Gastric pH and motility in a porcine model of acute lung injury using a wireless motility capsule

Wireless Monitoring of Gastrointestinal Transit Time, Intra-luminal pH, Pressure and Temperature in Experimental Pigs: A Pilot Study

BACKGROUND

There is no single gold standard for investigation of gastrointestinal motility function. Wireless motility monitoring involves a novel concept which provides a complex information on gastrointestinal function (gastrointestinal transit time, intra-luminal pH, pressure and temperature). Gastrointestinal motility functions of experimental pigs are very similar to those of humans. That is why porcine studies have already provided suitable experimental models for several preclinical projects.

AIMS

The aim of our study was to adopt methods of non-invasive wireless monitoring of gastrointestinal functions in experimental pigs.

METHODS

Five experimental adult female pigs were enrolled into the study. Wireless motility capsules were delivered into the porcine stomach endoscopically. Gastrointestinal transit and intra-luminal conditions were recorded for five days.

RESULTS

Records of animals provided good (3 pigs) or very good quality files (2 pigs). 31150 variables were evaluated. Mean time of the presence of capsules in the stomach was 926 ± 295 min, transfer of a capsule from the stomach into the duodenum lasted 5-34 min. Mean small intestinal transit time was 251 ± 43 min. Food intake was associated with an increase of gastric luminal temperature and a decrease of intra-gastric pressure. The highest intra-luminal pH was present in the ileum. The highest temperature and the lowest intra-luminal pressure were found in the colon. All data displayed a substantial inter-individual variability.

CONCLUSIONS

This pilot study has proven that a long-term function monitoring of the gastrointestinal tract by means of wireless motility capsules in experimental pigs is feasible. However, both ketamine-based induction of general anaesthesia as well as long-lasting general anaesthesia (> 6 hours) should be avoided to prevent retention of a capsule in the porcine stomach.

Evaluating intra-abdominal pressures in a porcine model of acute lung injury by using a wireless motility capsule

BACKGROUND

Intra-vesical pressure measurement as the reference standard for assessing intra-abdominal pressures is mainly indirect and discontinuous. We therefore evaluated a motility capsule for continuous intra-abdominal pressure measurement in an animal model with a high probability for capillary leakage and intestinal edema.

MATERIAL/METHODS

Motility capsules were inserted into the stomachs of 8 anesthetized and ventilated pigs. Stomach pH, pressure, and temperature data were wirelessly transmitted to a recorder attached to each animal's abdomen. Intra-gastric pressures measured by the capsule were compared to intra-vesical pressures measured by a pressure transducer system.

RESULTS

The intra-abdominal pressures ranged from 3 to 15 mmHg (7.8 ± 2.4 mmHg [mean ± SD]) measured via the bladder. The capsule pressure recordings ranged from 1 to 3 mmHg (1.7 ± 0.5 mmHg [mean ± SD]). Bland-Altman analysis revealed an unacceptable bias between the 2 methods. The test bias was 6.2 (± 1.4) mmHg and the limits of agreement were from 3.3 to 8.9 mmHg.

CONCLUSIONS

Pressures in the stomach as measured by motility capsule underestimated the intra-vesical pressures. Discrepancies between gastric and intra-vesical pressures could be caused by gastric dilatation or different position of the 2 devices to the zero reference point.