ZOLL M Series Defibrillator Rev R - Manual (Page 142)

M Series Service Manual
132
The High Voltage module controls the monitoring, charging, and internal discharges of the defibrillator capacitor. The
Bridge module controls capacitor discharge, including waveform polarity control, patient current and voltage
monitoring during discharge and real-time control over defibrillator internal impedance to create the rectilinear
waveshape. The main CPU controls the waveform timing and resistor switching performed by the Bridge Module
based upon measured patient transthoracic impedance.
The Biphasic Bridge Assembly is constructed as two printed wire board assemblies (PWBAs) containing the power
and isolation circuits required to deliver a biphasic defibrillation pulse. These boards produce a defibrillation pulse
consisting of a positive current pulse followed by a negative current pulse. The positive portion of the pulse is shaped
to be rectilinear by switching resistors in series with the patient to compensate for droop in the capacitor voltage as it
delivers energy to the patient load.
The ZOLL Biphasic units produce a rectilinear waveform whose shape remains essentially constant from patient to
patient. The rectilinear biphasic waveform consists of a 6 millisecond, essentially constant current first phase followed
by a 4 millisecond, truncated exponential second phase. The first and second phases of the defibrillation waveform are
of opposite polarity and their amplitudes vary based on the user selected therapeutic energy level. The initial amplitude
of this waveform’s second phase is approximately equal to the first phases’s final amplitude. This wavefrom has an
integrated patient impedance measurement sensing pulse at the beginning of the waveform. The positive and negative
phases are separated by 100
sec
Electronics and software control the shape of the waveform’s first phase and compensate for different transthoracic
impedances to maintain an essentially constant current throughout the first phase.When the highest energy setting is
selected and patient impedance exceeds 85 ohms, the first phase of the waveform will droop. All other waveform
parameters (phase duration, inter-phase delay and integrated impedance measurement sensing pulse) remain the same.