Common electrode configurations for devices with isolated circuits
There are several commonly used electrode configurations or circuit topologies:
With "bipolar" instruments the current is applied to the patient using a pair of similarly-sized electrodes. For example, special forceps, with one tine connected to one pole of the RF generator and the other tine connected to the other pole of the generator. When a piece of tissue is held by the forceps, the RF alternating polarity electrical current oscillates between the two forceps tines, heating the intervening tissue by the previously described synchronous oscillation of intracellular ions.
In monopolar configuration the patient is attached to the dispersive electrode, a relatively large metal plate or a flexible metalized plastic pad which is connected to the RF generator or electrosurgical unit (ESU). The surgeon uses a pointed or blade shaped electrode called the "active electrode" to make contact with the tissue and exert a tissue effect...vaporization, and its linear propagation called electrosurgical cutting, or the combination of desiccation and protein coagulation used to seal blood vessels for the purpose of Hemostasis. The electric current oscillates between the active electrode and the dispersive electrode with the entire patient interposed between the two. Since the concentration of the RF current reduces with distance from the active electrode the current density rapidly (quadratically) decreases. Since the rate of tissue heating is proportional to the square of current density, the heating occurs in a very localized region, only near the portion of the electrode, usually the tip, near to or in contact with the target tissue.
On an extremity such as a finger, there is limited cross-sectional area to disperse the current, a circumstance which might result in higher current density and some heating throughout the volume of the extremity.
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Jinhua Huacheng Medical Appliance Co.,Ltd.
Manufactuer of disposable medical products: Electrosurgical pencil,grounding plate,skin stapler and ECG electrode
