electrically powered or battery powered.
[0121] The endovascular temperature management system 10 described
in various embodiments herein is a high powered system, capable of
rapidly cooling a patient.
[0122] In certain embodiments, the cassette/console is designed and
configured such that it is capable of delivering .ltoreq.4.degree.
C. working fluid or saline at a rate of .gtoreq.600 mL/min, at
steady state, when up to 700 W of heat is added to the working
fluid or saline loop (e.g., heat added by the subject's body).
[0123] In certain embodiments, the cassette/console is designed and
configured such that it is capable of delivering .ltoreq.4.degree.
C. working fluid or saline at a rate of 220+-20 mL/min, at steady
state, when .ltoreq.70 W of heat is added to the working fluid or
saline loop (e.g., heat added by the subject's body).
[0124] In certain embodiments, the cassette/console is designed and
configured such that it is capable of delivering .gtoreq.42.degree.
C. working fluid or saline at a rate of >400 mL/min, at steady
state, when up to 200 W of heat is removed from the working fluid
or saline loop.
[0125] In certain embodiments, the system (cassette, console, and
catheter) is designed and configured such that it is capable of
delivering greater than 400 Watts, or greater than or equal to 500
Watts, or greater than or equal to 600 Watts of cooling power,
e.g., with .ltoreq.4.degree. C. working fluid or saline at a
catheter pressure of about 60 PSI. In certain embodiments, the
system may deliver from 500 to 700 W or 600 to 700 W of cooling
power or about 675 W of cooling power or greater than 700 W of
cooling power.
[0126] In certain embodiments, the system (cassette, console, and
catheter) is designed and configured such that it is capable of
delivering > or equal to 50 W of warming power e.g., with
>37.degree. C. working fluid or saline at a catheter pressure of
about 40 PSI.
[0127] In certain embodiments, the system performance parameters
were verified during a bench test. The bench test included placing
a catheter (which is connected to a console/cassette assembly) in a
rigid 22 mm ID tube, which simulates the average IVC (inferior vena
cava) diameter, through which water at a temperature of 37 degrees
C. is flowing at a rate of 2.5 liters per minute (simulating blood
flow) over the catheter in a direction from the proximal end of the
catheter to the distal end of the catheter.
[0128] In certain embodiments, in maintenance and controlled rate
warming, the system may control a stable patient's temperature, as
measured by console, within about 0.3.degree. C. of target when
using a temperature sensor or probe on or in the catheter. During
normal use and in the case of a sudden saline loop blockage, the
system shall regulate and limit working fluid or saline pressure
for catheters as follows: <20 C: 60 psi nominal, 90 psi limit;
>=20 C: 40 psi nominal, 70 psi limit; or 40 psi nominal, 70 psi
limit. The console working fluid pump and cassette shall be capable
of an output up to 600 mL/min at 70 psi. Saline or working fluid
pressure at the outlet of the saline pump may be measured, e.g.,
over a range of 0-100 psi with an accuracy of .+-.5 psi over the
range 10-70 psi. The system may be used concurrently with a
defibrillator, electro surgical unit or other device or during an
MRI. The console and cassette together may be capable of delivering
<8.degree. C. saline, at a rate of 600 mL/min, within 5 minutes
of turning on the console, when starting with the system
equilibrated to ambient temperature. The console and cassette
together may be capable of changing the temperature from 4.degree.
C. to 40.degree. C. within 10 minutes.
Supplemental Warming by Hot Gas Bypass
[0129] With reference to FIG. 34, at least some embodiments of the
system 10 may include a hot gas bypass circuit and
controller/processor(s) programmed to cause hot refrigerant to
circulate from the refrigeration system of the cooling engine 108
through the thermal exchange plates 80 to assist the heaters 82
when conditions are deemed to indicate that such assistance of the
heaters 82 is appropriate. When the system 10 requires less cooling
than what the cooling engine provides when the compressor is at the
minimum speed, the heater(s) 82 are operative to warm the thermal
exchange plates 80. An indicator of the warming power output of the
heater(s) 82 is monitored. So long as the warming power expended by
the heater(s) 82 remains below a predetermined limit, the system 10
will continue to operate with only the heater(s) 82 warming the
thermal exchange plates 80. However, if the warming power output of
the heater(s) 82 exceeds a predetermined limit, the controller(s)
will cause hot refrigerant to circulate from the refrigeration
system of the cooling engine 108 through the hot gas bypass circuit
and through the thermal exchange plates 80, thereby assisting the
heaters 82 in warming the thermal exchange plates 80. The amount of
assistance the given to the heaters by the hot gas bypass circuit
is determined by the duty cycle of the hot gas bypass being open vs
being closed. When the monitored heater power falls below the
predetermined limit, the controller(s) may then incrementally or
progressively reduce the hot gas bypass valve duty cycle (BVDC) to
facilitate the correct amount of cooling or warming of the subject
body temperature to the target temperature without significant
overshoot of the target temperature.
[0130] To provide incremental or continuous change of the amount of
supplemental heating provided by the hot gas bypass, the controller
in some embodiments of the system 10 may be programed to vary duty
cycle of the hot gas bypass as the monitored power output of the
heater(s) 82 changes. For example, if the maximum heating power
output of the heater(s) 82 occurs at a heater duty cycle (HDC) of
30%, the predetermined limit may be set at an HDC of 15% (i.e., one
half of the maximum possible heater output). The hot gas bypass
circuit may be operative to deliver hot refrigerant to the thermal
exchange plates 80 on a hot gas bypass valve duty cycle (BVDC). For
example, at a BVDC of 50%, a bypass valve would open for a period
of 50 seconds to allow a 50 second flow of hot refrigerant to the
thermal exchange plates 80 and would then close for a period of 50
seconds to halt the flow of hot refrigerant to the thermal exchange
plates 80 for a subsequent period of 50 seconds, etc. Once the
monitored heater power has exceeded the 15% HDC predetermined
limit, the controller will trigger the bypass circuit to begin
delivering hot refrigerant to the thermal exchange plates 80. Once
the flow of hot refrigerant to the thermal exchange plates 80 has
commenced, the controller will cause the BVDC to increase as the
HDC increases above the 15% HDC predetermined limit and will cause
the BVDC to decrease as the HDC decreases below the 15% HDC
predetermined limit. There may be a maximum and minimum limit of
the BVDC, and the BVDC cannot exceed those limits (e.g., max of 90%
and min of 0%).
Combined Variation of Heat Exchange Fluid Flow Rate and Temperature
for Precision Maintenance of Target Body Temperature
[0131] In some embodiments of the system 10, the
controller/processor(s) may be programmed to vary not only the
temperature of the heat exchange fluid being circulated through the
heat exchange catheter 12, but also the rate and/or frequency of
such flow. One non-limiting example of this is shown in the flow
diagram of FIG. 35. In this example, after the subject has reached
the target temperature and the system 10 is operating to maintain
the body temperature at or within a permissible variance range of
the target temperature, the system 10 holds the temperature of the
heat exchange fluid constant and varies the speed of the pump 70 to
adjust the flow rate of heat exchange fluid through the catheter 12
as needed to maintain the body temperature. The controller monitors
the pump speed. If the pump speed exceeds a predetermined limit,
the controller will then cause warming or cooling of the thermal
exchange plates 80 to adjust the temperature of the heat exchange
fluid as needed to reduce the pump speed to the predetermined
limit. This allows for optimal combination of flow rate and
temperature adjustment during the maintenance phase of a treatment
session. It is to be understood that this applies only so long as
the system is continuing to cool or continuing to warm in order to
maintain the body temperature. If it becomes necessary for the
system to switch from cooling to warming or from warming to
cooling, the controller will adjust the temperature of the heat
exchange fluid irrespective of whether the pump speed has exceeded
the limit.
[0132] For example, after the system 10 has cooled a subject to a
target body temperature of 32 degrees C., the subject's body may
tend to rewarm. Thus, the system will operate in cooling mode to
maintain the target body temperature against the body's inherent
tendency to rewarm. In doing so, the system will maintain a
constant temperature of heat exchange fluid and will vary the speed
of the pump 70 as needed to maintain the target body temperature.
However, if it becomes necessary for the pump 70 to run at a speed
that exceeds a predetermined limit, the controller will cause the
cooling engine 108 to reduce the temperature of the heat exchange
fluid by an amount which will allow the pump to slow to a
predetermined limit while still maintaining the target body
temperature.
Pressure Feedback
[0133] As described, the heat exchange catheter system 10 may
incorporate pressure sensor(s) for sensing the pressure of the
circulating heat exchange fluid. During a given treatment session,
over-pressurization events can occur. This is when the saline
pressure is above the saline pressure predetermined limit. Such
over-pressurization events are typically of a transient nature and
result from temporary compression or bending of the catheter 12 or
associated tubing, or other causes. During a given treatment
session, under-pressurization events can also occur. Such
under-pressurization events occur when the Saline Pump Maximum Set
Point (SPM_set) is reached, meaning the saline pump is not allowed
to move any faster, but the saline pressure is below the saline
pressure predetermined limit. When an over-pressurization or
under-pressurization event of significant magnitude occurs, it may
be desirable to adjust SPM_set. However, it is preferable not to
abruptly change or overly reduce/increase the pump speed.
Additionally, after a transient over-pressurization or
under-pressurization event has past, it is desirable to return the
speed of the pump 70 to optimal operating speeds to maintain normal
pressurization of the circulating heat exchange fluid.
[0134] FIG. 36 is a flow diagram illustrating the SPM_set
adjustment protocol that some embodiments of the system 10 may be
programmed to perform. The system 10 is equipped to sense the
temperature of the heat exchange fluid, and the heat exchange fluid
is classified as "cold" or "hot". In this non-limiting example, the
predetermined limit for "cold" heat exchange fluid is set at 60
pounds per square inch (psi) and the predetermined limit for "hot"
heat exchange fluid is set at 40 psi. The SPM_set will only be
adjusted if the saline pressure is above the predetermined limit or
the saline pump set point is equal to SPM_set. The controller will
cause the SPM_set to decrease if the saline pressure is above the
pressure predetermined limit, and will cause the SPM_set to
increase as the saline pressure is below the pressure predetermined
limit. There may be a maximum and minimum limit of the SPM_set, and
the SPM_set cannot exceed those limits (e.g., max of 100% and min
of 10%).
[0135] Optionally, the controller/processor(s) may also be
programmed to store the most recent SPM_set for "cold" and "hot"
heat exchange fluids. Thus, when the saline temperature threshold
is crossed, the system 10 will switch from "cold" mode to "hot"
mode, or vice versa, and upon doing so may recall and apply the
recently calculated SPM_set setting for that temperature. In this
example, the SPM_set adjustment protocol repeats every three
seconds, however other intervals could alternatively be used.
Control of Body Cooling or Warming to Prevent Overshoot
[0136] In some situations, when warming or cooling a subject's body
to a target temperature, it may be desirable to control such
cooling or warming in a manner that substantially prevents or
avoids overshooting the target patient temperature. For example, in
embodiments of the system 10 which allow a user to select a
"maximum" rate of warming or cooling, the system controller may be
programed to follow a multi-phase warming or cooling protocol,
examples of which are shown in FIGS. 40 and 41. FIG. 40 is a graph
of patient temperature versus time during a body warming process
using a body heat exchange system as described herein. FIG. 41 is a
flow diagram showing steps in one embodiment of a body warming
process using a body heat exchange system as described herein. As
shown in FIG. 41, a user initially inputs a Patient Temperature Set
Point and a Warm/Cool Rate Set Point. If the user inputs a Patient
Temperature Set Point greater than 37.8 degrees C. (e.g., 38.0
degrees C.) and a Warm/Cool Rate Set Point of greater than 0.1
degrees C. per hour (e.g., 0.5 degrees C. per hour or max), the
system controller will cause the system 10 to effect the rewarming
in three phases, as follows:
[0137] Phase 1--In phase 1 the system controller initially causes
the system 10 to circulate heat exchange fluid through a body heat
exchanger, such as a heat exchange catheter 12 or body surface heat
exchanger (pad or garment), using a maximum pump speed and maximum
heat exchange fluid temperature (e.g., the maximum safe temperature
and flow rate for warming). The actual patient temperature is
received by the controller. During phase 1, the heat exchange fluid
temperature and/or pump speed may be periodically recalculated and
adjusted based on feedback of the sensed patient temperature, as
needed, to cause the sensed actual body or patient temperature to
increase from the current temperature to a predetermined interim
temperature. During phase 1, the controller may incrementally
adjust the control patient temperature set point over time, e.g.,
from 32 degrees C. to 37.8 degrees C., at the user defined rate,
e.g., at 0.5 degrees C. per hour. The pump speed and heat exchange
fluid temperature used during phase 1 causes the sensed actual body
or patient temperature to increase until it reaches a predetermined
interim temperature, which is lower than the user-input patient
temperature set point or user-input target patient temperature. In
this non-limiting example the interim temperature is 37.8 degrees
C. If the rate is chosen to be max, the rate at which the actual
patient temperature changes during phase 1 may not necessarily be
linear or constant as seen in the graph of FIG. 40. Rather, the
actual rate of change of the subject's body temperature during
phase 1 may, in some cases, vary due to physiological,
pharmacological and/or environmental factors (e.g. patient
sweating, changes in heart or respiration rate, dosing or changing
infusion rate of certain drugs, changes in room temperature,
changes in amount of clothing, blankets, or other warming deices,
etc.). In certain embodiments, during the first phase, the heat
exchange fluid may circulate through the body heat exchanger at a
substantially constant temperature and flow rate/pump speed.
[0138] Phase 2--as shown in FIG. 41, when the sensed patient
temperature reaches 37.8 degrees C. (i.e., the interim temperature)
the controller will cause the system to begin phase 2 of the
warming process. In phase 2, the system controller causes the
system 10 to circulate heat exchange fluid through the body heat
exchanger so as to further warm the subject's body at one or more
rate(s). The overall rate of warming during phase 2 is slower than
the overall rate of warming during phase 1. During phase 2, the
heat exchange fluid temperature and/or pump speed may be
periodically recalculated and adjusted based on feedback of the
sensed patient temperature, as needed, to cause the sensed actual
body or patient temperature to increase from the interim
temperature to the user-input patient temperature set point of 38
degrees C., without overshooting or exceeding such target patient
temperature. During phase 2, the controller may incrementally
adjust the control patient temperature set point over time, e.g.,
from 37.8 degrees C. to the user-input patient temperature set
point of 38 degrees C., at a slower rate than in phase 1, e.g. at
0.1 degrees C. per hour. Because the system controller monitors the
sensed actual body or patient temperature and makes periodic (e.g,
every minute) adjustments to the heat exchange fluid temperature
and/or pump speed or flow rate during phase 2, such rate is
precisely controlled and overshoot of the 38.0 degrees C.
user-input patient temperature set point is avoided. The controller
may be programmed to incrementally reduce the phase 2 warming rate
as the actual body or patient temperature gets closer to the
user-input patient temperature set point.
[0139] Phase 3--As shown in FIG. 41, when the sensed patient
temperature reaches the user-input patient temperature set point of
38.0 degrees C., the controller will cause the system to proceed
with phase 3 of the warming process to maintain the target patient
temperature. In phase 3, the system controller continues to receive
the actual sensed patient temperature and periodically (e.g., every
minute) adjusts the heat exchange fluid temperature and/or pump
speed, as needed, to maintain the sensed actual patient temperature
substantially equal to the user-input patient temperature set point
until such time as the user enters a "stop" command. As an
alternative to a "stop" command, in some embodiments, the user may
input a time period for phase 3 maintenance of the user-input
patient temperature set point and the system may automatically stop
the flow of heat exchange fluid through the body heat exchanger at
the end of such user-input time period.
[0140] In cases where the system 10 is being used to warm a
subject's body, an overall warming rate of 0.01 degrees C. per hour
to 0.2 degrees C. per hour may be used during phase 2. For example,
a warming rate of 0.05 degrees C. per hour to 0.1 degrees C. per
hour may be used during phase 2. In cases where the system 10 is
being used to cool a subject's body, an overall cooling rate of
0.05 degrees C. per hour to 1.0 degrees C. per hour may be used
during phase 2.
[0141] In some embodiments, during warming, if the user-input
patient temperature set point is greater than 37.8 the controller
may be programmed to actually cause the heat exchange fluid to stop
flowing through the body heat exchanger when the sensed actual body
or patient temperature reaches 37.8 degrees C., irrespective of the
user-input patient temperature set point.
[0142] In certain embodiments, an additional feature to ensure the
patient temperature does not exceed 38.0 degrees C. may be
provided. If the actual patient temperature is higher than 38.0
degrees C. and the saline temperature is determined to be higher
than 38.0 degrees C., the saline pump will turn off. This prevents
warming of the patient when the actual patient temperature is above
38.0 degrees C.
Hypothermic Treatment to Deter Reperfusion Injury
[0143] FIG. 26 shows one example of a clinical protocol that may be
used to effect rapid hypothermia to deter reperfusion injury in a
subject suffering from an ischemic event that may be treated in a
manner that causes reperfusion or restoration of blood flow to the
ischemic tissue. Non-limiting examples of such reperfusion
procedures include angioplasty, stenting, atherectomy, embolectomy,
thrombectomy, insertion of a perfusion wire or other conduit to
carry blood or oxygenated fluid through or past an obstruction,
administration or a thrombolytic agent (e.g., streptokinase or
tissue plasminogen activator), some types of surgical
revascularization, etc. While reperfusion treatments may restore a
flow of blood or other oxygenated fluid to the ischemic tissue,
they can also result in significant reperfusion injury which
contributes to the amount of tissue that is ultimately infarcted or
caused to become necrotic due to the ischemic event. Reperfusion
injury is thought to occur in stages. Initially, the ischemia
causes increased permeability of capillaries and arterioles. When
reperfusion is accomplished, the renewed pressure within those
damaged capillaries and arterioles results in diffusion and
filtration of fluid into the adjacent tissue. This causes chemical
imbalances within the tissue that give rise to an inflammatory
response. These events and possibly others result in
post-reperfusion damage to the tissue that may be permanent.
[0144] As explained herein, the above-described heat exchange
catheter system 10 has the unique ability to cool an adult human
subject's body to a hypothermic temperature below 34 degrees C.,
and preferably between 32 degrees C. and 34 degrees C., in
approximately 20 minutes. This rapid induction of hypothermia
allows caregivers to select an appropriate time to perform the
reperfusion procedure after the subjects body temperature has been
lowered to the target temperature. Prior studies have indicated
that if hypothermia below 35 degrees C. is effected prior to
reperfusion, the severity of reperfusion injury, and hence the size
or severity of any permanent tissue infarction, is reduced.
Applicant has performed a pilot study using the above-described
protocol for deterrence of reperfusion injury in human subjects
presenting at hospital emergency departments suffering from acute
ST elevation myocardial infarction (STEW). In this pilot study,
subjects were randomized into hypothermia and non-hypothermia
(control) groups. Subjects in the hypothermia group received
standard anti-shivering medication and a heat exchange catheter was
placed in the inferior vena cava (IVC). A high power heat exchange
catheter system was then used to rapidly cool the body of each
subject in the hypothermia group to a temperature below 34 degrees
C. within <90 minutes of the subject's arrival in the emergency
department. Each subject then underwent percutaneous coronary
Intervention (PCI) resulting in reperfusion of the ischemic
myocardium. The subjects in the hypothermia group had a body
temperatures at the time of reperfusion (i.e., measured at PCI wire
crossing) of 33.6+1.0 degrees C.
[0145] Following completion of the reperfusion procedure,
hypothermia was maintained in each hypothermia group subject for a
period of three hours at a target temperature setting of 32 degrees
C. Thereafter, the hypothermia group subjects were gradually
rewarmed to a body temperature of 36 degrees C.
[0146] Four to six days after the event, each subject underwent
cardiac magnetic resonance imaging (cMR) and infarct size divided
by left ventricular mass (IS/LVM) was determined. On average,
subjects in the hypothermia group had a 7.1% absolute change in
IS/LVM and approximately a 30% relative reduction compared to the
non-hypothermia controls. A 5% absolute change in IS/LVM is
generally viewed as a good clinical outcome.
[0147] The results of this pilot study, when compared with
previously reported data, suggests that 1) cooling of the subject's
body temperature at a faster rate (i.e., made possible by using a
high cooling power system) results in reduced infarct size measured
as IS/LVM, 2) There appears to be a dose-response relationship
whereby lower body temperature at the time of reperfusion
correlates with greater protection against reperfusion injury and,
thus, smaller infarct size.
[0148] Accordingly, a method for reducing reperfusion injury in a
human or animal subject who undergoes a reperfusion procedure
following an ischemic event (e.g., myocardial infarction, acute
coronary syndrome, stroke, infarction or ischemia of any metabolic
tissue or organ including but not limited to heart, lung, kidney,
liver and brain) is provided. In this method, the heat exchange
catheter 12 is inserted into the subject's vasculature and the
system 10 is used to lower a body temperature of the subject to a
temperature below 34 degrees C. and preferably between 32 degrees
C. and 34 degrees C. prior to reperfusion. The above described
techniques for estimating body temperature at a target location may
be utilized in this method and the target location may be in or
near the organ or tissue where the ischemia is occurring. For
example, in a subject suffering from an evolving myocardial
infarction of myocardial ischemia, the system 10 may operate to
lower the estimated cardiac temperature (LV Temperature) to the
hypothermic temperature. Thereafter, caregivers may perform a
reperfusion procedure at a selected time after the body temperature
has been cooled to the target hypothermic temperature, thereby
deterring reperfusion injury and/or reducing the amount of tissue
that ultimately becomes infarcted or necrotic.
[0149] Although the invention has been described hereabove with
reference to certain examples or embodiments of the invention,
various additions, deletions, alterations and modifications may be
made to those described examples and embodiments without departing
from the intended spirit and scope of the invention. For example,
any elements, steps, members, components, compositions, reactants,
parts or portions of one embodiment or example may be incorporated
into or used with another embodiment or example, unless otherwise
specified or unless doing so would render that embodiment or
example unsuitable for its intended use. Also, where the steps of a
method or process have been described or listed in a particular
order, the order of such steps may be changed unless otherwise
specified or unless doing so would render the method or process
unsuitable for its intended purpose. Additionally, the elements,
steps, members, components, compositions, reactants, parts or
portions of any invention or example described herein may
optionally exist or be utilized in the absence or substantial
absence of any other element, step, member, component, composition,
reactant, part or portion unless otherwise noted. All reasonable
additions, deletions, modifications and alterations are to be
considered equivalents of the described examples and embodiments
and are to be included within the scope of the following
claims.
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