If nasal flow decreases with an increase in respiratory effort, desaturation is caused by which apnea?

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Obstructive apnea is indicated when airflow (nasal flow) falls away while the chest and abdomen still show effort to breathe. That means the airway is blocked but the brain is signaling to breathe, so you have ongoing respiratory effort with little or no airflow, leading to desaturation.

In contrast, central apnea would show a loss of respiratory effort during the pause, so airflow would be absent without any effort. Hypoventilation isn’t an apnea event at all—it's reduced ventilation over time with continued effort and gradual desaturation, not a discrete airflow cessation. Mixed apnea would begin with a central (no effort) phase and then progress to an obstructive (effort with blocked airflow) phase, so it wouldn’t match the pattern of airflow stopping while effort remains constant from the outset.