The Shape of the Expired CO₂ tracing of a Patient

Multiple Choice

The shape of the expired CO₂ tracing of a patient is normal but instead of being zero, the baseline is elevated to about 12 mm Hg. Which of the following is the most likely problem?

A) patient disconnected from the system
B) obstruction of the sampling tube
C) rebreathing
D) presence of N₂O