The most appropriate circuit for ventilating a spontaneously breathing infant during anaesthesia is-

Ans. is 'a' i.e., Jackson Rees modification of Ayre's T piece o The Ayre's T piece with Jackson-Rees modification remains the mainstay of pediatric anesthesia.Circuit typeRequired fresh gas flowCommentsSpontaneousControlledType A (Magill circuit)Equal to minute volumeVery high and difficult to predicto Circuit of choice for spontaneous ventilation. (80 mLAg/min) o Should not be used for controlled ventilationType B2 x minute volume2 - 2 1/2 minute volume Type C (Water's to and fro)2 -3 x minute volume2 - 2 1/2 minute volumeo It is a coaxial systemType D (Bain circuit)2 - 3 x minute volume1 - 2 x minute volumeo Circuit to choice for controlledo Most commonly used circuit,o Can also be used for spontaneous ventilation.Type E (Ayre's T-piece)2-3 x minute volume3 x minute volumeo Circuit of 2nd choice in childrenType F (Jackson-Rees circuit)2-3 x minute volume2 x minute ventilationo Circuit of choice in childrenNote: - Coaxial system means both fresh gas tube and exhaled gas tube are placed in the same axis, i.e., coaxial. Fresh gases are delivered through the inner tube and exhaled gas is expired through ofter tube so that mixing of fresh gases and exhaled gases does not occur.