A non-invasive algorithm of the continuous intra-abdominal pressure measurement using parametric curve fitting method

The rectal pressure is considered to be the 'gold standard' for the assessment of the intra-abdominal pressure (IAP). However, conventional rectal catheters can cause erroneous results, and it is not comfortable for the patients. To reduce these problems, we contrived a non-invasive measurement of the IAP using the parametric curve fitting method, such as using a linear, quadratic, cubic, quartic, exponential and sine equation modeling, between the rectal pressure and the root mean square (RMS) values of surface electromyographic (sEMG) signals, recorded simultaneously from the abdomen. The study group consisted of 12 patients (7 males and 5 females) with neurogenic bladders due to spinal cord injury. The average age and body mass index of the subjects were 53.2 (S.D. ±11.9) years and 24.4 (S.D. ±2.7), respectively. By our devised algorithm, the correlation coefficient and root mean square error (RMSE) between the measured and estimated IAP by the quartic polynomial modeling, were 0.86±0.05 and 4.70±1.56, respectively. This method suggested that the sEMG should be used reliably for the indirect measurement of the IAP in ambulatory urodynamics monitoring studies.