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Equipment review: Gastric intramucosal pH measurement

BioMed Central
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  • Review


Equipment review: Gastric intramucosal pH measurement REVIEW Equipment review: Gastric intramucosal pH measurement Francisco Baigorri, Xavier Calvet, Domenec Joseph 64cc-1-2-061 Introduction Gastric tonometry has emerged as an attractive, rela- tively noninvasive technology for assessing gastrointest- inal perfusion and oxygenation by detecting acidosis in the gut wall. Several clinical studies have shown that gastric intramucosal acidosis detected by this procedure predicts increased mortality of critcally ill adults in med- ical and surgical intensive care unit (ICU) settings [1-3], and that it is a better predictor of mortality from critical illness than other mesures of global oxygen delivery and systemic hemodynamics [4]. It has also been suggested that correcting intramucosal acidosis may increase survi- val in selected critically ill patients [5]. The purpose of this review is to discuss factors influ- encing in vivo reliability and variability of gastric tono- metry, and to analyze the causes of the occasional misinterpretation of its results. The gastric tonometry technique — causes of misinterpretation of the results The measurement of gastric mucosal acidosis by gastric tonometry is based on the principle that the fluid in a hollow viscus can be used to estimate gas tensions in the surrounding tissues. The main assumption is that, after a given equilibration time, luminal and mucosal CO2 partial pressures (PCO2) will be similar. Conse- quently, the increased tissue production of CO2 during hypoxia (from the reaction between hydrogen anions and bicarbonate) can be detected by analyzing the liquid inside the gastric lumen. Conventional gastric tonometry involves the place- ment of a modified nasogastric (NG) tube, equipped with a gas-permeable, saline-filled silicone balloon at its tip, into the stomach [6,7] (Fig 1). Allowing enough time for the equilibration of CO2 between the fluid in the balloon and the gastric lumen (30–90 min), the saline is then aspirated and i

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