What is the role of capnography in anesthesia monitoring?

• A. To measure blood oxygen saturation.
• B. To monitor ventilation and detect hypoventilation, airway obstruction, or apnea by measuring end-tidal CO2.
• C. To monitor heart rate.
• D. To assess body temperature.

Answer: (B)

Capnography provides real-time feedback on ventilation by measuring end-tidal CO2 in the exhaled breath. This end-tidal CO2 reflects how effectively CO2 is being eliminated from the lungs, so it directly informs us about the patient’s ventilatory status during anesthesia.

Because of this, it’s the best tool for quickly detecting problems like hypoventilation, airway obstruction, or apnea. If ventilation is inadequate, the end-tidal CO2 value changes in a characteristic way and the capnogram waveform alters accordingly. A normal waveform with an EtCO2 in the expected range indicates good ventilation. If ventilation worsens, EtCO2 may rise as CO2 accumulates, while an abrupt loss of the waveform signals apnea or a circuit/airway disconnection. Partial airway obstruction tends to distort the waveform and may produce a longer rise and a distorted plateau (sometimes described as a shark-fin pattern). These waveform trends allow rapid intervention to restore ventilation, clear obstructions, or reestablish airway patency.

Capnography is also valuable for confirming tracheal intubation because a consistent CO2 signal indicates proper placement in the trachea rather than the esophagus. While it complements pulse oximetry, capnography offers earlier warning of ventilation problems, since oxygen saturation can lag behind changes in ventilation.