Table of Contents
Advertisement
Rhythm detection system
12
Rhythm detection system
The rhythm detection system on the PRIMEDIC™ HeartSave analyses the patient's
ECG and supports it if the unit detects a shockable or non-shockable rhythm.
Operator control of the defibrillation shock therapy:
Ascertaining the electrode contact
Automatic evaluation of the ECG
Operator control of the defibrillation shock therapy
Ascertaining the electrode contact
The transthoracic impedance of the patient is measured by the defibrillation electrodes.
If the baseline impedance is greater that the maximum critical value, then the device
determines whether the electrodes are not in good enough contact with the patient or
if they are not connected properly to the device. ECG analysis and dispensation of
defibrillation shocks are therefore prevented. The voice output says "Check electrodes"
if the contact of the electrodes is insufficient.
Automatic Interpretation of the ECG
The rhythm detection system of the device is designed to recommend defibrillation
when the system detects a shockable rhythm.
With all other ECG rhythms, including asystolia and normal sinus rhythms, the rhythm
detection system in the device does not recommend defibrillation.
Operator control of the output of defibrillation shocks
The device's rhythm detection system triggers automatic charging of power if the
device ascertains a shockable cardiac rhythm. Optical and acoustic messages are
emitted to show you that the device recommends giving a defibrillation shock. If a
defibrillation shock is recommended, you decide whether and when the shock is to be
given.
The Algorithm:
Observes the ECG rhythm across a continuous recording of 10 seconds, of which
7 seconds have been used for an initial diagnosis or to display the message "Shock
recommended."
Measures the symmetry of the ECG signal by several wave form factors and area
abive and below the moving average of the signal. Shockable ryhthms show
greater symmetry than non-shockable rhythms.
Measures the ratio of the signal energy content in a frequency band typical for
shockable rhythms and the total of the signal energy content. For shockable
rhythms the signal energy concentrates in a specific frequency band and its
fraction with respect to the total signal energy is higher.
Derives from these two signal processing steps two parameters and compares
them to a threshold. If both parameters drop below their respective threshold for a
specific amount of time, the device will rate the heart rhythm shockable. However,
if one of the parameters exceeds its higher threshold value, this shocking
recommendation is retracted.
Filters and measures artefacts and interference. If a specific artefact level is
exceeded no reliable signal analysis is possible and the heart rhythm is rated non-
shockable.
HeartSave AED / AED-M, 21212 / GB / E02
47
Advertisement
Table of Contents
