Which monitor modality is most reliable for confirming correct endotracheal tube placement?

• A. Chest X-ray
• B. Waveform capnography (end-tidal CO2)
• C. Auscultation alone
• D. SpO2 waveform

Answer: (B)

Real-time verification of airway placement comes from waveform capnography because it directly shows whether carbon dioxide is being exhaled from the lungs. When the endotracheal tube is in the trachea, each breath produces a CO2 waveform with a measurable end-tidal CO2 value. If the tube is in the esophagus, there’s little or no CO2 detected and the waveform is flat, providing an immediate and reliable cue that the tube needs to be repositioned. This immediate feedback is crucial during resuscitation, and the end-tidal CO2 level also changes with perfusion, helping signal return of circulation.

Chest X-ray can confirm placement, but it isn’t instant and depends on getting radiographs and interpretation, which isn’t practical for real-time confirmation during intubation or CPR. Auscultation alone is unreliable because breath sounds can be misleading, especially in a noisy resuscitation setting or with pediatric anatomy variations. SpO2 waveform shows oxygenation status, which can be preserved briefly even if the tube isn’t in the trachea, so it doesn’t reliably confirm placement.