| Waveform Characteristic | Possible Causes |
|---|
| Rapidly diminishing or absent EtCO2 levels | Excess of sedatives, opioids, or other respiratory suppressing medications; displaced or kinked sampling line; dislodged, displaced or kinked ETT; disconnection from the ventilator; complete airway obstruction, esophageal intubation |
| Rising EtCO2 levels | Inadequate respiratory rate/volume (hypoventilation); may be Secondary to sedatives, opioids or other respiratory suppressing medications, inadequate weaning from ventilator |
| Falling EtCO2 levels | Increased respiratory rate/volume (hyperventilation); may be secondary to pain or anxiety, excessive tidal volume |
| Elevated baseline CO2 | Typical of rebreathing, inadequate oxygen flow, shallow breathing, unable to clear dead space, ventilator malfunction |
| EtCO2 waveform does not reach plateau | Small airway obstruction, bronchospasm, COPD/emphysema, airway secretions, dislodged, misplaced or partially kinked ETT; uncuffed ETT air leak |
| Cleft present in EtCO2 plateau | Indicates spontaneous respiratory effort in mechanically ventilated patient |