U.S. patent application number 11/942132 was filed with the patent office on 2008-03-20 for integrated resuscitation.
This patent application is currently assigned to ZOLL Medical Corporation. Invention is credited to Gary A. Freeman.
Application Number | 20080071316 11/942132 |
Document ID | / |
Family ID | 23980487 |
Filed Date | 2008-03-20 |
United States Patent
Application |
20080071316 |
Kind Code |
A1 |
Freeman; Gary A. |
March 20, 2008 |
Integrated Resuscitation
Abstract
A resuscitation system that includes at least two defibrillation
electrodes configured to be applied to the exterior of the chest of
a patient for delivering a defibrillation shock, a source of one or
more ECG signals from the patient, a defibrillation circuit for
delivering a defibrillation shock to the defibrillation electrodes,
a control box that receives and processes the ECG signals to
determine whether a defibrillation shock should be delivered or
whether CPR should be performed, and that issues instructions to
the user either to deliver a defibrillation shock or to perform
CPR, wherein the determination of whether CPR should be performed
and the instructions to perform CPR can occur at substantially any
point during a rescue.
Inventors: |
Freeman; Gary A.; (Newton
Centre, MA) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
ZOLL Medical Corporation
|
Family ID: |
23980487 |
Appl. No.: |
11/942132 |
Filed: |
November 19, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10804312 |
Mar 18, 2004 |
7310553 |
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11942132 |
Nov 19, 2007 |
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09794320 |
Feb 27, 2001 |
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10804312 |
Mar 18, 2004 |
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09498306 |
Feb 4, 2000 |
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09794320 |
Feb 27, 2001 |
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PCT/US01/03781 |
Feb 5, 2001 |
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09794320 |
Feb 27, 2001 |
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Current U.S.
Class: |
607/5 ;
601/41 |
Current CPC
Class: |
A61H 31/007 20130101;
A61H 2230/207 20130101; A61H 2031/002 20130101; A61N 1/3987
20130101; A61N 1/39044 20170801; A61H 31/004 20130101; A61N 1/0492
20130101; A61H 2201/10 20130101; A61H 2201/5061 20130101; A61N
1/3993 20130101; A61N 1/3925 20130101; A61H 2201/5084 20130101;
A61N 1/046 20130101; A61H 2201/5048 20130101; A61H 2201/5043
20130101; A61H 31/005 20130101; A61H 2201/5007 20130101 |
Class at
Publication: |
607/005 ;
601/041 |
International
Class: |
A61N 1/04 20060101
A61N001/04; A61H 31/00 20060101 A61H031/00 |
Claims
1. A resuscitation system comprising: at least two defibrillation
electrodes configured to be applied to the exterior of the chest of
a patient for delivering a defibrillation shock; a source of one or
more ECG signals from the patient; a defibrillation circuit for
delivering a defibrillation shock to the defibrillation electrodes;
a control box that receives and processes the ECG signals to
determine whether a defibrillation shock should be delivered or
whether CPR should be preformed, and that issues instructions to
the user either to deliver a defibrillation shock or to perform
CPR; wherein the determination of whether CPR should be performed
and the instructions to perform CPR can occur at substantially any
point during a rescue.
2. The system of claim 1 wherein the control box includes a user
operable control for initiating delivery of a defibrillation shock,
and the instructions to deliver a defibrillation shock include
instructions to activate the user operable control.
3. The system of claim 2 wherein the user operable control is a
button configured to be pushed by the user.
4. The system of claim 1 wherein the determination of whether CPR
should be performed and the instructions to perform CPR can occur
before a determination to deliver any defibrillation shock.
5. The system of claim 1 wherein the source of the ECG signals is
the defibrillation electrodes.
6. The system of claim 1 wherein the defibrillation circuit is
contained in the control box.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
U.S. application Ser. No. 10/804,312, filed on Mar. 18, 2004, which
is a continuation of and claims priority to U.S. application Ser.
No. 09/794,320, filed on Feb. 27, 2001 (now abandoned), which is a
continuation-in-part of and claims priority to U.S. application
Ser. No. 09/498,306, filed on Feb. 4, 2000 (now abandoned), and PCT
Application Serial No. PCT/US01/03781, filed on Feb. 5, 2001.
BACKGROUND OF THE INVENTION
[0002] This invention relates to integrated resuscitation systems
incorporating defibrillation and cardio-pulmonary resuscitation
(CPR) prompts.
[0003] Resuscitation can generally include clearing a patient's
airway, assisting the patient's breathing, chest compressions, and
defibrillation.
[0004] The American Heart Association's Basic Life Support for
Health Care Providers textbook provides a flow chart at page 4-14
of Chapter 4 that lists the steps of airway clearing, breathing,
and circulation (known as A, B, and C), for situations in which
there is no defibrillator readily accessible to the rescuer.
[0005] Defibrillation (sometimes known as step D) can be performed
with the use of an automatic external defibrillator (AED). Most
automatic external defibrillators are actually semi-automatic
external defibrillators (SAED), which require a clinician to press
a start button, after which the defibrillator analyzes the
patient's condition and provides a shock to the patient if the
electrical rhythm is shockable and waits for user intervention
before any subsequent shock. Fully automatic external
defibrillators, on the other hand, do not wait for user
intervention before applying subsequent shocks. As used below,
automatic external defibrillators (AED) include semi-automatic
external defibrillators (SAED).
[0006] Both types of defibrillators typically provide an oral stand
clear warning before the application of each shock, and then the
clinician is expected to stand clear of the patient and may be
required to press a button indicating that the clinician is
standing clear of the patient. The controls for automatic external
defibrillators are typically located on a resuscitation control
box.
[0007] AEDs are used typically by trained providers such as
physicians, nurses, fire department personnel, and police officers.
There might be one or two people at a given facility that has an
AED who have been designated for defibrillation resuscitation
before an ambulance service arrives. The availability of on-site
AEDs along with rescuers trained to operate them is important
because if the patient experiences a delay of more than 4 minutes
before receiving a defibrillation shock the patient's chance of
survival can drop dramatically. Many large cities and rural areas
have low survival rates for defibrillation because the ambulance
response time is slow, although many suburbs have higher survival
rates because of the faster ambulance response time due to lack of
traffic and availability of hospitals and advanced life
support.
[0008] Trained lay providers are a new group of AED operators, but
they rarely have opportunities to defibrillate. For example,
spouses of heart attack victims may become lay providers, but these
lay providers can be easily intimidated by an AED during a medical
emergency. Consequently, such lay providers can be reluctant to
purchase AEDs, or might tend to wait for an ambulance to arrive
rather than use an available AED, out of concern that the lay
provider might do something wrong.
[0009] There are many different kinds of heart rhythms, some of
which are considered shockable and some of them are not. For
example, a normal rhythm is considered non-shockable, and there are
also many abnormal non-shockable rhythms. There are also some
abnormal non-viable non-shockable, which means that the patient
cannot remain alive with the rhythm, but yet applying shocks will
not help convert the rhythm.
[0010] As an example of a non-shockable rhythm, if a patient
experiences asystole, the heart will not be beating and application
of shocks will be ineffective. Pacing is recommended for asystole,
and there are other things that an advanced life support team can
do to assist such patient, such as the use of drugs. The job of the
first responder is simply to keep the patient alive, through the
use of CPR and possibly defibrillation, until an advanced life
support team arrives. Bradycardias, during which the heart beats
too slowly, are non-shockable and also possibly non-viable. If the
patient is unconscious during bradycardia, it can be helpful to
perform chest compressions until pacing becomes available.
Electro-mechanical dissociation (EMD), in which there is electrical
activity in the heart but it is not making the heart muscle
contract, is non-shockable and non-viable, and would require CPR as
a first response. Idio-ventricular rhythms, in which the normal
electrical activity occurs in the ventricles but not the atria, can
also be non-shockable and non-viable (usually, abnormal electrical
patterns begin in the atria). Idio-ventricular rhythms typically
result in slow heart rhythms of 30 or 40 beats per minute, often
causing the patient to lose consciousness. The slow heart rhythm
occurs because the ventricles ordinarily respond to the activity of
the atria, but when the atria stop their electrical activity, a
slower, backup rhythm occurs in the ventricles.
[0011] The primary examples of shockable rhythms, for which a first
responder should perform defibrillation, include ventricular
fibrillation, ventricular tachycardia, and ventricular flutter.
[0012] After using a defibrillator to apply one or more shocks to a
patient who has a shockable electrical rhythm, the patient may
nevertheless remain unconscious, in a shockable or non-shockable
rhythm. The rescuer may then resort to chest compressions. As long
as the patient remains unconscious, the rescuer can alternate
between use of the defibrillator (for analyzing the electrical
rhythm and possibly applying a shock) and performing
cardio-pulmonary resuscitation (CPR).
[0013] CPR generally involves a repeating pattern of five or
fifteen chest compressions followed by a pause. CPR is generally
ineffective against abnormal rhythms, but it does keep some level
of blood flow going to the patient's vital organs until an advanced
life support team arrives. It is difficult to perform CPR over an
extended period of time. Certain studies have shown that over a
course of minutes, rescuers tend to perform chest compressions with
less-than-sufficient strength to cause an adequate supply of blood
to flow to the brain. CPR prompting devices can assist a rescuer by
prompting each chest compression and breath.
[0014] PCT Patent Publication No. WO 99/24114, filed by
Heartstream, Inc., discloses an external defibrillator having PCR
and ACLS (advanced cardiac life support) prompts.
SUMMARY OF THE INVENTION
[0015] One aspect of the invention features a resuscitation system
comprising at least two defibrillation electrodes configured to be
applied to the exterior of the chest of a patient for delivering a
defibrillation shock; a source of one or more ECG signals from the
patient; a defibrillation circuit for delivering a defibrillation
shock to the defibrillation electrodes; a control box that receives
and processes the ECG signals to determine whether a defibrillation
shock should be delivered or whether CPR should be performed, and
that issues instructions to the user either to deliver a
defibrillation shock or to perform CPR, wherein the determination
of whether CPR should be performed and the instructions to perform
CPR can occur at substantially any point during a rescue.
[0016] In preferred implementations, one or more of the following
features are incorporated. The control box includes a user operable
control for initiating delivery of a defibrillation shock, and the
instructions to deliver a defibrillation shock include instructions
to activate the user operable control. The user operable control is
a button configured to be pushed by the user. The determination of
whether CPR should be performed and the instructions to perform CPR
can occur before a determination to deliver any defibrillation
shock. The source of the ECG signals is the defibrillation
electrodes. The defibrillation circuit is contained in the control
box.
[0017] Numerous other features and advantages of the invention will
be apparent from the detailed description and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a drawing of a defibrillation electrode pad
according to the invention, positioned over the chest of a
patient.
[0019] FIG. 2 is a view of the front display panel of a
resuscitation control box according to the invention that houses
electronic circuitry and provides audible and visual prompting.
[0020] FIG. 3 is a cross-sectional drawing of the defibrillation
electrode pad of FIG. 1 taken along line 3-3.
[0021] FIG. 4 is a cross-sectional drawing of the defibrillation
pad of FIG. 1 taken along line 4-4.
[0022] FIG. 5 is a circuit diagram illustrating the circuit
interconnections between the defibrillation electrode pad of FIG. 1
and the resuscitation control box of FIG. 2.
[0023] FIGS. 6A and 6B are a flowchart illustrating the initial
routine of a resuscitation system according to the invention.
[0024] FIGS. 7A, 7B, and 7C are a flowchart illustrating the
"circulation help" routine of the resuscitation system.
[0025] FIG. 8 is a flowchart illustrating the "breathing help"
routine of the resuscitation system.
[0026] FIGS. 9A and 9B are a flowchart illustrating the "airway
help" routine of the resuscitation system.
DETAILED DESCRIPTION
[0027] The defibrillation and CPR assembly according to the
invention combines traditional AED (automatic external
defibrillation) functions with CPR prompting, and thus transforms a
defibrillator into a resuscitation device that combines prompts for
clearing a patient's airway, breathing, chest compression, and
defibrillation. Thus, the combined defibrillation and CPR assembly
combines all of these aspects of resuscitation into a single
protocol.
[0028] With reference to FIG. 1, a defibrillation electrode pad 10,
which includes high-voltage apex defibrillation electrode 12 and
high-voltage sternum defibrillation electrode 14, is placed on the
patient's chest 16 and includes a region 18 on which a user may
press to perform CPR. Legends on pad 10 indicate proper placement
of the pad with respect to the patient's collarbones and the chest
centerline and the proper placement of the heel of the rescuer's
hand.
[0029] A low-profile button panel 20 is provided on the electrode
assembly. Button panel 20 has buttons 22, including buttons A
(Airway Help), B (Breathing Help), C (Circulation Help) and PAUSE,
and may also include adjacent light emitting diodes (LEDs) 24 that
indicate which button has been most recently pressed. Button panel
20 is connected by a cable 23 to a remote resuscitation control box
26, shown in FIG. 2. Button panel 20 provides rigid support
underneath buttons A, B, C, and PAUSE against which the switches
can be pushed in order to ensure good switch closure while the
electrode rests on a patient. Button panel 20 includes components
that make electrical contact with silver/silver-chloride electrical
circuit components screen-printed on a polyester base of
defibrillation electrode pad 10, as is described in detail
below.
[0030] A pulse detection system based on shining light through the
patient's vascular bed, e.g., a pulse oximetry system 52, is
incorporated into defibrillation electrode pad 10. Pulse oximetry
system 52 includes a red light-emitting diode, a near-infrared
light-emitting diode, and a photodetector diode (see FIG. 5)
incorporated into defibrillation electrode pad 10 in a manner so as
to contact the surface of the patient's chest 16. The red and
near-infrared light-emitting diodes emit light at two different
wavelengths, which is diffusely scattered through the patient's
tissue and detected by the photodetector diode. The information
obtained from the photodetector diode can be used to determine
whether the patient's blood is oxygenated, according to known
noninvasive optical monitoring techniques.
[0031] In an alternative embodiment, the pulse detection system is
a phonocardiogram system for listening to the sound of the victim's
heart, rather than a pulse oximetry system. The phonocardiogram
system includes a microphone and an amplifier incorporated within
the electrode pad. Because a heart sound can be confused with
microphone noise, the signal processing that must be performed by
the microprocessor inside the control box will be more difficult in
connection with a phonocardiogram system than in connection with a
pulse oximetry system. Nevertheless, there are programs available
that call enable the microprocessor to determine whether an ECG
signal is present as opposed to microphone noise.
[0032] Pulse oximetry is a well-developed, established technology,
but it requires good contact between the light sources and the
victim's skin so that light can shine down into the victim's
vascular bed. Many victims have lots of chest hair, which can
interfere with good contact. It may be desirable for different
types of electrode pads to be available at a given location (one
having a pulse oximetry system and one having a phonocardiogram
system) so that a rescuer can select an appropriate electrode pad
depending on the nature of the victim.
[0033] In an alternative embodiment, instead of providing a
low-profile button panel, a button housing can be provided that is
affixed to an edge of the defibrillation electrode. The housing may
be in the form of a clamshell formed of single molded plastic
element having a hinge at an edge of the clamshell around which the
plastic bends. The two halves of the clamshell can be snapped
together around the electrode assembly.
[0034] The resuscitation control box (FIG. 2) includes an internal
charge storage capacitor and associated circuitry including a
microprocessor, an further includes off/on dial 28, and a "READY"
button 30 that the rescuer presses immediately prior to application
of a defibrillation shock in order to ensure that the rescuer is
not in physical contact with the patient. The microprocessor may be
a RISC processor such as a Hitachi SH-3, which can interface well
with displays and keyboards, or more generally a processor capable
of handling DSP-type (digital signal processing) operations.
[0035] The resuscitation control box has printed instructions 32 on
its front face listing the basic steps A, B, and C for
resuscitating a patient and giving basic instructions for
positioning the defibrillation electrode pad on the patient. A
speaker orally prompts the user to perform various steps, as is
described in detail below.
[0036] For example, the resuscitation control box instructs the
user, by audible instructions and also through a display 34 on the
resuscitation control box, to check the patient's airway and
perform mouth-to-mouth resuscitation, and if the patient's airway
is still blocked, to press the A (Airway Help) button on the button
panel (FIG. 1), upon which the resuscitation control box gives
detailed prompts for clearing the patient's airway. If the
patient's airway is clear and the patient has a pulse but the
patient does not breathe after initial mouth-to-mouth
resuscitation, the resuscitation control box instructs the user
press the B (Breathing Help) button, upon which the resuscitation
control box gives detailed mouth-to-mouth resuscitation prompts.
If, during the detailed mouth-to-mouth resuscitation procedure, the
rescuer checks the patient's pulse and discovers that the patient
has no pulse, the resuscitation control box instructs the user to
press the C (Circulation Help) button.
[0037] During the circulation procedure, the resuscitation control
box receives electrical signals from the defibrillation electrodes
and determines whether defibrillation or CPR should be performed.
If the resuscitation control box determines that defibrillation is
desirable, the resuscitation control box instructs the user to
press the "ready" button on the resuscitation control box and to
stand clear of the patient. After a short pause, the resuscitation
control box causes a defibrillation pulse to be applied between the
electrodes. If at any point the resuscitation control box
determines, based on the electrical signals received from the
electrodes, that CPR is desirable, it will instruct the user to
perform CPR.
[0038] Thus, the key controls for the system are on the electrodes
attached to the patient rather than the resuscitation control box.
This is important because it enables the rescuer to remain focused
on the patient rather than the control box. The resuscitation
control box gets its information directly from the electrodes and
the controls on the electrodes.
[0039] The resuscitation control box can sense electrical signals
from the patient's body during pauses between CPR compressions.
Also, as is described below, a compression-sensing element such as
an accelerometer or a force-sensing element is provided in the
region of the defibrillation electrode pad on which the user
presses to perform CPR. The purpose of the compression-sensing or
force-sensing element is to allow the resuscitation control box to
prompt the user to apply additional compression or force, or to
prompt the user to cease CPR if the user is performing CPR at an
inappropriate point in time.
[0040] Referring to FIG. 4, according to one embodiment of the
invention, each electrode 12, 14 (only electrode 12 is shown) of
defibrillation electrode pad 10 includes a polymer-based ink
containing a silver/silver-chloride suspension, which is
screen-printed on a polyester or plastic base 36. The ink is used
to carry the defibrillation current. The screen-printing process
first involves applying a resist layer to the polyester base 36.
The resist layer is basically a loose mesh of nylon or the like, in
which the holes have been filled in at some locations in the mesh.
Then, the silver/silver-chloride ink is applied as a paste through
the resist layer in a squeegee-like manner. The ink squeezes
through the screen and becomes a solid layer. The ink may then be
cured or dried. The silver/silver-chloride ink provides good
conductivity and good monitoring capabilities.
[0041] Thus, the ink can be applied as pattern, as opposed to a
solid sheet covering the entire polyester base. For example, U.S.
Pat. No. 5,330,526 describes an electrode in which the conductive
portion has a scalloped or daisy shape that increases the
circumference of the conductive portion and reduces burning of the
patient. A conductive adhesive gel 38 covers the exposed surface of
each electrode.
[0042] In addition, electrical circuit components are also be
screen printed on the base, in the same manner as flat circuit
components of membrane-covered, laminated panel controls.
[0043] Referring to FIG. 3, a rigid piece 40 of hard plastic, such
as PVC or polycarbonate, is laminated beneath substrate 36 and
supports buttons A, B, C, and PAUSE. The rigid plastic piece 40 is
glued onto substrate 36. Buttons A, B, C, and PAUSE consist of
small metal dome snap-action switches that make contact between an
upper conductive ink trace 42 and lower conductive ink traces 44,
46, 48, and 50. Buttons A, B, C, and PAUSE serve as controls that
can be activated by the user that are physically located either on
or immediately adjacent to the electrode assembly itself. Each of
buttons A, B, C, and PAUSE may be associated with an adjacent
light-emitting diode (LED). For example, LEDs may be glued, using
conductive epoxy, onto silver/silver-chloride traces on substrate
36. An embossed polyester laminate layer 54 covers conductive ink
trace 42 of buttons A, B, C, and PAUSE, and a foam layer 56 is
laminated beneath rigid plastic piece 40.
[0044] Referring again to FIG. 4, defibrillation electrode pad 10
includes an extension piece that is placed directly over the
location on the patient's body where the rescuer performs chest
compressions. This extension piece includes substrate 36, and a
semi-rigid plastic supporting member 58 laminated underneath
substrate 36 that covers the chest compression area. Semi-rigid
supporting member 58 provides somewhat less rigidity than rigid
plastic piece 40 provided at the location of buttons A, B, C, and
PAUSE (illustrated in FIG. 3).
[0045] In embodiments having a force-sensing element, a polyester
laminate 60, and a force-sensing resistor having two layers of
carbon-plated material 62 and 64, are laminated between polyester
substrate 36 and semi-rigid supporting member 58. A suitable
construction of the force-sensing resistor is illustrated in the
FSR Integration Guide & Evaluation Parts Catalog with Suggested
Electrical Interfaces, from Interlink Electronics. The electrical
contact between the two carbon-plated layers of material increases
with increased pressure, and the layers of force-sensing resistive
material can provide a generally linear relationship between
resistance and force. Conductive ink traces 66 and 68 provide
electrical connections to the two layers of the force-sensing
resistor.
[0046] During chest compressions, the rescuer's hands are placed
over the extension piece, and the force-sensing resistor of the
extension piece is used to sense the force and the timing of the
chest compressions. The force-sensing resistor provides information
to the resuscitation control box so that the resuscitation control
box can provide the rescuer with feedback if the rescuer is
applying insufficient force. The resuscitation control box also
provides coaching as to the rate at which CPR is performed. In
certain situations, the resuscitation control box indicates to the
rescuer that CPR should be halted because it is being performed at
an inappropriate time, such as immediately prior to application of
a defibrillation shock when the rescuer's hands should not be
touching the patient, in which case the resuscitation control box
will also indicate that the rescuer should stay clear of the
patient because the patient is going to experience a defibrillation
shock.
[0047] As is noted above, during CPR the rescuer pushes on the
patient's chest through the extension piece in the vicinity of the
electrodes. If the resuscitation control box were to perform
analysis during the chest compressions, the chest compressions
would be likely to affect the sensed electrical rhythm. Instead,
during the pauses between sets of compressions (for example, the
pause after every fifth chest compression), the resuscitation
control box can perform an electrocardiogram (ECG) analysis. The
resuscitation control box might discover, for example, that the
patient who is undergoing CPR is experiencing a non-shockable
rhythm such as bradycardia, in which case the CPR is required in
order to keep the patient alive, but then the resuscitation control
box may discover that the rhythm has changed to ventricular
fibrillation in the midst of CPR, in which case the resuscitation
control box would instruct the rescuer to stop performing CPR so as
to allow the resuscitation control box to perform more analysis and
possibly apply one or more shocks to the patient. Thus, the
invention integrates the rescuer into a sophisticated scheme that
allows complex combinations of therapy.
[0048] In an alternative embodiment, a compression-sensing element
such as an accelerometer may be used in place of a force-sensing
element. The accelerometer, such as a solid-state ADXL202
accelerometer, is positioned at the location where the rescuer
performs chest compressions. In this embodiment, the microprocessor
obtains acceleration readings from the accelerometer at fixed time
intervals such as one-millisecond intervals, and the microprocessor
integrates the acceleration readings to provide a measurement of
chest compression. The use of an accelerometer is based on the
discovery that it is more important to measure how deeply the
rescuer is compressing the chest than to measure how hard the
rescuer is pressing. In fact, every victim's chest will have a
different compliance, and it is important that the chest be
compressed about an inch and a half to two inches in a normal sized
adult regardless of the victim's chest compliance.
[0049] FIG. 5 is a circuit diagram illustrating the circuit
interconnections between the defibrillation electrode pad of FIG. 1
through the cable to the resuscitation control box or FIG. 2.
Sternum electrode 14 is connected to HV+ at the resuscitation
control box, and apex electrode 12 is connected to HV-. A ground
GND is connected to the upper conductive ink trace of buttons A, B,
C, and PAUSE and to one of the layers of the force-sensing
resistor. The other layer of the force-sensing resistor is
connected to CPR_FORCE, and the lower conductive ink traces
associated with buttons A, B, C, and PAUSE are connected to
BUTTON_DETECT through resistors R1, R2, R3, and R4. As an
alternative to the use of a force-sensing resistor, a
compression-sensing accelerometer 76 may be employed, in which case
CPR_FORCE is replaced by CPR_ACCEL connected to accelerometer 76.
Red light-emitting diode 70, near-infrared light-emitting diode 72,
and photodetector diode 74 of the pulse oximetry system are
connected to RLED, ILED, and ISENSE respectively, as well as ground
AGND. As an alternative to the use of a pulse oximetry system, a
phonocardiogram system may be employed, in which case RLED, ILED,
and ISENSE is replaced by SENSE connected to microphone 78 and
amplifier 80.
[0050] FIGS. 6-9 illustrate the routine of the resuscitation system
described above, which is based on steps A, B, and C (airway,
breathing, and circulation). Because step C includes defibrillation
as well as chest compressions, all of the aspects of resuscitation
are tied together in one protocol (actually, if defibrillation were
considered to be a step D distinct from step C, the sequence of
steps would be A, B, D, C).
[0051] The first thing the rescuer must do upon arriving at the
patient is to determine whether the patient is unconscious and
breathing. The rescuer opens the patient's airway, administers
breaths to the patient if the patient is not breathing, and checks
to determine whether a pulse is present. If there is no pulse,
rather than perform chest compressions as in standard CPR, the
rescuer allows the resuscitation control box to analyze the
patient's electrical rhythm, and if the resuscitation control box
determines that the rhythm is shockable, the resuscitation control
box causes one or more shocks to be applied to the patient, and
then the rescuer performs chest compressions. Thus, the invention
provides a first response system that can keep the patient viable
until an advanced life support time arrives to perform advanced
techniques including pacing, further defibrillation, and drug
therapy.
[0052] If the resuscitation control box determines that it should
apply one or more defibrillation shocks to the patient, it is
important that the rescuer not be anywhere near the patient when
the shocks are applied to the patient. Prior to application of each
shock, the resuscitation control box instructs the rescuer to
please press the "ready" button when everybody is clear of the
patient. The pressing of the "ready" button verifies that the
rescuer's hands are off of the patient.
[0053] When the resuscitation control box detects a shockable
rhythm, the resuscitation control box provides shocks of
appropriate duration and energy (such as a sequence of shocks of
increasing energy from 200 Joules to 300 Joules to the highest
setting, 360 Joules, with the resuscitation control box performing
analysis after each shock to determine whether another shock is
required). If the defibrillation therapy is successful, the
patient's rhythm is typically converted from ventricular
fibrillation, ventricular tachycardia, or ventricular flutter to
bradycardia, idio-ventricular rhythm, or asystole, all of which
require CPR. It is rare to convert to a normal rhythm. Once the
resuscitation control box has caused defibrillation shocks to be
applied to the patient, the resuscitation control box automatically
senses the patient's condition, and depending on the patient's
condition will either prompt the responder to perform CPR or will
not prompt the respond to perform CPR.
[0054] Defibrillation equipment can be somewhat intimidating to
rescuers who are not medical professionals because the equipment
can lead the rescuer to feel responsibility for having to save a
loved one's life. It is important that the defibrillation equipment
reduce this sense of responsibility. In particular, when the
rescuer presses the "ready" button, rather than apply a shock
immediately that will cause the patient's body to jump
dramatically, the resuscitation control box will thank the rescuer
and instruct the rescuer to remain clear of the patient and then
wait for about two seconds (the resuscitation control box may
describe this period to the rescuer as being an internal safety
check, even if no substantial safety check is being performed).
This process has an effect similar to a conversation that hands
responsibility to the resuscitation control box, which makes the
decision whether to apply the shock. Thus, the system maintains the
rescuer safety features of a semi-automatic external defibrillator,
because the rescuer must press the "ready" button before each
shock, while appearing to operate more as a fully automatic
external defibrillator because the time delay immediately prior to
each shock leaves the rescuer with the impression that operation of
the equipment is out of the hands of the rescuer. The use of CPR
prompts in combination with the defibrillation also adds to the
sense that the rescuer is simply following instructions from the
resuscitation control box.
[0055] With reference to FIGS, 6-9, when the rescuer turns the
resuscitation control box on (step 101), the resuscitation control
box first informs the rescuer that the rescuer can temporarily halt
prompting by pressing the PAUSE button (step 102), and then, after
a pause, instructs the rescuer to check responsiveness of patient,
and if the patient is non-responsive to call an emergency medical
service (EMS) (steps 103, 104). The resuscitation control box then
instructs the rescuer to check the patient's airway to determine
whether the patient is breathing (steps 105-107).
[0056] After a pause, the resuscitation control box then instructs
the rescuer that if the patient is breathing the patient should be
placed on the patient's side, unless trauma is suspected, and that
the rescuer should press the PAUSE button (steps 108-109). Then the
resuscitation control box instructs the rescuer to perform
mouth-to-mouth resuscitation if the patient is not breathing (steps
110-114) Then the resuscitation control box instructs the rescuer
to press an Airway Help button A if the patient's airway is
blocked, so that the resuscitation control box can give prompts for
clearing obstructed airways (steps 115 of FIG. 6B and 147-158 of
FIGS. 9A-9B).
[0057] Next, after a pause (step 116a), if the resuscitation
control box does not include pulse oximetry or phonocardiogram
capability (step 116b), the resuscitation control box instructs the
rescuer to check the patient's pulse (step 117). Alter another
pause, the resuscitation control box instructs the rescuer to press
a Breathing Help button B if the patient's pulse is okay but the
patient is not breathing, so that the resuscitation control box can
give prompts for assisting the patient's breathing (steps 118 and
119 of FIG. 7A and 140-146 of FIG. 8). Light-emitting diodes
adjacent the various buttons indicate which button has been pressed
most recently (only one light remains on at a time). The
resuscitation control box next prompts the rescuer to contact an
emergency medical system (step 120) and to open the patient's shirt
or blouse and attach the adhesive pads (steps 122f-122h).
[0058] If the resuscitation control box does include pulse oximetry
or phonocardiogram capability (step and 116b), the resuscitation
control box prompts the rescuer to open the patient's shirt or
blouse and attach the adhesive pads (steps 121 and 122a). If the
pulse oximetry or phonocardiogram system does not provide a valid
pulsatile reading (step 122b), then the flow chart proceeds to step
117. If the pulse oximetry or phonocardiogram system does provide a
valid pulsatile reading and detects a pulse (steps 122b and 122c),
then the resuscitation control box begins the breathing help
routine (steps 122d of FIG. 7B and step 140 of FIG. 8). If the
pulse oximetry or phonocardiogram system does not detect a pulse,
then the resuscitation control prompts the rescuer to contact an
emergency medical system (step 122e), measures the impedance of the
patient to determine whether it is within an acceptable range for
application of shocks (step 123) and determines whether the
patient's rhythm is shockable (steps 124). If the rhythm is
shockable, the resuscitation control box causes a sequence of
shocks to be applied to the patient, each shock requiring the
rescuer first to press the "READY" button on the resuscitation
control box (steps 124-131). After the last shock in the sequence,
or if the rhythm is non-shockable, the resuscitation control box
prompts the rescuer in CPR (steps 132-139). The flowchart then
returns to step 117.
[0059] FIG. 8 shows the steps 140-146 for prompting the rescuer to
assist the patient's breathing. After 12 breaths have been
completed (step 144), the pulse oximetry or phonocardiogram system
attempts to detect a pulse (step 145a), or, if the system does not
include a pulse oximetry or phonocardiogram system, the
resuscitation control box prompts the rescuer to check the
patient's pulse. If no pulse is present, the resuscitation control
box prompts the rescuer to press a Circulation Help button C (step
145b) that brings the rescuer back to the circulation portion of
the flowchart. Otherwise, if a pulse is detected, then the flow
chart of FIG. 8 returns to step 142.
[0060] The combined defibrillation and CPR resuscitation assembly
provided by the invention can be less intimidating than
conventional AEDs because the assembly is not devoted solely to
defibrillation. Moreover, the resuscitation assembly is less
intimidating because it accommodates common skill retention
problems with respect to necessary techniques ancillary to
defibrillation such as mouth-to-mouth resuscitation and CPR,
including the appropriate rates of chest compression, the proper
location for performing compressions, the proper manner of tilting
the patient's head. In addition, because the rescuer knows that it
may never even be necessary to apply a defibrillation shock during
use of the resuscitation assembly, the rescuer may be more
comfortable using the resuscitation assembly for mouth-to-mouth
resuscitation and CPR. Unlike previous CPR prompting devices, the
rescuer would be required to place the electrode assembly on top of
the patient, but the rescuer would do this with the belief that the
resuscitation assembly will be sensing the patient's condition and
that the likelihood that the resuscitation assembly is actually
going to apply a shock is low. If, during this resuscitation
process, the resuscitation control box instructs the rescuer to
press the "READY" button so that a defibrillation shock can be
applied, the rescuer will likely feel comfortable allowing the
shock to be applied to the patient. Basically, the resuscitation
assembly simply tells the rescuer what to do, and by that point,
given that the rescuer is already using the assembly, the rescuer
is likely simply to do what the rescuer is told to do. Essentially,
the rescuer will be likely to view the resuscitation assembly as
simply being a sophisticated CPR prompting device with an
additional feature incorporated into it, and since rescuers are
less likely to be intimidated by CPR prompting devices than AEDs,
they will be likely to use the resuscitation assembly according to
the invention when it is needed.
[0061] Other embodiments are within the following claims. For
example, in other embodiments the system can perform pacing in
addition to defibrillation. Pulse detection methods other than
pulse oximetry and phonocardiogram may be employed. Any method
capable of detecting a victim's pulse can be used with the aspects
of the invention calling for pulse detection.
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