Volatile CO2 Response Reduction — FRCA Primary MCQ

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ModeratePharmacology - Inhalational AgentsVolatile CO2 Response ReductionFRCA Primary

Volatile anaesthetic agents reduce the gain (slope) of the ventilatory response to CO2 and shift the curve to the right. At 1 MAC the response is:

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Correct answer: A — Reduced by approximately 50%

Volatile agents reduce the ventilatory response to CO2 in a dose-dependent manner. At 1 MAC the slope is reduced by approximately 50% and shifted rightward (higher PaCO2 threshold). At 1.5-2 MAC the response is nearly abolished. This is why spontaneously breathing patients under volatile anaesthesia develop hypercapnia.

Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care