Electrical Characteristics of Unintended Needle Dislodgement Detection Circuit using a Noninvasive Sensor

Accidental needle dislodgement during blood purification therapy has become a critical issue, occasionally leading to fatalities. This study examines a circuit designed to detect indwelling needle dislodgement through electrostatic capacitive coupling electrically connected to both the dialysis circuit and the patient’s body, thereby functioning as a non-invasive sensor without direct contact between electrodes and blood. Needle dislodgement detection is based on impedance variations between electrodes, and circuit characteristics were analyzed under various experimental conditions. Optimal signal frequency (10 kHz) and load resistor value (200 kΩ) were identified in this study. These findings suggest that the proposed circuit could enhance the safety of blood purification therapy.