A patient with Cheyne-Stokes respiration has hypocapnic episodes followed by apnoea. Which mechanism accounts for the oscillating breathing pattern?

• A Increased circulatory delay from cardiac failure causing controller gain instability — hyperventilation causes hypocapnia, triggering apnoea until CO2 rises again ✓
• B Intermittent upper airway obstruction from pharyngeal muscle fatigue during sleep
• C Increased chemoreceptor sensitivity causing breath-by-breath feedback oscillation
• D Pontine respiratory group dysfunction with alternating activation and inhibition cycles

Explanation

Cheyne-Stokes respiration is a form of periodic breathing seen in heart failure, strokes, and altitude. The key mechanism is increased circulatory delay (cardiac output is low, so the time for blood from the lungs to reach the central chemoreceptors is prolonged) combined with high loop gain. Hyperventilation lowers PaCO2 below the apnoeic threshold, causing apnoea. During apnoea, CO2 rises (slowly, because of the long circulatory delay), eventually triggering hyperventilation again. The cycle repeats. High ventilatory sensitivity (controller gain) amplifies the instability. Obstructive sleep apnoea involves pharyngeal obstruction and is distinct from this central mechanism.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.