Wash-In Curve Factors — FRCA Primary MCQ

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ModeratePharmacology - Inhalational AgentsWash-In Curve FactorsFRCA Primary

Regarding the wash-in curve (FA/FI) for volatile agents which factor causes the curve to rise most steeply?

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Correct answer: C — Low blood:gas solubility with high inspired concentration

Rapid FA/FI rise (fast induction) is favoured by: low blood:gas solubility (less uptake from alveoli) / high inspired concentration (concentration effect) / high alveolar ventilation (faster delivery to alveoli) / low cardiac output (less removal from alveoli). Desflurane and N2O have the fastest wash-in due to low solubility.

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