Currently methods such as nuclear scintigraphy, gastric cannulation, and indwelling pH probes, for evaluating gastric emptying (GE), gastric and intestinal pH, and luminal pressure in horses are invasive and costly. Recently, a wireless ambulatory capsule technology, the SmartPillTM GI Monitoring System (SP), was introduced to measure gastrointestinal (GI) pH, pressure and temperature, and provide GE and transit time in humans. The purpose of this study was to evaluate the SmartPillTM for measurement of intraluminal GI pH, pressure, and temperature, GE time, small and large bowel transit time (SLBTT) and total transit time (TTT). Also, SP GE study was compared to gastric emptying scintigraphy (GES).
A 12-year-old female mixed breed horse weighing 454 kg was used to evaluate the SP technology. The evening before the SP study at 8:00 PM, a muzzle was placed and feed withheld. The following morning, the SP was preloaded in the end of a nasogastric tube and SP administered into the esophagus. An enhanced wireless data receiver was attached to a girth strap and gastrointestinal pH was collected every 5 seconds for 24 hours, along with luminal pressure and temperature until the SP was passed in the feces. Once the SP was expelled from the horse, feed was withheld and the horse was again muzzled overnight. The following morning the horse was fed a radioactive meal (20mCi, 99mTcDisofenin) mixed with 1kg of a complete pelleted feed (Purina® Horse Chow). Once the meal was consumed GES was performed in a standard manner for 4 hours.
Sixty-eight percent of the data packets were received from the SP during the study period and the SP was recovered intact from the horse's feces. GE time measured by the SP and GES (T7%) were 10.3 h and 4.1 h, respectively. The TTT of the SP was 46.8 h and SLBTT was 36.5 h. Gastric pH ranged from less than 1 to 7.5. The pH increased to 8 in the small intestine and abruptly decreased to pH 7.0, 23.3 h after administration. pH remained 7.0 until the SP was excreted from the horse. GI temperature ranged from 37.5°C in the stomach to 38.5°C in the large intestine. Rectal temperature taken daily during the study averaged 37.2°C
The GE measured by the SP was substantially longer than GE measured by the GES, which was probably due to the larger size and weight of the SP compared to the pelleted feed. The TTT (46.8 h) measured by the SP was similar to previous reports in horses, where TTT was 40 h. Gastric juice pH and pressure profiles were similar to previous reports. Rectal temperature was lower than GI temperature measured by the SP, which was expected. The SmartPillTM was easy to administer and shows promise as an ambulatory method for measuring GI pH, temperature, pressure, gastric emptying time and bowel transit time in health and disease.