Experimental evaluation of the optimum applied pressure and number of cuffs for artificial sphincter in fluid flow control in an ex vivo model

Objective

The aim of this study was to find the optimal force that should be applied to control urine leakage using a non-hydraulic cuff design, and to investigate the relationship between the number of cuffs used in urinary control and the change in demand force.

Method

In this study, five sheep bladders were used to design and build a biomechanical evaluation system. The biomechanical system included the bladder, pressure gauge, pressure regulator system of the bladder, and force application system by the cuff. In this study, we increased the fluid pressure inside the bladder from 0 cmH₂O to 200 cmH₂O (1 cmH₂O=0.098 kPa), and at each point, the force applied by the cuff to prevent fluid leakage was measured and recorded.

Results

The study revealed that a mean tensile force of 2.81 (standard deviation 0.23) N for a single cuff and 1.63 (standard deviation 0.16) N for double cuffs with symmetrical pressure effectively prevented bladder fluid leakage in the pressure range from 75 cmH₂O to 100 cmH₂O (p<0.001). However, there were no significant differences in results when comparing the applied tensile force required by double cuffs with asymmetric tensile force to that of the single cuff use. Furthermore, using three cuffs instead of two did not yield significantly different outcomes.

Conclusion

Using double cuffs with symmetrical pressure had a greater effect compared with a single cuff with the same tensile force. Although multiple cuffs with varying tensile forces were not found to be useful in controlling urine leakage in this study, it is suggested that applying variable forces alternately and rotationally among several cuffs may reduce long-term risks such as atrophy and necrosis. Future in vivo studies are recommended to further evaluate efficiency.