Capnometry involves:

• A. The use of a capnometer, a device that measures the amount of expired carbon dioxide
• B. The measurement of blood oxygen saturation
• C. The calculation of alveolar ventilation
• D. The assessment of airway resistance

Answer: (A)

Capnometry is the measurement of carbon dioxide in exhaled breath using a capnometer. It provides a numerical end-tidal CO2 value, reflecting the CO2 concentration at the end of expiration and serving as a real-time guide to ventilation and airway status. This is the best choice because the capnometer is specifically designed to quantify expired CO2, which helps confirm that ventilation is occurring and that the airway device is in place when intubating (a clear CO2 signal indicates tracheal placement). By contrast, measuring blood oxygen saturation is done with a pulse oximeter, not capnometry. Calculating alveolar ventilation is a broader concept involving tidal volume and respiratory rate and is not a direct measurement provided by capnometry. Assessing airway resistance involves other measurements of flow and pressure and is not what capnometry measures. Capnometry focuses on the CO2 content of exhaled air to monitor ventilation.