What is the gold standard for assessing ventilation?

• A. EtCO2
• B. Arterial blood gas analysis
• C. Spirometry
• D. Pulse oximetry

Answer: (A)

End-tidal CO2 measurement with capnography provides the best real-time picture of ventilation because it directly tracks the amount of CO2 being eliminated from the lungs on each breath. This makes it highly sensitive to changes in ventilatory status, so you can rapidly detect hypoventilation, apnea, airway obstruction, or a disconnection in the breathing circuit. It’s noninvasive and continuous, giving immediate feedback during anesthesia or critical care. In contrast, arterial blood gas analysis measures PaCO2 directly but requires a blood sample and only reflects a single time point, not ongoing ventilation. Spirometry looks at lung volumes and flow but doesn’t tell you how well CO2 is being removed in real time, and pulse oximetry assesses oxygenation, not ventilation. For these reasons, end-tidal CO2 is the preferred tool for monitoring ventilation.