Factors affecting 13C-natural abundance measurement of breath carbon dioxide during surgery:: absorption of carbon dioxide during endoscopic procedures

The aim of this paper is to review the factors which may affect breath (CO2)-C-13/(CO2)-C-12 natural abundance in patients undergoing surgery or intensive care. Intravenous glucose administration is a major determinant of the (CO2)-C-13/(CO2)-C-12 of breath as intravenous glucose preparations are almost all derived from cornstarch. In addition, the oxidation of endogenous substrates can affect the (CO2)-C-13/(CO2)-C-12 ratio. During many endoscopic procedures, such as laparoscopic surgery, carbon dioxide insufflation is used to provide a working space. As medical CO2 is relatively depleted in (CO2)-C-13 compared with endogenous and exogenous metabolic CO2 sources, breath (CO2)-C-13/(CO2)-C-12 measurements can be used to estimate CO2 absorption during these procedures. However, all these factors may also be affected by the bicarbonate pool, making a definitive attribution of changes in breath (CO2)-C-13/(CO2)-C-12 to a single factor problematic. Copyright (C) 2008 John Wiley & Sons, Ltd.