Lobar collapse shunt — FRCA Primary MCQ

Correct answer: E — Perfusion of non-ventilated alveoli creates shunt

True shunt is perfusion of non-ventilated lung and responds poorly to oxygen. Right ventricular afterload rises with pulmonary vascular resistance is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Chronic hypertension shifts cerebral autoregulation right is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Small myelinated fibres block relatively early is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Central chemoreceptors respond to CSF hydrogen ion concentration is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. In Primary FRCA physiology, the correct answer is usually the variable that best explains the observed change in the anaesthetised patient.

Reference: West's Respiratory Physiology; Ganong Review of Medical Physiology; Primary FRCA textbooks