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.

Keywords: Capsules, Acute Lung Injury - physiopathology, Abdominal Cavity, Pressure, Radio Waves, Swine, Telemetry - instrumentation