No Trace = Wrong Place
Objective: Treat absent sustained exhaled CO₂ as esophageal intubation until proven otherwise, and default to removing the tube rather than listening your way out of a flat trace.
Why This Is Hard
Esophageal intubation happens to experienced people on “easy” looks. It shows up in more than 1 in 18 emergency intubations of the critically ill. Waveform capnography is how you exclude the esophagus. Fog, chest rise, and listening have high false-positive rates. Color-change detectors can lie after gastric CO₂. Teams then lock onto “it’s just arrest” or “it’s just bronchospasm” and leave a tube in the stomach. The slogan is still the street rule: no trace = wrong place.
- Waveform EtCO₂ (the CO₂ waveform on the monitor) on before the look. Confirm the monitor actually traces during preoxygenation.
- Say the view out loud. Say “sustained EtCO₂” or “flat trace” out loud. Your partner should agree or challenge.
- Sustained exhaled CO₂ means a real square-ish wave that rises on exhalation, holds or grows over several breaths, and is not a tiny blip from a soda.
- After every move, vomit, or packaging: glance at the waveform again. Tubes migrate.
Street Sequence
- Pass the tube. Watch the waveform, not the fog. Partner watches the screen.
- If there is no sustained exhaled CO₂, that is esophageal until you prove it is not. Default is pull the tube and ventilate with a mask or SGA (supraglottic airway).
- Do not spend the sat falling on “five-point auscultation.” Clinical exam does not exclude esophageal intubation.
- Cardiac arrest and severe bronchospasm are the two stories people tell themselves. High-quality CPR still makes CO₂ if the tube is in the trachea. A flat line is not “just arrest.”
Field Rules
- No trace = wrong place: the default response to no sustained exhaled CO₂ is remove the tube and ventilate.
- Sustained means a repeating wave, not one color change and a high-five. You want amplitude that rises on exhalation, is consistent over several breaths, and is clinically believable.
- Fog and breath sounds lie: misting false-positive rate was about 0.69 in a major review. Bilateral sounds still miss the esophagus often enough to kill.
- Reconfirm after movement: packaging, compressions, and kids displace tubes. A good trace at the curb can be a flat line in the truck.
- If you will not pull it: you must actively exclude the esophagus (repeat look, preferably video) while the sat is still okay. If the sat falls, the tube comes out.
- Sustained EtCO₂ — or pull it
- No trace = wrong place
- Fog is not confirmation
- Reconfirm after we move them
Field Pitfalls
- Calling a flat capnograph “bronchospasm” without pulling the tube.
- Trusting “I saw it pass the cords” in a brown, bouncing field.
- Using a color-change gadget once and never looking again.
- Leaving a tube in because taking it out feels like failure.
Practice
60-second drill
Partner: you passed a tube, chest “rises,” sat was 99% from preox, capnograph is flat. First sentence. Then they arrest. What is still the first problem?
Related: Waveform Capnography: The Gold Standard, Post-Intubation Care, Video Laryngoscopy in the Field.
Sources & Further Study
Named guidelines for further study. They are not clinical orders and do not replace your protocol or medical direction.
- NASEMSO National Model EMS Clinical Guidelines (2022) — U.S. EMS model language; protocol still wins
- PUMA 2022 — Preventing unrecognised oesophageal intubation — waveform is the mainstay; default is remove the tube; clinical exam does not exclude
- LITFL — Unrecognised oesophageal intubation — plain-language PUMA summary: no trace = wrong place
- INTUBE (JAMA 2021) — esophageal intubation is common in emergency airways of the critically ill
Education only. Apply learning within your protocols and medical direction. This is not clinical care guidance.
Check Your Understanding
Street decisions from this lesson only. After you check, the key is highlighted. Education practice — not a certification exam.