Rapid detection of oesophageal intubation: take care when using colorimetric capnometry

Rapid detection of a misplaced endotracheal tube in the esophagus is crucial, especially in emergency situations. Hence, we have compared the ability of a colorimetric CO2 indicator (Colibri technology, CO2ntrol 1) and a capnography to differentiate oesophageal and tracheal intubation, with and without CO2 air in the esophagus.

Fourteen otherwise healthy patients were intubated with an endotracheal tube in the trachea under general anesthesia. After a positive verification of this endotracheal tube and established mechanical ventilation a second endotracheal tube was placed in the esophagus. Both were initially ventilated four times, and expired CO2 was measured with a mainstream capnograph and a colorimetric indicator. In the remaining five patients CO2 containing air was inserted into the esophagus first and then ventilated four times.

Both the colorimetric indicator and mainstream capnograph verified correct placement of the endotracheal tube from the first ventilation. When the tube was placed in the esophagus, both methods correctly showed that no CO2 was present. However, in patients (n=5) with CO2 installed in their esophagus, the colorimetric indicator, but not the capnograph, had readings showing that CO2 was present. This may cause a misinterpretation of correct tracheal placement.

We found that in emergency situations where CO2 containing air may be present in the esophagus, capnography should be the preferred method of verifying endotracheal and not oesophageal intubation. The tested colorimetric CO2 indicator (Colibri technology, CO2ntrol 1) is very sensitive to low CO2 values. It may therefore falsely indicate correct endotracheal intubation, even when the tube is in the oesophageus.