U.S. patent application number 14/269588 was filed with the patent office on 2014-08-28 for automated pediatric defibrillator.
This patent application is currently assigned to ZOLL Medical Corporation. The applicant listed for this patent is ZOLL Medical Corporation. Invention is credited to Ziad F. Elghazzawi, Gary A. Freeman, Frederick J. Geheb, Michael Parascandola.
Application Number | 20140243916 14/269588 |
Document ID | / |
Family ID | 35150513 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140243916 |
Kind Code |
A1 |
Freeman; Gary A. ; et
al. |
August 28, 2014 |
Automated Pediatric Defibrillator
Abstract
A device for assisting a rescuer in delivering therapy to an
adult or pediatric patient, the device including a user interface
comprising a display and/or audio speakers, the user interface
being configured to deliver prompts to a rescuer to assist the
rescuer in delivering therapy to a patient; a processor configured
to provide prompts to the user interface and to perform an ECG
analysis algorithm on ECG information detected from the patient; at
least one detection element configured to determine without rescuer
input via the user interface that a pediatric patient is being
treated; wherein, if a pediatric patient is detected, the processor
modifies the ECG analysis algorithm or the prompts provided to the
user interface to use an ECG analysis algorithm or prompts adapted
for a pediatric patient rather than for an adult patient.
Inventors: |
Freeman; Gary A.; (Newton
Center, MA) ; Elghazzawi; Ziad F.; (Newton, MA)
; Geheb; Frederick J.; (Danvers, MA) ;
Parascandola; Michael; (Londonderry, NH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZOLL Medical Corporation |
Chelmsford |
MA |
US |
|
|
Assignee: |
ZOLL Medical Corporation
Chelmsford
MA
|
Family ID: |
35150513 |
Appl. No.: |
14/269588 |
Filed: |
May 5, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11104272 |
Apr 12, 2005 |
8738130 |
|
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14269588 |
|
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60561493 |
Apr 12, 2004 |
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Current U.S.
Class: |
607/3 |
Current CPC
Class: |
A61B 5/4836 20130101;
A61N 1/39044 20170801; A61N 1/046 20130101; A61N 1/3918 20130101;
A61N 1/3925 20130101; A61N 1/3993 20130101; A61N 1/3968 20130101;
A61N 1/0492 20130101; A61N 1/3906 20130101 |
Class at
Publication: |
607/3 |
International
Class: |
A61N 1/39 20060101
A61N001/39; A61B 5/00 20060101 A61B005/00 |
Claims
1. An external defibrillation device for assisting a rescuer in
delivering defibrillation therapy to an adult or pediatric patient,
the device comprising a user interface comprising a display or
audio speakers, the user interface being configured to deliver
prompts to a rescuer to assist the rescuer in delivering therapy to
a patient; a processor configured to provide prompts to the user
interface and to perform an ECG analysis algorithm on ECG
information detected from the patient; a force or pressure sensor
for detecting information pertaining to the weight of the patient;
wherein the processor modifies the defibrillation energy delivered
to the patient based on the information pertaining to the weight of
the patient.
2. The device of claim 1 wherein the processor modifies the ECG
analysis algorithm based on the information pertaining to the
weight of the patient.
3. The device of claim 1 wherein the force or pressure sensor is
incorporated into a shoulder support that is placed under the
shoulders of the patient.
4. The device of claim 1 wherein the shoulder support is a cover
for the defibrillator.
5. The device of claim 4 wherein the cover has an upper surface
that is inclined at an angle that makes it suitable to be used to
properly position the patient's airway by lifting the patient's
shoulders to cause the patient's head to tilt back at an angle.
6. The device of claim 4 wherein the cover is configured to be
positioned under a patient's neck and shoulders to support the
patient's shoulders and neck in a way that helps to maintain the
patient's airway in an open position.
7. The device of claim 3 or 4 wherein the information from sensors
in the shoulder support element is communicated to the
defibrillator by one or more of the following techniques: by a wire
extending from the support to the defibrillator, or by a wireless
communication connection between the support and the defibrillator.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of and claims
priority to U.S. application Ser. No. 11/104,272, filed on Apr. 12,
2005, which application claims priority to U.S. Provisional
Application No. 60/561,493, filed on Apr. 12, 2004. Both
applications are hereby incorporated by reference.
TECHNICAL FIELD
[0002] This invention relates to the treatment of cardiac arrest in
pediatric populations with automatic external defibrillators
(AEDs).
BACKGROUND
[0003] Automatic External Defibrillators (AEDs) are used by
non-medical personnel to defibrillate victims of cardiac arrest the
prevalence of which is approximately 600,000 people per year,
worldwide. In the past, these AEDs had only been available for the
adult population, and the pediatric arrest victims were forced to
wait valuable minutes for the professional rescuers such as
paramedics, doctors or nurses to arrive. AEDs are now available
that are designed specifically to be compatible for use on
children. Because defibrillation energies are lower with children,
various methods have been developed to accommodate this fact and
provide a means of switching defibrillation energies if a pediatric
arrest victim is present. One method, described in U.S. Pat. No.
6,101,413, determines a pediatric arrest victim is present if the
AED detects that electrodes specifically designed for use with
children are attached to the device, in which case the energy
levels and voice prompts associated with energy delivery are
adjusted to conform with those most appropriate for children. U.S.
Patent Application 2003/0195567A1 describes a method that
determines a victim is a child based on user input form the AED
operator. The energy levels are set based on such indirect means as
a measurement of the patient, e.g., the length of an anatomical
feature of the victim may be correlated within the AED to a
specific energy level.
[0004] Resuscitation treatments for patients suffering from cardiac
arrest generally include clearing and opening the patient's airway,
providing rescue breathing for the patient, and applying chest
compressions to provide blood flow to the victim's heart, brain and
other vital organs. If the patient has a shockable heart rhythm,
resuscitation also may include defibrillation therapy. The term
basic life support (BLS) involves all the following elements:
initial assessment; airway maintenance; expired air ventilation
(rescue breathing); and chest compression. When all three [airway
breathing, and circulation, including chest compressions] are
combined, the term cardiopulmonary resuscitation (CPR) is used. In
the case of pediatric arrest, CPR takes on a heightened prominence
based on the fact that cardiac arrest is rare in children, and many
more children are affected by respiratory arrest due to choking,
drowning, poisoning and asthma.
[0005] There are many different kinds of abnormal heart rhythms,
some of which can be treated by defibrillation therapy ("shockable
rhythms") and some which cannot (non-shockable rhythms"). For
example, most ECG rhythms that produce significant cardiac output
are considered non-shockable (examples include normal sinus
rhythms, certain bradycardias, and sinus tachycardias). There are
also several abnormal ECG rhythms that do not result in significant
cardiac output but are still considered non-shockable, since
defibrillation treatment is usually ineffective under these
conditions. Examples of these non-shockable rhythms include
asystole, electromechanical disassociation and other pulseless
electrical activity. Although a patient cannot remain alive with
these non-viable, non-shockable rhythms, applying shocks will not
help convert the rhythm. The primary examples of shockable rhythms,
for which the caregiver should perform defibrillation, include
ventricular fibrillation, ventricular tachycardia, and ventricular
flutter.
[0006] The current protocols recommended by the American Heart
Association (AHA) are as follows: after using a defibrillator to
apply one or more shocks to a patient who has a shockable ECG
rhythm, the patient may nevertheless remain unconscious, in a
shockable or non-shockable, perfusing or non-perfusing rhythm. If a
non-perfusing rhythm is present, the caregiver may then resort to
performing CPR for a period of time in order to provide continuing
blood flow and oxygen to the patient's heart, brain and other vital
organs. If a shockable rhythm continues to exist or develops during
the delivery of CPR, further defibrillation attempts may be
undertaken following this period of cardiopulmonary resuscitation.
As long as the patient remains unconscious and without effective
circulation, the caregiver can alternate between use of the
defibrillator (for analyzing the electrical rhythm and possibly
applying a shock) and performing cardio-pulmonary resuscitation
(CPR). CPR generally involves a repeating pattern of five or
fifteen chest compressions followed by a pause during which two
rescue breaths are given.
[0007] Defibrillation can be performed using an AED. The American
Heart Association, European Resuscitation Council, and other
similar agencies provide protocols for the treatment of victims of
cardiac arrest that include the use of AEDs. These protocols define
a sequence of steps to be followed in accessing the victim's
condition and determining the appropriate treatments to be
delivered during resuscitation. Caregivers who may be required to
use an AED are trained to follow these protocols.
[0008] Most automatic external defibrillators are actually
semi-automatic external defibrillators (SAEDs), which require the
caregiver to press a start or analyze button, after which the
defibrillator analyzes the patient's ECG rhythm and advises the
caregiver to provide a shock to the patient if the electrical
rhythm is shockable. The caregiver is then responsible for pressing
a control button to deliver the shock. Following shock delivery,
the SAED may reanalyze the patient's ECG rhythm, automatically or
manually, and advise additional shocks or instruct the caregiver to
check the patient for signs of circulation (indicating that the
defibrillation treatment was successful or that the rhythm is
non-shockable) and to begin CPR if circulation has not been
restored by the defibrillation attempts. Fully automatic external
defibrillators, on the other hand, do not wait for user
intervention before applying defibrillation shocks. As used below,
automatic external defibrillators (AEDs) include semi-automatic
external defibrillators (SAEDs).
[0009] Automated External Defibrillators include signal processing
software that analyzes ECG signals acquired from the victim to
determine when a cardiac arrhythmia such as Ventricular
Fibrillation (VF) or shockable ventricular tachycardia (VT) exists.
Usually, these algorithms are designed to perform ECG analyses at
specific times during the rescue event. The first ECG analysis is
usually initiated within a few seconds following attachment of the
defibrillation electrodes to the patient. Subsequent ECG analyses
may or may not be initiated based upon the results of the first
analysis. Typically if the first analysis detects a shockable
rhythm, the rescuer is advised to deliver a defibrillation shock.
Following the shock delivery a second analysis is automatically
initiated to determine whether the defibrillation treatment was
successful or not (i.e. the shockable ECG rhythm has been converted
to a normal or other non-shockable rhythm). If this second analysis
detects the continuing presence of a shockable arrhythmia, the AED
advises the user to deliver a second defibrillation treatment. A
third ECG analysis may then be initiated to determine whether the
second shock was or was not effective. If a shockable rhythm
persists, the rescuer is then advised to deliver a third
defibrillation treatment.
[0010] The typical algorithms process the ECG for measured features
which will differentiate the rhythm as shockable (ventricular
fibrillation (VF) and ventricular tachycardia (VT)) or
non-shockable rhythms (normal sinus rhythms (NSR), abnormal rhythms
(ABN), non-shockable VT's and asystole). Some of these features
include R to R interval averaging, R to R interval variance,
average and maximum signal amplitude, measures of baseline
isoelectric time, QRS width, ECG first difference distributions,
and parameters from frequency domain analysis.sup.1 Analyses of
annotated ECG databases establish the distribution of values for a
given feature for shockable and non-shockable rhythms. Appropriate
decision logic techniques can be used to combine this knowledge and
produce the shock or non-shock decision.
[0011] Although AEDs have been designed for use on adults and the
ECG arrhythmia logic has been developed for the adult population,
there is a clear need to extend the use of AEDs to children with
cardiac arrest. Recent literature have reported the accuracies of
adult based AED arrhythmia algorithms on ECG databases collected
from children and have concluded they are safe and effective.
However, there are significant differences between adult and
pediatric ECG rhythms. For example, the pediatric ECG exhibits
faster normal heart rates, narrower QRS widths, and shorter PR and
QT intervals as compared to adults. Shockable ventricular
tachycardia occurs at much higher rates (>200 BPM) in pediatric
subjects than adults (>150 BPM).
[0012] Following the third defibrillator shock or when any of the
analyses described above detects a non-shockable rhythm, treatment
protocols recommended by the American Heart Association and
European Resuscitation Council require the rescuer to check the
patient's pulse or to evaluate the patient for signs of
circulation. If no pulse or signs of circulation are present, the
rescuer is trained to perform CPR on the victim for a period of one
or more minutes. Following this period of cardiopulmonary
resuscitation (that includes rescue breathing and chest
compressions) the AED reinitiates a series of up to three
additional ECG analyses interspersed with appropriate
defibrillation treatments as described above. The sequence of 3 ECG
analyses/defibrillation shocks followed by 1-3 minutes of CPR,
continues in a repetitive fashion for as long as the AED's power is
turned on and the patient is connected to the AED device.
Typically, the AED provides audio prompts to inform the rescuer
when analyses are about to begin, what the analysis results were
and when to start and stop the delivery of CPR.
[0013] The AED can be used on adult and pediatric patients.
However, the American Heart Association recommends a different
protocol in the rescue of pediatric victims compared to the adult
rescue protocol particularly with regards to the application of
CPR. Because of the heightened prominence of airway and breathing
with pediatric arrest victims, the AHA recommends that prior even
to calling and activating emergency medical services (EMS) system,
the child's airway is first checked for obstructions, the airway is
cleared, and mouth to mouth breathing is performed in order to
provide what is usually the primary treatment of respiration to the
child. The AHA recommends a ratio 15 chest compressions to two
ventilations in the case of an adult victim and a ratio of five
chest compressions to one ventilation in the case of pediatric
victims. The recommended rate of compressions in both adult and
pediatric victims is 100 compressions per minute. The rationale for
this difference in compression to ventilation ratios is that: 1)
the most common cause in pediatric (<8 years of age) arrest is
respiratory; and 2) respiratory rates in pediatric (<8 years of
age) population are faster than respiratory rates in adults. In
addition, the recommended depth of chest compression for pediatric
victims (<8 years of age) is 1 to 1.5 inches while the
recommended chest compression depth for adult and pediatric (>8
years of age) is 1.5 to 2 inches.
[0014] Existing AEDs are unable to provide appropriate rescue
protocol and ECG analysis for a pediatric (<8 years of age)
victim that is different from an adult rescue protocol and ECG
analysis. Also, a lay rescuer who is trained on pediatric
resuscitation and is not aware of the AHA guidelines
recommendations will not be able to provide an effective
resuscitation for a pediatric victim when using these existing
AEDs.
SUMMARY
[0015] In a first aspect, the invention features a device for
assisting a rescuer in delivering therapy to an adult or pediatric
patient, the device comprising a user interface comprising a
display and/or audio speakers, the user interface being configured
to deliver prompts to a rescuer to assist the rescuer in delivering
therapy to a patient, a processor configured to provide prompts to
the user interface and to perform an ECG analysis algorithm on ECG
information detected from the patient, at least one detection
element configured to determine without rescuer input via the user
interface that a pediatric patient is being treated, wherein if a
pediatric patient is detected, the processor modifies the ECG
analysis algorithm to use an ECG analysis algorithm configured for
a pediatric patient rather than for an adult patient.
[0016] In a second aspect, the invention features a device for
assisting a rescuer in delivering therapy to an adult or pediatric
patient, the device comprising a user interface comprising a
display and/or audio speakers, the user interface being configured
to deliver prompts to a rescuer to assist the rescuer in delivering
therapy to a patient, a processor configured to provide prompts to
the user interface and to perform an ECG analysis algorithm on ECG
information detected from the patient, at least one detection
element configured to determine without rescuer input via the user
interface that a pediatric patient is being treated, wherein if a
pediatric patient is detected, the processor modifies the prompts
provided to the user interface to use prompts adapted for a
pediatric patient rather than for an adult patient.
[0017] In a third aspect, the invention features a device for
assisting a rescuer in delivering therapy to an adult or pediatric
patient, the device comprising a user interface comprising a
display and/or audio speakers, the user interface being configured
to deliver prompts to a rescuer to assist the rescuer in delivering
therapy to a patient, a processor configured to provide prompts to
the user interface and to perform an ECG analysis algorithm on ECG
information detected from the patient, at least one detection
element configured to determine without rescuer input via the user
interface that a pediatric patient is being treated, wherein if a
pediatric patient is detected, the processor modifies the CPR
protocol that governs CPR prompts provided to the user interface to
use CPR prompts adapted for a pediatric patient rather than for an
adult patient.
[0018] In preferred implementations, one or more of the following
features may be incorporated. The invention may further comprise an
automatic external defibrillator for delivering defibrillation
shocks to the patient using defibrillation electrodes applied to
the patient. The prompts provided via the user interface may
comprise prompts as to CPR chest compression, and the CPR chest
compression prompts may be changed from an adult set of prompts to
a pediatric set of prompts if a pediatric patient is detected. The
pediatric set of prompts may address depth and rate of CPR chest
compressions. The invention may further comprise one or more
sensors for measuring the rate and depth of CPR related chest
compressions. The detection element may comprise circuitry for
detecting whether a pediatric or an adult defibrillation electrode
is in use. The detection element may comprise a force or pressure
sensor located on a shoulder support element for sensing force or
pressure from the weight of the patient. The energy of
defibrillation shocks may be determined based in part on
information as to the patient's weight obtained from the force or
pressure sensor on the shoulder support. The shoulder support
element may comprise a removable cover of the device. The detection
element may comprise one or more sensors for determining from the
separation of defibrillation electrodes placed on the patient
whether the patient is a pediatric or adult patient.
[0019] In a fourth aspect, the invention features an external
defibrillation device for assisting a rescuer in delivering
defibrillation therapy to an adult or pediatric patient, the device
comprising a user interface comprising a display or audio speakers,
the user interface being configured to deliver prompts to a rescuer
to assist the rescuer in delivering therapy to a patient, a
processor configured to provide prompts to the user interface and
to perform an ECG analysis algorithm on ECG information detected
from the patient, a force or pressure sensor for detecting
information pertaining to the weight of the patient, wherein the
processor modifies the defibrillation energy delivered to the
patient based on the information pertaining to the weight of the
patient.
[0020] In preferred implementations, one or more of the following
features may be incorporated. The processor may modify the ECG
analysis algorithm based on the information pertaining to the
weight of the patient. The force or pressure sensor may be
incorporated into a shoulder support that is placed under the
shoulders of the patient. The shoulder support may be a cover for
the defibrillator. The cover may have an upper surface that is
inclined at an angle that makes it suitable to be used to properly
position the patient's airway by lifting the patient's shoulders to
cause the patient's head to tilt back at an angle. The cover may be
configured to be positioned under a patient's neck and shoulders to
support the patient's shoulders and neck in a way that helps to
maintain the patient's airway in an open position. The information
from sensors in the shoulder support element may be communicated to
the defibrillator by one or more of the following techniques: by a
wire extending from the support to the defibrillator, or by a
wireless communication connection between the support and the
defibrillator.
[0021] In a fifth aspect, the invention features an external
defibrillation device for assisting a rescuer in delivering
defibrillation therapy to an adult or pediatric patient, the device
comprising a user interface comprising a display or audio speakers,
the user interface being configured to deliver prompts to a rescuer
to assist the rescuer in delivering therapy to a patient, a
processor configured to provide prompts to the user interface and
to perform an ECG analysis algorithm on ECG information detected
from the patient, a shoulder support element for placement under
the shoulders of the patient to assist in keeping the airway open,
sensors in the shoulder support element for determining if the
patient's shoulders have been properly positioned on the
element.
[0022] In preferred implementations, one or more of the following
features may be incorporated. The shoulder support element may
comprise a cover for the device.
[0023] In a sixth aspect, the invention features an external
defibrillation device for assisting a rescuer in delivering
defibrillation therapy to an adult or pediatric patient, the device
comprising a user interface comprising a display or audio speakers,
the user interface being configured to deliver prompts to a rescuer
to assist the rescuer in delivering therapy to a patient, a
processor configured to provide prompts to the user interface and
to perform an ECG analysis algorithm on ECG information detected
from the patient, defibrillation electrodes for placement on the
chest of the patient, one or more sensors located in one or both of
the defibrillation electrodes, the sensors being configured to
determine a distance between the electrodes after they are placed
on the patient's chest, wherein the processor can determine
information pertaining to the size of the patient from the distance
determined from the one or more sensors, and wherein the processor
can vary the prompts, or the ECG analysis algorithm, or the energy
delivered to the patient based on the information pertaining to the
size of the patient.
[0024] In preferred implementations, one or more of the following
features may be incorporated. The processor may estimate the
circumferential girth of the patient from the information obtained
from the sensors. The processor may estimate the age of the patient
from the information obtained from the sensors. Modifications to
the ECG analysis algorithm may include one or more of the
following: heart rate criteria, QRS width criteria, VF frequency
content criteria, or ECG amplitude criteria. Modifications to the
prompts may include changing a sequence of prompts, a number of
prompts, or a type of prompts. The prompts may include prompts on
CPR compression and CPR ventilation, and the
compression-ventilation ratio may be about 5:1 for pediatric
patients and about 15:2 for adult patients. The prompts may include
prompts on CPR compression depth, and the desired compression depth
for pediatric patients may be in the range of about 1.0 to 1.5
inches, and the desired compression depth for adult patients may be
in the range of about 1.0 to 2.0 inches. The prompts may include a
prompt informing the rescuer as to whether the device is operating
in an adult or pediatric mode. The prompts may include prompting of
the CPR interval T1 based on one or more of patient rhythm, age, or
weight. The invention may further comprise one or more sensors and
prompts for detecting and prompting the user to achieve a complete
chest release during CPR. The prompts may include pediatric
specific prompts for the compression rate R1. The prompts may
include adult specific prompts for the compression rate R1.
[0025] The invention may feature a system that will alter the AED
arrhythmia processing for adults or children based the automatic
sensing or manual assignment of the patient type. Altering the AED
arrhythmia processing for pediatric subjects based on the pediatric
specific logic may achieve higher sensitivity and specificity of
the shock decision that will significantly improve the safety and
effective of the device.
[0026] The invention may provide an improved method for providing
an appropriate rescue protocol and ECG analysis based on patient
age, thoracic circumferential girth and weight in an automated
fashion without the need for any user intervention. Utilizing a
means of detecting a patient's age, weight or thoracic
circumferential girth, the AED can automatically switch to
providing the appropriate rescue protocol and optimizing
performance of the ECG analysis algorithm for a specific victim age
and weight. If an untrained rescuer activates the proposed AED, the
protocol is tailored to instruct the user to provide one minute of
CPR to the pediatric (<8 years of age) victim before activating
the EMS system. The protocol is tailored to instruct the user to
activate the EMS system before providing any treatment or CPR to an
adult victim. Also, since the AED is capable of detecting the depth
of chest compression when used with a set of defibrillation
electrodes embedding a chest compression detector, it can guide the
rescuer to administer appropriate chest compression-ventilation
ratio and depth of compressions based on specific victim age and
weight. Furthermore, the proposed AED can select a preconfigured
CPR period length based on the type of rhythm when the CPR interval
is entered. For example, the pre-programmed CPR period when an
asystole, PEA, or normal rhythm is detected can be longer than
after a ventricular fibrillation or tachycardia is detected.
[0027] The invention may provide a more comprehensive and effective
system for delivering treatment to pediatric arrest victims,
providing an appropriate rescue protocol and ECG analysis based on
patient age, thoracic circumferential girth and weight in an
automated fashion without the need for any user intervention.
[0028] The invention may feature a device for assisting a rescuer
in delivering therapy to an adult or pediatric patient, the device
comprising a user interface comprising a display or audio speakers,
the user interface being configured to deliver prompts to a rescuer
to assist the rescuer in delivering therapy to a patient; a
processor configured to provide prompts to the user interface and
to perform an ECG analysis algorithm on ECG information detected
from the patient; at least one detection element configured to
determine without rescuer input via the user interface that a
pediatric patient is being treated; wherein, if a pediatric patient
is detected, the processor modifies the ECG analysis algorithm or
the prompts provided to the user interface to use an ECG analysis
algorithm or prompts better suited to a pediatric patient than to
an adult patient.
[0029] The device may incorporate an automatic external
defibrillator for delivering defibrillation shocks to the patient
using defibrillation electrodes applied to the patient. The prompts
provided via the user interface may comprise prompts as to CPR
chest compression, and the CPR chest compression prompts are
changed from an adult set of prompts to a pediatric set of prompts
if a pediatric patient is detected. The pediatric set of prompts
may address depth and rate of CPR chest compressions. One or more
sensors for measuring the rate and depth of CPR related chest
compressions may be provided. The detection element may comprise
circuitry for detecting whether a pediatric or an adult
defibrillation electrode is in use. The detection element may
comprise a force or pressure sensor located on a shoulder support
element for sensing force or pressure from the weight of the
patient. The energy of defibrillation shocks may be determined
based in part on information as to the patient's weight obtained
from the force or pressure sensor on the shoulder support. The
shoulder support element may comprise a removable cover of the
device. The detection element may comprise one or more sensors for
determining from the separation of defibrillation electrodes placed
on the patient whether the patient is a pediatric or adult
patient.
[0030] The AED may include the capability of measuring the rate and
depth of CPR related chest compressions and automatically switch
when specific defibrillation electrode types are detected to
provide appropriate rescue protocol, ECG analysis, and CPR interval
length and guidance based on the victim's determined age. Based on
the determined patient age, appropriate ventilation to compression
ratio and compression interval length are determined, and guidance
is provided to the rescuer to provide appropriate chest
compressions/ventilation ratio and rate and compression depth via
voice and text prompts throughout the entire rescue process.
[0031] The invention may feature an external defibrillation device
for assisting a rescuer in delivering defibrillation therapy to an
adult or pediatric patient. The device may comprise a user
interface comprising a display or audio speakers, the user
interface being configured to deliver prompts to a rescuer to
assist the rescuer in delivering therapy to a patient; a processor
configured to provide prompts to the user interface and to perform
an ECG analysis algorithm on ECG information detected from the
patient; a force or pressure sensor for detecting information
pertaining to the weight of the patient; wherein the processor
modifies the defibrillation energy delivered to the patient based
on the information pertaining to the weight of the patient.
[0032] The processor may modify the ECG analysis algorithm based on
the information pertaining to the weight of the patient. The force
or pressure sensor may be incorporated into a shoulder support that
is placed under the shoulders of the patient. The shoulder support
may be a cover for the defibrillator. The cover may have an upper
surface that is inclined at an angle that makes it suitable to be
used to properly position the patient's airway by lifting the
patient's shoulders to cause the patient's head to tilt back at an
angle. The cover may be configured to be positioned under a
patient's neck and shoulders to support the patient's shoulders and
neck in a way that helps to maintain the patient's airway in an
open position. The information from sensors in the shoulder support
element may be communicated to the defibrillator by one or more of
the following techniques: by a wire extending from the support to
the defibrillator, or by a wireless communication connection
between the support and the defibrillator.
[0033] Some implementations may provide an automated means for
determining the age of the victim with greater specificity. Victim
weight is a commonly used clinical measure for determining
defibrillation energies for children. An integrated force sensor
may be provided within the AED for measuring the patient's weight
and the AED will then adjust the defibrillation energy and ECG
analysis parameters based on the measured weight.
[0034] The force sensor may be incorporated into the cover of the
AED. The cover has an upper surface that is inclined at an angle
that makes it suitable to be used to properly position the
patient's airway, by, for instance, lifting the patient's shoulders
thereby causing the patient's head to tilt back at the proper
angle. The cover is constructed to be positioned under a patient's
neck and shoulders to support the patient's shoulders and neck in a
way that helps to maintain his airway in an open position, i.e.,
maintaining the patient in the head tuck-chin lift position. When a
caregiver encounters a person who appears to be suffering from
cardiac arrest, the caregiver should follow recommended
resuscitation procedures, such as are specified by the AHA
Guidelines for Cardiopulmonary Resuscitation and Emergency
Cardiovascular Care. If there is no evidence of head or neck
trauma, the caregiver should clear any debris from the patient's
airway. After this has been done, the caregiver should roll the
patient onto his side, place cover under the patient's shoulders,
and roll the patient back onto his back. The cover should be
positioned so as to support the patient in the head tilt-chin lift
position. The caregiver can then proceed with CPR and/or use of the
defibrillator. The positions (a patient in the head lift-chin tilt
position and a patient with a closed airway) are also shown in the
AHA Guidelines for Cardiopulmonary Resuscitation and Emergency
Cardiovascular Care, Aug. 22, 2000, p. 1-32, FIGS. 7 and 8. The
cover is provided with a detection means for determining if the
patient's shoulders have been properly positioned on the cover.
Communication of the detection means located in the cover to the
processor in the device housing can be accomplished by making the
cover an integral element of the device housing, for instance via a
hinge element or by providing an interconnection element such as a
flat flexible cable. Communication may also be accomplished
wirelessly via such technologies as Bluetooth or inductive methods.
When the patient's shoulders are placed on the cover, the measured
force is communicated to the AED.
[0035] The invention may feature an external defibrillation device
for assisting a rescuer in delivering defibrillation therapy to an
adult or pediatric patient, the device comprising a user interface
comprising a display or audio speakers, the user interface being
configured to deliver prompts to a rescuer to assist the rescuer in
delivering therapy to a patient; a processor configured to provide
prompts to the user interface and to perform an ECG analysis
algorithm on ECG information detected from the patient; a shoulder
support element for placement under the shoulders of the patient to
assist in keeping the airway open; sensors in the shoulder support
element for determining if the patient's shoulders have been
properly positioned on the element.
[0036] The invention may feature an external defibrillation device
for assisting a rescuer in delivering defibrillation therapy to an
adult or pediatric patient, the device comprising a user interface
comprising a display or audio speakers, the user interface being
configured to deliver prompts to a rescuer to assist the rescuer in
delivering therapy to a patient; a processor configured to provide
prompts to the user interface and to perform an ECG analysis
algorithm on ECG information detected from the patient;
defibrillation electrodes for placement on the chest of the
patient; one or more sensors located in one or both of the
defibrillation electrodes, the sensors being configured to
determine a distance between the electrodes after they are placed
on the patient's chest; wherein the processor can determine
information pertaining to the size of the patient from the distance
determined from the one or more sensors, and wherein the processor
can vary the prompts, or the ECG analysis algorithm, or the energy
delivered to the patient based on the information pertaining to the
size of the patient.
[0037] The processor may estimate the circumferential girth of the
patient from the information obtained from the sensors. The
processor may estimate the age of the patient from the information
obtained from the sensors.
[0038] The sensor elements may be fabricated into the two
defibrillation electrodes placed on the victim's chest. The
electrodes may be constructed such that the relative distance
between the electrodes can be determined by the AED. Based on that
relative distance, the circumferential girth can be calculated by
the AED and used as a means of estimating patient age as well as
delivering the appropriate energy level.
[0039] Other features and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
DESCRIPTION OF DRAWINGS
[0040] FIG. 1 is a perspective view of an AED with its cover
on.
[0041] FIG. 2 is a perspective view of the AED of FIG. 1 with the
cover removed.
[0042] FIG. 3 is a block diagram of the AED.
[0043] FIG. 4 is a plan view of the graphical interface decal used
on the cover of the AED of FIG. 1.
[0044] FIG. 5 is a plan view of the graphical interface decal used
on the device housing of the AED of FIG. 1, as shown in FIG. 2.
[0045] FIG. 6a is a flow diagram for the pediatric AED
resuscitation protocol.
[0046] FIG. 6b is a flow diagram for the adult AED resuscitation
protocol.
[0047] FIG. 7 shows an exploded perspective view of the cover and
housing.
[0048] FIG. 8 shows a side plan view of the cover indicating angle
`A`.
[0049] FIGS. 9a and 9b show the effect on the patient's airway of
placing the cover beneath a patient's shoulders.
[0050] FIG. 10 shows the graphical instructions on the cover for
placing the cover under a patient's shoulders.
[0051] FIG. 11 shows an integrated electrode pad.
[0052] FIG. 12 is a flow diagram of the arrhythmia processing in
the AED.
[0053] FIG. 13 is a flow diagram of mode specific processing for
enhancing QRS detection.
[0054] FIG. 14 is a flow diagram of mode specific processing for
enhancing rhythm classification logic and shock determination.
[0055] FIG. 15 is an example AED arrhythmia logic table for an
adult.
[0056] FIG. 16 is an example AED arrhythmia logic table for a
child.
DETAILED DESCRIPTION
[0057] There are a great many possible implementations of the
invention, too many to describe herein. Some possible
implementations that are presently preferred are described below.
It cannot be emphasized too strongly, however, that these are
descriptions of implementations of the invention, and not
descriptions of the invention, which is not limited to the detailed
implementations described in this section but is described in
broader terms in the claims.
[0058] The terms "caregiver", "rescuer" and "user" are used
interchangeably in the description of the invention and refer to
the operator of the device providing care to the patient. "Victim"
is also used interchangeably with "patient".
[0059] Referring to FIGS. 1 and 2, an automated external
defibrillator 10 includes a removable cover 12 and a device housing
14. The defibrillator 10 is shown with cover 12 removed in FIG. 2.
An electrode assembly 16 (or a pair of separate electrodes) is
connected to the device housing 14 by a cable 18. Electrode
assembly 16 is stored under cover 12 when the defibrillator is not
in use.
[0060] Referring to FIG. 3, the invention includes a processor
means 20, a user interface 21 including such elements as a
graphical 22 or text display 23 or an audio output such as a
speaker 24, and a detection means 25 for determining whether at
least one of a series of steps in a protocol has been completed
successfully. In the preferred embodiment, the detection means 25
also includes the ability to determine both whether a particular
step has been initiated by a user and additionally whether that
particular step has been successfully completed by a user. Based on
usability studies in either simulated or actual use, common user
errors are determined and specific detection means are provided for
determining if the most prevalent errors have occurred.
[0061] Device housing 14 includes a power button 15 and a status
indicator 17. Status indicator 17 indicates to the caregiver
whether the defibrillator is ready to use.
[0062] The cover 12 includes a cover decal 30 (FIGS. 1 and 4)
including a logo 31 and a series of graphics 32, 34 and 36. Logo 31
may provide information concerning the manufacturer of the device
and that the device is a defibrillator (e.g., "ZOLL AED", as shown
in FIG. 1, indicating that the device is a Semi-automatic External
Defibrillator available from ZOLL Medical). Graphics 32, 34 and 36
lead the caregiver through the initial stages of a cardiac
resuscitation sequence as outlined in the AHA's AED treatment
algorithm for Emergency Cardiac Care pending arrival of emergency
medical personnel. (See "Guidelines 2000 for Cardiopulmonary
Resuscitation and Emergency Cardiovascular Care. Supplement to
Circulation," Volume 102, Number 8, Aug. 22, 2000, pp. 1-67.) Thus,
graphic 32, showing the caregiver and patient, indicates that the
caregiver should first check the patient for responsiveness, e.g.,
by shaking the patient gently and asking if the patient is okay.
Next, graphic 34, showing a telephone and an emergency vehicle,
indicates that the caregiver should call for emergency assistance
prior to administering resuscitation. Finally, graphic 36 indicates
that after these steps have been performed the caregiver should
remove the cover 12 of the defibrillator, remove the electrode
assembly 16 stored under the lid, and turn the power on by
depressing button 15. The graphics are arranged in clockwise order,
with the first step in the upper left, since this is the order most
caregivers would intuitively follow. However, in this case the
order in which the caregiver performs the steps is not critical,
and thus for simplicity no other indication of the order of steps
is provided.
[0063] The cover 12 is constructed to be positioned under a
patient's neck and shoulders, as shown in FIGS. 9a and 9b to
support the patient's shoulders and neck in a way that helps to
maintain his airway in an open position, i.e., maintaining the
patient in the head tuck-chin lift position. The cover is
preferably formed of a relatively rigid plastic with sufficient
wall thickness to provide firm support during resuscitation.
Suitable plastics include, for example, ABS, polypropylene, and
ABS/polypropylene blends.
[0064] Prior to administering treatment for cardiac arrest, the
caregiver should make sure that the patient's airway is clear and
unobstructed, to assure passage of air into the lungs. To prevent
obstruction of the airway by the patient's tongue and epiglottis
(e.g., as shown in FIG. 9a), it is desirable that the patient be
put in a position in which the neck is supported in an elevated
position with the head tilted back and down. Positioning the
patient in this manner is referred to in the American Heart
Association Guidelines for Cardiopulmonary Resuscitation and
Emergency Cardiovascular Care as the "head tilt-chin lift
maneuver." The head tilt-chin lift position provides a relatively
straight, open airway to the lungs through the mouth and trachea.
However, it may be difficult to maintain the patient in this
position during emergency treatment.
[0065] The cover 12 has an upper surface 24 that is inclined at an
angle A (FIG. 8) of from about 10 to 25 degrees, e.g., 15 to 20
degrees, so as to lift the patient's shoulders and thereby cause
the patient's head to tilt back. The upper surface 24 is smoothly
curved to facilitate positioning of the patient. A curved surface,
e.g., having a radius of curvature of from about 20 to 30 inches,
generally provides better positioning than a flat surface. At its
highest point, the cover 12 has a height H (FIG. 8) of from about
7.5 to 10 cm. To accommodate the width of most patients' shoulders,
the cover 12 preferably has a width W (FIG. 8) of at least 6
inches, e.g., from about 6 to 10 inches. If the cover 12 is not
wide enough, the patient's neck and shoulders may move around
during chest compressions, reducing the effectiveness of the
device. The positions shown in FIGS. 9a and 9b (a patient in the
head lift-chin tilt position and a patient with a closed airway)
are also shown in the AHA Guidelines for Cardiopulmonary
Resuscitation and Emergency Cardiovascular Care, Aug. 22, 2000, p.
I-32, FIGS. 7 and 8.
[0066] In a preferred implementation, if on power-up, the AED
detects that the pediatric defibrillation pads are attached then
the AED will automatically start a pediatric rescue protocol. FIG.
6a shows the details of one instance of the pediatric protocol. The
device will output voice/text prompts indicating to the rescuer to
check the victim's responsiveness (i.e., "Check Responsiveness")
and allow a preprogrammed time interval (e.g., 4 seconds) to allow
for checking the responsiveness before moving to the next state.
The device will next output voice/text prompts instructing the
rescuer to check breathing (example "Check Breathing") and then
allow a preprogrammed time interval (e.g., 7 seconds) to check the
victim's breathing. The AED will next output voice/text prompts
instructing the rescuer to check the victim's pulse (example "Check
Pulse") and then allow a preprogrammed time interval (e.g., 10 sec)
for checking the victim's pulse. The AED will then enter a CPR
state where it outputs voice/text prompts instructing the rescuer
to start chest compressions (e.g., "If No Pulse, Start Chest
Compressions"). While in this CPR state, the chest compression
signal is received by `Detect & Increment Chest Compressions
Counter` function that detects chest compressions and counts them.
While the number of chest compressions is less than 5, the depth of
each detected compression is evaluated. If the depth of the
detected compression is not higher than 1'', the rescuer is
instructed to push harder on the victims chest by outputting "Push
Harder" voice/text prompts and return to `Detect & Increment
Chest Compression count` state. Else, if the depth of the detected
chest compression exceeds 1'', this depth is evaluated again. If
the depth of the detected compression is less than 1.5'', a check
is made for complete hand release to allow the victim's chest to
recoil. If the rescuer hand is released off the victim chest after
every compression, then the AED checks if the compression rate is
higher than a preprogrammed R1 rate. If the compression rate is
higher than R1, the AED output voice/text prompts indicating
effective compressions "Good Compressions". Else, the compression
rate is less than R1, the AED output voice/text prompts instructing
the rescuer to press faster and return to `Detect & Increment
Chest Compression count` state.
[0067] If the rescuer is not releasing the hands off the chest
after each compression, the AED instructs the user to release the
hands off the victim's chest after each compression by outputting
voice/text prompts "Release Hands Off Chest After Pushing", then
returns to `Detect & Increment Chest Compressions Count` state.
If the depth of the detected chest compression is greater than
1.5'', the AED instructs the rescuer to push on the victim chest
with less force by outputting the prompt "Push With Less Force",
then returns to `Detect & Increment Chest Compressions Count`
state. If the number of chest compressions exceeds 5, the device
instructs the rescuer to stop compressions and give the victim one
breath by outputting voice/text prompts "Stop Compressions, Give
One Breath", then checks if the CPR state time interval exceeds a
timer T1. If CPR state time interval is less than T1, the chest
compression counter is reset and the AED returns to `Detect &
Increment Chest Compressions Count` state. If the CPR state time
interval exceeds T1, the AED instructs the rescuer to activate the
EMS system by calling 911 and then the AED transitions to `Execute
3 Shock Sequence, Set T1` state. In this state, the "Pediatric ECG
Analysis Algorithm" is executed. If the first analysis detects a
non-shockable rhythm, the AED transitions to the CPR state for
another cycle of CPR. Else, if the first analysis detects a
shockable rhythm, the rescuer is advised to deliver a
defibrillation shock. Following the shock delivery a second
analysis is automatically initiated to determine whether the
defibrillation treatment was successful or not (i.e. the shockable
ECG rhythm has been converted to a normal or other non-shockable
rhythm). If this second analysis detects the continuing presence of
a shockable arrhythmia, the AED advises the user to deliver a
second defibrillation treatment.
[0068] A third ECG analysis is automatically initiated to determine
whether the second shock was or was not effective. If a shockable
rhythm persists, the rescuer is then advised to deliver a third
defibrillation treatment. Following the third defibrillator shock
or when any of the analyses described above detects a non-shockable
rhythm, the AED transitions to the CPR state for another cycle of
chest compressions and ventilation. Also In the `Execute 3 Shock
Sequence, Set T1` state, T1 is set to a preprogrammed value based
on the type of the detected rhythm: normal, asystole,
non-conductive, ventricular tachycardia or ventricular
fibrillation. For instance, the asystole and non-conductive rhythms
may require longer CPR periods than 1 minute in such case the
`Execute 3 Shock Sequence, Set T1` task will set the T1 to a
preprogrammed value appropriate for pediatric asystole or
non-conductive rhythms that may be longer than one minute. In the
case of an arrhythmia, the required CPR time may be only 1 minute
in such case the `Execute 3 Shock Sequence, Set T1` task will set
the T1 to a preprogrammed value appropriate for pediatric
arrhythmia rhythms that may be one minute. In the case of normal
rhythm, the required CPR time may be only 1 minute in such case the
`Execute 3 Shock Sequence, Set T1` task will set the T1 to a
preprogrammed value appropriate for pediatric pediatric rhythms
that may be one minute or longer.
[0069] If on the other hand, the AED detects adult defibrillation
pads on power-up, the AED will automatically start an adult rescue
protocol. FIG. 6b shows the details of one instance of the adult
rescue protocol. The AED will output voice/text prompts indicating
to the rescuer to check the victim's responsiveness (i.e., "Check
Responsiveness") and allow a preprogrammed time interval (i.e., 4
seconds) to expire to allow for checking the responsiveness before
moving to the next state. Next, the AED instructs the rescuer to
activate the EMS system by calling 911 and allow a preprogrammed
time interval (e.g., 4 seconds) to expire to allow someone call for
help before moving to the next state. The AED will next output
voice/text prompts instructing the rescuer to check breathing
(e.g., "Check Breathing") and then allow a preprogrammed time
interval (example: 7 seconds) to check breathing. The device will
next output voice/text prompts instructing the rescuer to check the
victim's pulse (e.g., "Check Pulse") and then allow a preprogrammed
time interval (e.g., 10 seconds) for the pulse check. The AED will
then transitions to `Execute 3 Shock Sequence, Set T1` state. In
this state, the "Adult ECG Analysis Algorithm" is executed. If the
first analysis detects a non-shockable rhythm, the AED will
transition to the CPR state. Else, if the first analysis detects a
shockable rhythm, the rescuer is advised to deliver a
defibrillation shock.
[0070] Following the shock delivery a second analysis is
automatically initiated to determine whether the defibrillation
treatment was successful or not (i.e. the shockable ECG rhythm has
been converted to a normal or other non-shockable rhythm). If this
second analysis detects the continuing presence of a shockable
arrhythmia, the AED advises the user to deliver a second
defibrillation treatment. A third ECG analysis is automatically
initiated to determine whether the second shock was or was not
effective. If a shockable rhythm persists, the rescuer is then
advised to deliver a third defibrillation treatment. Following the
third defibrillator shock or when any of the analyses described
above detects a non-shockable rhythm, the device transition to the
CPR state for another cycle of CPR. Also In the `Execute 3 Shock
Sequence, Set T1 state, T1 is set to a preprogrammed value based on
the type of the detected rhythm: normal, asystole, non-conductive,
ventricular tachycardia or ventricular fibrillation. For instance,
the asystole and non-conductive rhythms may require longer CPR
periods than 1 minute in such case the `Execute 3 Shock Sequence,
Set T1` task will set the T1 to a preprogrammed value appropriate
for adult asystole or non-conductive rhythms that may be longer
than one minute. In the case of an arrhythmia, the required CPR
time may be only 1 minute in such case the `Execute 3 Shock
Sequence, Set T1 task will set the T1 to a preprogrammed value
appropriate for adult arrhythmia rhythms that may be one minute. In
the case of normal rhythm, the required CPR time may be only 1
minute in such case the `Execute 3 Shock Sequence, Set T1 task will
set the T1 to a preprogrammed value appropriate for adult rhythms
that may be one minute or longer. Upon entering the CPR state, the
AED outputs voice/text prompts instructing the rescuer to start
chest compressions (example "If No Pulse, Start Chest
Compressions"). While in this CPR state the chest compression
signal is received by `Detect & Increment Chest Compressions
Counter` function that detects chest compressions and counts them.
While the number of chest compressions is less than 15, the depth
of each detected compression is evaluated. If the depth of the
detected compression is not higher than 1.5'', the rescuer is
instructed to push harder on the victims chest by outputting "Push
Harder" voice/text prompts and return to `Detect & Increment
Chest Compression count` state. Else, if the depth of the detected
chest compression exceeds 1.5'', this depth is evaluated again. If
the depth of the detected compression is less than 2'', a check is
made for complete hand release. If the rescuer hand is released off
the victim chest after every compression to allow for complete
chest recoil, then the AED checks if the compression rate is higher
than a preprogrammed R1 rate. If the compression rate is higher
than R1, the AED output voice/text prompts indicating effective
compressions "Good Compressions". Else, the compression rate is
less than R1, the AED output voice/text prompts instructing the
rescuer to press faster and return to `Detect & Increment Chest
Compression count` state.
[0071] If the rescuer is not releasing the hands off the chest
after each compression, the device instructs the user to release
the hands off the victim's chest after each compression to provide
more effective CPR by outputting voice/text prompts "Release Hands
Off Chest After Pushing", then returns to `Detect & Increment
Chest Compressions Count` state. If the depth of the detected chest
compression is greater than 3'', the device instructs the rescuer
to push on the victim chest with less force by outputting the
prompt "Push With Less Force", then checks if compression rate is
higher than a preprogrammed R1 rate. If the compression rate is
higher than R1, the AED output voice/text prompts indicating
effective compressions. Else, the compression rate is less than R1,
the AED output voice/text prompts instructing the rescuer to press
faster. If the number of chest compressions exceeds 15, the device
instructs the rescuer to stop compressions and give the victim two
breaths by outputting voice/text prompts "Stop Compressions, Give
Two Breaths", then checks if the CPR state time interval exceeds a
selected timer T1.
[0072] If CPR state time interval is less than T1, the chest
compression counter is reset and the device returns to `Detect
& Increment Chest Compressions Count` state. If the CPR state
time interval exceeds T1, the AED will transition to `Execute 3
Shock Sequence, Set T1 state.
[0073] FIG. 12 shows an example of a AED Arrhythmia processing flow
diagram. Since the pediatric QRS is narrower and the heart faster
than adult, the QRS detection system can be tailored to be more
sensitive to the ECG signal. The flow diagram also shows that the
arrhythmia classification logic and shock decision logic can be
altered to improve the specificity and sensitivity.
[0074] In the Signal Conditioning block, the ECG signal is band
passed and notch filtered to remove baseline offsets, high
frequency noise, and line noise frequency noise. The noise
Detection block performs baseline, motion, high frequency, muscle,
and saturation noise detections and flags the ECG Signal status
data accordingly.
[0075] In the QRS detection block, the processing produces a QRS
detection signal by performing a QRS based matched filter on the
filtered ECG data. The type of processing performed is dependant on
the Processing Mode Setting (reference FIG. 13).
[0076] Once the location of the QRS is detected in the signal
stream, the QRS Detection Block will process the signal around the
QRS detection to determine specific measurements such as R-R
interval, QRS width, QRS area, and other features which will
support classification of the QRS complex and its underlying
rhythm. The Rhythm Measurement block will perform analysis on the
QRS measures and ECG signal to produce rhythm based measures
required for rhythm classification. The Rhythm Determination and
Shock Determination Decision Logic block will process the QRS
detection and rhythm data to classify the ECG rhythm and make a
shock versus no shock decision. Many beat and rhythm classification
techniques are know in the art and include heuristic logic,
morphological analysis, expert system analysis, and statistical
clustering techniques. The outputs from the Rhythm Determination
and Shock Determination Decision Logic block are used by the AED to
shock the victim (fully automatic AED) or notify the user to
deliver a shock (semi-automatic AED) or begin other interventions
such as CPR.
[0077] FIG. 13 shows an example of the use of mode specific
processing to enhance QRS detection. In the PEDI Mode selection
block, the matched filter characteristics are chosen based on the
Processing Mode setting (Adult or Pediatric) to produce an optimal
detection signal for that class of patients. A threshold detection
scheme is used to determine the location of the QRS complexes in
the detection signal. A threshold system is utilized which has been
optimized for use with the respective QRS matched filter. The QRS
Detection Selection block determines whether to perform QRS
Measurements (QRS Detected) or perform an Asystole Check (QRS Not
Detected). The Asystole check will process a detection timeout,
adjust detection thresholds, and notify the target system if an
asystole state is present.
[0078] FIG. 14 shows an example of the use of mode specific
processing to enhance the rhythm classification logic and shock
decision determination. The PEDI Mode Selection block chooses which
Patient Mode Rhythm Logic to process. Rhythm classification logic
can be implemented in a number of ways, heuristic (if-then-else)
rules, feature cluster analysis, fuzzy system analysis, neural
networks, Bayesian probabilistic system analysis, etc. The
Shockable Rhythm Selection block selects the appropriate process
flow based on the Shock decision. The No Shock Decision block
notifies the defibrillator system to take the appropriate actions
such as display and audibly announce the non-shockable rhythm
analysis result. A shockable decision will produce a charging of
the defibrillator and a delivery of therapy (automatic
defibrillator) or a prompt to the user for delivery of energy
(semi-automatic defibrillator).
[0079] FIG. 15 and FIG. 16 are simple examples adult and pediatric
AED arrhythmia logic tables. The rhythm classifications in column 1
are satisfied when all of the rules stated in columns 2-6 are met
and the respective shock decision is listed in the last column. The
examples show that the shockable versus non-shockable decision can
come from specific adult or pediatric rhythm classification logic.
The various limits, rules, or other population specific logic
systems are tuned (or trained) from adult and pediatric ECG signal
databases, respectively.
[0080] Referring to FIG. 7, the cover 12 is provided with a
detection means for determining if the patient's shoulders have
been properly positioned on the cover 12. Two photoelectric sensors
156, 157 are used to determine if the cover has been placed
underneath the patient's back. The sensors 156, 157 are located
along the acute edge of the cover 12, with one facing inward and
one facing outward with the cable 155 providing both power to the
sensors 156, 157 as well as detection of the sensor output. If the
cover 12 is upside down, the inner sensor 156 will measure a higher
light level than the outer sensor 157; if the cover has been placed
with the acute edge facing toward the top of the patient's head,
then the outer sensor 157 will measure higher than the inner sensor
156 and will also exceed a pre-specified level. In the case of a
properly positioned cover, both inner 156 and outer sensor 157
outputs will be below a pre-specified level. In another embodiment,
the detections means is provided by a pressure sensor 158 located
underneath the cover decal. The pressure sensor 158 can be used to
measure the thoracic weight of the victim. Based on the measured
weight, a table lookup can be generated, determining the victim's
approximate age as well as the optimal defibrillation energies to
provide.
[0081] Thus, when a person collapses and a caregiver suspects that
the person is in cardiac arrest, the caregiver first gets the
defibrillator and turns the power on 102. If the unit passes its
internal self tests, and is ready for use, this will be indicated
by indicator 17. Next, the defibrillator prompts the caregiver with
an introductory audio message, e.g., "Stay calm. Listen
carefully."
[0082] Shortly thereafter, the defibrillator will prompt the
caregiver with an audio message indicating that the caregiver
should check the patient for responsiveness. Simultaneously, the
LED 56 adjacent graphic 42 will light up, directing the caregiver
to look at this graphic. Graphic 42 will indicate to the caregiver
that she should shout "are you OK?" and shake the person in order
to determine whether the patient is unconscious or not.
[0083] After a suitable period of time has elapsed (e.g., 2
seconds), if the caregiver has not turned the defibrillator power
off (as would occur if the patient were responsive), the
defibrillator will give an audio prompt indicating that the
caregiver should call for help. Simultaneously, the LED adjacent
graphic 42 will turn off and the LED adjacent graphic 43 will light
up, directing the caregiver's attention to graphic 43. Graphic 43
will remind the caregiver to call emergency personnel, if the
caregiver has not already done so.
[0084] After a suitable interval has been allowed for the caregiver
to perform the prior step (e.g., 2 seconds) the defibrillator will
give an audio prompt indicating that the caregiver should open the
patient's airway and check whether the patient is breathing. The
LED adjacent graphic 43 will turn off, and the LED adjacent graphic
44 will light up, directing the caregiver's attention to graphic
44, which shows the proper procedure for opening a patient's
airway. This will lead the caregiver to lift the patient's chin and
tilt the patient's head back. The caregiver may also position an
airway support device under the patient's neck and shoulders, if
desired, as discussed below with reference to FIGS. 9a, 9b. The
caregiver will then check to determine whether the patient is
breathing.
[0085] After a suitable interval (e.g., 15 seconds), the
defibrillator will give an audio prompt indicating that the
caregiver should check for signs of circulation, the LED adjacent
graphic 44 will turn off, and the LED adjacent graphic 45 will
light up. Graphic 45 will indicate to the caregiver that the
patient should be checked for a pulse or other signs of circulation
as recommended by the AHA for lay rescuers.
[0086] After a suitable interval (e.g., 5 to 7 seconds), the
defibrillator will give an audio prompt indicating that the
caregiver should attach electrode assembly 16 to the patient, the
LED adjacent graphic 45 will turn off, and the LED adjacent graphic
46 will light up. Graphic 46 will indicate to the caregiver how the
electrode assembly 16 should be positioned on the patient's
chest.
[0087] At this point, the LED adjacent graphic 47 will light up,
and the defibrillator will give an audio prompt indicating that the
patient's heart rhythm is being analyzed by the defibrillator and
the caregiver should stand clear. While this LED is lit, the
defibrillator will acquire ECG data from the electrode assembly,
and analyze the data to determine whether the patient's heart
rhythm is shockable. This analysis is conventionally performed by
AEDs.
[0088] If the defibrillator determines that the patient's heart
rhythm is not shockable, the defibrillator will give an audio
prompt such as "No shock advised". The LEDs next to graphics 48 and
49 will then light up, and the defibrillator will give an audio
prompt indicating that the caregiver should again open the
patient's airway, check for breathing and a pulse, and, if no pulse
is detected by the caregiver, then commence giving CPR. Graphics 48
and 49 will remind the caregiver of the appropriate steps to
perform when giving CPR.
[0089] Alternatively, if the defibrillator determines that the
patient's heart rhythm is shockable, the defibrillator will give an
audio prompt such as "Shock advised. Stand clear of patient. Press
treatment button." At the same time, the heart 54 and/or hand 52
will light up, indicating to the caregiver the location of the
treatment button. At this point, the caregiver will stand clear
(and warn others, if present, to stand clear) and will press the
heart 54, depressing the treatment button and administering a
defibrillating shock (or a series of shocks, as determined by the
defibrillator electronics) to the patient.
[0090] Referring to FIG. 11, in some implementations, a means is
provided of detecting the relative lateral positions of the apex
electrode 255 and the sternum electrode 254. In one implementation,
magnetic Hall Effect sensors 251 are located such that when
activated by the magnet 253 located within the apex electrode 255
the signal generated by the Hall effect sensor 251 indicates the
relative lateral location of the electrodes. Using known
anthropometrics, the thoracic girth can be estimated as well as
patient age and defibrillation energy levels. The relative lateral
positions of the electrodes can be determined using a linear
encoder commonly used in digital calipers thus providing an
accurate measurement of girth. The encoder may be an optical
encoder or a magnetic based encoder.
[0091] The cover 12 of the AED may include a decal on its
underside, e.g., decal 200 shown in FIG. 10. Decal 200 illustrates
the use of the cover as a passive airway support device, to keep
the patient's airway open during resuscitation. Graphic 202 prompts
the caregiver to roll the patient over and place cover 12 under the
patient's shoulders, and graphic 204 illustrates the proper
positioning of the cover 12 under the patient to ensure an open
airway.
[0092] While such a graphic is not included in the decal shown in
FIG. 5, the decal 40 may include a graphic that would prompt the
user to check to see if the patient is breathing. Such a graphic
may include, e.g., a picture of the caregiver with his ear next to
the patient's mouth. The graphic may also include lines indicating
flow of air from the patient's mouth.
[0093] Many other implementations of the invention other than those
described above are within the invention, which is defined by the
following claims.
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