What is the most reliable indicator of successful endotracheal (ET) intubation?

End-Tidal CO2 is the Most Reliable Indicator of Successful Endotracheal Intubation

End-tidal CO2 detection is the most reliable indicator of successful endotracheal intubation. According to the American Heart Association guidelines, exhaled CO2 detection remains the most reliable method of confirmation of endotracheal tube placement 1.

Evidence Supporting End-Tidal CO2 Detection

The American Heart Association guidelines provide strong evidence for end-tidal CO2 detection as the gold standard:

• Continuous waveform capnography is recommended with a Class I, Level of Evidence A recommendation as the most reliable method of confirming and monitoring correct placement of an endotracheal tube 1
• Studies of waveform capnography to verify endotracheal tube position in cardiac arrest victims have shown 100% sensitivity and 100% specificity in identifying correct tube placement 1
• Even when waveform capnography is not available, colorimetric and nonwaveform exhaled CO2 detectors can be used in addition to clinical assessment as the initial method for confirming correct tube placement (Class IIa, LOE B) 1

Comparing the Options

Let's analyze each option from the question:

1. Chest X-ray: While definitive, it has significant limitations:

   • Requires time to obtain and interpret
   • Not practical for immediate confirmation during emergency situations
   • Cannot provide continuous monitoring of tube position

2. End-tidal CO2: Superior for several reasons:

   • Provides immediate confirmation
   • Studies show 100% sensitivity and specificity in identifying correct tube placement 1, 2
   • Offers continuous monitoring capability
   • Faster than chest auscultation in confirming tracheal intubation 3

3. Cord visualization:

   • While direct visualization confirms initial placement
   • It doesn't confirm ongoing proper positioning
   • Cannot detect tube displacement after initial placement

4. Chest auscultation:

   • Less reliable with sensitivity of 94% and specificity of 83% in non-arrest patients 2
   • Can be misleading in certain clinical scenarios
   • Inferior to capnography in emergency conditions 2

5. Pulse oximetry:

   • Delayed indicator of tube misplacement
   • Can be affected by many factors unrelated to tube position
   • Not specific for tube position

Important Caveats and Limitations

While end-tidal CO2 is the most reliable indicator, clinicians should be aware of potential false readings:

• False-negative readings may occur during:

  • Low cardiac output states or cardiac arrest (due to reduced CO2 delivery to lungs)
  • Pulmonary embolism
  • Severe airway obstruction or pulmonary edema 1

• False-positive readings are rare but can occur:

  • After ingestion of large amounts of carbonated liquids before arrest 1
  • However, the waveform doesn't continue during subsequent breaths in these cases

Best Practice Approach

For optimal confirmation of endotracheal tube placement:

1. Use end-tidal CO2 detection as the primary confirmation method
2. Combine with clinical assessment (chest rise, auscultation)
3. If CO2 is not detected, use a second method such as direct visualization or esophageal detector device 1
4. Consider continuous waveform capnography for ongoing monitoring when available

In neonatal resuscitation specifically, when positive pressure ventilation is provided through an endotracheal tube, the best indicator of successful endotracheal intubation with successful inflation and aeration of the lungs is a prompt increase in heart rate, with exhaled CO2 detection remaining the most reliable method of confirmation 1.