Vaporization
The cutting of tissue by electrical current is due to the vaporization of cells. This is a special and interesting case, since the actual mechanisms of cutting remain controversial. As with the other tissue effects, the cutting action of electrical current is a product of current density. A dampened (coagulating) current can be made to divide tissue (albeit at the expense of great lateral thermal damage) by increasing the power or decreasing the electrode size, and an undamped, sinusoidal current (cutting) will produce coagulation if the current density is low, and the electrode contacts tissue. Every gynecologist who has performed tubal sterilization with the Wolf bipolar unit has made use of cutting current to produce coagulation of tissue.
Cutting tissue requires that a spark be present between the electrode and the tissue. An arc may be present in coagulating currents, and is necessary in fulguration. In the formation of an arc, little happens until a sufficient voltage is reached to allow the electrons to traverse the air gap between electrode and tissue. When this voltage is reached, electrons jump across the gap, causing ionization of the air molecules along the path of the spark. This ion path presents a low resistance pathway to the tissue, so long as the plasma (gas composed of ionized molecules) cloud is maintained. In a cutting current, the rapidly repetitive peak voltages occur before the plasma cloud can dissipate, so that each spark tends to follow the same pathway, maintaining ionization of the air along the spark path and striking the tissue at the same spot, generating a locally high current density. A dampened current reaches higher peak voltages than does an undamped one, but the peaks are separated by a longer period of time so that the plasma cloud dissipates between each peak. The low resistance path to tissue is lost, and the charring and dehydration of the tissue caused by the previous spark cause a locally higher resistance, decreasing the likelihood of a subsequent spark striking the same spot. The net result is a lower current density, and coagulation. McLean4 demonstrated the essential difference between the arcs used in cutting and the other effects by photographing the sparks caused by damped and undamped currents and found that the former caused a broad, brushlike spark (low current density), while the latter caused a tight, pencil-like arc (high current density).
It is thought that the cutting effect on tissue stems from the extremely high localized current density causing boiling of the intracellular water, and exploding the cells.Lateral damage is minimized by heat being carried off by the steam.
Jinhua Huacheng Medical Appliance Co.,Ltd.
Manufactuer of disposable medical products: Electrosurgical pencil,grounding plate,skin stapler and ECG electrode
