Comparison of acid secretion rates measured by gastric aspiration and by in vivo intragastric titration in healthy human subjects.

In nine healthy subjects acid secretion rates, measured first by gastric aspiration and then by in vivo intragastric titration to pH 5, were compared. In vivo intragastric titration was initiated by instilling 50, 100, or 700 ml saline (pH 5) into the stomach, followed by a continuous intragastric saline infusion at 3.3 ml/min. Irrespective of the volume of saline used to initiate in vivo intragastric titration, acid secretion rates during titration were two to three times greater than secretion rates during gastric aspiration (P less than 0.005). This difference was not due to transpyloric acid losses during aspiration, since such losses were corrected for by nonabsorbable marker recovery; nor was the difference due to a higher intragastric pH during in vivo titration, since significant differences in acid secretion rates between aspiration and titration persisted when in vivo titration was performed at an acid pH. These findings suggest that in vivo intragastric titration leads to higher measured acid secretory rates than gastric aspiration because the titration method is associated with gastric distention and even small degrees of gastric distention stimulate gastric acid secretion.