Capnography is the monitoring of end-tidal carbon dioxide in waveform and numeric display. For this technology to be useful, the critical care nurse must have a clear understanding of the normal capnography waveform and what the alterations in this waveform represent. The critical care nurse can use this information to plan patient care interventions with other critical care team members and to adjust care based on the patient's response. End-tidal carbon dioxide physiology, normal waveforms, abnormal waveforms, and clinical aspects of capnography monitoring are included.