Every AEM instrument has a protective shield that is actively monitored by the AEM system throughout a procedure. This protective shield eliminates the risk of capacitive coupling to the patient by draining the energy away from the patient to the AEM monitor. If an insulation failure occurs, the AEM system actively drains the electrosurgical energy away from the patient through this protective shield. In addition the AEM system immediately shuts down the instrument power, similar to a circuit breaker (GFCI) in the electrical wiring of a house.
In every AEM instrument, the active electrode is surrounded by the primary insulation layer. The primary insulation layer withstands the high voltages of electrosurgery, ensuring effective use of the active electrode. The protective shield is a conductive tube that surrounds the primary insulation layer and active electrode. The shield conducts stray energy back to the generator, ensuring there is no chance of a stray energy burn to the patient. The outer insulation provides an additional layer of insulation for all AEM instruments.
What is Capacitive Coupling?
Capacitive coupling occurs when electrosurgical energy is transferred to the patient without direct contact with the active wire. The fundamental design of all laparoscopic instruments creates a large capacitor, which induces electrical current into the patient without ever contacting the patient’s body. The instrument’s insulation is intact and yet the patient is still burned due to the coupled energy. All monopolar instruments have dangerous levels of capacitive coupling.
What is Insulation Failure?
Insulation failure occurs when there is a hole in the insulation on the shaft of an instrument. This hole allows the full power of the electrosurgical generator to burn the patient in an unintended area.
Insulation failure is extremely common. 1 in 5 reusable instruments has a full thickness insulation failure. 1 in 33 disposable instruments has a failure right out of the package. 57% of insulation failures are not visible to the naked eye.*
This is a break in the instrument insulation, a defect beyond the control of even the most skilled surgeon. With the AEM® system, instrument insulation is monitored so that no instrument with a fault is used in surgery. Insulation failure occurs when insulation along the shaft of the active electrode breaks down and current ‘leaks’ from the instrument, burning nearby tissue. Insulation defects occur as a result of normal wear and tear, the stress of high voltages, the cleaning and sterilization process, and contact with other sharp instruments such as trocar cannula. The smaller the defect, the greater the hazard. Defects that are invisible to the naked eye can concentrate current density and cause severe burns to non-targeted tissue.
An electrical phenomenon whereby current passes through intact insulation. In the event that this type of energy reaches dangerous levels, the AEM monitor interrupts the power by shutting down the generator.
Capacitive coupling occurs when electrical current is induced from the active electrode to nearby conductive material through intact insulation.
In electrosurgery, the charge on the active electrode switches from positive to negative at a very high frequency. The rapidly varying electrical field around the active electrode can transfer high levels of electrical current to non-targeted tissue, causing severe burns.
The potential for capacitive coupling to occur is always present in monopolar electrosurgery.