Urine Volume Estimation by Electrical Impedance Tomography with Fewer Electrodes: A Simulation Study

Urinary incontinence is prevalent among elderly people. Recent studies have demonstrated the effectiveness of continence care based on bladder volume measurement in elderly people, who maintain the urinary storage function but have difficulty in feeling bladder fullness due to dementia or some neurological disorders. To help caregivers provide the bladder volume measurement-based care, our group is developing a wearable bladder volume sensor with an error of <; 20mL (10% error around 200 mL). This study evaluated the performance of a bladder volume estimation by impedance measurement with fewer electrodes than ordinary electrical impedance tomography in finite element simulation. The result in simulation data by 8-electrode measurement showed a root mean square error of 27.7 (0.2) mL (mean (SD)) with the normal measurement noise, and this decreased to 15.2 (0.1) mL with a smaller noise. This study confirmed that the impedance measurement with eight electrodes accurately estimates the bladder volume. As the urine conductivity is subject to diurnal variation, we tested the model in the mixed urine conductivity condition. The root mean square error increased to 57.2 (0.3) mL and was not improved even with smaller noise. Further research will include the development of an estimation model that is robust to urine conductivity variations.