Electrical stimulation to induce propulsive contractions in the porcine descending colon.

Electrical stimulation of the colon can improve transit in slow-transit constipation, or enable controlled emptying in colostomy patients. Preliminary studies showed that sequential stimulation of consecutive colon segments induced serial contractions resulting in colonic propulsion. This study was performed to optimize the stimulation parameters. The electrodes were inserted under the serosa of the descending colon of pigs. Charge-balanced rectangular pulses at 10 Hz were delivered in consecutive sessions. Electrically evoked contractions (ECs) were monitored using impedance planimetry and manometry. The luminal pressure and cross-sectional area (CSA), the latency and velocity of CSA decrease, and the wall tension were compared for ECs induced using 3 ms pulses of 9, 12, 15, and 30 mA. When using 15 mA, ECs induced by 0.03, 0.3, and 3 ms long pulses were compared. A current increase from 9 to 30 mA induced a significant increase in the pressure generated by contraction. The increase in pulse duration from 0.03 to 3 ms resulted in shorter latency, faster contraction, higher pressure, and higher wall tension. It is concluded that, at a frequency of 10 Hz, the best combination of current and pulse duration to elicit propulsive contractions in the descending colon of pigs is 15 mA and 3 ms.