The most appropriate circuit for ventilating a spontaneously breathing infant during anaesthesia is:
The most appropriate circuit advocated for use in infants is the Ayre's T piece (Mapleson E). Ref: Lee's Synopsis of Anaesthesia, 12th Edition, Page 117; Sho Textbook of Anaesthesia By Ajay Yadav, 2nd Edition, Page 27
Jackson Rees' modification of Ayre's T Piece
Mapleson A or Magill's circuit
Mapleson C or Waters' to and fro canister
Bains circuit