Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PORTABLE PATIENT TEMPERATURE ADJUSTMENT
APPARATUS AND METHOD
TECHNICAL FIELD
The present specification relates to a device for adjusting the core body
temperature of a patient. More specifically, portable devices and methods for
adjusting the core body temperature of a patient are disclosed.
BACKGROUND
The application of pressure and/or thermal energy is often used to treat
various
medical conditions.
For example, the combined application of pressure and temperature is taught
in U.S. Patent No. 5,074,285 for the treatment of sporting injuries such as
bruising
and muscle stiffness. In that system, thermal sources, which could be hot or
cold, are
introduced into pockets close to the wearer's skin and pressure is applied to
a series of
air pockets arranged along the limb that are designed to apply a pressure-
gradient
repeatedly to the limb.
Hypothermia is a condition resulting from a drop in body temperature and
varies in degree according to the amount of undercooling. Many methods for
treating
hypothermia are already known. Generally, these comprise introducing heat into
the
core of the body by some means to raise the body temperature. Simple
treatments can
take the form of a warm drink. Sometimes warm air is blown around the body via
air
blankets.
One of the first physiological responses of hypothermia is peripheral
vasoconstriction which reduces the amount of blood at the periphery of the
body.
This can make it difficult to introduce heat into the body through the
application of
heat to the body surface. It is known that vessels, including capillaries,
arterioles,
arteries, venules and veins, can be made to vasodilate under conditions of
negative
pressure. Vasodilated skin regions, particularly on the forearm, can make
efficient
heat transfer surfaces.
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One system that applies negative pressure to a limb to reduce peripheral
vasoconstriction whilst warming the periphery of the patient to treat
hypothermia is
taught in U.S. Patent No. 5,683,438 and sold under the mark Thermostat by
Aquarius Medical Corp. In that system, a limb of the patient is placed in a
sealed
chamber and the pressure inside the chamber is reduced to a negative pressure
of
between -20 to -80 mmHg (-2.7 to -10.7 kPa). At the same time, thermal energy
is
delivered to the surface the limb using a thermal blanket, heat lamp or
chemical
heating elements. Further developments to this system are described in
International
Publication No. WO 01/80790 Al.
Recently, the application of a pulsating negative pressure has been found
beneficial in the adjustment of a patient's core body temperature. Commonly
owned
U.S. Patent Application Publication No. 2005/0027218 describes a system for
applying a pulsating pressure and adjusting the core body temperature of a
patient
which utilizes a liquid reservoir to effectuate heat and pressure transfer to
a limb of
the patient. Such application is herein incorporated in its entirety.
SUMMARY
Embodiments of the invention provide devices and methods for the in situ or
in transit adjustment of the core body temperature of a patient. Devices
according to
some embodiments include a control unit and pressure chamber adapted to apply
a
pulsating negative pressure to a limb of the patient. An adjustment
temperature
applied during the application of the pulsating pressure can heat or cool the
patient as
necessary.
In a first aspect, the invention features a portable device for in situ or in
transit
adjustment of a core body temperature of a patient. The device includes a
thermal
transfer sleeve, a pressure chamber, and a control unit. The thermal transfer
sleeve
may be adapted to receive a limb of the patient. The pressure chamber may
include a
substantially rigid casing for receiving the limb and thermal transfer sleeve,
and a heat
transfer element for applying an adjustment temperature within the casing. The
control unit may be connectable to the pressure chamber and adapted, when
connected to the pressure chamber, to alternatingly introduce and release a
negative
pressure within the pressure chamber. Components of the device, including the
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thermal transfer sleeve, pressure chamber, and control unit may be configured
to fit
within a carrying case such that the portable device and the carrying case can
be
manually carried by an individual.
According to another aspect, in some devices, the thermal transfer sleeve may
be adapted to receive a limb of the patient and to be wetted such that the
thermal
transfer sleeve is in contact with the surface of the limb and air between the
thermal
transfer sleeve and the limb is minimized. In such case, when the limb and
thermal
transfer sleeve are inserted into the pressure chamber substantially all of
any liquid
within the pressure chamber may be carried by the thermal transfer sleeve.
According to another aspect of the invention, the portable device for in situ
or
in transit adjustment of a patient's core body temperature includes a portable
pressure
chamber, thermal transfer means, temperature adjustment means, and pressure
application means. The thermal transfer means may be adapted for receiving the
limb
of the patient, facilitating insertion of the limb into the portable pressure
chamber,
and, when inserted into the portable pressure chamber with the limb, carrying
substantially all of any liquid within the portable pressure chamber. The
temperature
adjustment means may be adapted for applying an adjustment temperature to the
thermal transfer means and thereby to the limb when the thermal transfer means
and
the limb are inserted into the portable pressure chamber. And the pressure
application
means may be adapted to alternatingly introduce a negative pressure within the
portable pressure chamber and release the negative pressure from the portable
pressure chamber.
In another aspect, a method for in situ or in transit adjustment of a
patient's
core body temperature is provided. The method can include installing an
absorbent
sleeve the patient's limb. The sleeve may be wetted with a liquid. The limb
having
the wetted sleeve installed thereon, may be inserted into a pressure chamber
such that
the limb is substantially sealed from external conditions and substantially
all liquid in
the interior of the pressure chamber is carried by the sleeve. A
heating/cooling
element within the pressure chamber may be activated to selectively heat or
cool the
limb. And, a negative pressure may be alternatingly introduced to and released
from
the pressure chamber.
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Methods according to some aspects of the invention can be carried out to
effectuate the in situ or in transit adjustment the core body temperature of
an
unconscious patient. In such cases, the methods can include the additional
steps of
installing the thermal transfer sleeve about a limb of the unconscious
patient, and
preparing the limb for insertion into the pressure chamber.
In addition, methods according to some aspects of the invention can include
the step of manually carrying a portable device in a carrying case to the
patient. Such
methods can further include removing the portable device from the carrying
case, and
checking that the control unit is in fluid connection with the pressure
chamber and if
not, connecting the control unit with the pressure chamber.
In some embodiments, devices and methods disclosed herein may provide for
efficient heating and/or cooling of a patient. Devices and methods may further
provide for the application of pulsating pressure to the limb of a patient.
Some
embodiments may provide such functionality in a portable device that can be
manually carried by an individual. In some embodiments, the temperature
adjustment
devices and methods may be usable in situ or in transit. Such devices and
methods
may provide for use under environmental conditions. For example, some devices
may
provide for closed-system operation. Devices and methods may be used without
the
need for a reservoir of liquid or liquid supply system.
Related technology is disclosed in commonly owned U.S. patent application
nos. 12/335,852 and 12/335,918, both filed on December 16, 2008 and titled
Portable
Patient Temperature Adjustment Apparatus and Method, the entirety of both of
which
is hereby incorporated by reference herein.
BRIEF DESCRIPTION OF THE DRAWINGS
The following drawings are illustrative of particular embodiments of the
invention
and therefore do not limit the scope of the invention. The drawings are not to
scale
(unless so stated) and are intended for use in conjunction with the
explanations in the
following detailed description. Embodiments of the invention will hereinafter
be
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described in conjunction with the appended drawings, wherein like numerals
denote
like elements.
Figure 1 is a perspective view of a device according to one embodiment.
Figure 2 is a top plan view of a device including a carrying case according to
some
embodiments.
Figure 3 is a cross-sectional view of an embodiment installed about a limb of
a
patient.
Figure 4 is a side plan view of a pressure chamber according to some
embodiments.
Figure 5A is a top plan view of a casing according to some embodiments.
Figure 5B is a side plan view of the casing of Figure 5A.
Figure 5C is a side plan view of an expandable casing according to some
embodiments, the casing having been expanded.
Figure 6 is a top plan view of a heat transfer element according to some
embodiments.
Figure 7 is a perspective view of a thermal transfer sleeve according to some
embodiments.
Figure 8 is a schematic diagram of a control device according to some
embodiments.
Figure 9 is a perspective view of a control unit according to some
embodiments.
Figure 1 OA is a perspective view of a component compartment of a control unit
according to some embodiments.
Figure I OB is a side sectional representation of the component compartment of
Figure
I OA.
Figure 11 is a perspective view of a power supply compartment of a control
unit
according to some embodiments.
Figures 12A - 12D show a schematic representation of the operation of the
device
according to some embodiments.
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Figure 13 shows a plot of applied pressure v. time representative of the
operation of
devices and methods according to some embodiments.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The following detailed description is exemplary in nature and is not intended
to limit the scope, applicability, or configuration of the invention in any
way. Rather,
the following description provides practical illustrations for implementing
exemplary
embodiments of the present invention. Examples of constructions, materials,
dimensions, and manufacturing processes are provided for selected elements,
and all
other elements employ that which is known to those of skill in the field of
the
invention. Those skilled in the art will recognize that many of the examples
provided
have suitable alternatives that can be utilized.
Figure 1 shows a portable device 100 for adjusting the core body temperature
of a patient according to some embodiments. Devices according to embodiments
of
the invention adjust the patient's core body temperature through the
application of an
adjustment temperature while applying a pulsating pressure to the patient's
limb. The
portable device 100 includes a control unit 105 connected to a pressure
chamber 110
via connector 115. The device 100 further includes a thermal transfer sleeve
120
adapted to be installed about a limb of the patient. The pressure chamber 110
is
adapted to receive the patient's limb having the thermal transfer sleeve 120
installed
thereon. An adjustment temperature can be applied by temperature adjustment
means
within the pressure chamber 110 to cause heat transfer to or from the limb
through the
thermal transfer sleeve 120. Contemporaneously, the control unit 105 can apply
a
pulsating pressure within the pressure chamber 110 via connector 115 to
increase
blood flow within the limb. Due to the increased blood flow at the point of
application of adjustment temperature, the core body temperature of the
patient can be
effectively adjusted.
Potential uses for the devices and methods described herein take advantage of
the improved heating and cooling capabilities provided by the increased blood
flow.
For example, devices and methods according to some embodiments can be used in
connection with any of the important clinical problems listed below:
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= Prevention of hypothermia by heat transfer to the body (heat gain)
= Treatment of hypothermia by heat transfer to the body (heat gain)
= Prevention of hyperthermia by heat transfer from the body (heat loss)
= Treatment of hyperthermia by heat transfer from the body (heat loss)
To induce hypothermia to treat stroke patients, heart attack and other
ischemic
diseases, for neurosurgery etc.
= To induce hyperthermia to treat cancer patients globally and locally
= Changing the pharmacological distribution of drugs systemically and locally
because of locally changed blood flow and possibly diffusion
Increasing the distribution of contrast fluid to a local part of the body
= Increasing venous circulation
= Increasing lymphatic circulation
= Promoting healing of tissues by increased blood flow
= Increasing antigen-antibody contact through increased blood flow, lymphatic
flow and diffusion
= Increased flow of substances between vessels and cells through increased
diffusion
= Reducing fever in patients with neurological injury
= Preheating of skin and increase in blood circulation to ease insertion of
needles (veneflon) in subcutaneous veins
= Increasing blood circulation in ischemic limb
= Delivering antibiotics to ischemic limb
= Reducing oedema in ischemic limb
Moreover, devices according to some embodiments can be especially useful
due to their portability. More specifically, rather than requiring a patient
needing
temperature adjustment to be first moved to a controlled environment, portable
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temperature adjustment systems and methods such as those described herein
allow for
the adjustment of the patient's core body temperature where the patient is
located (in
situ) or as the patient is being transported (in transit). In many situations,
timing is
critical and the quicker the patients core body temperature can be adjusted,
the more
likely a positive result for the patient. For example, using devices and
methods of the
present invention, an unconscious, hypothermic patient can be warmed in the
location
where the patient is found, rather than delaying treatment until after the
patient has
been transported. Thus, embodiments of the device can be especially useful in
connection with, for example, search and rescue, military, or emergency
medicine
endeavors.
Various features of embodiments of the present invention render the devices
disclosed herein particularly effective for in situ or in transit temperature
adjustment.
Primarily, the dimensions of the device provide for portability. As shown in
Figure 2
devices according to the present invention are configured to fit within a
carrying case
200 such that the portable device and the carrying case are configured to be
manually
carried by an individual. For example, the carrying case and device can be
hand-
carried or carried over the shoulder. A carrying case 200 can generally
comprise a
bag, or rigid case formed to receive the component parts of the device 100. In
this
view, the carrying case 200 has been opened to reveal various compartments of
the
case. This particular embodiment includes four compartments: a first
compartment
205 configured to receive the control unit 105, a second compartment 210
configured
to receive the pressure chamber 110 and connector 115, a third compartment 215
configured to receive a power supply/adapter 225, and a fourth compartment 220
for
holding additional items, for example, pre-wet thermal transfer sleeves, a
container of
liquid, or medical supplies. Moreover, a carrying case can include additional
features
to facilitate portability such as, for example, a power outlet. A carrying
case
including an external power adapter can provide for charging or pre-warming of
the
device while it is still located within the carrying case. For example, a case
can
include an AC adapter which can be plugged into a standard electrical outlet,
or a
charger adapted for use with a DC power source such as a 12 V DC vehicle power
socket. Of course, one can appreciate that many other cases can be used to
carry
devices according to the present invention and the specific example shown here
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should not be construed to limit the invention. Further, in some embodiments
various
components can be sized such that they are configured to fit within other
components
of the device. For example, the control unit can be sized so as to fit within
the
pressure chamber. In addition the carrying case 200 may include one or more
straps,
a handle, or other features to facilitate manual carrying.
With reference to Figure 1, devices according to some embodiments can be
used by first installing the thermal transfer sleeve 120 and pressure chamber
110
about the limb of a patient. To do so, patient's limb is first inserted into
the thermal
transfer sleeve 120. Then, the limb having the thermal transfer sleeve
installed
thereon, is inserted into the pressure chamber 110. Installation of some
embodiments
including additional steps and features will be discussed in greater detail
below.
Figure 3 shows a cross-section of a patient's limb 300 having a portion of a
device 100 according to some embodiments of the invention installed thereon.
From
the surface of the limb 300 outward, the device 100 includes thermal transfer
sleeve
120 and pressure chamber 110. Pressure chamber 110 generally comprises a
substantially rigid casing 125 having a heat transfer element 130 installed
therein.
Further, some embodiments include an outer shell 135 about an outer surface of
the
casing 125. The pressure chamber 110 is formed to receive the patient's limb
300
within an interior cavity 305 of the chamber. The casing 125 provides the
shape of
the pressure chamber and generally defines the interior cavity 305. In
addition, the
casing 125 should be sized to accommodate the heat transfer element 130 within
the
interior cavity 305. When installed, the pressure chamber 110 provides a
substantially
fixed volume about the limb 300 having the thermal transfer sleeve 120
installed
thereon such that a negative pressure can be generated, preferably within
sleeve-
chamber gap 305, and the adjustment temperature can be applied within the
chamber.
In some embodiments, the limb-sleeve gap 310 is small such that air between
the
thermal transfer sleeve 120 and limb 300 is minimized. Preferably the thermal
transfer sleeve 120 is in skin-tight contact with the limb 300. In some
embodiments, a
constant or intermittent negative pressure is applied within the limb-sleeve
gap to
evacuate potential air within this gap and to maximize skin-sleeve contact. In
such
case, the sleeve can include an airtight outer surface. In contrast, sleeve-
chamber gap
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305 is generally larger than the limb-sleeve gap 310. This is because, in some
embodiments, negative pressure is applied within the sleeve-chamber gap 305
and a
larger gap is necessary to facilitate air removal from within the gap.
The limb 300 can be any part of a human or animal body that can be easily
introduced into the device. For example, a limb can comprise an arm or leg, a
portion
of an arm or leg (e.g. forearm, hand, lower leg, or foot), or more than one of
such
parts of the body. In certain situations it may be preferable to use more than
one
device to increase the amount of heat transfer. For transferring thermal
energy to or
from the patient, generally the greater the surface area of skin contacted by
the
thermal transfer sleeve 120 and heat transfer element 130 of the pressure
chamber
110, the better. In addition, some areas of skin are generally more efficient
at
transferring thermal energy from or to the patient's blood, and hence the core
of the
patient. Some embodiments are preferably installed on the patient's forearm
because
it provides a large, efficient surface area for heat transfer. Moreover, in
comparison
with the leg, there is generally less reflex constriction in the forearm,
leading to
improved thermal energy transfer. Where maximum heat transfer is required, the
device should be large enough to accommodate the whole arm or at least as far
up the
upper arm as possible, e.g., the middle of the upper arm. Engaging the
patient's arm
above the elbow can maximize the surface area of skin in contact with the
thermal
transfer sleeve and can also provide for a longer period of blood flow in the
distended
venous plexus in close proximity to the thermal transfer sleeve. In this way
therefore,
the volume of blood subject to heat transfer from the heat transfer element of
the
pressure chamber can be maximized. Moreover, engaging the limb as far up the
limb
as possible reduces the area of the limb exposed to the external conditions,
thus
reducing environmental effects which could counter the patient temperature
adjustment. In particular, the area of the limb which includes veins nearest
the skin
can be covered.
Another problem addressed by engaging a large portion of the limb is the
counter-current effect present in many mammals. The counter-current effect is
a
mechanism wherein arteries delivering blood flow to a patient's limb run
alongside
veins delivering blood from the limb. Heat transfer between the arteries and
veins
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causes the temperature of blood flow within the associated vessels to
equilibrate.
Thus, venous blood flow is heated or cooled by arterial blood flow, which is
at or
nearer to the patient's core body temperature, prior to returning to the
patient's core.
Where the venous blood flow has been temperature adjusted, e.g. by the devices
described herein, the heat transfer from the arterial blood flow counteracts
the desired
effect of the temperature adjustment by drawing the venous blood flow closer
to the
(undesired) core body temperature. Embodiments of the invention can address
this
counter-current effect by applying the adjustment temperature to a region of
the limb
where the counter-current effect is taking place, thus mitigating the heat
loss or gain
of the venous blood flow due to arterial heat transfer.
However, in the interest of maintaining portability of the device, the
pressure
chamber and thermal transfer sleeve may be sized so as to accommodate a
smaller
portion of the limb. For example, a smaller device, in which the proximal end
of the
pressure chamber engages the arm at or slightly below the elbow around the
patient's
forearm or biceps and triceps can be easier to install about a patient,
especially in situ
or in transit.
Figure 4 shows a perspective view of a pressure chamber 110 according to
some embodiments. The pressure chamber 110 can comprise any shape capable of
receiving the limb, but it is preferably tubular and of circular or oval cross-
section.
Cylindrical chambers provide a rounded surface well suited to withstand
negative
pressures and which generally conforms to limbs. Here, the pressure chamber
110
comprises an elongate cylinder having a curved side wall 405 and an end wall
410. In
some embodiments, the pressure chamber includes additional anatomical features
to
generally conform to the limb. Anatomical features can decrease the interior
chamber
volume, which in turn minimizes the volume of air which must be displaced from
the
chamber to provide the negative pressure. Thus, a smaller pump can be utilized
with
such embodiments. In addition, the provision of such features can reduce the
size of
the pressure chamber, thus making the device easier to transport. The
embodiment of
Figure 4 includes anatomical features to generally conform to an arm.
Additionally,
the pressure chamber 110 includes a connection 415 located within the end wall
410
for connecting the pressure chamber 110 to a control unit. While the
connection 415
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can be located generally anywhere on the device, positioning the connection
415 in
the end wall 410 can allow for easy access no matter the situation in which
the
portable device is utilized.
The pressure chamber 110 of Figure 4 further comprises an outer shell 420
fitted about an exterior surface of the casing. In some embodiments, the outer
shell -
420 can comprise a substantially elastic material, such as, e.g. Neoprene. An
elastic
outer shell can be used to bias an expandable casing closed, yet stretch to
allow for
expansion of the casing to facilitate insertion or removal of the limb.
Moreover, an
outer shell can act as an insulation layer about the pressure chamber to
insulate the
chamber interior from external conditions. Such an insulation layer can be
especially
important given the portability of some embodiments. Because the portable
device
can be used for in situ or in transit temperature adjustment, the user will
often need to
use the device where environmental conditions would counteract the operation
of the
device, e.g. warming a patient in a cold environment. An insulation layer can
inhibit
negative environmental thermal effects and thus improve performance of the
temperature adjustment system.
Figure 5A shows a casing 125 according to some embodiments. The casing
provides the structure for the pressure chamber and defines the interior
cavity. Casing
125 comprises an elongate rigid tube having a distal end wall 505 and an open
proximal end 510. A patient's limb can be inserted in through the opening in
the
proximal end 510. In the embodiment of Figure 5A, the casing 125 is
anatomically
formed to substantially conform with an arm. The casing 125 includes a wrist
portion
515 between wider forearm and hand portions 520, 525. Ideally, the anatomical
features of the device are perfectly dimensioned for the limb of the patient,
however
such practice is impractical given the variety of sizes of patients. Thus, in
some
embodiments, the anatomical features are provided based upon general
population
biometrics. In some embodiments, a system for use in the military can comprise
a
casing formed according to military biometrics so as to fit 95% of U.S.
soldiers.
Figures 5A and 5B include exemplary dimensions formed according to such
statistics.
Further, in some embodiments, the casing 125 is expandable. An expandable
casing can facilitate installation of the casing about the patient's limb.
Installation of
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a pressure chamber including some anatomical features, for example the wrist
portion
515 of Figure 5A, can be difficult because the patient must maneuver his or
her limb
or a portion thereof to get past the feature. Moreover, proper installation of
a pressure
chamber about the limb of an unconscious or injured patient can be hindered
due to
the patient's inability to maneuver his or her limb past the anatomical
features. With
an expandable casing, many of these problems can be overcome. In some
embodiments, an expandable casing comprises a casing having a hinged edge 530
and
opposed openable edge 535. Figure 5B shows a side view of the casing 125 of
Figure
5A along the openable edge 535. The casing can be expanded by pivoting the top
half
540 of the casing relative to the bottom half 545 of the casing about hinge
550 on the
opposite edge of the casing, causing the casing to split along fissure 555. As
the
casing 125 splits, the cross-sectional dimension of the casing expands,
facilitating
insertion of the limb. A side plan view of an expanded casing 125' is shown in
Figure
5C. In this view, the top and bottom halves 540,545 of the casing have been
separated along fissure 555 by pivoting about hinge 550. Alignment members 560
are
shown extending between the top and bottom halves 540, 545 so as to maintain
alignment of the halves 540, 545. Alignment members 560 can be rigid
protrusions
extending from the top or bottom half 540, 545 of the casing into receiving
members
on the opposite half. When the casing 125' is expanded, such as in Figure 5C
or
during installation or removal of a limb, alignment members 560 prevent
misalignment of the casing. Of course, one of ordinary skill in the art can
appreciate
that there are many additional ways to maintain proper alignment, all of which
should
be considered as within the scope of this invention.
In some embodiments, to further facilitate portability of the device, the
casing
may be capable of being disassembled, e.g. it may break in half, for example
along a
fissure around the entire casing. Each separate piece or half of the can then
be easily
stowed within a carrying case while taking up minimal space. In use, each
separate
piece of such a casing can be removed from the carrying case and fitted
together to
form the casing. Other components of the pressure chamber, e.g. heat transfer
element and outer shell, can then be installed within or about the assembled
casing.
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Referring back to Figure 3, pressure chambers 110 according to some
embodiments further comprise a heat transfer element 130 adapted to facilitate
heat
transfer within the pressure chamber 110 so as to apply an adjustment
temperature to
the limb 300, via the thermal transfer sleeve 120. Embodiments of the device
can be
used for warming, cooling, or both warming and cooling of a patient's core
body
temperature. When the device is used to warm a patient, the heat transfer
element
facilitates heat transfer to the limb and the adjustment temperature can be
said to be a
warming temperature. When the device is used to cool a patient, the heat
transfer
element facilitates heat transfer from the limb and the adjustment temperature
can be
said to be a cooling temperature. In either case, heat transfer effectuated by
the heat
transfer element occurs via the thermal transfer sleeve. The locally applied
heat
affects the circulation locally. Cool adjustment temperatures can constrict
vessels
locally, while warm adjustment temperatures tend to dilate vessels. This can
sometimes work to the disadvantage of the patient.
Devices according to some embodiments can be adapted to provide a
warming, a cooling, or both a warming and a cooling adjustment temperature. In
some embodiments, a user of the device can tune the adjustment temperature to
any
desired level within an operating range. Conversely, in some embodiments, the
adjustment temperature is restricted to a preset value or one of a few
selected
predetermined values. A warming adjustment temperature should be selected so
as to
be at or above the current core body temperature of the patient. Generally,
the
selected warming temperature is at or above the normal physiologic temperature
of
the patient. Of course, in some applications, the applied warming temperature
will be
below the normal physiologic temperature of the patient. In cooling
applications, the
cooling temperature is generally selected to be at or below the normal
physiologic
temperature of the patient, however, in some applications, the applied cooling
temperature will be above the normal physiologic temperature of the patient.
In
embodiments capable of providing a warming temperature, the device should be
configured so as to be capable of applying a temperature of at least about
37.0 degrees
Celsius ( C). Preferably, the warming temperature will be in the range of 37.0
C to
43.0 C (e.g. 42.5 C) at the patient's skin. In embodiments capable of
providing a
cooling temperature, the device should be configured so as to be capable of
applying a
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temperature of at least below about 24.0 C, and preferably below about 10.0
C.
Preferably, where the cooling temperature will be applied to a patient's limb
without
regional anesthesia, the cooling temperature will be in the range of 22.0 C
to 23.0 C
(e.g. 22.5 C) at the patient's skin. Where the cooling temperature will be
applied to
the patient's limb with regional anesthesia, the cooling temperature can be in
the
range of 4.0 C to 10.0 C (preferably about 10.0 C).
Figure 6 shows an embodiment of a heat transfer element 130 according to
some embodiments. The heat transfer element 130 comprises a tube-like mitten
605
having an open proximal end 610 and a distal end 615 which, in some
embodiments,
is closed. The mitten 605 can be installed inside the casing of the pressure
chamber
such that it lines the interior cavity of the chamber. The exemplary heat
transfer
element 130 shown is shaped to conform with a casing including anatomical
features
for use with an arm such as that of Figure 5A. In this view, the heat transfer
element
130 has been removed from the pressure chamber. The term "mitten" as used
herein
should not limit the heat transfer element to embodiments wherein the limb is
an arm
or hand, rather the term "mitten" should be broadly construed to designate a
lining
that generally conforms with the casing in which it is installed. Mitten 605
can be
rigid, or flexible and can comprise any suitable material. Because the mitten
often
comes into contact with the limb of the patient and can line the interior of
the
substantially rigid casing, in some embodiments the mitten comprises a soft or
cushioned material, such as, e.g. Neoprene.
Heat transfer element 130 further comprises thermoelectric devices 620
installed within or along a surface of the mitten. The thermoelectric devices
620 are
adapted to thermally communicate with the limb via the thermal transfer sleeve
when
the limb and thermal transfer sleeve are received in the pressure chamber.
Thermoelectric devices 620 can comprise any such device capable of
effectuating
heat transfer under an applied electrical current or potential. The
thermoelectric
devices can be heating devices, cooling devices, devices capable of both
heating and
cooling, or a combination of heating and cooling devices. For example, the
thermoelectric devices can comprise Peltier devices, resistive heating
elements, or
cooling fans. In some embodiments, the heat transfer element 130 can be
constructed
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of a material that is itself a resistive heating material, for example, a mesh
of resistive
threads. Electrical wires 625 connect the thermoelectric devices 620 to
thermal
control circuitry which is adapted to control the operation of the
thermoelectric
devices 620. In some embodiments, the thermal control circuitry includes a
controller
located within the control unit and connected to electrical wires 625 via
connector
115. Thermoelectric devices can be located at any location within or about the
mitten.
In the embodiment of Figure 6, the thermoelectric devices are regularly
dispersed
about the entire surface of the mitten. However, in some embodiments,
thermoelectric devices are positioned irregularly or located so as to create
independent heating/cooling zones within the mitten.
The embodiment of Figure 6 further includes a temperature sensor 630.
Temperature sensor 630 can provide feedback to the thermal control circuitry
or
temperature control unit so that the desired adjustment temperature within the
pressure chamber can be maintained. Some embodiments may include multiple
temperature sensors each keyed to independent heating/cooling zones within the
pressure chamber so that each zone can be separately controlled. In addition,
some
embodiments can include additional temperature sensors or the capability to
communicate with additional temperatures sensors. For example, some
embodiments
can include an external or ambient temperature sensor for sensing an ambient
temperature and adjusting the applied or available adjustment temperatures
based on
this reading. Further, some embodiments can include a thermometer or
connection to
a thermometer which can be separately connected to or used with the patient to
provide feedback in the form of a current core body temperature of the
patient.
In some embodiments, the pressure chamber further comprises a seal element
adapted to seal the pressure chamber about the limb when the limb is received
by the
pressure chamber. Seal element should provide a substantially air tight seal
about the
limb so that the negative pressure can be introduced to the pressure chamber
and can
be applied throughout the negative pressure period. A seal element according
to
embodiments of the portable device need not perfectly seal the chamber, rather
the
emphasis of the feature should be on ease of installation about the patient.
In some
embodiments, the seal element comprises a cuff made of a stretchable,
resilient
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material. Alternatively, the seal element can comprise an inflatable cuff
which
inflates to engage the limb. An exemplary cuff 425 is shown in Figure 4. Here,
the
cuff 425 is attached to the pressure chamber 110 about the open proximal end
430 of
the device. Cuff 425 narrows to opening 435, through which the patient's limb
can be
inserted. When the limb is inserted, the stretchable material of the cuff 425
expands
at the opening 435 to accommodate the limb and maintain a seal about the outer
surface of the limb. As seen in Figure 4, a cuff 425 can be joined to outer
shell 420
and can comprise the same material as the outer shell or a different material.
Alternatively, as shown in Figure 6, cuff 425 can be connected to the heat
transfer
element 130. Likewise, the cuff can be connected or attachable to the thermal
transfer
sleeve. Of course many other seal element designs and connections can be used
and
should be understood to be within the scope of invention. For example, a cuff
extending from the heat transfer element can be connected with a cuff
extending from
the outer shell to form a single cuff connected to both layers.
In some embodiments, the pressure chamber 110 further includes an extension
feature. An extension feature can provide an extensible, semi-rigid portion of
the
pressure chamber so that the chamber can be extended to cover a larger portion
of the
limb, which can be desirable in some embodiments as described above. An
extension
feature can comprise, for example, an accordion feature having a plurality of
rigid
support members or a coiled rigid support member encased within or coupled to
a
flexible connection material. The support member maintains the sleeve-chamber
gap
of the device, and the flexible connection material maintains the seal of the
chamber.
In some embodiments, an extension feature is included between the open
proximal
end 430 and the seal element 425 of the pressure chamber 110 so that the
pressure
chamber 110 can be extended beyond and/or flex with a joint, e.g. an elbow or
knee,
of the limb. Extension features can be permanently connected to the pressure
chamber, or can be removably connected such that the feature can be used only
when
necessary.
Referring back to Figure 1, devices according to the present invention further
comprise a thermal transfer sleeve 120. Thermal transfer sleeve 120 is
installable
about the patient's limb and facilitates thermal energy transfer to or from
the limb.
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The incorporation of the thermal transfer sleeve further enables the
portability of
devices according to the present invention. In previously known devices, large
and
difficult to transport liquid management systems are often required to supply
and
regulate the liquid reservoir which the device uses as a heat and pressure
transfer
medium. In addition, the liquid reservoirs themselves are quite bulky and
heavy. As
such, devices of the prior art are not readily transportable by an individual.
In
contrast, embodiments of the present invention do not require or utilize a
free flowing
volume of liquid within the pressure chamber to effectuate heat and pressure
transfer
to the limb. Rather, embodiments utilize the thermal transfer sleeve and a
small, fixed
volume of liquid (or no liquid at all) to perform these functions.
Accordingly, by
eliminating the use of liquid reservoirs as heat and pressure transfer means,
portability
is enhanced.
Figure 7 shows a perspective view of a thermal transfer sleeve 120 according
to some embodiments. The thermal transfer sleeve 120 generally comprises a
cloth-
like, material formed to receive the patient's limb. In this embodiment, the
thermal
transfer sleeve 120 is formed to receive an arm. When installed, the thermal
transfer
sleeve should generally conform to the limb. For example, the thermal transfer
sleeve
can comprise a stretchable material that can stretch to engage the limb.
Moreover, the
thermal transfer sleeve can include coatings or layers to afford the sleeve
additional
properties, for example, a thermal transfer sleeve can include a coating or
surface that
is airtight, watertight, or both airtight and watertight. In some embodiments,
the
thermal transfer sleeve 120 comprises a wettable material capable of absorbing
and
storing a volume of thermally conductive liquid. In such embodiments, when the
limb and thermal transfer sleeve are inserted into the pressure chamber
substantially
all of any liquid within the pressure chamber can be carried by the thermal
transfer
sleeve. Alternative heat transfer materials, e.g. a thin metallic sheet or a
cloth
material bearing a thermally conductive coating, are also contemplated and
should be
construed as within the scope of the invention. Preferably, the thermal
transfer sleeve
comprises a high-absorbency, wettable material, e.g. synthetic chamois cloth.
Wettable materials may be preferred because when installed about a limb and
wetted,
such materials can adhere to the limb in skin-tight contact. Thus the surface
area of
the limb contacted by the thermal transfer sleeve is maximized, providing for
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increased and more uniform heat transfer through the wetted material. In
various
embodiments, the liquid used to saturate the thermal transfer sleeve is water,
however
other thermally conductive liquids can be used.
The embodiment of Figure 7 includes additional features which can facilitate
installation and adjustment of the sleeve 120 about a limb. Slit 705 extends
along a
portion of the sleeve 120 and allows for partial separation of the sleeve to
facilitate
installation of the thermal transfer sleeve 120 about the limb. Such a feature
can be
especially useful when the sleeve is being installed about the limb of an
unconscious
patient. Closing features 710 are provided to secure the sleeve together about
the slit
705. Closing features 710 can comprise any suitable connection means such as,
for
example, hook and loop, snap, adhesive, or another connector. In addition to
facilitating installation of the thermal transfer sleeve 120, closing features
710 and slit
705 can be used to adjust the sleeve once installed about the patient's limb.
For
example, once installed about the limb, opposing sides of the slit 705 can be
cinched
and closing features 710 reattached so that the sleeve 120 is in close contact
with the
limb and the limb-sleeve gap is reduced.
In some embodiments, the device can include a pre-wet sleeve. Pre-wet
sleeves are provided with the sleeve material already saturated with liquid.
By
providing the thermal transfer sleeve pre-wet, one or more installation steps
can be
eschewed. Moreover, the provision of such sleeves prevents the user from
having to
locate a source of liquid at installation. A pre-wet sleeve can comprise any
of the
thermal transfer sleeves discussed above, or it may be otherwise constituted.
The pre-
wet sleeve is typically provided in a liquid-impermeable package so that the
sleeve
remains wet until use. After use, the pre-wet sleeve may be discarded, or
retained for
future re-wetting and use. Additionally, in embodiments including a carrying
case, a
separate compartment for stowing one or more packages of pre-wet sleeves may
be
provided.
Referring back to Figure 1, devices according to embodiments of the invention
further comprise a control unit 105. The control unit 105 is connectable, e.g.
via
connector 115, to the pressure chamber 110 and adapted to deliver a pulsating
pressure to the pressure chamber 110. In addition, in some embodiments, the
control
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unit 105 regulates the adjustment temperature applied within the pressure
chamber
110.
To deliver the pulsating pressure, the control unit 105 can cause air to be
delivered to or removed from the pressure chamber. The term "air" used herein
as a
pressure regulating medium is in no way intended to limit the invention to
devices
that just use air. Other gases, for example, inert gases, would also be
suitable
although may add considerably to the cost of operation and the portability of
the
device. Moreover, unless otherwise noted, any reference to a pressure within
this
disclosure should be construed as the pressure relative to local atmospheric
pressure at
the time of use of the device. For example, the term "positive pressure"
references a
pressure greater than atmospheric pressure. In another example, a pressure of -
80
mmHg (-10.7 kPa) within the chamber would correspond with an absolute internal
pressure of 680 mmHg (90.7 kPa) based on an atmospheric pressure of 760 mmHg
(101.3 kPa). Moreover, any reference to "higher" or "greater" negative
pressures
should be understood to reference pressures that are more negative than
others, i.e. -
80 mmHg is a "higher" and a "greater" negative pressure than -60 mmHg.
Devices and methods according to the present invention operate on the
premise of the application of a pulsating pressure. A "pulsating pressure," as
used
herein, refers to the repeated, alternating introduction of two or more
different
pressures during consecutive time periods. In one example, a pulsating
pressure can
comprise the alternating introduction of an applied pressure and release of
the applied
pressure so as to return to approximately atmospheric pressure. The applied
pressure
can be either a positive pressure or a negative pressure. In embodiments using
a
negative pressure, the period during which the negative pressure is introduced
and is
present is referred to as the negative pressure period. Likewise, in systems
utilizing a
positive pressure, the period during which the positive pressure is introduced
and is
present is referred to as the positive pressure period. In each case, the
period during
which the applied pressure is released and atmospheric pressure is returned
and is
present is referred to as the atmospheric pressure period. Generally
embodiments
discussed herein are discussed with reference to a negative applied pressure.
In most
cases negative pressure systems can be readily substituted with positive
pressure
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systems by inverting pump and valve operations or by other adjustments
apparent to
one of ordinary skill in the art. Thus, one should appreciate that any
discussion of
negative pressure systems herein, unless otherwise indicated, likewise applies
to
positive pressure systems. In such case, the term "negative pressure" as used
herein
should be interchanged with the term "positive pressure" and pressure values
should
likewise be substituted. Accordingly, the invention should not be construed to
exclude devices and methods using a positive pressure rather than a negative
pressure.
In some embodiments, multiple, consecutive, alternating negative pressure
periods and atmospheric pressure periods are applied to a limb within a
pressure
chamber without removing the limb from the chamber. The negative and
atmospheric
pressure periods can be of the same or a different duration. In some
embodiments, the
negative pressure periods and atmospheric pressure periods can be selected
according
to known methods, such as those described in commonly owned U.S. Patent
Application Publication No. 2005/0027218 which is herein incorporated by
reference.
For example, in some embodiments the negative pressure period is between 1
second
and 20 seconds in duration and the atmospheric pressure period is between 2
seconds
and 15 seconds in duration. Further, in some embodiments, the negative
pressure
period is between 5 seconds and 15 seconds in duration and the atmospheric
pressure
period is between 5 seconds and 10 seconds in duration. And in some preferred
embodiments, the negative pressure period is approximately 10 seconds in
duration
and the atmospheric pressure period is approximately 7 seconds in duration.
The pressure applied within the pressure chamber can be fixed or selected at
the point of use. Embodiments of devices and methods according to the present
invention provide for the application of a negative pressure of -80 mmHg (-
10.7 kPa)
or less. Accordingly, corresponding pressure chambers are configured to
withstand
negative pressures of at least -80 mmHg (-10.7 kPa), and preferably
considerably
more. In some embodiments, the negative pressure can be -60 mmHg (-8.0 kPa) or
less. Some embodiments utilize a negative pressure of approximately -40 mmHg
(-5.3 kPa). The preferred negative pressures have been selected in order to
reduce
complications that can possibly arise from the application of higher negative
pressures. In some embodiments, a negative pressure has been selected to
encourage
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local vasodilation in the surface of the limb while minimizing the risk of
possible
complications. As described above, pulsating the negative pressure has been
found to
encourage blood flow and for this reason a pulsating negative pressure of 0 to
-40
mmHg (0 to -5.3 kPa) is preferably generated in the chamber.
Figure 8 is a schematic representation of a device 100 including control unit
105 according to some embodiments. Control unit 105 comprises a portable
housing
805 having a pump 810, valve 815, controller 820, and power supply 825
connected
thereto. The portable housing 805 further includes first and second chambers
830,
835 and a connector input 840 for providing fluid connection to the pressure
chamber
110 via connector 115. First and second chambers 830, 835 can be substantially
air
impermeable so as to prevent leakage of air into or out of each chamber. Pump
810
includes a pump inlet 811 in fluid connection with the second chamber 835 and
a
pump outlet 812 in fluid connection with the first chamber 830. Accordingly,
the
pump 810 is adapted to displace air from the second chamber 835 and deliver
the
displaced air to the first chamber 830. Valve 815 is adapted to alternatingly
connect
the connector input 840 (and therefore the pressure chamber 110) with the
first
chamber 830 and the second chamber 835. Controller 820 is connected with the
pump 810 and valve 815 to control the introduction and the release of the
negative
pressure to and from the pressure chamber 110. The controller 820 can
accomplish a
pulsating negative pressure within the pressure chamber 110 by setting the
valve 815
so that the connector input 840 is in communication with the second chamber
835 (a
low pressure source). Air from the (relatively high pressure) pressure chamber
is
drawn into the second chamber 835 through this connection. To restore the
pressure
chamber 110 to atmospheric pressure, the controller 820 can switch the valve
815
such that the first chamber 830 and pressure chamber are connected causing the
pressures to equilibrate at approximately atmospheric pressure. By repeatedly
switching the valve 815, negative pressure pulses can be applied within the
pressure
chamber 110.
In addition, the controller 820 can comprise the thermal control circuitry for
controlling the adjustment temperature within pressure chamber 110. In such
case,
the controller is provided a connection with the pressure chamber 110 via
connector
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input 840 and connector 115 or an additional connection to the pressure
chamber 110.
Power supply 825 is connected with the portable housing 805 and adapted to
supply
power to pump 810, valve 815, controller 820, and, in some embodiments, the
heat
transfer element within the pressure chamber 110. The power supply enhances
the
portability of the device 100, allowing for use of the device in remote
locations where
access to power is limited. Moreover, some embodiments include a power adapter
for
using the device when a power source is available, or for charging the
portable power
supply 825.
Connector 115 provides for the connection from the control unit 105 to the
pressure chamber 110. The connector 115 can comprise a length of tubing for
transferring air to or from the pressure chamber to apply a pulsating pressure
therewithin. Additionally, in some embodiments, the connector 115 can provide
for
an electrical connection from the control unit to the pressure chamber. The
electrical
connection can deliver power and/or control signals to or from electrical
components
within the pressure chamber. To provide such connection, electrically
conductive
wire can be molded into or attached to the tubing or be provided separately
from the
tubing. In some embodiments, the connector comprises a length of silicon
tubing
having an electrical lead helically coiled about the tubing and molded or
attached
thereto. Such a connector can provide a durable, rugged connection between the
pressure chamber and the control unit.
Figure 9 shows a control unit 105 according to some embodiments of the
invention. The control unit 105 comprises a portable housing 905 for
protecting and
holding the components of the control unit. The portable housing 905 can
comprise
any suitable shape and material, preferably a lightweight, robust material
such as
plastic or a composite material. In some embodiments the control unit 105 is
shaped
and dimensioned such that it can fit within the pressure chamber for stowing.
For
example, in some embodiments, the portable housing is generally cylindrical
and
approximately 50 cm in length (e.g. 51.1 cm) having an approximately 8.0 cm
outer
diameter. In addition, in some embodiments the portable housing 905 includes
grip
features 910, e.g. surface unevenness in designated areas, to provide a good
grip
when holding the device. Additionally, some embodiments can include brackets
or
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other mounting means for mounting the control unit near the patient, e.g. to a
stretcher.
In some embodiments, the portable housing 905 comprises a component
compartment 915 and a power supply compartment 920. Figures 1 OA and I OB show
views of a component compartment 915 according to some embodiments of the
invention. The component compartment comprises the housing 1005 defining a
housing cavity 1010 within which is mounted a pump 1015, internal chamber
1020,
valve 1025, printed circuit board 1030, and on/off switch 1035. The pump 1015,
valve 1025, and printed circuit board 1030 can be mounted upon a flat upper
surface
of the internal chamber 1020, which can then be slid into the housing 1005 on
rails
1040 which are fastened or molded to the inner wall of the housing 1005. In
addition,
the component compartment can include a lock mechanism 1045 for releasably
connecting with the power supply compartment.
The pump 1015 can comprise any suitable fluid pump capable of generating a
pressure up to at least -40 mmHg within the internal chamber 1020. More
preferably,
the pump 1015 is capable of generating negative pressures greater than -40
mmHg
(e.g. -80 mmHg). In some embodiments, the pump 1015 is configured to pump air
from the internal chamber 1020 into the housing cavity 1010. In such
embodiments,
the housing cavity 1010 and internal chamber 1020 correspond to the first and
second
chambers 830, 835, respectively, of the schematic of Figure 8. Referring again
to
Figures 1 OA and I OB, the operation of the pump 1015 can be controlled by a
controller located on the printed circuit board 1030. This controller can also
interface
with the pressure chamber and a temperature sensor therewithin to regulate
operation
of the pump 1015 and heat transfer element of the pressure chamber.
Valve 1025 is in fluid communication with the internal chamber 1020 and a
connector input 1050 connectable with a connector for connecting to a portable
pressure chamber. Valve 1025 can be controlled by the controller to connect
the
internal chamber 1020 with the pressure chamber during negative pressure
periods to
provide for the introduction of negative pressure to the pressure chamber. In
some
embodiments the valve 1025 may further be in fluid connection with the housing
cavity 1010. Such devices can be described as closed system devices because
when
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generating the negative pressure, the pump 1015 delivers the displaced air
from the
pressure chamber within the housing cavity 1010 and thus preserves the
temperature
of the air as modified while within the pressure chamber. During atmospheric
pressure periods, such embodiments connect the housing cavity with the
pressure
chamber to return to the pressure chamber the temperature adjusted air.
Component compartments 915 can further include additional features. For
example, in some embodiments, the device further includes a strain relief 1055
for
ensuring a proper and enduring connection between the control unit and the
connector. Further, the component compartment 915 can include one or more
escape
valves within an external wall of the housing for connecting one or more of
the
system chambers to the environment. Such an escape valve can be activated to
relieve excess pressure built up within the system during prolonged or normal
operation. For example, air leakage into the pressure chamber from the
environment
when the negative pressure is introduced may remain within the system causing
pressure within the pressure chamber (in a closed system) to build up. The
escape
valve can be triggered by the controller or manually to relieve this excess
air.
Additionally, in some embodiments, an escape valve can be opened to draw
additional
environmental air into the system to allow for a more rapid return to
atmospheric
pressure.
An embodiment of a power supply compartment 920 can be seen in Figure 11.
Such a compartment is generally a hollow tube for receiving a power supply or
storage device. In some embodiments, the power supply is one or more
batteries.
The batteries can be rechargeable or disposable, and in some embodiments
comprises
one or more ANR26650M1 cells available from A123 Systems. Embodiments
including rechargeable batteries can further include a charging contact 1105
mounted
within the housing of the power supply compartment 920. Additionally, some
embodiments may include a fuse 1110 to prevent overcharging of the device. To
connect with the component compartment 915, the power supply compartment 920
can include a lock mechanism 1115 which can engage a paired lock mechanism
1045
on the component compartment to lock the two compartments together.
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Various embodiments include features for facilitating the transition between
pressure periods. For example, the transition from the negative pressure
period to the
atmospheric pressure period can be accomplished by allowing air to be drawn
into the
pressure chamber. For example, in some embodiments, the pressure chamber can
include an external valve to the environment openable to release the negative
pressure
(i.e. cause air flow from the relatively higher pressure, atmospheric pressure
source to
the pressure chamber). Preferably, however, a separate chamber within the
control
unit or pressure chamber is designated an atmospheric pressure source, thus
allowing
the device to operate as a closed system device. Most preferably, the device
includes
a positive pressure chamber, e.g. the first chamber 1210 of the control unit
in Figures
12A - 12D discussed below, which maintains a pressure greater than atmospheric
pressure (i.e. a positive pressure) during the negative pressure period. Thus,
upon
transition from the negative pressure period to the atmospheric pressure
period, fluid
transfer into the pressure chamber occurs more rapidly due to a greater
pressure
differential between the positive pressure source and the pressure chamber.
Because of the length of the atmospheric pressure period or the rate at which
air can re-enter the pressure chamber, the chamber may not be returned
completely to
atmospheric pressure between the pulses of negative pressure. In such case, a
small
amount of negative pressure may remain in the pressure chamber at the end each
pulse, i.e. the pressure chamber is returned only to approximately atmospheric
pressure. This might be, say, between 0 and -20 mmHg (0 and -2.7 kPa) or more
preferably between 0 and -10 mmHg (0 and -1.3 kPa), and more preferably still
between 0 and -5 mmHg (0 and -0.67 kPa). Most preferably, the rate at which
air can
re-enter the pressure chamber and the pulse period are such that the pressure
within
the chamber is returned to atmospheric pressure during each atmospheric
pressure
period. Indeed, in the most preferred embodiments, the change in the chamber
pressure occurs rapidly such that the time taken to change the pressure is
only a small
fraction of the atmospheric pressure period, for example, less than 50%,
preferably
less than 25% and more preferably less than 10% of the atmospheric pressure
period.
It is most preferred that the plot of pressure against time follows a
substantially
square-wave plot with sharp transitions at the pressure changes i.e. the
change in the
chamber pressure is substantially instantaneous. In practice, some rounding of
the
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transitions may occur. Similarly, the control unit should have sufficient
capacity to
bring the pressure chamber to the desired negative or positive pressure as
quickly as
possible. In preferred embodiments, the control unit pre-generates the
negative
pressure prior to the negative pressure period (e.g. during a preceding
atmospheric
pressure period), so that the transition to the negative pressure period can
likewise
approach a square wave.
Figure 13 shows a plot of applied pressure v. time representative of the
operation of devices and methods according to some embodiments. This plot
represents one cycle of applied pressure within the pressure chamber. Here,
the
negative pressure period is between To and T1, and the atmospheric pressure
period is
from Ti to T2. In some embodiments, the negative pressure period To-Ti is
approximately 10 seconds in duration, and the atmospheric pressure period Ti-
T2 is
approximately 7 seconds in duration. The transition from atmospheric pressure
to
negative pressure is indicated at To and T2, and the transition from negative
pressure
to atmospheric pressure is indicated at Ti. As described above, in some
preferred
embodiments, the transition from atmospheric pressure Po to the negative
pressure Pi
(i.e. from 0 mmHg to -40 mmHg in some embodiments) is a sharp transition
resulting
in rapid pressure change, i.e. pressure transition in less than 50% of the
duration of the
negative pressure period TO-Ti. In this embodiment, the transition to the
atmospheric
pressure period, at T1, results in a pressure P2 greater than atmospheric
pressure PO
being applied for a portion or all of the atmospheric pressure period Ti-T2.
In some
embodiments, the application of a positive pressure during the atmospheric
pressure
period Ti-T2 can have certain beneficial effects. For example, the positive
pressure P2
exerts force on the patients limb, causing veins to empty faster and further
improve
circulation. Moreover, positive pressure P2 applied within the pressure
chamber gap
can press the sleeve and/or heat transfer element against the limb of the
patient,
improving passive diffusion of heat to or from the limb. Thus, the applied
pressure v.
time plot of Figure 13 is representative of the desired operation of some
embodiments.
Some embodiments can enhance the in situ or in transit operation of the device
by reducing the effect of ambient temperature on the temperature adjustment of
the
patient. In situations requiring in situ or in transit adjustment of a
patient's core body
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temperature it is often the case that the ambient temperature about the
patient is the
cause of or contributes to the patient's condition. For instance, an ambient
temperature lower than the core body temperature of a hypothermic patient only
further contributes to the patient's condition. A closed system device,
according to
some embodiments, is a device such that substantially all air displaced within
the
components of the device during introduction of the negative pressure is
retained
within the device. For example, with reference to Figure 8, to introduce a
negative
pressure within the pressure chamber 110, a volume of air can be transferred
from the
pressure chamber 110 to the control unit 105 (e.g. to the second chamber 835).
This
volume of air has been temperature adjusted while within the pressure chamber
110
due to the application of the adjustment temperature. During the negative
pressure
period, this temperature adjusted air can be pumped via pump 810 to first
chamber
830. Then, to release the negative pressure from the pressure chamber 110 and
return
the chamber to atmospheric pressure, substantially the same volume of air can
be
transferred from the control unit 105 (e.g. first chamber 830) to the pressure
chamber
110 rather than drawing ambient temperature, environmental air into the
pressure
chamber 110. Thus, embodiments of the invention reduce the impact of
introducing
environmental air into the pressure chamber by recycling the temperature
adjusted air
within the pressure chamber during successive pressure cycles.
Closed system portable devices can be advantageous for a number of reasons.
For example, as described above, the effect of ambient temperature on the
temperature adjustment of the patient is reduced. In addition, closed systems
can
provide for more power efficient devices by reducing the amount of heating or
cooling performed by the system. Because the closed system re-circulates
temperature adjusted air, the temperature within the pressure chamber can be
maintained at the adjustment temperature with less heating or cooling by the
heat
transfer element. Thus, the work load, and therefore the power draw, of the
heat
transfer element is reduced. Moreover, the re-circulated, temperature adjusted
volume of air can also serve to heat or cool other components within the
control unit
which can further improve device performance. For example, in some
embodiments,
batteries used to power the portable device operate more effectively when
warmed, so
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device performance in cool environmental conditions can be improved by
providing a
closed system.
Figures 12A - 12D show a schematic representation of the operation of an
embodiment of the device 1200 providing for substantially square-wave
transitions
between pressure periods. The shown abstractions of the pressure chamber 1205,
first
chamber 1210, and second chamber 1215, can correlate, for example, with the
pressure chamber 110, first chamber 830, and second chamber 835, of the
embodiment shown in Figure 8. Initially, as shown in Figure 12A, the pump 1220
is
off, and valve 1225 is open allowing fluid communication between each of the
pressure chamber 1205, first chamber 1210, and second chamber 1215 each
chamber
being at approximately atmospheric pressure. When the device is actuated, as
shown
in Figure 12B, valve 1225 is closed and the pump 1220 is turned on. While on,
the
pump displaces air from the second chamber 1215 and into the first chamber
1210,
thus causing a negative pressure to build up in the second chamber 1215 while
increasing the pressure within the first chamber 1210. The pressure within the
pressure chamber 1205 remains at approximately atmospheric pressure. In some
embodiments, an escape valve 1230 may be opened to release some air from the
first
chamber 1210 during the initial building of a negative pressure within the
second
chamber 1215. In addition, the negative pressure built up within the second
chamber
may be greater than (i.e. more negative than) the desired negative pressure to
be
applied within the pressure chamber.
Next, as shown in Figure 12C representing the device state during the negative
pressure period referenced above, the valve connects the second chamber 1215
with
the pressure chamber 1205 causing air to flow from the pressure chamber 1205
to the
second chamber 1215 and the pressures within each of these chambers to
equalize.
Pump 1220 remains on as necessary to draw the pressure within the pressure
chamber
towards the desired negative pressure, and maintain it at that level. Air
pumped from
the second chamber 1215 is delivered to the first chamber causing the first
chamber to
maintain a positive pressure relative to the pressure chamber 1205 and, in
some
embodiments, atmospheric pressure. In some embodiments, excess air may leak
1235
into the system, e.g. at an imperfect seal of the pressure chamber 1205. Over
time,
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this extra volume of air could cause excess pressure to build within the
system,
namely within the first chamber 1210 during the negative pressure period.
Thus, in
some embodiments, an escape valve 1230 connected with the first chamber 1210
or
elsewhere within the system can be opened to allow excess air to escape the
system.
Figure 12D represents the device state during the atmospheric pressure period
referenced above. During this period, the valve 1225 switches to connect the
first
chamber 1210 with the pressure chamber 1205. With this connection in place,
air
flows from the first chamber 1210 to the pressure chamber 1205 and the
pressure
chamber is restored to approximately atmospheric temperature. An escape valve
coupled with the first chamber 1210 can be opened as necessary to during this
period
to allow the first chamber and pressure chamber to equalize at approximately
atmospheric temperature. Additionally, during the atmospheric pressure period,
pump
1220 remains on as necessary to accumulate negative pressure within the second
chamber 1215. As above, this negative pressure may be greater than the desired
negative pressure to be applied within the pressure chamber.
As described with reference to Figures 12A - 12D above, some embodiments
of the invention introduce a negative pressure to the pressure chamber only
after the
negative pressure has been pre-accumulated within another chamber of the
device.
Such operation is preferred because it provides for sharper transitions from
the
positive pressure period to the negative pressure period. Additionally, by
allowing a
positive pressure to build within the first chamber prior to the positive
pressure
period, the transition time from the negative pressure period to the positive
pressure
period is reduced. Thus, some embodiments can provide the substantially square-
wave operation.
Another advantage of devices providing for operation according to
embodiments of Figures 12A - 12D is that they provide for closed system
operation.
As described above, closed system devices can reduce the effect of the ambient
temperature on the temperature adjustment of the patient and increase the
power
efficiency of the device. The term "closed system," as used herein refers to a
device
where substantially all air displaced within the system during generation of
the
negative pressure is retained within the device. While closed system devices
capable
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of substantially instantaneous pressure changes are preferred, this disclosure
should
not be read to exclude embodiments which do not provide for square-wave and
closed
system operation with regard to the pressure changes within the device. For
example,
in some devices, negative pressure can be introduced by removing air directly
from
the pressure chamber. Moreover, negative pressure can be released by opening a
valve to connect the pressure chamber with the environment.
In another aspect, embodiments of the invention provide methods for the in
situ or in transit adjustment of a patient's core body temperature. In one
such method,
a limb of the patient is installed with a sleeve comprising an absorbent
material.
Either before installing the sleeve about the limb or after the sleeve has
been installed,
the sleeve is wetted with a liquid. The limb having the wetted sleeve
installed thereon
is inserted into a pressure chamber such that the limb is substantially sealed
from
external conditions. The pressure chamber can be any pressure chamber
described
herein, and generally comprises a substantially rigid casing and a
heating/cooling
element within the casing. Substantially all liquid in the interior of the
pressure
chamber can be carried by the sleeve. Depending upon the application, the
heating/cooling element is activated to either (a) increase the temperature
within the
pressure chamber to a heating temperature or (b) decrease the temperature
within the
pressure chamber to a cooling temperature. Negative pressure is alternatingly
introduced to the pressure chamber and released from the pressure chamber,
such that
when the negative pressure is released from the pressure chamber, the pressure
chamber is at approximately atmospheric pressure. In some preferred
embodiments,
the step of alternatingly introducing a negative pressure to the chamber can
be a
closed system process accomplished as described above.
In such a method, the wetting of the sleeve can be accomplished in a number
of ways that lend to the in situ or in transit use of the method. For example,
in some
embodiments, the sleeve can be wetted by submerging the limb having the sleeve
installed thereon within a volume of the liquid. For example, in some
embodiments
the pressure chamber can be filled or partially filled with a liquid, and a
limb having
the thermal transfer sleeve installed thereon can be inserted into the
pressure chamber.
In such case, a volume of the liquid may be displaced from the pressure
chamber,
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while a large portion of the liquid is absorbed by the thermal transfer
sleeve. Any
excess liquid within the chamber can then be emptied out. Alternatively, a
volume of
the liquid can be poured over a limb having the sleeve installed thereon.
Further still,
some embodiments can include a channel or inlet within an exterior surface of
the
pressure chamber through which the liquid can be supplied. In such
embodiments,
the limb having the sleeve installed thereon can be inserted into the dry
pressure
chamber, and the liquid can then be delivered into the device through the
channel or
inlet. In each case, the liquid can be selected from generally any available
source, for
example, a canteen of drinking water or liquid from a nearby river, pond, or
other
natural water source. In another aspect, some embodiments include the
installation of
a pre-wet thermal transfer sleeve. If a pre-wet sleeve is used the step of
wetting the
sleeve includes removing the pre-wet sleeve from its packaging prior to
installation.
Thus, with such sleeves, no additional liquid source is necessary at the
locale of use.
In some embodiments, the step of installing the sleeve about the limb and
wetting the sleeve further comprise the step of ensuring that the thermal
transfer
sleeve is in skin tight contact about the limb. As described above, in some
embodiments, it is desirable for the thermal transfer sleeve to contact the
limb such
that air gaps between the sleeve and limb are minimized to improve thermal and
pressure transfer from the pressure chamber to the limb. To ensure the sleeve
is in
skin tight contact about the limb, a user or the patient can start at the
distal end of the
limb and press the sleeve against the limb, working back toward the open
proximal
end. Such a method can further operate to remove excess liquid from the
thermal
transfer sleeve.
In some embodiments, methods according to the present invention further
include preparing the limb for installation. For example, in embodiments which
include anatomical features, e.g. a wrist feature, it can often be difficult
to properly
insert a patient's limb into the pressure chamber. This is because a narrow
portion of
the chamber created by the inclusion of the anatomical feature can impede the
limb's
path into the chamber. In cases where methods and devices according to
embodiments of the invention are being installed upon an unconscious patient,
inserting the limb into the chamber can be especially difficult and improper
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installation can result in injury to the patient. Thus, preparing the limb for
insertion
into the pressure chamber can include the step of straightening the limb or
ensuring
that the limb is straightened prior to insertion. For example, where the limb
is an arm
and the pressure chamber includes a wrist portion, preparing the limb for
installation
can include straightening the fingers to provide a minimal cross-sectional
size for
insertion of the hand beyond the wrist portion and to reduce the incidence of
injury to
the patient. Moreover, in some embodiments insertion into the chamber can be
facilitated by temporarily expanding the pressure chamber. Such methods are
preferable where the pressure chamber is an expandable pressure chamber such
as
those described above with reference to Figures 5A - 5C.
Methods according to embodiments of the invention can be especially useful
for in situ or in transit adjustment of a patient's core body temperature. To
facilitate
such use, the method can include the step of transporting a system or device
according
to any of the embodiments discussed above to the location of a patient in need
of
temperature adjustment. Such a method can be especially useful where the
patient is
immobile or unconscious. To deliver the device to the patient, the device can
be
hand-carried or connected with a vehicle such as, e.g. an ambulance.
Preferably, the
device can be hand-carried within a carrying case. Upon reaching the patient,
the
portable device can be removed from the carrying case. In some embodiments, it
may
be necessary to ensure that the control unit is in fluid connection with the
pressure
chamber. If not, the pressure chamber should be connected with the control
unit
either directly or, preferably, with a connector. In some instances, it is
important to
ensure that the limb is substantially sealed from external conditions. For
example,
where the device has been brought to a hypothermic patient in a cold
environment,
ensuring that the limb is substantially sealed from the cold external
environment can
enhance operation of the device and method. Then the remainder of the steps
for
using the device can be carried out in the location of the patient (in situ)
or as the
patient is being transported (in transit).
Moreover, it should be recognized that devices and methods according to
some embodiments can be used in manners different from those described above
to
accomplish some of the functionality described above. For example, embodiments
of
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the devices described above can be used to heat or cool a patient without the
application of a pulsating pressure. In such case, the heat transfer element
(alone or
with the thermal transfer sleeve) can be used to heat or cool a limb inserted
into a
pressure chamber without the application of pressure or with a constant
pressure
applied within the chamber. Although generally less effective, in most cases,
than the
uses described above such alternative use may provide for in situ or in
transit heating
or cooling of a patient if, for example, the pump of the device were to break.
Likewise, embodiments of devices and methods can be used to apply a pressure
or
pulsating pressure to the limb of a patient without the application of a
heating or
cooling temperature. Accordingly, the device can be used to increase blood
flow
within a limb of a patient who does not require temperature adjustment.
Device aspects of the present invention include the following:
1. A portable device for in situ or in transit adjustment of a core
body temperature of a patient, the device comprising:
a thermal transfer sleeve adapted to receive a limb of the
patient such that the thermal transfer sleeve is in contact with the limb;
a pressure chamber comprising (a) a substantially rigid casing
adapted to receive the limb and thermal transfer sleeve, and (b) a heat
transfer element adapted to apply an adjustment temperature within the
casing; and
a control unit connectable to the pressure chamber and adapted,
when connected to the pressure chamber, to alternatingly introduce a
negative pressure to the pressure chamber during a negative pressure
period and release the negative pressure from the pressure chamber to
restore the pressure chamber to approximately atmospheric pressure
during an atmospheric pressure period,
wherein the thermal transfer sleeve, pressure chamber, and
control unit are configured to fit within a carrying case such that the
portable device and the carrying case can be manually carried by an
individual.
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2. The portable device of device aspect 1, wherein the limb is an
arm.
3. The portable device of device aspect 1, wherein when the
thermal transfer sleeve has received the limb, the thermal transfer sleeve is
in
skin-tight contact with the limb.
4. The portable device of device aspect 1, wherein the thermal
transfer sleeve comprises a wettable material formed to receive the limb, the
wettable material adapted to be wetted with a liquid.
5. The portable device of device aspect 4, wherein when the limb
and thermal transfer sleeve are installed within the pressure chamber,
substantially all of the liquid within the pressure chamber is contained
within
the thermal transfer sleeve.
6. The portable device of device aspect 4, wherein the wettable
material is a high-absorbency material.
7. The portable device of device aspect 4, wherein the liquid is
water.
8. The portable device of device aspect 1, wherein the control unit
and pressure chamber when connected, comprise a substantially closed system
in that (a) introducing the negative pressure to the pressure chamber
comprises
transferring an amount of air from the pressure chamber to the control unit
and
(b) releasing the negative pressure from the pressure chamber comprises
transferring substantially the same amount of air from the control unit to the
pressure chamber.
9. The portable device of device aspect 1, wherein during
operation substantially all air flow caused by the introduction and release of
the negative pressure is contained within the control unit and the pressure
chamber.
10. The portable device of device aspect 1, wherein the control unit
comprises:
a portable housing having first and second chambers and a
connector input for providing fluid connection to the pressure chamber,
the second chamber being substantially air impermeable;
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a pump coupled to the portable housing and being (a) in fluid
communication with the second chamber and (b) adapted to displace
air from the second chamber;
a valve coupled to the housing and adapted to alternatingly
connect the connector input with the first chamber and the second
chamber;
a controller adapted to control (a) the pump and valve, thereby
controlling the introduction and the release of the negative pressure to
and from the pressure chamber and (b) the adjustment temperature
applied within the pressure chamber; and
a power supply coupled to the portable housing and adapted to
supply power to the pump, the valve, the controller, and the heat
transfer element.
11. The portable device of device aspect 1, wherein the limb is an
arm and the casing is formed to substantially conform to the arm, the casing
comprising a narrower wrist portion disposed between wider hand and forearm
portions.
12. The portable device of device aspect 1, wherein the casing is
anatomically formed to substantially conform to the limb.
13. The portable device of device aspect 11, wherein the casing is
expandable to facilitate insertion of the limb.
14. The portable device of device aspect 13, wherein the casing is
hinged along one side edge and expandable in that it is openable along an
opposed side edge.
15. The portable device of device aspect 14, wherein the opposed
side edge includes one or more alignment members proximate the opposed
side edge adapted to prevent misalignment during opening and closing of the
casing.
16. The portable device of device aspect 13, the pressure chamber
further comprising:
a substantially elastic outer shell positioned about an exterior
surface of the casing, the outer shell adapted to bias the casing closed,
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yet to allow for expansion of the casing to facilitate insertion of the
limb.
17. The portable device of device aspect 16, wherein the outer shell
comprises Neoprene.
18. The portable device of device aspect 1, the pressure chamber
further comprising an extension feature providing for extension of the
pressure
chamber thereby allowing a larger portion of the limb to be received.
19. The portable device of device aspect 1, wherein the heat
transfer element comprises:
a mitten positioned inside the casing adapted to contact the
thermal transfer sleeve when the limb and thermal transfer sleeve are
received in the casing; and
one or more thermoelectric devices installed within the mitten
and adapted to thermally communicate with the limb when the limb
and thermal transfer sleeve are received in the casing.
20. The portable device of device aspect 19, wherein the mitten
comprises Neoprene.
21. The portable device of device aspect 19, wherein the heat
transfer element further comprises a temperature sensor connected with
thermal control circuitry for regulating the adjustment temperature.
22. The portable device of device aspect 1, the pressure chamber
further comprising:
a seal element adapted to seal the pressure chamber about the
limb when the limb is received by the pressure chamber.
23. The portable device of device aspect 22, wherein the seal
element comprises a cuff comprising a stretchable material.
24. The portable device of device aspect 1, further comprising the
carrying case.
25. A portable device for the adjustment of a core temperature of a
patient, the portable device comprising:
a thermal transfer sleeve, adapted to receive a limb of the
patient and to be wetted such that the thermal transfer sleeve is in
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contact with a surface of the limb and air between the thermal transfer
sleeve and the surface is minimized;
a pressure chamber, adapted to receive the limb and the thermal
transfer sleeve and to apply an adjustment temperature to the limb via
the thermal transfer sleeve; and
a control unit connectable to the pressure chamber and adapted,
when connected to the pressure chamber, to alternatingly introduce a
negative pressure to the pressure chamber during a negative pressure
period and release the negative pressure from the pressure chamber to
restore the pressure chamber to approximately atmospheric pressure
during an atmospheric pressure period,
wherein, when the limb and the thermal transfer sleeve are
inserted into the pressure chamber substantially all of any liquid within
the pressure chamber is carried by the thermal transfer sleeve.
26. The portable device of device aspect 25, wherein the thermal
transfer sleeve comprises a pre-wet sleeve.
27. The portable device of device aspect 25, wherein the control
unit comprises:
a portable housing having first and second chambers and a
connector input for providing fluid connection to the pressure chamber,
the second chamber being substantially air impermeable;
a pump coupled to the portable housing and being (a) in fluid
communication with the second chamber and (b) adapted to displace
air from the second chamber;
a valve coupled to the housing and adapted to alternatingly
connect the connector input with the first chamber and the second
chamber;
a controller adapted to control (a) the pump and valve, thereby
controlling the introduction and the release of the negative pressure to
and from the pressure chamber and (b) the adjustment temperature
applied within the pressure chamber; and
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a power supply coupled to the portable housing and adapted to
supply power to the pump, the valve, the controller, and the heat
transfer element.
28. The portable device of device aspect 27, wherein the control
unit's pump includes a pump outlet that is in fluid communication with the
first chamber.
29. The portable device of device aspect 27, wherein the first
chamber of the control unit is substantially air impermeable.
30. The portable device of device aspect 29, wherein the control
unit further comprises an escape valve mounted within the portable housing
for periodically relieving an excess pressure build-up from the first chamber.
31. The portable device of device aspect 25, wherein the control
unit is connectable to the pressure chamber by a length of flexible tubing.
32. A portable device for in situ or in transit adjustment of a core
body temperature of a patient, the portable device comprising:
a portable pressure chamber adapted to receive a limb of the
patient;
a thermal transfer means for receiving the limb of the patient,
facilitating insertion of the limb into the portable pressure chamber,
and, when inserted into the portable pressure chamber with the limb,
carrying substantially all of any liquid within the portable pressure
chamber;
a temperature adjustment means for applying an adjustment
temperature to the thermal transfer means and thereby to the limb
when the thermal transfer means and the limb are inserted into the
portable pressure chamber; and
a pressure application means for alternatingly introducing a
negative pressure about the limb and thermal transfer means during a
negative pressure period and releasing the negative pressure to restore
atmospheric pressure about the limb during an atmospheric pressure
period when the thermal transfer means and the limb are inserted into
the portable pressure chamber.
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33. The portable device of device aspect 32, wherein the pressure
application means alternatingly introduces and removes the negative pressure
about the limb in a substantially square-wave fashion.
34. The portable device of device aspect 32, wherein the portable
device further comprises a carrying case, the portable pressure chamber,
thermal transfer means, temperature adjustment means, and pressure
application means being configured to fit within the carrying case such that
the
portable device and the carrying case can be manually carried by an
individual.
[QD] Method aspects of the present invention include the following:
1. A method for in situ or in transit adjustment of a core body
temperature of a patient, the method comprising the steps of:
installing a sleeve comprising an absorbent material about a
limb of the patient;
wetting the sleeve with a liquid;
inserting the limb having the wetted sleeve installed thereon
into a pressure chamber such that the limb is substantially sealed from
external conditions, wherein the pressure chamber comprises a
substantially rigid casing and a heating/cooling element within the
casing, and substantially all liquid in the interior of the pressure
chamber is carried by the sleeve;
activating the heating/cooling element to selectively (a)
increase a temperature within the pressure chamber to a heating
temperature or (b) decrease the temperature within the pressure
chamber to a cooling temperature; and
alternatingly introducing a negative pressure to the pressure
chamber during a negative pressure period and releasing the negative
pressure from the pressure chamber to restore the pressure chamber to
approximately atmospheric pressure during an atmospheric pressure
period.
2. The method of method aspect 1, wherein the step of wetting the
sleeve occurs after the step of installing the sleeve about the limb.
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3. The method of method aspect 1, wherein the step of wetting the
sleeve comprises submerging the limb and the sleeve within a volume of the
liquid.
4. The method of method aspect 1, wherein the steps of installing
the sleeve and wetting the sleeve comprise ensuring that the sleeve is
generally
skin tight about the limb.
5. The method of method aspect 1, wherein the step of
alternatingly introducing and releasing the negative pressure within the
pressure chamber comprises a closed-system process.
6. The method of method aspect 1, wherein the step of
alternatingly introducing and releasing the negative pressure comprises:
generating the negative pressure within a first chamber of a
control unit connected to the pressure chamber during the atmospheric
pressure period; and
fluidly connecting the first chamber of the control unit with the
pressure chamber thereby transitioning to the negative pressure period,
wherein during the negative pressure period a second chamber
of the control unit is maintained at a pressure greater than the negative
pressure.
7. The method of method aspect 6, wherein the step of releasing
the negative pressure from the pressure chamber comprises disconnecting the
pressure chamber from the first chamber and fluidly connecting the pressure
chamber with the second chamber of the control unit thereby transitioning to
the atmospheric pressure period.
8. The method of method aspect 6, wherein during the negative
pressure period the second chamber of the control unit is maintained at a
pressure greater than atmospheric pressure.
9. The method of method aspect 6, further comprising the step of:
periodically releasing pressure from the second chamber of the
control unit that has accumulated during the alternating introduction
and release of the negative pressure, thereby preventing over-
pressurization of the control unit.
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10. The method of method aspect 6, wherein the step of generating
the negative pressure within the first chamber of the control unit comprises
pumping a volume of air from the first chamber to the second chamber thereby
increasing the pressure within the second chamber.
11. The method of method aspect 1, wherein the step of activating
the heating/cooling element comprises controlling the temperature within the
pressure chamber with a temperature control unit coupled with a control unit
connected to the pressure chamber.
12. The method of method aspect 1, wherein the patient is a
hypothermic patient, the step of activating the heating/cooling element
comprising increasing the temperature within the pressure chamber to the
heating temperature.
13. The method of method aspect 1, wherein the negative pressure
period is approximately 10 seconds in duration.
14. The method of method aspect 1, wherein the atmospheric
pressure period is approximately 7 seconds in duration.
15. The method of method aspect 1, wherein the negative pressure
period is approximately 10 seconds in duration and the atmospheric pressure
period is approximately 7 seconds in duration.
16. The method of method aspect 1, wherein the patient is
unconscious and the step of inserting the limb includes preparing the limb for
insertion.
17. The method of method aspect 16, wherein the casing of the
pressure chamber comprises wrist portion having a reduced size cross-
sectional profile between hand and forearm portions having larger size cross-
sectional profiles, the limb comprises an arm and a hand, and the step of
preparing the limb for insertion includes straightening fingers of the hand
for
insertion beyond the wrist portion.
18. The method of method aspect 1, wherein the heating
temperature is greater than or equal to the core body temperature of the
patient.
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19. The method of method aspect 1, wherein the heating
temperature is between approximately 38.0 C and approximately 43.5 C.
20. The method of method aspect 19, wherein the heating
temperature is approximately 43.0 C.
21. The method of method aspect 1, wherein the cooling
temperature is less than or equal to the core body temperature of the patient,
but greater than a temperature known to cause vessels of the limb to
constrict.
22. The method of method aspect 1, wherein the cooling
temperature is between approximately 22.0 C and approximately 24.0 C.
23. The method of method aspect 22, wherein the cooling
temperature is 23.0 C.
24. A method for in situ or in transit adjustment of a core body
temperature of an unconscious patient, the method comprising the steps of:
providing (i) a pressure chamber comprising a substantially
rigid casing and a heating/cooling element within the casing, (ii) a
thermal transfer sleeve, and (iii) a control unit in fluid connection with
the pressure chamber and adapted to control a chamber pressure
therewithin;
installing the thermal transfer sleeve about a limb of the
unconscious patient;
preparing the limb for insertion into the pressure chamber, the
limb having the thermal transfer sleeve installed thereon;
after having prepared the limb for insertion into the pressure
chamber, inserting the limb into the pressure chamber such that the
limb is substantially sealed from external conditions; and
activating the control unit, thereby (a) activating the
heating/cooling element to selectively (i) increase a temperature within
the pressure chamber to a heating temperature or (ii) decrease the
temperature within the pressure chamber to a cooling temperature, and
(b) alternatingly introducing a negative pressure within the pressure
chamber and releasing the negative pressure from the pressure
chamber.
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25. The method of method aspect 24, wherein the casing has an
anatomical feature with a reduced size cross-sectional profile and the step of
preparing the limb for insertion into the pressure chamber comprises arranging
the limb to fit beyond the anatomical feature of the casing.
26. The method of method aspect 25, wherein the anatomical
feature of the casing comprises a wrist portion disposed between hand and
forearm portions having larger cross-sectional profiles, the limb comprises an
arm and hand, and preparing the arm and hand for insertion into the pressure
chamber comprises straightening the fingers and thumb of the hand to reduce
the incidence of injury to the unconscious patient.
27. The method of method aspect 24, wherein the step of inserting
the limb into the pressure chamber comprises temporarily expanding the
pressure chamber to facilitate insertion of the limb.
28. The method of method aspect 24, wherein the negative pressure
is introduced within the pressure chamber by removing a volume of air from
the pressure chamber and transferring the volume of air to the control unit.
29. The method of method aspect 28, wherein the negative pressure
is released from the pressure chamber by returning the volume of air to the
pressure chamber from the control unit.
30. A method for in situ or in transit adjustment of a core body
temperature of a patient, the method comprising the steps of:
manually carrying a portable device in a carrying case, the
portable device comprising (i) a pressure chamber comprising a
substantially rigid casing and a heating/cooling element within the
casing, (ii) a thermal transfer sleeve, and (iii) a control unit fluidly
connectable with the pressure chamber and adapted to control a
chamber pressure therewithin;
removing the portable device from the carrying case;
checking that the control unit is in fluid connection with the
pressure chamber and if not, connecting the control unit with the
pressure chamber;
installing the thermal transfer sleeve about a limb of the patient;
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preparing the limb for insertion into the pressure chamber, the
limb having the thermal transfer sleeve installed thereon;
after having prepared the limb for insertion into the pressure
chamber, inserting the limb into the pressure chamber such that the
limb is substantially sealed from external conditions;
activating the control unit, thereby (a) activating the
heating/cooling element to selectively (i) increase a temperature within
the pressure chamber to a heating temperature or (ii) decrease the
temperature within the pressure chamber to a cooling temperature, and
(b) alternatingly causing the chamber pressure to decrease to a negative
pressure and causing the chamber pressure to increase to
approximately atmospheric pressure.
31. The method of method aspect 30, wherein the step of preparing
the limb for insertion into the pressure chamber comprises wetting the thermal
transfer sleeve with a liquid.
32. The method of method aspect 30, wherein the step of activating
the control unit causes the chamber pressure to alternatingly decrease and
increase in a substantially square-wave fashion.
33. The method of method aspect 30, wherein the step of causing
the chamber pressure to decrease comprises transferring air from the pressure
chamber to the control unit.
34. The method of method aspect 30, wherein the step of causing
the chamber pressure to increase comprises transferring air from the control
unit to the pressure chamber.
35. The method of method aspect 30, wherein the negative pressure
is between -20 mmHg and -80 mmHg (-2.7 kPa and -10.7 kPa).
36. The method of method aspect 35, wherein the negative pressure
is -40 mmHg (-5.3 kPa).
37. A method for in situ or in transit adjustment of a core body
temperature of a patient, the method comprising the steps of:
providing a portable temperature management system
configured to fit within a carrying case such that the carrying case and
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portable temperature management system can be manually carried by
an individual, the portable temperature management system
comprising (i) a thermal transfer sleeve, (ii) a pressure chamber
comprising a substantially rigid casing and a heat transfer element
within the casing, and (iii) a control unit connectable to the pressure
chamber;
installing the thermal transfer sleeve about a limb of the patient;
inserting the limb having the thermal transfer sleeve installed
thereon into the casing such that the limb is substantially sealed from
external conditions;
activating the control unit, thereby (i) activating the heat
transfer element to apply an adjustment temperature within the casing
and (ii) alternatingly introducing a negative pressure within the
pressure chamber and releasing the negative pressure from the pressure
chamber.
38. The method of method aspect 37, wherein the adjustment
temperature is between 38.0 C and 43.5 C.
39. The method of method aspect 38, wherein the adjustment
temperature is 43.0 C.
40. The method of method aspect 37, wherein the adjustment
temperature is between 20.0 C and 25.0 C.
41. The method of method aspect 40, wherein the adjustment
temperature is 23.0 C.
42. The method of method aspect 37, wherein the step of
alternatingly introducing and releasing the negative pressure comprises
introducing the negative pressure for approximately 10 seconds.
43. The method of method aspect 37, wherein the step of
alternatingly introducing and releasing the negative pressure comprises
releasing the negative pressure for approximately 7 seconds.
44. The method of method aspect 37, wherein the step of
alternatingly introducing and releasing the negative pressure comprises
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introducing the negative pressure for approximately 10 seconds and releasing
the negative pressure for approximately 7 seconds.
45. The method of method aspect 37, wherein the negative pressure
is between -20 mmHg and -80 mmHg (-2.7 kPa and -10.7 kPa).
46. The method of method aspect 45, wherein the negative pressure
is -40 mmHg (-5.3 kPa).
Although the present invention has been described in considerable detail with
reference to certain disclosed embodiments, the disclosed embodiments have
been
presented for purposes of illustration and not limitation and other
embodiments of the
invention are possible. One skilled in the art will appreciate that various
changes,
adaptations, and modifications may be made without departing from the spirit
of the
invention and the scope of the appended claims.
