Anesthesia breathing circuits

Anesthesia breathing circuits: Bi-Directional Flow Systems:

Mapleson did a theoretical analysis of the fresh gas requirements of the semiclosed systems available at that time. It is only proper to refer to it as Mapleson systems as he gave a nomenclature as A, B, C, D and E for easy identification as per their construction. For better understanding of the functional analyses, they have been classified as:

1. Afferent reservoir system (ARS).

2. Enclosed afferent reservoir systems (EARS).

3. Efferent reservoir systems (ERS).

4. Combined systems.

The afferent limb is that part of the breathing system which delivers the fresh gas from the machine to the patient. If the reservoir is placed in this limb as in Mapleson A, B, C and Lack’s systems, they are called afferent reservoir systems (ARS).

The efferent limb is that part of the breathing system which carries expired gas from the patient and vents it to the atmosphere through the expiratory valve/port. If the reservoir is placed in this limb as in Mapleson D, E, F and Bain systems, they are called efferent reservoir systems (ERS).

Enclosed afferent reservoir system (EARS) has been described by Miller and Miller.