Capnography is the measurement of the partial pressure of CO2 in the exhaled breath over time. The maximum CO2 concentration at the end of each tidal breath (end-tidal, ET CO2) can provide information about ventilation and perfusion in patients in cardiac arrest undergoing cardiopulmonary resuscitation (CPR).
The increase in cardiac output with the return of spontaneous circulation (ROSC) causes rapid transport of CO2 accumulated in tissues during cardiac arrest to the lungs. This is detected as a sudden rise in EtCO2 on capnography and is the earliest indicator of ROSC, occurring even before a pulse can be palpated. This technology virtually eliminates the need to stop CPR to check for a palpable pulse, reducing interruptions in cardiac compressions.
In addition, recent studies have indicated that EtCO2 can help determine prognosis during cardiac arrest. Patients with an EtCO2 of ≤10 mm Hg after 20 minutes of CPR are highly unlikely to achieve ROSC.