Typical flowrates for popular breathing systems.

Suggested fresh gas flow rates for maintenance of anaesthesia.

Litres per min : O₂/N₂O Figures in "( )" = Total flow rate.

Breathing System:	Modified Ayres T	Mini-Lack	Bain	Magill	Lack	Cyclo-Flo Circle
Mapleson Classification	"F"	Mod. "A"	"D"	"A"	Mod."A"	N/A
Circuit Factor	2.5 x mV	1.0 x mV	2.5 x mV	1.5 x mV	1.0 x mV	N/A
2.5 kg	(3) 1.0/2.0	(1) 0.4/0.60	-	-	-	-
5.5 kg	(4.5) 1.5/3.0	(1.5) 0.5/1.0	-	-	-	-
7.5 kg	(6) 2.0/4.0	(2) 0.7/1.30	-	-	(2.5) 1.0/1.5	0.5
10 kg	(7.5) 2.5/5.0	(2.5) 0.9/1.60	(7.5) 2.5/5.0	(3) 1.0/2.0	(3) 1.0/2.0	0.5
15 kg			(9) 3.0/6.0	(4.5) 1.5/3.0	(4.5) 1.5/3.0	0.5
20 kg			(12) 4.0/8.0	(6) 2.0/4.0	(6) 2.0/4.0	0.5
25 kg				(7.5) 2.5/5.0	(7.5) 2.5/5.0	1.0
30 kg				(10.5) 3.5/7.0	(9) 3.0/6.0	1.0
35 kg				(12) 4.0/8.0	(10.5) 3.5/7.0	1.0
40 kg					(11) 4.0/7.0	1.5
45 kg					(12) 4.0/8.0	1.5
50 kg						1.5
55 kg						2.0
60 kg						2.0
70 kg						2.0
80 kg						2.5

Disclaimer: The above information is provided only as a useful guide. Users should make their own judgement as to the correct flow rate to be used for each patient, based on a thorough clinical assessment and the level of patient monitoring to be used.