ACLS Basics and STEMIs Practice Test

During CPR, continuous capnography tracks end-tidal carbon dioxide, which serves as an indirect read on how well chest compressions are generating pulmonary blood flow and thus cardiac output. The amount of CO2 reaching the lungs depends on how effectively blood is circulating; when compressions are more effective, more CO2 is delivered to the lungs and exhaled, raising the end-tidal CO2. This makes EtCO2 a practical indicator of CPR quality and the likelihood of return of spontaneous circulation, rather than a direct measure of oxygen content, heart rate, or respiratory rate. A sudden rise in EtCO2 can also signal ROSC.