What is the Difference Between a Biphasic and Monophasic Defibrillator

How a Defibrillator Works00:00:00

A defibrillator delivers a high-energy electric shock to the heart to depolarize all cells simultaneously, restoring a normal heart rhythm. It's used for cardiac arrhythmias not treatable by medication, such as ventricular fibrillation, and for conditions like ventricular tachycardia and supraventricular tachycardia, which is known as cardioversion.

Types of Defibrillation00:01:11

Defibrillation can be external, using paddles on the chest; internal, where paddles are applied directly to the heart during surgery; or through implantable cardioverter-defibrillators (ICDs), which are devices implanted in the pectoral region with electrodes in the heart to deliver shocks for immediate arrhythmia management.

Monophasic vs. Biphasic Defibrillators00:02:21

Monophasic defibrillators deliver a shock in only one direction, which may not depolarize all myocardial cells effectively. Biphasic defibrillators deliver a shock first in one direction, then reverse polarity, ensuring more complete depolarization and requiring less energy. Older monophasic units typically have a maximum energy of 360 joules, while modern biphasic units often have a maximum of 200 joules, with some capable of higher for resistant cases.

Physics and Safety of Defibrillation00:05:00

Defibrillators typically use high voltages, often around 2,500 volts DC. They charge a high-value capacitor, which is why a charging process is observed. Safety precautions, such as shouting 'all clear' and ensuring good skin conductivity with electrolyte jelly, are crucial to prevent accidental shocks to personnel and skin burns to the patient. Modern defibrillators can sense thoracic impedance to ensure proper delivery of the set energy and synchronize the shock to the R-wave during cardioversion.