Magnetic Induction-Based Sensor for Vital Sign Detection

Nowadays, various medical applications demand for less-obtrusive and continuous respiratory and cardiac activity monitoring methods. Sleep monitoring and home health care are some examples of these applications. Magnetic induction could provide such a contactless unobtrusive method for continuous monitoring of vital signs. In this paper, we present the preliminary results of a developed magnetic induction sensor. The system consists of one coil for excitation and a specific shaped coil for detection. For data acquisition we have used a low noise amplifier plus a phase sensitive detection circuit. The measured phase angle and magnitude are acquired simultaneously with cardiac and respiratory signals from standard sensors of a BIOPAC system. Considering the objective of having a system to be integrated in the bed, the coils were designed in a printed circuit board (PCB). Supine and prone positions, apnea and breathing periods were parts of the experiments to investigate different parameters which affect the signal. Comparing the breathing and apnea periods, respiration and heart activity is clearly reflected in the detected signal and the results show that the system could detect these vital signs.