A new ambulatory urodynamics monitoring system of measuring the abdominal pressure using the bio-impedance method

Abstract

The conventional urodynamic monitoring is performed by filling artificially the bladder with saline. It is difficult to evaluate the physiological functions of the storage and voiding of the bladder. In this study, we constructed an ambulatory urodynamic monitoring (AUM) system and proposed a novel method estimating abdominal pressure by bio-impedance changes and EMG activity. The system was evaluated in 10 patients. As the intensity of the abdomen contraction increased, the amplitude of bio-impedance signal and the RMS value of EMG increased as compared to those observed during resting. The correlation coefficient was 0.72 for the "weak" contraction, 0.96 for strong contraction, 0.90 for stronger contraction, 0.84 for vigorous contraction and 0.78 for maximal contraction. Also, daily events such as coughing, sneezing and conversation, were sensitively monitored by observing the amplitude change of the bio-impedance signals. However, the EMG signals could not be used to detect these events, therefore, bio-impedance method is a more useful tool to measure the changes in the abdominal pressure noninvasively for urodynamic monitoring. © Springer-Verlag 2007.