Proposed new bladder volume monitoring device based on impedance measurement

Abstract

A new implantable bladder volume-monitoring device based on the impedance measurement of the detrusor muscle is described. The system is completely autonomous and forms a mixed-signal (analogue/digital) feedback loop with a neuro-stimulator to rectify bladder dysfunctions (incontinence and retention) through neuromuscular stimulation techniques. A programmable instrumentation amplifier and a signal processing block, to eliminate the artefacts caused by the patient's movements, have been designed and tested. The layout for the signal processing block has been realised in 0.8 micron BiCMOS technology.

Feasibility of fluid volume conductance to assess bladder volume

“…21 Similar attempts to assess bladder volume relied upon invasive procedures to place electrodes within the bladder wall. 22,23 These methods produced data exhibiting a correlation between impedance (the inverse of conductance) and volume, which results from the thinning and elongation of the detrusor with increasing bladder volume.…”

Impedance Ratio Method for Urine Conductivity-Invariant Estimation of Bladder Volume

“…In consequence, urine conductivity is highly dependent on renal activity and can not be assumed constant. Early experiments identified the influence of different urine conductivities on bladder volume estimation from impedance measurements [11,12] and suggested further research in this field.…”

Electric impedance tomography for monitoring volume and size of the urinary bladder

“…Thus, a method that continuously and unobtrusively monitors fl uid volume in the bladder would be a valuable asset for these patients, especially when coupled with a threshold-based alarm function. In principle, the measurement of tissue bioimpedance seems to be a promising technique for this task, as it specifi cally relates to tissue fl uid content [10,15,21] and has been proposed for the determination of bladder volume [6,22,24] or pressure [11] . However, until now, such measurements have been catheter based and invasive.…”