Date of Award

Summer 1990

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Biomedical Engineering

First Advisor

Jeutter, Dean C.

Second Advisor

Avitall, Boaz

Abstract

Recent literature reports have described reduced defibrillation energy requirements when using truncated biphasic defibrillation waveforms as compared to monophasic defibrillation waveforms. In an attempt to address the question, ''What is significant about biphasic defibrillation waveforms? An experimental defibrillator which incorporates a new type of biphasic waveform was designed and tested. The experimental defibrillator is a high voltage RC circuit and delivers a waveform which has smoothed leading and trailing edges. A single transient occurs at the switch over between the two phases (Figure l). The experimental defibrillator is capable of delivering biphasic shocks of 5 msec duration, with peak positive and negative amplitudes of greater then 500 volts. The circuit is capable of delivering in excess of 6 Joules into a 50 ohm load. Defibrillation energy requirements for both the experimental defibrillator and a defibrillator (ECD II, supplied by cardiac Pacemakers Incorporated) delivering a conventional biphasic truncated exponential waveform (Figure 2) were compared in seven canine experiments. Energy delivery was measured using a 12 Bit analog to digital converter, installed in an HM compatible personal computer, measuring voltage and current delivered to the load, at a sampling rate of 50 Khz per channel. The mean energy required for 50% successful defibrillation was 1.37 +/ - 0.07 Joules with the experimental defibrillator, and 1.70 +/- 0.03 Joules with the ECD. These results suggest that the rapid voltage change at phase reversal could play the most important role in defibrillation, and that rapid leading and trailing edges are unimportant to biphasic waveforms.

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