Optimum electrode configuration to estimate abdominal pressure using regression analysis of bio-impedance signal

Bio-impedance technique has become a suitable method for monitoring of tissue state and functioning of organs in vivo. In this study, we determined the optimum electrode pair for measuring the abdominal pressure using bio-impedance method and compared with conventional methods. Because impedance changes differ from a weight, a height, contractile force, volume of muscle and blood other or whatever of individuals, it was quantified using impedance changes, correlation coefficient and SNR (signal-to-noise ratio). Our results showed the optimum electrode pair (1, 9) which could detect impedance changes due to daily events, which are cough, sneeze and conversation as well as diverse postures. It is the cause that this optimum electrode pair (1, 9) is synthetically reflected in physiological changes of various muscles (rectus abdominis, trasversus abdominis, external and internal oblique muscle) related to an abdomen contraction. The correlation coefficient between the abdominal pressure, measured using a rectal catheter, and the values, estimated using impedance method, was 0.77. However, correlation coefficient with values estimated using EMG method was 0.58, and it is remarkably lower than values using impedance method. Therefore, this result demonstrated that the abdominal pressure could be measured more correctly using impedance method than using EMG method. We propose that this optimum electrode configuration would be useful for future studies involving the convenient measurement of abdominal pressure by ambulatory urodynamic monitoring.