LIFEPAK CR Plus and LIFEPAK EXPRESS Defibrillator Operating Instructions B-1
©2009-2014 Physio-Control, Inc.
Appendixes
Shock Advisory System
OVERVIEW OF THE SHOCK ADVISORY SYSTEM
The Physio-Control patented Shock Advisory System is an ECG analysis system built into the
LIFEPAK CR Plus and LIFEPAK EXPRESS defibrillators that advises the operator if it detects a
shockable or nonshockable rhythm. This system makes it possible for individuals not trained to interpret
ECG rhythms to provide potentially-lifesaving therapy to victims of ventricular fibrillation or pulseless
ventricular tachycardia. The Shock Advisory System contains the following features:
• Electrode contact determination
• Automated interpretation of the ECG
• Operator control of shock therapy
• Motion detection
Electrode Contact Determination
The victim's transthoracic impedance is measured through the defibrillation electrodes. If the baseline
impedance is higher than a maximum limit, it is determined that the electrodes are not in sufficient
contact with the victim or not properly connected to the defibrillator. ECG analysis and shock delivery
are inhibited. The operator is advised to connect electrodes any time electrode contact is inadequate.
Automated Interpretation of the ECG
The Shock Advisory System is designed to recommend a shock if it detects the following:
•
Ventricular fibrillation — with a peak-to-peak amplitude of at least 0.08 mV
•
Ventricular tachycardia — defined as having a heart rate of at least 120 beats per minute, QRS
width of at least 0.16 seconds, and no apparent P waves.
Pacemaker pulses may prevent advisement of an appropriate shock, regardless of the victim’s
underlying rhythm. The Shock Advisory System is designed to recommend no shock for all other ECG
rhythms including pulseless electrical activity, idioventricular rhythms, bradycardia, supraventricular
tachycardias, and normal sinus rhythms.
ECG analysis is performed on consecutive 2.7 second segments of ECG. The analysis of two out of
three segments must agree before a decision (
SHOCK ADVISED or NO SHOCK ADVISED) is made.
The Shock Advisory System performance for adult, pacemaker and pediatric ECGs is summarized in
the following table.
Table B-1 Shock Advisory System Performance Table for Adult ECGs
Rhythm Class
ECG Test
1
Sample Size
Performance Goal
2,
3
Observed Performance
Sensitivity or Specificity [LCL]
4
Shockable:
coarse VF
168 >90% sensitivity 100.0% [98.6%]
Shockable:
shockable VT
65 >75% sensitivity 84.6% [77.3%]
Nonshockable:
NSR
144 >99% specificity for
NSR (AHA)
100.0% [98.4%]
Nonshockable:
asystole
43 >95% specificity 100.0% [94.8%]
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