A sudden increase in PetCO2 during CPR most likely indicates:

• A. ROSC
• B. Air embolism
• C. Ventilator failure
• D. Cardiac tamponade

Answer: (A)

PetCO2 during CPR reflects how much blood is reaching the lungs and being brought back to the heart to be circulated—i.e., pulmonary blood flow and overall cardiac output. While chest compressions are ongoing, this end-tidal value is typically low because perfusion is limited. A sudden rise in PetCO2 indicates a rapid improvement in perfusion, most plausibly because the heart has started beating effectively again (return of spontaneous circulation). With ROSC, more CO2-laden blood is delivered to the lungs each cycle, so the amount exhaled at the end of expiration jumps quickly. This abrupt change is a strong clue that circulation has resumed.

Other scenarios don’t fit a sudden spike as reliably: air embolism wouldn’t inherently produce a quick, sustained rise in PetCO2 during CPR; ventilator failure usually reduces ventilation and may lower PetCO2 rather than cause a sharp increase; cardiac tamponade keeps cardiac output suppressed and would keep PetCO2 low. After seeing a sharp PetCO2 rise, you should promptly confirm ROSC with additional clinical assessment and monitoring.