Arrange Mapelson circuit for spontaneous ventilation in an adult from best to worst
During spontaneous ventilation, alveolar gas containing Co2 will be exhaled into the breathing tube or directly vented through an open APL valve. Before inhalation occurs, if the fresh gas flow exceeds alveolar minute ventilation, the in flow of fresh gas will force the alveolar gas remaining in the breathing tube to exit from the APL valve. Because a fresh gas flow equal to minute ventilation is sufficient to prevent rebreathing, the Mapelson a design is the most efficient for spontaneous ventilation
D>B>C>A
A>C>B>D
A>D>C>B
B>C>D>A
Anesthesia Circuit