A 68-year-old man with chronic heart failure has a resting heart rate of 88 bpm and develops Cheyne-Stokes respiration during sleep. The cyclical breathing pattern is primarily due to:
- A Periodic upper airway obstruction by the tongue
- B Hypoxic depression of the respiratory centre
- C Increased lung-to-chemoreceptor circulation time causing oscillating hypercapnic drives ✓
- D Abnormal Hering-Breuer reflex causing breath cessation
Correct answer: C. Increased lung-to-chemoreceptor circulation time causing oscillating hypercapnic drives
Explanation
In low cardiac output states, the circulation time between lungs and peripheral/central chemoreceptors is prolonged. The respiratory system overcorrects PaCO2 (causing hypocapnia and apnoea), then allows PaCO2 to rise again before the chemoreceptors detect the change, creating the crescendo-decrescendo cyclical pattern of Cheyne-Stokes respiration. This is distinct from obstructive sleep apnoea, in which upper airway collapse — not circulation time — is the primary mechanism.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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