Defibrillator - Wikipedia, the free encyclopedia: "Biphasic Defibrillation
Until recently, external defibrillators relied on monophasic shock waves. Electrical pulses are sent rapidly from one electrode to the other, only in one direction. Biphasic defibrillation, however, alternates the direction of the pulses, completing one cycle in approximately 10 milliseconds. Biphasic defibrillation was originally developed and used for implantable cardioverter-defibrillators. When applied to external defibrillators, biphasic defibrillation significantly decreases the energy level necessary for successful defibrillation. This, in turn, decreases risk of burns and myocardial damage. However, there is limited evidence to suggest that biphasic defibrillation is superior to monophasic defibrillators, although the small capacitor size required for the defibrillator can result in significant cost and size savings-- essential for the proliferation of Automated External Defibrillators."