ETCO2 monitoring during low flow states: clinical aims and limits

End-tidal carbon dioxide concentration in the expired air (ETCO2) is measured with different technologies. ETCO2 allows the global evaluation of three main body functions: metabolism, circulation and ventilation. If two of these parameters are held constant, changes in ETCO2 reflect a variation of the third. Thus, ETCO2 is now widely used as a reliable monitoring device in various clinical settings. In the past years several studies proposed ETCO2 as a noninvasive monitor for the evaluation of therapeutic efforts during low-flow states, and especially during cardiopulmonary resuscitation. However, recent laboratory and clinical investigations demonstrated that various pharmacological and physical interventions may influence ETCO2. Especially, the use of the CO2 generating buffer NaHCO3 increase and alpha-adrenergic agents constantly decrease ETCO2. Thus, although ETCO2 remains a necessary tool during anaesthesia, it may loose the potential for prediction of survival when monitoring the resuscitative efforts during cardiopulmonary resuscitation.