The various types of medical defibrillator include: the standard manual defibrillator, manual internal defibrillators, the automatic implanted cardiac defibrillator (AICD), the semiautomatic automated external defibrillator (AED) and fully automated AEDs. An AED, whether semiautomatic or fully automated, can be monophasic or biphasic. Monophasic AEDs send a single shock from the negative pad or paddle to the positive pad or paddle, and biphasic AEDs send a shock in one direction and then in the other. They also have the ability to measure the impedance or resistance and can adjust the amount of energy according to the need. More energy is used when impedance is high, and less is used when it is low, resulting in a more efficient use of energy overall.
It is believed that biphasic AEDs might help lower any risk of damaging the heart, but this type of medical defibrillator has not been shown to raise survival rates. Other advantages of the biphasic AED include its smaller size and lighter weight. An AED is the only medical defibrillator that laypeople can be trained and permitted to use; all other types must be operated by a healthcare provider. They also figure among the equipment of emergency medical technicians (EMTs) and paramedics, and they frequently are found in public buildings and places such as hotels, schools, sports arenas and airplanes.
The manual medical defibrillator is exclusively used in the hospital setting by a healthcare provider such as a medical doctor or cardiologist. This type of defibrillator requires more knowledge to use than an AED. For example, the operator must be able to interpret the heart rhythm that appears on a screen and decide whether it is shockable. He or she must then lubricate paddles, charge them and deliver the shock to the patient's chest.
The medical defibrillator known as the AICD is surgically implanted under the patient's skin. It is designed to detect life-threatening cardiac dysrhythmia and intervene by delivering one or more shocks to remedy the problem. Most patients find being shocked by an AICD very unnerving and often need much encouragement to remain calm during and after the shocks.
Regardless of the type of medical defibrillator in question, they are all designed to correct cardiac arrhythmia, which is a medical term for an abnormal heartbeat or rhythm. The heart has an electrical system of its own that can become corrupted, creating an abnormal heartbeat. Some abnormal rhythms are shockable and some are not. Use of a medical defibrillator, however, plays a very vital role in the "chain" of survival for cardiac arrest patients. A medical defibrillator does not take the place of cardiopulomonary resuscitation (CPR).