Gastric mucosal tonometry: towards new methods and applications

Gastrointestinal tonometry is a minimally-invasive method of assessing splanchnic perfusion. The measurement of regional-CO2 (PrCO2) and calculation of intra-mucosal pH (pHi) using the gastro-intestinal tonometer has been shown to be predictive of outcome in critically ill patients. Furthermore, the use of tonometrically derived data as therapeutic indices have been associated with improved outcome. The original balloon-saline method of tonometry was laborious, cumbersome and prone to systematic errors. The Tonocap (Tonometrics Division Instrumentarium Corp., Datex, Finland) is an automated on-line air based system. We present here a detailed description of the Tonocap along with a summary of the results of some of the original in-vitro, animal in-vivo and human experiments. The Tonocap is a major advance in regional monitoring and its introduction into clinical practice should allow widespread assessment of the value of gastro--intestinal tonometry in the management of the critically ill.