Note: Descriptions are shown in the official language in which they were submitted.
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Automatic Lightweight Electro-Mechanical Chest Compression
Device and Temperature Regulation System Therefor
Field of the Inventions
The inventions described below relate the field of
cardiopulmonary resuscitation and in particular to automatic
chest compression devices.
Background of the Inventions
Cardiopulmonary resuscitation (CPR) is a well-known and
valuable method of first aid used to resuscitate people who
have suffered from cardiac arrest. CPR requires repetitive
chest compressions to squeeze the heart and the thoracic
cavity to pump blood through the body. Artificial
respiration, such as mouth-to-mouth breathing or a bag mask
apparatus, is used to supply air to the lungs. When a first
aid provider performs manual chest compression effectively,
blood flow in the body is about 25% to 30% of normal blood
flow. However, even experienced paramedics cannot maintain
adequate chest compressions for more than a few minutes.
Hightower, et al., Decay In Quality Of Chest Compressions Over
Time, 26 Ann. Emerg. Med. 300 (Sep. 1995). Thus, CPR is not
often successful at sustaining or reviving the patient.
Nevertheless, if chest compressions could be adequately
maintained, then cardiac arrest victims could be sustained for
extended periods of time. Occasional reports of extended CPR
efforts (45 to 90 minutes) have been reported, with the
victims eventually being saved by coronary bypass surgery.
See Tovar, et al., Successful Myocardial Revascularization and
Neurologic Recovery, 22 Texas Heart J. 271 (1995).
In efforts to provide better blood flow and increase the
effectiveness of bystander resuscitation efforts, various
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mechanical devices have been proposed for performing CPR. In
one variation of such devices, a belt is placed around the
patient's chest and an automatic chest compression device
tightens the belt to effect chest compressions. Our own
patents, Mollenauer et al., Resuscitation device having a motor
driven belt to constrict/compress the chest,
U.S. Patent 6,142,962 (Nov. 7, 2000); Bystrom et al.,
Resuscitation and alert system, U.S. Patent 6,090,056
(Jul. 18, 2000); Sherman et al., Modular CPR assist device,
U.S. Patent 6,066,106 (May 23, 2000); and Sherman et al.,
Modular CPR assist device, U.S. Patent 6,398,745
(Jun. 4, 2002); and Sherman et al., CPR assist device with
pressure bladder feedback, US Patent 6,616,620 (Sep. 9, 2003),
and Vijfvinkel, Surgical cutting tool, US Patent 6,939,314
(Sep. 6, 2005) show chest compression devices that compress a
patient's chest with a belt.
Since seconds count during an emergency, any CPR
device should be easy to use and facilitate rapid deployment of
the device on the patient. Our own devices are easy to deploy
quickly and may significantly increase the patient's chances of
survival. Nevertheless, a novel chest compression device has
been designed to further increase ease of use, further
facilitate rapid deployment and further increase the durability
and convenience of the device.
A problem encountered when building a lightweight,
compact electro-mechanical chest compression device was that
the device could overheat. (The motor, brake and electrical
systems all produce heat.) Overheating can damage the device
and may injure the patient.
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Summary
According to one embodiment of the present invention,
there is provided an electro-mechanical chest compression
device comprising: a housing; a motor disposed in the housing;
a channel beam mounted within the housing, said channel beam
laterally oriented with respect to the housing and defining a
channel across the housing; a drive spool spanning the channel
beam, said drive spool operably attached to the motor and
rotatably attached to the channel beam, wherein the motor is
capable of rotating the drive spool; and a belt attached to the
drive spool and disposed within the channel, said belt capable
of extending at least partially around the chest of a patient,
wherein rotation of the drive spool tightens the belt to
compress the chest of the patient.
According to another embodiment of the present
invention, there is provided an electro-mechanical chest
compression device comprising: a housing; a motor disposed in
the housing; a power source operably connected to the housing
and to the motor; a channel beam mounted within the housing,
said channel beam laterally oriented with respect to. the
housing and defining a channel across the housing; a drive
spool spanning the channel beam, said drive spool operably
attached to the motor and rotatably attached to the channel
beam, wherein the motor is capable of rotating the drive spool;
and a belt attached to the drive spool and disposed within the
channel, said belt capable of extending at least partially
around the chest of a patient, wherein rotation of the drive
spool tightens the belt to compress the chest of the patient.
In some embodiments, the devices and methods
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described below provide for an electro-mechanical chest
compression device that weighs less than 30 pounds when fully
assembled. The device is provided with a channel beam to
strengthen the device at the points where most of the force of
compressions is applied, thereby making it possible to create a
hollow device and to use lighter weight materials. The channel
beam also serves as a mount onto which a compression belt
cartridge may be installed, thereby allowing the belt to be
easily changed after each use. A slotted drive spool spans the
channel beam. The drive spool is attached to a motor that is
capable of rotating the drive spool. Spindles are disposed on
either end of the channel beam to guide the belt during
compressions and assist in conserving energy. In use, a
compression belt cartridge is provided, the belt is attached to
the slot in the drive spool and the belt is extended over and
around the spindles. The cartridge cover plate is then
attached to the channel beam. The patient is placed then on
the device and the belt is secured over and around the
patient's chest. When the motor rotates, the belt spools
around the drive spool, thereby tightening the belt.
Sufficient torque is generated that the belt compresses the
patient's chest.
Brief Description of The Drawings
Figure 1 illustrates a method of performing chest
compressions on a patient by using an automatic chest
compression device.
Figure 2 shows the anterior side of an electro-
mechanical chest compression device.
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described below provide for an electro-mechanical chest
compression device that weighs less than 30 pounds when fully
assembled. The device is provided with a channel beam to
strengthen the device at the points where most of the force of
compressions is applied, thereby making it possible to create a
hollow device and to use lighter weight materials. The channel
beam also serves as a mount onto which a compression belt
cartridge may be installed, thereby allowing the belt to be
easily changed after each use. A slotted drive spool spans the
channel beam. The drive spool is attached to a motor that is
capable of rotating the drive spool. Spindles are disposed on
either end of the channel beam to guide the belt during
compressions and assist in conserving energy. In use, a
compression belt cartridge is provided, the belt is attached to
the slot in the drive spool and the belt is extended over and
around the spindles. The cartridge cover plate is then
attached to the channel beam. The patient is placed then on
the device and the belt is secured over and around the
patient's chest. When the motor rotates, the belt spools
around the drive spool, thereby tightening the belt.
Sufficient torque is generated that the belt compresses the
patient's chest.
Brief Description of The Drawings
Figure 1 illustrates a method of performing chest
compressions on a patient by using an automatic chest
compression device.
Figure 2 shows the anterior side of an electro-
mechanical chest compression device.
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Figure 3 shows the inferior and posterior sides of the
automatic chest compression device.
Figure 4 shows the superior and posterior sides of the
automatic chest compression device.
Figure 5 shows a compression belt cartridge for use with
the chest compression device.
Figure 6 shows the inferior and posterior sides of the
automatic chest compression device with the superior and
inferior cover plates removed.
Figure 7 shows an exploded view of the automatic chest
compression device as seen from the posterior side of the
device.
Figure 8 shows an exploded view of part of the automatic
chest compression device, as seen from the anterior side of
the device without some posterior elements.
Figure 9 illustrates a method of performing chest
compressions on a patient when viewed from the side.
Figure 10 shows an exploded view of some of the internal
components of the device.
Detailed Description of the Inventions
Figure 1 shows the chest compression belt fitted on a
patient 1. A chest compression device 2 applies compressions
with the belt 3, which has a right belt portion 3R and a left
belt portion 3L. The chest compression device 2 includes a
belt drive platform 4 and a compression belt cartridge 5
(which includes the belt). The belt drive platform includes a
housing 6 upon which the patient rests, a means for tightening
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the belt, a processor and a user interface disposed on the
housing. The belt includes pull straps 18 and 19 and wide load
distribution sections 16 and 17 at the ends of the belt. The
means for tightening the belt includes a motor attached to a
drive spool, around which the belt. spools and tightens during
use. The design of the chest compression device, as shown
herein, allows for a lightweight electro-mechanical chest
compression device. The fully assembled chest compression
device weighs only 29 pounds, and is thus hand-portable over
long distances. (The device itself weighs about 22.0 to 23.0
pounds, the battery weighs about 5.0 pounds, the belt
cartridge weighs about 0.8 pounds and the straps to secure the
patient weigh about 1.6 pounds.) To date, the chest
compression device described below is the only self-contained
electro-mechanical or belt-based automatic chest compression
device known to the inventors that weighs less than 30 pounds.
Figure 2 shows the anterior side of an electro-mechanical
chest compression device 2. The chest compression device
includes the belt drive platform 4 and the belt cartridge 5.
The belt drive platform includes a headboard 20, upon which
the patient's head rests, and a backboard 21, upon which the
patient's back rests. Preferably, the headboard and backboard
are part of one, integral plate of material. The chest
compression device 2 is described in relation to the patient
when the patient's back is on the backboard and the patient's
head is on the headboard. Thus, in normal use, the top of the
device is the anterior side 22 (the side upon which the
patient rests during use), the bottom of the device is the
posterior side 23 (the side facing the ground during use,
shown in Figures 3 and 4), the front of the device is the
superior side 24 and the back of the device is the inferior
side 25. The left side 26 and right side 27 of the device are
to the left and right of the patient, respectively, when the
device is in use.
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The device is lightweight and compact. The superior-
inferior height of the device (along arrow 28) is about 32
inches and the lateral width of the device (along arrow 29) is
about 19 inches. The anterior-posterior thickness of the
device is about 3 inches. The distance between a left belt
spindle 30 and a right belt spindle 31 is in the range of
about 12 inches to about 22 inches. Preferably, the distance
between the spindles is about 15 inches so that the device
will accommodate the vast majority of patients. Specifically,
the distance is measured from the lateral, outer edge of one
spindle to the lateral, outer edge of the other spindle. (The
device may be made ,larger to accommodate very large patients.)
In use, a belt cartridge is provided and is secured to
the posterior side of the chest compression device, as
described in reference to Figures 3 through 5. The patient is
then placed on the device. The belt extends over and around
the left spindle and the right spindle, under the patient's
axilla (armpits) and around the patient's chest. The load
distribution sections are then secured over the patient's
chest. The chest compression device then tightens the belt
repetitively to perform chest compressions.
Figures 3 and 4 show the posterior side 23 of the chest
compression device as seen from the inferior and superior
directions, respectively. (In the perspective of Figures 3
and 4, the average sized patient's buttocks and the back of
the patient's legs would extend past the inferior bumper 40.)
The device is built around a sturdy channel beam 41 that is
laterally oriented with respect to the housing. The channel
beam supports the device against the forces created during
compressions. The channel beam also serves as the structure
to which the belt cartridge is attached. The channel beam 41
,is formed from a single piece of cast aluminum alloy that
forms two walls perpendicular to a flat bottom portion. (The
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channel beam may be formed from separate components and of
other suitably strong and stiff materials, such as steel,
magnesium, or reinforced polymer composites.) To accommodate
the belt, the channel beam is about 2.5 inches high (along the
superior-inferior direction), about 12 inches to about 16
inches long (along the left-right direction) and about 2
inches deep (from the bottom portion to the top of a wall
portion).
The channel beam 41 forms a channel extending across the
lateral width of the device. During compressions, the belt is
disposed in and travels along the channel. The belt is
attached to a drive spool 42 that spans the channel. The drive
spool serves as a means for operably connecting the
compression belt to the motor. (The drive spool is shown in
phantom in Figure 3 to indicate its position near the bottom
surface of the channel beam.) The drive spool is less than 3
inches long and less than 1 inch in diameter. The drive spool
may be located anywhere within the channel beam. Preferably,
the drive spool extends across the channel beam at a location
slightly offset from the vertical centerline of the device.
For example, the drive spool may have a conical shape for
use with a cable attached to the pull straps (or when the belt
is replaced with a cable). During initial spooling, the cable
wraps around the base of the cone, thereby creating a large
mechanical advantage when starting a compression. The cable
then spools around the length of the cone, proceeding towards
the peak of the cone. The drive spool applies more torque to
the cable as the cable spools around the smaller diameter
portions of the cone, thereby applying a greater force to the
patient towards the end of a compression when the chest's
resistance to the compression is highest. (The shape of the
drive spool is the spooling profile of the device. The
spooling profile may be customized to take advantage of the
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speed versus torque trade-off from the drive train or from the
viscoelastic effects of the patient's chest).
The drive spool is provided with a slot 43 disposed along
the length of the spool shaft. A spline attached to the belt
is keyed to the shape of the drive spool slot. Thus, when the
spline is inserted into the drive spool slot, the belt is
securely fastened to the drive spool. A groove 44 in the
,
channel beam walls assists in aligning and securing the spline
to the drive spool slot. Similarly, one or more discs or
guide plates mounted on one or both walls of the channel beam
also assist in aligning and securing the spline to the drive
spool slot. (The guide plate may also be operably attached to
the drive spool or both the drive spool and the channel beam.)
The guide plate is attached to a spring that allows the guide
plate to move in and out of the channel, thereby allowing easy
removal of the spline. When the guide plate springs back
after insertion of the clip, the guide plate helps secure the
spline in place. The guide plate may be provided with a slot
sized and dimensioned to receive the spline, thereby further
securing the spline within the drive spool slot.
The left spindle 30 and right 31 spindle are disposed on
either end of the channel beam 41 and are mounted to the
channel beam walls via sealed bearings. The spindles are
hollow aluminum cylinders, having a length of about 2.5 inches
and a diameter of about 0.75 inches, to minimize weight and to
minimize their moments of inertia. The left and right
spindles allow the compression belt to easily travel around
the left and right sides of the device with a minimum of
friction, thus conserving energy. The left and right spindles
are disposed along the superior-inferior direction of the
device such that the belt will easily wrap around the
patient's chest when the patient is placed on the device. The
spindles are inset into the sides of the housing in order to
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protect the patient, rescuer and device components. Belt
guards disposed on the belt cartridge, shown in Figure 5, also
cover the spindles. The belt guards further protect the
patient, rescuer and device components.
Also disposed on or near the channel beam are means for
securing the compression belt cartridge to the channel beam.
For example, a number of blind holes or slots 45 are disposed
in the housing and along the edge of the channel beam.
Corresponding alignment tabs disposed on the compression belt
cartridge fit within the slots. The slots also have bosses or
detents 46 that extend outwardly and into the channel a short
distance. Snap latches disposed on the compression belt
cartridge fit securely, though removably, within the bosses or
detents. Similarly, a number of apertures 47 are disposed in
the housing and along the edges of the channel beam 41. The
compression belt cartridge is provided with tabs or hooks that
fit into the apertures, thus further securing the cartridge to
the channel beam. The slots and apertures are symmetrically
located about the medial axis of the device. However, placing
the slots and apertures asymmetrically about the medial axis
of the device can ensure that the cartridge is attached to the
channel beam in only one orientation.
In addition, the housing is provided with labeling, such
as triangle 48, to assist a user with correctly attaching the
compression belt cartridge. Labeling on the housing aligns
with corresponding labeling disposed on the compression belt
cartridge when the cartridge is correctly aligned with the
device. Contrasting colors are used in the region of the
triangle to further assist the user to align the cartridge.
Additional labeling 49 may be added to the device to aid in
aligning the patient with the device, or to provide warnings,
operation instructions or advertising information. For
example, recess 50 (shown in Figure 2) disposed across the
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width of the device provides a visual alignment marker. The
recess 50 also helps fluids to flow away from the surface of
the device.
Although the channel beam 41 forms the backbone of the
device, additional reinforcement for the device is provided by
the device housing. Referring again to Figures 3 and 4, the
shell housing comprises an anterior cover plate 60 attached to
two posterior cover plates, a superior cover plate 61 and an
inferior cover plate 62. The anterior cover plate is attached
to the superior cover plate and the inferior cover plate via a
plurality of threaded fasteners disposed in holes 63 or by
interlocking features that snap together.
The superior cover plate 61 is disposed superiorly to the
channel beam 41 and the inferior cover plate 62 is disposed
inferiorly to the channel beam. (The housing may be formed
from more or fewer cover plates, although using three cover
plates is a preferred design with the devices shown in the
Figures 2 through 7.) The three-piece shell design minimizes
shear forces applied to the fasteners connecting the cover
plates, thereby increasing the durability of the device. (The
channel beam absorbs most shear forces.) In addition, the
posterior edges of the channel interlock with ridges in the
superior and inferior cover plates to protect the fasteners
connecting the cover plates to the channel. Alignment pins
and bumpers interdigitate with the overlapping cover plates,
thereby providing further protection from shear forces.
The housing is constructed with rounded edges to minimize
impact damage to people or to the device. The housing is
formed from a hard, liquid-proof material that is easy to
clean, has low thermal conductivity and is resistant to fire,
electricity, chemicals, sun exposure and extreme weather
conditions. (Such materials include acrylonitrile butadiene
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.styrene, high molecular weight polyethylene, other polymer
=
plastics and lightweight metals such as aluminum and titanium;
however, metals should be provided with a coating or other
feature to make the housing non-conducting.)
=
Figure 5 shows. a compression belt .cartridge for use with
the chest compression device. The cartridge has a.belt 3, a.
spline 65 for attaching the belt to the chest compression
= device,' a belt cover plate 66 for protecting the belt, and
belt guards 67 rotatably attached to the belt cover plate .via
hinges 68. . (The belt guards are disposed around the spindles
. .'during use.)' The belt cartridge may also be provided with a
compression bladder 69, which it_placed between the belt and
the patient's sternum during compressions. An example of:a
compression bladder is shown in Vijfvinkel, Surgical cutting
tool, US Patent 6,939,314 (Sep. 6., 2005).
. To attach the belt. cartridge to the.chest=compression
device, thebelt spline 65 is inserted ihto.the drive spool
Slot 43. The belt cover Plate 66 is then secured to the
= channel beam 41 sand housing 6. by inserting hooks 70 on the.
belt cover plate into the corresponding apertures 47 in the
device and by inserting tabs and snap latches 71 within the
.slots 45 and bosses On the device. (The slots, apertures, .
tabs and hooks are aligned and begin sliding together prior to
= engagement of the snap latches within,the bosses.) Labeling =
. 25 =72 disposed on.the belt cover plate further assists the. user
to align the belt cover plate with the channel beam-. =
. Figures 6 and 7 show the internal components of the chest
.compression'device 2.' A motor 79 is operable to provide
torque to the drive spool 42 through a. clutch 80 and a gearbox .
. 30 81.' A brake 82, attached-to the superior side of the motor,
= is operable to brake the motion of the drive spool, The brake
hub connects directly to the rotor shaft of the motor.
=
11.
= .
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The drive spool extends across the channel is rotatably
attached to the walls of the channel beam via bearings.
Together, the drive spool, clutch, gearbox and brake compose
the drive train of the device. Preferably, the drive train is
not attached to any other component of the device or to the
device housing, except via attachment of the drive spool to
the channel beam. Thus, the drive train is cantilevered from
the channel beam. When cantilevered from the channel beam,
the drive train minimizes rotational resistance and rotational
inertia, reduces undesirable bending or shearing forces on the
components of the drive train, reduces the weight of the
overall device and improves air flow around the components of
the drive train (thereby improving cooling of those
components).
The gearbox contains a gear system having a gear ratio
that decreases the speed of the drive spool relative to the
clutch or motor drive shaft. The gear ratio preferably about
10:1. Useable gear systems include planetary gear systems
that operate in a straight line from the motor shaft to the
output shaft (which is the drive spool shaft). Still other
gear systems do not operate in a straight line, so that the
motor and output shafts need not be along the same line. In
the device shown in Figures 6 and 7, the drive spool is the
output shaft of the gearbox.
The clutch disengages the motor from the gearbox if too
much torque is applied to the drive spool. The control system
can also disengage the clutch based on other sensed
parameters; for example, the controller can control the clutch
to disengage when too much load, as pre-determined by the
manufacturer, is sensed at the load plate, when there is a
software error or upon other conditions. Thus, the clutch
serves as a safety mechanism for the chest compression device.
Optionally, the clutch can be used actively during
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compressions to aid in timing compressions and conserving
energy. An example of this use for a clutch is found in our
U.S. Patent 6,142,962. Preferably, the brake, motor, gearbox,
clutch and drive spool are alined in a straight line,
perpendicular to the channel beam 41.
The motor 79 and brake 82 are controlled by a processor
unit 83, motor controller 84 and power distribution controller
85, all of which are mounted to the inside of the anterior
cover plate 60. (The power distribution controller is not
shown in Figure 6 in order to clearly show the end of the
battery compartment.) The processor unit includes a computer
processor, a non-volatile memory device and a display. A user
may access the display through opening 86 in the housing.
Additional feedback is given to the user though speaker 87
mounted on bracket 88.
The processor unit is provided with software used to
control the power controller and the motor controller.
Together, the processor unit, power controller and motor
controller make up a control system capable of precisely
controlling the operation of the motor. Thus, the timing and
force of compressions are automatically and precisely
controlled for patients of varying sizes. Examples of
compression belt timing methods may be found in our U.S.
Patent 6,066,106 and in our US Patent 6,616,620.
The motor controller may also be operably connected to a
torque sensor that senses the torque applied by the motor to
the drive spool. In this case, the motor controller is
capable of automatically stopping the device if the torque
exceeds a pre-set threshold. The motor controller or
processor may also be attached to a biological sensor that
senses a biological parameter, such as end-tidal carbon
dioxide, pulse or blood pressure. The processor and motor
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controller are then operable to control the operation of the
device based on the sensed biological parameter. Examples of
motor control and biological feedback control are found in our
patent, Mollenauer et al., Resuscitation Device Raving a Motor
Driven Belt to Constrict/ Compress the chest, U.S. Patent
6,142,962 (Nov. 7, 2000). The motor controller or processor
may also be attached to a current sensor operable to sense the
current in the motor. A sudden spike in the motor current
indicates a sudden load on the motor, and is thus an
indication of how much torque is being applied to the patient.
Accordingly, control system may control the operation of the
device based on the measured current in the motor.
The processor unit is also attached to a rotary encoder
100 disposed in the inferior portion of the housing and
mounted on the channel beam 41. (The rotary encoder may be
replaced with a linear encoder operably disposed with respect
to the belt.) The rotary encoder measures the rotation of the
drive spool 42 and produces spool data corresponding to drive
spool rotation. The processor, together with an encoder
controller 101 mounted in the inferior portion of the housing,
translates the spool data into the total amount of belt take-
up and into the total depth of compression accomplished by the
system. The encoder controller converts pulses from the
encoder into a count and direction signal, and the processor
uses that signal to control the device. (The encoder
controller and the encoder may be located elsewhere in the
device; for example, the encoder may be located in the gearbox
and operably connected to one of the gear shafts.) Examples
of encoders as used with chest compression devices are found
' in our patent, Sherman et al., Modular CPR assist device, U.S.
Patent 6,066,106 (May 23, 2000) and in our Sherman et al.,
CPR assist device with pressure bladder feedback, US Patent 6,616,620
(Sep. 9, 2003).
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Referring again to Figures 6 and 7, a number of
additional features are provided to the device to increase its
utility and safety. Additional reinforcement for the device
is provided by ribs 102, 103 and 104. The ribs are metal
plates that support the housing during use, thereby protecting
the device and device components. All ribs are disposed in
the same plane as the motor to conserve space. More ribs may
be added to provide further reinforcement to the device. The
edges of the ribs are sealed with foam so that any liquid that
does enter the device will not contact the controller board,
power distribution board, motor controller, other electronics
and associated cables.
Further reinforcement is provided by hollow posts 105
integrally formed with the housing cover plates. The hollow
posts are open at one end where the threaded fasteners are
inserted to connect the cover plates to each other. (The
openings in the posts correspond to the holes 63 in Figures 3
and 4) Additional, internal mounting posts 106 are provided
to mount electronic systems and suspend them off the floor of ,
the device. Thus, the internal mounting posts help prevent
any liquids that enter the device from pooling on the
electronics. Still further reinforcement is provided by
gussets 107 mounted throughout the device housing. The
multiply redundant reinforcements and the tight-fitting
compartmentalized design of the device provide very high
protection against force, shock and vibration. The device
shown in Figures 2 through 7 can resist more than 1,200 pounds
of distributed force.
To protect the patient and users from accidental
activation, or activation when a belt is not secured to the
device, a means for sensing the presence of the belt is
provided. The drive spool slot 43 is provided with a pin 108
that is longitudinally translatable through the drive spool
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and the rotary encoder. The pin is attached to a spring that
urges the pin into the drive spool slot. When a belt spline
is inserted into the drive spool slot, the pin is pushed
through the drive spool and rotary encoder and towards a
contact switch 109. The contact switch is mounted on brace
110 that is itself mountea to the channel beam 41. The
contact switch is operably connected to the encoder controller
(and thereby to the processor). When the belt is inserted,
the pin is pushed against the contact switch and the device
thereby registers the presence and proper insertion of the
belt spline. To provide additional safety, the spline is
keyed to the drive spool slot so that movement of the pin
towards the contact switch is difficult unless the spline is
inserted into the slot. Other means for sensing the presence
of the belt may be used; for example, the drive spool slot may
be provided with an electrical contact that senses the
presence of the belt.
In addition, the spool shaft is provided with a detent
that locks the shaft in place when the spline is removed. The
detent holds the spool shaft at a particular position to aid
in insertion of the spline. Holding the spool shaft at a
particular position also maintains the relationship between
the actual physical position of the spool and the position of
the spool as measured by the control system. Thus, the
starting position of the spool shaft does not change while the
device is turned off. This, in turn, helps to maintain the
accuracy of measuring the actual amount of belt travel during
compressions.
The chest compression device is provided with a control
system that controls how the belt is wrapped around the drive
spool. For example, the drive spool is controlled so that
some of the belt is left wrapped around the drive spool
between compressions (that is, when the device has loosened
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the belt around the patient, just before beginning the next
compression). Preferably, a length of the belt corresponding
to one revolution of the drive spool is left wrapped around
the drive spool at all times during compressions. Thus, the
belt will maintain its curled shape, reduce the chance of
causing folds in the belt during compressions and increase the
efficiency of spooling the belt around the drive spool.
Figures 6 and 7 also show the location of the battery
compartment near the head of the patient. The location and
design of the battery pack and battery compartment allow for
rapid exchange of batteries. A spring in the back of the
compartment forces the battery pack out unless the battery
pack is fully and correctly inserted in the compartment.
Recesses 120 indicate the location of the springs inside the
battery compartment 121. Plastic grills 122 at the end of the
battery compartment reinforce the recesses.
To cool the device and tlie device electronics, a blower
123 is provided to circulate air inside the device. Outside
air is drawn in from either the left louvered vent 124 or the
superior louvered vent 125 and is expelled from the other
vent, thereby assisting in cooling the device components. (In
the devices shown in Figures 2 through 7, air is drawn in the
left vent and is blown out the superior vent.) The vents are
disposed in inwardly sloping recesses that are disposed in the
housing. The recesses help prevent liquids from entering the
vents.
Temperature inside the housing is measured with a
temperature sensor 127, such as a thermometer or thermistor,
mounted on the inside of the anterior cover plate. If the
temperature exceeds a pre-set temperature, then the processor
is programmed to control the systems of the device to cool the
device. For example, the processor may increase the speed of
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the blower, reduce motor speed or prompt the user to clear
blocked vents or move the patient and device to a cooler
location.
A means for measuring force is operably attached to the
device. The means for measuring force is operable to measure
the force the patient applies to the device and the force of
compressions. The means for measuring force is a load plate
128 attached to two load cells 129. Other means for sensing
force or weight may be used, such as one or more strain gauges
or springs operably attached to the channel beam. A load
plate cover 130, made from a high-density polyethylene
polymer, Santoprene rubber or similar materials, is also
provided to seal the inside of the device from liquids and
other contaminants.
A back-up battery may also be provided with the system to
provide power when the main batteries are not attached. The
back-up battery is mounted to a mounting plate 131 on the
channel beam 41. The mounting plate is a thickened region of
the channel beam itself, though the mounting plate may be a
separate component mounted to the channel beam.
Figure 8 shows an exploded view of part of the automatic
chest compression device 2, as seen from the anterior side 22
of the device. The device is shown in an orientation
corresponding to when the device is laying on the ground and
in use. The patient's head is placed on the headboard 20
portion of the anterior cover plate 60, the patient's torso is
placed on the load plate 128, the patient's back is placed on
the backboard 21 portion of the anterior cover plate 60 and
the patient's legs and buttocks extend past the handles 140 on
the inferior side of the device.
Figure 8 also shows the load cells 129 in relation to the
channel beam 41. The load cells are mounted to the channel
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beam by placing the load cells in load cell slots 141. The
load cells rest on shoulders 142 provided in the slots.
Bosses 143 disposed on the load cells contact the load plate
so that the load cells can measure the force applied to the
load plate 128. Thus, the load cells can measure the force
applied by the patient's thorax and the device to the load
cell, and this corresponds to the total compressive force
applied to the patient.
The load cells use a strain-based method to transduce
applied loads into an electrical signal. (Other load
measuring devices may be used, such as resistors, capacitors,
pneumatic actuators, piezoelectric actuators and other means
for measuring force or pressure.) The processor and software
control the operation of the device based on the load signal
generated by the load cells. For example, the device
determines how much force to apply based, in part, on the
weight of the patient on the load plate. The device also
monitors the force of compressions and prevents excessive
force from being applied to the patient. An excessive
compressive force is between about 600 pounds to about 1000
pounds (over the entire area of the load distribution
sections), depending on the patient and the embodiment used.
Figure 9 illustrates a method of performing chest
compressions on a patient 1. The patient's head 156 rests on
the headboard 20 between the loops 176, the patient's chest
157 rests over the load plate 128, the lumbar poi-Lion of the
patient's back 158 rests over the backboard 21 of the housing
and the patient's hips and legs extend past the inferior
handles 140 (the hips and legs rest on the ground, gurney or
other surface while the device is in use). The belt 3 extends
from the drive spool 42, around the spindles 30 and 31 and
over the patient's chest. In use, the drive spool tightens
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the belt as the motor turns the drive spool, thereby
compressing the patient's chest.
As shown in Figure 9, the backboard portion 21 of the
device is provided with an ergonomic shape for both the
patient and the device operator. The patient's head can be
easily tilted, as recommended by current AHA guidelines. The
design also allows easy endotracheal intubation and
visualization during endotracheal intubation. The backboard
design also allows for safe and easy immobilization of the
patient's head, torso and hips. The backboard also is shaped
to reduce back strain on the patient. Specifically, the
backboard portion of the housing slopes toward the ground
toward the inferior end of the belt drive platform. The
device thereby accommodates the lumbar curve in the patient's
back when the patient rests on the backboard.
Referring again to Figure 2, the device is provided with
a number of additional features to make it user-friendly and
durable. A plurality of ergonomic handles 140 are provided to
allow a user to carry the device in several different
orientations, or to allow multiple people to carry the device
when a patient is laying on the housing. The sides of the
device are shaped so that the top of the device gently slopes
towards the bottom of the device. (In other words, the
anterior portion of the left and right sides of the device
gently curves towards the posterior portion of the left and
right sides of the device.) Thus, the handles 140 and air
vents 124 and 125 are raised slightly from the ground when the
device is placed on the ground. This shape helps to prevent
liquids from entering the louvered vents. The shape also
allows a user to more easily lay the device on the ground
without scraping his or her fingers and to more easily lift or
shift the position of the device. In addition, the shape also
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makes it easier to laterally roll the patient over the side of
the device.
A user interface 159 is placed near the patient's head on
the left side of the device to allow a rescuer to easily
interact with the device during use and to reduce interference
from a patient's clothes or body parts. The user interface is
provided with color-coded switches or buttons 160 for ease of
use. (The preferred embodiment uses membrane-type buttons
with a low profile or a touch screen.) The user interface is
recessed into the housing to reduce inadvertent activation of
buttons or other interfaces. The user interface is also
covered with a plastic cover 161 to prevent liquids from
damaging the interface. One or more slots 162 are placed in
the user interface recess so that liquids can drain out of the
recess.
Also shown in Figure 2 are bumpers 40 that are attached
to the ears 163 and to the sides of the device. The bumpers
provide further protection against shock and vibration. The
bumpers also help prevent the device from slipping when the
device is leaned against walls or other objects. The bumpers
on the ears are thicker than the bumpers on the other portions
of the device. All of the bumpers are made from a
thermoplastic elastomer compound, such as Dynaflexm' produced
by GLS Corporation, although rubber and other elastomeric
materials may be used. Preferably the bumpers are shaped,
sized and dimensioned to fit between the housing cover plates
so that the bumpers also serve as gaskets. Additional gaskets
are provided to further seal the device. The entire perimeter
of the device, including the edges of the spindles and the
channel beam, is sealed by a combination of gaskets, adhesives
and compressed rubber seals.
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A left niche 173 and a right niche 174 are provided in
the, left side 26 and right side 27 of the housing,
respectively, between the ears and the handles. The niches
allow additional straps to be secured to the device. In
addition data port 175 is disposed on the edge of the housing,
tucked into one or both niches. The data port allows the
device to communicate with other devices or processors. The
data port may be an infrared port, Bluetooth port, Ethernet
cable, phone jack, USB port, wireless transmitter or any other
suitable means for transferring data. (The data port may be
disposed elsewhere on the device.)
Figures 2 and 9 also shows a number of flexible loops 176
that are attached to the headboard portion of the housing.
The flexible loops are metal cables coated with plastic. A
head restraining strap, or other head restraint, may be
threaded through or attached to the loops and placed around
the patient's head or shoulders. The head restraint secures
the patient's head to the device during treatment and
transport. (The flexible loops may be replaced with some
other means for securing the patient's head to the device such
as a built-in head restraint frame.)
A plurality of tie-downs 177 are also provided to serve
as objects around which straps or other restraints may be
placed. (Thus, the device may be easily secured to a gurney
or bed, or the device may be easily secured to the patient for
transport.) The tie-downs are mounted to the handles 140 and
within the niches 173 and 174. The tie-downs may be made
rotatable within the housing so that the tie-downs may act as
spindles for straps disposed around the tie-downs. The tie-
downs also serve as reinforcements for the handles.
All of the fasteners used to secure the various
components of the device are disposed either within the device
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or on the posterior side of the housing (the bottom of the
device when in use). The fasteners are also set into the
housing in holes so that no fasteners will catch on clothing
or other objects. The fasteners are all plastic to prevent
electrical currents from flowing between the inside and the
outside of the device. Moreover, fluids spilled on the
anterior side of the device will not accumulate in fastener
holes, thereby making the device more resistant to fluids.
(The threaded fasteners may be replaced with latches or snap
latches to increase the ease of opening the device.)
Referring again to Figures 3 and 4, the device is
provided with more features to increase its utility. A
battery compartment 121 disposed inside the superior end of
the device holds one or more batteries designed to fit within
the compartment. Pinned electrical connectors in the battery
compartment electrically connect the batteries to the device.
The electrical connectors are provided with foam seals or
gaskets that are compressed when a battery is connected to the
device. The foam seals seal the electrical connection from
liquids.
The floor of the compartment (on the inside of the
superior cover plate) is provided with a notch, boss or detent
that receives a corresponding spring latch on the rectangular
battery pack. Thus, a battery pack audibly snaps into place
when secured in the battery compartment.
The battery compartment, or the opening to the
compartment, is shaped to match specific battery packs. Thus,
batteries not designed to work with the device may not be
inserted into the compartment or used with the device.
Likewise, the shape of the compartment ensures that the
battery pack is correctly inserted. Alignment ridges 183
disposed in the compartment further aid in aligning and
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inserting battery packs. In addition, flexible metal strips
may be disposed between rails 184 mounted in the roof of the
compartment (on the inside of the anterior cover plate). The
metal strips are bent slightly away from the rails. The metal
strips impart a force to a battery pack that urges a pack
towards the floor of the compartment. Thus, the rails help to
secure the battery pack within the compartment and help to
align the battery with the electrical connector as the battery
slides in.
The battery compartment 121 is sealed from liquids and
other contaminants by the battery compartment cover plate 185.
A gasket or seal may be provided between the compartment cover
plate and the housing to further prevent entry by liquids.
To indicate battery status, the device or the battery
pack (or both) may be provided with a means for displaying
battery status that is operably attached to a means for
determining battery status. For example, an LED can be added
to a battery pack to indicate the status of the batteries, or
the processor can be programmed to display battery status on
the display.
A power switch 186 is disposed on the superior side of
the device and is recessed into the housing to help prevent
inadvertent activation. The power switch is a button
protected by a flexible, waterproof cover, though a flip-
switch or other means for activating and deactivating the
device can be used. The power switch may be disposed
elsewhere on the housing.
Protection from electric shocks or surges is provided by
the channel beam, which serves as a grounding element. In
addition, a thin, metallic coating on the inside of the
enclosure is connected to the channel beam. The metallic
coating conducts stray electrical currents to the channel beam
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and grounds them. The coating also limits electromagnetic
emissions from the device, thereby protecting patients with
pacemakers or other electrical medical equipment. The housing
is also made from a non-conducting material to further improve
electrical insulation. Other forms of electrical insulation
or protection may also be provided to the device.
Additional safety features may be added to the device;
for example, the device can be designed so that the device
will not operate without a key. Likewise, multiple motions
may be required to activate certain functions; for example, a
twisting and pushing motion may be required to activate and
deactivate the device. Alternatively, two or more buttons,
possibly operated in a particular sequence, may be required to
activate the device. Moreover, the device can provide
different users with different levels of access to device
functions depending on the training of the user. Examples of
tiered access emergency devices are found in our U.S. Patent
6,398,744.
The processor is also capable of monitoring the status of
the device and taking appropriate action depending on certain
events. For example, the device can call 911 or a central
operating center when the device is activated. The device may
also inform a customer or a manufacturer when the batteries
are running low or when the batteries have reached the end of
their service life. Examples of device monitoring may be
found in our U.S. Patent 6,142,962.
Figure 10 shows an exploded view of some of the internal
components of the device (also shown in Figure 7). The
display and processor unit 83; ribs 102, 103, and 104; blower
123; drive spool 42, motor 79, clutch 80, gearbox 81 and brake
82; part of the channel beam 41, the left spindle 30 and the
right spindle 31; and the central rib 102 and motor controller
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84 are separated to show the air path around the drive train.
The motor, brake and electronics all produce excess heat that
can cause the device to malfunction or be permanently damaged.
Excess heat may also harm the patient or rescuers if the
device overheats. Thus, cooling mechanisms are needed to
provide a means for removing heat from the device.
One means for removing heat is to circulate outside air
throughout the device and to force heated air out of the
device. As described in reference to Figures 6 and 7, the
blower draws outside air from one vent and through the top of
the blower. The blower then expels air through opening 187 in
rib 104 and into the device. Air circulates in the device and
is ultimately expelled from the other vent. (Airflow may be
reversed, so that the blower blows air from inside the device
to outside the device). The blower itself is a ComAir/Rotron
Model WT12B3-E2, 12-volt blower. Although any suitable
blower, fan or other cooling device of similar capacity may be
used, a blower is preferable since it is more compact than a
fan and generates less electromagnetic noise than a fan.
To increase the effectiveness of air-cooling, the device
Is structured so that airflow is directed along the drive
train (the drive spool 42, motor 79, clutch 80, gearbox 81 and
brake 82). Specifically, the ribs 102, 103 and 104 serve as
guides for airflow around the drive train. The ribs are
narrowly spaced from the drive train to generate higher air
velocity and hence greater convective cooling. The path of
airflow along the drive train of the devices shown in the
Figures is represented by arrows 188. Generally, air flows
between the drive train and the ribs, but air does flow both
over and under the gearbox, clutch and motor. In addition,
the ribs form compartments in the device that allow air to
flow over or under all of the heat-producing or heat-sensitive
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internal components of the device, such as the processor,
power controller, and other components.
Additional cooling is provided by mounting a metal foil
on the inside surface of the anterior cover plate (any number
of metals can be used, such as copper, steel and others). The
metal foil extends from the channel beam to the superior end
of the device and across the lateral width of the device. The
metal foil absorbs heat produced by the motor and distributes
the heat over a broad area, thereby increasing heat
dissipation. (The metal foil also reflects infrared radiation
back into the device to prevent the outside of the device from
overheating the patient.) Furthermore, a layer of insulation
is added between the anterior cover plate and the metal foil
in the region of the brake and motor. The insulation reduces
the rate of heat transfer to the anterior cover plate, and
hence the patient. In addition, the motor, brake, electronics
and other heat-producing components of the device are
separated from the metal sheet and the outer surfaces of the
device by an air-filled space. The space prevents direct heat
conduction and further reduces the rate of heat transfer to
the outer surfaces of the device and to the patient.
Additional cooling is provided by heat sinks 189 disposed
on the motor, ribs and other components of the system. The
heat sinks increase the surface area of these components,
thereby allowing more heat to dissipate into the surrounding
air flow. In addition, the motor, brake, gearbox and clutch
are physically thermally connected. The physical thermal
connections serve as additional heat sinks for these heat-
producing devices. Additional heat sinks are provided in the
form of braces 190 provided on the central rib 102. The
braces both hold the motor controller 84 and provide a
physical thermal connection between the motor controller and
the central rib. The central rib thereby acts as a heat sink
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for the motor controller. Other connections throughout the
device provide for additional heat sinks to further increase
the ability to remove excess heat.
Temperature is measured with a temperature sensor, such
as a thermometer or thermistor, mounted on the inside of the
anterior cover plate (and near to the patient during use).
The temperature sensor thereby monitors temperature in a
location slightly warmer than the surface directly contacting
the patient, meaning that potential patient overheating is
detected early. (The body temperature of the patient May also
be measured and tracked by the system with a separate sensor.)
As described in reference to Figure 7, if the temperature
exceeds a pre-set temperature, then the processor is
programmed to control the device to cool the device or patient
or to prompt the user to take steps to cool the device or
patient.
The device housing is made from a material having a low
thermal conductivity, thereby reducing the chances that the
patient overheats and also reducing the effect of leaving the
device near a heat source or out in the Sun. In addition,
other heat dissipation mechanisms may be added to the device
to further cool the device during operation, such as
radiators, thermoelectric cooling devices or spray/drip
devices. Thus, while the preferred embodiments of the devices
and methods have been described in reference to the
environment in which they were developed, they are merely
illustrative of the principles of the inventions. Other
embodiments and configurations may be devised without
departing from the spirit of the inventions and the scope of
the appended claims.
The device may be made larger so that the entire patient
rests on the device, or the housing may be provided with a
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telescoping plate that extends outwardly from the device. The
telescoping plate allows the patient's legs to rest on the
device when in transport, yet allows the device to be more
portable when not in use. (The plate need not be telescoping,
but may be connected to the rest of the housing by hinges or
other suitable means for connecting the plate to the rest of
the housing.) Similarly, the device may be provided with
storage compartments to house additional equipment, such as
gloves, respirators, ECG monitors, blood pressure monitors,
pulse oximeters, pulse detectors, end-tidal carbon dioxide
monitors, defibrillators or other emergency equipment.
In addition, one or more kickstands or braces can be
added to the device. If the device must be operated on an
uneven surface, the kickstands or braces stabilize the device
during use. Thus, while the preferred embodiments of the.
devices and methods have been described in reference to the
environment in which they were developed, they are merely
illustrative of the principles of the inventions. Other
embodiments and configurations may be devised without
departing from the scope of
the appended claims.
=
29
