Operating instructions

LIFEPAK CR Plus Defibrillator Operating Instructions B-1
©2002–2005 Medtronic Emergency Response Systems, Inc.
Appendixes
Shock Advisory System
OVERVIEW OF THE SHOCK ADVISORY SYSTEM
The Shock Advisory System (SAS) is an ECG analysis system built into the LIFEPAK CR Plus
Defibrillator 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 SAS contains the
following features:
• Electrode contact determination
• Automated interpretation of the ECG
• Operator control of shock therapy
• Motion detection
Electrode Contact Determination
The patient'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 patient 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 patient’s
underlying rhythm. The SAS 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 LIFEPAK CR Plus Defibrillator SAS performance for adult, pacemaker and pediatric ECGs is
summarized in the following table.
Table B-1 LIFEPAK CR Plus Defibrillator SAS 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%]