Capnography during resuscitation is most useful for assessing chest compression effectiveness.

• A. Chest compression effectiveness
• B. Ventilation rate
• C. Blood pressure
• D. Heart rate

Answer: (A)

Capnography measures end-tidal CO2, which reflects how well blood is being circulated to the lungs and how effectively CO2 is being delivered to the lungs to be exhaled. In resuscitation, chest compressions are the mechanism that generates the forward flow of blood. When compressions are strong and consistent, more CO2 is carried to the lungs and expelled, so the end-tidal CO2 (ETCO2) rises. If compressions are shallow, erratic, or interrupted, perfusion drops and ETCO2 falls. That direct link between circulation during CPR and the CO2 that reaches and is exhaled from the lungs makes capnography the best tool for judging how effective chest compressions are.

Ventilation rate, blood pressure, and heart rate are important monitors, but capnography isn’t a direct measure of those. It mainly provides feedback on circulatory effectiveness via CO2 delivery and removal, with changes in ETCO2 also helping signal return of spontaneous circulation when a sudden rise occurs.