Poor in vivo reproducibility of gastric intramucosal pH determined by saline-filled balloon tonometry

Abstract

Purpose: The reproducibility of gastric intramucosal pH (pHi) determinations by saline-filled balloon tonometry has not been assessed adequately. We examined the agreement of pHi obtained using pairs of tonometry catheters under various conditions in a canine model of global hypoxia.

Methods: Two gastric balloon tonometry catheters were inserted into each of 16 anesthetized dogs. Cimetidine was administered to six of the animals (group 1). Hypoxia was induced for 30 minutes by reducing the F1O2 to 0.08. pHi was determined under basal conditions, at completion of hypoxia, and during the posthypoxic period.

Results: The mean bias of the paired pHi determinations was 0.03 for group 1 and 0.00 for group 2 (P = NS). The corresponding 95% limits of agreement spanned 0.24 and 0.28 pH units, respectively. Agreement of pHi determinations between tonometry catheters was not significantly affected by varying of the equilibration period, by administration of cimetidine, or by the presence of posthypoxic conditions.

Conclusions: Clinically important disagreement was observed in simultaneous pHi determinations obtained using separate gastric balloon tonometry catheters exposed to identical in vivo conditions. Poor reproducibility of individual pHi determinations may limit the accuracy of pHi obtained by gastric balloon tonometry in the clinical setting.