After ROSC, ETCO2 trend is:

• A. Abrupt and sustained increase
• B. A sudden rise and then stabilization
• C. No change
• D. A gradual decline

Answer: (B)

ETCO2 reflects how much carbon dioxide is being produced by the body and carried to the lungs by the bloodstream, then exhaled. When spontaneous circulation returns, the heart suddenly restores blood flow,迅 delivering CO2 from the tissues to the lungs. That jump in perfusion makes the amount of CO2 exiting the lungs rise quickly, so you see an abrupt increase in ETCO2. After this quick change, the level settles into a stable value that matches the current ventilation and metabolic CO2 production, rather than continuing to rise.

This pattern doesn’t fit with no change, because circulation restoration changes CO2 delivery. It also doesn’t fit with a gradual decline, since the immediate effect of improved perfusion is increased CO2 delivery to the lungs, not a slow fall. And it isn’t an abrupt and sustained rise, because once ventilation and perfusion balance out, the ETCO2 stabilizes rather than continuing to climb.