Operating instructions

LIFEPAK 500 Automated External Defibrillator Operating Instructions A-3
©1996–2003 Medtronic Physio-Control Corp.
Shock Advisory System
Appendixes
Control of Shock Therapy
Operator Control of Shock Therapy
The Shock Advisory System causes the AED to charge automatically when it detects the presence of a
shockable rhythm. When a shock is advised, the operator remains in control of when the shock is
delivered.
Continuous Patient Surveillance System
The Continuous Patient Surveillance System (CPSS) automatically monitors the patient's ECG rhythm
for a potentially shockable rhythm while the electrodes are attached and the AED is turned on. CPSS is
not active during ECG analysis.
Motion detection is not active during the CPSS. Therefore, there is a chance that motion distortion in
the ECG rhythm may be interpreted by CPSS as a potentially shockable rhythm.
Motion Detection
The Shock Advisory System detects patient motion independent of ECG analysis. A motion detector is
designed into the LIFEPAK 500 AED.
MOTION DETECTION can be configured in the setup mode to be ON
or
OFF.
Motion can be caused by CPR, rescuer movement, patient movement, vehicle movement, or other
causes. If variations in the transthoracic impedance signal exceed a maximum limit, it is determined
that patient motion of some kind is present. ECG analysis is inhibited until the motion ceases. The
operator is advised any time motion is detected during an analysis by a displayed message, a voice
prompt, and an audible alert. If the motion does not cease within 20 seconds, analysis attempts will stop
until the operator presses the
ANALYZE button again. For LIFEPAK 500 AEDs without an ANALYZE
button, analysis restarts automatically. If the motion does cease within 20 seconds, ECG analysis
proceeds automatically.
There are two reasons why ECG analysis is inhibited when motion is detected:
1 Such motion may cause artifact in the ECG signal. This artifact can cause a nonshockable ECG
rhythm to look like a shockable rhythm. For example, chest compressions during asystole can look
like shockable ventricular tachycardia. Artifact can also cause a shockable ECG rhythm to look like a
nonshockable rhythm. For example, chest compressions during ventricular fibrillation can look like
an organized and, therefore, nonshockable rhythm.
2 The motion may be caused by a rescuer's interventions. To reduce the risk of inadvertently shocking
a rescuer, the motion alert prompts the rescuer to move away from the patient. This will stop the
motion and ECG analysis will proceed.