Monopolar Electrosurgical Return Electrode With PTC Thermistor
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Solution Overview
Problem
Monopolar electrosurgical systems face issues with unregulated current density at the return electrode, leading to potential thermal burns due to improper connection or separation from the patient, as the current density can exceed safe limits, causing unwanted heating of body tissue.
Innovation Solution
A monopolar electrosurgical return electrode featuring a flexible pad doped with a positive temperature coefficient thermistor material and a metallic foil, which increases resistance to over 100 Ohms at 45 degrees Celsius, limiting current density and preventing excessive heating by switching to a non-conductive state when temperature thresholds are met, and a feedback mechanism in the electrosurgical unit to monitor and control the resistance and current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the return electrode is not connected properly or sections separate from the patient's body, then the current density becomes unregulated, but this causes unwanted thermal effects and tissue heating
Solution Approach 1:
The patent implements a feedback mechanism where the electrosurgical unit continuously monitors the resistance of the return electrode and compares it against predetermined safe thresholds. When the resistance exceeds the threshold (indicating improper connection or separation), the system automatically terminates power delivery, preventing unregulated current density and thermal effects.
Solution Approach 2:
The system performs preliminary resistance monitoring before power is applied and maintains continuous monitoring during operation. This preliminary and ongoing detection allows the system to identify connection issues before they cause harmful thermal effects, enabling preventive action.
2Productivity
If the current density at the return electrode is high, then the cutting and coagulation action is effective, but this exceeds safe limits and heats body tissue beyond necrosis threshold
Solution Approach 1:
The patent applies different current density requirements to different locations: high current density at the active electrode for effective cutting and coagulation, while maintaining low current density at the return electrode to prevent tissue heating. The system monitors return electrode resistance to ensure the local quality at the return site remains safe.
Solution Approach 2:
The system dynamically monitors and responds to changes in electrical parameters (resistance, current density) at the return electrode. When parameters indicate unsafe conditions, the system changes the operational state by terminating power, thereby controlling the harmful thermal effects while maintaining effective surgery under normal conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively limits current density to prevent tissue necrosis by dynamically adjusting resistance based on temperature, ensuring safe surgical conditions and automatically terminating power if excessive heating is detected, thus preventing electrical burns.
Implementation Method 1
a flexible pad doped with a positive temperature coefficient thermistor material which increases resistance to over 100 Ohms at 45 degrees Celsius
Implementation Method 2
increases resistance to at least more than 100 Ohms at least 45 degrees Celsius
Data Source
AI summary
A monopolar electrosurgical return electrode to prevent unwanted thermal effects in monopolar electrosurgery, accomplished in one aspect by volumetric incorporation of temperature-resistive material of positive nature into a flexible and adhesive return electrode pad is provided. The incorporation of positive temperature coefficient resistance with low resistance at room temperature will increase the local electrical resistance of the pad with an increase of the local return electrode temperature corresponding to a switching of the resistance from low to high value which in turn will lead to a reduction of the local current density. The switching temperature of the positive temperature coefficient return electrode is low enough to prevent significant thermal heating of the patient's tissue.