Central apnea can best be defined as a cessation of which of the following?

• A. Respiratory airflow
• B. Respiratory effort
• C. Respiratory volume
• D. Oxygen saturation

Answer: (B)

Central apnea is defined by a cessation of neural drive to the respiratory muscles, so there is no respiratory effort—no chest movement and, consequently, no airflow. This lack of respiratory effort is the hallmark differentiating it from obstructive apnea, where effort continues but airflow is blocked by an airway obstruction. Oxygen saturation may fall during an apnea episode, but the defining feature is the absence of respiratory effort.