Continuous quantitative waveform capnography provides a measure of what and why?

Continuous quantitative waveform capnography provides a measure of what and why?

• A. Blood pressure, because CO2 affects vessel tone
• B. Cardiac output during chest compressions, because CO2 exhaled relates to blood flow
• C. Oxygen saturation, because CO2 reflects oxygen exchange
• D. Heart rate, because CO2 relates to metabolic rate

Answer: (B)

Continuous waveform capnography measures end-tidal CO2, which during CPR reflects how well blood is flowing to the lungs and, consequently, the overall forward cardiac output produced by chest compressions. CO2 is carried in the blood from the tissues to the lungs, so the amount exhaled depends on pulmonary blood flow. When chest compressions generate good perfusion, more CO2 reaches the lungs and ETCO2 rises; when perfusion is poor, ETCO2 falls. This makes ETCO2 a real-time indicator of how effectively the heart is delivering blood during compressions and can signal impending return of spontaneous circulation. The other options don’t fit: blood pressure isn’t directly measured by capnography, so ETCO2 doesn’t provide BP. Oxygen saturation reflects oxygenation, not CO2 elimination, so it’s not what capnography measures. Heart rate isn’t directly measured by capnography, which tracks CO2 in exhaled air rather than pulse rate.

Continuous waveform capnography measures end-tidal CO2, which during CPR reflects how well blood is flowing to the lungs and, consequently, the overall forward cardiac output produced by chest compressions. CO2 is carried in the blood from the tissues to the lungs, so the amount exhaled depends on pulmonary blood flow. When chest compressions generate good perfusion, more CO2 reaches the lungs and ETCO2 rises; when perfusion is poor, ETCO2 falls. This makes ETCO2 a real-time indicator of how effectively the heart is delivering blood during compressions and can signal impending return of spontaneous circulation.

The other options don’t fit: blood pressure isn’t directly measured by capnography, so ETCO2 doesn’t provide BP. Oxygen saturation reflects oxygenation, not CO2 elimination, so it’s not what capnography measures. Heart rate isn’t directly measured by capnography, which tracks CO2 in exhaled air rather than pulse rate.