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Global Health Technologies

Undergraduate Lightning Talks

Toward the Prevention of Patient Burns During Electrosurgery Procedures: Development of a Test System to Characterize Grounding Pad Adhesive Contact

Saturday, October 26, 2024
12:30 PM – 12:35 PM EST
Location: Room 342

Introduction:  Electrosurgery is a useful surgical technique that uses electricity to generate heat to alter tissues (e.g., cutting, coagulation). The main components are an electrosurgical generator, a hand-held electrosurgical instrument, and a neutral electrode adhered to the patient, also known as a dispersive electrode or grounding pad. Grounding pads ensure patient safety by helping safely manage electrical currents generated by electrosurgical instruments. Their disfunction or loss of adequate adhesion to the patients’ skin leads to risk of patient burns when electrical current is released as heat [4,5]. Although grounding pads are designated as single-use devices (disposable), the World Health Organization documents frequent reuse beyond their lifespan [7]. Because safe reuse requires reprocessing, cleaning, and disinfection of grounding pads after each use, there is a need to detect any damage and to verify safe function. In a previous study from our team, over 500 grounding pad malfunctions were documented using a structured search of the FDA’s MAUDE database. In a survey of 59 physicians in Africa, 49% recorded complications associated with electrosurgery, included burns [2]. Based on these risks to patient safety, there is need for an affordable test system to assess the function of electrosurgical grounding pads [3]. The broad objective of this work was to develop and validate a procedure for testing electrosurgical grounding pads under a simulated clinical environment for patient safety. The first phase involved experimental approaches for detecting changes in grounding pad resistance due to grounding pad malfunction or loss of adhesion.

Materials and

Methods:  Initial experiments for measuring impedance across electrosurgical grounding pads used a new grounding pad (Model 800, Uni-Patch Specialty Electrodes, Cardinal Health) adhered to a thin (0.635 mm) conductive copper plate, similar to IEC 60601-2-2017 guidelines [1]. A multi-meter was used to measure the resistance of the grounding pad as a function of contact area between the grounding pad and plate. Additionally, the grounding pad was adhered to the conductive plate, supplied with a 12-volt DC power supply, and connected in a series circuit that was tested separately with three different resistors (10 kilo-ohm, 1 kilo-ohm, 470 ohm). The voltage drop was measured across the grounding pad by connecting the multi-meter leads to the grounding pad output wire and the conductive plate. Area of contact was varied from 100% contact to 0% contact in increments of 25% (Figure 1), which simulated varied quality of adhesion that can occur when attached to a patient.
Subsequently, a test system was designed to measure impedance across a four-quadrant grid pattern over the grounding pad surface. A circuit was designed around an Arduino Uno interface to monitor the voltage drop in different quadrants. Similar to the initial experiments, the grounding pad acted as a large resistor in the circuit. The circuit leads were attached to the edge of the grounding pad using pairs of alligator clamps at the four-quadrant points (Figure 1). A back projection calculation was used to convert the measured voltage drops into the actual resistance values on the bulk of the pad.

Results, Conclusions, and Discussions: The grounding pad had a varied resistance dictated by the area of contact between the pad and the conductive plate, ranging from 2.5 kilo-ohms with full contact and 7 kilo-ohms with no contact. That is, the lower the contact area between the grounding pad and copper plate the higher the resistance. In the series circuit, the magnitude of resistance was linearly related to the adhesive contact area between the grounding pad and copper plate. The voltage drop across the grounding pad increased with decreased contact area between the grounding pad and copper plate (Figure 2). This behavior of increased voltage drop with small contact area was confirmed for a degraded grounding pad, which lacked adhesive on approximately 25% of the pad surface.
The test system for evaluating grounding pad performance in different quadrants did not provide reliable measures of the voltage drop in different quadrants. Attaching the circuit leads directly to the pad led to degradation at that interface and did not provide an overall current flow through the entire pad surface. It did not provide clear indications of pad degradation or changes in adhesive contact area. Therefore, it is critical to adhere the pad to a conductive surface to mimic the role of human skin contact. This test system will be integrated with a copper plate and measures of overall pad resistance, as successfully executed in the initial experiments.
Evaluating adhesive contact area is a key factor to ensuring patient safety with electrosurgery in clinical applications. In our study, resistance varied with contact area and was detected by measuring voltage drop across the grounding pad, which is indicative of high current according to Ohm’s law. According to the ANSI/AAMI HF18:2001 standard [6], 75 ohms is an acceptable maximum measurement of contact impedance for conductive neutral electrodes when energized using a high frequency input voltage. Future work will include further development and testing of the electrosurgical grounding pad device in laboratory and clinical settings. Additionally, evaluating the effects of reprocessing on electrosurgical grounding pads under a simulated clinical environment is planned.

Acknowledgements (Optional):  We acknowledge the Clemson University Creative Inquiry Program and the Clemson University Honors College for funding and administrative support.

References:
1. International Standard for Medical Electrical Equipment. IEC 60601-2-2:2017-03. Geneva, Switzerland.
2. Oosting, R M, et al. “Availability, Procurement, Training, Usage, Maintenance and Complications of Electrosurgical Units and Laparoscopic Equipment in 12 African Countries.” BJS Open, U.S. National Library of Medicine, Apr. 2020, Available at: www.ncbi.nlm.nih.gov/pmc/articles/PMC7092388/.
3. Petrova G, Yanev G, Spasov G, Arduino based module for return electrode contact quality monitoring in the electrosurgical instruments, 2017 XXVI International Scientific Conference Electronics (ET), Sozopol, Bulgaria, 2017, pp. 1-4. doi: 10.1109/ET.2017.8124379.
4. Rhim, Hyunchul, et al. “Radiofrequency Thermal Ablation of Abdominal Tumors: Lessons Learned from Complications.” RadioGraphics, vol. 24, no. 1, Jan. 2004, pp. 41–52, https://doi.org/10.1148/rg.241025144.
5. Sanders, Samuel, et al. “Third-degree Burn from a Grounding Pad during Arthroscopy.” Arthroscopy: The Journal of Arthroscopic & Related Surgery, vol. 25, no. 10, Oct. 2009, pp. 1193–1197, https://doi.org/10.1016/j.arthro.2008.11.003.
6. Standard for Electrosurgical Devices. ANSI/AAMI HF18:2001. Association for the Advancement of Medical Instrumentation.
7. World Health Organization, Medical devices: Managing the mismatch – an outcome of the priority medical devices project. WHO Press, Geneva, 129 pp, 2010.