Technical and clinical aspects of capnography in neonates

This article reviews the current literature on the uses of capnometry and capnography as applied to neonates. The first part addresses the technical aspects and principles of the measurements, including definitions. The features of available carbon dioxide analysers are discussed and factors known to influence their accuracy are highlighted. In the second part of this paper, in vivo studies in neonates are reviewed, with particular emphasis on understanding why the accuracy of end-tidal CO2 measurements differs among studies. This is attributable to various factors: aspiration flow rate, the sampling site (whether distal or proximal) and the type of capnometer. The critical limitation of their overall accuracy in the presence of lung disease is discussed. Potential applications are considered, as are the current limitations of transcutaneous monitoring. We conclude that capnometry with capnography is a potentially useful tool to arterial CO2 tension (PaCO2) monitor infants with normal lungs.