Electrical impedance spectroscopy on a needle for safer Veress needle insertion during laparoscopic surgery

Micro-electrical impedance spectroscopy-on-a-needle for depth profiling (μEoN-DP) of biotissue is proposed as a potentially safer technique for insertion of the Veress needle (VN) to prevent and immediately recognize iatrogenic injury during laparoscopic surgery. By comparing the electrical impedance of intra-abdominal cavity with that of organs prone to iatrogenic injury, the μEoN-DP can localize a safe place for infusion of CO2 gas to secure the necessary space required for laparoscopic surgery. The proposed device was evaluated though in-vivo experiments on three rats by analyzing the electrical impedance of the intra-abdominal cavity with that of organs prone to iatrogenic injury. The discrimination capability of the device was verified through impedance differences, discrimination index, and statistical analysis of the measured impedance over the frequency range from 100 Hz to 1 MHz. The impedances of the abdominal cavity and organs were clearly discriminated at the optimal frequencies obtained on the basis of the discrimination index. The real part of impedance was recommended as the best impedance parameter to discriminate between abdominal cavity and organs in real-time. To analyze the electrical characteristics of the abdominal cavity and organs, the resistance and capacitance were extracted through curve fitting to a proposed electrical equivalent circuit. The extracted resistance of the abdominal cavity is 4.8 times larger than that of the organs, whereas the extracted capacitance of the abdominal cavity is a factor of 2.8 smaller than that of the organs. The experimental results in the present research potentially imply that the VN with an electrical impedance spectroscopy (EIS) sensor can improve the safety of laparoscopic surgery by localizing a safe place in the abdominal cavity, and by performing prompt management when an iatrogenic organ injury occurs.