The high-frequency electrosurgical unit itself must have a very complete and reliable safety guarantee system, which is the most basic condition to ensure the safety of patients and medical staff. Therefore, the high-frequency electric knife should be strictly tested and inspected item by item or even several times before leaving the factory. Users should also establish appropriate and regular testing methods to ensure that the safety indicators of the electrosurgical knife are always kept within the standards of the International Electrotechnical Society and my country's high-frequency electrosurgical knife issued in May 1995 (ie IEC601-2-2, GB9706.4 and GB9706.1) within the specified range.
The safety requirements and necessary safety guarantee systems for high-frequency electrosurgery can be summarized as follows:
(1) The output must be completely suspended, that is, the high-frequency and high-voltage output part of the high-frequency electric knife should be strictly isolated from the chassis (earth) and the power supply (mains). The insulation resistance of each output port (electrode) to ground and power supply should not only be large (>100MΩ), but also the distributed capacitance to ground should be small enough (<100pF) after connecting to the application part, and it must withstand about 6000V AC Test voltage test. Once the high-frequency electrosurgery output is poorly suspended, the high and low frequency leakage currents will increase rapidly, which is prone to burns and even life-threatening. To this end, the high-frequency electric knife should also have leak-proof and moisture-proof properties. Otherwise, once it gets damp, it will definitely affect the suspension degree of the electrosurgical output.
(2) The metal casing of the electric knife should be grounded reliably, that is, the ground wire of the power supply should be truly connected to the earth, and the connection resistance with the ground point of the machine should be less than 0.2Ω (including the ground wire of the power cable) to prevent the machine from being damaged. The shell and the protective grounding point are suspended and charged, which increases the risk of electric shock and high-frequency radiation from the inside to the outside world.
(3) The grid power supply and the chassis (grounding wire) must be able to withstand 1500V voltage. The leakage current of the chassis to the ground should be lower than 0.1mA to ensure that the mains (low frequency) is well isolated from the chassis to prevent electric shock.
(4) Low-frequency current is very harmful. Excessive low-frequency leakage current will cause serious irritation to the patient and even death.
(5) The high frequency leakage current must be lower than 150mA. High-frequency leakage current refers to the radiation current of the two output electrodes of the electrosurgical knife to the ground, which has no effect on the operation and can cause burns to patients and environmental pollution.
(6) The main carrier frequency (fundamental wave) of the high-frequency electric knife should be between 0.3 and 5MHz. It should not be too low or too high (generally between 0.4 and 0.8 MHz for a fully suspended electric knife). If it is too low, low-frequency stimulation will occur; if it is too high, high-frequency radiation will be serious.
(7) In any case, the output power of the high-frequency electric knife shall not exceed 400W. Excessive power can cause injury to the patient.
(8) The output power of the high-frequency electric knife should be as stable as possible. When the power supply voltage fluctuates and the load changes, the output power should still be within the specified range. Otherwise, during the operation, either the cutting and coagulation effect is not good, or the tissue is scorched, and the patient is even severely burned.
(9) The output waveform of the high-frequency electric knife must be stable, and its fundamental wave should be a relatively pure sine wave. Otherwise, it is easy to cause unstable output power, increase high-frequency leakage current or generate low-frequency operating current.
(10) The withstand voltage of the handle of the electric knife and the surface of the connecting cable to the electrode should be able to withstand the test of 3000V (AC RMS) and 2 times the open-circuit output voltage of the high-frequency electric knife. Otherwise, it is possible to burn the operator and/or the patient due to leakage of electricity.
(11) A control action should only activate one surgical electrode of the electrosurgical knife. Otherwise, the misoperation of the unused cutter head will cause accidental burns to the operator or patient in contact with it. In some old electrosurgical scalpels, one control action can activate the output of more than one surgical electrode (knife head) at the same time. In this case, special attention should be paid: Do not connect the unused cutter head to the machine. If connected, it should be placed in an insulated container. Don't just leave it alone.
(12) The hand switch and foot switch should preferably be sealed. In this way, water, blood or disinfectant can be prevented from entering the switch and causing the electric knife to malfunction and burn relevant personnel.
(13) The area of the electrode plate should be large enough, preferably a paste type. Ensure that the density of the current returning to the machine from the patient's body is as low as possible (<0.02A/cm2=) at the contact point between the body and the plate.
(14) When the neutral electrode (plate) is disconnected or the impedance is too large, the instrument should have the function of sound and light alarm and cut off the output. Prevents burns or fires from power dissipation at breakpoints or high impedance points.
(15) The output power should increase with the increase of the set value and decrease with the decrease of the set value. Prevents the danger of unwanted power changes when adjusting the settings.
(16) When cutting and freezing are started at the same time, power output should be prohibited or only the mode with lower power output (such as condensation). Prevent excessive power from being applied to the patient due to misoperation.
(17) When cutting and freezing are started, there should be clear sound and light prompts to remind the operator to pay attention.
(18) In the use of high-frequency electrocautery in cardiac surgery, the use of defibrillators is often encountered. The applied part of the CF electrosurgical knife should be able to withstand the shock of 2kV defibrillation voltage.
(19) The electric knife can be opened for a long time under any setting, and can be short-circuited for many times without affecting the performance and safety of the machine.
(20) When the power is reconnected or restarted, the output under any setting shall not increase by more than 20%. Prevent excessive power from being suddenly applied to the patient.
(21) The output under rated load should correspond to the set position, and the power deviation should be ≤20%. The deviation between the full power and half power curves under different loads and the specified value should also be ≤20%.
(22) The working voltage of the manual switch should be ≤12V; the working voltage of the foot switch should be ≤24V.
(23) The output loop should be connected in series with a high-voltage capacitor of not less than 5000pF. The DC impedance of the output electrode (pair) should be much greater than 2MΩ to prevent low frequency output.
(24) The interior of the machine should be treated with moisture-proof treatment, and the casing should be able to prevent liquid (when overturned) from immersing in the machine. Ensure the insulation and isolation of the instrument.