A NONINVASIVE METHOD FOR BLADDER ELECTROMYOGRAPHY IN HUMANS

No convincing correlation of bladder EMG in humans to simultaneously m easured intravesical pressure has been reported in the literature. In most studies on bladder EMG the electrodes contact the bladder wall it self. This causes problems in the discrimination between very small ex tracellular signals, reflecting actual membrane potential changes of b ladder muscle cells, and large electro-mechanical artefact caused by e lectrode movement as the tissue contracts. Aim of this study is to inv estigate whether bladder EMG can be performed non-invasively with Ag-A gCl surface electrodes that are placed on the abdominal skin of health y volunteers. Bipolar electrode signals are obtained in a diagonal, ve rtical and horizontal direction of the abdominal electrodes. A convent ional urodynamic investigation is performed according to International Continence Society standards simultaneously with bladder EMG. This ne w method shows that voiding is accompanied by a slow voltage change in bipolar electrode signals. The contribution of abdominal and other st riated muscle activity to the bipolar electrode signals can clearly be distinguished from the slow voltage changes related to voiding. Free flowmetry shows that the electrical activity picked up by the abdomina l electrodes is related to bladder emptying. In pressure/flow studies a relation between the electrical activity and the detrusor pressure i s found. The present results suggest that the slow voltage changes fou nd during bladder contraction are caused by summed membrane potential changes of bladder muscle cells, but this concept needs further testin g. Also, validation for clinical use remains to be established.