What does a sudden loss of end-tidal CO2 indicate during anesthesia, and what is the immediate course of action?

• A. Apnea, dislodged circuit, or obstructed airway; requires immediate assessment
• B. Improved ventilation
• C. Hypertension
• D. Excessive ventilation

Answer: (A)

A sudden loss of end-tidal CO2 means there is an abrupt cessation of effective ventilation—the CO2 that was being exhaled is no longer reaching the sensor. The most likely reasons are apnea, a dislodged or disconnected airway/circuit, or an airway obstruction. Because capnography reflects ongoing gas exchange, any real-time disappearance of the CO2 waveform signals an urgent problem with ventilation that must be addressed immediately.

The immediate course of action is to rapidly assess and restore ventilation. First, verify the airway and circuit: check that the endotracheal tube or airway device is still in place and patent, inspect the circuit for disconnection, leaks, or kinks, and confirm the ventilator is delivering breaths. If needed, switch to manual ventilation with 100% oxygen while you fix the issue. Clear any airway obstruction and re-seal or reconnect the circuit as required. Reassess with capnography and ensure a waveform returns along with adequate chest movement and oxygenation.

The other possibilities—improved ventilation, hypertension, or excessive ventilation—do not produce a sudden, complete loss of the CO2 signal, so they do not fit the scenario as the immediate cause.