What is the fresh gas flow (FGF) for a circle circuit initially and after 5 minutes?

• A. 2-4 L/min initially then 1-2 L/min after 5 mins
• B. 1-2 L/min initially then 0.5-1 L/min
• C. 4-6 L/min initially then 2-3 L/min
• D. 0.5-1 L/min initially then 0.25-0.5 L/min

Answer: (A)

Fresh gas flow management in a circle system aims to wash in the circuit quickly and then conserve gas during maintenance. At induction you use a moderate-high flow (about 2–4 L/min) to rapidly achieve the desired inspired concentrations and to charge the circuit, reducing rebreathing as the patient begins to breathe. After roughly five minutes, the circuit is filled and stable, so you can drop the flow to about 1–2 L/min to save oxygen and anesthetic gas without compromising ventilation or the delivered anesthetic concentration. This pattern fits the option describing 2–4 L/min initially, then 1–2 L/min after five minutes. The other options either underestimate the wash-in flow or keep a higher flow longer than necessary, which is not typically ideal for standard practice.