Capnography Requirements

Figure 1

The capnography waveform can be compared to an ECG because the “normal” waveform has certain rules. Each waveform represents the various phases of inhalation and exhalation and is divided into four phases.

Figure 2

The hypoventilation waveform, related to a decreased respiratory rate, will have fewer waveforms, with each presenting increased height due to the presence of more CO2 per breath.

EtCO2 Sampling Line

Always ensure your EtCO2 sampling line is properly inserted and secured in the monitor. Check this connection if your reading doesn't seem to correspond with your patient's condition.

Figure 3

Because it reflects circulatory status, and indirectly reflects cardiac output, EtCO2 may decrease before changes in systolic blood pressure occur. For this reason, capnography should be carefully monitored in patients with acute myocardial infarction.

Figure 4

Capnography Waveform Patterns