Using external anal sphincter activity to detect the onset of bladder contractions

Abstract

Individuals with spinal cord injury or neurological disorders may develop, involuntary bladder contraction at low volumes (bladder hyper-reflexia), which can lead to significant health problems. Current devices can eliminate nascent contractions through continuous stimulation, but do not have a means to detect the onset of bladder contraction to stimulate conditionally. The objective of this study is to determine the relationship between the activity of the external anal sphincter (EAS) and hyper-reflexive bladder contraction, and to use the relationship to develop a model to detect the onset of a bladder contraction. Bladder pressure and EAS EMG were recorded in four intact male cats. There was little EAS activity during the bladder contraction and more activity between contractions (p<0.001). A model was developed to predict the onset of a bladder contraction using the EAS EMG activity. The model calculated the onset of bladder contraction on average 4.8 seconds after the contraction started with an average increase in pressure of 8.7 cmH/sub 2/O. There existed a phasic relationship between the bladder and the EAS, which enabled the prediction model to detect the onset of a bladder contraction. The EAS EMG can be used as a trigger to deliver conditional inhibitory stimulation of the bladder.