Assessment of the gastric emptying velocity by the 13C-octanoate breath test: deconvolution versus a Wagner-Nelson...

The dynamic change in gastric emptying on a minute-by-minute basis (gastric velocity) is evaluated by the 13C-octanoate breath test with deconvolution analysis. However, deconvolution is impractical, because it requires dual experiments to obtain 13CO2 excretion profiles following intraduodenal and oral administration of 13C-octanoate. We investigated whether the Wagner-Nelson method, used in drug absorption studies, can determine the velocity profile based on a single experiment as accurately as deconvolution, and whether the velocity assessed by the Wagner-Nelson method is sensitive enough to detect subtle changes in gastric emptying induced by butylscopolamine.

Five male volunteers underwent a 4-h breath test twice, after intraduodenal administration of 20 ml normal saline containing 100 mg 13C-octanoate and after ingestion of a 320-kcal muffin containing 100 mg 13C-octanoate. Deconvolution determined the velocity profile by subtracting duodenal from oral data, and the Wagner-Nelson method produced it from only oral data. The velocity profiles were compared between the two methods. Another six male subjects underwent the breath test by ingesting a muffin twice, once with and once without 20 mg oral butylscopolamine. The velocity profiles generated by the Wagner-Nelson analysis and the conventional 13CO2 excretion curves were compared between the two occasions.

The two techniques yielded identical velocity profiles. The velocity profile detected a significant change in the emptying pattern induced by butylscopolamine (initial acceleration with subsequent deceleration), while the conventional breath curves failed to detect this change.

Velocity assessment by a Wagner-Nelson analysis can precisely describe altered gastric emptying, based on a single experiment.