Central sleep apnea features: absence of respiratory effort during apnea episodes.

• A. Absence of respiratory effort during apnea episodes.
• B. Airway obstruction with ongoing respiratory effort.
• C. Increased frequency of leg movements during sleep.
• D. No nocturnal symptoms.

Answer: (A)

Central sleep apnea is defined by the absence of respiratory effort during apnea events. In other words, during an episode where airflow stops, the chest and diaphragm show no movement because the brain isn’t sending the signal to breathe. That lack of neural drive is the hallmark that distinguishes central from obstructive sleep apnea.

This contrasts with obstructive sleep apnea, where airflow stops but the body still attempts to breathe, so you see ongoing respiratory effort on monitoring even though the airway is blocked. The other options describe different phenomena—airway obstruction with continuing effort points to obstructive sleep apnea; increased leg movements refer to periodic limb movements during sleep; and having no nocturnal symptoms isn’t a defining feature of central sleep apnea.

So the statement that aligns best with central sleep apnea is the absence of respiratory effort during apnea episodes.