Concentration Effect — FRCA Primary MCQ
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Correct answer: D — The faster rate of rise of FA/FI when a higher inspired concentration of an agent is used
The concentration effect states that a higher inspired concentration of an inhaled agent results in a faster rate of rise of FA/FI. At higher inspired concentrations the volume of gas taken up from the alveolus is proportionately replaced by a larger volume of fresh gas (concentrating effect and augmented inflow). This is most clinically significant with N2O at 60-70%.
Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care