A sudden drop in end-tidal CO2 during ventilation most often indicates which event?

• A. Disconnection or tube dislodgement
• B. Left ventricular failure
• C. Pulmonary embolism
• D. Massive pleural effusion

Answer: (A)

A sudden drop in end-tidal CO2 during ventilation points to a rapid loss of gas delivery to the lungs. End-tidal CO2 reflects the CO2 that is being exhaled with each breath; if the circuit is broken or the endotracheal tube becomes dislodged, CO2 can no longer reach the sensor, causing the reading to fall abruptly to near zero and the waveform to disappear. That immediate, dramatic change is most characteristic of a disconnection or tube dislodgement.

Other conditions can alter CO2, but they don’t typically produce such an abrupt, complete loss of CO2 in the moment the problem occurs. For example, massive cardiopulmonary issues like left ventricular failure or pulmonary embolism, or a large pleural effusion, affect CO2 through changes in perfusion or ventilation over time rather than causing an instantaneous circuit failure.