ElectroSurgical Unit Preventive Maintenance

After we have extensively introduced the function, modes, and uses of an Electro Surgical Unit we are going to mention in this article how to apply preventive maintenance to this machine and when to do so.

Different ESU Types

We are going to break this into a list and it going to be as follows:

1. According to the sample risk assessment sheet, an electrosurgical unit needs inspection for a thorough preventive maintenance procedure 2 times per year. During which you will test the performance of the electrosurgical unit. Extreme caution should be taken while inspecting an ESU as there are a high risk of getting an electric shock from direct or indirect (e.x: leakage) ways.
2. You will need to test many things in an ESU, among which you will need to test the power output and properties of the output signal. You will also need to make sure that output current A, the power (W), and the peak-to-peak voltage (V) to be accurate.
3. The power distribution test will evaluate the ESU output across various loads to make sure that the output is adjusted with varying impedance. Thus making sure that impedance sensing circuits in the ESU are working properly and delivering outputs that are accurate regardless of load variation. 
4. ESU testing must be applied we are going through more details on how to test the ESU later in this article.
5. High-Frequency leakage (RF leakage current should also be tested, as it is a critical parameter to measure as it may cause accidental burns in patients. 
6. Return Electrode Current Monitor (RECM) is an alarm circuit that alarms operator with a visual and audible alarm in case the ESU generator reaches a high threshold of the amount of current passing through the return electrode plates/pad.
7. In case an ESU has an inert gas flow* the flow and pressure of such inert gas need to be tested. 
8. Cleaning and dust removal of the inside of an ESU is important as cleaning and dust removal helps reduce heat accumulation in the machine.
9. Some ESU manufacturers recommend replacing fuses of an ESU every preventive maintenance check. Make sure that fuses that are going to be placed are having the same specifications of the ones removed. 
10. Cables inspection is important as they are moving and could be subject to rupture. It is highly recommended that you keep spare cables as these cables can be damaged at any time and once damaged you cannot use them anymore.
11. A resistivity test must be applied to electrodes, even if they should last for a very long time. But due to continuous use, their resistance increases with time. Also, it is recommended that you have spare electrodes, or at least when you find that the resistance increased substantially consider replacing them soon. (Note: Resistivity can reach a certain limit where the electrode will no longer function properly even if the maximum load is applied).
12. The electrical safety test procedure is highly recommended, this can be easily applied if you have an electrical safety analyzer.  

Fluke 87-V Digital Multi-meter

*Some ESUs have this option by which an inert gas is flowing and envelops the surgery sites that oxygen is eliminated at the surgery site, this allows for a faster healing incision that is neat and clean as lack of oxygen prevents tissue charring.

ESU testing

For a Bio-Medical technician/engineer it is very important to be able to test an ESU machine during a preventive maintenance procedure, but caution must be taken as there is a very high frequency of electric current passing through the terminals. 

We’d test the frequency by using the oscilloscope, remember that the voltage is as indicated below: 

-300 – 2000 V (coagulation mode) with a frequency range of 250 – 2000 kHz.

-9 kV and above (cutting mode) with a frequency range of 0.5 – 2.5 MHz.

ESU Connection to Test

- A coil is needed to be wrapped around a wire taken from the output of the ESU that amplifies the current because it has a small number of turns.

- A high resistance resistor is placed so as to protect the oscilloscope and reduce the amplitude of the voltage while maintaining the same amplified current.

- The closed-circuit is now consisting of the ESU, coil, resistance, and return plate.

- Each mode of functioning produces a waveform as seen in the explanation of the modes previously.

Besides all the information mentioned above, you might consider having an electrosurgical unit analyzer. We highly recommend the fluke biomedical QA-ES III Electrosurgical analyzer. This testing device will be able to test the ESU and alarm you of any failures in the ESU. It is highly recommended that you follow the service and maintenance handbook that is designed especially for each machine.

ESU inside view

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