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Updated: Aug 24, 2026

Ultrasonography-Guided Nasogastric Tube Placement and Verification: A Standardized Nursing Protocol
Published on: April 7, 2026
Gastric tonometry and monitoring gastrointestinal perfusion: using research to support nursing practice
Andrea P Marshall1, Sandra H West
1Department of Clinical Nursing, The University of Sydney, Sydney, Australia. andrea.marshall@uts.edu.au
Abstract:
The principles and physiological underpinnings of gastric tonometry are reviewed. Tonometric variables, including the PtCO2, pHi and CO2 gap, are described and critiqued as measurements of gastrointestinal perfusion. Increases in gastrointestinal CO2 unrelated to gastrointestinal hypoperfusion are discussed within different clinical contexts. The technical limitations of gastric tonometry, including procedural errors and PtCO2 measurement are discussed in relation to the accuracy of tonometric measurements. Tonometric measurement using semi-continuous air tonometry is introduced as a strategy to minimize technical limitations.
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