After a difficult intubation, there is no observed end-tidal CO2. Which of the following is NOT a likely cause?

After a difficult intubation, there is no observed end-tidal CO2. Which of the following is NOT a likely cause?

• A. Esophageal intubation
• B. Failure to ventilate
• C. Disconnection of circuit or monitor
• D. Pneumothorax requiring high airway pressures

Answer: (D)

End-tidal CO2 appears only when alveolar gas containing CO2 is being delivered to the lungs and exhaled through the circuit. If you see no ETCO2 after a difficult intubation, think about situations where there is no effective ventilation or the gas never reaches the sensor. Esophageal intubation places the tube in the esophagus, so the lungs aren’t ventilated and CO2 isn’t exhaled, giving an absent CO2 waveform. Likewise, failing to ventilate means there’s little or no CO2 being delivered to the alveoli, so ETCO2 is not seen. A disconnection of the circuit or monitor abruptly stops gas flow to the sensor, also producing no ETCO2. Pneumothorax that requires high airway pressures can severely impair ventilation and reduce the amount of CO2 reaching the lungs, and it can lower ETCO2 levels, but it does not typically produce a complete absence of the CO2 waveform. In other words, it’s unlikely to be the cause of no observed ETCO2, compared with the others where CO2 delivery to the lungs is clearly interrupted.

End-tidal CO2 appears only when alveolar gas containing CO2 is being delivered to the lungs and exhaled through the circuit. If you see no ETCO2 after a difficult intubation, think about situations where there is no effective ventilation or the gas never reaches the sensor. Esophageal intubation places the tube in the esophagus, so the lungs aren’t ventilated and CO2 isn’t exhaled, giving an absent CO2 waveform. Likewise, failing to ventilate means there’s little or no CO2 being delivered to the alveoli, so ETCO2 is not seen. A disconnection of the circuit or monitor abruptly stops gas flow to the sensor, also producing no ETCO2.

Pneumothorax that requires high airway pressures can severely impair ventilation and reduce the amount of CO2 reaching the lungs, and it can lower ETCO2 levels, but it does not typically produce a complete absence of the CO2 waveform. In other words, it’s unlikely to be the cause of no observed ETCO2, compared with the others where CO2 delivery to the lungs is clearly interrupted.