Implementation of a multi-functional ambulatory urodynamics monitoring system based on newly devised abdominal pressure measurement

The measurement of the rectal pressure is considered to be the 'gold standard' for the assessment of the abdominal pressure. However, conventional rectal catheters can cause erroneous results and are not comfortable for the patients. To reduce these problems, we devised a non-invasive technique for the measurement of the abdominal pressure using the parametric curve fitting method, based on linear, polynomial, exponential or sine equation modeling, between the rectal pressure and electromyographic (sEMG) signals recorded simultaneously from the abdomen. The sEMG signals and rectal pressure were obtained simultaneously from 12 patients with neurogenic bladders due to spinal cord injury (age = 53.2 ± 11.9 years, BMI = 24.4 ± 2.7, ASIA classification: D). Using our algorithm, the correlation coefficient and root mean square error (RMSE) between the measured and estimated abdominal pressure obtained by the quartic polynomial modeling were 0.86 ± 0.05 and 4.70 ± 1.56, respectively. The results obtained herein suggest that the sEMG signals can be used reliably for the indirect measurement of the abdominal pressure in ambulatory urodynamics monitoring systems.