Reservoir bag allows for variation in volume with breathing and any mismatch between inflow and absorption. Bag can be used to manually force ventilation, or be replaced by bellows for force ventilation. If the anaesthetic in the circuit is in equilibrium with that in the patient, then no extra need be added. Quickly reducing the anaesthetic concentration requires flushing the system. Requires more monitoring of the system.
Partial recirculation vents some fraction of the expired gases.
Can add humidification system to reduce heat loss from evaporation. Gas scavenging systems. Need to collect gas from all possible escape points. Inspired oxygen concentration Airway pressure for both low and high pressures. Both concentration and as indicator of breathing.