What is the purpose of polysomnography's respiratory channels in diagnosing sleep apnea?

• A. To monitor leg movements
• B. To assess heart rhythm
• C. To detect apneas/hypopneas and distinguish central from obstructive events with oxygen desaturation
• D. To measure brain waves

Answer: (C)

The respiratory channels in polysomnography are used to track breathing in real time—airflow and the effort of breathing during sleep. This combination lets you see when breathing stops or becomes very shallow and whether the chest/abdominal muscles are still working. If airflow stops but there is still respiratory effort, the event is obstructive apnea. If there is no airflow and no respiratory effort, it’s a central apnea. The oxygen desaturation measured alongside these signals shows how much the blood’s oxygen level drops during the event, helping confirm that a breathing disturbance occurred and indicating its severity. This is why these channels are essential for identifying apneas and hypopneas and for distinguishing central from obstructive events, with desaturation data providing the physiologic impact. Other sensors (like EEG for brain waves, ECG for heart rhythm, or leg EMG for movements) serve different purposes and are not part of the respiratory-channel function.