A monophasic-damped sine wave provides a high voltage and high peak current over a short time. A monophasic-truncated exponential wave responds to impedance by delivering the energy over more time. A biphasic-truncated exponential wave also delivers energy over time, but the energy is reversed at a predetermined time. Full discussion of the benefits of the various waveforms is beyond the scope of this article. Representative AEDs Several companies market AEDs.
Available units differ slightly in size, cost, technology, and use.
The manufacturers and independent testers have extensively evaluated the technology differences, and no single company's AED has become a standard. The most elaborate version has an ECG display and manual override that allows the rescuer to shock based on the display. Other manufacturers have chosen not to incorporate the ECG display. The ForeRunner delivers 150 J in a biphasic waveform. It has voice prompts and can record, on an internal card, voice, rhythm, and shocks delivered.