A CO2 monitoring system (20) is described which is operable to monitor the CO2 content of respiratory gases during intubation, CPR, or ventilation treatment of a patient. The patient's respiratory gases are sensed for CO2 content (17) and characteristics of a CO2 waveform are detected (30), such as waveform baseline, waveform amplitude, waveform frequency, waveform slope, waveform rhythm, and waveform corners. One or more of the waveform characteristics are analyzed in consideration of the type of respiration treatment being performed to identify an abnormal respiratory condition. These abnormal conditions may include the intubation tube located in the esophagus, ineffective CPR, or an airway obstruction, for example. When an abnormal condition is identified (34) a visual or audible alarm (40) is issued to alert a caregiver to tend to the patient.