Fully discharging phases. A new approach to biphasic waveforms for external defibrillation

Area of Science:

• Cardiovascular Research
• Biomedical Engineering
• Electrophysiology

Background:

• Single-capacitor biphasic waveforms have limitations in voltage and pulse width dependent on phase-1 characteristics.
• Utilizing two separate output capacitors can overcome these limitations, potentially lowering defibrillation thresholds.
• Previous research suggested optimal tilt angles exceeding 70%.

Purpose of the Study:

• To determine an optimal biphasic waveform by using two separate, fully discharging capacitors (95% tilt).
• To investigate the impact of phase-1 and phase-2 capacitor combinations on defibrillation efficacy.

Main Methods:

• Two external defibrillation studies were conducted in a pig ventricular fibrillation model.
• Waveforms were generated using combinations of different phase-1 and phase-2 capacitor values.
• Defibrillation efficacy was assessed based on stored energy and voltage requirements.

Main Results:

• Biphasic waveforms with a phase-2 capacitor at 1/3 of the phase-1 capacitor generally showed higher defibrillation efficacy.
• Optimal combinations for defibrillation were found to be 60/20 and 60/30 microfarads.
• Phase-2 capacitor size was more critical for a 30-microfarad phase-1 capacitor than for a 60-microfarad one.

Conclusions:

• Phase-2 capacitor size significantly influences defibrillation energy reduction in biphasic waveforms when using two separate, fully discharging capacitors.
• The findings provide insights into optimizing biphasic waveform design for external defibrillation.