Is the Time for Absorption and Oxidation of ¹³C-Octanoate Really Negligible in the Gastric Emptying Breath Test?

Excerpt

To the Editor: Breath testing using ¹³C-labeled octanoate allows indirect assessment of gastric emptying by monitoring ¹³CO₂ exhaled [1, 2]. ¹³C-Octanoate is absorbed only after it is emptied from the stomach, and is oxidized to ¹³CO₂ in the liver. The methodological relevance of the breath test is based on the assumption that intestinal absorption and hepatic oxidation progress so rapidly as to be bypassed effectively [1]. No one has doubted the validity of the assumption, because pulmonary ¹³CO₂ excretion attains its peak level 10 min after direct administration of ¹³C-octanoate into the duodenum [1]. However, the rapid peak of ¹³CO₂ excretion does not necessarily exclude the possibility that the slow absorption of ¹³C-octanoate is ongoing long after the time of peak excretion.

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