Page 137
Technical Data
12
User guide
Defibrillation Waveform
12.2
A
rt.
no.
: 0-48-
0227
Rev.:
g
DEFIGARD/PHYSIOGARD Touch 7
12.2.1
Shock Advisory System
The Shock Advisory System (SAS) validation test set consists of 17,803 ECG
waveforms coming from the PhysioNet databases [1]. These files (MIT-VFDB) are
subsets of the general PhysioNet databases recognised as standard in ECG tests.
PhysioNet databases are ECG Holter recordings with full diagnostic bandwidth [0.05
- 125] Hz. The bandwidth of the devices that recorded the signals is larger than that
of the
DEFIGARD
®
Touch 7
. However, when the analogue signals of the database are
run the the electrode connector, the rhythm detector signal-processing
characteristics are applied. Moreover, these signals are of appropriate length to allow
decisions to be made by the detector system.
The
DEFIGARD
®
Touch 7
SAS when configured as “Analysis with anteriority to ON”
uses a combination of algorithms which are launched in two-stages [4-6] to deliver a
shock advisory decision at minimal delay after actual CC stoppage. The SAS
configured as “Analysis with anteriority to OFF” starts a chest compression-free VF
detection at an analysis request, without trying to optimize hands-off time. In both
configurations, the SAS does not continue analyzing after a shock advised decision
is reached.
[2]: Automatic External Defibrillators for
Public Access Defibrillation :
Recommendations for Specifying and
Reporting Arrhythmia Analysis
Algorithm Performance, Incorporating
New Waveforms and Enhancing
Safety ; Circulation, 1997 ; 95 :1677-
1682.
[3]: Standard IEC 2010 60601-2-4, ed 3.
[4]: Shock advisory system with minimal delay trig-
gering after end of chest compressions: Accuracy
and gained hands-off time. Jean-Philippe Didon,
Vessela Krasteva, Sarah Ménétré, Todor Stoyanov,
Irena Jekova, Resuscitation 82S (2011) S8-S15
[5]: Circulation. 2011; 124: A219, Resuscitation Sci-
ence Symposium Abstracts, Best Original Resusci-
tation Science Poster Session, Abstract 219: Com-
bination of Algorithms to Decrease Preshock Pause
for Automated External Defibrillators. Jean-Philippe
Didon, Irena Jekova, Sarah Ménétré, Todor Stoy-
anov, Vessela Krasteva.
[6]: Circulation. 2010; 122: A253, Resuscitation Sci-
ence Symposium Abstracts, Best Original Resusci-
tation Science Poster Session, Abstract 253: Meth-
od for Minimal Delay Triggering of VF Detection
During Cardio Pulmonary Resuscitation. Jean-
Philippe Didon; Sarah Ménétré, Irena Jekova, Ves-
sela Krasteva. »
The validation test set database used to establish compliance with the AHA
requirements [2] and the IEC Standards [3] is independent from the one used to
develop the rhythm recognition detector.
The SAS validation test set contains the following ECG samples (see test sample size
in Table 1):
• coarse ventricular fibrillation (VF) (>200
μ
V peak-to-peak amplitude)
• shockable ventricular tachycardia (VT hi) (HR >150 bpm, rushes that last more
than 8s)
• asystole (
≤
100
μ
V peak-to-peak amplitude)
• normal sinus rhythm (NSR) (PQRS-T waves visible, HR 40-100 bpm)
• other organized rhythm (N) (includes all rhythms except those in other listed
categories)
For each test sample, in function of the expert rhythm annotation and the SAS
decision (shock/no shock), an interpretation table is built and shows the true positive
(correct classification of a shockable rhythm), true negative (correct classification of a
non-shockable rhythm), false positive (non-shockable rhythm incorrectly classified as
a shockable rhythm), false negative (shockable rhythm incorrectly classified as non-
shockable). Finally, the results of the detector performance are reported in terms of:
specificity-Sp (TN/(TN+FP)), true predictive value (TP/(TP + FP)), sensitivity-Se (TP/
(FN + TP)), false positive rate (FP/(FP + TN)).
Table 1:
DEFIGARD
®
Touch 7
SAS performance by rhythm category meets AHA
recommendations [2] and IEC Standards [3] for adult defibrillation on artefacts-free
MIT-VFDB signals:
Rhythms
Test sample
size
Performance goal Observed perfor-
mance
Shockable
Coarse VF
308
Sensitivity > 90% Meets [2-3]
VT hi
202
Specificity > 75% Meets [2-3]
Non Shockable
NSR
1023
Sensitivity > 99% Meets [2-3]
Asystole
4798
Sensitivity > 95% Meets [2-3]
Other rhythms
1425
Sensitivity > 95% Meets [2-3]
Total NS
7246
Sensitivity > 95% Meets [3]
