Gastrointestinal tonometry is a diagnostic technique that uses the diffusion of carbon dioxide (CO2) from the surrounding tissue into the gastric lumen to estimate the perfusion and oxygenation of the gut. The technique involves the insertion of a thin, flexible tube with a balloon at the tip into the stomach or intestine. The balloon is then inflated with a small amount of air or saline, and the pressure of the gas within the balloon is measured over time. As the balloon inflates, it comes into contact with the surrounding tissue, and CO2 diffuses across the tissue and into the balloon. The rate of CO2 diffusion is proportional to the blood flow and oxygenation of the surrounding tissue, and can be used to estimate the perfusion and oxygenation of the gut. Gastrointestinal tonometry is used primarily in critical care settings to monitor the perfusion and oxygenation of the gut in patients with shock or other conditions that can lead to decreased blood flow to the gut.
References: [1, 2]
1. Ackland G, Grocott MP, Mythen MG: Critical Care 2000, 4(5):269.
2. Van Haren FMP, Sleigh JW, Pickkers R, Van Der Hoeven JG: Gastrointestinal Perfusion in Septic Shock. Anaesthesia and Intensive Care 2007, 35(5):679-694.