During CPR, what is the normal end-tidal CO2 (EtCO2) range?

• A. 5-10
• B. 15-20
• C. 20-25
• D. 10-15

Answer: (D)

End-tidal CO2 during CPR reflects the amount of blood flowing through the lungs and the effectiveness of chest compressions. Because cardiac output is limited in CPR, EtCO2 is much lower than normal resting values, which are around 35–45 mm Hg. The typical range seen with adequate CPR is about 10–15 mm Hg. This level indicates there is some pulmonary blood flow and CO2 delivery to the alveoli despite ongoing compressions.

If EtCO2 stays well below this range (lower end around 5–10), it suggests suboptimal chest compressions or ventilation issues that reduce perfusion to the lungs. Values edging higher toward the mid-teens or above can point to improving perfusion and the possibility of ROSC, with a dramatic jump to very high values (often >35–40) signaling that return of spontaneous circulation has occurred.