End-tidal CO2 ("EtCO2") monitoring is a noninvasive technique that measures the partial pressure or maximal concentration of carbon dioxide (CO2) at the end of an exhaled breath, which is expressed as a percentage of CO2 or mmHg. EtCO2 monitors, or capnometers, help practitioners receive and assess instant feedback about ventilation, as opposed to pulse oximeters, which provide feedback about oxygenation.