Anorectal sphincter muscle stimulator design

摘要

One of the anorectal anomalies observed very commonly in our university hospital is the problem of closed rectum in the newborns. Before operating on the rectal area, a surgeon needs to stimulate the anorectal sphincter muscle in order to prevent any damage to the muscle itself while making a rectal opening. Stimulation of this muscle also helps to locate the rectal opening at the right place; otherwise false positioning of the opening might lead to some other undesirable problems. In this study, we have designed a stimulator that provides reasonably constant output current depending on the physiological impedance of the rectal area. The current amplitude can be set between 20 and 250 mAs. Stimulation pulses are adjusted for a duration of 230 μs and can be obtained at a repetition period between 1.75 and 20 ms. The hardware part is composed of five parts; 1) DC to AC conversion from battery power supply 2) AC Amplification through a transformer 3) AC to DC conversion 4) Current Regulation and 5) Pulse duration and period adjustment. The stimulator has been tested on 70 patients in the Pediatric Surgery Department of Erciyes University Hospital. On average, about 140 mAs was enough to stimulate the muscle when probes were applied over the skin. On the other hand, with the placement of probes beneath the skin, stimulation was obtained for pulse amplitude of 40 mAs. The main advantages of this designed system over the available commercial stimulators are its compact size, light weight and low cost. Best of all, you are not bound with searching for an electrical outlet on the walls, since it is operated on a battery supply and also due to its portability, it can be easily used at multiple sites.