Shivering — FRCA Primary MCQ
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Correct answer: C — High oxygen consumption and low FRC shorten safe apnoea time
Shivering increases skeletal muscle metabolic heat production. Hypocapnia causes cerebral vasoconstriction is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Acidosis shifts the oxyhaemoglobin curve right is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Ventilation of poorly perfused alveoli increases dead space is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. ADH inserts aquaporin-2 channels in collecting ducts 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