4 Table 1.2: Classification of respiratory anesthesia system according to Baker [20] Types of anesthesia flows Fresh gas flow compensated Basic metabolic flow ~ 250 ml / min Minimum flow 250 - 500 ml / min Low flow 500 - 1000 ml / min Medium flow 1 - 2 L / min High flow 2 - 4 L / min Open flow > 4 L / min Closed-loop system: The closed-loop system is transformed from a semi-closed system by closing the pressure reducing valve on the exhaled airway.