EtCO2 monitoring is a valuable tool for clinical management of patients in cardiac arrest, near-arrest and post-arrest. During cardiac arrest, EtCO2 levels fall abruptly at the onset of cardiac arrest, increase after the onset of effective CPR and return to normal at return of spontaneous circulation (ROSC). During effective CPR, end-tidal CO2 has been shown to correlate with cardiac output, coronary perfusion pressure, efficacy of cardiac compression, ROSC and even survival. Colorimetric detectors (shown to correlate with infrared capnometry) have been shown to have prognostic value in both adult and pediatric CPR. The higher the initial value of EtCO2, the greater was short-term survival. EtCO2 is a useful tool during patient resuscitation for evaluating the current and potential effects of treatment, and could be potentially useful in determining when to terminate resuscitation efforts.