Obstructive sleep apnea is caused by what?

• A. Caused by pneumonia
• B. Caused by CNS failure
• C. Caused by low oxygen saturations
• D. Caused by anatomic obstruction of the upper airway with continued ventilatory effort

Answer: (D)

Upper airway obstruction that occurs during sleep with ongoing breathing effort. The muscles relax and the airway narrows or collapses, so airflow is blocked even though the person continues to attempt to breathe. This creates repeated apneas or hypopneas, leading to drops in oxygen saturation and brief arousals that restore the airway. This distinguishes it from central sleep apnea, where the brain stops sending the signal to breathe and there is little or no respiratory effort during the event. Pneumonia would cause hypoxemia through lung infection, not by blocking the airway during sleep, and low oxygen saturations are a consequence of the obstruction, not the cause. The hallmark mechanism is the anatomic/functional upper airway obstruction with continued ventilatory effort.