User manual

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Fig. 3.5: Equivalent electrical diagram of a final stage of a monophasic defibrillator with

damp-shaped defibrillation pulse with delay. Position 1 - charging of the capacitors, position

2 - discharging of the capacitors past the delay line (defibrillation pulse DMT).

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Synchronizedcardioversion

 Synchronized cardioversion, or simply a cardioversion, is basically a synchronized

defibrillation, which uses lower energy values of the defibrillation pulse. Typically, the

synchronized cardioversion starts at the discharge value of 50 J in external biphasic

cardioversion and at 5 J in internal biphasic cardioversion. The defibrillator senses the ECG

(see Chapter 2) signal and calculates the distance of the R waves (the so called R-R interval),

which means the distance of subsequent QRS complexes. Cardioversion is most often used in

case of atrial flutter, atrial fibrillation and ventricular tachycardia. The applied discharge

depolarizes the entire heart muscle, thus interrupting the so called reentry circuit.

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Transcutaneousstimulation(pacing)

 At present, most external defibrillators can perform the so called transcutaneous

(external) stimulation besides defibrillation (TEPs - Transcutaneous External Cardiac Pacing).

Transcutaneous stimulation is used in acute arrhythmias, in case of some forms of

bradycardias and tachycardia (more than 90 beats/min, adult patients). The stimulation may

be carried out in the on-demand mode or in the fix-rate mode. Single-use electrodes are used

for the stimulation, with large surface area, the so called “pads”. The active surface of

electrodes for transcutaneous stimulation must not be less than 75 cm

for adult patients and

20 cm

for child patients.

In the on-demand mode (bradycardia, asystole), the stimulator is inactive as long as

the patient has his own cardiac activity with frequency higher than that set up on the simulator

(mostly 30-180 beats/min). The stimulation pulses are only applied in case the heart

frequency decreases or if the heart stops beating. The heart’s activity is monitored via the