User manual

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only, and to biphasic pulse (Fig. 3.2), when the direct current is lead past the heart muscle in

one direction during the first stage of the pulse, and in the other direction in the second stage.

Some defibrillators use triphasic or quadriphasic defibrillation pulses.

Fig. 3.2: Demonstration of biphasic depolarizing pulses (from the left: trapezoidal BTE and

damped with delay DBT).

Depending on the shape of the pulse (monophasic and biphasic), we divide the defibrillation

pulse to trapezoidal (exponential), damped (sine), and damped with delay.

The trapezoidal shape of the defibrillation pulse is given by the time limited

exponential discharge of the capacitor (tens of µF). Discharging of the capacitor is interrupted

via thyristors in a moment the selected energetic value contained in the stimulation pulse is

reached; see an equivalent diagram of such a circuit in Fig. 3.3.

Fig. 3.3: Equivalent electrical diagram of a monophasic defibrillator with trapezoidal

(exponential) defibrillation pulse. Position 1 - charging of the capacitor, position 2 -

discharging of the capacitor into the patient (defibrillation pulse), position 3 - fast discharge

of the capacitor (the MTE defibrillation pulse is interrupted upon reaching the selected

energy of the pulse).