An absent capnography waveform is most consistent with which finding?

An absent capnography waveform is most consistent with which finding?

• A. Airway obstruction
• B. Normal ventilation
• C. Hyperventilation
• D. High oxygen delivery

Answer: (A)

Capnography depends on detecting CO2 in exhaled gas. If no waveform appears, it means no CO2 is reaching the sensor, signaling that ventilation is effectively stopped or blocked. The best match among the options is airway obstruction because a blockage can prevent exhaled gas from flowing to the sampling line, so there is no CO2 detected and the waveform disappears. In contrast, normal ventilation would produce a normal capnography waveform; hyperventilation lowers the amount of CO2 but still yields a visible waveform; and high oxygen delivery, with the patient still ventilating, does not by itself abolish the waveform. Clinically, an absent waveform should prompt immediate assessment of airway patency and the ventilation circuit for obstruction or disconnection.

Capnography depends on detecting CO2 in exhaled gas. If no waveform appears, it means no CO2 is reaching the sensor, signaling that ventilation is effectively stopped or blocked. The best match among the options is airway obstruction because a blockage can prevent exhaled gas from flowing to the sampling line, so there is no CO2 detected and the waveform disappears.

In contrast, normal ventilation would produce a normal capnography waveform; hyperventilation lowers the amount of CO2 but still yields a visible waveform; and high oxygen delivery, with the patient still ventilating, does not by itself abolish the waveform. Clinically, an absent waveform should prompt immediate assessment of airway patency and the ventilation circuit for obstruction or disconnection.