Long-Term Telemetric Recording and Computer
Analysis of Colonic Motility in Unrestrained Pigs

J. McRorie1, W. Mills2, E. Konigsberg2, and M. Hastings3,
The Procter & Gamble Company, Mason, OH1, Konigsberg Instruments, Pasadena, CA2, and Data Integrated Scientific Systems, Pinckney, MI3

Introduction The mammalian large intestine is responsible for the mixing, dehydration, storage, transport and evacuation of luminal contents. The motor events that facilitate these activities are poorly understood. This is due, in part, to the low frequency and high variability of colonic motor events. Colonic motions are so slow, and recur at such long intervals, that they may not be fully appreciated by the short term observations usually used to study them. Recent advances in self-contained 'data loggers' have facilitated longer (24 hour) recording periods in ambulatory subjects, but their limited memory capacities require slow sampling rates (1 Hz), and data are inaccessible while recording. Extended monitoring of colonic motility in unrestrained, ambulatory subjects requires an extremely durable solid state probe and telemetric recording device, and a computer system providing continuous acquisition, a sampling rate enabling digital reconstruction of analog events, artifact filtering, analytical interpretation, and adaptability to signal changes.

Methods The aim of this study was to develop a method for extended term monitoring and high resolution analysis of colonic motility in unrestrained, ambulatory Yucatan mini pigs. We have developed a versatile telemetric recording system (Konisberg Instruments: custom-built motility probe, amplifier/telemetry transmitter, and base station receiver/decoder), coupled with a computer analysis program (Data Integrated Scientific Systems), capable of high sampling rates, virtually unlimited memory (optical disc), and on-line (monitor and laser printer) observation and analysis of motility. Three female Yucatan mini pigs had a cecal fistula created by surgically attaching the cecum to the abdominal wall. The pigs have been maintained for >3 years without serious health problems.

Results Colonic motility was recorded continuously in the proximal colon for up to 6 consecutive days using a motility probe with 5 solid state pressure transducer ports. A baseline of motility values and patterns has been established from sixty three 24-hour recordings for the proximal colon of the pig. Non-propagating motility was the predominant motor activity, and was observed as either random events (87% of recorded non-propagating events) or in a '3 contractions per minute' (3 cpm) pattern (13% of recorded non-propagating events). Propagating contractions were also observed, and represent approximately 6% of all recorded pressure events.

Discussion The data acquisition rate of this system allowed for the identification of propagating contractions with rates up to 16cm/s, not previously described in the literature. The relatively high frequency (27.9 + 2.6/24 hours), high velocity (4.9 + 1.7cm/s), low amplitude (31.2 + 0.9mmHg), and short duration (7.8 + 0.9s) of these rapidly propagating contractions suggest they may act on a lower viscosity substrate, such as gas.