Waveform end-tidal CO2 (EtCO2) monitoring is an essential tool we must be using in our departments. This additional data can help you make ventilator changes while checking fewer blood gases. It can give you information regarding dead space. When flow monitoring is added you can even measure cardiac output with EtCO2 and a blood gas. All of these things require you to have an accurate reading. The EtCO2 number reading is not sufficient. You must be able to read the waveform to assure you can trust the number.
For normal exhalations, you should see a good plateau on your waveform. Each plateau should appear similar with small EtCO2 changes between breaths. If you have multiple, short, peaks with wildly varying EtCO2 numbers, your patient is like taking shallow breaths and you are not actually measuring gas from the alveoli which contains the most CO2.