Optimal Small-Capacitor Biphasic Waveform for External Defibrillation

Abstract

Background-Biphasic waveforms have been reported to be more efficacious than monophasic waveforms for external defibrillation. This study examined the optimal phase-1 tilts and phase-2 leading-edge voltages with small capacitors (60 and 20 F) for external defibrillation. We also assessed the ability of the "charge-burping" model to predict the optimal waveforms. Methods and Results-Two groups of studies were performed. In group 1, 9 biphasic waveforms from a combination of 3 phase-1 tilt values (30%, 50%, and 70%) and 3 phase-2 leading-edge voltage values (0.5, 1.0, and 1.5 times the phase-1 leading-edge voltage, V 1 ) were tested. Phase-2 pulse width was held constant at 3 ms in all waveforms. Two separate 60-F capacitors were used in each phase. The energy value that would produce a 50% likelihood of successful defibrillation (E 50 ) decreased with increasing phase-1 tilt and increased with increasing phase-2 leading-edge voltage except for the 30% phase-1 tilt waveforms. In group 2, 9 waveforms were identical to the waveforms in group 1, except for a 20-F capacitor for phase 2. E 50 decreased with increasing phase-1 tilt. Phase-2 leading-edge voltage of 1.0 to 1.5 V 1 appeared to minimize E 50 for phase-1 tilt of 50% and 70% but worsened E 50 for phase-1 tilt of 30%. There was a significant correlation between E 50 and residual membrane voltage at the end of phase 2, as calculated by the charge-burping model in both groups (group 1, R 2 ϭ0.47, PϽ0.001; group 2, R 2 ϭ0.42, PϽ0.001). Conclusions-The waveforms with 70% phase-1 tilt were more efficacious than those with 30% and 50%. The relationship of phase-2 leading-edge voltage to defibrillation efficacy depended on phase-2 capacitance. The charge-burping model predicted the optimal external biphasic waveform. (Circulation. 1998;98:2487-2493.)

Automatic adjustment of biphasic pulse duration in transthoracic defibrillation

“…Similar V m modelling was used by Yamanouchi et al [7] , but for selecting leading voltages, capacitance s and tilts of biphasic wave forms.…”

The Strength‐Duration Relationship of Monophasic Waveforms with Varying Capacitance Sizes in External Defibrillation

“…Three adhesive pad electrodes and an RV transvenous defibrillation lead were connected to an external defibrillator custom made by SurVivaLink Corp (Minneapolis, MN, USA). The function in this external defibrillator was described in more detail in our previous publication 6 . Ventricular fibrillation (VF) was induced by 60 Hz AC (15 V) for 3 seconds between the RV defibrillation lead and the left upper pad electrode.…”

“…A detailed description of animal preparation and surgical procedures has been reported in our previously publications. 6,15,16 Briefly, the pig was ventilated with room air supplemented with oxygen through a Drager SAV respirator (North PACE, Vol. 26 American Drager, PA, USA) which was adjusted as needed to maintain normal arterial blood gases.…”

“…The function in this external defibrillator was described in more detail in our previous publication. 6 Ventricular fibrillation (VF) was induced by 60 Hz AC (15 V) for 3 seconds between the RV defibrillation lead and the left upper pad electrode. After sustained VF lasting 10 seconds, one of the test waveforms was delivered between the right upper pectoral pad electrode and the apical pad electrode at end-expiration phase.…”

“…Defibrillation threshold (DFT) for external shocks depends upon the shape of the defibrillation waveforms 1–6 as well as electrode pad size, 7,8 shock polarity, 9 and the sequence of shock pulse 10 . Since defibrillation waveforms are determined by the waveform time constant, 11 capacitance size and interelectrode resistance may play an important role in the determination of defibrillation efficacy 12 .…”