From the Guidelines
End-tidal carbon dioxide (ETCO2) detectors are highly effective tools for confirming proper endotracheal tube placement and detecting esophageal intubation, with a recommendation to use continuous waveform capnography in addition to clinical assessment as the most reliable method of confirming and monitoring correct placement of an endotracheal tube (Class I, LOE C-LD) 1. When an endotracheal tube is accidentally placed in the esophagus instead of the trachea, an ETCO2 detector will typically show absent or very low CO2 readings (usually less than 5 mmHg) after multiple breaths. This occurs because the esophagus does not contain significant amounts of carbon dioxide, unlike exhaled air from the lungs. Some key points to consider when using ETCO2 detectors include:
- Colorimetric ETCO2 detectors change color based on CO2 levels - typically purple in the absence of CO2 (suggesting esophageal intubation) and yellow when CO2 is present (suggesting correct tracheal placement) 2.
- Waveform capnography provides even more detailed information, showing a flat line with esophageal intubation versus a characteristic rectangular waveform with proper tracheal placement 2.
- While ETCO2 detection is highly reliable, it's essential to note that in certain clinical scenarios such as cardiac arrest, severe hypoperfusion, or massive pulmonary embolism, CO2 readings may be diminished even with correct tube placement 3.
- Therefore, ETCO2 detection should be used alongside clinical assessment and other confirmation techniques like direct visualization, chest rise observation, and auscultation for optimal verification of tube placement 1. It's also important to consider the potential for false-positive and false-negative readings, and to use a second method to confirm endotracheal tube placement if CO2 is not detected 3.
From the Research
Role of End-Tidal Carbon Dioxide (ETCO2) Detector
The role of end-tidal carbon dioxide (ETCO2) detector in diagnosing esophageal intubation is crucial, as it helps in verifying the correct placement of the endotracheal tube. The ETCO2 detector measures the amount of carbon dioxide present in the exhaled breath, which is typically higher in tracheal intubation compared to esophageal intubation.
Key Findings
- A study published in 2002 4 found that capnography is a more reliable method for verifying endotracheal intubation, especially in emergency situations where CO2 containing air may be present in the esophagus.
- Another study published in 1990 5 found that colorimetric ETCO2 monitoring is a safe, reliable, rapid, simple, and portable method for determining endotracheal tube position in patients who are hemodynamically stable.
- A study published in 1994 6 found that a semiquantitative, colorimetric FEF end-tidal CO2 detector is 100% reliable for confirming tracheal placement and detecting esophageal intubation in emergency settings.
- A more recent study published in 2023 7 compared upper airway ultrasonography with end-tidal capnography for confirming endotracheal tube placement and found that upper airway ultrasonography can be a reliable method for confirmation of ETT location.
- A study published in 2003 8 found that the ETCO2 monitor is the most reliable method for verifying tracheal intubation in non-cardiac arrest patients, but during cardiac arrest and cardiopulmonary resuscitation, clinical methods are superior to the use of these devices.
Advantages and Limitations
- The ETCO2 detector is a rapid and non-invasive method for verifying endotracheal tube placement.
- However, it may not be reliable in certain situations, such as cardiac arrest or when CO2 containing air is present in the esophagus.
- The accuracy of the ETCO2 detector can be affected by various factors, including the type of detector used, the patient's hemodynamic status, and the presence of CO2 in the esophagus.